Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 9194 insertions, 0 deletions

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
new file mode 100644
index 0000000000..68d86dbecb
--- /dev/null
+++ b/drivers/md/raid5.c
@@ -0,0 +1,9194 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * raid5.c : Multiple Devices driver for Linux
+ *	   Copyright (C) 1996, 1997 Ingo Molnar, Miguel de Icaza, Gadi Oxman
+ *	   Copyright (C) 1999, 2000 Ingo Molnar
+ *	   Copyright (C) 2002, 2003 H. Peter Anvin
+ *
+ * RAID-4/5/6 management functions.
+ * Thanks to Penguin Computing for making the RAID-6 development possible
+ * by donating a test server!
+ */
+
+/*
+ * BITMAP UNPLUGGING:
+ *
+ * The sequencing for updating the bitmap reliably is a little
+ * subtle (and I got it wrong the first time) so it deserves some
+ * explanation.
+ *
+ * We group bitmap updates into batches.  Each batch has a number.
+ * We may write out several batches at once, but that isn't very important.
+ * conf->seq_write is the number of the last batch successfully written.
+ * conf->seq_flush is the number of the last batch that was closed to
+ *    new additions.
+ * When we discover that we will need to write to any block in a stripe
+ * (in add_stripe_bio) we update the in-memory bitmap and record in sh->bm_seq
+ * the number of the batch it will be in. This is seq_flush+1.
+ * When we are ready to do a write, if that batch hasn't been written yet,
+ *   we plug the array and queue the stripe for later.
+ * When an unplug happens, we increment bm_flush, thus closing the current
+ *   batch.
+ * When we notice that bm_flush > bm_write, we write out all pending updates
+ * to the bitmap, and advance bm_write to where bm_flush was.
+ * This may occasionally write a bit out twice, but is sure never to
+ * miss any bits.
+ */
+
+#include <linux/blkdev.h>
+#include <linux/delay.h>
+#include <linux/kthread.h>
+#include <linux/raid/pq.h>
+#include <linux/async_tx.h>
+#include <linux/module.h>
+#include <linux/async.h>
+#include <linux/seq_file.h>
+#include <linux/cpu.h>
+#include <linux/slab.h>
+#include <linux/ratelimit.h>
+#include <linux/nodemask.h>
+
+#include <trace/events/block.h>
+#include <linux/list_sort.h>
+
+#include "md.h"
+#include "raid5.h"
+#include "raid0.h"
+#include "md-bitmap.h"
+#include "raid5-log.h"
+
+#define UNSUPPORTED_MDDEV_FLAGS	(1L << MD_FAILFAST_SUPPORTED)
+
+#define cpu_to_group(cpu) cpu_to_node(cpu)
+#define ANY_GROUP NUMA_NO_NODE
+
+#define RAID5_MAX_REQ_STRIPES 256
+
+static bool devices_handle_discard_safely = false;
+module_param(devices_handle_discard_safely, bool, 0644);
+MODULE_PARM_DESC(devices_handle_discard_safely,
+		 "Set to Y if all devices in each array reliably return zeroes on reads from discarded regions");
+static struct workqueue_struct *raid5_wq;
+
+static inline struct hlist_head *stripe_hash(struct r5conf *conf, sector_t sect)
+{
+	int hash = (sect >> RAID5_STRIPE_SHIFT(conf)) & HASH_MASK;
+	return &conf->stripe_hashtbl[hash];
+}
+
+static inline int stripe_hash_locks_hash(struct r5conf *conf, sector_t sect)
+{
+	return (sect >> RAID5_STRIPE_SHIFT(conf)) & STRIPE_HASH_LOCKS_MASK;
+}
+
+static inline void lock_device_hash_lock(struct r5conf *conf, int hash)
+	__acquires(&conf->device_lock)
+{
+	spin_lock_irq(conf->hash_locks + hash);
+	spin_lock(&conf->device_lock);
+}
+
+static inline void unlock_device_hash_lock(struct r5conf *conf, int hash)
+	__releases(&conf->device_lock)
+{
+	spin_unlock(&conf->device_lock);
+	spin_unlock_irq(conf->hash_locks + hash);
+}
+
+static inline void lock_all_device_hash_locks_irq(struct r5conf *conf)
+	__acquires(&conf->device_lock)
+{
+	int i;
+	spin_lock_irq(conf->hash_locks);
+	for (i = 1; i < NR_STRIPE_HASH_LOCKS; i++)
+		spin_lock_nest_lock(conf->hash_locks + i, conf->hash_locks);
+	spin_lock(&conf->device_lock);
+}
+
+static inline void unlock_all_device_hash_locks_irq(struct r5conf *conf)
+	__releases(&conf->device_lock)
+{
+	int i;
+	spin_unlock(&conf->device_lock);
+	for (i = NR_STRIPE_HASH_LOCKS - 1; i; i--)
+		spin_unlock(conf->hash_locks + i);
+	spin_unlock_irq(conf->hash_locks);
+}
+
+/* Find first data disk in a raid6 stripe */
+static inline int raid6_d0(struct stripe_head *sh)
+{
+	if (sh->ddf_layout)
+		/* ddf always start from first device */
+		return 0;
+	/* md starts just after Q block */
+	if (sh->qd_idx == sh->disks - 1)
+		return 0;
+	else
+		return sh->qd_idx + 1;
+}
+static inline int raid6_next_disk(int disk, int raid_disks)
+{
+	disk++;
+	return (disk < raid_disks) ? disk : 0;
+}
+
+/* When walking through the disks in a raid5, starting at raid6_d0,
+ * We need to map each disk to a 'slot', where the data disks are slot
+ * 0 .. raid_disks-3, the parity disk is raid_disks-2 and the Q disk
+ * is raid_disks-1.  This help does that mapping.
+ */
+static int raid6_idx_to_slot(int idx, struct stripe_head *sh,
+			     int *count, int syndrome_disks)
+{
+	int slot = *count;
+
+	if (sh->ddf_layout)
+		(*count)++;
+	if (idx == sh->pd_idx)
+		return syndrome_disks;
+	if (idx == sh->qd_idx)
+		return syndrome_disks + 1;
+	if (!sh->ddf_layout)
+		(*count)++;
+	return slot;
+}
+
+static void print_raid5_conf (struct r5conf *conf);
+
+static int stripe_operations_active(struct stripe_head *sh)
+{
+	return sh->check_state || sh->reconstruct_state ||
+	       test_bit(STRIPE_BIOFILL_RUN, &sh->state) ||
+	       test_bit(STRIPE_COMPUTE_RUN, &sh->state);
+}
+
+static bool stripe_is_lowprio(struct stripe_head *sh)
+{
+	return (test_bit(STRIPE_R5C_FULL_STRIPE, &sh->state) ||
+		test_bit(STRIPE_R5C_PARTIAL_STRIPE, &sh->state)) &&
+	       !test_bit(STRIPE_R5C_CACHING, &sh->state);
+}
+
+static void raid5_wakeup_stripe_thread(struct stripe_head *sh)
+	__must_hold(&sh->raid_conf->device_lock)
+{
+	struct r5conf *conf = sh->raid_conf;
+	struct r5worker_group *group;
+	int thread_cnt;
+	int i, cpu = sh->cpu;
+
+	if (!cpu_online(cpu)) {
+		cpu = cpumask_any(cpu_online_mask);
+		sh->cpu = cpu;
+	}
+
+	if (list_empty(&sh->lru)) {
+		struct r5worker_group *group;
+		group = conf->worker_groups + cpu_to_group(cpu);
+		if (stripe_is_lowprio(sh))
+			list_add_tail(&sh->lru, &group->loprio_list);
+		else
+			list_add_tail(&sh->lru, &group->handle_list);
+		group->stripes_cnt++;
+		sh->group = group;
+	}
+
+	if (conf->worker_cnt_per_group == 0) {
+		md_wakeup_thread(conf->mddev->thread);
+		return;
+	}
+
+	group = conf->worker_groups + cpu_to_group(sh->cpu);
+
+	group->workers[0].working = true;
+	/* at least one worker should run to avoid race */
+	queue_work_on(sh->cpu, raid5_wq, &group->workers[0].work);
+
+	thread_cnt = group->stripes_cnt / MAX_STRIPE_BATCH - 1;
+	/* wakeup more workers */
+	for (i = 1; i < conf->worker_cnt_per_group && thread_cnt > 0; i++) {
+		if (group->workers[i].working == false) {
+			group->workers[i].working = true;
+			queue_work_on(sh->cpu, raid5_wq,
+				      &group->workers[i].work);
+			thread_cnt--;
+		}
+	}
+}
+
+static void do_release_stripe(struct r5conf *conf, struct stripe_head *sh,
+			      struct list_head *temp_inactive_list)
+	__must_hold(&conf->device_lock)
+{
+	int i;
+	int injournal = 0;	/* number of date pages with R5_InJournal */
+
+	BUG_ON(!list_empty(&sh->lru));
+	BUG_ON(atomic_read(&conf->active_stripes)==0);
+
+	if (r5c_is_writeback(conf->log))
+		for (i = sh->disks; i--; )
+			if (test_bit(R5_InJournal, &sh->dev[i].flags))
+				injournal++;
+	/*
+	 * In the following cases, the stripe cannot be released to cached
+	 * lists. Therefore, we make the stripe write out and set
+	 * STRIPE_HANDLE:
+	 *   1. when quiesce in r5c write back;
+	 *   2. when resync is requested fot the stripe.
+	 */
+	if (test_bit(STRIPE_SYNC_REQUESTED, &sh->state) ||
+	    (conf->quiesce && r5c_is_writeback(conf->log) &&
+	     !test_bit(STRIPE_HANDLE, &sh->state) && injournal != 0)) {
+		if (test_bit(STRIPE_R5C_CACHING, &sh->state))
+			r5c_make_stripe_write_out(sh);
+		set_bit(STRIPE_HANDLE, &sh->state);
+	}
+
+	if (test_bit(STRIPE_HANDLE, &sh->state)) {
+		if (test_bit(STRIPE_DELAYED, &sh->state) &&
+		    !test_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
+			list_add_tail(&sh->lru, &conf->delayed_list);
+		else if (test_bit(STRIPE_BIT_DELAY, &sh->state) &&
+			   sh->bm_seq - conf->seq_write > 0)
+			list_add_tail(&sh->lru, &conf->bitmap_list);
+		else {
+			clear_bit(STRIPE_DELAYED, &sh->state);
+			clear_bit(STRIPE_BIT_DELAY, &sh->state);
+			if (conf->worker_cnt_per_group == 0) {
+				if (stripe_is_lowprio(sh))
+					list_add_tail(&sh->lru,
+							&conf->loprio_list);
+				else
+					list_add_tail(&sh->lru,
+							&conf->handle_list);
+			} else {
+				raid5_wakeup_stripe_thread(sh);
+				return;
+			}
+		}
+		md_wakeup_thread(conf->mddev->thread);
+	} else {
+		BUG_ON(stripe_operations_active(sh));
+		if (test_and_clear_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
+			if (atomic_dec_return(&conf->preread_active_stripes)
+			    < IO_THRESHOLD)
+				md_wakeup_thread(conf->mddev->thread);
+		atomic_dec(&conf->active_stripes);
+		if (!test_bit(STRIPE_EXPANDING, &sh->state)) {
+			if (!r5c_is_writeback(conf->log))
+				list_add_tail(&sh->lru, temp_inactive_list);
+			else {
+				WARN_ON(test_bit(R5_InJournal, &sh->dev[sh->pd_idx].flags));
+				if (injournal == 0)
+					list_add_tail(&sh->lru, temp_inactive_list);
+				else if (injournal == conf->raid_disks - conf->max_degraded) {
+					/* full stripe */
+					if (!test_and_set_bit(STRIPE_R5C_FULL_STRIPE, &sh->state))
+						atomic_inc(&conf->r5c_cached_full_stripes);
+					if (test_and_clear_bit(STRIPE_R5C_PARTIAL_STRIPE, &sh->state))
+						atomic_dec(&conf->r5c_cached_partial_stripes);
+					list_add_tail(&sh->lru, &conf->r5c_full_stripe_list);
+					r5c_check_cached_full_stripe(conf);
+				} else
+					/*
+					 * STRIPE_R5C_PARTIAL_STRIPE is set in
+					 * r5c_try_caching_write(). No need to
+					 * set it again.
+					 */
+					list_add_tail(&sh->lru, &conf->r5c_partial_stripe_list);
+			}
+		}
+	}
+}
+
+static void __release_stripe(struct r5conf *conf, struct stripe_head *sh,
+			     struct list_head *temp_inactive_list)
+	__must_hold(&conf->device_lock)
+{
+	if (atomic_dec_and_test(&sh->count))
+		do_release_stripe(conf, sh, temp_inactive_list);
+}
+
+/*
+ * @hash could be NR_STRIPE_HASH_LOCKS, then we have a list of inactive_list
+ *
+ * Be careful: Only one task can add/delete stripes from temp_inactive_list at
+ * given time. Adding stripes only takes device lock, while deleting stripes
+ * only takes hash lock.
+ */
+static void release_inactive_stripe_list(struct r5conf *conf,
+					 struct list_head *temp_inactive_list,
+					 int hash)
+{
+	int size;
+	bool do_wakeup = false;
+	unsigned long flags;
+
+	if (hash == NR_STRIPE_HASH_LOCKS) {
+		size = NR_STRIPE_HASH_LOCKS;
+		hash = NR_STRIPE_HASH_LOCKS - 1;
+	} else
+		size = 1;
+	while (size) {
+		struct list_head *list = &temp_inactive_list[size - 1];
+
+		/*
+		 * We don't hold any lock here yet, raid5_get_active_stripe() might
+		 * remove stripes from the list
+		 */
+		if (!list_empty_careful(list)) {
+			spin_lock_irqsave(conf->hash_locks + hash, flags);
+			if (list_empty(conf->inactive_list + hash) &&
+			    !list_empty(list))
+				atomic_dec(&conf->empty_inactive_list_nr);
+			list_splice_tail_init(list, conf->inactive_list + hash);
+			do_wakeup = true;
+			spin_unlock_irqrestore(conf->hash_locks + hash, flags);
+		}
+		size--;
+		hash--;
+	}
+
+	if (do_wakeup) {
+		wake_up(&conf->wait_for_stripe);
+		if (atomic_read(&conf->active_stripes) == 0)
+			wake_up(&conf->wait_for_quiescent);
+		if (conf->retry_read_aligned)
+			md_wakeup_thread(conf->mddev->thread);
+	}
+}
+
+static int release_stripe_list(struct r5conf *conf,
+			       struct list_head *temp_inactive_list)
+	__must_hold(&conf->device_lock)
+{
+	struct stripe_head *sh, *t;
+	int count = 0;
+	struct llist_node *head;
+
+	head = llist_del_all(&conf->released_stripes);
+	head = llist_reverse_order(head);
+	llist_for_each_entry_safe(sh, t, head, release_list) {
+		int hash;
+
+		/* sh could be readded after STRIPE_ON_RELEASE_LIST is cleard */
+		smp_mb();
+		clear_bit(STRIPE_ON_RELEASE_LIST, &sh->state);
+		/*
+		 * Don't worry the bit is set here, because if the bit is set
+		 * again, the count is always > 1. This is true for
+		 * STRIPE_ON_UNPLUG_LIST bit too.
+		 */
+		hash = sh->hash_lock_index;
+		__release_stripe(conf, sh, &temp_inactive_list[hash]);
+		count++;
+	}
+
+	return count;
+}
+
+void raid5_release_stripe(struct stripe_head *sh)
+{
+	struct r5conf *conf = sh->raid_conf;
+	unsigned long flags;
+	struct list_head list;
+	int hash;
+	bool wakeup;
+
+	/* Avoid release_list until the last reference.
+	 */
+	if (atomic_add_unless(&sh->count, -1, 1))
+		return;
+
+	if (unlikely(!conf->mddev->thread) ||
+		test_and_set_bit(STRIPE_ON_RELEASE_LIST, &sh->state))
+		goto slow_path;
+	wakeup = llist_add(&sh->release_list, &conf->released_stripes);
+	if (wakeup)
+		md_wakeup_thread(conf->mddev->thread);
+	return;
+slow_path:
+	/* we are ok here if STRIPE_ON_RELEASE_LIST is set or not */
+	if (atomic_dec_and_lock_irqsave(&sh->count, &conf->device_lock, flags)) {
+		INIT_LIST_HEAD(&list);
+		hash = sh->hash_lock_index;
+		do_release_stripe(conf, sh, &list);
+		spin_unlock_irqrestore(&conf->device_lock, flags);
+		release_inactive_stripe_list(conf, &list, hash);
+	}
+}
+
+static inline void remove_hash(struct stripe_head *sh)
+{
+	pr_debug("remove_hash(), stripe %llu\n",
+		(unsigned long long)sh->sector);
+
+	hlist_del_init(&sh->hash);
+}
+
+static inline void insert_hash(struct r5conf *conf, struct stripe_head *sh)
+{
+	struct hlist_head *hp = stripe_hash(conf, sh->sector);
+
+	pr_debug("insert_hash(), stripe %llu\n",
+		(unsigned long long)sh->sector);
+
+	hlist_add_head(&sh->hash, hp);
+}
+
+/* find an idle stripe, make sure it is unhashed, and return it. */
+static struct stripe_head *get_free_stripe(struct r5conf *conf, int hash)
+{
+	struct stripe_head *sh = NULL;
+	struct list_head *first;
+
+	if (list_empty(conf->inactive_list + hash))
+		goto out;
+	first = (conf->inactive_list + hash)->next;
+	sh = list_entry(first, struct stripe_head, lru);
+	list_del_init(first);
+	remove_hash(sh);
+	atomic_inc(&conf->active_stripes);
+	BUG_ON(hash != sh->hash_lock_index);
+	if (list_empty(conf->inactive_list + hash))
+		atomic_inc(&conf->empty_inactive_list_nr);
+out:
+	return sh;
+}
+
+#if PAGE_SIZE != DEFAULT_STRIPE_SIZE
+static void free_stripe_pages(struct stripe_head *sh)
+{
+	int i;
+	struct page *p;
+
+	/* Have not allocate page pool */
+	if (!sh->pages)
+		return;
+
+	for (i = 0; i < sh->nr_pages; i++) {
+		p = sh->pages[i];
+		if (p)
+			put_page(p);
+		sh->pages[i] = NULL;
+	}
+}
+
+static int alloc_stripe_pages(struct stripe_head *sh, gfp_t gfp)
+{
+	int i;
+	struct page *p;
+
+	for (i = 0; i < sh->nr_pages; i++) {
+		/* The page have allocated. */
+		if (sh->pages[i])
+			continue;
+
+		p = alloc_page(gfp);
+		if (!p) {
+			free_stripe_pages(sh);
+			return -ENOMEM;
+		}
+		sh->pages[i] = p;
+	}
+	return 0;
+}
+
+static int
+init_stripe_shared_pages(struct stripe_head *sh, struct r5conf *conf, int disks)
+{
+	int nr_pages, cnt;
+
+	if (sh->pages)
+		return 0;
+
+	/* Each of the sh->dev[i] need one conf->stripe_size */
+	cnt = PAGE_SIZE / conf->stripe_size;
+	nr_pages = (disks + cnt - 1) / cnt;
+
+	sh->pages = kcalloc(nr_pages, sizeof(struct page *), GFP_KERNEL);
+	if (!sh->pages)
+		return -ENOMEM;
+	sh->nr_pages = nr_pages;
+	sh->stripes_per_page = cnt;
+	return 0;
+}
+#endif
+
+static void shrink_buffers(struct stripe_head *sh)
+{
+	int i;
+	int num = sh->raid_conf->pool_size;
+
+#if PAGE_SIZE == DEFAULT_STRIPE_SIZE
+	for (i = 0; i < num ; i++) {
+		struct page *p;
+
+		WARN_ON(sh->dev[i].page != sh->dev[i].orig_page);
+		p = sh->dev[i].page;
+		if (!p)
+			continue;
+		sh->dev[i].page = NULL;
+		put_page(p);
+	}
+#else
+	for (i = 0; i < num; i++)
+		sh->dev[i].page = NULL;
+	free_stripe_pages(sh); /* Free pages */
+#endif
+}
+
+static int grow_buffers(struct stripe_head *sh, gfp_t gfp)
+{
+	int i;
+	int num = sh->raid_conf->pool_size;
+
+#if PAGE_SIZE == DEFAULT_STRIPE_SIZE
+	for (i = 0; i < num; i++) {
+		struct page *page;
+
+		if (!(page = alloc_page(gfp))) {
+			return 1;
+		}
+		sh->dev[i].page = page;
+		sh->dev[i].orig_page = page;
+		sh->dev[i].offset = 0;
+	}
+#else
+	if (alloc_stripe_pages(sh, gfp))
+		return -ENOMEM;
+
+	for (i = 0; i < num; i++) {
+		sh->dev[i].page = raid5_get_dev_page(sh, i);
+		sh->dev[i].orig_page = sh->dev[i].page;
+		sh->dev[i].offset = raid5_get_page_offset(sh, i);
+	}
+#endif
+	return 0;
+}
+
+static void stripe_set_idx(sector_t stripe, struct r5conf *conf, int previous,
+			    struct stripe_head *sh);
+
+static void init_stripe(struct stripe_head *sh, sector_t sector, int previous)
+{
+	struct r5conf *conf = sh->raid_conf;
+	int i, seq;
+
+	BUG_ON(atomic_read(&sh->count) != 0);
+	BUG_ON(test_bit(STRIPE_HANDLE, &sh->state));
+	BUG_ON(stripe_operations_active(sh));
+	BUG_ON(sh->batch_head);
+
+	pr_debug("init_stripe called, stripe %llu\n",
+		(unsigned long long)sector);
+retry:
+	seq = read_seqcount_begin(&conf->gen_lock);
+	sh->generation = conf->generation - previous;
+	sh->disks = previous ? conf->previous_raid_disks : conf->raid_disks;
+	sh->sector = sector;
+	stripe_set_idx(sector, conf, previous, sh);
+	sh->state = 0;
+
+	for (i = sh->disks; i--; ) {
+		struct r5dev *dev = &sh->dev[i];
+
+		if (dev->toread || dev->read || dev->towrite || dev->written ||
+		    test_bit(R5_LOCKED, &dev->flags)) {
+			pr_err("sector=%llx i=%d %p %p %p %p %d\n",
+			       (unsigned long long)sh->sector, i, dev->toread,
+			       dev->read, dev->towrite, dev->written,
+			       test_bit(R5_LOCKED, &dev->flags));
+			WARN_ON(1);
+		}
+		dev->flags = 0;
+		dev->sector = raid5_compute_blocknr(sh, i, previous);
+	}
+	if (read_seqcount_retry(&conf->gen_lock, seq))
+		goto retry;
+	sh->overwrite_disks = 0;
+	insert_hash(conf, sh);
+	sh->cpu = smp_processor_id();
+	set_bit(STRIPE_BATCH_READY, &sh->state);
+}
+
+static struct stripe_head *__find_stripe(struct r5conf *conf, sector_t sector,
+					 short generation)
+{
+	struct stripe_head *sh;
+
+	pr_debug("__find_stripe, sector %llu\n", (unsigned long long)sector);
+	hlist_for_each_entry(sh, stripe_hash(conf, sector), hash)
+		if (sh->sector == sector && sh->generation == generation)
+			return sh;
+	pr_debug("__stripe %llu not in cache\n", (unsigned long long)sector);
+	return NULL;
+}
+
+static struct stripe_head *find_get_stripe(struct r5conf *conf,
+		sector_t sector, short generation, int hash)
+{
+	int inc_empty_inactive_list_flag;
+	struct stripe_head *sh;
+
+	sh = __find_stripe(conf, sector, generation);
+	if (!sh)
+		return NULL;
+
+	if (atomic_inc_not_zero(&sh->count))
+		return sh;
+
+	/*
+	 * Slow path. The reference count is zero which means the stripe must
+	 * be on a list (sh->lru). Must remove the stripe from the list that
+	 * references it with the device_lock held.
+	 */
+
+	spin_lock(&conf->device_lock);
+	if (!atomic_read(&sh->count)) {
+		if (!test_bit(STRIPE_HANDLE, &sh->state))
+			atomic_inc(&conf->active_stripes);
+		BUG_ON(list_empty(&sh->lru) &&
+		       !test_bit(STRIPE_EXPANDING, &sh->state));
+		inc_empty_inactive_list_flag = 0;
+		if (!list_empty(conf->inactive_list + hash))
+			inc_empty_inactive_list_flag = 1;
+		list_del_init(&sh->lru);
+		if (list_empty(conf->inactive_list + hash) &&
+		    inc_empty_inactive_list_flag)
+			atomic_inc(&conf->empty_inactive_list_nr);
+		if (sh->group) {
+			sh->group->stripes_cnt--;
+			sh->group = NULL;
+		}
+	}
+	atomic_inc(&sh->count);
+	spin_unlock(&conf->device_lock);
+
+	return sh;
+}
+
+/*
+ * Need to check if array has failed when deciding whether to:
+ *  - start an array
+ *  - remove non-faulty devices
+ *  - add a spare
+ *  - allow a reshape
+ * This determination is simple when no reshape is happening.
+ * However if there is a reshape, we need to carefully check
+ * both the before and after sections.
+ * This is because some failed devices may only affect one
+ * of the two sections, and some non-in_sync devices may
+ * be insync in the section most affected by failed devices.
+ *
+ * Most calls to this function hold &conf->device_lock. Calls
+ * in raid5_run() do not require the lock as no other threads
+ * have been started yet.
+ */
+int raid5_calc_degraded(struct r5conf *conf)
+{
+	int degraded, degraded2;
+	int i;
+
+	rcu_read_lock();
+	degraded = 0;
+	for (i = 0; i < conf->previous_raid_disks; i++) {
+		struct md_rdev *rdev = rcu_dereference(conf->disks[i].rdev);
+		if (rdev && test_bit(Faulty, &rdev->flags))
+			rdev = rcu_dereference(conf->disks[i].replacement);
+		if (!rdev || test_bit(Faulty, &rdev->flags))
+			degraded++;
+		else if (test_bit(In_sync, &rdev->flags))
+			;
+		else
+			/* not in-sync or faulty.
+			 * If the reshape increases the number of devices,
+			 * this is being recovered by the reshape, so
+			 * this 'previous' section is not in_sync.
+			 * If the number of devices is being reduced however,
+			 * the device can only be part of the array if
+			 * we are reverting a reshape, so this section will
+			 * be in-sync.
+			 */
+			if (conf->raid_disks >= conf->previous_raid_disks)
+				degraded++;
+	}
+	rcu_read_unlock();
+	if (conf->raid_disks == conf->previous_raid_disks)
+		return degraded;
+	rcu_read_lock();
+	degraded2 = 0;
+	for (i = 0; i < conf->raid_disks; i++) {
+		struct md_rdev *rdev = rcu_dereference(conf->disks[i].rdev);
+		if (rdev && test_bit(Faulty, &rdev->flags))
+			rdev = rcu_dereference(conf->disks[i].replacement);
+		if (!rdev || test_bit(Faulty, &rdev->flags))
+			degraded2++;
+		else if (test_bit(In_sync, &rdev->flags))
+			;
+		else
+			/* not in-sync or faulty.
+			 * If reshape increases the number of devices, this
+			 * section has already been recovered, else it
+			 * almost certainly hasn't.
+			 */
+			if (conf->raid_disks <= conf->previous_raid_disks)
+				degraded2++;
+	}
+	rcu_read_unlock();
+	if (degraded2 > degraded)
+		return degraded2;
+	return degraded;
+}
+
+static bool has_failed(struct r5conf *conf)
+{
+	int degraded = conf->mddev->degraded;
+
+	if (test_bit(MD_BROKEN, &conf->mddev->flags))
+		return true;
+
+	if (conf->mddev->reshape_position != MaxSector)
+		degraded = raid5_calc_degraded(conf);
+
+	return degraded > conf->max_degraded;
+}
+
+enum stripe_result {
+	STRIPE_SUCCESS = 0,
+	STRIPE_RETRY,
+	STRIPE_SCHEDULE_AND_RETRY,
+	STRIPE_FAIL,
+};
+
+struct stripe_request_ctx {
+	/* a reference to the last stripe_head for batching */
+	struct stripe_head *batch_last;
+
+	/* first sector in the request */
+	sector_t first_sector;
+
+	/* last sector in the request */
+	sector_t last_sector;
+
+	/*
+	 * bitmap to track stripe sectors that have been added to stripes
+	 * add one to account for unaligned requests
+	 */
+	DECLARE_BITMAP(sectors_to_do, RAID5_MAX_REQ_STRIPES + 1);
+
+	/* the request had REQ_PREFLUSH, cleared after the first stripe_head */
+	bool do_flush;
+};
+
+/*
+ * Block until another thread clears R5_INACTIVE_BLOCKED or
+ * there are fewer than 3/4 the maximum number of active stripes
+ * and there is an inactive stripe available.
+ */
+static bool is_inactive_blocked(struct r5conf *conf, int hash)
+{
+	if (list_empty(conf->inactive_list + hash))
+		return false;
+
+	if (!test_bit(R5_INACTIVE_BLOCKED, &conf->cache_state))
+		return true;
+
+	return (atomic_read(&conf->active_stripes) <
+		(conf->max_nr_stripes * 3 / 4));
+}
+
+struct stripe_head *raid5_get_active_stripe(struct r5conf *conf,
+		struct stripe_request_ctx *ctx, sector_t sector,
+		unsigned int flags)
+{
+	struct stripe_head *sh;
+	int hash = stripe_hash_locks_hash(conf, sector);
+	int previous = !!(flags & R5_GAS_PREVIOUS);
+
+	pr_debug("get_stripe, sector %llu\n", (unsigned long long)sector);
+
+	spin_lock_irq(conf->hash_locks + hash);
+
+	for (;;) {
+		if (!(flags & R5_GAS_NOQUIESCE) && conf->quiesce) {
+			/*
+			 * Must release the reference to batch_last before
+			 * waiting, on quiesce, otherwise the batch_last will
+			 * hold a reference to a stripe and raid5_quiesce()
+			 * will deadlock waiting for active_stripes to go to
+			 * zero.
+			 */
+			if (ctx && ctx->batch_last) {
+				raid5_release_stripe(ctx->batch_last);
+				ctx->batch_last = NULL;
+			}
+
+			wait_event_lock_irq(conf->wait_for_quiescent,
+					    !conf->quiesce,
+					    *(conf->hash_locks + hash));
+		}
+
+		sh = find_get_stripe(conf, sector, conf->generation - previous,
+				     hash);
+		if (sh)
+			break;
+
+		if (!test_bit(R5_INACTIVE_BLOCKED, &conf->cache_state)) {
+			sh = get_free_stripe(conf, hash);
+			if (sh) {
+				r5c_check_stripe_cache_usage(conf);
+				init_stripe(sh, sector, previous);
+				atomic_inc(&sh->count);
+				break;
+			}
+
+			if (!test_bit(R5_DID_ALLOC, &conf->cache_state))
+				set_bit(R5_ALLOC_MORE, &conf->cache_state);
+		}
+
+		if (flags & R5_GAS_NOBLOCK)
+			break;
+
+		set_bit(R5_INACTIVE_BLOCKED, &conf->cache_state);
+		r5l_wake_reclaim(conf->log, 0);
+
+		/* release batch_last before wait to avoid risk of deadlock */
+		if (ctx && ctx->batch_last) {
+			raid5_release_stripe(ctx->batch_last);
+			ctx->batch_last = NULL;
+		}
+
+		wait_event_lock_irq(conf->wait_for_stripe,
+				    is_inactive_blocked(conf, hash),
+				    *(conf->hash_locks + hash));
+		clear_bit(R5_INACTIVE_BLOCKED, &conf->cache_state);
+	}
+
+	spin_unlock_irq(conf->hash_locks + hash);
+	return sh;
+}
+
+static bool is_full_stripe_write(struct stripe_head *sh)
+{
+	BUG_ON(sh->overwrite_disks > (sh->disks - sh->raid_conf->max_degraded));
+	return sh->overwrite_disks == (sh->disks - sh->raid_conf->max_degraded);
+}
+
+static void lock_two_stripes(struct stripe_head *sh1, struct stripe_head *sh2)
+		__acquires(&sh1->stripe_lock)
+		__acquires(&sh2->stripe_lock)
+{
+	if (sh1 > sh2) {
+		spin_lock_irq(&sh2->stripe_lock);
+		spin_lock_nested(&sh1->stripe_lock, 1);
+	} else {
+		spin_lock_irq(&sh1->stripe_lock);
+		spin_lock_nested(&sh2->stripe_lock, 1);
+	}
+}
+
+static void unlock_two_stripes(struct stripe_head *sh1, struct stripe_head *sh2)
+		__releases(&sh1->stripe_lock)
+		__releases(&sh2->stripe_lock)
+{
+	spin_unlock(&sh1->stripe_lock);
+	spin_unlock_irq(&sh2->stripe_lock);
+}
+
+/* Only freshly new full stripe normal write stripe can be added to a batch list */
+static bool stripe_can_batch(struct stripe_head *sh)
+{
+	struct r5conf *conf = sh->raid_conf;
+
+	if (raid5_has_log(conf) || raid5_has_ppl(conf))
+		return false;
+	return test_bit(STRIPE_BATCH_READY, &sh->state) &&
+		!test_bit(STRIPE_BITMAP_PENDING, &sh->state) &&
+		is_full_stripe_write(sh);
+}
+
+/* we only do back search */
+static void stripe_add_to_batch_list(struct r5conf *conf,
+		struct stripe_head *sh, struct stripe_head *last_sh)
+{
+	struct stripe_head *head;
+	sector_t head_sector, tmp_sec;
+	int hash;
+	int dd_idx;
+
+	/* Don't cross chunks, so stripe pd_idx/qd_idx is the same */
+	tmp_sec = sh->sector;
+	if (!sector_div(tmp_sec, conf->chunk_sectors))
+		return;
+	head_sector = sh->sector - RAID5_STRIPE_SECTORS(conf);
+
+	if (last_sh && head_sector == last_sh->sector) {
+		head = last_sh;
+		atomic_inc(&head->count);
+	} else {
+		hash = stripe_hash_locks_hash(conf, head_sector);
+		spin_lock_irq(conf->hash_locks + hash);
+		head = find_get_stripe(conf, head_sector, conf->generation,
+				       hash);
+		spin_unlock_irq(conf->hash_locks + hash);
+		if (!head)
+			return;
+		if (!stripe_can_batch(head))
+			goto out;
+	}
+
+	lock_two_stripes(head, sh);
+	/* clear_batch_ready clear the flag */
+	if (!stripe_can_batch(head) || !stripe_can_batch(sh))
+		goto unlock_out;
+
+	if (sh->batch_head)
+		goto unlock_out;
+
+	dd_idx = 0;
+	while (dd_idx == sh->pd_idx || dd_idx == sh->qd_idx)
+		dd_idx++;
+	if (head->dev[dd_idx].towrite->bi_opf != sh->dev[dd_idx].towrite->bi_opf ||
+	    bio_op(head->dev[dd_idx].towrite) != bio_op(sh->dev[dd_idx].towrite))
+		goto unlock_out;
+
+	if (head->batch_head) {
+		spin_lock(&head->batch_head->batch_lock);
+		/* This batch list is already running */
+		if (!stripe_can_batch(head)) {
+			spin_unlock(&head->batch_head->batch_lock);
+			goto unlock_out;
+		}
+		/*
+		 * We must assign batch_head of this stripe within the
+		 * batch_lock, otherwise clear_batch_ready of batch head
+		 * stripe could clear BATCH_READY bit of this stripe and
+		 * this stripe->batch_head doesn't get assigned, which
+		 * could confuse clear_batch_ready for this stripe
+		 */
+		sh->batch_head = head->batch_head;
+
+		/*
+		 * at this point, head's BATCH_READY could be cleared, but we
+		 * can still add the stripe to batch list
+		 */
+		list_add(&sh->batch_list, &head->batch_list);
+		spin_unlock(&head->batch_head->batch_lock);
+	} else {
+		head->batch_head = head;
+		sh->batch_head = head->batch_head;
+		spin_lock(&head->batch_lock);
+		list_add_tail(&sh->batch_list, &head->batch_list);
+		spin_unlock(&head->batch_lock);
+	}
+
+	if (test_and_clear_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
+		if (atomic_dec_return(&conf->preread_active_stripes)
+		    < IO_THRESHOLD)
+			md_wakeup_thread(conf->mddev->thread);
+
+	if (test_and_clear_bit(STRIPE_BIT_DELAY, &sh->state)) {
+		int seq = sh->bm_seq;
+		if (test_bit(STRIPE_BIT_DELAY, &sh->batch_head->state) &&
+		    sh->batch_head->bm_seq > seq)
+			seq = sh->batch_head->bm_seq;
+		set_bit(STRIPE_BIT_DELAY, &sh->batch_head->state);
+		sh->batch_head->bm_seq = seq;
+	}
+
+	atomic_inc(&sh->count);
+unlock_out:
+	unlock_two_stripes(head, sh);
+out:
+	raid5_release_stripe(head);
+}
+
+/* Determine if 'data_offset' or 'new_data_offset' should be used
+ * in this stripe_head.
+ */
+static int use_new_offset(struct r5conf *conf, struct stripe_head *sh)
+{
+	sector_t progress = conf->reshape_progress;
+	/* Need a memory barrier to make sure we see the value
+	 * of conf->generation, or ->data_offset that was set before
+	 * reshape_progress was updated.
+	 */
+	smp_rmb();
+	if (progress == MaxSector)
+		return 0;
+	if (sh->generation == conf->generation - 1)
+		return 0;
+	/* We are in a reshape, and this is a new-generation stripe,
+	 * so use new_data_offset.
+	 */
+	return 1;
+}
+
+static void dispatch_bio_list(struct bio_list *tmp)
+{
+	struct bio *bio;
+
+	while ((bio = bio_list_pop(tmp)))
+		submit_bio_noacct(bio);
+}
+
+static int cmp_stripe(void *priv, const struct list_head *a,
+		      const struct list_head *b)
+{
+	const struct r5pending_data *da = list_entry(a,
+				struct r5pending_data, sibling);
+	const struct r5pending_data *db = list_entry(b,
+				struct r5pending_data, sibling);
+	if (da->sector > db->sector)
+		return 1;
+	if (da->sector < db->sector)
+		return -1;
+	return 0;
+}
+
+static void dispatch_defer_bios(struct r5conf *conf, int target,
+				struct bio_list *list)
+{
+	struct r5pending_data *data;
+	struct list_head *first, *next = NULL;
+	int cnt = 0;
+
+	if (conf->pending_data_cnt == 0)
+		return;
+
+	list_sort(NULL, &conf->pending_list, cmp_stripe);
+
+	first = conf->pending_list.next;
+
+	/* temporarily move the head */
+	if (conf->next_pending_data)
+		list_move_tail(&conf->pending_list,
+				&conf->next_pending_data->sibling);
+
+	while (!list_empty(&conf->pending_list)) {
+		data = list_first_entry(&conf->pending_list,
+			struct r5pending_data, sibling);
+		if (&data->sibling == first)
+			first = data->sibling.next;
+		next = data->sibling.next;
+
+		bio_list_merge(list, &data->bios);
+		list_move(&data->sibling, &conf->free_list);
+		cnt++;
+		if (cnt >= target)
+			break;
+	}
+	conf->pending_data_cnt -= cnt;
+	BUG_ON(conf->pending_data_cnt < 0 || cnt < target);
+
+	if (next != &conf->pending_list)
+		conf->next_pending_data = list_entry(next,
+				struct r5pending_data, sibling);
+	else
+		conf->next_pending_data = NULL;
+	/* list isn't empty */
+	if (first != &conf->pending_list)
+		list_move_tail(&conf->pending_list, first);
+}
+
+static void flush_deferred_bios(struct r5conf *conf)
+{
+	struct bio_list tmp = BIO_EMPTY_LIST;
+
+	if (conf->pending_data_cnt == 0)
+		return;
+
+	spin_lock(&conf->pending_bios_lock);
+	dispatch_defer_bios(conf, conf->pending_data_cnt, &tmp);
+	BUG_ON(conf->pending_data_cnt != 0);
+	spin_unlock(&conf->pending_bios_lock);
+
+	dispatch_bio_list(&tmp);
+}
+
+static void defer_issue_bios(struct r5conf *conf, sector_t sector,
+				struct bio_list *bios)
+{
+	struct bio_list tmp = BIO_EMPTY_LIST;
+	struct r5pending_data *ent;
+
+	spin_lock(&conf->pending_bios_lock);
+	ent = list_first_entry(&conf->free_list, struct r5pending_data,
+							sibling);
+	list_move_tail(&ent->sibling, &conf->pending_list);
+	ent->sector = sector;
+	bio_list_init(&ent->bios);
+	bio_list_merge(&ent->bios, bios);
+	conf->pending_data_cnt++;
+	if (conf->pending_data_cnt >= PENDING_IO_MAX)
+		dispatch_defer_bios(conf, PENDING_IO_ONE_FLUSH, &tmp);
+
+	spin_unlock(&conf->pending_bios_lock);
+
+	dispatch_bio_list(&tmp);
+}
+
+static void
+raid5_end_read_request(struct bio *bi);
+static void
+raid5_end_write_request(struct bio *bi);
+
+static void ops_run_io(struct stripe_head *sh, struct stripe_head_state *s)
+{
+	struct r5conf *conf = sh->raid_conf;
+	int i, disks = sh->disks;
+	struct stripe_head *head_sh = sh;
+	struct bio_list pending_bios = BIO_EMPTY_LIST;
+	struct r5dev *dev;
+	bool should_defer;
+
+	might_sleep();
+
+	if (log_stripe(sh, s) == 0)
+		return;
+
+	should_defer = conf->batch_bio_dispatch && conf->group_cnt;
+
+	for (i = disks; i--; ) {
+		enum req_op op;
+		blk_opf_t op_flags = 0;
+		int replace_only = 0;
+		struct bio *bi, *rbi;
+		struct md_rdev *rdev, *rrdev = NULL;
+
+		sh = head_sh;
+		if (test_and_clear_bit(R5_Wantwrite, &sh->dev[i].flags)) {
+			op = REQ_OP_WRITE;
+			if (test_and_clear_bit(R5_WantFUA, &sh->dev[i].flags))
+				op_flags = REQ_FUA;
+			if (test_bit(R5_Discard, &sh->dev[i].flags))
+				op = REQ_OP_DISCARD;
+		} else if (test_and_clear_bit(R5_Wantread, &sh->dev[i].flags))
+			op = REQ_OP_READ;
+		else if (test_and_clear_bit(R5_WantReplace,
+					    &sh->dev[i].flags)) {
+			op = REQ_OP_WRITE;
+			replace_only = 1;
+		} else
+			continue;
+		if (test_and_clear_bit(R5_SyncIO, &sh->dev[i].flags))
+			op_flags |= REQ_SYNC;
+
+again:
+		dev = &sh->dev[i];
+		bi = &dev->req;
+		rbi = &dev->rreq; /* For writing to replacement */
+
+		rcu_read_lock();
+		rrdev = rcu_dereference(conf->disks[i].replacement);
+		smp_mb(); /* Ensure that if rrdev is NULL, rdev won't be */
+		rdev = rcu_dereference(conf->disks[i].rdev);
+		if (!rdev) {
+			rdev = rrdev;
+			rrdev = NULL;
+		}
+		if (op_is_write(op)) {
+			if (replace_only)
+				rdev = NULL;
+			if (rdev == rrdev)
+				/* We raced and saw duplicates */
+				rrdev = NULL;
+		} else {
+			if (test_bit(R5_ReadRepl, &head_sh->dev[i].flags) && rrdev)
+				rdev = rrdev;
+			rrdev = NULL;
+		}
+
+		if (rdev && test_bit(Faulty, &rdev->flags))
+			rdev = NULL;
+		if (rdev)
+			atomic_inc(&rdev->nr_pending);
+		if (rrdev && test_bit(Faulty, &rrdev->flags))
+			rrdev = NULL;
+		if (rrdev)
+			atomic_inc(&rrdev->nr_pending);
+		rcu_read_unlock();
+
+		/* We have already checked bad blocks for reads.  Now
+		 * need to check for writes.  We never accept write errors
+		 * on the replacement, so we don't to check rrdev.
+		 */
+		while (op_is_write(op) && rdev &&
+		       test_bit(WriteErrorSeen, &rdev->flags)) {
+			sector_t first_bad;
+			int bad_sectors;
+			int bad = is_badblock(rdev, sh->sector, RAID5_STRIPE_SECTORS(conf),
+					      &first_bad, &bad_sectors);
+			if (!bad)
+				break;
+
+			if (bad < 0) {
+				set_bit(BlockedBadBlocks, &rdev->flags);
+				if (!conf->mddev->external &&
+				    conf->mddev->sb_flags) {
+					/* It is very unlikely, but we might
+					 * still need to write out the
+					 * bad block log - better give it
+					 * a chance*/
+					md_check_recovery(conf->mddev);
+				}
+				/*
+				 * Because md_wait_for_blocked_rdev
+				 * will dec nr_pending, we must
+				 * increment it first.
+				 */
+				atomic_inc(&rdev->nr_pending);
+				md_wait_for_blocked_rdev(rdev, conf->mddev);
+			} else {
+				/* Acknowledged bad block - skip the write */
+				rdev_dec_pending(rdev, conf->mddev);
+				rdev = NULL;
+			}
+		}
+
+		if (rdev) {
+			if (s->syncing || s->expanding || s->expanded
+			    || s->replacing)
+				md_sync_acct(rdev->bdev, RAID5_STRIPE_SECTORS(conf));
+
+			set_bit(STRIPE_IO_STARTED, &sh->state);
+
+			bio_init(bi, rdev->bdev, &dev->vec, 1, op | op_flags);
+			bi->bi_end_io = op_is_write(op)
+				? raid5_end_write_request
+				: raid5_end_read_request;
+			bi->bi_private = sh;
+
+			pr_debug("%s: for %llu schedule op %d on disc %d\n",
+				__func__, (unsigned long long)sh->sector,
+				bi->bi_opf, i);
+			atomic_inc(&sh->count);
+			if (sh != head_sh)
+				atomic_inc(&head_sh->count);
+			if (use_new_offset(conf, sh))
+				bi->bi_iter.bi_sector = (sh->sector
+						 + rdev->new_data_offset);
+			else
+				bi->bi_iter.bi_sector = (sh->sector
+						 + rdev->data_offset);
+			if (test_bit(R5_ReadNoMerge, &head_sh->dev[i].flags))
+				bi->bi_opf |= REQ_NOMERGE;
+
+			if (test_bit(R5_SkipCopy, &sh->dev[i].flags))
+				WARN_ON(test_bit(R5_UPTODATE, &sh->dev[i].flags));
+
+			if (!op_is_write(op) &&
+			    test_bit(R5_InJournal, &sh->dev[i].flags))
+				/*
+				 * issuing read for a page in journal, this
+				 * must be preparing for prexor in rmw; read
+				 * the data into orig_page
+				 */
+				sh->dev[i].vec.bv_page = sh->dev[i].orig_page;
+			else
+				sh->dev[i].vec.bv_page = sh->dev[i].page;
+			bi->bi_vcnt = 1;
+			bi->bi_io_vec[0].bv_len = RAID5_STRIPE_SIZE(conf);
+			bi->bi_io_vec[0].bv_offset = sh->dev[i].offset;
+			bi->bi_iter.bi_size = RAID5_STRIPE_SIZE(conf);
+			/*
+			 * If this is discard request, set bi_vcnt 0. We don't
+			 * want to confuse SCSI because SCSI will replace payload
+			 */
+			if (op == REQ_OP_DISCARD)
+				bi->bi_vcnt = 0;
+			if (rrdev)
+				set_bit(R5_DOUBLE_LOCKED, &sh->dev[i].flags);
+
+			if (conf->mddev->gendisk)
+				trace_block_bio_remap(bi,
+						disk_devt(conf->mddev->gendisk),
+						sh->dev[i].sector);
+			if (should_defer && op_is_write(op))
+				bio_list_add(&pending_bios, bi);
+			else
+				submit_bio_noacct(bi);
+		}
+		if (rrdev) {
+			if (s->syncing || s->expanding || s->expanded
+			    || s->replacing)
+				md_sync_acct(rrdev->bdev, RAID5_STRIPE_SECTORS(conf));
+
+			set_bit(STRIPE_IO_STARTED, &sh->state);
+
+			bio_init(rbi, rrdev->bdev, &dev->rvec, 1, op | op_flags);
+			BUG_ON(!op_is_write(op));
+			rbi->bi_end_io = raid5_end_write_request;
+			rbi->bi_private = sh;
+
+			pr_debug("%s: for %llu schedule op %d on "
+				 "replacement disc %d\n",
+				__func__, (unsigned long long)sh->sector,
+				rbi->bi_opf, i);
+			atomic_inc(&sh->count);
+			if (sh != head_sh)
+				atomic_inc(&head_sh->count);
+			if (use_new_offset(conf, sh))
+				rbi->bi_iter.bi_sector = (sh->sector
+						  + rrdev->new_data_offset);
+			else
+				rbi->bi_iter.bi_sector = (sh->sector
+						  + rrdev->data_offset);
+			if (test_bit(R5_SkipCopy, &sh->dev[i].flags))
+				WARN_ON(test_bit(R5_UPTODATE, &sh->dev[i].flags));
+			sh->dev[i].rvec.bv_page = sh->dev[i].page;
+			rbi->bi_vcnt = 1;
+			rbi->bi_io_vec[0].bv_len = RAID5_STRIPE_SIZE(conf);
+			rbi->bi_io_vec[0].bv_offset = sh->dev[i].offset;
+			rbi->bi_iter.bi_size = RAID5_STRIPE_SIZE(conf);
+			/*
+			 * If this is discard request, set bi_vcnt 0. We don't
+			 * want to confuse SCSI because SCSI will replace payload
+			 */
+			if (op == REQ_OP_DISCARD)
+				rbi->bi_vcnt = 0;
+			if (conf->mddev->gendisk)
+				trace_block_bio_remap(rbi,
+						disk_devt(conf->mddev->gendisk),
+						sh->dev[i].sector);
+			if (should_defer && op_is_write(op))
+				bio_list_add(&pending_bios, rbi);
+			else
+				submit_bio_noacct(rbi);
+		}
+		if (!rdev && !rrdev) {
+			if (op_is_write(op))
+				set_bit(STRIPE_DEGRADED, &sh->state);
+			pr_debug("skip op %d on disc %d for sector %llu\n",
+				bi->bi_opf, i, (unsigned long long)sh->sector);
+			clear_bit(R5_LOCKED, &sh->dev[i].flags);
+			set_bit(STRIPE_HANDLE, &sh->state);
+		}
+
+		if (!head_sh->batch_head)
+			continue;
+		sh = list_first_entry(&sh->batch_list, struct stripe_head,
+				      batch_list);
+		if (sh != head_sh)
+			goto again;
+	}
+
+	if (should_defer && !bio_list_empty(&pending_bios))
+		defer_issue_bios(conf, head_sh->sector, &pending_bios);
+}
+
+static struct dma_async_tx_descriptor *
+async_copy_data(int frombio, struct bio *bio, struct page **page,
+	unsigned int poff, sector_t sector, struct dma_async_tx_descriptor *tx,
+	struct stripe_head *sh, int no_skipcopy)
+{
+	struct bio_vec bvl;
+	struct bvec_iter iter;
+	struct page *bio_page;
+	int page_offset;
+	struct async_submit_ctl submit;
+	enum async_tx_flags flags = 0;
+	struct r5conf *conf = sh->raid_conf;
+
+	if (bio->bi_iter.bi_sector >= sector)
+		page_offset = (signed)(bio->bi_iter.bi_sector - sector) * 512;
+	else
+		page_offset = (signed)(sector - bio->bi_iter.bi_sector) * -512;
+
+	if (frombio)
+		flags |= ASYNC_TX_FENCE;
+	init_async_submit(&submit, flags, tx, NULL, NULL, NULL);
+
+	bio_for_each_segment(bvl, bio, iter) {
+		int len = bvl.bv_len;
+		int clen;
+		int b_offset = 0;
+
+		if (page_offset < 0) {
+			b_offset = -page_offset;
+			page_offset += b_offset;
+			len -= b_offset;
+		}
+
+		if (len > 0 && page_offset + len > RAID5_STRIPE_SIZE(conf))
+			clen = RAID5_STRIPE_SIZE(conf) - page_offset;
+		else
+			clen = len;
+
+		if (clen > 0) {
+			b_offset += bvl.bv_offset;
+			bio_page = bvl.bv_page;
+			if (frombio) {
+				if (conf->skip_copy &&
+				    b_offset == 0 && page_offset == 0 &&
+				    clen == RAID5_STRIPE_SIZE(conf) &&
+				    !no_skipcopy)
+					*page = bio_page;
+				else
+					tx = async_memcpy(*page, bio_page, page_offset + poff,
+						  b_offset, clen, &submit);
+			} else
+				tx = async_memcpy(bio_page, *page, b_offset,
+						  page_offset + poff, clen, &submit);
+		}
+		/* chain the operations */
+		submit.depend_tx = tx;
+
+		if (clen < len) /* hit end of page */
+			break;
+		page_offset +=  len;
+	}
+
+	return tx;
+}
+
+static void ops_complete_biofill(void *stripe_head_ref)
+{
+	struct stripe_head *sh = stripe_head_ref;
+	int i;
+	struct r5conf *conf = sh->raid_conf;
+
+	pr_debug("%s: stripe %llu\n", __func__,
+		(unsigned long long)sh->sector);
+
+	/* clear completed biofills */
+	for (i = sh->disks; i--; ) {
+		struct r5dev *dev = &sh->dev[i];
+
+		/* acknowledge completion of a biofill operation */
+		/* and check if we need to reply to a read request,
+		 * new R5_Wantfill requests are held off until
+		 * !STRIPE_BIOFILL_RUN
+		 */
+		if (test_and_clear_bit(R5_Wantfill, &dev->flags)) {
+			struct bio *rbi, *rbi2;
+
+			BUG_ON(!dev->read);
+			rbi = dev->read;
+			dev->read = NULL;
+			while (rbi && rbi->bi_iter.bi_sector <
+				dev->sector + RAID5_STRIPE_SECTORS(conf)) {
+				rbi2 = r5_next_bio(conf, rbi, dev->sector);
+				bio_endio(rbi);
+				rbi = rbi2;
+			}
+		}
+	}
+	clear_bit(STRIPE_BIOFILL_RUN, &sh->state);
+
+	set_bit(STRIPE_HANDLE, &sh->state);
+	raid5_release_stripe(sh);
+}
+
+static void ops_run_biofill(struct stripe_head *sh)
+{
+	struct dma_async_tx_descriptor *tx = NULL;
+	struct async_submit_ctl submit;
+	int i;
+	struct r5conf *conf = sh->raid_conf;
+
+	BUG_ON(sh->batch_head);
+	pr_debug("%s: stripe %llu\n", __func__,
+		(unsigned long long)sh->sector);
+
+	for (i = sh->disks; i--; ) {
+		struct r5dev *dev = &sh->dev[i];
+		if (test_bit(R5_Wantfill, &dev->flags)) {
+			struct bio *rbi;
+			spin_lock_irq(&sh->stripe_lock);
+			dev->read = rbi = dev->toread;
+			dev->toread = NULL;
+			spin_unlock_irq(&sh->stripe_lock);
+			while (rbi && rbi->bi_iter.bi_sector <
+				dev->sector + RAID5_STRIPE_SECTORS(conf)) {
+				tx = async_copy_data(0, rbi, &dev->page,
+						     dev->offset,
+						     dev->sector, tx, sh, 0);
+				rbi = r5_next_bio(conf, rbi, dev->sector);
+			}
+		}
+	}
+
+	atomic_inc(&sh->count);
+	init_async_submit(&submit, ASYNC_TX_ACK, tx, ops_complete_biofill, sh, NULL);
+	async_trigger_callback(&submit);
+}
+
+static void mark_target_uptodate(struct stripe_head *sh, int target)
+{
+	struct r5dev *tgt;
+
+	if (target < 0)
+		return;
+
+	tgt = &sh->dev[target];
+	set_bit(R5_UPTODATE, &tgt->flags);
+	BUG_ON(!test_bit(R5_Wantcompute, &tgt->flags));
+	clear_bit(R5_Wantcompute, &tgt->flags);
+}
+
+static void ops_complete_compute(void *stripe_head_ref)
+{
+	struct stripe_head *sh = stripe_head_ref;
+
+	pr_debug("%s: stripe %llu\n", __func__,
+		(unsigned long long)sh->sector);
+
+	/* mark the computed target(s) as uptodate */
+	mark_target_uptodate(sh, sh->ops.target);
+	mark_target_uptodate(sh, sh->ops.target2);
+
+	clear_bit(STRIPE_COMPUTE_RUN, &sh->state);
+	if (sh->check_state == check_state_compute_run)
+		sh->check_state = check_state_compute_result;
+	set_bit(STRIPE_HANDLE, &sh->state);
+	raid5_release_stripe(sh);
+}
+
+/* return a pointer to the address conversion region of the scribble buffer */
+static struct page **to_addr_page(struct raid5_percpu *percpu, int i)
+{
+	return percpu->scribble + i * percpu->scribble_obj_size;
+}
+
+/* return a pointer to the address conversion region of the scribble buffer */
+static addr_conv_t *to_addr_conv(struct stripe_head *sh,
+				 struct raid5_percpu *percpu, int i)
+{
+	return (void *) (to_addr_page(percpu, i) + sh->disks + 2);
+}
+
+/*
+ * Return a pointer to record offset address.
+ */
+static unsigned int *
+to_addr_offs(struct stripe_head *sh, struct raid5_percpu *percpu)
+{
+	return (unsigned int *) (to_addr_conv(sh, percpu, 0) + sh->disks + 2);
+}
+
+static struct dma_async_tx_descriptor *
+ops_run_compute5(struct stripe_head *sh, struct raid5_percpu *percpu)
+{
+	int disks = sh->disks;
+	struct page **xor_srcs = to_addr_page(percpu, 0);
+	unsigned int *off_srcs = to_addr_offs(sh, percpu);
+	int target = sh->ops.target;
+	struct r5dev *tgt = &sh->dev[target];
+	struct page *xor_dest = tgt->page;
+	unsigned int off_dest = tgt->offset;
+	int count = 0;
+	struct dma_async_tx_descriptor *tx;
+	struct async_submit_ctl submit;
+	int i;
+
+	BUG_ON(sh->batch_head);
+
+	pr_debug("%s: stripe %llu block: %d\n",
+		__func__, (unsigned long long)sh->sector, target);
+	BUG_ON(!test_bit(R5_Wantcompute, &tgt->flags));
+
+	for (i = disks; i--; ) {
+		if (i != target) {
+			off_srcs[count] = sh->dev[i].offset;
+			xor_srcs[count++] = sh->dev[i].page;
+		}
+	}
+
+	atomic_inc(&sh->count);
+
+	init_async_submit(&submit, ASYNC_TX_FENCE|ASYNC_TX_XOR_ZERO_DST, NULL,
+			  ops_complete_compute, sh, to_addr_conv(sh, percpu, 0));
+	if (unlikely(count == 1))
+		tx = async_memcpy(xor_dest, xor_srcs[0], off_dest, off_srcs[0],
+				RAID5_STRIPE_SIZE(sh->raid_conf), &submit);
+	else
+		tx = async_xor_offs(xor_dest, off_dest, xor_srcs, off_srcs, count,
+				RAID5_STRIPE_SIZE(sh->raid_conf), &submit);
+
+	return tx;
+}
+
+/* set_syndrome_sources - populate source buffers for gen_syndrome
+ * @srcs - (struct page *) array of size sh->disks
+ * @offs - (unsigned int) array of offset for each page
+ * @sh - stripe_head to parse
+ *
+ * Populates srcs in proper layout order for the stripe and returns the
+ * 'count' of sources to be used in a call to async_gen_syndrome.  The P
+ * destination buffer is recorded in srcs[count] and the Q destination
+ * is recorded in srcs[count+1]].
+ */
+static int set_syndrome_sources(struct page **srcs,
+				unsigned int *offs,
+				struct stripe_head *sh,
+				int srctype)
+{
+	int disks = sh->disks;
+	int syndrome_disks = sh->ddf_layout ? disks : (disks - 2);
+	int d0_idx = raid6_d0(sh);
+	int count;
+	int i;
+
+	for (i = 0; i < disks; i++)
+		srcs[i] = NULL;
+
+	count = 0;
+	i = d0_idx;
+	do {
+		int slot = raid6_idx_to_slot(i, sh, &count, syndrome_disks);
+		struct r5dev *dev = &sh->dev[i];
+
+		if (i == sh->qd_idx || i == sh->pd_idx ||
+		    (srctype == SYNDROME_SRC_ALL) ||
+		    (srctype == SYNDROME_SRC_WANT_DRAIN &&
+		     (test_bit(R5_Wantdrain, &dev->flags) ||
+		      test_bit(R5_InJournal, &dev->flags))) ||
+		    (srctype == SYNDROME_SRC_WRITTEN &&
+		     (dev->written ||
+		      test_bit(R5_InJournal, &dev->flags)))) {
+			if (test_bit(R5_InJournal, &dev->flags))
+				srcs[slot] = sh->dev[i].orig_page;
+			else
+				srcs[slot] = sh->dev[i].page;
+			/*
+			 * For R5_InJournal, PAGE_SIZE must be 4KB and will
+			 * not shared page. In that case, dev[i].offset
+			 * is 0.
+			 */
+			offs[slot] = sh->dev[i].offset;
+		}
+		i = raid6_next_disk(i, disks);
+	} while (i != d0_idx);
+
+	return syndrome_disks;
+}
+
+static struct dma_async_tx_descriptor *
+ops_run_compute6_1(struct stripe_head *sh, struct raid5_percpu *percpu)
+{
+	int disks = sh->disks;
+	struct page **blocks = to_addr_page(percpu, 0);
+	unsigned int *offs = to_addr_offs(sh, percpu);
+	int target;
+	int qd_idx = sh->qd_idx;
+	struct dma_async_tx_descriptor *tx;
+	struct async_submit_ctl submit;
+	struct r5dev *tgt;
+	struct page *dest;
+	unsigned int dest_off;
+	int i;
+	int count;
+
+	BUG_ON(sh->batch_head);
+	if (sh->ops.target < 0)
+		target = sh->ops.target2;
+	else if (sh->ops.target2 < 0)
+		target = sh->ops.target;
+	else
+		/* we should only have one valid target */
+		BUG();
+	BUG_ON(target < 0);
+	pr_debug("%s: stripe %llu block: %d\n",
+		__func__, (unsigned long long)sh->sector, target);
+
+	tgt = &sh->dev[target];
+	BUG_ON(!test_bit(R5_Wantcompute, &tgt->flags));
+	dest = tgt->page;
+	dest_off = tgt->offset;
+
+	atomic_inc(&sh->count);
+
+	if (target == qd_idx) {
+		count = set_syndrome_sources(blocks, offs, sh, SYNDROME_SRC_ALL);
+		blocks[count] = NULL; /* regenerating p is not necessary */
+		BUG_ON(blocks[count+1] != dest); /* q should already be set */
+		init_async_submit(&submit, ASYNC_TX_FENCE, NULL,
+				  ops_complete_compute, sh,
+				  to_addr_conv(sh, percpu, 0));
+		tx = async_gen_syndrome(blocks, offs, count+2,
+				RAID5_STRIPE_SIZE(sh->raid_conf), &submit);
+	} else {
+		/* Compute any data- or p-drive using XOR */
+		count = 0;
+		for (i = disks; i-- ; ) {
+			if (i == target || i == qd_idx)
+				continue;
+			offs[count] = sh->dev[i].offset;
+			blocks[count++] = sh->dev[i].page;
+		}
+
+		init_async_submit(&submit, ASYNC_TX_FENCE|ASYNC_TX_XOR_ZERO_DST,
+				  NULL, ops_complete_compute, sh,
+				  to_addr_conv(sh, percpu, 0));
+		tx = async_xor_offs(dest, dest_off, blocks, offs, count,
+				RAID5_STRIPE_SIZE(sh->raid_conf), &submit);
+	}
+
+	return tx;
+}
+
+static struct dma_async_tx_descriptor *
+ops_run_compute6_2(struct stripe_head *sh, struct raid5_percpu *percpu)
+{
+	int i, count, disks = sh->disks;
+	int syndrome_disks = sh->ddf_layout ? disks : disks-2;
+	int d0_idx = raid6_d0(sh);
+	int faila = -1, failb = -1;
+	int target = sh->ops.target;
+	int target2 = sh->ops.target2;
+	struct r5dev *tgt = &sh->dev[target];
+	struct r5dev *tgt2 = &sh->dev[target2];
+	struct dma_async_tx_descriptor *tx;
+	struct page **blocks = to_addr_page(percpu, 0);
+	unsigned int *offs = to_addr_offs(sh, percpu);
+	struct async_submit_ctl submit;
+
+	BUG_ON(sh->batch_head);
+	pr_debug("%s: stripe %llu block1: %d block2: %d\n",
+		 __func__, (unsigned long long)sh->sector, target, target2);
+	BUG_ON(target < 0 || target2 < 0);
+	BUG_ON(!test_bit(R5_Wantcompute, &tgt->flags));
+	BUG_ON(!test_bit(R5_Wantcompute, &tgt2->flags));
+
+	/* we need to open-code set_syndrome_sources to handle the
+	 * slot number conversion for 'faila' and 'failb'
+	 */
+	for (i = 0; i < disks ; i++) {
+		offs[i] = 0;
+		blocks[i] = NULL;
+	}
+	count = 0;
+	i = d0_idx;
+	do {
+		int slot = raid6_idx_to_slot(i, sh, &count, syndrome_disks);
+
+		offs[slot] = sh->dev[i].offset;
+		blocks[slot] = sh->dev[i].page;
+
+		if (i == target)
+			faila = slot;
+		if (i == target2)
+			failb = slot;
+		i = raid6_next_disk(i, disks);
+	} while (i != d0_idx);
+
+	BUG_ON(faila == failb);
+	if (failb < faila)
+		swap(faila, failb);
+	pr_debug("%s: stripe: %llu faila: %d failb: %d\n",
+		 __func__, (unsigned long long)sh->sector, faila, failb);
+
+	atomic_inc(&sh->count);
+
+	if (failb == syndrome_disks+1) {
+		/* Q disk is one of the missing disks */
+		if (faila == syndrome_disks) {
+			/* Missing P+Q, just recompute */
+			init_async_submit(&submit, ASYNC_TX_FENCE, NULL,
+					  ops_complete_compute, sh,
+					  to_addr_conv(sh, percpu, 0));
+			return async_gen_syndrome(blocks, offs, syndrome_disks+2,
+						  RAID5_STRIPE_SIZE(sh->raid_conf),
+						  &submit);
+		} else {
+			struct page *dest;
+			unsigned int dest_off;
+			int data_target;
+			int qd_idx = sh->qd_idx;
+
+			/* Missing D+Q: recompute D from P, then recompute Q */
+			if (target == qd_idx)
+				data_target = target2;
+			else
+				data_target = target;
+
+			count = 0;
+			for (i = disks; i-- ; ) {
+				if (i == data_target || i == qd_idx)
+					continue;
+				offs[count] = sh->dev[i].offset;
+				blocks[count++] = sh->dev[i].page;
+			}
+			dest = sh->dev[data_target].page;
+			dest_off = sh->dev[data_target].offset;
+			init_async_submit(&submit,
+					  ASYNC_TX_FENCE|ASYNC_TX_XOR_ZERO_DST,
+					  NULL, NULL, NULL,
+					  to_addr_conv(sh, percpu, 0));
+			tx = async_xor_offs(dest, dest_off, blocks, offs, count,
+				       RAID5_STRIPE_SIZE(sh->raid_conf),
+				       &submit);
+
+			count = set_syndrome_sources(blocks, offs, sh, SYNDROME_SRC_ALL);
+			init_async_submit(&submit, ASYNC_TX_FENCE, tx,
+					  ops_complete_compute, sh,
+					  to_addr_conv(sh, percpu, 0));
+			return async_gen_syndrome(blocks, offs, count+2,
+						  RAID5_STRIPE_SIZE(sh->raid_conf),
+						  &submit);
+		}
+	} else {
+		init_async_submit(&submit, ASYNC_TX_FENCE, NULL,
+				  ops_complete_compute, sh,
+				  to_addr_conv(sh, percpu, 0));
+		if (failb == syndrome_disks) {
+			/* We're missing D+P. */
+			return async_raid6_datap_recov(syndrome_disks+2,
+						RAID5_STRIPE_SIZE(sh->raid_conf),
+						faila,
+						blocks, offs, &submit);
+		} else {
+			/* We're missing D+D. */
+			return async_raid6_2data_recov(syndrome_disks+2,
+						RAID5_STRIPE_SIZE(sh->raid_conf),
+						faila, failb,
+						blocks, offs, &submit);
+		}
+	}
+}
+
+static void ops_complete_prexor(void *stripe_head_ref)
+{
+	struct stripe_head *sh = stripe_head_ref;
+
+	pr_debug("%s: stripe %llu\n", __func__,
+		(unsigned long long)sh->sector);
+
+	if (r5c_is_writeback(sh->raid_conf->log))
+		/*
+		 * raid5-cache write back uses orig_page during prexor.
+		 * After prexor, it is time to free orig_page
+		 */
+		r5c_release_extra_page(sh);
+}
+
+static struct dma_async_tx_descriptor *
+ops_run_prexor5(struct stripe_head *sh, struct raid5_percpu *percpu,
+		struct dma_async_tx_descriptor *tx)
+{
+	int disks = sh->disks;
+	struct page **xor_srcs = to_addr_page(percpu, 0);
+	unsigned int *off_srcs = to_addr_offs(sh, percpu);
+	int count = 0, pd_idx = sh->pd_idx, i;
+	struct async_submit_ctl submit;
+
+	/* existing parity data subtracted */
+	unsigned int off_dest = off_srcs[count] = sh->dev[pd_idx].offset;
+	struct page *xor_dest = xor_srcs[count++] = sh->dev[pd_idx].page;
+
+	BUG_ON(sh->batch_head);
+	pr_debug("%s: stripe %llu\n", __func__,
+		(unsigned long long)sh->sector);
+
+	for (i = disks; i--; ) {
+		struct r5dev *dev = &sh->dev[i];
+		/* Only process blocks that are known to be uptodate */
+		if (test_bit(R5_InJournal, &dev->flags)) {
+			/*
+			 * For this case, PAGE_SIZE must be equal to 4KB and
+			 * page offset is zero.
+			 */
+			off_srcs[count] = dev->offset;
+			xor_srcs[count++] = dev->orig_page;
+		} else if (test_bit(R5_Wantdrain, &dev->flags)) {
+			off_srcs[count] = dev->offset;
+			xor_srcs[count++] = dev->page;
+		}
+	}
+
+	init_async_submit(&submit, ASYNC_TX_FENCE|ASYNC_TX_XOR_DROP_DST, tx,
+			  ops_complete_prexor, sh, to_addr_conv(sh, percpu, 0));
+	tx = async_xor_offs(xor_dest, off_dest, xor_srcs, off_srcs, count,
+			RAID5_STRIPE_SIZE(sh->raid_conf), &submit);
+
+	return tx;
+}
+
+static struct dma_async_tx_descriptor *
+ops_run_prexor6(struct stripe_head *sh, struct raid5_percpu *percpu,
+		struct dma_async_tx_descriptor *tx)
+{
+	struct page **blocks = to_addr_page(percpu, 0);
+	unsigned int *offs = to_addr_offs(sh, percpu);
+	int count;
+	struct async_submit_ctl submit;
+
+	pr_debug("%s: stripe %llu\n", __func__,
+		(unsigned long long)sh->sector);
+
+	count = set_syndrome_sources(blocks, offs, sh, SYNDROME_SRC_WANT_DRAIN);
+
+	init_async_submit(&submit, ASYNC_TX_FENCE|ASYNC_TX_PQ_XOR_DST, tx,
+			  ops_complete_prexor, sh, to_addr_conv(sh, percpu, 0));
+	tx = async_gen_syndrome(blocks, offs, count+2,
+			RAID5_STRIPE_SIZE(sh->raid_conf), &submit);
+
+	return tx;
+}
+
+static struct dma_async_tx_descriptor *
+ops_run_biodrain(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
+{
+	struct r5conf *conf = sh->raid_conf;
+	int disks = sh->disks;
+	int i;
+	struct stripe_head *head_sh = sh;
+
+	pr_debug("%s: stripe %llu\n", __func__,
+		(unsigned long long)sh->sector);
+
+	for (i = disks; i--; ) {
+		struct r5dev *dev;
+		struct bio *chosen;
+
+		sh = head_sh;
+		if (test_and_clear_bit(R5_Wantdrain, &head_sh->dev[i].flags)) {
+			struct bio *wbi;
+
+again:
+			dev = &sh->dev[i];
+			/*
+			 * clear R5_InJournal, so when rewriting a page in
+			 * journal, it is not skipped by r5l_log_stripe()
+			 */
+			clear_bit(R5_InJournal, &dev->flags);
+			spin_lock_irq(&sh->stripe_lock);
+			chosen = dev->towrite;
+			dev->towrite = NULL;
+			sh->overwrite_disks = 0;
+			BUG_ON(dev->written);
+			wbi = dev->written = chosen;
+			spin_unlock_irq(&sh->stripe_lock);
+			WARN_ON(dev->page != dev->orig_page);
+
+			while (wbi && wbi->bi_iter.bi_sector <
+				dev->sector + RAID5_STRIPE_SECTORS(conf)) {
+				if (wbi->bi_opf & REQ_FUA)
+					set_bit(R5_WantFUA, &dev->flags);
+				if (wbi->bi_opf & REQ_SYNC)
+					set_bit(R5_SyncIO, &dev->flags);
+				if (bio_op(wbi) == REQ_OP_DISCARD)
+					set_bit(R5_Discard, &dev->flags);
+				else {
+					tx = async_copy_data(1, wbi, &dev->page,
+							     dev->offset,
+							     dev->sector, tx, sh,
+							     r5c_is_writeback(conf->log));
+					if (dev->page != dev->orig_page &&
+					    !r5c_is_writeback(conf->log)) {
+						set_bit(R5_SkipCopy, &dev->flags);
+						clear_bit(R5_UPTODATE, &dev->flags);
+						clear_bit(R5_OVERWRITE, &dev->flags);
+					}
+				}
+				wbi = r5_next_bio(conf, wbi, dev->sector);
+			}
+
+			if (head_sh->batch_head) {
+				sh = list_first_entry(&sh->batch_list,
+						      struct stripe_head,
+						      batch_list);
+				if (sh == head_sh)
+					continue;
+				goto again;
+			}
+		}
+	}
+
+	return tx;
+}
+
+static void ops_complete_reconstruct(void *stripe_head_ref)
+{
+	struct stripe_head *sh = stripe_head_ref;
+	int disks = sh->disks;
+	int pd_idx = sh->pd_idx;
+	int qd_idx = sh->qd_idx;
+	int i;
+	bool fua = false, sync = false, discard = false;
+
+	pr_debug("%s: stripe %llu\n", __func__,
+		(unsigned long long)sh->sector);
+
+	for (i = disks; i--; ) {
+		fua |= test_bit(R5_WantFUA, &sh->dev[i].flags);
+		sync |= test_bit(R5_SyncIO, &sh->dev[i].flags);
+		discard |= test_bit(R5_Discard, &sh->dev[i].flags);
+	}
+
+	for (i = disks; i--; ) {
+		struct r5dev *dev = &sh->dev[i];
+
+		if (dev->written || i == pd_idx || i == qd_idx) {
+			if (!discard && !test_bit(R5_SkipCopy, &dev->flags)) {
+				set_bit(R5_UPTODATE, &dev->flags);
+				if (test_bit(STRIPE_EXPAND_READY, &sh->state))
+					set_bit(R5_Expanded, &dev->flags);
+			}
+			if (fua)
+				set_bit(R5_WantFUA, &dev->flags);
+			if (sync)
+				set_bit(R5_SyncIO, &dev->flags);
+		}
+	}
+
+	if (sh->reconstruct_state == reconstruct_state_drain_run)
+		sh->reconstruct_state = reconstruct_state_drain_result;
+	else if (sh->reconstruct_state == reconstruct_state_prexor_drain_run)
+		sh->reconstruct_state = reconstruct_state_prexor_drain_result;
+	else {
+		BUG_ON(sh->reconstruct_state != reconstruct_state_run);
+		sh->reconstruct_state = reconstruct_state_result;
+	}
+
+	set_bit(STRIPE_HANDLE, &sh->state);
+	raid5_release_stripe(sh);
+}
+
+static void
+ops_run_reconstruct5(struct stripe_head *sh, struct raid5_percpu *percpu,
+		     struct dma_async_tx_descriptor *tx)
+{
+	int disks = sh->disks;
+	struct page **xor_srcs;
+	unsigned int *off_srcs;
+	struct async_submit_ctl submit;
+	int count, pd_idx = sh->pd_idx, i;
+	struct page *xor_dest;
+	unsigned int off_dest;
+	int prexor = 0;
+	unsigned long flags;
+	int j = 0;
+	struct stripe_head *head_sh = sh;
+	int last_stripe;
+
+	pr_debug("%s: stripe %llu\n", __func__,
+		(unsigned long long)sh->sector);
+
+	for (i = 0; i < sh->disks; i++) {
+		if (pd_idx == i)
+			continue;
+		if (!test_bit(R5_Discard, &sh->dev[i].flags))
+			break;
+	}
+	if (i >= sh->disks) {
+		atomic_inc(&sh->count);
+		set_bit(R5_Discard, &sh->dev[pd_idx].flags);
+		ops_complete_reconstruct(sh);
+		return;
+	}
+again:
+	count = 0;
+	xor_srcs = to_addr_page(percpu, j);
+	off_srcs = to_addr_offs(sh, percpu);
+	/* check if prexor is active which means only process blocks
+	 * that are part of a read-modify-write (written)
+	 */
+	if (head_sh->reconstruct_state == reconstruct_state_prexor_drain_run) {
+		prexor = 1;
+		off_dest = off_srcs[count] = sh->dev[pd_idx].offset;
+		xor_dest = xor_srcs[count++] = sh->dev[pd_idx].page;
+		for (i = disks; i--; ) {
+			struct r5dev *dev = &sh->dev[i];
+			if (head_sh->dev[i].written ||
+			    test_bit(R5_InJournal, &head_sh->dev[i].flags)) {
+				off_srcs[count] = dev->offset;
+				xor_srcs[count++] = dev->page;
+			}
+		}
+	} else {
+		xor_dest = sh->dev[pd_idx].page;
+		off_dest = sh->dev[pd_idx].offset;
+		for (i = disks; i--; ) {
+			struct r5dev *dev = &sh->dev[i];
+			if (i != pd_idx) {
+				off_srcs[count] = dev->offset;
+				xor_srcs[count++] = dev->page;
+			}
+		}
+	}
+
+	/* 1/ if we prexor'd then the dest is reused as a source
+	 * 2/ if we did not prexor then we are redoing the parity
+	 * set ASYNC_TX_XOR_DROP_DST and ASYNC_TX_XOR_ZERO_DST
+	 * for the synchronous xor case
+	 */
+	last_stripe = !head_sh->batch_head ||
+		list_first_entry(&sh->batch_list,
+				 struct stripe_head, batch_list) == head_sh;
+	if (last_stripe) {
+		flags = ASYNC_TX_ACK |
+			(prexor ? ASYNC_TX_XOR_DROP_DST : ASYNC_TX_XOR_ZERO_DST);
+
+		atomic_inc(&head_sh->count);
+		init_async_submit(&submit, flags, tx, ops_complete_reconstruct, head_sh,
+				  to_addr_conv(sh, percpu, j));
+	} else {
+		flags = prexor ? ASYNC_TX_XOR_DROP_DST : ASYNC_TX_XOR_ZERO_DST;
+		init_async_submit(&submit, flags, tx, NULL, NULL,
+				  to_addr_conv(sh, percpu, j));
+	}
+
+	if (unlikely(count == 1))
+		tx = async_memcpy(xor_dest, xor_srcs[0], off_dest, off_srcs[0],
+				RAID5_STRIPE_SIZE(sh->raid_conf), &submit);
+	else
+		tx = async_xor_offs(xor_dest, off_dest, xor_srcs, off_srcs, count,
+				RAID5_STRIPE_SIZE(sh->raid_conf), &submit);
+	if (!last_stripe) {
+		j++;
+		sh = list_first_entry(&sh->batch_list, struct stripe_head,
+				      batch_list);
+		goto again;
+	}
+}
+
+static void
+ops_run_reconstruct6(struct stripe_head *sh, struct raid5_percpu *percpu,
+		     struct dma_async_tx_descriptor *tx)
+{
+	struct async_submit_ctl submit;
+	struct page **blocks;
+	unsigned int *offs;
+	int count, i, j = 0;
+	struct stripe_head *head_sh = sh;
+	int last_stripe;
+	int synflags;
+	unsigned long txflags;
+
+	pr_debug("%s: stripe %llu\n", __func__, (unsigned long long)sh->sector);
+
+	for (i = 0; i < sh->disks; i++) {
+		if (sh->pd_idx == i || sh->qd_idx == i)
+			continue;
+		if (!test_bit(R5_Discard, &sh->dev[i].flags))
+			break;
+	}
+	if (i >= sh->disks) {
+		atomic_inc(&sh->count);
+		set_bit(R5_Discard, &sh->dev[sh->pd_idx].flags);
+		set_bit(R5_Discard, &sh->dev[sh->qd_idx].flags);
+		ops_complete_reconstruct(sh);
+		return;
+	}
+
+again:
+	blocks = to_addr_page(percpu, j);
+	offs = to_addr_offs(sh, percpu);
+
+	if (sh->reconstruct_state == reconstruct_state_prexor_drain_run) {
+		synflags = SYNDROME_SRC_WRITTEN;
+		txflags = ASYNC_TX_ACK | ASYNC_TX_PQ_XOR_DST;
+	} else {
+		synflags = SYNDROME_SRC_ALL;
+		txflags = ASYNC_TX_ACK;
+	}
+
+	count = set_syndrome_sources(blocks, offs, sh, synflags);
+	last_stripe = !head_sh->batch_head ||
+		list_first_entry(&sh->batch_list,
+				 struct stripe_head, batch_list) == head_sh;
+
+	if (last_stripe) {
+		atomic_inc(&head_sh->count);
+		init_async_submit(&submit, txflags, tx, ops_complete_reconstruct,
+				  head_sh, to_addr_conv(sh, percpu, j));
+	} else
+		init_async_submit(&submit, 0, tx, NULL, NULL,
+				  to_addr_conv(sh, percpu, j));
+	tx = async_gen_syndrome(blocks, offs, count+2,
+			RAID5_STRIPE_SIZE(sh->raid_conf),  &submit);
+	if (!last_stripe) {
+		j++;
+		sh = list_first_entry(&sh->batch_list, struct stripe_head,
+				      batch_list);
+		goto again;
+	}
+}
+
+static void ops_complete_check(void *stripe_head_ref)
+{
+	struct stripe_head *sh = stripe_head_ref;
+
+	pr_debug("%s: stripe %llu\n", __func__,
+		(unsigned long long)sh->sector);
+
+	sh->check_state = check_state_check_result;
+	set_bit(STRIPE_HANDLE, &sh->state);
+	raid5_release_stripe(sh);
+}
+
+static void ops_run_check_p(struct stripe_head *sh, struct raid5_percpu *percpu)
+{
+	int disks = sh->disks;
+	int pd_idx = sh->pd_idx;
+	int qd_idx = sh->qd_idx;
+	struct page *xor_dest;
+	unsigned int off_dest;
+	struct page **xor_srcs = to_addr_page(percpu, 0);
+	unsigned int *off_srcs = to_addr_offs(sh, percpu);
+	struct dma_async_tx_descriptor *tx;
+	struct async_submit_ctl submit;
+	int count;
+	int i;
+
+	pr_debug("%s: stripe %llu\n", __func__,
+		(unsigned long long)sh->sector);
+
+	BUG_ON(sh->batch_head);
+	count = 0;
+	xor_dest = sh->dev[pd_idx].page;
+	off_dest = sh->dev[pd_idx].offset;
+	off_srcs[count] = off_dest;
+	xor_srcs[count++] = xor_dest;
+	for (i = disks; i--; ) {
+		if (i == pd_idx || i == qd_idx)
+			continue;
+		off_srcs[count] = sh->dev[i].offset;
+		xor_srcs[count++] = sh->dev[i].page;
+	}
+
+	init_async_submit(&submit, 0, NULL, NULL, NULL,
+			  to_addr_conv(sh, percpu, 0));
+	tx = async_xor_val_offs(xor_dest, off_dest, xor_srcs, off_srcs, count,
+			   RAID5_STRIPE_SIZE(sh->raid_conf),
+			   &sh->ops.zero_sum_result, &submit);
+
+	atomic_inc(&sh->count);
+	init_async_submit(&submit, ASYNC_TX_ACK, tx, ops_complete_check, sh, NULL);
+	tx = async_trigger_callback(&submit);
+}
+
+static void ops_run_check_pq(struct stripe_head *sh, struct raid5_percpu *percpu, int checkp)
+{
+	struct page **srcs = to_addr_page(percpu, 0);
+	unsigned int *offs = to_addr_offs(sh, percpu);
+	struct async_submit_ctl submit;
+	int count;
+
+	pr_debug("%s: stripe %llu checkp: %d\n", __func__,
+		(unsigned long long)sh->sector, checkp);
+
+	BUG_ON(sh->batch_head);
+	count = set_syndrome_sources(srcs, offs, sh, SYNDROME_SRC_ALL);
+	if (!checkp)
+		srcs[count] = NULL;
+
+	atomic_inc(&sh->count);
+	init_async_submit(&submit, ASYNC_TX_ACK, NULL, ops_complete_check,
+			  sh, to_addr_conv(sh, percpu, 0));
+	async_syndrome_val(srcs, offs, count+2,
+			   RAID5_STRIPE_SIZE(sh->raid_conf),
+			   &sh->ops.zero_sum_result, percpu->spare_page, 0, &submit);
+}
+
+static void raid_run_ops(struct stripe_head *sh, unsigned long ops_request)
+{
+	int overlap_clear = 0, i, disks = sh->disks;
+	struct dma_async_tx_descriptor *tx = NULL;
+	struct r5conf *conf = sh->raid_conf;
+	int level = conf->level;
+	struct raid5_percpu *percpu;
+
+	local_lock(&conf->percpu->lock);
+	percpu = this_cpu_ptr(conf->percpu);
+	if (test_bit(STRIPE_OP_BIOFILL, &ops_request)) {
+		ops_run_biofill(sh);
+		overlap_clear++;
+	}
+
+	if (test_bit(STRIPE_OP_COMPUTE_BLK, &ops_request)) {
+		if (level < 6)
+			tx = ops_run_compute5(sh, percpu);
+		else {
+			if (sh->ops.target2 < 0 || sh->ops.target < 0)
+				tx = ops_run_compute6_1(sh, percpu);
+			else
+				tx = ops_run_compute6_2(sh, percpu);
+		}
+		/* terminate the chain if reconstruct is not set to be run */
+		if (tx && !test_bit(STRIPE_OP_RECONSTRUCT, &ops_request))
+			async_tx_ack(tx);
+	}
+
+	if (test_bit(STRIPE_OP_PREXOR, &ops_request)) {
+		if (level < 6)
+			tx = ops_run_prexor5(sh, percpu, tx);
+		else
+			tx = ops_run_prexor6(sh, percpu, tx);
+	}
+
+	if (test_bit(STRIPE_OP_PARTIAL_PARITY, &ops_request))
+		tx = ops_run_partial_parity(sh, percpu, tx);
+
+	if (test_bit(STRIPE_OP_BIODRAIN, &ops_request)) {
+		tx = ops_run_biodrain(sh, tx);
+		overlap_clear++;
+	}
+
+	if (test_bit(STRIPE_OP_RECONSTRUCT, &ops_request)) {
+		if (level < 6)
+			ops_run_reconstruct5(sh, percpu, tx);
+		else
+			ops_run_reconstruct6(sh, percpu, tx);
+	}
+
+	if (test_bit(STRIPE_OP_CHECK, &ops_request)) {
+		if (sh->check_state == check_state_run)
+			ops_run_check_p(sh, percpu);
+		else if (sh->check_state == check_state_run_q)
+			ops_run_check_pq(sh, percpu, 0);
+		else if (sh->check_state == check_state_run_pq)
+			ops_run_check_pq(sh, percpu, 1);
+		else
+			BUG();
+	}
+
+	if (overlap_clear && !sh->batch_head) {
+		for (i = disks; i--; ) {
+			struct r5dev *dev = &sh->dev[i];
+			if (test_and_clear_bit(R5_Overlap, &dev->flags))
+				wake_up(&sh->raid_conf->wait_for_overlap);
+		}
+	}
+	local_unlock(&conf->percpu->lock);
+}
+
+static void free_stripe(struct kmem_cache *sc, struct stripe_head *sh)
+{
+#if PAGE_SIZE != DEFAULT_STRIPE_SIZE
+	kfree(sh->pages);
+#endif
+	if (sh->ppl_page)
+		__free_page(sh->ppl_page);
+	kmem_cache_free(sc, sh);
+}
+
+static struct stripe_head *alloc_stripe(struct kmem_cache *sc, gfp_t gfp,
+	int disks, struct r5conf *conf)
+{
+	struct stripe_head *sh;
+
+	sh = kmem_cache_zalloc(sc, gfp);
+	if (sh) {
+		spin_lock_init(&sh->stripe_lock);
+		spin_lock_init(&sh->batch_lock);
+		INIT_LIST_HEAD(&sh->batch_list);
+		INIT_LIST_HEAD(&sh->lru);
+		INIT_LIST_HEAD(&sh->r5c);
+		INIT_LIST_HEAD(&sh->log_list);
+		atomic_set(&sh->count, 1);
+		sh->raid_conf = conf;
+		sh->log_start = MaxSector;
+
+		if (raid5_has_ppl(conf)) {
+			sh->ppl_page = alloc_page(gfp);
+			if (!sh->ppl_page) {
+				free_stripe(sc, sh);
+				return NULL;
+			}
+		}
+#if PAGE_SIZE != DEFAULT_STRIPE_SIZE
+		if (init_stripe_shared_pages(sh, conf, disks)) {
+			free_stripe(sc, sh);
+			return NULL;
+		}
+#endif
+	}
+	return sh;
+}
+static int grow_one_stripe(struct r5conf *conf, gfp_t gfp)
+{
+	struct stripe_head *sh;
+
+	sh = alloc_stripe(conf->slab_cache, gfp, conf->pool_size, conf);
+	if (!sh)
+		return 0;
+
+	if (grow_buffers(sh, gfp)) {
+		shrink_buffers(sh);
+		free_stripe(conf->slab_cache, sh);
+		return 0;
+	}
+	sh->hash_lock_index =
+		conf->max_nr_stripes % NR_STRIPE_HASH_LOCKS;
+	/* we just created an active stripe so... */
+	atomic_inc(&conf->active_stripes);
+
+	raid5_release_stripe(sh);
+	conf->max_nr_stripes++;
+	return 1;
+}
+
+static int grow_stripes(struct r5conf *conf, int num)
+{
+	struct kmem_cache *sc;
+	size_t namelen = sizeof(conf->cache_name[0]);
+	int devs = max(conf->raid_disks, conf->previous_raid_disks);
+
+	if (conf->mddev->gendisk)
+		snprintf(conf->cache_name[0], namelen,
+			"raid%d-%s", conf->level, mdname(conf->mddev));
+	else
+		snprintf(conf->cache_name[0], namelen,
+			"raid%d-%p", conf->level, conf->mddev);
+	snprintf(conf->cache_name[1], namelen, "%.27s-alt", conf->cache_name[0]);
+
+	conf->active_name = 0;
+	sc = kmem_cache_create(conf->cache_name[conf->active_name],
+			       struct_size_t(struct stripe_head, dev, devs),
+			       0, 0, NULL);
+	if (!sc)
+		return 1;
+	conf->slab_cache = sc;
+	conf->pool_size = devs;
+	while (num--)
+		if (!grow_one_stripe(conf, GFP_KERNEL))
+			return 1;
+
+	return 0;
+}
+
+/**
+ * scribble_alloc - allocate percpu scribble buffer for required size
+ *		    of the scribble region
+ * @percpu: from for_each_present_cpu() of the caller
+ * @num: total number of disks in the array
+ * @cnt: scribble objs count for required size of the scribble region
+ *
+ * The scribble buffer size must be enough to contain:
+ * 1/ a struct page pointer for each device in the array +2
+ * 2/ room to convert each entry in (1) to its corresponding dma
+ *    (dma_map_page()) or page (page_address()) address.
+ *
+ * Note: the +2 is for the destination buffers of the ddf/raid6 case where we
+ * calculate over all devices (not just the data blocks), using zeros in place
+ * of the P and Q blocks.
+ */
+static int scribble_alloc(struct raid5_percpu *percpu,
+			  int num, int cnt)
+{
+	size_t obj_size =
+		sizeof(struct page *) * (num + 2) +
+		sizeof(addr_conv_t) * (num + 2) +
+		sizeof(unsigned int) * (num + 2);
+	void *scribble;
+
+	/*
+	 * If here is in raid array suspend context, it is in memalloc noio
+	 * context as well, there is no potential recursive memory reclaim
+	 * I/Os with the GFP_KERNEL flag.
+	 */
+	scribble = kvmalloc_array(cnt, obj_size, GFP_KERNEL);
+	if (!scribble)
+		return -ENOMEM;
+
+	kvfree(percpu->scribble);
+
+	percpu->scribble = scribble;
+	percpu->scribble_obj_size = obj_size;
+	return 0;
+}
+
+static int resize_chunks(struct r5conf *conf, int new_disks, int new_sectors)
+{
+	unsigned long cpu;
+	int err = 0;
+
+	/*
+	 * Never shrink. And mddev_suspend() could deadlock if this is called
+	 * from raid5d. In that case, scribble_disks and scribble_sectors
+	 * should equal to new_disks and new_sectors
+	 */
+	if (conf->scribble_disks >= new_disks &&
+	    conf->scribble_sectors >= new_sectors)
+		return 0;
+	mddev_suspend(conf->mddev);
+	cpus_read_lock();
+
+	for_each_present_cpu(cpu) {
+		struct raid5_percpu *percpu;
+
+		percpu = per_cpu_ptr(conf->percpu, cpu);
+		err = scribble_alloc(percpu, new_disks,
+				     new_sectors / RAID5_STRIPE_SECTORS(conf));
+		if (err)
+			break;
+	}
+
+	cpus_read_unlock();
+	mddev_resume(conf->mddev);
+	if (!err) {
+		conf->scribble_disks = new_disks;
+		conf->scribble_sectors = new_sectors;
+	}
+	return err;
+}
+
+static int resize_stripes(struct r5conf *conf, int newsize)
+{
+	/* Make all the stripes able to hold 'newsize' devices.
+	 * New slots in each stripe get 'page' set to a new page.
+	 *
+	 * This happens in stages:
+	 * 1/ create a new kmem_cache and allocate the required number of
+	 *    stripe_heads.
+	 * 2/ gather all the old stripe_heads and transfer the pages across
+	 *    to the new stripe_heads.  This will have the side effect of
+	 *    freezing the array as once all stripe_heads have been collected,
+	 *    no IO will be possible.  Old stripe heads are freed once their
+	 *    pages have been transferred over, and the old kmem_cache is
+	 *    freed when all stripes are done.
+	 * 3/ reallocate conf->disks to be suitable bigger.  If this fails,
+	 *    we simple return a failure status - no need to clean anything up.
+	 * 4/ allocate new pages for the new slots in the new stripe_heads.
+	 *    If this fails, we don't bother trying the shrink the
+	 *    stripe_heads down again, we just leave them as they are.
+	 *    As each stripe_head is processed the new one is released into
+	 *    active service.
+	 *
+	 * Once step2 is started, we cannot afford to wait for a write,
+	 * so we use GFP_NOIO allocations.
+	 */
+	struct stripe_head *osh, *nsh;
+	LIST_HEAD(newstripes);
+	struct disk_info *ndisks;
+	int err = 0;
+	struct kmem_cache *sc;
+	int i;
+	int hash, cnt;
+
+	md_allow_write(conf->mddev);
+
+	/* Step 1 */
+	sc = kmem_cache_create(conf->cache_name[1-conf->active_name],
+			       struct_size_t(struct stripe_head, dev, newsize),
+			       0, 0, NULL);
+	if (!sc)
+		return -ENOMEM;
+
+	/* Need to ensure auto-resizing doesn't interfere */
+	mutex_lock(&conf->cache_size_mutex);
+
+	for (i = conf->max_nr_stripes; i; i--) {
+		nsh = alloc_stripe(sc, GFP_KERNEL, newsize, conf);
+		if (!nsh)
+			break;
+
+		list_add(&nsh->lru, &newstripes);
+	}
+	if (i) {
+		/* didn't get enough, give up */
+		while (!list_empty(&newstripes)) {
+			nsh = list_entry(newstripes.next, struct stripe_head, lru);
+			list_del(&nsh->lru);
+			free_stripe(sc, nsh);
+		}
+		kmem_cache_destroy(sc);
+		mutex_unlock(&conf->cache_size_mutex);
+		return -ENOMEM;
+	}
+	/* Step 2 - Must use GFP_NOIO now.
+	 * OK, we have enough stripes, start collecting inactive
+	 * stripes and copying them over
+	 */
+	hash = 0;
+	cnt = 0;
+	list_for_each_entry(nsh, &newstripes, lru) {
+		lock_device_hash_lock(conf, hash);
+		wait_event_cmd(conf->wait_for_stripe,
+				    !list_empty(conf->inactive_list + hash),
+				    unlock_device_hash_lock(conf, hash),
+				    lock_device_hash_lock(conf, hash));
+		osh = get_free_stripe(conf, hash);
+		unlock_device_hash_lock(conf, hash);
+
+#if PAGE_SIZE != DEFAULT_STRIPE_SIZE
+	for (i = 0; i < osh->nr_pages; i++) {
+		nsh->pages[i] = osh->pages[i];
+		osh->pages[i] = NULL;
+	}
+#endif
+		for(i=0; i<conf->pool_size; i++) {
+			nsh->dev[i].page = osh->dev[i].page;
+			nsh->dev[i].orig_page = osh->dev[i].page;
+			nsh->dev[i].offset = osh->dev[i].offset;
+		}
+		nsh->hash_lock_index = hash;
+		free_stripe(conf->slab_cache, osh);
+		cnt++;
+		if (cnt >= conf->max_nr_stripes / NR_STRIPE_HASH_LOCKS +
+		    !!((conf->max_nr_stripes % NR_STRIPE_HASH_LOCKS) > hash)) {
+			hash++;
+			cnt = 0;
+		}
+	}
+	kmem_cache_destroy(conf->slab_cache);
+
+	/* Step 3.
+	 * At this point, we are holding all the stripes so the array
+	 * is completely stalled, so now is a good time to resize
+	 * conf->disks and the scribble region
+	 */
+	ndisks = kcalloc(newsize, sizeof(struct disk_info), GFP_NOIO);
+	if (ndisks) {
+		for (i = 0; i < conf->pool_size; i++)
+			ndisks[i] = conf->disks[i];
+
+		for (i = conf->pool_size; i < newsize; i++) {
+			ndisks[i].extra_page = alloc_page(GFP_NOIO);
+			if (!ndisks[i].extra_page)
+				err = -ENOMEM;
+		}
+
+		if (err) {
+			for (i = conf->pool_size; i < newsize; i++)
+				if (ndisks[i].extra_page)
+					put_page(ndisks[i].extra_page);
+			kfree(ndisks);
+		} else {
+			kfree(conf->disks);
+			conf->disks = ndisks;
+		}
+	} else
+		err = -ENOMEM;
+
+	conf->slab_cache = sc;
+	conf->active_name = 1-conf->active_name;
+
+	/* Step 4, return new stripes to service */
+	while(!list_empty(&newstripes)) {
+		nsh = list_entry(newstripes.next, struct stripe_head, lru);
+		list_del_init(&nsh->lru);
+
+#if PAGE_SIZE != DEFAULT_STRIPE_SIZE
+		for (i = 0; i < nsh->nr_pages; i++) {
+			if (nsh->pages[i])
+				continue;
+			nsh->pages[i] = alloc_page(GFP_NOIO);
+			if (!nsh->pages[i])
+				err = -ENOMEM;
+		}
+
+		for (i = conf->raid_disks; i < newsize; i++) {
+			if (nsh->dev[i].page)
+				continue;
+			nsh->dev[i].page = raid5_get_dev_page(nsh, i);
+			nsh->dev[i].orig_page = nsh->dev[i].page;
+			nsh->dev[i].offset = raid5_get_page_offset(nsh, i);
+		}
+#else
+		for (i=conf->raid_disks; i < newsize; i++)
+			if (nsh->dev[i].page == NULL) {
+				struct page *p = alloc_page(GFP_NOIO);
+				nsh->dev[i].page = p;
+				nsh->dev[i].orig_page = p;
+				nsh->dev[i].offset = 0;
+				if (!p)
+					err = -ENOMEM;
+			}
+#endif
+		raid5_release_stripe(nsh);
+	}
+	/* critical section pass, GFP_NOIO no longer needed */
+
+	if (!err)
+		conf->pool_size = newsize;
+	mutex_unlock(&conf->cache_size_mutex);
+
+	return err;
+}
+
+static int drop_one_stripe(struct r5conf *conf)
+{
+	struct stripe_head *sh;
+	int hash = (conf->max_nr_stripes - 1) & STRIPE_HASH_LOCKS_MASK;
+
+	spin_lock_irq(conf->hash_locks + hash);
+	sh = get_free_stripe(conf, hash);
+	spin_unlock_irq(conf->hash_locks + hash);
+	if (!sh)
+		return 0;
+	BUG_ON(atomic_read(&sh->count));
+	shrink_buffers(sh);
+	free_stripe(conf->slab_cache, sh);
+	atomic_dec(&conf->active_stripes);
+	conf->max_nr_stripes--;
+	return 1;
+}
+
+static void shrink_stripes(struct r5conf *conf)
+{
+	while (conf->max_nr_stripes &&
+	       drop_one_stripe(conf))
+		;
+
+	kmem_cache_destroy(conf->slab_cache);
+	conf->slab_cache = NULL;
+}
+
+/*
+ * This helper wraps rcu_dereference_protected() and can be used when
+ * it is known that the nr_pending of the rdev is elevated.
+ */
+static struct md_rdev *rdev_pend_deref(struct md_rdev __rcu *rdev)
+{
+	return rcu_dereference_protected(rdev,
+			atomic_read(&rcu_access_pointer(rdev)->nr_pending));
+}
+
+/*
+ * This helper wraps rcu_dereference_protected() and should be used
+ * when it is known that the mddev_lock() is held. This is safe
+ * seeing raid5_remove_disk() has the same lock held.
+ */
+static struct md_rdev *rdev_mdlock_deref(struct mddev *mddev,
+					 struct md_rdev __rcu *rdev)
+{
+	return rcu_dereference_protected(rdev,
+			lockdep_is_held(&mddev->reconfig_mutex));
+}
+
+static void raid5_end_read_request(struct bio * bi)
+{
+	struct stripe_head *sh = bi->bi_private;
+	struct r5conf *conf = sh->raid_conf;
+	int disks = sh->disks, i;
+	struct md_rdev *rdev = NULL;
+	sector_t s;
+
+	for (i=0 ; i<disks; i++)
+		if (bi == &sh->dev[i].req)
+			break;
+
+	pr_debug("end_read_request %llu/%d, count: %d, error %d.\n",
+		(unsigned long long)sh->sector, i, atomic_read(&sh->count),
+		bi->bi_status);
+	if (i == disks) {
+		BUG();
+		return;
+	}
+	if (test_bit(R5_ReadRepl, &sh->dev[i].flags))
+		/* If replacement finished while this request was outstanding,
+		 * 'replacement' might be NULL already.
+		 * In that case it moved down to 'rdev'.
+		 * rdev is not removed until all requests are finished.
+		 */
+		rdev = rdev_pend_deref(conf->disks[i].replacement);
+	if (!rdev)
+		rdev = rdev_pend_deref(conf->disks[i].rdev);
+
+	if (use_new_offset(conf, sh))
+		s = sh->sector + rdev->new_data_offset;
+	else
+		s = sh->sector + rdev->data_offset;
+	if (!bi->bi_status) {
+		set_bit(R5_UPTODATE, &sh->dev[i].flags);
+		if (test_bit(R5_ReadError, &sh->dev[i].flags)) {
+			/* Note that this cannot happen on a
+			 * replacement device.  We just fail those on
+			 * any error
+			 */
+			pr_info_ratelimited(
+				"md/raid:%s: read error corrected (%lu sectors at %llu on %pg)\n",
+				mdname(conf->mddev), RAID5_STRIPE_SECTORS(conf),
+				(unsigned long long)s,
+				rdev->bdev);
+			atomic_add(RAID5_STRIPE_SECTORS(conf), &rdev->corrected_errors);
+			clear_bit(R5_ReadError, &sh->dev[i].flags);
+			clear_bit(R5_ReWrite, &sh->dev[i].flags);
+		} else if (test_bit(R5_ReadNoMerge, &sh->dev[i].flags))
+			clear_bit(R5_ReadNoMerge, &sh->dev[i].flags);
+
+		if (test_bit(R5_InJournal, &sh->dev[i].flags))
+			/*
+			 * end read for a page in journal, this
+			 * must be preparing for prexor in rmw
+			 */
+			set_bit(R5_OrigPageUPTDODATE, &sh->dev[i].flags);
+
+		if (atomic_read(&rdev->read_errors))
+			atomic_set(&rdev->read_errors, 0);
+	} else {
+		int retry = 0;
+		int set_bad = 0;
+
+		clear_bit(R5_UPTODATE, &sh->dev[i].flags);
+		if (!(bi->bi_status == BLK_STS_PROTECTION))
+			atomic_inc(&rdev->read_errors);
+		if (test_bit(R5_ReadRepl, &sh->dev[i].flags))
+			pr_warn_ratelimited(
+				"md/raid:%s: read error on replacement device (sector %llu on %pg).\n",
+				mdname(conf->mddev),
+				(unsigned long long)s,
+				rdev->bdev);
+		else if (conf->mddev->degraded >= conf->max_degraded) {
+			set_bad = 1;
+			pr_warn_ratelimited(
+				"md/raid:%s: read error not correctable (sector %llu on %pg).\n",
+				mdname(conf->mddev),
+				(unsigned long long)s,
+				rdev->bdev);
+		} else if (test_bit(R5_ReWrite, &sh->dev[i].flags)) {
+			/* Oh, no!!! */
+			set_bad = 1;
+			pr_warn_ratelimited(
+				"md/raid:%s: read error NOT corrected!! (sector %llu on %pg).\n",
+				mdname(conf->mddev),
+				(unsigned long long)s,
+				rdev->bdev);
+		} else if (atomic_read(&rdev->read_errors)
+			 > conf->max_nr_stripes) {
+			if (!test_bit(Faulty, &rdev->flags)) {
+				pr_warn("md/raid:%s: %d read_errors > %d stripes\n",
+				    mdname(conf->mddev),
+				    atomic_read(&rdev->read_errors),
+				    conf->max_nr_stripes);
+				pr_warn("md/raid:%s: Too many read errors, failing device %pg.\n",
+				    mdname(conf->mddev), rdev->bdev);
+			}
+		} else
+			retry = 1;
+		if (set_bad && test_bit(In_sync, &rdev->flags)
+		    && !test_bit(R5_ReadNoMerge, &sh->dev[i].flags))
+			retry = 1;
+		if (retry)
+			if (sh->qd_idx >= 0 && sh->pd_idx == i)
+				set_bit(R5_ReadError, &sh->dev[i].flags);
+			else if (test_bit(R5_ReadNoMerge, &sh->dev[i].flags)) {
+				set_bit(R5_ReadError, &sh->dev[i].flags);
+				clear_bit(R5_ReadNoMerge, &sh->dev[i].flags);
+			} else
+				set_bit(R5_ReadNoMerge, &sh->dev[i].flags);
+		else {
+			clear_bit(R5_ReadError, &sh->dev[i].flags);
+			clear_bit(R5_ReWrite, &sh->dev[i].flags);
+			if (!(set_bad
+			      && test_bit(In_sync, &rdev->flags)
+			      && rdev_set_badblocks(
+				      rdev, sh->sector, RAID5_STRIPE_SECTORS(conf), 0)))
+				md_error(conf->mddev, rdev);
+		}
+	}
+	rdev_dec_pending(rdev, conf->mddev);
+	bio_uninit(bi);
+	clear_bit(R5_LOCKED, &sh->dev[i].flags);
+	set_bit(STRIPE_HANDLE, &sh->state);
+	raid5_release_stripe(sh);
+}
+
+static void raid5_end_write_request(struct bio *bi)
+{
+	struct stripe_head *sh = bi->bi_private;
+	struct r5conf *conf = sh->raid_conf;
+	int disks = sh->disks, i;
+	struct md_rdev *rdev;
+	sector_t first_bad;
+	int bad_sectors;
+	int replacement = 0;
+
+	for (i = 0 ; i < disks; i++) {
+		if (bi == &sh->dev[i].req) {
+			rdev = rdev_pend_deref(conf->disks[i].rdev);
+			break;
+		}
+		if (bi == &sh->dev[i].rreq) {
+			rdev = rdev_pend_deref(conf->disks[i].replacement);
+			if (rdev)
+				replacement = 1;
+			else
+				/* rdev was removed and 'replacement'
+				 * replaced it.  rdev is not removed
+				 * until all requests are finished.
+				 */
+				rdev = rdev_pend_deref(conf->disks[i].rdev);
+			break;
+		}
+	}
+	pr_debug("end_write_request %llu/%d, count %d, error: %d.\n",
+		(unsigned long long)sh->sector, i, atomic_read(&sh->count),
+		bi->bi_status);
+	if (i == disks) {
+		BUG();
+		return;
+	}
+
+	if (replacement) {
+		if (bi->bi_status)
+			md_error(conf->mddev, rdev);
+		else if (is_badblock(rdev, sh->sector,
+				     RAID5_STRIPE_SECTORS(conf),
+				     &first_bad, &bad_sectors))
+			set_bit(R5_MadeGoodRepl, &sh->dev[i].flags);
+	} else {
+		if (bi->bi_status) {
+			set_bit(STRIPE_DEGRADED, &sh->state);
+			set_bit(WriteErrorSeen, &rdev->flags);
+			set_bit(R5_WriteError, &sh->dev[i].flags);
+			if (!test_and_set_bit(WantReplacement, &rdev->flags))
+				set_bit(MD_RECOVERY_NEEDED,
+					&rdev->mddev->recovery);
+		} else if (is_badblock(rdev, sh->sector,
+				       RAID5_STRIPE_SECTORS(conf),
+				       &first_bad, &bad_sectors)) {
+			set_bit(R5_MadeGood, &sh->dev[i].flags);
+			if (test_bit(R5_ReadError, &sh->dev[i].flags))
+				/* That was a successful write so make
+				 * sure it looks like we already did
+				 * a re-write.
+				 */
+				set_bit(R5_ReWrite, &sh->dev[i].flags);
+		}
+	}
+	rdev_dec_pending(rdev, conf->mddev);
+
+	if (sh->batch_head && bi->bi_status && !replacement)
+		set_bit(STRIPE_BATCH_ERR, &sh->batch_head->state);
+
+	bio_uninit(bi);
+	if (!test_and_clear_bit(R5_DOUBLE_LOCKED, &sh->dev[i].flags))
+		clear_bit(R5_LOCKED, &sh->dev[i].flags);
+	set_bit(STRIPE_HANDLE, &sh->state);
+
+	if (sh->batch_head && sh != sh->batch_head)
+		raid5_release_stripe(sh->batch_head);
+	raid5_release_stripe(sh);
+}
+
+static void raid5_error(struct mddev *mddev, struct md_rdev *rdev)
+{
+	struct r5conf *conf = mddev->private;
+	unsigned long flags;
+	pr_debug("raid456: error called\n");
+
+	pr_crit("md/raid:%s: Disk failure on %pg, disabling device.\n",
+		mdname(mddev), rdev->bdev);
+
+	spin_lock_irqsave(&conf->device_lock, flags);
+	set_bit(Faulty, &rdev->flags);
+	clear_bit(In_sync, &rdev->flags);
+	mddev->degraded = raid5_calc_degraded(conf);
+
+	if (has_failed(conf)) {
+		set_bit(MD_BROKEN, &conf->mddev->flags);
+		conf->recovery_disabled = mddev->recovery_disabled;
+
+		pr_crit("md/raid:%s: Cannot continue operation (%d/%d failed).\n",
+			mdname(mddev), mddev->degraded, conf->raid_disks);
+	} else {
+		pr_crit("md/raid:%s: Operation continuing on %d devices.\n",
+			mdname(mddev), conf->raid_disks - mddev->degraded);
+	}
+
+	spin_unlock_irqrestore(&conf->device_lock, flags);
+	set_bit(MD_RECOVERY_INTR, &mddev->recovery);
+
+	set_bit(Blocked, &rdev->flags);
+	set_mask_bits(&mddev->sb_flags, 0,
+		      BIT(MD_SB_CHANGE_DEVS) | BIT(MD_SB_CHANGE_PENDING));
+	r5c_update_on_rdev_error(mddev, rdev);
+}
+
+/*
+ * Input: a 'big' sector number,
+ * Output: index of the data and parity disk, and the sector # in them.
+ */
+sector_t raid5_compute_sector(struct r5conf *conf, sector_t r_sector,
+			      int previous, int *dd_idx,
+			      struct stripe_head *sh)
+{
+	sector_t stripe, stripe2;
+	sector_t chunk_number;
+	unsigned int chunk_offset;
+	int pd_idx, qd_idx;
+	int ddf_layout = 0;
+	sector_t new_sector;
+	int algorithm = previous ? conf->prev_algo
+				 : conf->algorithm;
+	int sectors_per_chunk = previous ? conf->prev_chunk_sectors
+					 : conf->chunk_sectors;
+	int raid_disks = previous ? conf->previous_raid_disks
+				  : conf->raid_disks;
+	int data_disks = raid_disks - conf->max_degraded;
+
+	/* First compute the information on this sector */
+
+	/*
+	 * Compute the chunk number and the sector offset inside the chunk
+	 */
+	chunk_offset = sector_div(r_sector, sectors_per_chunk);
+	chunk_number = r_sector;
+
+	/*
+	 * Compute the stripe number
+	 */
+	stripe = chunk_number;
+	*dd_idx = sector_div(stripe, data_disks);
+	stripe2 = stripe;
+	/*
+	 * Select the parity disk based on the user selected algorithm.
+	 */
+	pd_idx = qd_idx = -1;
+	switch(conf->level) {
+	case 4:
+		pd_idx = data_disks;
+		break;
+	case 5:
+		switch (algorithm) {
+		case ALGORITHM_LEFT_ASYMMETRIC:
+			pd_idx = data_disks - sector_div(stripe2, raid_disks);
+			if (*dd_idx >= pd_idx)
+				(*dd_idx)++;
+			break;
+		case ALGORITHM_RIGHT_ASYMMETRIC:
+			pd_idx = sector_div(stripe2, raid_disks);
+			if (*dd_idx >= pd_idx)
+				(*dd_idx)++;
+			break;
+		case ALGORITHM_LEFT_SYMMETRIC:
+			pd_idx = data_disks - sector_div(stripe2, raid_disks);
+			*dd_idx = (pd_idx + 1 + *dd_idx) % raid_disks;
+			break;
+		case ALGORITHM_RIGHT_SYMMETRIC:
+			pd_idx = sector_div(stripe2, raid_disks);
+			*dd_idx = (pd_idx + 1 + *dd_idx) % raid_disks;
+			break;
+		case ALGORITHM_PARITY_0:
+			pd_idx = 0;
+			(*dd_idx)++;
+			break;
+		case ALGORITHM_PARITY_N:
+			pd_idx = data_disks;
+			break;
+		default:
+			BUG();
+		}
+		break;
+	case 6:
+
+		switch (algorithm) {
+		case ALGORITHM_LEFT_ASYMMETRIC:
+			pd_idx = raid_disks - 1 - sector_div(stripe2, raid_disks);
+			qd_idx = pd_idx + 1;
+			if (pd_idx == raid_disks-1) {
+				(*dd_idx)++;	/* Q D D D P */
+				qd_idx = 0;
+			} else if (*dd_idx >= pd_idx)
+				(*dd_idx) += 2; /* D D P Q D */
+			break;
+		case ALGORITHM_RIGHT_ASYMMETRIC:
+			pd_idx = sector_div(stripe2, raid_disks);
+			qd_idx = pd_idx + 1;
+			if (pd_idx == raid_disks-1) {
+				(*dd_idx)++;	/* Q D D D P */
+				qd_idx = 0;
+			} else if (*dd_idx >= pd_idx)
+				(*dd_idx) += 2; /* D D P Q D */
+			break;
+		case ALGORITHM_LEFT_SYMMETRIC:
+			pd_idx = raid_disks - 1 - sector_div(stripe2, raid_disks);
+			qd_idx = (pd_idx + 1) % raid_disks;
+			*dd_idx = (pd_idx + 2 + *dd_idx) % raid_disks;
+			break;
+		case ALGORITHM_RIGHT_SYMMETRIC:
+			pd_idx = sector_div(stripe2, raid_disks);
+			qd_idx = (pd_idx + 1) % raid_disks;
+			*dd_idx = (pd_idx + 2 + *dd_idx) % raid_disks;
+			break;
+
+		case ALGORITHM_PARITY_0:
+			pd_idx = 0;
+			qd_idx = 1;
+			(*dd_idx) += 2;
+			break;
+		case ALGORITHM_PARITY_N:
+			pd_idx = data_disks;
+			qd_idx = data_disks + 1;
+			break;
+
+		case ALGORITHM_ROTATING_ZERO_RESTART:
+			/* Exactly the same as RIGHT_ASYMMETRIC, but or
+			 * of blocks for computing Q is different.
+			 */
+			pd_idx = sector_div(stripe2, raid_disks);
+			qd_idx = pd_idx + 1;
+			if (pd_idx == raid_disks-1) {
+				(*dd_idx)++;	/* Q D D D P */
+				qd_idx = 0;
+			} else if (*dd_idx >= pd_idx)
+				(*dd_idx) += 2; /* D D P Q D */
+			ddf_layout = 1;
+			break;
+
+		case ALGORITHM_ROTATING_N_RESTART:
+			/* Same a left_asymmetric, by first stripe is
+			 * D D D P Q  rather than
+			 * Q D D D P
+			 */
+			stripe2 += 1;
+			pd_idx = raid_disks - 1 - sector_div(stripe2, raid_disks);
+			qd_idx = pd_idx + 1;
+			if (pd_idx == raid_disks-1) {
+				(*dd_idx)++;	/* Q D D D P */
+				qd_idx = 0;
+			} else if (*dd_idx >= pd_idx)
+				(*dd_idx) += 2; /* D D P Q D */
+			ddf_layout = 1;
+			break;
+
+		case ALGORITHM_ROTATING_N_CONTINUE:
+			/* Same as left_symmetric but Q is before P */
+			pd_idx = raid_disks - 1 - sector_div(stripe2, raid_disks);
+			qd_idx = (pd_idx + raid_disks - 1) % raid_disks;
+			*dd_idx = (pd_idx + 1 + *dd_idx) % raid_disks;
+			ddf_layout = 1;
+			break;
+
+		case ALGORITHM_LEFT_ASYMMETRIC_6:
+			/* RAID5 left_asymmetric, with Q on last device */
+			pd_idx = data_disks - sector_div(stripe2, raid_disks-1);
+			if (*dd_idx >= pd_idx)
+				(*dd_idx)++;
+			qd_idx = raid_disks - 1;
+			break;
+
+		case ALGORITHM_RIGHT_ASYMMETRIC_6:
+			pd_idx = sector_div(stripe2, raid_disks-1);
+			if (*dd_idx >= pd_idx)
+				(*dd_idx)++;
+			qd_idx = raid_disks - 1;
+			break;
+
+		case ALGORITHM_LEFT_SYMMETRIC_6:
+			pd_idx = data_disks - sector_div(stripe2, raid_disks-1);
+			*dd_idx = (pd_idx + 1 + *dd_idx) % (raid_disks-1);
+			qd_idx = raid_disks - 1;
+			break;
+
+		case ALGORITHM_RIGHT_SYMMETRIC_6:
+			pd_idx = sector_div(stripe2, raid_disks-1);
+			*dd_idx = (pd_idx + 1 + *dd_idx) % (raid_disks-1);
+			qd_idx = raid_disks - 1;
+			break;
+
+		case ALGORITHM_PARITY_0_6:
+			pd_idx = 0;
+			(*dd_idx)++;
+			qd_idx = raid_disks - 1;
+			break;
+
+		default:
+			BUG();
+		}
+		break;
+	}
+
+	if (sh) {
+		sh->pd_idx = pd_idx;
+		sh->qd_idx = qd_idx;
+		sh->ddf_layout = ddf_layout;
+	}
+	/*
+	 * Finally, compute the new sector number
+	 */
+	new_sector = (sector_t)stripe * sectors_per_chunk + chunk_offset;
+	return new_sector;
+}
+
+sector_t raid5_compute_blocknr(struct stripe_head *sh, int i, int previous)
+{
+	struct r5conf *conf = sh->raid_conf;
+	int raid_disks = sh->disks;
+	int data_disks = raid_disks - conf->max_degraded;
+	sector_t new_sector = sh->sector, check;
+	int sectors_per_chunk = previous ? conf->prev_chunk_sectors
+					 : conf->chunk_sectors;
+	int algorithm = previous ? conf->prev_algo
+				 : conf->algorithm;
+	sector_t stripe;
+	int chunk_offset;
+	sector_t chunk_number;
+	int dummy1, dd_idx = i;
+	sector_t r_sector;
+	struct stripe_head sh2;
+
+	chunk_offset = sector_div(new_sector, sectors_per_chunk);
+	stripe = new_sector;
+
+	if (i == sh->pd_idx)
+		return 0;
+	switch(conf->level) {
+	case 4: break;
+	case 5:
+		switch (algorithm) {
+		case ALGORITHM_LEFT_ASYMMETRIC:
+		case ALGORITHM_RIGHT_ASYMMETRIC:
+			if (i > sh->pd_idx)
+				i--;
+			break;
+		case ALGORITHM_LEFT_SYMMETRIC:
+		case ALGORITHM_RIGHT_SYMMETRIC:
+			if (i < sh->pd_idx)
+				i += raid_disks;
+			i -= (sh->pd_idx + 1);
+			break;
+		case ALGORITHM_PARITY_0:
+			i -= 1;
+			break;
+		case ALGORITHM_PARITY_N:
+			break;
+		default:
+			BUG();
+		}
+		break;
+	case 6:
+		if (i == sh->qd_idx)
+			return 0; /* It is the Q disk */
+		switch (algorithm) {
+		case ALGORITHM_LEFT_ASYMMETRIC:
+		case ALGORITHM_RIGHT_ASYMMETRIC:
+		case ALGORITHM_ROTATING_ZERO_RESTART:
+		case ALGORITHM_ROTATING_N_RESTART:
+			if (sh->pd_idx == raid_disks-1)
+				i--;	/* Q D D D P */
+			else if (i > sh->pd_idx)
+				i -= 2; /* D D P Q D */
+			break;
+		case ALGORITHM_LEFT_SYMMETRIC:
+		case ALGORITHM_RIGHT_SYMMETRIC:
+			if (sh->pd_idx == raid_disks-1)
+				i--; /* Q D D D P */
+			else {
+				/* D D P Q D */
+				if (i < sh->pd_idx)
+					i += raid_disks;
+				i -= (sh->pd_idx + 2);
+			}
+			break;
+		case ALGORITHM_PARITY_0:
+			i -= 2;
+			break;
+		case ALGORITHM_PARITY_N:
+			break;
+		case ALGORITHM_ROTATING_N_CONTINUE:
+			/* Like left_symmetric, but P is before Q */
+			if (sh->pd_idx == 0)
+				i--;	/* P D D D Q */
+			else {
+				/* D D Q P D */
+				if (i < sh->pd_idx)
+					i += raid_disks;
+				i -= (sh->pd_idx + 1);
+			}
+			break;
+		case ALGORITHM_LEFT_ASYMMETRIC_6:
+		case ALGORITHM_RIGHT_ASYMMETRIC_6:
+			if (i > sh->pd_idx)
+				i--;
+			break;
+		case ALGORITHM_LEFT_SYMMETRIC_6:
+		case ALGORITHM_RIGHT_SYMMETRIC_6:
+			if (i < sh->pd_idx)
+				i += data_disks + 1;
+			i -= (sh->pd_idx + 1);
+			break;
+		case ALGORITHM_PARITY_0_6:
+			i -= 1;
+			break;
+		default:
+			BUG();
+		}
+		break;
+	}
+
+	chunk_number = stripe * data_disks + i;
+	r_sector = chunk_number * sectors_per_chunk + chunk_offset;
+
+	check = raid5_compute_sector(conf, r_sector,
+				     previous, &dummy1, &sh2);
+	if (check != sh->sector || dummy1 != dd_idx || sh2.pd_idx != sh->pd_idx
+		|| sh2.qd_idx != sh->qd_idx) {
+		pr_warn("md/raid:%s: compute_blocknr: map not correct\n",
+			mdname(conf->mddev));
+		return 0;
+	}
+	return r_sector;
+}
+
+/*
+ * There are cases where we want handle_stripe_dirtying() and
+ * schedule_reconstruction() to delay towrite to some dev of a stripe.
+ *
+ * This function checks whether we want to delay the towrite. Specifically,
+ * we delay the towrite when:
+ *
+ *   1. degraded stripe has a non-overwrite to the missing dev, AND this
+ *      stripe has data in journal (for other devices).
+ *
+ *      In this case, when reading data for the non-overwrite dev, it is
+ *      necessary to handle complex rmw of write back cache (prexor with
+ *      orig_page, and xor with page). To keep read path simple, we would
+ *      like to flush data in journal to RAID disks first, so complex rmw
+ *      is handled in the write patch (handle_stripe_dirtying).
+ *
+ *   2. when journal space is critical (R5C_LOG_CRITICAL=1)
+ *
+ *      It is important to be able to flush all stripes in raid5-cache.
+ *      Therefore, we need reserve some space on the journal device for
+ *      these flushes. If flush operation includes pending writes to the
+ *      stripe, we need to reserve (conf->raid_disk + 1) pages per stripe
+ *      for the flush out. If we exclude these pending writes from flush
+ *      operation, we only need (conf->max_degraded + 1) pages per stripe.
+ *      Therefore, excluding pending writes in these cases enables more
+ *      efficient use of the journal device.
+ *
+ *      Note: To make sure the stripe makes progress, we only delay
+ *      towrite for stripes with data already in journal (injournal > 0).
+ *      When LOG_CRITICAL, stripes with injournal == 0 will be sent to
+ *      no_space_stripes list.
+ *
+ *   3. during journal failure
+ *      In journal failure, we try to flush all cached data to raid disks
+ *      based on data in stripe cache. The array is read-only to upper
+ *      layers, so we would skip all pending writes.
+ *
+ */
+static inline bool delay_towrite(struct r5conf *conf,
+				 struct r5dev *dev,
+				 struct stripe_head_state *s)
+{
+	/* case 1 above */
+	if (!test_bit(R5_OVERWRITE, &dev->flags) &&
+	    !test_bit(R5_Insync, &dev->flags) && s->injournal)
+		return true;
+	/* case 2 above */
+	if (test_bit(R5C_LOG_CRITICAL, &conf->cache_state) &&
+	    s->injournal > 0)
+		return true;
+	/* case 3 above */
+	if (s->log_failed && s->injournal)
+		return true;
+	return false;
+}
+
+static void
+schedule_reconstruction(struct stripe_head *sh, struct stripe_head_state *s,
+			 int rcw, int expand)
+{
+	int i, pd_idx = sh->pd_idx, qd_idx = sh->qd_idx, disks = sh->disks;
+	struct r5conf *conf = sh->raid_conf;
+	int level = conf->level;
+
+	if (rcw) {
+		/*
+		 * In some cases, handle_stripe_dirtying initially decided to
+		 * run rmw and allocates extra page for prexor. However, rcw is
+		 * cheaper later on. We need to free the extra page now,
+		 * because we won't be able to do that in ops_complete_prexor().
+		 */
+		r5c_release_extra_page(sh);
+
+		for (i = disks; i--; ) {
+			struct r5dev *dev = &sh->dev[i];
+
+			if (dev->towrite && !delay_towrite(conf, dev, s)) {
+				set_bit(R5_LOCKED, &dev->flags);
+				set_bit(R5_Wantdrain, &dev->flags);
+				if (!expand)
+					clear_bit(R5_UPTODATE, &dev->flags);
+				s->locked++;
+			} else if (test_bit(R5_InJournal, &dev->flags)) {
+				set_bit(R5_LOCKED, &dev->flags);
+				s->locked++;
+			}
+		}
+		/* if we are not expanding this is a proper write request, and
+		 * there will be bios with new data to be drained into the
+		 * stripe cache
+		 */
+		if (!expand) {
+			if (!s->locked)
+				/* False alarm, nothing to do */
+				return;
+			sh->reconstruct_state = reconstruct_state_drain_run;
+			set_bit(STRIPE_OP_BIODRAIN, &s->ops_request);
+		} else
+			sh->reconstruct_state = reconstruct_state_run;
+
+		set_bit(STRIPE_OP_RECONSTRUCT, &s->ops_request);
+
+		if (s->locked + conf->max_degraded == disks)
+			if (!test_and_set_bit(STRIPE_FULL_WRITE, &sh->state))
+				atomic_inc(&conf->pending_full_writes);
+	} else {
+		BUG_ON(!(test_bit(R5_UPTODATE, &sh->dev[pd_idx].flags) ||
+			test_bit(R5_Wantcompute, &sh->dev[pd_idx].flags)));
+		BUG_ON(level == 6 &&
+			(!(test_bit(R5_UPTODATE, &sh->dev[qd_idx].flags) ||
+			   test_bit(R5_Wantcompute, &sh->dev[qd_idx].flags))));
+
+		for (i = disks; i--; ) {
+			struct r5dev *dev = &sh->dev[i];
+			if (i == pd_idx || i == qd_idx)
+				continue;
+
+			if (dev->towrite &&
+			    (test_bit(R5_UPTODATE, &dev->flags) ||
+			     test_bit(R5_Wantcompute, &dev->flags))) {
+				set_bit(R5_Wantdrain, &dev->flags);
+				set_bit(R5_LOCKED, &dev->flags);
+				clear_bit(R5_UPTODATE, &dev->flags);
+				s->locked++;
+			} else if (test_bit(R5_InJournal, &dev->flags)) {
+				set_bit(R5_LOCKED, &dev->flags);
+				s->locked++;
+			}
+		}
+		if (!s->locked)
+			/* False alarm - nothing to do */
+			return;
+		sh->reconstruct_state = reconstruct_state_prexor_drain_run;
+		set_bit(STRIPE_OP_PREXOR, &s->ops_request);
+		set_bit(STRIPE_OP_BIODRAIN, &s->ops_request);
+		set_bit(STRIPE_OP_RECONSTRUCT, &s->ops_request);
+	}
+
+	/* keep the parity disk(s) locked while asynchronous operations
+	 * are in flight
+	 */
+	set_bit(R5_LOCKED, &sh->dev[pd_idx].flags);
+	clear_bit(R5_UPTODATE, &sh->dev[pd_idx].flags);
+	s->locked++;
+
+	if (level == 6) {
+		int qd_idx = sh->qd_idx;
+		struct r5dev *dev = &sh->dev[qd_idx];
+
+		set_bit(R5_LOCKED, &dev->flags);
+		clear_bit(R5_UPTODATE, &dev->flags);
+		s->locked++;
+	}
+
+	if (raid5_has_ppl(sh->raid_conf) && sh->ppl_page &&
+	    test_bit(STRIPE_OP_BIODRAIN, &s->ops_request) &&
+	    !test_bit(STRIPE_FULL_WRITE, &sh->state) &&
+	    test_bit(R5_Insync, &sh->dev[pd_idx].flags))
+		set_bit(STRIPE_OP_PARTIAL_PARITY, &s->ops_request);
+
+	pr_debug("%s: stripe %llu locked: %d ops_request: %lx\n",
+		__func__, (unsigned long long)sh->sector,
+		s->locked, s->ops_request);
+}
+
+static bool stripe_bio_overlaps(struct stripe_head *sh, struct bio *bi,
+				int dd_idx, int forwrite)
+{
+	struct r5conf *conf = sh->raid_conf;
+	struct bio **bip;
+
+	pr_debug("checking bi b#%llu to stripe s#%llu\n",
+		 bi->bi_iter.bi_sector, sh->sector);
+
+	/* Don't allow new IO added to stripes in batch list */
+	if (sh->batch_head)
+		return true;
+
+	if (forwrite)
+		bip = &sh->dev[dd_idx].towrite;
+	else
+		bip = &sh->dev[dd_idx].toread;
+
+	while (*bip && (*bip)->bi_iter.bi_sector < bi->bi_iter.bi_sector) {
+		if (bio_end_sector(*bip) > bi->bi_iter.bi_sector)
+			return true;
+		bip = &(*bip)->bi_next;
+	}
+
+	if (*bip && (*bip)->bi_iter.bi_sector < bio_end_sector(bi))
+		return true;
+
+	if (forwrite && raid5_has_ppl(conf)) {
+		/*
+		 * With PPL only writes to consecutive data chunks within a
+		 * stripe are allowed because for a single stripe_head we can
+		 * only have one PPL entry at a time, which describes one data
+		 * range. Not really an overlap, but wait_for_overlap can be
+		 * used to handle this.
+		 */
+		sector_t sector;
+		sector_t first = 0;
+		sector_t last = 0;
+		int count = 0;
+		int i;
+
+		for (i = 0; i < sh->disks; i++) {
+			if (i != sh->pd_idx &&
+			    (i == dd_idx || sh->dev[i].towrite)) {
+				sector = sh->dev[i].sector;
+				if (count == 0 || sector < first)
+					first = sector;
+				if (sector > last)
+					last = sector;
+				count++;
+			}
+		}
+
+		if (first + conf->chunk_sectors * (count - 1) != last)
+			return true;
+	}
+
+	return false;
+}
+
+static void __add_stripe_bio(struct stripe_head *sh, struct bio *bi,
+			     int dd_idx, int forwrite, int previous)
+{
+	struct r5conf *conf = sh->raid_conf;
+	struct bio **bip;
+	int firstwrite = 0;
+
+	if (forwrite) {
+		bip = &sh->dev[dd_idx].towrite;
+		if (!*bip)
+			firstwrite = 1;
+	} else {
+		bip = &sh->dev[dd_idx].toread;
+	}
+
+	while (*bip && (*bip)->bi_iter.bi_sector < bi->bi_iter.bi_sector)
+		bip = &(*bip)->bi_next;
+
+	if (!forwrite || previous)
+		clear_bit(STRIPE_BATCH_READY, &sh->state);
+
+	BUG_ON(*bip && bi->bi_next && (*bip) != bi->bi_next);
+	if (*bip)
+		bi->bi_next = *bip;
+	*bip = bi;
+	bio_inc_remaining(bi);
+	md_write_inc(conf->mddev, bi);
+
+	if (forwrite) {
+		/* check if page is covered */
+		sector_t sector = sh->dev[dd_idx].sector;
+		for (bi=sh->dev[dd_idx].towrite;
+		     sector < sh->dev[dd_idx].sector + RAID5_STRIPE_SECTORS(conf) &&
+			     bi && bi->bi_iter.bi_sector <= sector;
+		     bi = r5_next_bio(conf, bi, sh->dev[dd_idx].sector)) {
+			if (bio_end_sector(bi) >= sector)
+				sector = bio_end_sector(bi);
+		}
+		if (sector >= sh->dev[dd_idx].sector + RAID5_STRIPE_SECTORS(conf))
+			if (!test_and_set_bit(R5_OVERWRITE, &sh->dev[dd_idx].flags))
+				sh->overwrite_disks++;
+	}
+
+	pr_debug("added bi b#%llu to stripe s#%llu, disk %d, logical %llu\n",
+		 (*bip)->bi_iter.bi_sector, sh->sector, dd_idx,
+		 sh->dev[dd_idx].sector);
+
+	if (conf->mddev->bitmap && firstwrite) {
+		/* Cannot hold spinlock over bitmap_startwrite,
+		 * but must ensure this isn't added to a batch until
+		 * we have added to the bitmap and set bm_seq.
+		 * So set STRIPE_BITMAP_PENDING to prevent
+		 * batching.
+		 * If multiple __add_stripe_bio() calls race here they
+		 * much all set STRIPE_BITMAP_PENDING.  So only the first one
+		 * to complete "bitmap_startwrite" gets to set
+		 * STRIPE_BIT_DELAY.  This is important as once a stripe
+		 * is added to a batch, STRIPE_BIT_DELAY cannot be changed
+		 * any more.
+		 */
+		set_bit(STRIPE_BITMAP_PENDING, &sh->state);
+		spin_unlock_irq(&sh->stripe_lock);
+		md_bitmap_startwrite(conf->mddev->bitmap, sh->sector,
+				     RAID5_STRIPE_SECTORS(conf), 0);
+		spin_lock_irq(&sh->stripe_lock);
+		clear_bit(STRIPE_BITMAP_PENDING, &sh->state);
+		if (!sh->batch_head) {
+			sh->bm_seq = conf->seq_flush+1;
+			set_bit(STRIPE_BIT_DELAY, &sh->state);
+		}
+	}
+}
+
+/*
+ * Each stripe/dev can have one or more bios attached.
+ * toread/towrite point to the first in a chain.
+ * The bi_next chain must be in order.
+ */
+static bool add_stripe_bio(struct stripe_head *sh, struct bio *bi,
+			   int dd_idx, int forwrite, int previous)
+{
+	spin_lock_irq(&sh->stripe_lock);
+
+	if (stripe_bio_overlaps(sh, bi, dd_idx, forwrite)) {
+		set_bit(R5_Overlap, &sh->dev[dd_idx].flags);
+		spin_unlock_irq(&sh->stripe_lock);
+		return false;
+	}
+
+	__add_stripe_bio(sh, bi, dd_idx, forwrite, previous);
+	spin_unlock_irq(&sh->stripe_lock);
+	return true;
+}
+
+static void end_reshape(struct r5conf *conf);
+
+static void stripe_set_idx(sector_t stripe, struct r5conf *conf, int previous,
+			    struct stripe_head *sh)
+{
+	int sectors_per_chunk =
+		previous ? conf->prev_chunk_sectors : conf->chunk_sectors;
+	int dd_idx;
+	int chunk_offset = sector_div(stripe, sectors_per_chunk);
+	int disks = previous ? conf->previous_raid_disks : conf->raid_disks;
+
+	raid5_compute_sector(conf,
+			     stripe * (disks - conf->max_degraded)
+			     *sectors_per_chunk + chunk_offset,
+			     previous,
+			     &dd_idx, sh);
+}
+
+static void
+handle_failed_stripe(struct r5conf *conf, struct stripe_head *sh,
+		     struct stripe_head_state *s, int disks)
+{
+	int i;
+	BUG_ON(sh->batch_head);
+	for (i = disks; i--; ) {
+		struct bio *bi;
+		int bitmap_end = 0;
+
+		if (test_bit(R5_ReadError, &sh->dev[i].flags)) {
+			struct md_rdev *rdev;
+			rcu_read_lock();
+			rdev = rcu_dereference(conf->disks[i].rdev);
+			if (rdev && test_bit(In_sync, &rdev->flags) &&
+			    !test_bit(Faulty, &rdev->flags))
+				atomic_inc(&rdev->nr_pending);
+			else
+				rdev = NULL;
+			rcu_read_unlock();
+			if (rdev) {
+				if (!rdev_set_badblocks(
+					    rdev,
+					    sh->sector,
+					    RAID5_STRIPE_SECTORS(conf), 0))
+					md_error(conf->mddev, rdev);
+				rdev_dec_pending(rdev, conf->mddev);
+			}
+		}
+		spin_lock_irq(&sh->stripe_lock);
+		/* fail all writes first */
+		bi = sh->dev[i].towrite;
+		sh->dev[i].towrite = NULL;
+		sh->overwrite_disks = 0;
+		spin_unlock_irq(&sh->stripe_lock);
+		if (bi)
+			bitmap_end = 1;
+
+		log_stripe_write_finished(sh);
+
+		if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
+			wake_up(&conf->wait_for_overlap);
+
+		while (bi && bi->bi_iter.bi_sector <
+			sh->dev[i].sector + RAID5_STRIPE_SECTORS(conf)) {
+			struct bio *nextbi = r5_next_bio(conf, bi, sh->dev[i].sector);
+
+			md_write_end(conf->mddev);
+			bio_io_error(bi);
+			bi = nextbi;
+		}
+		if (bitmap_end)
+			md_bitmap_endwrite(conf->mddev->bitmap, sh->sector,
+					   RAID5_STRIPE_SECTORS(conf), 0, 0);
+		bitmap_end = 0;
+		/* and fail all 'written' */
+		bi = sh->dev[i].written;
+		sh->dev[i].written = NULL;
+		if (test_and_clear_bit(R5_SkipCopy, &sh->dev[i].flags)) {
+			WARN_ON(test_bit(R5_UPTODATE, &sh->dev[i].flags));
+			sh->dev[i].page = sh->dev[i].orig_page;
+		}
+
+		if (bi) bitmap_end = 1;
+		while (bi && bi->bi_iter.bi_sector <
+		       sh->dev[i].sector + RAID5_STRIPE_SECTORS(conf)) {
+			struct bio *bi2 = r5_next_bio(conf, bi, sh->dev[i].sector);
+
+			md_write_end(conf->mddev);
+			bio_io_error(bi);
+			bi = bi2;
+		}
+
+		/* fail any reads if this device is non-operational and
+		 * the data has not reached the cache yet.
+		 */
+		if (!test_bit(R5_Wantfill, &sh->dev[i].flags) &&
+		    s->failed > conf->max_degraded &&
+		    (!test_bit(R5_Insync, &sh->dev[i].flags) ||
+		      test_bit(R5_ReadError, &sh->dev[i].flags))) {
+			spin_lock_irq(&sh->stripe_lock);
+			bi = sh->dev[i].toread;
+			sh->dev[i].toread = NULL;
+			spin_unlock_irq(&sh->stripe_lock);
+			if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
+				wake_up(&conf->wait_for_overlap);
+			if (bi)
+				s->to_read--;
+			while (bi && bi->bi_iter.bi_sector <
+			       sh->dev[i].sector + RAID5_STRIPE_SECTORS(conf)) {
+				struct bio *nextbi =
+					r5_next_bio(conf, bi, sh->dev[i].sector);
+
+				bio_io_error(bi);
+				bi = nextbi;
+			}
+		}
+		if (bitmap_end)
+			md_bitmap_endwrite(conf->mddev->bitmap, sh->sector,
+					   RAID5_STRIPE_SECTORS(conf), 0, 0);
+		/* If we were in the middle of a write the parity block might
+		 * still be locked - so just clear all R5_LOCKED flags
+		 */
+		clear_bit(R5_LOCKED, &sh->dev[i].flags);
+	}
+	s->to_write = 0;
+	s->written = 0;
+
+	if (test_and_clear_bit(STRIPE_FULL_WRITE, &sh->state))
+		if (atomic_dec_and_test(&conf->pending_full_writes))
+			md_wakeup_thread(conf->mddev->thread);
+}
+
+static void
+handle_failed_sync(struct r5conf *conf, struct stripe_head *sh,
+		   struct stripe_head_state *s)
+{
+	int abort = 0;
+	int i;
+
+	BUG_ON(sh->batch_head);
+	clear_bit(STRIPE_SYNCING, &sh->state);
+	if (test_and_clear_bit(R5_Overlap, &sh->dev[sh->pd_idx].flags))
+		wake_up(&conf->wait_for_overlap);
+	s->syncing = 0;
+	s->replacing = 0;
+	/* There is nothing more to do for sync/check/repair.
+	 * Don't even need to abort as that is handled elsewhere
+	 * if needed, and not always wanted e.g. if there is a known
+	 * bad block here.
+	 * For recover/replace we need to record a bad block on all
+	 * non-sync devices, or abort the recovery
+	 */
+	if (test_bit(MD_RECOVERY_RECOVER, &conf->mddev->recovery)) {
+		/* During recovery devices cannot be removed, so
+		 * locking and refcounting of rdevs is not needed
+		 */
+		rcu_read_lock();
+		for (i = 0; i < conf->raid_disks; i++) {
+			struct md_rdev *rdev = rcu_dereference(conf->disks[i].rdev);
+			if (rdev
+			    && !test_bit(Faulty, &rdev->flags)
+			    && !test_bit(In_sync, &rdev->flags)
+			    && !rdev_set_badblocks(rdev, sh->sector,
+						   RAID5_STRIPE_SECTORS(conf), 0))
+				abort = 1;
+			rdev = rcu_dereference(conf->disks[i].replacement);
+			if (rdev
+			    && !test_bit(Faulty, &rdev->flags)
+			    && !test_bit(In_sync, &rdev->flags)
+			    && !rdev_set_badblocks(rdev, sh->sector,
+						   RAID5_STRIPE_SECTORS(conf), 0))
+				abort = 1;
+		}
+		rcu_read_unlock();
+		if (abort)
+			conf->recovery_disabled =
+				conf->mddev->recovery_disabled;
+	}
+	md_done_sync(conf->mddev, RAID5_STRIPE_SECTORS(conf), !abort);
+}
+
+static int want_replace(struct stripe_head *sh, int disk_idx)
+{
+	struct md_rdev *rdev;
+	int rv = 0;
+
+	rcu_read_lock();
+	rdev = rcu_dereference(sh->raid_conf->disks[disk_idx].replacement);
+	if (rdev
+	    && !test_bit(Faulty, &rdev->flags)
+	    && !test_bit(In_sync, &rdev->flags)
+	    && (rdev->recovery_offset <= sh->sector
+		|| rdev->mddev->recovery_cp <= sh->sector))
+		rv = 1;
+	rcu_read_unlock();
+	return rv;
+}
+
+static int need_this_block(struct stripe_head *sh, struct stripe_head_state *s,
+			   int disk_idx, int disks)
+{
+	struct r5dev *dev = &sh->dev[disk_idx];
+	struct r5dev *fdev[2] = { &sh->dev[s->failed_num[0]],
+				  &sh->dev[s->failed_num[1]] };
+	int i;
+	bool force_rcw = (sh->raid_conf->rmw_level == PARITY_DISABLE_RMW);
+
+
+	if (test_bit(R5_LOCKED, &dev->flags) ||
+	    test_bit(R5_UPTODATE, &dev->flags))
+		/* No point reading this as we already have it or have
+		 * decided to get it.
+		 */
+		return 0;
+
+	if (dev->toread ||
+	    (dev->towrite && !test_bit(R5_OVERWRITE, &dev->flags)))
+		/* We need this block to directly satisfy a request */
+		return 1;
+
+	if (s->syncing || s->expanding ||
+	    (s->replacing && want_replace(sh, disk_idx)))
+		/* When syncing, or expanding we read everything.
+		 * When replacing, we need the replaced block.
+		 */
+		return 1;
+
+	if ((s->failed >= 1 && fdev[0]->toread) ||
+	    (s->failed >= 2 && fdev[1]->toread))
+		/* If we want to read from a failed device, then
+		 * we need to actually read every other device.
+		 */
+		return 1;
+
+	/* Sometimes neither read-modify-write nor reconstruct-write
+	 * cycles can work.  In those cases we read every block we
+	 * can.  Then the parity-update is certain to have enough to
+	 * work with.
+	 * This can only be a problem when we need to write something,
+	 * and some device has failed.  If either of those tests
+	 * fail we need look no further.
+	 */
+	if (!s->failed || !s->to_write)
+		return 0;
+
+	if (test_bit(R5_Insync, &dev->flags) &&
+	    !test_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
+		/* Pre-reads at not permitted until after short delay
+		 * to gather multiple requests.  However if this
+		 * device is no Insync, the block could only be computed
+		 * and there is no need to delay that.
+		 */
+		return 0;
+
+	for (i = 0; i < s->failed && i < 2; i++) {
+		if (fdev[i]->towrite &&
+		    !test_bit(R5_UPTODATE, &fdev[i]->flags) &&
+		    !test_bit(R5_OVERWRITE, &fdev[i]->flags))
+			/* If we have a partial write to a failed
+			 * device, then we will need to reconstruct
+			 * the content of that device, so all other
+			 * devices must be read.
+			 */
+			return 1;
+
+		if (s->failed >= 2 &&
+		    (fdev[i]->towrite ||
+		     s->failed_num[i] == sh->pd_idx ||
+		     s->failed_num[i] == sh->qd_idx) &&
+		    !test_bit(R5_UPTODATE, &fdev[i]->flags))
+			/* In max degraded raid6, If the failed disk is P, Q,
+			 * or we want to read the failed disk, we need to do
+			 * reconstruct-write.
+			 */
+			force_rcw = true;
+	}
+
+	/* If we are forced to do a reconstruct-write, because parity
+	 * cannot be trusted and we are currently recovering it, there
+	 * is extra need to be careful.
+	 * If one of the devices that we would need to read, because
+	 * it is not being overwritten (and maybe not written at all)
+	 * is missing/faulty, then we need to read everything we can.
+	 */
+	if (!force_rcw &&
+	    sh->sector < sh->raid_conf->mddev->recovery_cp)
+		/* reconstruct-write isn't being forced */
+		return 0;
+	for (i = 0; i < s->failed && i < 2; i++) {
+		if (s->failed_num[i] != sh->pd_idx &&
+		    s->failed_num[i] != sh->qd_idx &&
+		    !test_bit(R5_UPTODATE, &fdev[i]->flags) &&
+		    !test_bit(R5_OVERWRITE, &fdev[i]->flags))
+			return 1;
+	}
+
+	return 0;
+}
+
+/* fetch_block - checks the given member device to see if its data needs
+ * to be read or computed to satisfy a request.
+ *
+ * Returns 1 when no more member devices need to be checked, otherwise returns
+ * 0 to tell the loop in handle_stripe_fill to continue
+ */
+static int fetch_block(struct stripe_head *sh, struct stripe_head_state *s,
+		       int disk_idx, int disks)
+{
+	struct r5dev *dev = &sh->dev[disk_idx];
+
+	/* is the data in this block needed, and can we get it? */
+	if (need_this_block(sh, s, disk_idx, disks)) {
+		/* we would like to get this block, possibly by computing it,
+		 * otherwise read it if the backing disk is insync
+		 */
+		BUG_ON(test_bit(R5_Wantcompute, &dev->flags));
+		BUG_ON(test_bit(R5_Wantread, &dev->flags));
+		BUG_ON(sh->batch_head);
+
+		/*
+		 * In the raid6 case if the only non-uptodate disk is P
+		 * then we already trusted P to compute the other failed
+		 * drives. It is safe to compute rather than re-read P.
+		 * In other cases we only compute blocks from failed
+		 * devices, otherwise check/repair might fail to detect
+		 * a real inconsistency.
+		 */
+
+		if ((s->uptodate == disks - 1) &&
+		    ((sh->qd_idx >= 0 && sh->pd_idx == disk_idx) ||
+		    (s->failed && (disk_idx == s->failed_num[0] ||
+				   disk_idx == s->failed_num[1])))) {
+			/* have disk failed, and we're requested to fetch it;
+			 * do compute it
+			 */
+			pr_debug("Computing stripe %llu block %d\n",
+			       (unsigned long long)sh->sector, disk_idx);
+			set_bit(STRIPE_COMPUTE_RUN, &sh->state);
+			set_bit(STRIPE_OP_COMPUTE_BLK, &s->ops_request);
+			set_bit(R5_Wantcompute, &dev->flags);
+			sh->ops.target = disk_idx;
+			sh->ops.target2 = -1; /* no 2nd target */
+			s->req_compute = 1;
+			/* Careful: from this point on 'uptodate' is in the eye
+			 * of raid_run_ops which services 'compute' operations
+			 * before writes. R5_Wantcompute flags a block that will
+			 * be R5_UPTODATE by the time it is needed for a
+			 * subsequent operation.
+			 */
+			s->uptodate++;
+			return 1;
+		} else if (s->uptodate == disks-2 && s->failed >= 2) {
+			/* Computing 2-failure is *very* expensive; only
+			 * do it if failed >= 2
+			 */
+			int other;
+			for (other = disks; other--; ) {
+				if (other == disk_idx)
+					continue;
+				if (!test_bit(R5_UPTODATE,
+				      &sh->dev[other].flags))
+					break;
+			}
+			BUG_ON(other < 0);
+			pr_debug("Computing stripe %llu blocks %d,%d\n",
+			       (unsigned long long)sh->sector,
+			       disk_idx, other);
+			set_bit(STRIPE_COMPUTE_RUN, &sh->state);
+			set_bit(STRIPE_OP_COMPUTE_BLK, &s->ops_request);
+			set_bit(R5_Wantcompute, &sh->dev[disk_idx].flags);
+			set_bit(R5_Wantcompute, &sh->dev[other].flags);
+			sh->ops.target = disk_idx;
+			sh->ops.target2 = other;
+			s->uptodate += 2;
+			s->req_compute = 1;
+			return 1;
+		} else if (test_bit(R5_Insync, &dev->flags)) {
+			set_bit(R5_LOCKED, &dev->flags);
+			set_bit(R5_Wantread, &dev->flags);
+			s->locked++;
+			pr_debug("Reading block %d (sync=%d)\n",
+				disk_idx, s->syncing);
+		}
+	}
+
+	return 0;
+}
+
+/*
+ * handle_stripe_fill - read or compute data to satisfy pending requests.
+ */
+static void handle_stripe_fill(struct stripe_head *sh,
+			       struct stripe_head_state *s,
+			       int disks)
+{
+	int i;
+
+	/* look for blocks to read/compute, skip this if a compute
+	 * is already in flight, or if the stripe contents are in the
+	 * midst of changing due to a write
+	 */
+	if (!test_bit(STRIPE_COMPUTE_RUN, &sh->state) && !sh->check_state &&
+	    !sh->reconstruct_state) {
+
+		/*
+		 * For degraded stripe with data in journal, do not handle
+		 * read requests yet, instead, flush the stripe to raid
+		 * disks first, this avoids handling complex rmw of write
+		 * back cache (prexor with orig_page, and then xor with
+		 * page) in the read path
+		 */
+		if (s->to_read && s->injournal && s->failed) {
+			if (test_bit(STRIPE_R5C_CACHING, &sh->state))
+				r5c_make_stripe_write_out(sh);
+			goto out;
+		}
+
+		for (i = disks; i--; )
+			if (fetch_block(sh, s, i, disks))
+				break;
+	}
+out:
+	set_bit(STRIPE_HANDLE, &sh->state);
+}
+
+static void break_stripe_batch_list(struct stripe_head *head_sh,
+				    unsigned long handle_flags);
+/* handle_stripe_clean_event
+ * any written block on an uptodate or failed drive can be returned.
+ * Note that if we 'wrote' to a failed drive, it will be UPTODATE, but
+ * never LOCKED, so we don't need to test 'failed' directly.
+ */
+static void handle_stripe_clean_event(struct r5conf *conf,
+	struct stripe_head *sh, int disks)
+{
+	int i;
+	struct r5dev *dev;
+	int discard_pending = 0;
+	struct stripe_head *head_sh = sh;
+	bool do_endio = false;
+
+	for (i = disks; i--; )
+		if (sh->dev[i].written) {
+			dev = &sh->dev[i];
+			if (!test_bit(R5_LOCKED, &dev->flags) &&
+			    (test_bit(R5_UPTODATE, &dev->flags) ||
+			     test_bit(R5_Discard, &dev->flags) ||
+			     test_bit(R5_SkipCopy, &dev->flags))) {
+				/* We can return any write requests */
+				struct bio *wbi, *wbi2;
+				pr_debug("Return write for disc %d\n", i);
+				if (test_and_clear_bit(R5_Discard, &dev->flags))
+					clear_bit(R5_UPTODATE, &dev->flags);
+				if (test_and_clear_bit(R5_SkipCopy, &dev->flags)) {
+					WARN_ON(test_bit(R5_UPTODATE, &dev->flags));
+				}
+				do_endio = true;
+
+returnbi:
+				dev->page = dev->orig_page;
+				wbi = dev->written;
+				dev->written = NULL;
+				while (wbi && wbi->bi_iter.bi_sector <
+					dev->sector + RAID5_STRIPE_SECTORS(conf)) {
+					wbi2 = r5_next_bio(conf, wbi, dev->sector);
+					md_write_end(conf->mddev);
+					bio_endio(wbi);
+					wbi = wbi2;
+				}
+				md_bitmap_endwrite(conf->mddev->bitmap, sh->sector,
+						   RAID5_STRIPE_SECTORS(conf),
+						   !test_bit(STRIPE_DEGRADED, &sh->state),
+						   0);
+				if (head_sh->batch_head) {
+					sh = list_first_entry(&sh->batch_list,
+							      struct stripe_head,
+							      batch_list);
+					if (sh != head_sh) {
+						dev = &sh->dev[i];
+						goto returnbi;
+					}
+				}
+				sh = head_sh;
+				dev = &sh->dev[i];
+			} else if (test_bit(R5_Discard, &dev->flags))
+				discard_pending = 1;
+		}
+
+	log_stripe_write_finished(sh);
+
+	if (!discard_pending &&
+	    test_bit(R5_Discard, &sh->dev[sh->pd_idx].flags)) {
+		int hash;
+		clear_bit(R5_Discard, &sh->dev[sh->pd_idx].flags);
+		clear_bit(R5_UPTODATE, &sh->dev[sh->pd_idx].flags);
+		if (sh->qd_idx >= 0) {
+			clear_bit(R5_Discard, &sh->dev[sh->qd_idx].flags);
+			clear_bit(R5_UPTODATE, &sh->dev[sh->qd_idx].flags);
+		}
+		/* now that discard is done we can proceed with any sync */
+		clear_bit(STRIPE_DISCARD, &sh->state);
+		/*
+		 * SCSI discard will change some bio fields and the stripe has
+		 * no updated data, so remove it from hash list and the stripe
+		 * will be reinitialized
+		 */
+unhash:
+		hash = sh->hash_lock_index;
+		spin_lock_irq(conf->hash_locks + hash);
+		remove_hash(sh);
+		spin_unlock_irq(conf->hash_locks + hash);
+		if (head_sh->batch_head) {
+			sh = list_first_entry(&sh->batch_list,
+					      struct stripe_head, batch_list);
+			if (sh != head_sh)
+					goto unhash;
+		}
+		sh = head_sh;
+
+		if (test_bit(STRIPE_SYNC_REQUESTED, &sh->state))
+			set_bit(STRIPE_HANDLE, &sh->state);
+
+	}
+
+	if (test_and_clear_bit(STRIPE_FULL_WRITE, &sh->state))
+		if (atomic_dec_and_test(&conf->pending_full_writes))
+			md_wakeup_thread(conf->mddev->thread);
+
+	if (head_sh->batch_head && do_endio)
+		break_stripe_batch_list(head_sh, STRIPE_EXPAND_SYNC_FLAGS);
+}
+
+/*
+ * For RMW in write back cache, we need extra page in prexor to store the
+ * old data. This page is stored in dev->orig_page.
+ *
+ * This function checks whether we have data for prexor. The exact logic
+ * is:
+ *       R5_UPTODATE && (!R5_InJournal || R5_OrigPageUPTDODATE)
+ */
+static inline bool uptodate_for_rmw(struct r5dev *dev)
+{
+	return (test_bit(R5_UPTODATE, &dev->flags)) &&
+		(!test_bit(R5_InJournal, &dev->flags) ||
+		 test_bit(R5_OrigPageUPTDODATE, &dev->flags));
+}
+
+static int handle_stripe_dirtying(struct r5conf *conf,
+				  struct stripe_head *sh,
+				  struct stripe_head_state *s,
+				  int disks)
+{
+	int rmw = 0, rcw = 0, i;
+	sector_t recovery_cp = conf->mddev->recovery_cp;
+
+	/* Check whether resync is now happening or should start.
+	 * If yes, then the array is dirty (after unclean shutdown or
+	 * initial creation), so parity in some stripes might be inconsistent.
+	 * In this case, we need to always do reconstruct-write, to ensure
+	 * that in case of drive failure or read-error correction, we
+	 * generate correct data from the parity.
+	 */
+	if (conf->rmw_level == PARITY_DISABLE_RMW ||
+	    (recovery_cp < MaxSector && sh->sector >= recovery_cp &&
+	     s->failed == 0)) {
+		/* Calculate the real rcw later - for now make it
+		 * look like rcw is cheaper
+		 */
+		rcw = 1; rmw = 2;
+		pr_debug("force RCW rmw_level=%u, recovery_cp=%llu sh->sector=%llu\n",
+			 conf->rmw_level, (unsigned long long)recovery_cp,
+			 (unsigned long long)sh->sector);
+	} else for (i = disks; i--; ) {
+		/* would I have to read this buffer for read_modify_write */
+		struct r5dev *dev = &sh->dev[i];
+		if (((dev->towrite && !delay_towrite(conf, dev, s)) ||
+		     i == sh->pd_idx || i == sh->qd_idx ||
+		     test_bit(R5_InJournal, &dev->flags)) &&
+		    !test_bit(R5_LOCKED, &dev->flags) &&
+		    !(uptodate_for_rmw(dev) ||
+		      test_bit(R5_Wantcompute, &dev->flags))) {
+			if (test_bit(R5_Insync, &dev->flags))
+				rmw++;
+			else
+				rmw += 2*disks;  /* cannot read it */
+		}
+		/* Would I have to read this buffer for reconstruct_write */
+		if (!test_bit(R5_OVERWRITE, &dev->flags) &&
+		    i != sh->pd_idx && i != sh->qd_idx &&
+		    !test_bit(R5_LOCKED, &dev->flags) &&
+		    !(test_bit(R5_UPTODATE, &dev->flags) ||
+		      test_bit(R5_Wantcompute, &dev->flags))) {
+			if (test_bit(R5_Insync, &dev->flags))
+				rcw++;
+			else
+				rcw += 2*disks;
+		}
+	}
+
+	pr_debug("for sector %llu state 0x%lx, rmw=%d rcw=%d\n",
+		 (unsigned long long)sh->sector, sh->state, rmw, rcw);
+	set_bit(STRIPE_HANDLE, &sh->state);
+	if ((rmw < rcw || (rmw == rcw && conf->rmw_level == PARITY_PREFER_RMW)) && rmw > 0) {
+		/* prefer read-modify-write, but need to get some data */
+		if (conf->mddev->queue)
+			blk_add_trace_msg(conf->mddev->queue,
+					  "raid5 rmw %llu %d",
+					  (unsigned long long)sh->sector, rmw);
+		for (i = disks; i--; ) {
+			struct r5dev *dev = &sh->dev[i];
+			if (test_bit(R5_InJournal, &dev->flags) &&
+			    dev->page == dev->orig_page &&
+			    !test_bit(R5_LOCKED, &sh->dev[sh->pd_idx].flags)) {
+				/* alloc page for prexor */
+				struct page *p = alloc_page(GFP_NOIO);
+
+				if (p) {
+					dev->orig_page = p;
+					continue;
+				}
+
+				/*
+				 * alloc_page() failed, try use
+				 * disk_info->extra_page
+				 */
+				if (!test_and_set_bit(R5C_EXTRA_PAGE_IN_USE,
+						      &conf->cache_state)) {
+					r5c_use_extra_page(sh);
+					break;
+				}
+
+				/* extra_page in use, add to delayed_list */
+				set_bit(STRIPE_DELAYED, &sh->state);
+				s->waiting_extra_page = 1;
+				return -EAGAIN;
+			}
+		}
+
+		for (i = disks; i--; ) {
+			struct r5dev *dev = &sh->dev[i];
+			if (((dev->towrite && !delay_towrite(conf, dev, s)) ||
+			     i == sh->pd_idx || i == sh->qd_idx ||
+			     test_bit(R5_InJournal, &dev->flags)) &&
+			    !test_bit(R5_LOCKED, &dev->flags) &&
+			    !(uptodate_for_rmw(dev) ||
+			      test_bit(R5_Wantcompute, &dev->flags)) &&
+			    test_bit(R5_Insync, &dev->flags)) {
+				if (test_bit(STRIPE_PREREAD_ACTIVE,
+					     &sh->state)) {
+					pr_debug("Read_old block %d for r-m-w\n",
+						 i);
+					set_bit(R5_LOCKED, &dev->flags);
+					set_bit(R5_Wantread, &dev->flags);
+					s->locked++;
+				} else
+					set_bit(STRIPE_DELAYED, &sh->state);
+			}
+		}
+	}
+	if ((rcw < rmw || (rcw == rmw && conf->rmw_level != PARITY_PREFER_RMW)) && rcw > 0) {
+		/* want reconstruct write, but need to get some data */
+		int qread =0;
+		rcw = 0;
+		for (i = disks; i--; ) {
+			struct r5dev *dev = &sh->dev[i];
+			if (!test_bit(R5_OVERWRITE, &dev->flags) &&
+			    i != sh->pd_idx && i != sh->qd_idx &&
+			    !test_bit(R5_LOCKED, &dev->flags) &&
+			    !(test_bit(R5_UPTODATE, &dev->flags) ||
+			      test_bit(R5_Wantcompute, &dev->flags))) {
+				rcw++;
+				if (test_bit(R5_Insync, &dev->flags) &&
+				    test_bit(STRIPE_PREREAD_ACTIVE,
+					     &sh->state)) {
+					pr_debug("Read_old block "
+						"%d for Reconstruct\n", i);
+					set_bit(R5_LOCKED, &dev->flags);
+					set_bit(R5_Wantread, &dev->flags);
+					s->locked++;
+					qread++;
+				} else
+					set_bit(STRIPE_DELAYED, &sh->state);
+			}
+		}
+		if (rcw && conf->mddev->queue)
+			blk_add_trace_msg(conf->mddev->queue, "raid5 rcw %llu %d %d %d",
+					  (unsigned long long)sh->sector,
+					  rcw, qread, test_bit(STRIPE_DELAYED, &sh->state));
+	}
+
+	if (rcw > disks && rmw > disks &&
+	    !test_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
+		set_bit(STRIPE_DELAYED, &sh->state);
+
+	/* now if nothing is locked, and if we have enough data,
+	 * we can start a write request
+	 */
+	/* since handle_stripe can be called at any time we need to handle the
+	 * case where a compute block operation has been submitted and then a
+	 * subsequent call wants to start a write request.  raid_run_ops only
+	 * handles the case where compute block and reconstruct are requested
+	 * simultaneously.  If this is not the case then new writes need to be
+	 * held off until the compute completes.
+	 */
+	if ((s->req_compute || !test_bit(STRIPE_COMPUTE_RUN, &sh->state)) &&
+	    (s->locked == 0 && (rcw == 0 || rmw == 0) &&
+	     !test_bit(STRIPE_BIT_DELAY, &sh->state)))
+		schedule_reconstruction(sh, s, rcw == 0, 0);
+	return 0;
+}
+
+static void handle_parity_checks5(struct r5conf *conf, struct stripe_head *sh,
+				struct stripe_head_state *s, int disks)
+{
+	struct r5dev *dev = NULL;
+
+	BUG_ON(sh->batch_head);
+	set_bit(STRIPE_HANDLE, &sh->state);
+
+	switch (sh->check_state) {
+	case check_state_idle:
+		/* start a new check operation if there are no failures */
+		if (s->failed == 0) {
+			BUG_ON(s->uptodate != disks);
+			sh->check_state = check_state_run;
+			set_bit(STRIPE_OP_CHECK, &s->ops_request);
+			clear_bit(R5_UPTODATE, &sh->dev[sh->pd_idx].flags);
+			s->uptodate--;
+			break;
+		}
+		dev = &sh->dev[s->failed_num[0]];
+		fallthrough;
+	case check_state_compute_result:
+		sh->check_state = check_state_idle;
+		if (!dev)
+			dev = &sh->dev[sh->pd_idx];
+
+		/* check that a write has not made the stripe insync */
+		if (test_bit(STRIPE_INSYNC, &sh->state))
+			break;
+
+		/* either failed parity check, or recovery is happening */
+		BUG_ON(!test_bit(R5_UPTODATE, &dev->flags));
+		BUG_ON(s->uptodate != disks);
+
+		set_bit(R5_LOCKED, &dev->flags);
+		s->locked++;
+		set_bit(R5_Wantwrite, &dev->flags);
+
+		clear_bit(STRIPE_DEGRADED, &sh->state);
+		set_bit(STRIPE_INSYNC, &sh->state);
+		break;
+	case check_state_run:
+		break; /* we will be called again upon completion */
+	case check_state_check_result:
+		sh->check_state = check_state_idle;
+
+		/* if a failure occurred during the check operation, leave
+		 * STRIPE_INSYNC not set and let the stripe be handled again
+		 */
+		if (s->failed)
+			break;
+
+		/* handle a successful check operation, if parity is correct
+		 * we are done.  Otherwise update the mismatch count and repair
+		 * parity if !MD_RECOVERY_CHECK
+		 */
+		if ((sh->ops.zero_sum_result & SUM_CHECK_P_RESULT) == 0)
+			/* parity is correct (on disc,
+			 * not in buffer any more)
+			 */
+			set_bit(STRIPE_INSYNC, &sh->state);
+		else {
+			atomic64_add(RAID5_STRIPE_SECTORS(conf), &conf->mddev->resync_mismatches);
+			if (test_bit(MD_RECOVERY_CHECK, &conf->mddev->recovery)) {
+				/* don't try to repair!! */
+				set_bit(STRIPE_INSYNC, &sh->state);
+				pr_warn_ratelimited("%s: mismatch sector in range "
+						    "%llu-%llu\n", mdname(conf->mddev),
+						    (unsigned long long) sh->sector,
+						    (unsigned long long) sh->sector +
+						    RAID5_STRIPE_SECTORS(conf));
+			} else {
+				sh->check_state = check_state_compute_run;
+				set_bit(STRIPE_COMPUTE_RUN, &sh->state);
+				set_bit(STRIPE_OP_COMPUTE_BLK, &s->ops_request);
+				set_bit(R5_Wantcompute,
+					&sh->dev[sh->pd_idx].flags);
+				sh->ops.target = sh->pd_idx;
+				sh->ops.target2 = -1;
+				s->uptodate++;
+			}
+		}
+		break;
+	case check_state_compute_run:
+		break;
+	default:
+		pr_err("%s: unknown check_state: %d sector: %llu\n",
+		       __func__, sh->check_state,
+		       (unsigned long long) sh->sector);
+		BUG();
+	}
+}
+
+static void handle_parity_checks6(struct r5conf *conf, struct stripe_head *sh,
+				  struct stripe_head_state *s,
+				  int disks)
+{
+	int pd_idx = sh->pd_idx;
+	int qd_idx = sh->qd_idx;
+	struct r5dev *dev;
+
+	BUG_ON(sh->batch_head);
+	set_bit(STRIPE_HANDLE, &sh->state);
+
+	BUG_ON(s->failed > 2);
+
+	/* Want to check and possibly repair P and Q.
+	 * However there could be one 'failed' device, in which
+	 * case we can only check one of them, possibly using the
+	 * other to generate missing data
+	 */
+
+	switch (sh->check_state) {
+	case check_state_idle:
+		/* start a new check operation if there are < 2 failures */
+		if (s->failed == s->q_failed) {
+			/* The only possible failed device holds Q, so it
+			 * makes sense to check P (If anything else were failed,
+			 * we would have used P to recreate it).
+			 */
+			sh->check_state = check_state_run;
+		}
+		if (!s->q_failed && s->failed < 2) {
+			/* Q is not failed, and we didn't use it to generate
+			 * anything, so it makes sense to check it
+			 */
+			if (sh->check_state == check_state_run)
+				sh->check_state = check_state_run_pq;
+			else
+				sh->check_state = check_state_run_q;
+		}
+
+		/* discard potentially stale zero_sum_result */
+		sh->ops.zero_sum_result = 0;
+
+		if (sh->check_state == check_state_run) {
+			/* async_xor_zero_sum destroys the contents of P */
+			clear_bit(R5_UPTODATE, &sh->dev[pd_idx].flags);
+			s->uptodate--;
+		}
+		if (sh->check_state >= check_state_run &&
+		    sh->check_state <= check_state_run_pq) {
+			/* async_syndrome_zero_sum preserves P and Q, so
+			 * no need to mark them !uptodate here
+			 */
+			set_bit(STRIPE_OP_CHECK, &s->ops_request);
+			break;
+		}
+
+		/* we have 2-disk failure */
+		BUG_ON(s->failed != 2);
+		fallthrough;
+	case check_state_compute_result:
+		sh->check_state = check_state_idle;
+
+		/* check that a write has not made the stripe insync */
+		if (test_bit(STRIPE_INSYNC, &sh->state))
+			break;
+
+		/* now write out any block on a failed drive,
+		 * or P or Q if they were recomputed
+		 */
+		dev = NULL;
+		if (s->failed == 2) {
+			dev = &sh->dev[s->failed_num[1]];
+			s->locked++;
+			set_bit(R5_LOCKED, &dev->flags);
+			set_bit(R5_Wantwrite, &dev->flags);
+		}
+		if (s->failed >= 1) {
+			dev = &sh->dev[s->failed_num[0]];
+			s->locked++;
+			set_bit(R5_LOCKED, &dev->flags);
+			set_bit(R5_Wantwrite, &dev->flags);
+		}
+		if (sh->ops.zero_sum_result & SUM_CHECK_P_RESULT) {
+			dev = &sh->dev[pd_idx];
+			s->locked++;
+			set_bit(R5_LOCKED, &dev->flags);
+			set_bit(R5_Wantwrite, &dev->flags);
+		}
+		if (sh->ops.zero_sum_result & SUM_CHECK_Q_RESULT) {
+			dev = &sh->dev[qd_idx];
+			s->locked++;
+			set_bit(R5_LOCKED, &dev->flags);
+			set_bit(R5_Wantwrite, &dev->flags);
+		}
+		if (WARN_ONCE(dev && !test_bit(R5_UPTODATE, &dev->flags),
+			      "%s: disk%td not up to date\n",
+			      mdname(conf->mddev),
+			      dev - (struct r5dev *) &sh->dev)) {
+			clear_bit(R5_LOCKED, &dev->flags);
+			clear_bit(R5_Wantwrite, &dev->flags);
+			s->locked--;
+		}
+		clear_bit(STRIPE_DEGRADED, &sh->state);
+
+		set_bit(STRIPE_INSYNC, &sh->state);
+		break;
+	case check_state_run:
+	case check_state_run_q:
+	case check_state_run_pq:
+		break; /* we will be called again upon completion */
+	case check_state_check_result:
+		sh->check_state = check_state_idle;
+
+		/* handle a successful check operation, if parity is correct
+		 * we are done.  Otherwise update the mismatch count and repair
+		 * parity if !MD_RECOVERY_CHECK
+		 */
+		if (sh->ops.zero_sum_result == 0) {
+			/* both parities are correct */
+			if (!s->failed)
+				set_bit(STRIPE_INSYNC, &sh->state);
+			else {
+				/* in contrast to the raid5 case we can validate
+				 * parity, but still have a failure to write
+				 * back
+				 */
+				sh->check_state = check_state_compute_result;
+				/* Returning at this point means that we may go
+				 * off and bring p and/or q uptodate again so
+				 * we make sure to check zero_sum_result again
+				 * to verify if p or q need writeback
+				 */
+			}
+		} else {
+			atomic64_add(RAID5_STRIPE_SECTORS(conf), &conf->mddev->resync_mismatches);
+			if (test_bit(MD_RECOVERY_CHECK, &conf->mddev->recovery)) {
+				/* don't try to repair!! */
+				set_bit(STRIPE_INSYNC, &sh->state);
+				pr_warn_ratelimited("%s: mismatch sector in range "
+						    "%llu-%llu\n", mdname(conf->mddev),
+						    (unsigned long long) sh->sector,
+						    (unsigned long long) sh->sector +
+						    RAID5_STRIPE_SECTORS(conf));
+			} else {
+				int *target = &sh->ops.target;
+
+				sh->ops.target = -1;
+				sh->ops.target2 = -1;
+				sh->check_state = check_state_compute_run;
+				set_bit(STRIPE_COMPUTE_RUN, &sh->state);
+				set_bit(STRIPE_OP_COMPUTE_BLK, &s->ops_request);
+				if (sh->ops.zero_sum_result & SUM_CHECK_P_RESULT) {
+					set_bit(R5_Wantcompute,
+						&sh->dev[pd_idx].flags);
+					*target = pd_idx;
+					target = &sh->ops.target2;
+					s->uptodate++;
+				}
+				if (sh->ops.zero_sum_result & SUM_CHECK_Q_RESULT) {
+					set_bit(R5_Wantcompute,
+						&sh->dev[qd_idx].flags);
+					*target = qd_idx;
+					s->uptodate++;
+				}
+			}
+		}
+		break;
+	case check_state_compute_run:
+		break;
+	default:
+		pr_warn("%s: unknown check_state: %d sector: %llu\n",
+			__func__, sh->check_state,
+			(unsigned long long) sh->sector);
+		BUG();
+	}
+}
+
+static void handle_stripe_expansion(struct r5conf *conf, struct stripe_head *sh)
+{
+	int i;
+
+	/* We have read all the blocks in this stripe and now we need to
+	 * copy some of them into a target stripe for expand.
+	 */
+	struct dma_async_tx_descriptor *tx = NULL;
+	BUG_ON(sh->batch_head);
+	clear_bit(STRIPE_EXPAND_SOURCE, &sh->state);
+	for (i = 0; i < sh->disks; i++)
+		if (i != sh->pd_idx && i != sh->qd_idx) {
+			int dd_idx, j;
+			struct stripe_head *sh2;
+			struct async_submit_ctl submit;
+
+			sector_t bn = raid5_compute_blocknr(sh, i, 1);
+			sector_t s = raid5_compute_sector(conf, bn, 0,
+							  &dd_idx, NULL);
+			sh2 = raid5_get_active_stripe(conf, NULL, s,
+				R5_GAS_NOBLOCK | R5_GAS_NOQUIESCE);
+			if (sh2 == NULL)
+				/* so far only the early blocks of this stripe
+				 * have been requested.  When later blocks
+				 * get requested, we will try again
+				 */
+				continue;
+			if (!test_bit(STRIPE_EXPANDING, &sh2->state) ||
+			   test_bit(R5_Expanded, &sh2->dev[dd_idx].flags)) {
+				/* must have already done this block */
+				raid5_release_stripe(sh2);
+				continue;
+			}
+
+			/* place all the copies on one channel */
+			init_async_submit(&submit, 0, tx, NULL, NULL, NULL);
+			tx = async_memcpy(sh2->dev[dd_idx].page,
+					  sh->dev[i].page, sh2->dev[dd_idx].offset,
+					  sh->dev[i].offset, RAID5_STRIPE_SIZE(conf),
+					  &submit);
+
+			set_bit(R5_Expanded, &sh2->dev[dd_idx].flags);
+			set_bit(R5_UPTODATE, &sh2->dev[dd_idx].flags);
+			for (j = 0; j < conf->raid_disks; j++)
+				if (j != sh2->pd_idx &&
+				    j != sh2->qd_idx &&
+				    !test_bit(R5_Expanded, &sh2->dev[j].flags))
+					break;
+			if (j == conf->raid_disks) {
+				set_bit(STRIPE_EXPAND_READY, &sh2->state);
+				set_bit(STRIPE_HANDLE, &sh2->state);
+			}
+			raid5_release_stripe(sh2);
+
+		}
+	/* done submitting copies, wait for them to complete */
+	async_tx_quiesce(&tx);
+}
+
+/*
+ * handle_stripe - do things to a stripe.
+ *
+ * We lock the stripe by setting STRIPE_ACTIVE and then examine the
+ * state of various bits to see what needs to be done.
+ * Possible results:
+ *    return some read requests which now have data
+ *    return some write requests which are safely on storage
+ *    schedule a read on some buffers
+ *    schedule a write of some buffers
+ *    return confirmation of parity correctness
+ *
+ */
+
+static void analyse_stripe(struct stripe_head *sh, struct stripe_head_state *s)
+{
+	struct r5conf *conf = sh->raid_conf;
+	int disks = sh->disks;
+	struct r5dev *dev;
+	int i;
+	int do_recovery = 0;
+
+	memset(s, 0, sizeof(*s));
+
+	s->expanding = test_bit(STRIPE_EXPAND_SOURCE, &sh->state) && !sh->batch_head;
+	s->expanded = test_bit(STRIPE_EXPAND_READY, &sh->state) && !sh->batch_head;
+	s->failed_num[0] = -1;
+	s->failed_num[1] = -1;
+	s->log_failed = r5l_log_disk_error(conf);
+
+	/* Now to look around and see what can be done */
+	rcu_read_lock();
+	for (i=disks; i--; ) {
+		struct md_rdev *rdev;
+		sector_t first_bad;
+		int bad_sectors;
+		int is_bad = 0;
+
+		dev = &sh->dev[i];
+
+		pr_debug("check %d: state 0x%lx read %p write %p written %p\n",
+			 i, dev->flags,
+			 dev->toread, dev->towrite, dev->written);
+		/* maybe we can reply to a read
+		 *
+		 * new wantfill requests are only permitted while
+		 * ops_complete_biofill is guaranteed to be inactive
+		 */
+		if (test_bit(R5_UPTODATE, &dev->flags) && dev->toread &&
+		    !test_bit(STRIPE_BIOFILL_RUN, &sh->state))
+			set_bit(R5_Wantfill, &dev->flags);
+
+		/* now count some things */
+		if (test_bit(R5_LOCKED, &dev->flags))
+			s->locked++;
+		if (test_bit(R5_UPTODATE, &dev->flags))
+			s->uptodate++;
+		if (test_bit(R5_Wantcompute, &dev->flags)) {
+			s->compute++;
+			BUG_ON(s->compute > 2);
+		}
+
+		if (test_bit(R5_Wantfill, &dev->flags))
+			s->to_fill++;
+		else if (dev->toread)
+			s->to_read++;
+		if (dev->towrite) {
+			s->to_write++;
+			if (!test_bit(R5_OVERWRITE, &dev->flags))
+				s->non_overwrite++;
+		}
+		if (dev->written)
+			s->written++;
+		/* Prefer to use the replacement for reads, but only
+		 * if it is recovered enough and has no bad blocks.
+		 */
+		rdev = rcu_dereference(conf->disks[i].replacement);
+		if (rdev && !test_bit(Faulty, &rdev->flags) &&
+		    rdev->recovery_offset >= sh->sector + RAID5_STRIPE_SECTORS(conf) &&
+		    !is_badblock(rdev, sh->sector, RAID5_STRIPE_SECTORS(conf),
+				 &first_bad, &bad_sectors))
+			set_bit(R5_ReadRepl, &dev->flags);
+		else {
+			if (rdev && !test_bit(Faulty, &rdev->flags))
+				set_bit(R5_NeedReplace, &dev->flags);
+			else
+				clear_bit(R5_NeedReplace, &dev->flags);
+			rdev = rcu_dereference(conf->disks[i].rdev);
+			clear_bit(R5_ReadRepl, &dev->flags);
+		}
+		if (rdev && test_bit(Faulty, &rdev->flags))
+			rdev = NULL;
+		if (rdev) {
+			is_bad = is_badblock(rdev, sh->sector, RAID5_STRIPE_SECTORS(conf),
+					     &first_bad, &bad_sectors);
+			if (s->blocked_rdev == NULL
+			    && (test_bit(Blocked, &rdev->flags)
+				|| is_bad < 0)) {
+				if (is_bad < 0)
+					set_bit(BlockedBadBlocks,
+						&rdev->flags);
+				s->blocked_rdev = rdev;
+				atomic_inc(&rdev->nr_pending);
+			}
+		}
+		clear_bit(R5_Insync, &dev->flags);
+		if (!rdev)
+			/* Not in-sync */;
+		else if (is_bad) {
+			/* also not in-sync */
+			if (!test_bit(WriteErrorSeen, &rdev->flags) &&
+			    test_bit(R5_UPTODATE, &dev->flags)) {
+				/* treat as in-sync, but with a read error
+				 * which we can now try to correct
+				 */
+				set_bit(R5_Insync, &dev->flags);
+				set_bit(R5_ReadError, &dev->flags);
+			}
+		} else if (test_bit(In_sync, &rdev->flags))
+			set_bit(R5_Insync, &dev->flags);
+		else if (sh->sector + RAID5_STRIPE_SECTORS(conf) <= rdev->recovery_offset)
+			/* in sync if before recovery_offset */
+			set_bit(R5_Insync, &dev->flags);
+		else if (test_bit(R5_UPTODATE, &dev->flags) &&
+			 test_bit(R5_Expanded, &dev->flags))
+			/* If we've reshaped into here, we assume it is Insync.
+			 * We will shortly update recovery_offset to make
+			 * it official.
+			 */
+			set_bit(R5_Insync, &dev->flags);
+
+		if (test_bit(R5_WriteError, &dev->flags)) {
+			/* This flag does not apply to '.replacement'
+			 * only to .rdev, so make sure to check that*/
+			struct md_rdev *rdev2 = rcu_dereference(
+				conf->disks[i].rdev);
+			if (rdev2 == rdev)
+				clear_bit(R5_Insync, &dev->flags);
+			if (rdev2 && !test_bit(Faulty, &rdev2->flags)) {
+				s->handle_bad_blocks = 1;
+				atomic_inc(&rdev2->nr_pending);
+			} else
+				clear_bit(R5_WriteError, &dev->flags);
+		}
+		if (test_bit(R5_MadeGood, &dev->flags)) {
+			/* This flag does not apply to '.replacement'
+			 * only to .rdev, so make sure to check that*/
+			struct md_rdev *rdev2 = rcu_dereference(
+				conf->disks[i].rdev);
+			if (rdev2 && !test_bit(Faulty, &rdev2->flags)) {
+				s->handle_bad_blocks = 1;
+				atomic_inc(&rdev2->nr_pending);
+			} else
+				clear_bit(R5_MadeGood, &dev->flags);
+		}
+		if (test_bit(R5_MadeGoodRepl, &dev->flags)) {
+			struct md_rdev *rdev2 = rcu_dereference(
+				conf->disks[i].replacement);
+			if (rdev2 && !test_bit(Faulty, &rdev2->flags)) {
+				s->handle_bad_blocks = 1;
+				atomic_inc(&rdev2->nr_pending);
+			} else
+				clear_bit(R5_MadeGoodRepl, &dev->flags);
+		}
+		if (!test_bit(R5_Insync, &dev->flags)) {
+			/* The ReadError flag will just be confusing now */
+			clear_bit(R5_ReadError, &dev->flags);
+			clear_bit(R5_ReWrite, &dev->flags);
+		}
+		if (test_bit(R5_ReadError, &dev->flags))
+			clear_bit(R5_Insync, &dev->flags);
+		if (!test_bit(R5_Insync, &dev->flags)) {
+			if (s->failed < 2)
+				s->failed_num[s->failed] = i;
+			s->failed++;
+			if (rdev && !test_bit(Faulty, &rdev->flags))
+				do_recovery = 1;
+			else if (!rdev) {
+				rdev = rcu_dereference(
+				    conf->disks[i].replacement);
+				if (rdev && !test_bit(Faulty, &rdev->flags))
+					do_recovery = 1;
+			}
+		}
+
+		if (test_bit(R5_InJournal, &dev->flags))
+			s->injournal++;
+		if (test_bit(R5_InJournal, &dev->flags) && dev->written)
+			s->just_cached++;
+	}
+	if (test_bit(STRIPE_SYNCING, &sh->state)) {
+		/* If there is a failed device being replaced,
+		 *     we must be recovering.
+		 * else if we are after recovery_cp, we must be syncing
+		 * else if MD_RECOVERY_REQUESTED is set, we also are syncing.
+		 * else we can only be replacing
+		 * sync and recovery both need to read all devices, and so
+		 * use the same flag.
+		 */
+		if (do_recovery ||
+		    sh->sector >= conf->mddev->recovery_cp ||
+		    test_bit(MD_RECOVERY_REQUESTED, &(conf->mddev->recovery)))
+			s->syncing = 1;
+		else
+			s->replacing = 1;
+	}
+	rcu_read_unlock();
+}
+
+/*
+ * Return '1' if this is a member of batch, or '0' if it is a lone stripe or
+ * a head which can now be handled.
+ */
+static int clear_batch_ready(struct stripe_head *sh)
+{
+	struct stripe_head *tmp;
+	if (!test_and_clear_bit(STRIPE_BATCH_READY, &sh->state))
+		return (sh->batch_head && sh->batch_head != sh);
+	spin_lock(&sh->stripe_lock);
+	if (!sh->batch_head) {
+		spin_unlock(&sh->stripe_lock);
+		return 0;
+	}
+
+	/*
+	 * this stripe could be added to a batch list before we check
+	 * BATCH_READY, skips it
+	 */
+	if (sh->batch_head != sh) {
+		spin_unlock(&sh->stripe_lock);
+		return 1;
+	}
+	spin_lock(&sh->batch_lock);
+	list_for_each_entry(tmp, &sh->batch_list, batch_list)
+		clear_bit(STRIPE_BATCH_READY, &tmp->state);
+	spin_unlock(&sh->batch_lock);
+	spin_unlock(&sh->stripe_lock);
+
+	/*
+	 * BATCH_READY is cleared, no new stripes can be added.
+	 * batch_list can be accessed without lock
+	 */
+	return 0;
+}
+
+static void break_stripe_batch_list(struct stripe_head *head_sh,
+				    unsigned long handle_flags)
+{
+	struct stripe_head *sh, *next;
+	int i;
+	int do_wakeup = 0;
+
+	list_for_each_entry_safe(sh, next, &head_sh->batch_list, batch_list) {
+
+		list_del_init(&sh->batch_list);
+
+		WARN_ONCE(sh->state & ((1 << STRIPE_ACTIVE) |
+					  (1 << STRIPE_SYNCING) |
+					  (1 << STRIPE_REPLACED) |
+					  (1 << STRIPE_DELAYED) |
+					  (1 << STRIPE_BIT_DELAY) |
+					  (1 << STRIPE_FULL_WRITE) |
+					  (1 << STRIPE_BIOFILL_RUN) |
+					  (1 << STRIPE_COMPUTE_RUN)  |
+					  (1 << STRIPE_DISCARD) |
+					  (1 << STRIPE_BATCH_READY) |
+					  (1 << STRIPE_BATCH_ERR) |
+					  (1 << STRIPE_BITMAP_PENDING)),
+			"stripe state: %lx\n", sh->state);
+		WARN_ONCE(head_sh->state & ((1 << STRIPE_DISCARD) |
+					      (1 << STRIPE_REPLACED)),
+			"head stripe state: %lx\n", head_sh->state);
+
+		set_mask_bits(&sh->state, ~(STRIPE_EXPAND_SYNC_FLAGS |
+					    (1 << STRIPE_PREREAD_ACTIVE) |
+					    (1 << STRIPE_DEGRADED) |
+					    (1 << STRIPE_ON_UNPLUG_LIST)),
+			      head_sh->state & (1 << STRIPE_INSYNC));
+
+		sh->check_state = head_sh->check_state;
+		sh->reconstruct_state = head_sh->reconstruct_state;
+		spin_lock_irq(&sh->stripe_lock);
+		sh->batch_head = NULL;
+		spin_unlock_irq(&sh->stripe_lock);
+		for (i = 0; i < sh->disks; i++) {
+			if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
+				do_wakeup = 1;
+			sh->dev[i].flags = head_sh->dev[i].flags &
+				(~((1 << R5_WriteError) | (1 << R5_Overlap)));
+		}
+		if (handle_flags == 0 ||
+		    sh->state & handle_flags)
+			set_bit(STRIPE_HANDLE, &sh->state);
+		raid5_release_stripe(sh);
+	}
+	spin_lock_irq(&head_sh->stripe_lock);
+	head_sh->batch_head = NULL;
+	spin_unlock_irq(&head_sh->stripe_lock);
+	for (i = 0; i < head_sh->disks; i++)
+		if (test_and_clear_bit(R5_Overlap, &head_sh->dev[i].flags))
+			do_wakeup = 1;
+	if (head_sh->state & handle_flags)
+		set_bit(STRIPE_HANDLE, &head_sh->state);
+
+	if (do_wakeup)
+		wake_up(&head_sh->raid_conf->wait_for_overlap);
+}
+
+static void handle_stripe(struct stripe_head *sh)
+{
+	struct stripe_head_state s;
+	struct r5conf *conf = sh->raid_conf;
+	int i;
+	int prexor;
+	int disks = sh->disks;
+	struct r5dev *pdev, *qdev;
+
+	clear_bit(STRIPE_HANDLE, &sh->state);
+
+	/*
+	 * handle_stripe should not continue handle the batched stripe, only
+	 * the head of batch list or lone stripe can continue. Otherwise we
+	 * could see break_stripe_batch_list warns about the STRIPE_ACTIVE
+	 * is set for the batched stripe.
+	 */
+	if (clear_batch_ready(sh))
+		return;
+
+	if (test_and_set_bit_lock(STRIPE_ACTIVE, &sh->state)) {
+		/* already being handled, ensure it gets handled
+		 * again when current action finishes */
+		set_bit(STRIPE_HANDLE, &sh->state);
+		return;
+	}
+
+	if (test_and_clear_bit(STRIPE_BATCH_ERR, &sh->state))
+		break_stripe_batch_list(sh, 0);
+
+	if (test_bit(STRIPE_SYNC_REQUESTED, &sh->state) && !sh->batch_head) {
+		spin_lock(&sh->stripe_lock);
+		/*
+		 * Cannot process 'sync' concurrently with 'discard'.
+		 * Flush data in r5cache before 'sync'.
+		 */
+		if (!test_bit(STRIPE_R5C_PARTIAL_STRIPE, &sh->state) &&
+		    !test_bit(STRIPE_R5C_FULL_STRIPE, &sh->state) &&
+		    !test_bit(STRIPE_DISCARD, &sh->state) &&
+		    test_and_clear_bit(STRIPE_SYNC_REQUESTED, &sh->state)) {
+			set_bit(STRIPE_SYNCING, &sh->state);
+			clear_bit(STRIPE_INSYNC, &sh->state);
+			clear_bit(STRIPE_REPLACED, &sh->state);
+		}
+		spin_unlock(&sh->stripe_lock);
+	}
+	clear_bit(STRIPE_DELAYED, &sh->state);
+
+	pr_debug("handling stripe %llu, state=%#lx cnt=%d, "
+		"pd_idx=%d, qd_idx=%d\n, check:%d, reconstruct:%d\n",
+	       (unsigned long long)sh->sector, sh->state,
+	       atomic_read(&sh->count), sh->pd_idx, sh->qd_idx,
+	       sh->check_state, sh->reconstruct_state);
+
+	analyse_stripe(sh, &s);
+
+	if (test_bit(STRIPE_LOG_TRAPPED, &sh->state))
+		goto finish;
+
+	if (s.handle_bad_blocks ||
+	    test_bit(MD_SB_CHANGE_PENDING, &conf->mddev->sb_flags)) {
+		set_bit(STRIPE_HANDLE, &sh->state);
+		goto finish;
+	}
+
+	if (unlikely(s.blocked_rdev)) {
+		if (s.syncing || s.expanding || s.expanded ||
+		    s.replacing || s.to_write || s.written) {
+			set_bit(STRIPE_HANDLE, &sh->state);
+			goto finish;
+		}
+		/* There is nothing for the blocked_rdev to block */
+		rdev_dec_pending(s.blocked_rdev, conf->mddev);
+		s.blocked_rdev = NULL;
+	}
+
+	if (s.to_fill && !test_bit(STRIPE_BIOFILL_RUN, &sh->state)) {
+		set_bit(STRIPE_OP_BIOFILL, &s.ops_request);
+		set_bit(STRIPE_BIOFILL_RUN, &sh->state);
+	}
+
+	pr_debug("locked=%d uptodate=%d to_read=%d"
+	       " to_write=%d failed=%d failed_num=%d,%d\n",
+	       s.locked, s.uptodate, s.to_read, s.to_write, s.failed,
+	       s.failed_num[0], s.failed_num[1]);
+	/*
+	 * check if the array has lost more than max_degraded devices and,
+	 * if so, some requests might need to be failed.
+	 *
+	 * When journal device failed (log_failed), we will only process
+	 * the stripe if there is data need write to raid disks
+	 */
+	if (s.failed > conf->max_degraded ||
+	    (s.log_failed && s.injournal == 0)) {
+		sh->check_state = 0;
+		sh->reconstruct_state = 0;
+		break_stripe_batch_list(sh, 0);
+		if (s.to_read+s.to_write+s.written)
+			handle_failed_stripe(conf, sh, &s, disks);
+		if (s.syncing + s.replacing)
+			handle_failed_sync(conf, sh, &s);
+	}
+
+	/* Now we check to see if any write operations have recently
+	 * completed
+	 */
+	prexor = 0;
+	if (sh->reconstruct_state == reconstruct_state_prexor_drain_result)
+		prexor = 1;
+	if (sh->reconstruct_state == reconstruct_state_drain_result ||
+	    sh->reconstruct_state == reconstruct_state_prexor_drain_result) {
+		sh->reconstruct_state = reconstruct_state_idle;
+
+		/* All the 'written' buffers and the parity block are ready to
+		 * be written back to disk
+		 */
+		BUG_ON(!test_bit(R5_UPTODATE, &sh->dev[sh->pd_idx].flags) &&
+		       !test_bit(R5_Discard, &sh->dev[sh->pd_idx].flags));
+		BUG_ON(sh->qd_idx >= 0 &&
+		       !test_bit(R5_UPTODATE, &sh->dev[sh->qd_idx].flags) &&
+		       !test_bit(R5_Discard, &sh->dev[sh->qd_idx].flags));
+		for (i = disks; i--; ) {
+			struct r5dev *dev = &sh->dev[i];
+			if (test_bit(R5_LOCKED, &dev->flags) &&
+				(i == sh->pd_idx || i == sh->qd_idx ||
+				 dev->written || test_bit(R5_InJournal,
+							  &dev->flags))) {
+				pr_debug("Writing block %d\n", i);
+				set_bit(R5_Wantwrite, &dev->flags);
+				if (prexor)
+					continue;
+				if (s.failed > 1)
+					continue;
+				if (!test_bit(R5_Insync, &dev->flags) ||
+				    ((i == sh->pd_idx || i == sh->qd_idx)  &&
+				     s.failed == 0))
+					set_bit(STRIPE_INSYNC, &sh->state);
+			}
+		}
+		if (test_and_clear_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
+			s.dec_preread_active = 1;
+	}
+
+	/*
+	 * might be able to return some write requests if the parity blocks
+	 * are safe, or on a failed drive
+	 */
+	pdev = &sh->dev[sh->pd_idx];
+	s.p_failed = (s.failed >= 1 && s.failed_num[0] == sh->pd_idx)
+		|| (s.failed >= 2 && s.failed_num[1] == sh->pd_idx);
+	qdev = &sh->dev[sh->qd_idx];
+	s.q_failed = (s.failed >= 1 && s.failed_num[0] == sh->qd_idx)
+		|| (s.failed >= 2 && s.failed_num[1] == sh->qd_idx)
+		|| conf->level < 6;
+
+	if (s.written &&
+	    (s.p_failed || ((test_bit(R5_Insync, &pdev->flags)
+			     && !test_bit(R5_LOCKED, &pdev->flags)
+			     && (test_bit(R5_UPTODATE, &pdev->flags) ||
+				 test_bit(R5_Discard, &pdev->flags))))) &&
+	    (s.q_failed || ((test_bit(R5_Insync, &qdev->flags)
+			     && !test_bit(R5_LOCKED, &qdev->flags)
+			     && (test_bit(R5_UPTODATE, &qdev->flags) ||
+				 test_bit(R5_Discard, &qdev->flags))))))
+		handle_stripe_clean_event(conf, sh, disks);
+
+	if (s.just_cached)
+		r5c_handle_cached_data_endio(conf, sh, disks);
+	log_stripe_write_finished(sh);
+
+	/* Now we might consider reading some blocks, either to check/generate
+	 * parity, or to satisfy requests
+	 * or to load a block that is being partially written.
+	 */
+	if (s.to_read || s.non_overwrite
+	    || (s.to_write && s.failed)
+	    || (s.syncing && (s.uptodate + s.compute < disks))
+	    || s.replacing
+	    || s.expanding)
+		handle_stripe_fill(sh, &s, disks);
+
+	/*
+	 * When the stripe finishes full journal write cycle (write to journal
+	 * and raid disk), this is the clean up procedure so it is ready for
+	 * next operation.
+	 */
+	r5c_finish_stripe_write_out(conf, sh, &s);
+
+	/*
+	 * Now to consider new write requests, cache write back and what else,
+	 * if anything should be read.  We do not handle new writes when:
+	 * 1/ A 'write' operation (copy+xor) is already in flight.
+	 * 2/ A 'check' operation is in flight, as it may clobber the parity
+	 *    block.
+	 * 3/ A r5c cache log write is in flight.
+	 */
+
+	if (!sh->reconstruct_state && !sh->check_state && !sh->log_io) {
+		if (!r5c_is_writeback(conf->log)) {
+			if (s.to_write)
+				handle_stripe_dirtying(conf, sh, &s, disks);
+		} else { /* write back cache */
+			int ret = 0;
+
+			/* First, try handle writes in caching phase */
+			if (s.to_write)
+				ret = r5c_try_caching_write(conf, sh, &s,
+							    disks);
+			/*
+			 * If caching phase failed: ret == -EAGAIN
+			 *    OR
+			 * stripe under reclaim: !caching && injournal
+			 *
+			 * fall back to handle_stripe_dirtying()
+			 */
+			if (ret == -EAGAIN ||
+			    /* stripe under reclaim: !caching && injournal */
+			    (!test_bit(STRIPE_R5C_CACHING, &sh->state) &&
+			     s.injournal > 0)) {
+				ret = handle_stripe_dirtying(conf, sh, &s,
+							     disks);
+				if (ret == -EAGAIN)
+					goto finish;
+			}
+		}
+	}
+
+	/* maybe we need to check and possibly fix the parity for this stripe
+	 * Any reads will already have been scheduled, so we just see if enough
+	 * data is available.  The parity check is held off while parity
+	 * dependent operations are in flight.
+	 */
+	if (sh->check_state ||
+	    (s.syncing && s.locked == 0 &&
+	     !test_bit(STRIPE_COMPUTE_RUN, &sh->state) &&
+	     !test_bit(STRIPE_INSYNC, &sh->state))) {
+		if (conf->level == 6)
+			handle_parity_checks6(conf, sh, &s, disks);
+		else
+			handle_parity_checks5(conf, sh, &s, disks);
+	}
+
+	if ((s.replacing || s.syncing) && s.locked == 0
+	    && !test_bit(STRIPE_COMPUTE_RUN, &sh->state)
+	    && !test_bit(STRIPE_REPLACED, &sh->state)) {
+		/* Write out to replacement devices where possible */
+		for (i = 0; i < conf->raid_disks; i++)
+			if (test_bit(R5_NeedReplace, &sh->dev[i].flags)) {
+				WARN_ON(!test_bit(R5_UPTODATE, &sh->dev[i].flags));
+				set_bit(R5_WantReplace, &sh->dev[i].flags);
+				set_bit(R5_LOCKED, &sh->dev[i].flags);
+				s.locked++;
+			}
+		if (s.replacing)
+			set_bit(STRIPE_INSYNC, &sh->state);
+		set_bit(STRIPE_REPLACED, &sh->state);
+	}
+	if ((s.syncing || s.replacing) && s.locked == 0 &&
+	    !test_bit(STRIPE_COMPUTE_RUN, &sh->state) &&
+	    test_bit(STRIPE_INSYNC, &sh->state)) {
+		md_done_sync(conf->mddev, RAID5_STRIPE_SECTORS(conf), 1);
+		clear_bit(STRIPE_SYNCING, &sh->state);
+		if (test_and_clear_bit(R5_Overlap, &sh->dev[sh->pd_idx].flags))
+			wake_up(&conf->wait_for_overlap);
+	}
+
+	/* If the failed drives are just a ReadError, then we might need
+	 * to progress the repair/check process
+	 */
+	if (s.failed <= conf->max_degraded && !conf->mddev->ro)
+		for (i = 0; i < s.failed; i++) {
+			struct r5dev *dev = &sh->dev[s.failed_num[i]];
+			if (test_bit(R5_ReadError, &dev->flags)
+			    && !test_bit(R5_LOCKED, &dev->flags)
+			    && test_bit(R5_UPTODATE, &dev->flags)
+				) {
+				if (!test_bit(R5_ReWrite, &dev->flags)) {
+					set_bit(R5_Wantwrite, &dev->flags);
+					set_bit(R5_ReWrite, &dev->flags);
+				} else
+					/* let's read it back */
+					set_bit(R5_Wantread, &dev->flags);
+				set_bit(R5_LOCKED, &dev->flags);
+				s.locked++;
+			}
+		}
+
+	/* Finish reconstruct operations initiated by the expansion process */
+	if (sh->reconstruct_state == reconstruct_state_result) {
+		struct stripe_head *sh_src
+			= raid5_get_active_stripe(conf, NULL, sh->sector,
+					R5_GAS_PREVIOUS | R5_GAS_NOBLOCK |
+					R5_GAS_NOQUIESCE);
+		if (sh_src && test_bit(STRIPE_EXPAND_SOURCE, &sh_src->state)) {
+			/* sh cannot be written until sh_src has been read.
+			 * so arrange for sh to be delayed a little
+			 */
+			set_bit(STRIPE_DELAYED, &sh->state);
+			set_bit(STRIPE_HANDLE, &sh->state);
+			if (!test_and_set_bit(STRIPE_PREREAD_ACTIVE,
+					      &sh_src->state))
+				atomic_inc(&conf->preread_active_stripes);
+			raid5_release_stripe(sh_src);
+			goto finish;
+		}
+		if (sh_src)
+			raid5_release_stripe(sh_src);
+
+		sh->reconstruct_state = reconstruct_state_idle;
+		clear_bit(STRIPE_EXPANDING, &sh->state);
+		for (i = conf->raid_disks; i--; ) {
+			set_bit(R5_Wantwrite, &sh->dev[i].flags);
+			set_bit(R5_LOCKED, &sh->dev[i].flags);
+			s.locked++;
+		}
+	}
+
+	if (s.expanded && test_bit(STRIPE_EXPANDING, &sh->state) &&
+	    !sh->reconstruct_state) {
+		/* Need to write out all blocks after computing parity */
+		sh->disks = conf->raid_disks;
+		stripe_set_idx(sh->sector, conf, 0, sh);
+		schedule_reconstruction(sh, &s, 1, 1);
+	} else if (s.expanded && !sh->reconstruct_state && s.locked == 0) {
+		clear_bit(STRIPE_EXPAND_READY, &sh->state);
+		atomic_dec(&conf->reshape_stripes);
+		wake_up(&conf->wait_for_overlap);
+		md_done_sync(conf->mddev, RAID5_STRIPE_SECTORS(conf), 1);
+	}
+
+	if (s.expanding && s.locked == 0 &&
+	    !test_bit(STRIPE_COMPUTE_RUN, &sh->state))
+		handle_stripe_expansion(conf, sh);
+
+finish:
+	/* wait for this device to become unblocked */
+	if (unlikely(s.blocked_rdev)) {
+		if (conf->mddev->external)
+			md_wait_for_blocked_rdev(s.blocked_rdev,
+						 conf->mddev);
+		else
+			/* Internal metadata will immediately
+			 * be written by raid5d, so we don't
+			 * need to wait here.
+			 */
+			rdev_dec_pending(s.blocked_rdev,
+					 conf->mddev);
+	}
+
+	if (s.handle_bad_blocks)
+		for (i = disks; i--; ) {
+			struct md_rdev *rdev;
+			struct r5dev *dev = &sh->dev[i];
+			if (test_and_clear_bit(R5_WriteError, &dev->flags)) {
+				/* We own a safe reference to the rdev */
+				rdev = rdev_pend_deref(conf->disks[i].rdev);
+				if (!rdev_set_badblocks(rdev, sh->sector,
+							RAID5_STRIPE_SECTORS(conf), 0))
+					md_error(conf->mddev, rdev);
+				rdev_dec_pending(rdev, conf->mddev);
+			}
+			if (test_and_clear_bit(R5_MadeGood, &dev->flags)) {
+				rdev = rdev_pend_deref(conf->disks[i].rdev);
+				rdev_clear_badblocks(rdev, sh->sector,
+						     RAID5_STRIPE_SECTORS(conf), 0);
+				rdev_dec_pending(rdev, conf->mddev);
+			}
+			if (test_and_clear_bit(R5_MadeGoodRepl, &dev->flags)) {
+				rdev = rdev_pend_deref(conf->disks[i].replacement);
+				if (!rdev)
+					/* rdev have been moved down */
+					rdev = rdev_pend_deref(conf->disks[i].rdev);
+				rdev_clear_badblocks(rdev, sh->sector,
+						     RAID5_STRIPE_SECTORS(conf), 0);
+				rdev_dec_pending(rdev, conf->mddev);
+			}
+		}
+
+	if (s.ops_request)
+		raid_run_ops(sh, s.ops_request);
+
+	ops_run_io(sh, &s);
+
+	if (s.dec_preread_active) {
+		/* We delay this until after ops_run_io so that if make_request
+		 * is waiting on a flush, it won't continue until the writes
+		 * have actually been submitted.
+		 */
+		atomic_dec(&conf->preread_active_stripes);
+		if (atomic_read(&conf->preread_active_stripes) <
+		    IO_THRESHOLD)
+			md_wakeup_thread(conf->mddev->thread);
+	}
+
+	clear_bit_unlock(STRIPE_ACTIVE, &sh->state);
+}
+
+static void raid5_activate_delayed(struct r5conf *conf)
+	__must_hold(&conf->device_lock)
+{
+	if (atomic_read(&conf->preread_active_stripes) < IO_THRESHOLD) {
+		while (!list_empty(&conf->delayed_list)) {
+			struct list_head *l = conf->delayed_list.next;
+			struct stripe_head *sh;
+			sh = list_entry(l, struct stripe_head, lru);
+			list_del_init(l);
+			clear_bit(STRIPE_DELAYED, &sh->state);
+			if (!test_and_set_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
+				atomic_inc(&conf->preread_active_stripes);
+			list_add_tail(&sh->lru, &conf->hold_list);
+			raid5_wakeup_stripe_thread(sh);
+		}
+	}
+}
+
+static void activate_bit_delay(struct r5conf *conf,
+		struct list_head *temp_inactive_list)
+	__must_hold(&conf->device_lock)
+{
+	struct list_head head;
+	list_add(&head, &conf->bitmap_list);
+	list_del_init(&conf->bitmap_list);
+	while (!list_empty(&head)) {
+		struct stripe_head *sh = list_entry(head.next, struct stripe_head, lru);
+		int hash;
+		list_del_init(&sh->lru);
+		atomic_inc(&sh->count);
+		hash = sh->hash_lock_index;
+		__release_stripe(conf, sh, &temp_inactive_list[hash]);
+	}
+}
+
+static int in_chunk_boundary(struct mddev *mddev, struct bio *bio)
+{
+	struct r5conf *conf = mddev->private;
+	sector_t sector = bio->bi_iter.bi_sector;
+	unsigned int chunk_sectors;
+	unsigned int bio_sectors = bio_sectors(bio);
+
+	chunk_sectors = min(conf->chunk_sectors, conf->prev_chunk_sectors);
+	return  chunk_sectors >=
+		((sector & (chunk_sectors - 1)) + bio_sectors);
+}
+
+/*
+ *  add bio to the retry LIFO  ( in O(1) ... we are in interrupt )
+ *  later sampled by raid5d.
+ */
+static void add_bio_to_retry(struct bio *bi,struct r5conf *conf)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&conf->device_lock, flags);
+
+	bi->bi_next = conf->retry_read_aligned_list;
+	conf->retry_read_aligned_list = bi;
+
+	spin_unlock_irqrestore(&conf->device_lock, flags);
+	md_wakeup_thread(conf->mddev->thread);
+}
+
+static struct bio *remove_bio_from_retry(struct r5conf *conf,
+					 unsigned int *offset)
+{
+	struct bio *bi;
+
+	bi = conf->retry_read_aligned;
+	if (bi) {
+		*offset = conf->retry_read_offset;
+		conf->retry_read_aligned = NULL;
+		return bi;
+	}
+	bi = conf->retry_read_aligned_list;
+	if(bi) {
+		conf->retry_read_aligned_list = bi->bi_next;
+		bi->bi_next = NULL;
+		*offset = 0;
+	}
+
+	return bi;
+}
+
+/*
+ *  The "raid5_align_endio" should check if the read succeeded and if it
+ *  did, call bio_endio on the original bio (having bio_put the new bio
+ *  first).
+ *  If the read failed..
+ */
+static void raid5_align_endio(struct bio *bi)
+{
+	struct bio *raid_bi = bi->bi_private;
+	struct md_rdev *rdev = (void *)raid_bi->bi_next;
+	struct mddev *mddev = rdev->mddev;
+	struct r5conf *conf = mddev->private;
+	blk_status_t error = bi->bi_status;
+
+	bio_put(bi);
+	raid_bi->bi_next = NULL;
+	rdev_dec_pending(rdev, conf->mddev);
+
+	if (!error) {
+		bio_endio(raid_bi);
+		if (atomic_dec_and_test(&conf->active_aligned_reads))
+			wake_up(&conf->wait_for_quiescent);
+		return;
+	}
+
+	pr_debug("raid5_align_endio : io error...handing IO for a retry\n");
+
+	add_bio_to_retry(raid_bi, conf);
+}
+
+static int raid5_read_one_chunk(struct mddev *mddev, struct bio *raid_bio)
+{
+	struct r5conf *conf = mddev->private;
+	struct bio *align_bio;
+	struct md_rdev *rdev;
+	sector_t sector, end_sector, first_bad;
+	int bad_sectors, dd_idx;
+	bool did_inc;
+
+	if (!in_chunk_boundary(mddev, raid_bio)) {
+		pr_debug("%s: non aligned\n", __func__);
+		return 0;
+	}
+
+	sector = raid5_compute_sector(conf, raid_bio->bi_iter.bi_sector, 0,
+				      &dd_idx, NULL);
+	end_sector = sector + bio_sectors(raid_bio);
+
+	rcu_read_lock();
+	if (r5c_big_stripe_cached(conf, sector))
+		goto out_rcu_unlock;
+
+	rdev = rcu_dereference(conf->disks[dd_idx].replacement);
+	if (!rdev || test_bit(Faulty, &rdev->flags) ||
+	    rdev->recovery_offset < end_sector) {
+		rdev = rcu_dereference(conf->disks[dd_idx].rdev);
+		if (!rdev)
+			goto out_rcu_unlock;
+		if (test_bit(Faulty, &rdev->flags) ||
+		    !(test_bit(In_sync, &rdev->flags) ||
+		      rdev->recovery_offset >= end_sector))
+			goto out_rcu_unlock;
+	}
+
+	atomic_inc(&rdev->nr_pending);
+	rcu_read_unlock();
+
+	if (is_badblock(rdev, sector, bio_sectors(raid_bio), &first_bad,
+			&bad_sectors)) {
+		rdev_dec_pending(rdev, mddev);
+		return 0;
+	}
+
+	md_account_bio(mddev, &raid_bio);
+	raid_bio->bi_next = (void *)rdev;
+
+	align_bio = bio_alloc_clone(rdev->bdev, raid_bio, GFP_NOIO,
+				    &mddev->bio_set);
+	align_bio->bi_end_io = raid5_align_endio;
+	align_bio->bi_private = raid_bio;
+	align_bio->bi_iter.bi_sector = sector;
+
+	/* No reshape active, so we can trust rdev->data_offset */
+	align_bio->bi_iter.bi_sector += rdev->data_offset;
+
+	did_inc = false;
+	if (conf->quiesce == 0) {
+		atomic_inc(&conf->active_aligned_reads);
+		did_inc = true;
+	}
+	/* need a memory barrier to detect the race with raid5_quiesce() */
+	if (!did_inc || smp_load_acquire(&conf->quiesce) != 0) {
+		/* quiesce is in progress, so we need to undo io activation and wait
+		 * for it to finish
+		 */
+		if (did_inc && atomic_dec_and_test(&conf->active_aligned_reads))
+			wake_up(&conf->wait_for_quiescent);
+		spin_lock_irq(&conf->device_lock);
+		wait_event_lock_irq(conf->wait_for_quiescent, conf->quiesce == 0,
+				    conf->device_lock);
+		atomic_inc(&conf->active_aligned_reads);
+		spin_unlock_irq(&conf->device_lock);
+	}
+
+	if (mddev->gendisk)
+		trace_block_bio_remap(align_bio, disk_devt(mddev->gendisk),
+				      raid_bio->bi_iter.bi_sector);
+	submit_bio_noacct(align_bio);
+	return 1;
+
+out_rcu_unlock:
+	rcu_read_unlock();
+	return 0;
+}
+
+static struct bio *chunk_aligned_read(struct mddev *mddev, struct bio *raid_bio)
+{
+	struct bio *split;
+	sector_t sector = raid_bio->bi_iter.bi_sector;
+	unsigned chunk_sects = mddev->chunk_sectors;
+	unsigned sectors = chunk_sects - (sector & (chunk_sects-1));
+
+	if (sectors < bio_sectors(raid_bio)) {
+		struct r5conf *conf = mddev->private;
+		split = bio_split(raid_bio, sectors, GFP_NOIO, &conf->bio_split);
+		bio_chain(split, raid_bio);
+		submit_bio_noacct(raid_bio);
+		raid_bio = split;
+	}
+
+	if (!raid5_read_one_chunk(mddev, raid_bio))
+		return raid_bio;
+
+	return NULL;
+}
+
+/* __get_priority_stripe - get the next stripe to process
+ *
+ * Full stripe writes are allowed to pass preread active stripes up until
+ * the bypass_threshold is exceeded.  In general the bypass_count
+ * increments when the handle_list is handled before the hold_list; however, it
+ * will not be incremented when STRIPE_IO_STARTED is sampled set signifying a
+ * stripe with in flight i/o.  The bypass_count will be reset when the
+ * head of the hold_list has changed, i.e. the head was promoted to the
+ * handle_list.
+ */
+static struct stripe_head *__get_priority_stripe(struct r5conf *conf, int group)
+	__must_hold(&conf->device_lock)
+{
+	struct stripe_head *sh, *tmp;
+	struct list_head *handle_list = NULL;
+	struct r5worker_group *wg;
+	bool second_try = !r5c_is_writeback(conf->log) &&
+		!r5l_log_disk_error(conf);
+	bool try_loprio = test_bit(R5C_LOG_TIGHT, &conf->cache_state) ||
+		r5l_log_disk_error(conf);
+
+again:
+	wg = NULL;
+	sh = NULL;
+	if (conf->worker_cnt_per_group == 0) {
+		handle_list = try_loprio ? &conf->loprio_list :
+					&conf->handle_list;
+	} else if (group != ANY_GROUP) {
+		handle_list = try_loprio ? &conf->worker_groups[group].loprio_list :
+				&conf->worker_groups[group].handle_list;
+		wg = &conf->worker_groups[group];
+	} else {
+		int i;
+		for (i = 0; i < conf->group_cnt; i++) {
+			handle_list = try_loprio ? &conf->worker_groups[i].loprio_list :
+				&conf->worker_groups[i].handle_list;
+			wg = &conf->worker_groups[i];
+			if (!list_empty(handle_list))
+				break;
+		}
+	}
+
+	pr_debug("%s: handle: %s hold: %s full_writes: %d bypass_count: %d\n",
+		  __func__,
+		  list_empty(handle_list) ? "empty" : "busy",
+		  list_empty(&conf->hold_list) ? "empty" : "busy",
+		  atomic_read(&conf->pending_full_writes), conf->bypass_count);
+
+	if (!list_empty(handle_list)) {
+		sh = list_entry(handle_list->next, typeof(*sh), lru);
+
+		if (list_empty(&conf->hold_list))
+			conf->bypass_count = 0;
+		else if (!test_bit(STRIPE_IO_STARTED, &sh->state)) {
+			if (conf->hold_list.next == conf->last_hold)
+				conf->bypass_count++;
+			else {
+				conf->last_hold = conf->hold_list.next;
+				conf->bypass_count -= conf->bypass_threshold;
+				if (conf->bypass_count < 0)
+					conf->bypass_count = 0;
+			}
+		}
+	} else if (!list_empty(&conf->hold_list) &&
+		   ((conf->bypass_threshold &&
+		     conf->bypass_count > conf->bypass_threshold) ||
+		    atomic_read(&conf->pending_full_writes) == 0)) {
+
+		list_for_each_entry(tmp, &conf->hold_list,  lru) {
+			if (conf->worker_cnt_per_group == 0 ||
+			    group == ANY_GROUP ||
+			    !cpu_online(tmp->cpu) ||
+			    cpu_to_group(tmp->cpu) == group) {
+				sh = tmp;
+				break;
+			}
+		}
+
+		if (sh) {
+			conf->bypass_count -= conf->bypass_threshold;
+			if (conf->bypass_count < 0)
+				conf->bypass_count = 0;
+		}
+		wg = NULL;
+	}
+
+	if (!sh) {
+		if (second_try)
+			return NULL;
+		second_try = true;
+		try_loprio = !try_loprio;
+		goto again;
+	}
+
+	if (wg) {
+		wg->stripes_cnt--;
+		sh->group = NULL;
+	}
+	list_del_init(&sh->lru);
+	BUG_ON(atomic_inc_return(&sh->count) != 1);
+	return sh;
+}
+
+struct raid5_plug_cb {
+	struct blk_plug_cb	cb;
+	struct list_head	list;
+	struct list_head	temp_inactive_list[NR_STRIPE_HASH_LOCKS];
+};
+
+static void raid5_unplug(struct blk_plug_cb *blk_cb, bool from_schedule)
+{
+	struct raid5_plug_cb *cb = container_of(
+		blk_cb, struct raid5_plug_cb, cb);
+	struct stripe_head *sh;
+	struct mddev *mddev = cb->cb.data;
+	struct r5conf *conf = mddev->private;
+	int cnt = 0;
+	int hash;
+
+	if (cb->list.next && !list_empty(&cb->list)) {
+		spin_lock_irq(&conf->device_lock);
+		while (!list_empty(&cb->list)) {
+			sh = list_first_entry(&cb->list, struct stripe_head, lru);
+			list_del_init(&sh->lru);
+			/*
+			 * avoid race release_stripe_plug() sees
+			 * STRIPE_ON_UNPLUG_LIST clear but the stripe
+			 * is still in our list
+			 */
+			smp_mb__before_atomic();
+			clear_bit(STRIPE_ON_UNPLUG_LIST, &sh->state);
+			/*
+			 * STRIPE_ON_RELEASE_LIST could be set here. In that
+			 * case, the count is always > 1 here
+			 */
+			hash = sh->hash_lock_index;
+			__release_stripe(conf, sh, &cb->temp_inactive_list[hash]);
+			cnt++;
+		}
+		spin_unlock_irq(&conf->device_lock);
+	}
+	release_inactive_stripe_list(conf, cb->temp_inactive_list,
+				     NR_STRIPE_HASH_LOCKS);
+	if (mddev->queue)
+		trace_block_unplug(mddev->queue, cnt, !from_schedule);
+	kfree(cb);
+}
+
+static void release_stripe_plug(struct mddev *mddev,
+				struct stripe_head *sh)
+{
+	struct blk_plug_cb *blk_cb = blk_check_plugged(
+		raid5_unplug, mddev,
+		sizeof(struct raid5_plug_cb));
+	struct raid5_plug_cb *cb;
+
+	if (!blk_cb) {
+		raid5_release_stripe(sh);
+		return;
+	}
+
+	cb = container_of(blk_cb, struct raid5_plug_cb, cb);
+
+	if (cb->list.next == NULL) {
+		int i;
+		INIT_LIST_HEAD(&cb->list);
+		for (i = 0; i < NR_STRIPE_HASH_LOCKS; i++)
+			INIT_LIST_HEAD(cb->temp_inactive_list + i);
+	}
+
+	if (!test_and_set_bit(STRIPE_ON_UNPLUG_LIST, &sh->state))
+		list_add_tail(&sh->lru, &cb->list);
+	else
+		raid5_release_stripe(sh);
+}
+
+static void make_discard_request(struct mddev *mddev, struct bio *bi)
+{
+	struct r5conf *conf = mddev->private;
+	sector_t logical_sector, last_sector;
+	struct stripe_head *sh;
+	int stripe_sectors;
+
+	/* We need to handle this when io_uring supports discard/trim */
+	if (WARN_ON_ONCE(bi->bi_opf & REQ_NOWAIT))
+		return;
+
+	if (mddev->reshape_position != MaxSector)
+		/* Skip discard while reshape is happening */
+		return;
+
+	logical_sector = bi->bi_iter.bi_sector & ~((sector_t)RAID5_STRIPE_SECTORS(conf)-1);
+	last_sector = bio_end_sector(bi);
+
+	bi->bi_next = NULL;
+
+	stripe_sectors = conf->chunk_sectors *
+		(conf->raid_disks - conf->max_degraded);
+	logical_sector = DIV_ROUND_UP_SECTOR_T(logical_sector,
+					       stripe_sectors);
+	sector_div(last_sector, stripe_sectors);
+
+	logical_sector *= conf->chunk_sectors;
+	last_sector *= conf->chunk_sectors;
+
+	for (; logical_sector < last_sector;
+	     logical_sector += RAID5_STRIPE_SECTORS(conf)) {
+		DEFINE_WAIT(w);
+		int d;
+	again:
+		sh = raid5_get_active_stripe(conf, NULL, logical_sector, 0);
+		prepare_to_wait(&conf->wait_for_overlap, &w,
+				TASK_UNINTERRUPTIBLE);
+		set_bit(R5_Overlap, &sh->dev[sh->pd_idx].flags);
+		if (test_bit(STRIPE_SYNCING, &sh->state)) {
+			raid5_release_stripe(sh);
+			schedule();
+			goto again;
+		}
+		clear_bit(R5_Overlap, &sh->dev[sh->pd_idx].flags);
+		spin_lock_irq(&sh->stripe_lock);
+		for (d = 0; d < conf->raid_disks; d++) {
+			if (d == sh->pd_idx || d == sh->qd_idx)
+				continue;
+			if (sh->dev[d].towrite || sh->dev[d].toread) {
+				set_bit(R5_Overlap, &sh->dev[d].flags);
+				spin_unlock_irq(&sh->stripe_lock);
+				raid5_release_stripe(sh);
+				schedule();
+				goto again;
+			}
+		}
+		set_bit(STRIPE_DISCARD, &sh->state);
+		finish_wait(&conf->wait_for_overlap, &w);
+		sh->overwrite_disks = 0;
+		for (d = 0; d < conf->raid_disks; d++) {
+			if (d == sh->pd_idx || d == sh->qd_idx)
+				continue;
+			sh->dev[d].towrite = bi;
+			set_bit(R5_OVERWRITE, &sh->dev[d].flags);
+			bio_inc_remaining(bi);
+			md_write_inc(mddev, bi);
+			sh->overwrite_disks++;
+		}
+		spin_unlock_irq(&sh->stripe_lock);
+		if (conf->mddev->bitmap) {
+			for (d = 0;
+			     d < conf->raid_disks - conf->max_degraded;
+			     d++)
+				md_bitmap_startwrite(mddev->bitmap,
+						     sh->sector,
+						     RAID5_STRIPE_SECTORS(conf),
+						     0);
+			sh->bm_seq = conf->seq_flush + 1;
+			set_bit(STRIPE_BIT_DELAY, &sh->state);
+		}
+
+		set_bit(STRIPE_HANDLE, &sh->state);
+		clear_bit(STRIPE_DELAYED, &sh->state);
+		if (!test_and_set_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
+			atomic_inc(&conf->preread_active_stripes);
+		release_stripe_plug(mddev, sh);
+	}
+
+	bio_endio(bi);
+}
+
+static bool ahead_of_reshape(struct mddev *mddev, sector_t sector,
+			     sector_t reshape_sector)
+{
+	return mddev->reshape_backwards ? sector < reshape_sector :
+					  sector >= reshape_sector;
+}
+
+static bool range_ahead_of_reshape(struct mddev *mddev, sector_t min,
+				   sector_t max, sector_t reshape_sector)
+{
+	return mddev->reshape_backwards ? max < reshape_sector :
+					  min >= reshape_sector;
+}
+
+static bool stripe_ahead_of_reshape(struct mddev *mddev, struct r5conf *conf,
+				    struct stripe_head *sh)
+{
+	sector_t max_sector = 0, min_sector = MaxSector;
+	bool ret = false;
+	int dd_idx;
+
+	for (dd_idx = 0; dd_idx < sh->disks; dd_idx++) {
+		if (dd_idx == sh->pd_idx || dd_idx == sh->qd_idx)
+			continue;
+
+		min_sector = min(min_sector, sh->dev[dd_idx].sector);
+		max_sector = max(max_sector, sh->dev[dd_idx].sector);
+	}
+
+	spin_lock_irq(&conf->device_lock);
+
+	if (!range_ahead_of_reshape(mddev, min_sector, max_sector,
+				     conf->reshape_progress))
+		/* mismatch, need to try again */
+		ret = true;
+
+	spin_unlock_irq(&conf->device_lock);
+
+	return ret;
+}
+
+static int add_all_stripe_bios(struct r5conf *conf,
+		struct stripe_request_ctx *ctx, struct stripe_head *sh,
+		struct bio *bi, int forwrite, int previous)
+{
+	int dd_idx;
+	int ret = 1;
+
+	spin_lock_irq(&sh->stripe_lock);
+
+	for (dd_idx = 0; dd_idx < sh->disks; dd_idx++) {
+		struct r5dev *dev = &sh->dev[dd_idx];
+
+		if (dd_idx == sh->pd_idx || dd_idx == sh->qd_idx)
+			continue;
+
+		if (dev->sector < ctx->first_sector ||
+		    dev->sector >= ctx->last_sector)
+			continue;
+
+		if (stripe_bio_overlaps(sh, bi, dd_idx, forwrite)) {
+			set_bit(R5_Overlap, &dev->flags);
+			ret = 0;
+			continue;
+		}
+	}
+
+	if (!ret)
+		goto out;
+
+	for (dd_idx = 0; dd_idx < sh->disks; dd_idx++) {
+		struct r5dev *dev = &sh->dev[dd_idx];
+
+		if (dd_idx == sh->pd_idx || dd_idx == sh->qd_idx)
+			continue;
+
+		if (dev->sector < ctx->first_sector ||
+		    dev->sector >= ctx->last_sector)
+			continue;
+
+		__add_stripe_bio(sh, bi, dd_idx, forwrite, previous);
+		clear_bit((dev->sector - ctx->first_sector) >>
+			  RAID5_STRIPE_SHIFT(conf), ctx->sectors_to_do);
+	}
+
+out:
+	spin_unlock_irq(&sh->stripe_lock);
+	return ret;
+}
+
+static bool reshape_inprogress(struct mddev *mddev)
+{
+	return test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery) &&
+	       test_bit(MD_RECOVERY_RUNNING, &mddev->recovery) &&
+	       !test_bit(MD_RECOVERY_DONE, &mddev->recovery) &&
+	       !test_bit(MD_RECOVERY_INTR, &mddev->recovery);
+}
+
+static bool reshape_disabled(struct mddev *mddev)
+{
+	return is_md_suspended(mddev) || !md_is_rdwr(mddev);
+}
+
+static enum stripe_result make_stripe_request(struct mddev *mddev,
+		struct r5conf *conf, struct stripe_request_ctx *ctx,
+		sector_t logical_sector, struct bio *bi)
+{
+	const int rw = bio_data_dir(bi);
+	enum stripe_result ret;
+	struct stripe_head *sh;
+	sector_t new_sector;
+	int previous = 0, flags = 0;
+	int seq, dd_idx;
+
+	seq = read_seqcount_begin(&conf->gen_lock);
+
+	if (unlikely(conf->reshape_progress != MaxSector)) {
+		/*
+		 * Spinlock is needed as reshape_progress may be
+		 * 64bit on a 32bit platform, and so it might be
+		 * possible to see a half-updated value
+		 * Of course reshape_progress could change after
+		 * the lock is dropped, so once we get a reference
+		 * to the stripe that we think it is, we will have
+		 * to check again.
+		 */
+		spin_lock_irq(&conf->device_lock);
+		if (ahead_of_reshape(mddev, logical_sector,
+				     conf->reshape_progress)) {
+			previous = 1;
+		} else {
+			if (ahead_of_reshape(mddev, logical_sector,
+					     conf->reshape_safe)) {
+				spin_unlock_irq(&conf->device_lock);
+				ret = STRIPE_SCHEDULE_AND_RETRY;
+				goto out;
+			}
+		}
+		spin_unlock_irq(&conf->device_lock);
+	}
+
+	new_sector = raid5_compute_sector(conf, logical_sector, previous,
+					  &dd_idx, NULL);
+	pr_debug("raid456: %s, sector %llu logical %llu\n", __func__,
+		 new_sector, logical_sector);
+
+	if (previous)
+		flags |= R5_GAS_PREVIOUS;
+	if (bi->bi_opf & REQ_RAHEAD)
+		flags |= R5_GAS_NOBLOCK;
+	sh = raid5_get_active_stripe(conf, ctx, new_sector, flags);
+	if (unlikely(!sh)) {
+		/* cannot get stripe, just give-up */
+		bi->bi_status = BLK_STS_IOERR;
+		return STRIPE_FAIL;
+	}
+
+	if (unlikely(previous) &&
+	    stripe_ahead_of_reshape(mddev, conf, sh)) {
+		/*
+		 * Expansion moved on while waiting for a stripe.
+		 * Expansion could still move past after this
+		 * test, but as we are holding a reference to
+		 * 'sh', we know that if that happens,
+		 *  STRIPE_EXPANDING will get set and the expansion
+		 * won't proceed until we finish with the stripe.
+		 */
+		ret = STRIPE_SCHEDULE_AND_RETRY;
+		goto out_release;
+	}
+
+	if (read_seqcount_retry(&conf->gen_lock, seq)) {
+		/* Might have got the wrong stripe_head by accident */
+		ret = STRIPE_RETRY;
+		goto out_release;
+	}
+
+	if (test_bit(STRIPE_EXPANDING, &sh->state) ||
+	    !add_all_stripe_bios(conf, ctx, sh, bi, rw, previous)) {
+		/*
+		 * Stripe is busy expanding or add failed due to
+		 * overlap. Flush everything and wait a while.
+		 */
+		md_wakeup_thread(mddev->thread);
+		ret = STRIPE_SCHEDULE_AND_RETRY;
+		goto out_release;
+	}
+
+	if (stripe_can_batch(sh)) {
+		stripe_add_to_batch_list(conf, sh, ctx->batch_last);
+		if (ctx->batch_last)
+			raid5_release_stripe(ctx->batch_last);
+		atomic_inc(&sh->count);
+		ctx->batch_last = sh;
+	}
+
+	if (ctx->do_flush) {
+		set_bit(STRIPE_R5C_PREFLUSH, &sh->state);
+		/* we only need flush for one stripe */
+		ctx->do_flush = false;
+	}
+
+	set_bit(STRIPE_HANDLE, &sh->state);
+	clear_bit(STRIPE_DELAYED, &sh->state);
+	if ((!sh->batch_head || sh == sh->batch_head) &&
+	    (bi->bi_opf & REQ_SYNC) &&
+	    !test_and_set_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
+		atomic_inc(&conf->preread_active_stripes);
+
+	release_stripe_plug(mddev, sh);
+	return STRIPE_SUCCESS;
+
+out_release:
+	raid5_release_stripe(sh);
+out:
+	if (ret == STRIPE_SCHEDULE_AND_RETRY && !reshape_inprogress(mddev) &&
+	    reshape_disabled(mddev)) {
+		bi->bi_status = BLK_STS_IOERR;
+		ret = STRIPE_FAIL;
+		pr_err("md/raid456:%s: io failed across reshape position while reshape can't make progress.\n",
+		       mdname(mddev));
+	}
+
+	return ret;
+}
+
+/*
+ * If the bio covers multiple data disks, find sector within the bio that has
+ * the lowest chunk offset in the first chunk.
+ */
+static sector_t raid5_bio_lowest_chunk_sector(struct r5conf *conf,
+					      struct bio *bi)
+{
+	int sectors_per_chunk = conf->chunk_sectors;
+	int raid_disks = conf->raid_disks;
+	int dd_idx;
+	struct stripe_head sh;
+	unsigned int chunk_offset;
+	sector_t r_sector = bi->bi_iter.bi_sector & ~((sector_t)RAID5_STRIPE_SECTORS(conf)-1);
+	sector_t sector;
+
+	/* We pass in fake stripe_head to get back parity disk numbers */
+	sector = raid5_compute_sector(conf, r_sector, 0, &dd_idx, &sh);
+	chunk_offset = sector_div(sector, sectors_per_chunk);
+	if (sectors_per_chunk - chunk_offset >= bio_sectors(bi))
+		return r_sector;
+	/*
+	 * Bio crosses to the next data disk. Check whether it's in the same
+	 * chunk.
+	 */
+	dd_idx++;
+	while (dd_idx == sh.pd_idx || dd_idx == sh.qd_idx)
+		dd_idx++;
+	if (dd_idx >= raid_disks)
+		return r_sector;
+	return r_sector + sectors_per_chunk - chunk_offset;
+}
+
+static bool raid5_make_request(struct mddev *mddev, struct bio * bi)
+{
+	DEFINE_WAIT_FUNC(wait, woken_wake_function);
+	struct r5conf *conf = mddev->private;
+	sector_t logical_sector;
+	struct stripe_request_ctx ctx = {};
+	const int rw = bio_data_dir(bi);
+	enum stripe_result res;
+	int s, stripe_cnt;
+
+	if (unlikely(bi->bi_opf & REQ_PREFLUSH)) {
+		int ret = log_handle_flush_request(conf, bi);
+
+		if (ret == 0)
+			return true;
+		if (ret == -ENODEV) {
+			if (md_flush_request(mddev, bi))
+				return true;
+		}
+		/* ret == -EAGAIN, fallback */
+		/*
+		 * if r5l_handle_flush_request() didn't clear REQ_PREFLUSH,
+		 * we need to flush journal device
+		 */
+		ctx.do_flush = bi->bi_opf & REQ_PREFLUSH;
+	}
+
+	if (!md_write_start(mddev, bi))
+		return false;
+	/*
+	 * If array is degraded, better not do chunk aligned read because
+	 * later we might have to read it again in order to reconstruct
+	 * data on failed drives.
+	 */
+	if (rw == READ && mddev->degraded == 0 &&
+	    mddev->reshape_position == MaxSector) {
+		bi = chunk_aligned_read(mddev, bi);
+		if (!bi)
+			return true;
+	}
+
+	if (unlikely(bio_op(bi) == REQ_OP_DISCARD)) {
+		make_discard_request(mddev, bi);
+		md_write_end(mddev);
+		return true;
+	}
+
+	logical_sector = bi->bi_iter.bi_sector & ~((sector_t)RAID5_STRIPE_SECTORS(conf)-1);
+	ctx.first_sector = logical_sector;
+	ctx.last_sector = bio_end_sector(bi);
+	bi->bi_next = NULL;
+
+	stripe_cnt = DIV_ROUND_UP_SECTOR_T(ctx.last_sector - logical_sector,
+					   RAID5_STRIPE_SECTORS(conf));
+	bitmap_set(ctx.sectors_to_do, 0, stripe_cnt);
+
+	pr_debug("raid456: %s, logical %llu to %llu\n", __func__,
+		 bi->bi_iter.bi_sector, ctx.last_sector);
+
+	/* Bail out if conflicts with reshape and REQ_NOWAIT is set */
+	if ((bi->bi_opf & REQ_NOWAIT) &&
+	    (conf->reshape_progress != MaxSector) &&
+	    !ahead_of_reshape(mddev, logical_sector, conf->reshape_progress) &&
+	    ahead_of_reshape(mddev, logical_sector, conf->reshape_safe)) {
+		bio_wouldblock_error(bi);
+		if (rw == WRITE)
+			md_write_end(mddev);
+		return true;
+	}
+	md_account_bio(mddev, &bi);
+
+	/*
+	 * Lets start with the stripe with the lowest chunk offset in the first
+	 * chunk. That has the best chances of creating IOs adjacent to
+	 * previous IOs in case of sequential IO and thus creates the most
+	 * sequential IO pattern. We don't bother with the optimization when
+	 * reshaping as the performance benefit is not worth the complexity.
+	 */
+	if (likely(conf->reshape_progress == MaxSector))
+		logical_sector = raid5_bio_lowest_chunk_sector(conf, bi);
+	s = (logical_sector - ctx.first_sector) >> RAID5_STRIPE_SHIFT(conf);
+
+	add_wait_queue(&conf->wait_for_overlap, &wait);
+	while (1) {
+		res = make_stripe_request(mddev, conf, &ctx, logical_sector,
+					  bi);
+		if (res == STRIPE_FAIL)
+			break;
+
+		if (res == STRIPE_RETRY)
+			continue;
+
+		if (res == STRIPE_SCHEDULE_AND_RETRY) {
+			/*
+			 * Must release the reference to batch_last before
+			 * scheduling and waiting for work to be done,
+			 * otherwise the batch_last stripe head could prevent
+			 * raid5_activate_delayed() from making progress
+			 * and thus deadlocking.
+			 */
+			if (ctx.batch_last) {
+				raid5_release_stripe(ctx.batch_last);
+				ctx.batch_last = NULL;
+			}
+
+			wait_woken(&wait, TASK_UNINTERRUPTIBLE,
+				   MAX_SCHEDULE_TIMEOUT);
+			continue;
+		}
+
+		s = find_next_bit_wrap(ctx.sectors_to_do, stripe_cnt, s);
+		if (s == stripe_cnt)
+			break;
+
+		logical_sector = ctx.first_sector +
+			(s << RAID5_STRIPE_SHIFT(conf));
+	}
+	remove_wait_queue(&conf->wait_for_overlap, &wait);
+
+	if (ctx.batch_last)
+		raid5_release_stripe(ctx.batch_last);
+
+	if (rw == WRITE)
+		md_write_end(mddev);
+	bio_endio(bi);
+	return true;
+}
+
+static sector_t raid5_size(struct mddev *mddev, sector_t sectors, int raid_disks);
+
+static sector_t reshape_request(struct mddev *mddev, sector_t sector_nr, int *skipped)
+{
+	/* reshaping is quite different to recovery/resync so it is
+	 * handled quite separately ... here.
+	 *
+	 * On each call to sync_request, we gather one chunk worth of
+	 * destination stripes and flag them as expanding.
+	 * Then we find all the source stripes and request reads.
+	 * As the reads complete, handle_stripe will copy the data
+	 * into the destination stripe and release that stripe.
+	 */
+	struct r5conf *conf = mddev->private;
+	struct stripe_head *sh;
+	struct md_rdev *rdev;
+	sector_t first_sector, last_sector;
+	int raid_disks = conf->previous_raid_disks;
+	int data_disks = raid_disks - conf->max_degraded;
+	int new_data_disks = conf->raid_disks - conf->max_degraded;
+	int i;
+	int dd_idx;
+	sector_t writepos, readpos, safepos;
+	sector_t stripe_addr;
+	int reshape_sectors;
+	struct list_head stripes;
+	sector_t retn;
+
+	if (sector_nr == 0) {
+		/* If restarting in the middle, skip the initial sectors */
+		if (mddev->reshape_backwards &&
+		    conf->reshape_progress < raid5_size(mddev, 0, 0)) {
+			sector_nr = raid5_size(mddev, 0, 0)
+				- conf->reshape_progress;
+		} else if (mddev->reshape_backwards &&
+			   conf->reshape_progress == MaxSector) {
+			/* shouldn't happen, but just in case, finish up.*/
+			sector_nr = MaxSector;
+		} else if (!mddev->reshape_backwards &&
+			   conf->reshape_progress > 0)
+			sector_nr = conf->reshape_progress;
+		sector_div(sector_nr, new_data_disks);
+		if (sector_nr) {
+			mddev->curr_resync_completed = sector_nr;
+			sysfs_notify_dirent_safe(mddev->sysfs_completed);
+			*skipped = 1;
+			retn = sector_nr;
+			goto finish;
+		}
+	}
+
+	/* We need to process a full chunk at a time.
+	 * If old and new chunk sizes differ, we need to process the
+	 * largest of these
+	 */
+
+	reshape_sectors = max(conf->chunk_sectors, conf->prev_chunk_sectors);
+
+	/* We update the metadata at least every 10 seconds, or when
+	 * the data about to be copied would over-write the source of
+	 * the data at the front of the range.  i.e. one new_stripe
+	 * along from reshape_progress new_maps to after where
+	 * reshape_safe old_maps to
+	 */
+	writepos = conf->reshape_progress;
+	sector_div(writepos, new_data_disks);
+	readpos = conf->reshape_progress;
+	sector_div(readpos, data_disks);
+	safepos = conf->reshape_safe;
+	sector_div(safepos, data_disks);
+	if (mddev->reshape_backwards) {
+		BUG_ON(writepos < reshape_sectors);
+		writepos -= reshape_sectors;
+		readpos += reshape_sectors;
+		safepos += reshape_sectors;
+	} else {
+		writepos += reshape_sectors;
+		/* readpos and safepos are worst-case calculations.
+		 * A negative number is overly pessimistic, and causes
+		 * obvious problems for unsigned storage.  So clip to 0.
+		 */
+		readpos -= min_t(sector_t, reshape_sectors, readpos);
+		safepos -= min_t(sector_t, reshape_sectors, safepos);
+	}
+
+	/* Having calculated the 'writepos' possibly use it
+	 * to set 'stripe_addr' which is where we will write to.
+	 */
+	if (mddev->reshape_backwards) {
+		BUG_ON(conf->reshape_progress == 0);
+		stripe_addr = writepos;
+		BUG_ON((mddev->dev_sectors &
+			~((sector_t)reshape_sectors - 1))
+		       - reshape_sectors - stripe_addr
+		       != sector_nr);
+	} else {
+		BUG_ON(writepos != sector_nr + reshape_sectors);
+		stripe_addr = sector_nr;
+	}
+
+	/* 'writepos' is the most advanced device address we might write.
+	 * 'readpos' is the least advanced device address we might read.
+	 * 'safepos' is the least address recorded in the metadata as having
+	 *     been reshaped.
+	 * If there is a min_offset_diff, these are adjusted either by
+	 * increasing the safepos/readpos if diff is negative, or
+	 * increasing writepos if diff is positive.
+	 * If 'readpos' is then behind 'writepos', there is no way that we can
+	 * ensure safety in the face of a crash - that must be done by userspace
+	 * making a backup of the data.  So in that case there is no particular
+	 * rush to update metadata.
+	 * Otherwise if 'safepos' is behind 'writepos', then we really need to
+	 * update the metadata to advance 'safepos' to match 'readpos' so that
+	 * we can be safe in the event of a crash.
+	 * So we insist on updating metadata if safepos is behind writepos and
+	 * readpos is beyond writepos.
+	 * In any case, update the metadata every 10 seconds.
+	 * Maybe that number should be configurable, but I'm not sure it is
+	 * worth it.... maybe it could be a multiple of safemode_delay???
+	 */
+	if (conf->min_offset_diff < 0) {
+		safepos += -conf->min_offset_diff;
+		readpos += -conf->min_offset_diff;
+	} else
+		writepos += conf->min_offset_diff;
+
+	if ((mddev->reshape_backwards
+	     ? (safepos > writepos && readpos < writepos)
+	     : (safepos < writepos && readpos > writepos)) ||
+	    time_after(jiffies, conf->reshape_checkpoint + 10*HZ)) {
+		/* Cannot proceed until we've updated the superblock... */
+		wait_event(conf->wait_for_overlap,
+			   atomic_read(&conf->reshape_stripes)==0
+			   || test_bit(MD_RECOVERY_INTR, &mddev->recovery));
+		if (atomic_read(&conf->reshape_stripes) != 0)
+			return 0;
+		mddev->reshape_position = conf->reshape_progress;
+		mddev->curr_resync_completed = sector_nr;
+		if (!mddev->reshape_backwards)
+			/* Can update recovery_offset */
+			rdev_for_each(rdev, mddev)
+				if (rdev->raid_disk >= 0 &&
+				    !test_bit(Journal, &rdev->flags) &&
+				    !test_bit(In_sync, &rdev->flags) &&
+				    rdev->recovery_offset < sector_nr)
+					rdev->recovery_offset = sector_nr;
+
+		conf->reshape_checkpoint = jiffies;
+		set_bit(MD_SB_CHANGE_DEVS, &mddev->sb_flags);
+		md_wakeup_thread(mddev->thread);
+		wait_event(mddev->sb_wait, mddev->sb_flags == 0 ||
+			   test_bit(MD_RECOVERY_INTR, &mddev->recovery));
+		if (test_bit(MD_RECOVERY_INTR, &mddev->recovery))
+			return 0;
+		spin_lock_irq(&conf->device_lock);
+		conf->reshape_safe = mddev->reshape_position;
+		spin_unlock_irq(&conf->device_lock);
+		wake_up(&conf->wait_for_overlap);
+		sysfs_notify_dirent_safe(mddev->sysfs_completed);
+	}
+
+	INIT_LIST_HEAD(&stripes);
+	for (i = 0; i < reshape_sectors; i += RAID5_STRIPE_SECTORS(conf)) {
+		int j;
+		int skipped_disk = 0;
+		sh = raid5_get_active_stripe(conf, NULL, stripe_addr+i,
+					     R5_GAS_NOQUIESCE);
+		set_bit(STRIPE_EXPANDING, &sh->state);
+		atomic_inc(&conf->reshape_stripes);
+		/* If any of this stripe is beyond the end of the old
+		 * array, then we need to zero those blocks
+		 */
+		for (j=sh->disks; j--;) {
+			sector_t s;
+			if (j == sh->pd_idx)
+				continue;
+			if (conf->level == 6 &&
+			    j == sh->qd_idx)
+				continue;
+			s = raid5_compute_blocknr(sh, j, 0);
+			if (s < raid5_size(mddev, 0, 0)) {
+				skipped_disk = 1;
+				continue;
+			}
+			memset(page_address(sh->dev[j].page), 0, RAID5_STRIPE_SIZE(conf));
+			set_bit(R5_Expanded, &sh->dev[j].flags);
+			set_bit(R5_UPTODATE, &sh->dev[j].flags);
+		}
+		if (!skipped_disk) {
+			set_bit(STRIPE_EXPAND_READY, &sh->state);
+			set_bit(STRIPE_HANDLE, &sh->state);
+		}
+		list_add(&sh->lru, &stripes);
+	}
+	spin_lock_irq(&conf->device_lock);
+	if (mddev->reshape_backwards)
+		conf->reshape_progress -= reshape_sectors * new_data_disks;
+	else
+		conf->reshape_progress += reshape_sectors * new_data_disks;
+	spin_unlock_irq(&conf->device_lock);
+	/* Ok, those stripe are ready. We can start scheduling
+	 * reads on the source stripes.
+	 * The source stripes are determined by mapping the first and last
+	 * block on the destination stripes.
+	 */
+	first_sector =
+		raid5_compute_sector(conf, stripe_addr*(new_data_disks),
+				     1, &dd_idx, NULL);
+	last_sector =
+		raid5_compute_sector(conf, ((stripe_addr+reshape_sectors)
+					    * new_data_disks - 1),
+				     1, &dd_idx, NULL);
+	if (last_sector >= mddev->dev_sectors)
+		last_sector = mddev->dev_sectors - 1;
+	while (first_sector <= last_sector) {
+		sh = raid5_get_active_stripe(conf, NULL, first_sector,
+				R5_GAS_PREVIOUS | R5_GAS_NOQUIESCE);
+		set_bit(STRIPE_EXPAND_SOURCE, &sh->state);
+		set_bit(STRIPE_HANDLE, &sh->state);
+		raid5_release_stripe(sh);
+		first_sector += RAID5_STRIPE_SECTORS(conf);
+	}
+	/* Now that the sources are clearly marked, we can release
+	 * the destination stripes
+	 */
+	while (!list_empty(&stripes)) {
+		sh = list_entry(stripes.next, struct stripe_head, lru);
+		list_del_init(&sh->lru);
+		raid5_release_stripe(sh);
+	}
+	/* If this takes us to the resync_max point where we have to pause,
+	 * then we need to write out the superblock.
+	 */
+	sector_nr += reshape_sectors;
+	retn = reshape_sectors;
+finish:
+	if (mddev->curr_resync_completed > mddev->resync_max ||
+	    (sector_nr - mddev->curr_resync_completed) * 2
+	    >= mddev->resync_max - mddev->curr_resync_completed) {
+		/* Cannot proceed until we've updated the superblock... */
+		wait_event(conf->wait_for_overlap,
+			   atomic_read(&conf->reshape_stripes) == 0
+			   || test_bit(MD_RECOVERY_INTR, &mddev->recovery));
+		if (atomic_read(&conf->reshape_stripes) != 0)
+			goto ret;
+		mddev->reshape_position = conf->reshape_progress;
+		mddev->curr_resync_completed = sector_nr;
+		if (!mddev->reshape_backwards)
+			/* Can update recovery_offset */
+			rdev_for_each(rdev, mddev)
+				if (rdev->raid_disk >= 0 &&
+				    !test_bit(Journal, &rdev->flags) &&
+				    !test_bit(In_sync, &rdev->flags) &&
+				    rdev->recovery_offset < sector_nr)
+					rdev->recovery_offset = sector_nr;
+		conf->reshape_checkpoint = jiffies;
+		set_bit(MD_SB_CHANGE_DEVS, &mddev->sb_flags);
+		md_wakeup_thread(mddev->thread);
+		wait_event(mddev->sb_wait,
+			   !test_bit(MD_SB_CHANGE_DEVS, &mddev->sb_flags)
+			   || test_bit(MD_RECOVERY_INTR, &mddev->recovery));
+		if (test_bit(MD_RECOVERY_INTR, &mddev->recovery))
+			goto ret;
+		spin_lock_irq(&conf->device_lock);
+		conf->reshape_safe = mddev->reshape_position;
+		spin_unlock_irq(&conf->device_lock);
+		wake_up(&conf->wait_for_overlap);
+		sysfs_notify_dirent_safe(mddev->sysfs_completed);
+	}
+ret:
+	return retn;
+}
+
+static inline sector_t raid5_sync_request(struct mddev *mddev, sector_t sector_nr,
+					  int *skipped)
+{
+	struct r5conf *conf = mddev->private;
+	struct stripe_head *sh;
+	sector_t max_sector = mddev->dev_sectors;
+	sector_t sync_blocks;
+	int still_degraded = 0;
+	int i;
+
+	if (sector_nr >= max_sector) {
+		/* just being told to finish up .. nothing much to do */
+
+		if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery)) {
+			end_reshape(conf);
+			return 0;
+		}
+
+		if (mddev->curr_resync < max_sector) /* aborted */
+			md_bitmap_end_sync(mddev->bitmap, mddev->curr_resync,
+					   &sync_blocks, 1);
+		else /* completed sync */
+			conf->fullsync = 0;
+		md_bitmap_close_sync(mddev->bitmap);
+
+		return 0;
+	}
+
+	/* Allow raid5_quiesce to complete */
+	wait_event(conf->wait_for_overlap, conf->quiesce != 2);
+
+	if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery))
+		return reshape_request(mddev, sector_nr, skipped);
+
+	/* No need to check resync_max as we never do more than one
+	 * stripe, and as resync_max will always be on a chunk boundary,
+	 * if the check in md_do_sync didn't fire, there is no chance
+	 * of overstepping resync_max here
+	 */
+
+	/* if there is too many failed drives and we are trying
+	 * to resync, then assert that we are finished, because there is
+	 * nothing we can do.
+	 */
+	if (mddev->degraded >= conf->max_degraded &&
+	    test_bit(MD_RECOVERY_SYNC, &mddev->recovery)) {
+		sector_t rv = mddev->dev_sectors - sector_nr;
+		*skipped = 1;
+		return rv;
+	}
+	if (!test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery) &&
+	    !conf->fullsync &&
+	    !md_bitmap_start_sync(mddev->bitmap, sector_nr, &sync_blocks, 1) &&
+	    sync_blocks >= RAID5_STRIPE_SECTORS(conf)) {
+		/* we can skip this block, and probably more */
+		do_div(sync_blocks, RAID5_STRIPE_SECTORS(conf));
+		*skipped = 1;
+		/* keep things rounded to whole stripes */
+		return sync_blocks * RAID5_STRIPE_SECTORS(conf);
+	}
+
+	md_bitmap_cond_end_sync(mddev->bitmap, sector_nr, false);
+
+	sh = raid5_get_active_stripe(conf, NULL, sector_nr,
+				     R5_GAS_NOBLOCK);
+	if (sh == NULL) {
+		sh = raid5_get_active_stripe(conf, NULL, sector_nr, 0);
+		/* make sure we don't swamp the stripe cache if someone else
+		 * is trying to get access
+		 */
+		schedule_timeout_uninterruptible(1);
+	}
+	/* Need to check if array will still be degraded after recovery/resync
+	 * Note in case of > 1 drive failures it's possible we're rebuilding
+	 * one drive while leaving another faulty drive in array.
+	 */
+	rcu_read_lock();
+	for (i = 0; i < conf->raid_disks; i++) {
+		struct md_rdev *rdev = rcu_dereference(conf->disks[i].rdev);
+
+		if (rdev == NULL || test_bit(Faulty, &rdev->flags))
+			still_degraded = 1;
+	}
+	rcu_read_unlock();
+
+	md_bitmap_start_sync(mddev->bitmap, sector_nr, &sync_blocks, still_degraded);
+
+	set_bit(STRIPE_SYNC_REQUESTED, &sh->state);
+	set_bit(STRIPE_HANDLE, &sh->state);
+
+	raid5_release_stripe(sh);
+
+	return RAID5_STRIPE_SECTORS(conf);
+}
+
+static int  retry_aligned_read(struct r5conf *conf, struct bio *raid_bio,
+			       unsigned int offset)
+{
+	/* We may not be able to submit a whole bio at once as there
+	 * may not be enough stripe_heads available.
+	 * We cannot pre-allocate enough stripe_heads as we may need
+	 * more than exist in the cache (if we allow ever large chunks).
+	 * So we do one stripe head at a time and record in
+	 * ->bi_hw_segments how many have been done.
+	 *
+	 * We *know* that this entire raid_bio is in one chunk, so
+	 * it will be only one 'dd_idx' and only need one call to raid5_compute_sector.
+	 */
+	struct stripe_head *sh;
+	int dd_idx;
+	sector_t sector, logical_sector, last_sector;
+	int scnt = 0;
+	int handled = 0;
+
+	logical_sector = raid_bio->bi_iter.bi_sector &
+		~((sector_t)RAID5_STRIPE_SECTORS(conf)-1);
+	sector = raid5_compute_sector(conf, logical_sector,
+				      0, &dd_idx, NULL);
+	last_sector = bio_end_sector(raid_bio);
+
+	for (; logical_sector < last_sector;
+	     logical_sector += RAID5_STRIPE_SECTORS(conf),
+		     sector += RAID5_STRIPE_SECTORS(conf),
+		     scnt++) {
+
+		if (scnt < offset)
+			/* already done this stripe */
+			continue;
+
+		sh = raid5_get_active_stripe(conf, NULL, sector,
+				R5_GAS_NOBLOCK | R5_GAS_NOQUIESCE);
+		if (!sh) {
+			/* failed to get a stripe - must wait */
+			conf->retry_read_aligned = raid_bio;
+			conf->retry_read_offset = scnt;
+			return handled;
+		}
+
+		if (!add_stripe_bio(sh, raid_bio, dd_idx, 0, 0)) {
+			raid5_release_stripe(sh);
+			conf->retry_read_aligned = raid_bio;
+			conf->retry_read_offset = scnt;
+			return handled;
+		}
+
+		set_bit(R5_ReadNoMerge, &sh->dev[dd_idx].flags);
+		handle_stripe(sh);
+		raid5_release_stripe(sh);
+		handled++;
+	}
+
+	bio_endio(raid_bio);
+
+	if (atomic_dec_and_test(&conf->active_aligned_reads))
+		wake_up(&conf->wait_for_quiescent);
+	return handled;
+}
+
+static int handle_active_stripes(struct r5conf *conf, int group,
+				 struct r5worker *worker,
+				 struct list_head *temp_inactive_list)
+		__must_hold(&conf->device_lock)
+{
+	struct stripe_head *batch[MAX_STRIPE_BATCH], *sh;
+	int i, batch_size = 0, hash;
+	bool release_inactive = false;
+
+	while (batch_size < MAX_STRIPE_BATCH &&
+			(sh = __get_priority_stripe(conf, group)) != NULL)
+		batch[batch_size++] = sh;
+
+	if (batch_size == 0) {
+		for (i = 0; i < NR_STRIPE_HASH_LOCKS; i++)
+			if (!list_empty(temp_inactive_list + i))
+				break;
+		if (i == NR_STRIPE_HASH_LOCKS) {
+			spin_unlock_irq(&conf->device_lock);
+			log_flush_stripe_to_raid(conf);
+			spin_lock_irq(&conf->device_lock);
+			return batch_size;
+		}
+		release_inactive = true;
+	}
+	spin_unlock_irq(&conf->device_lock);
+
+	release_inactive_stripe_list(conf, temp_inactive_list,
+				     NR_STRIPE_HASH_LOCKS);
+
+	r5l_flush_stripe_to_raid(conf->log);
+	if (release_inactive) {
+		spin_lock_irq(&conf->device_lock);
+		return 0;
+	}
+
+	for (i = 0; i < batch_size; i++)
+		handle_stripe(batch[i]);
+	log_write_stripe_run(conf);
+
+	cond_resched();
+
+	spin_lock_irq(&conf->device_lock);
+	for (i = 0; i < batch_size; i++) {
+		hash = batch[i]->hash_lock_index;
+		__release_stripe(conf, batch[i], &temp_inactive_list[hash]);
+	}
+	return batch_size;
+}
+
+static void raid5_do_work(struct work_struct *work)
+{
+	struct r5worker *worker = container_of(work, struct r5worker, work);
+	struct r5worker_group *group = worker->group;
+	struct r5conf *conf = group->conf;
+	struct mddev *mddev = conf->mddev;
+	int group_id = group - conf->worker_groups;
+	int handled;
+	struct blk_plug plug;
+
+	pr_debug("+++ raid5worker active\n");
+
+	blk_start_plug(&plug);
+	handled = 0;
+	spin_lock_irq(&conf->device_lock);
+	while (1) {
+		int batch_size, released;
+
+		released = release_stripe_list(conf, worker->temp_inactive_list);
+
+		batch_size = handle_active_stripes(conf, group_id, worker,
+						   worker->temp_inactive_list);
+		worker->working = false;
+		if (!batch_size && !released)
+			break;
+		handled += batch_size;
+		wait_event_lock_irq(mddev->sb_wait,
+			!test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags),
+			conf->device_lock);
+	}
+	pr_debug("%d stripes handled\n", handled);
+
+	spin_unlock_irq(&conf->device_lock);
+
+	flush_deferred_bios(conf);
+
+	r5l_flush_stripe_to_raid(conf->log);
+
+	async_tx_issue_pending_all();
+	blk_finish_plug(&plug);
+
+	pr_debug("--- raid5worker inactive\n");
+}
+
+/*
+ * This is our raid5 kernel thread.
+ *
+ * We scan the hash table for stripes which can be handled now.
+ * During the scan, completed stripes are saved for us by the interrupt
+ * handler, so that they will not have to wait for our next wakeup.
+ */
+static void raid5d(struct md_thread *thread)
+{
+	struct mddev *mddev = thread->mddev;
+	struct r5conf *conf = mddev->private;
+	int handled;
+	struct blk_plug plug;
+
+	pr_debug("+++ raid5d active\n");
+
+	md_check_recovery(mddev);
+
+	blk_start_plug(&plug);
+	handled = 0;
+	spin_lock_irq(&conf->device_lock);
+	while (1) {
+		struct bio *bio;
+		int batch_size, released;
+		unsigned int offset;
+
+		released = release_stripe_list(conf, conf->temp_inactive_list);
+		if (released)
+			clear_bit(R5_DID_ALLOC, &conf->cache_state);
+
+		if (
+		    !list_empty(&conf->bitmap_list)) {
+			/* Now is a good time to flush some bitmap updates */
+			conf->seq_flush++;
+			spin_unlock_irq(&conf->device_lock);
+			md_bitmap_unplug(mddev->bitmap);
+			spin_lock_irq(&conf->device_lock);
+			conf->seq_write = conf->seq_flush;
+			activate_bit_delay(conf, conf->temp_inactive_list);
+		}
+		raid5_activate_delayed(conf);
+
+		while ((bio = remove_bio_from_retry(conf, &offset))) {
+			int ok;
+			spin_unlock_irq(&conf->device_lock);
+			ok = retry_aligned_read(conf, bio, offset);
+			spin_lock_irq(&conf->device_lock);
+			if (!ok)
+				break;
+			handled++;
+		}
+
+		batch_size = handle_active_stripes(conf, ANY_GROUP, NULL,
+						   conf->temp_inactive_list);
+		if (!batch_size && !released)
+			break;
+		handled += batch_size;
+
+		if (mddev->sb_flags & ~(1 << MD_SB_CHANGE_PENDING)) {
+			spin_unlock_irq(&conf->device_lock);
+			md_check_recovery(mddev);
+			spin_lock_irq(&conf->device_lock);
+
+			/*
+			 * Waiting on MD_SB_CHANGE_PENDING below may deadlock
+			 * seeing md_check_recovery() is needed to clear
+			 * the flag when using mdmon.
+			 */
+			continue;
+		}
+
+		wait_event_lock_irq(mddev->sb_wait,
+			!test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags),
+			conf->device_lock);
+	}
+	pr_debug("%d stripes handled\n", handled);
+
+	spin_unlock_irq(&conf->device_lock);
+	if (test_and_clear_bit(R5_ALLOC_MORE, &conf->cache_state) &&
+	    mutex_trylock(&conf->cache_size_mutex)) {
+		grow_one_stripe(conf, __GFP_NOWARN);
+		/* Set flag even if allocation failed.  This helps
+		 * slow down allocation requests when mem is short
+		 */
+		set_bit(R5_DID_ALLOC, &conf->cache_state);
+		mutex_unlock(&conf->cache_size_mutex);
+	}
+
+	flush_deferred_bios(conf);
+
+	r5l_flush_stripe_to_raid(conf->log);
+
+	async_tx_issue_pending_all();
+	blk_finish_plug(&plug);
+
+	pr_debug("--- raid5d inactive\n");
+}
+
+static ssize_t
+raid5_show_stripe_cache_size(struct mddev *mddev, char *page)
+{
+	struct r5conf *conf;
+	int ret = 0;
+	spin_lock(&mddev->lock);
+	conf = mddev->private;
+	if (conf)
+		ret = sprintf(page, "%d\n", conf->min_nr_stripes);
+	spin_unlock(&mddev->lock);
+	return ret;
+}
+
+int
+raid5_set_cache_size(struct mddev *mddev, int size)
+{
+	int result = 0;
+	struct r5conf *conf = mddev->private;
+
+	if (size <= 16 || size > 32768)
+		return -EINVAL;
+
+	conf->min_nr_stripes = size;
+	mutex_lock(&conf->cache_size_mutex);
+	while (size < conf->max_nr_stripes &&
+	       drop_one_stripe(conf))
+		;
+	mutex_unlock(&conf->cache_size_mutex);
+
+	md_allow_write(mddev);
+
+	mutex_lock(&conf->cache_size_mutex);
+	while (size > conf->max_nr_stripes)
+		if (!grow_one_stripe(conf, GFP_KERNEL)) {
+			conf->min_nr_stripes = conf->max_nr_stripes;
+			result = -ENOMEM;
+			break;
+		}
+	mutex_unlock(&conf->cache_size_mutex);
+
+	return result;
+}
+EXPORT_SYMBOL(raid5_set_cache_size);
+
+static ssize_t
+raid5_store_stripe_cache_size(struct mddev *mddev, const char *page, size_t len)
+{
+	struct r5conf *conf;
+	unsigned long new;
+	int err;
+
+	if (len >= PAGE_SIZE)
+		return -EINVAL;
+	if (kstrtoul(page, 10, &new))
+		return -EINVAL;
+	err = mddev_lock(mddev);
+	if (err)
+		return err;
+	conf = mddev->private;
+	if (!conf)
+		err = -ENODEV;
+	else
+		err = raid5_set_cache_size(mddev, new);
+	mddev_unlock(mddev);
+
+	return err ?: len;
+}
+
+static struct md_sysfs_entry
+raid5_stripecache_size = __ATTR(stripe_cache_size, S_IRUGO | S_IWUSR,
+				raid5_show_stripe_cache_size,
+				raid5_store_stripe_cache_size);
+
+static ssize_t
+raid5_show_rmw_level(struct mddev  *mddev, char *page)
+{
+	struct r5conf *conf = mddev->private;
+	if (conf)
+		return sprintf(page, "%d\n", conf->rmw_level);
+	else
+		return 0;
+}
+
+static ssize_t
+raid5_store_rmw_level(struct mddev  *mddev, const char *page, size_t len)
+{
+	struct r5conf *conf = mddev->private;
+	unsigned long new;
+
+	if (!conf)
+		return -ENODEV;
+
+	if (len >= PAGE_SIZE)
+		return -EINVAL;
+
+	if (kstrtoul(page, 10, &new))
+		return -EINVAL;
+
+	if (new != PARITY_DISABLE_RMW && !raid6_call.xor_syndrome)
+		return -EINVAL;
+
+	if (new != PARITY_DISABLE_RMW &&
+	    new != PARITY_ENABLE_RMW &&
+	    new != PARITY_PREFER_RMW)
+		return -EINVAL;
+
+	conf->rmw_level = new;
+	return len;
+}
+
+static struct md_sysfs_entry
+raid5_rmw_level = __ATTR(rmw_level, S_IRUGO | S_IWUSR,
+			 raid5_show_rmw_level,
+			 raid5_store_rmw_level);
+
+static ssize_t
+raid5_show_stripe_size(struct mddev  *mddev, char *page)
+{
+	struct r5conf *conf;
+	int ret = 0;
+
+	spin_lock(&mddev->lock);
+	conf = mddev->private;
+	if (conf)
+		ret = sprintf(page, "%lu\n", RAID5_STRIPE_SIZE(conf));
+	spin_unlock(&mddev->lock);
+	return ret;
+}
+
+#if PAGE_SIZE != DEFAULT_STRIPE_SIZE
+static ssize_t
+raid5_store_stripe_size(struct mddev  *mddev, const char *page, size_t len)
+{
+	struct r5conf *conf;
+	unsigned long new;
+	int err;
+	int size;
+
+	if (len >= PAGE_SIZE)
+		return -EINVAL;
+	if (kstrtoul(page, 10, &new))
+		return -EINVAL;
+
+	/*
+	 * The value should not be bigger than PAGE_SIZE. It requires to
+	 * be multiple of DEFAULT_STRIPE_SIZE and the value should be power
+	 * of two.
+	 */
+	if (new % DEFAULT_STRIPE_SIZE != 0 ||
+			new > PAGE_SIZE || new == 0 ||
+			new != roundup_pow_of_two(new))
+		return -EINVAL;
+
+	err = mddev_lock(mddev);
+	if (err)
+		return err;
+
+	conf = mddev->private;
+	if (!conf) {
+		err = -ENODEV;
+		goto out_unlock;
+	}
+
+	if (new == conf->stripe_size)
+		goto out_unlock;
+
+	pr_debug("md/raid: change stripe_size from %lu to %lu\n",
+			conf->stripe_size, new);
+
+	if (mddev->sync_thread ||
+		test_bit(MD_RECOVERY_RUNNING, &mddev->recovery) ||
+		mddev->reshape_position != MaxSector ||
+		mddev->sysfs_active) {
+		err = -EBUSY;
+		goto out_unlock;
+	}
+
+	mddev_suspend(mddev);
+	mutex_lock(&conf->cache_size_mutex);
+	size = conf->max_nr_stripes;
+
+	shrink_stripes(conf);
+
+	conf->stripe_size = new;
+	conf->stripe_shift = ilog2(new) - 9;
+	conf->stripe_sectors = new >> 9;
+	if (grow_stripes(conf, size)) {
+		pr_warn("md/raid:%s: couldn't allocate buffers\n",
+				mdname(mddev));
+		err = -ENOMEM;
+	}
+	mutex_unlock(&conf->cache_size_mutex);
+	mddev_resume(mddev);
+
+out_unlock:
+	mddev_unlock(mddev);
+	return err ?: len;
+}
+
+static struct md_sysfs_entry
+raid5_stripe_size = __ATTR(stripe_size, 0644,
+			 raid5_show_stripe_size,
+			 raid5_store_stripe_size);
+#else
+static struct md_sysfs_entry
+raid5_stripe_size = __ATTR(stripe_size, 0444,
+			 raid5_show_stripe_size,
+			 NULL);
+#endif
+
+static ssize_t
+raid5_show_preread_threshold(struct mddev *mddev, char *page)
+{
+	struct r5conf *conf;
+	int ret = 0;
+	spin_lock(&mddev->lock);
+	conf = mddev->private;
+	if (conf)
+		ret = sprintf(page, "%d\n", conf->bypass_threshold);
+	spin_unlock(&mddev->lock);
+	return ret;
+}
+
+static ssize_t
+raid5_store_preread_threshold(struct mddev *mddev, const char *page, size_t len)
+{
+	struct r5conf *conf;
+	unsigned long new;
+	int err;
+
+	if (len >= PAGE_SIZE)
+		return -EINVAL;
+	if (kstrtoul(page, 10, &new))
+		return -EINVAL;
+
+	err = mddev_lock(mddev);
+	if (err)
+		return err;
+	conf = mddev->private;
+	if (!conf)
+		err = -ENODEV;
+	else if (new > conf->min_nr_stripes)
+		err = -EINVAL;
+	else
+		conf->bypass_threshold = new;
+	mddev_unlock(mddev);
+	return err ?: len;
+}
+
+static struct md_sysfs_entry
+raid5_preread_bypass_threshold = __ATTR(preread_bypass_threshold,
+					S_IRUGO | S_IWUSR,
+					raid5_show_preread_threshold,
+					raid5_store_preread_threshold);
+
+static ssize_t
+raid5_show_skip_copy(struct mddev *mddev, char *page)
+{
+	struct r5conf *conf;
+	int ret = 0;
+	spin_lock(&mddev->lock);
+	conf = mddev->private;
+	if (conf)
+		ret = sprintf(page, "%d\n", conf->skip_copy);
+	spin_unlock(&mddev->lock);
+	return ret;
+}
+
+static ssize_t
+raid5_store_skip_copy(struct mddev *mddev, const char *page, size_t len)
+{
+	struct r5conf *conf;
+	unsigned long new;
+	int err;
+
+	if (len >= PAGE_SIZE)
+		return -EINVAL;
+	if (kstrtoul(page, 10, &new))
+		return -EINVAL;
+	new = !!new;
+
+	err = mddev_lock(mddev);
+	if (err)
+		return err;
+	conf = mddev->private;
+	if (!conf)
+		err = -ENODEV;
+	else if (new != conf->skip_copy) {
+		struct request_queue *q = mddev->queue;
+
+		mddev_suspend(mddev);
+		conf->skip_copy = new;
+		if (new)
+			blk_queue_flag_set(QUEUE_FLAG_STABLE_WRITES, q);
+		else
+			blk_queue_flag_clear(QUEUE_FLAG_STABLE_WRITES, q);
+		mddev_resume(mddev);
+	}
+	mddev_unlock(mddev);
+	return err ?: len;
+}
+
+static struct md_sysfs_entry
+raid5_skip_copy = __ATTR(skip_copy, S_IRUGO | S_IWUSR,
+					raid5_show_skip_copy,
+					raid5_store_skip_copy);
+
+static ssize_t
+stripe_cache_active_show(struct mddev *mddev, char *page)
+{
+	struct r5conf *conf = mddev->private;
+	if (conf)
+		return sprintf(page, "%d\n", atomic_read(&conf->active_stripes));
+	else
+		return 0;
+}
+
+static struct md_sysfs_entry
+raid5_stripecache_active = __ATTR_RO(stripe_cache_active);
+
+static ssize_t
+raid5_show_group_thread_cnt(struct mddev *mddev, char *page)
+{
+	struct r5conf *conf;
+	int ret = 0;
+	spin_lock(&mddev->lock);
+	conf = mddev->private;
+	if (conf)
+		ret = sprintf(page, "%d\n", conf->worker_cnt_per_group);
+	spin_unlock(&mddev->lock);
+	return ret;
+}
+
+static int alloc_thread_groups(struct r5conf *conf, int cnt,
+			       int *group_cnt,
+			       struct r5worker_group **worker_groups);
+static ssize_t
+raid5_store_group_thread_cnt(struct mddev *mddev, const char *page, size_t len)
+{
+	struct r5conf *conf;
+	unsigned int new;
+	int err;
+	struct r5worker_group *new_groups, *old_groups;
+	int group_cnt;
+
+	if (len >= PAGE_SIZE)
+		return -EINVAL;
+	if (kstrtouint(page, 10, &new))
+		return -EINVAL;
+	/* 8192 should be big enough */
+	if (new > 8192)
+		return -EINVAL;
+
+	err = mddev_lock(mddev);
+	if (err)
+		return err;
+	conf = mddev->private;
+	if (!conf)
+		err = -ENODEV;
+	else if (new != conf->worker_cnt_per_group) {
+		mddev_suspend(mddev);
+
+		old_groups = conf->worker_groups;
+		if (old_groups)
+			flush_workqueue(raid5_wq);
+
+		err = alloc_thread_groups(conf, new, &group_cnt, &new_groups);
+		if (!err) {
+			spin_lock_irq(&conf->device_lock);
+			conf->group_cnt = group_cnt;
+			conf->worker_cnt_per_group = new;
+			conf->worker_groups = new_groups;
+			spin_unlock_irq(&conf->device_lock);
+
+			if (old_groups)
+				kfree(old_groups[0].workers);
+			kfree(old_groups);
+		}
+		mddev_resume(mddev);
+	}
+	mddev_unlock(mddev);
+
+	return err ?: len;
+}
+
+static struct md_sysfs_entry
+raid5_group_thread_cnt = __ATTR(group_thread_cnt, S_IRUGO | S_IWUSR,
+				raid5_show_group_thread_cnt,
+				raid5_store_group_thread_cnt);
+
+static struct attribute *raid5_attrs[] =  {
+	&raid5_stripecache_size.attr,
+	&raid5_stripecache_active.attr,
+	&raid5_preread_bypass_threshold.attr,
+	&raid5_group_thread_cnt.attr,
+	&raid5_skip_copy.attr,
+	&raid5_rmw_level.attr,
+	&raid5_stripe_size.attr,
+	&r5c_journal_mode.attr,
+	&ppl_write_hint.attr,
+	NULL,
+};
+static const struct attribute_group raid5_attrs_group = {
+	.name = NULL,
+	.attrs = raid5_attrs,
+};
+
+static int alloc_thread_groups(struct r5conf *conf, int cnt, int *group_cnt,
+			       struct r5worker_group **worker_groups)
+{
+	int i, j, k;
+	ssize_t size;
+	struct r5worker *workers;
+
+	if (cnt == 0) {
+		*group_cnt = 0;
+		*worker_groups = NULL;
+		return 0;
+	}
+	*group_cnt = num_possible_nodes();
+	size = sizeof(struct r5worker) * cnt;
+	workers = kcalloc(size, *group_cnt, GFP_NOIO);
+	*worker_groups = kcalloc(*group_cnt, sizeof(struct r5worker_group),
+				 GFP_NOIO);
+	if (!*worker_groups || !workers) {
+		kfree(workers);
+		kfree(*worker_groups);
+		return -ENOMEM;
+	}
+
+	for (i = 0; i < *group_cnt; i++) {
+		struct r5worker_group *group;
+
+		group = &(*worker_groups)[i];
+		INIT_LIST_HEAD(&group->handle_list);
+		INIT_LIST_HEAD(&group->loprio_list);
+		group->conf = conf;
+		group->workers = workers + i * cnt;
+
+		for (j = 0; j < cnt; j++) {
+			struct r5worker *worker = group->workers + j;
+			worker->group = group;
+			INIT_WORK(&worker->work, raid5_do_work);
+
+			for (k = 0; k < NR_STRIPE_HASH_LOCKS; k++)
+				INIT_LIST_HEAD(worker->temp_inactive_list + k);
+		}
+	}
+
+	return 0;
+}
+
+static void free_thread_groups(struct r5conf *conf)
+{
+	if (conf->worker_groups)
+		kfree(conf->worker_groups[0].workers);
+	kfree(conf->worker_groups);
+	conf->worker_groups = NULL;
+}
+
+static sector_t
+raid5_size(struct mddev *mddev, sector_t sectors, int raid_disks)
+{
+	struct r5conf *conf = mddev->private;
+
+	if (!sectors)
+		sectors = mddev->dev_sectors;
+	if (!raid_disks)
+		/* size is defined by the smallest of previous and new size */
+		raid_disks = min(conf->raid_disks, conf->previous_raid_disks);
+
+	sectors &= ~((sector_t)conf->chunk_sectors - 1);
+	sectors &= ~((sector_t)conf->prev_chunk_sectors - 1);
+	return sectors * (raid_disks - conf->max_degraded);
+}
+
+static void free_scratch_buffer(struct r5conf *conf, struct raid5_percpu *percpu)
+{
+	safe_put_page(percpu->spare_page);
+	percpu->spare_page = NULL;
+	kvfree(percpu->scribble);
+	percpu->scribble = NULL;
+}
+
+static int alloc_scratch_buffer(struct r5conf *conf, struct raid5_percpu *percpu)
+{
+	if (conf->level == 6 && !percpu->spare_page) {
+		percpu->spare_page = alloc_page(GFP_KERNEL);
+		if (!percpu->spare_page)
+			return -ENOMEM;
+	}
+
+	if (scribble_alloc(percpu,
+			   max(conf->raid_disks,
+			       conf->previous_raid_disks),
+			   max(conf->chunk_sectors,
+			       conf->prev_chunk_sectors)
+			   / RAID5_STRIPE_SECTORS(conf))) {
+		free_scratch_buffer(conf, percpu);
+		return -ENOMEM;
+	}
+
+	local_lock_init(&percpu->lock);
+	return 0;
+}
+
+static int raid456_cpu_dead(unsigned int cpu, struct hlist_node *node)
+{
+	struct r5conf *conf = hlist_entry_safe(node, struct r5conf, node);
+
+	free_scratch_buffer(conf, per_cpu_ptr(conf->percpu, cpu));
+	return 0;
+}
+
+static void raid5_free_percpu(struct r5conf *conf)
+{
+	if (!conf->percpu)
+		return;
+
+	cpuhp_state_remove_instance(CPUHP_MD_RAID5_PREPARE, &conf->node);
+	free_percpu(conf->percpu);
+}
+
+static void free_conf(struct r5conf *conf)
+{
+	int i;
+
+	log_exit(conf);
+
+	unregister_shrinker(&conf->shrinker);
+	free_thread_groups(conf);
+	shrink_stripes(conf);
+	raid5_free_percpu(conf);
+	for (i = 0; i < conf->pool_size; i++)
+		if (conf->disks[i].extra_page)
+			put_page(conf->disks[i].extra_page);
+	kfree(conf->disks);
+	bioset_exit(&conf->bio_split);
+	kfree(conf->stripe_hashtbl);
+	kfree(conf->pending_data);
+	kfree(conf);
+}
+
+static int raid456_cpu_up_prepare(unsigned int cpu, struct hlist_node *node)
+{
+	struct r5conf *conf = hlist_entry_safe(node, struct r5conf, node);
+	struct raid5_percpu *percpu = per_cpu_ptr(conf->percpu, cpu);
+
+	if (alloc_scratch_buffer(conf, percpu)) {
+		pr_warn("%s: failed memory allocation for cpu%u\n",
+			__func__, cpu);
+		return -ENOMEM;
+	}
+	return 0;
+}
+
+static int raid5_alloc_percpu(struct r5conf *conf)
+{
+	int err = 0;
+
+	conf->percpu = alloc_percpu(struct raid5_percpu);
+	if (!conf->percpu)
+		return -ENOMEM;
+
+	err = cpuhp_state_add_instance(CPUHP_MD_RAID5_PREPARE, &conf->node);
+	if (!err) {
+		conf->scribble_disks = max(conf->raid_disks,
+			conf->previous_raid_disks);
+		conf->scribble_sectors = max(conf->chunk_sectors,
+			conf->prev_chunk_sectors);
+	}
+	return err;
+}
+
+static unsigned long raid5_cache_scan(struct shrinker *shrink,
+				      struct shrink_control *sc)
+{
+	struct r5conf *conf = container_of(shrink, struct r5conf, shrinker);
+	unsigned long ret = SHRINK_STOP;
+
+	if (mutex_trylock(&conf->cache_size_mutex)) {
+		ret= 0;
+		while (ret < sc->nr_to_scan &&
+		       conf->max_nr_stripes > conf->min_nr_stripes) {
+			if (drop_one_stripe(conf) == 0) {
+				ret = SHRINK_STOP;
+				break;
+			}
+			ret++;
+		}
+		mutex_unlock(&conf->cache_size_mutex);
+	}
+	return ret;
+}
+
+static unsigned long raid5_cache_count(struct shrinker *shrink,
+				       struct shrink_control *sc)
+{
+	struct r5conf *conf = container_of(shrink, struct r5conf, shrinker);
+
+	if (conf->max_nr_stripes < conf->min_nr_stripes)
+		/* unlikely, but not impossible */
+		return 0;
+	return conf->max_nr_stripes - conf->min_nr_stripes;
+}
+
+static struct r5conf *setup_conf(struct mddev *mddev)
+{
+	struct r5conf *conf;
+	int raid_disk, memory, max_disks;
+	struct md_rdev *rdev;
+	struct disk_info *disk;
+	char pers_name[6];
+	int i;
+	int group_cnt;
+	struct r5worker_group *new_group;
+	int ret = -ENOMEM;
+
+	if (mddev->new_level != 5
+	    && mddev->new_level != 4
+	    && mddev->new_level != 6) {
+		pr_warn("md/raid:%s: raid level not set to 4/5/6 (%d)\n",
+			mdname(mddev), mddev->new_level);
+		return ERR_PTR(-EIO);
+	}
+	if ((mddev->new_level == 5
+	     && !algorithm_valid_raid5(mddev->new_layout)) ||
+	    (mddev->new_level == 6
+	     && !algorithm_valid_raid6(mddev->new_layout))) {
+		pr_warn("md/raid:%s: layout %d not supported\n",
+			mdname(mddev), mddev->new_layout);
+		return ERR_PTR(-EIO);
+	}
+	if (mddev->new_level == 6 && mddev->raid_disks < 4) {
+		pr_warn("md/raid:%s: not enough configured devices (%d, minimum 4)\n",
+			mdname(mddev), mddev->raid_disks);
+		return ERR_PTR(-EINVAL);
+	}
+
+	if (!mddev->new_chunk_sectors ||
+	    (mddev->new_chunk_sectors << 9) % PAGE_SIZE ||
+	    !is_power_of_2(mddev->new_chunk_sectors)) {
+		pr_warn("md/raid:%s: invalid chunk size %d\n",
+			mdname(mddev), mddev->new_chunk_sectors << 9);
+		return ERR_PTR(-EINVAL);
+	}
+
+	conf = kzalloc(sizeof(struct r5conf), GFP_KERNEL);
+	if (conf == NULL)
+		goto abort;
+
+#if PAGE_SIZE != DEFAULT_STRIPE_SIZE
+	conf->stripe_size = DEFAULT_STRIPE_SIZE;
+	conf->stripe_shift = ilog2(DEFAULT_STRIPE_SIZE) - 9;
+	conf->stripe_sectors = DEFAULT_STRIPE_SIZE >> 9;
+#endif
+	INIT_LIST_HEAD(&conf->free_list);
+	INIT_LIST_HEAD(&conf->pending_list);
+	conf->pending_data = kcalloc(PENDING_IO_MAX,
+				     sizeof(struct r5pending_data),
+				     GFP_KERNEL);
+	if (!conf->pending_data)
+		goto abort;
+	for (i = 0; i < PENDING_IO_MAX; i++)
+		list_add(&conf->pending_data[i].sibling, &conf->free_list);
+	/* Don't enable multi-threading by default*/
+	if (!alloc_thread_groups(conf, 0, &group_cnt, &new_group)) {
+		conf->group_cnt = group_cnt;
+		conf->worker_cnt_per_group = 0;
+		conf->worker_groups = new_group;
+	} else
+		goto abort;
+	spin_lock_init(&conf->device_lock);
+	seqcount_spinlock_init(&conf->gen_lock, &conf->device_lock);
+	mutex_init(&conf->cache_size_mutex);
+
+	init_waitqueue_head(&conf->wait_for_quiescent);
+	init_waitqueue_head(&conf->wait_for_stripe);
+	init_waitqueue_head(&conf->wait_for_overlap);
+	INIT_LIST_HEAD(&conf->handle_list);
+	INIT_LIST_HEAD(&conf->loprio_list);
+	INIT_LIST_HEAD(&conf->hold_list);
+	INIT_LIST_HEAD(&conf->delayed_list);
+	INIT_LIST_HEAD(&conf->bitmap_list);
+	init_llist_head(&conf->released_stripes);
+	atomic_set(&conf->active_stripes, 0);
+	atomic_set(&conf->preread_active_stripes, 0);
+	atomic_set(&conf->active_aligned_reads, 0);
+	spin_lock_init(&conf->pending_bios_lock);
+	conf->batch_bio_dispatch = true;
+	rdev_for_each(rdev, mddev) {
+		if (test_bit(Journal, &rdev->flags))
+			continue;
+		if (bdev_nonrot(rdev->bdev)) {
+			conf->batch_bio_dispatch = false;
+			break;
+		}
+	}
+
+	conf->bypass_threshold = BYPASS_THRESHOLD;
+	conf->recovery_disabled = mddev->recovery_disabled - 1;
+
+	conf->raid_disks = mddev->raid_disks;
+	if (mddev->reshape_position == MaxSector)
+		conf->previous_raid_disks = mddev->raid_disks;
+	else
+		conf->previous_raid_disks = mddev->raid_disks - mddev->delta_disks;
+	max_disks = max(conf->raid_disks, conf->previous_raid_disks);
+
+	conf->disks = kcalloc(max_disks, sizeof(struct disk_info),
+			      GFP_KERNEL);
+
+	if (!conf->disks)
+		goto abort;
+
+	for (i = 0; i < max_disks; i++) {
+		conf->disks[i].extra_page = alloc_page(GFP_KERNEL);
+		if (!conf->disks[i].extra_page)
+			goto abort;
+	}
+
+	ret = bioset_init(&conf->bio_split, BIO_POOL_SIZE, 0, 0);
+	if (ret)
+		goto abort;
+	conf->mddev = mddev;
+
+	ret = -ENOMEM;
+	conf->stripe_hashtbl = kzalloc(PAGE_SIZE, GFP_KERNEL);
+	if (!conf->stripe_hashtbl)
+		goto abort;
+
+	/* We init hash_locks[0] separately to that it can be used
+	 * as the reference lock in the spin_lock_nest_lock() call
+	 * in lock_all_device_hash_locks_irq in order to convince
+	 * lockdep that we know what we are doing.
+	 */
+	spin_lock_init(conf->hash_locks);
+	for (i = 1; i < NR_STRIPE_HASH_LOCKS; i++)
+		spin_lock_init(conf->hash_locks + i);
+
+	for (i = 0; i < NR_STRIPE_HASH_LOCKS; i++)
+		INIT_LIST_HEAD(conf->inactive_list + i);
+
+	for (i = 0; i < NR_STRIPE_HASH_LOCKS; i++)
+		INIT_LIST_HEAD(conf->temp_inactive_list + i);
+
+	atomic_set(&conf->r5c_cached_full_stripes, 0);
+	INIT_LIST_HEAD(&conf->r5c_full_stripe_list);
+	atomic_set(&conf->r5c_cached_partial_stripes, 0);
+	INIT_LIST_HEAD(&conf->r5c_partial_stripe_list);
+	atomic_set(&conf->r5c_flushing_full_stripes, 0);
+	atomic_set(&conf->r5c_flushing_partial_stripes, 0);
+
+	conf->level = mddev->new_level;
+	conf->chunk_sectors = mddev->new_chunk_sectors;
+	ret = raid5_alloc_percpu(conf);
+	if (ret)
+		goto abort;
+
+	pr_debug("raid456: run(%s) called.\n", mdname(mddev));
+
+	ret = -EIO;
+	rdev_for_each(rdev, mddev) {
+		raid_disk = rdev->raid_disk;
+		if (raid_disk >= max_disks
+		    || raid_disk < 0 || test_bit(Journal, &rdev->flags))
+			continue;
+		disk = conf->disks + raid_disk;
+
+		if (test_bit(Replacement, &rdev->flags)) {
+			if (disk->replacement)
+				goto abort;
+			RCU_INIT_POINTER(disk->replacement, rdev);
+		} else {
+			if (disk->rdev)
+				goto abort;
+			RCU_INIT_POINTER(disk->rdev, rdev);
+		}
+
+		if (test_bit(In_sync, &rdev->flags)) {
+			pr_info("md/raid:%s: device %pg operational as raid disk %d\n",
+				mdname(mddev), rdev->bdev, raid_disk);
+		} else if (rdev->saved_raid_disk != raid_disk)
+			/* Cannot rely on bitmap to complete recovery */
+			conf->fullsync = 1;
+	}
+
+	conf->level = mddev->new_level;
+	if (conf->level == 6) {
+		conf->max_degraded = 2;
+		if (raid6_call.xor_syndrome)
+			conf->rmw_level = PARITY_ENABLE_RMW;
+		else
+			conf->rmw_level = PARITY_DISABLE_RMW;
+	} else {
+		conf->max_degraded = 1;
+		conf->rmw_level = PARITY_ENABLE_RMW;
+	}
+	conf->algorithm = mddev->new_layout;
+	conf->reshape_progress = mddev->reshape_position;
+	if (conf->reshape_progress != MaxSector) {
+		conf->prev_chunk_sectors = mddev->chunk_sectors;
+		conf->prev_algo = mddev->layout;
+	} else {
+		conf->prev_chunk_sectors = conf->chunk_sectors;
+		conf->prev_algo = conf->algorithm;
+	}
+
+	conf->min_nr_stripes = NR_STRIPES;
+	if (mddev->reshape_position != MaxSector) {
+		int stripes = max_t(int,
+			((mddev->chunk_sectors << 9) / RAID5_STRIPE_SIZE(conf)) * 4,
+			((mddev->new_chunk_sectors << 9) / RAID5_STRIPE_SIZE(conf)) * 4);
+		conf->min_nr_stripes = max(NR_STRIPES, stripes);
+		if (conf->min_nr_stripes != NR_STRIPES)
+			pr_info("md/raid:%s: force stripe size %d for reshape\n",
+				mdname(mddev), conf->min_nr_stripes);
+	}
+	memory = conf->min_nr_stripes * (sizeof(struct stripe_head) +
+		 max_disks * ((sizeof(struct bio) + PAGE_SIZE))) / 1024;
+	atomic_set(&conf->empty_inactive_list_nr, NR_STRIPE_HASH_LOCKS);
+	if (grow_stripes(conf, conf->min_nr_stripes)) {
+		pr_warn("md/raid:%s: couldn't allocate %dkB for buffers\n",
+			mdname(mddev), memory);
+		ret = -ENOMEM;
+		goto abort;
+	} else
+		pr_debug("md/raid:%s: allocated %dkB\n", mdname(mddev), memory);
+	/*
+	 * Losing a stripe head costs more than the time to refill it,
+	 * it reduces the queue depth and so can hurt throughput.
+	 * So set it rather large, scaled by number of devices.
+	 */
+	conf->shrinker.seeks = DEFAULT_SEEKS * conf->raid_disks * 4;
+	conf->shrinker.scan_objects = raid5_cache_scan;
+	conf->shrinker.count_objects = raid5_cache_count;
+	conf->shrinker.batch = 128;
+	conf->shrinker.flags = 0;
+	ret = register_shrinker(&conf->shrinker, "md-raid5:%s", mdname(mddev));
+	if (ret) {
+		pr_warn("md/raid:%s: couldn't register shrinker.\n",
+			mdname(mddev));
+		goto abort;
+	}
+
+	sprintf(pers_name, "raid%d", mddev->new_level);
+	rcu_assign_pointer(conf->thread,
+			   md_register_thread(raid5d, mddev, pers_name));
+	if (!conf->thread) {
+		pr_warn("md/raid:%s: couldn't allocate thread.\n",
+			mdname(mddev));
+		ret = -ENOMEM;
+		goto abort;
+	}
+
+	return conf;
+
+ abort:
+	if (conf)
+		free_conf(conf);
+	return ERR_PTR(ret);
+}
+
+static int only_parity(int raid_disk, int algo, int raid_disks, int max_degraded)
+{
+	switch (algo) {
+	case ALGORITHM_PARITY_0:
+		if (raid_disk < max_degraded)
+			return 1;
+		break;
+	case ALGORITHM_PARITY_N:
+		if (raid_disk >= raid_disks - max_degraded)
+			return 1;
+		break;
+	case ALGORITHM_PARITY_0_6:
+		if (raid_disk == 0 ||
+		    raid_disk == raid_disks - 1)
+			return 1;
+		break;
+	case ALGORITHM_LEFT_ASYMMETRIC_6:
+	case ALGORITHM_RIGHT_ASYMMETRIC_6:
+	case ALGORITHM_LEFT_SYMMETRIC_6:
+	case ALGORITHM_RIGHT_SYMMETRIC_6:
+		if (raid_disk == raid_disks - 1)
+			return 1;
+	}
+	return 0;
+}
+
+static void raid5_set_io_opt(struct r5conf *conf)
+{
+	blk_queue_io_opt(conf->mddev->queue, (conf->chunk_sectors << 9) *
+			 (conf->raid_disks - conf->max_degraded));
+}
+
+static int raid5_run(struct mddev *mddev)
+{
+	struct r5conf *conf;
+	int dirty_parity_disks = 0;
+	struct md_rdev *rdev;
+	struct md_rdev *journal_dev = NULL;
+	sector_t reshape_offset = 0;
+	int i;
+	long long min_offset_diff = 0;
+	int first = 1;
+
+	if (mddev_init_writes_pending(mddev) < 0)
+		return -ENOMEM;
+
+	if (mddev->recovery_cp != MaxSector)
+		pr_notice("md/raid:%s: not clean -- starting background reconstruction\n",
+			  mdname(mddev));
+
+	rdev_for_each(rdev, mddev) {
+		long long diff;
+
+		if (test_bit(Journal, &rdev->flags)) {
+			journal_dev = rdev;
+			continue;
+		}
+		if (rdev->raid_disk < 0)
+			continue;
+		diff = (rdev->new_data_offset - rdev->data_offset);
+		if (first) {
+			min_offset_diff = diff;
+			first = 0;
+		} else if (mddev->reshape_backwards &&
+			 diff < min_offset_diff)
+			min_offset_diff = diff;
+		else if (!mddev->reshape_backwards &&
+			 diff > min_offset_diff)
+			min_offset_diff = diff;
+	}
+
+	if ((test_bit(MD_HAS_JOURNAL, &mddev->flags) || journal_dev) &&
+	    (mddev->bitmap_info.offset || mddev->bitmap_info.file)) {
+		pr_notice("md/raid:%s: array cannot have both journal and bitmap\n",
+			  mdname(mddev));
+		return -EINVAL;
+	}
+
+	if (mddev->reshape_position != MaxSector) {
+		/* Check that we can continue the reshape.
+		 * Difficulties arise if the stripe we would write to
+		 * next is at or after the stripe we would read from next.
+		 * For a reshape that changes the number of devices, this
+		 * is only possible for a very short time, and mdadm makes
+		 * sure that time appears to have past before assembling
+		 * the array.  So we fail if that time hasn't passed.
+		 * For a reshape that keeps the number of devices the same
+		 * mdadm must be monitoring the reshape can keeping the
+		 * critical areas read-only and backed up.  It will start
+		 * the array in read-only mode, so we check for that.
+		 */
+		sector_t here_new, here_old;
+		int old_disks;
+		int max_degraded = (mddev->level == 6 ? 2 : 1);
+		int chunk_sectors;
+		int new_data_disks;
+
+		if (journal_dev) {
+			pr_warn("md/raid:%s: don't support reshape with journal - aborting.\n",
+				mdname(mddev));
+			return -EINVAL;
+		}
+
+		if (mddev->new_level != mddev->level) {
+			pr_warn("md/raid:%s: unsupported reshape required - aborting.\n",
+				mdname(mddev));
+			return -EINVAL;
+		}
+		old_disks = mddev->raid_disks - mddev->delta_disks;
+		/* reshape_position must be on a new-stripe boundary, and one
+		 * further up in new geometry must map after here in old
+		 * geometry.
+		 * If the chunk sizes are different, then as we perform reshape
+		 * in units of the largest of the two, reshape_position needs
+		 * be a multiple of the largest chunk size times new data disks.
+		 */
+		here_new = mddev->reshape_position;
+		chunk_sectors = max(mddev->chunk_sectors, mddev->new_chunk_sectors);
+		new_data_disks = mddev->raid_disks - max_degraded;
+		if (sector_div(here_new, chunk_sectors * new_data_disks)) {
+			pr_warn("md/raid:%s: reshape_position not on a stripe boundary\n",
+				mdname(mddev));
+			return -EINVAL;
+		}
+		reshape_offset = here_new * chunk_sectors;
+		/* here_new is the stripe we will write to */
+		here_old = mddev->reshape_position;
+		sector_div(here_old, chunk_sectors * (old_disks-max_degraded));
+		/* here_old is the first stripe that we might need to read
+		 * from */
+		if (mddev->delta_disks == 0) {
+			/* We cannot be sure it is safe to start an in-place
+			 * reshape.  It is only safe if user-space is monitoring
+			 * and taking constant backups.
+			 * mdadm always starts a situation like this in
+			 * readonly mode so it can take control before
+			 * allowing any writes.  So just check for that.
+			 */
+			if (abs(min_offset_diff) >= mddev->chunk_sectors &&
+			    abs(min_offset_diff) >= mddev->new_chunk_sectors)
+				/* not really in-place - so OK */;
+			else if (mddev->ro == 0) {
+				pr_warn("md/raid:%s: in-place reshape must be started in read-only mode - aborting\n",
+					mdname(mddev));
+				return -EINVAL;
+			}
+		} else if (mddev->reshape_backwards
+		    ? (here_new * chunk_sectors + min_offset_diff <=
+		       here_old * chunk_sectors)
+		    : (here_new * chunk_sectors >=
+		       here_old * chunk_sectors + (-min_offset_diff))) {
+			/* Reading from the same stripe as writing to - bad */
+			pr_warn("md/raid:%s: reshape_position too early for auto-recovery - aborting.\n",
+				mdname(mddev));
+			return -EINVAL;
+		}
+		pr_debug("md/raid:%s: reshape will continue\n", mdname(mddev));
+		/* OK, we should be able to continue; */
+	} else {
+		BUG_ON(mddev->level != mddev->new_level);
+		BUG_ON(mddev->layout != mddev->new_layout);
+		BUG_ON(mddev->chunk_sectors != mddev->new_chunk_sectors);
+		BUG_ON(mddev->delta_disks != 0);
+	}
+
+	if (test_bit(MD_HAS_JOURNAL, &mddev->flags) &&
+	    test_bit(MD_HAS_PPL, &mddev->flags)) {
+		pr_warn("md/raid:%s: using journal device and PPL not allowed - disabling PPL\n",
+			mdname(mddev));
+		clear_bit(MD_HAS_PPL, &mddev->flags);
+		clear_bit(MD_HAS_MULTIPLE_PPLS, &mddev->flags);
+	}
+
+	if (mddev->private == NULL)
+		conf = setup_conf(mddev);
+	else
+		conf = mddev->private;
+
+	if (IS_ERR(conf))
+		return PTR_ERR(conf);
+
+	if (test_bit(MD_HAS_JOURNAL, &mddev->flags)) {
+		if (!journal_dev) {
+			pr_warn("md/raid:%s: journal disk is missing, force array readonly\n",
+				mdname(mddev));
+			mddev->ro = 1;
+			set_disk_ro(mddev->gendisk, 1);
+		} else if (mddev->recovery_cp == MaxSector)
+			set_bit(MD_JOURNAL_CLEAN, &mddev->flags);
+	}
+
+	conf->min_offset_diff = min_offset_diff;
+	rcu_assign_pointer(mddev->thread, conf->thread);
+	rcu_assign_pointer(conf->thread, NULL);
+	mddev->private = conf;
+
+	for (i = 0; i < conf->raid_disks && conf->previous_raid_disks;
+	     i++) {
+		rdev = rdev_mdlock_deref(mddev, conf->disks[i].rdev);
+		if (!rdev && conf->disks[i].replacement) {
+			/* The replacement is all we have yet */
+			rdev = rdev_mdlock_deref(mddev,
+						 conf->disks[i].replacement);
+			conf->disks[i].replacement = NULL;
+			clear_bit(Replacement, &rdev->flags);
+			rcu_assign_pointer(conf->disks[i].rdev, rdev);
+		}
+		if (!rdev)
+			continue;
+		if (rcu_access_pointer(conf->disks[i].replacement) &&
+		    conf->reshape_progress != MaxSector) {
+			/* replacements and reshape simply do not mix. */
+			pr_warn("md: cannot handle concurrent replacement and reshape.\n");
+			goto abort;
+		}
+		if (test_bit(In_sync, &rdev->flags))
+			continue;
+		/* This disc is not fully in-sync.  However if it
+		 * just stored parity (beyond the recovery_offset),
+		 * when we don't need to be concerned about the
+		 * array being dirty.
+		 * When reshape goes 'backwards', we never have
+		 * partially completed devices, so we only need
+		 * to worry about reshape going forwards.
+		 */
+		/* Hack because v0.91 doesn't store recovery_offset properly. */
+		if (mddev->major_version == 0 &&
+		    mddev->minor_version > 90)
+			rdev->recovery_offset = reshape_offset;
+
+		if (rdev->recovery_offset < reshape_offset) {
+			/* We need to check old and new layout */
+			if (!only_parity(rdev->raid_disk,
+					 conf->algorithm,
+					 conf->raid_disks,
+					 conf->max_degraded))
+				continue;
+		}
+		if (!only_parity(rdev->raid_disk,
+				 conf->prev_algo,
+				 conf->previous_raid_disks,
+				 conf->max_degraded))
+			continue;
+		dirty_parity_disks++;
+	}
+
+	/*
+	 * 0 for a fully functional array, 1 or 2 for a degraded array.
+	 */
+	mddev->degraded = raid5_calc_degraded(conf);
+
+	if (has_failed(conf)) {
+		pr_crit("md/raid:%s: not enough operational devices (%d/%d failed)\n",
+			mdname(mddev), mddev->degraded, conf->raid_disks);
+		goto abort;
+	}
+
+	/* device size must be a multiple of chunk size */
+	mddev->dev_sectors &= ~((sector_t)mddev->chunk_sectors - 1);
+	mddev->resync_max_sectors = mddev->dev_sectors;
+
+	if (mddev->degraded > dirty_parity_disks &&
+	    mddev->recovery_cp != MaxSector) {
+		if (test_bit(MD_HAS_PPL, &mddev->flags))
+			pr_crit("md/raid:%s: starting dirty degraded array with PPL.\n",
+				mdname(mddev));
+		else if (mddev->ok_start_degraded)
+			pr_crit("md/raid:%s: starting dirty degraded array - data corruption possible.\n",
+				mdname(mddev));
+		else {
+			pr_crit("md/raid:%s: cannot start dirty degraded array.\n",
+				mdname(mddev));
+			goto abort;
+		}
+	}
+
+	pr_info("md/raid:%s: raid level %d active with %d out of %d devices, algorithm %d\n",
+		mdname(mddev), conf->level,
+		mddev->raid_disks-mddev->degraded, mddev->raid_disks,
+		mddev->new_layout);
+
+	print_raid5_conf(conf);
+
+	if (conf->reshape_progress != MaxSector) {
+		conf->reshape_safe = conf->reshape_progress;
+		atomic_set(&conf->reshape_stripes, 0);
+		clear_bit(MD_RECOVERY_SYNC, &mddev->recovery);
+		clear_bit(MD_RECOVERY_CHECK, &mddev->recovery);
+		set_bit(MD_RECOVERY_RESHAPE, &mddev->recovery);
+		set_bit(MD_RECOVERY_RUNNING, &mddev->recovery);
+		rcu_assign_pointer(mddev->sync_thread,
+			md_register_thread(md_do_sync, mddev, "reshape"));
+		if (!mddev->sync_thread)
+			goto abort;
+	}
+
+	/* Ok, everything is just fine now */
+	if (mddev->to_remove == &raid5_attrs_group)
+		mddev->to_remove = NULL;
+	else if (mddev->kobj.sd &&
+	    sysfs_create_group(&mddev->kobj, &raid5_attrs_group))
+		pr_warn("raid5: failed to create sysfs attributes for %s\n",
+			mdname(mddev));
+	md_set_array_sectors(mddev, raid5_size(mddev, 0, 0));
+
+	if (mddev->queue) {
+		int chunk_size;
+		/* read-ahead size must cover two whole stripes, which
+		 * is 2 * (datadisks) * chunksize where 'n' is the
+		 * number of raid devices
+		 */
+		int data_disks = conf->previous_raid_disks - conf->max_degraded;
+		int stripe = data_disks *
+			((mddev->chunk_sectors << 9) / PAGE_SIZE);
+
+		chunk_size = mddev->chunk_sectors << 9;
+		blk_queue_io_min(mddev->queue, chunk_size);
+		raid5_set_io_opt(conf);
+		mddev->queue->limits.raid_partial_stripes_expensive = 1;
+		/*
+		 * We can only discard a whole stripe. It doesn't make sense to
+		 * discard data disk but write parity disk
+		 */
+		stripe = stripe * PAGE_SIZE;
+		stripe = roundup_pow_of_two(stripe);
+		mddev->queue->limits.discard_granularity = stripe;
+
+		blk_queue_max_write_zeroes_sectors(mddev->queue, 0);
+
+		rdev_for_each(rdev, mddev) {
+			disk_stack_limits(mddev->gendisk, rdev->bdev,
+					  rdev->data_offset << 9);
+			disk_stack_limits(mddev->gendisk, rdev->bdev,
+					  rdev->new_data_offset << 9);
+		}
+
+		/*
+		 * zeroing is required, otherwise data
+		 * could be lost. Consider a scenario: discard a stripe
+		 * (the stripe could be inconsistent if
+		 * discard_zeroes_data is 0); write one disk of the
+		 * stripe (the stripe could be inconsistent again
+		 * depending on which disks are used to calculate
+		 * parity); the disk is broken; The stripe data of this
+		 * disk is lost.
+		 *
+		 * We only allow DISCARD if the sysadmin has confirmed that
+		 * only safe devices are in use by setting a module parameter.
+		 * A better idea might be to turn DISCARD into WRITE_ZEROES
+		 * requests, as that is required to be safe.
+		 */
+		if (!devices_handle_discard_safely ||
+		    mddev->queue->limits.max_discard_sectors < (stripe >> 9) ||
+		    mddev->queue->limits.discard_granularity < stripe)
+			blk_queue_max_discard_sectors(mddev->queue, 0);
+
+		/*
+		 * Requests require having a bitmap for each stripe.
+		 * Limit the max sectors based on this.
+		 */
+		blk_queue_max_hw_sectors(mddev->queue,
+			RAID5_MAX_REQ_STRIPES << RAID5_STRIPE_SHIFT(conf));
+
+		/* No restrictions on the number of segments in the request */
+		blk_queue_max_segments(mddev->queue, USHRT_MAX);
+	}
+
+	if (log_init(conf, journal_dev, raid5_has_ppl(conf)))
+		goto abort;
+
+	return 0;
+abort:
+	md_unregister_thread(mddev, &mddev->thread);
+	print_raid5_conf(conf);
+	free_conf(conf);
+	mddev->private = NULL;
+	pr_warn("md/raid:%s: failed to run raid set.\n", mdname(mddev));
+	return -EIO;
+}
+
+static void raid5_free(struct mddev *mddev, void *priv)
+{
+	struct r5conf *conf = priv;
+
+	free_conf(conf);
+	mddev->to_remove = &raid5_attrs_group;
+}
+
+static void raid5_status(struct seq_file *seq, struct mddev *mddev)
+{
+	struct r5conf *conf = mddev->private;
+	int i;
+
+	seq_printf(seq, " level %d, %dk chunk, algorithm %d", mddev->level,
+		conf->chunk_sectors / 2, mddev->layout);
+	seq_printf (seq, " [%d/%d] [", conf->raid_disks, conf->raid_disks - mddev->degraded);
+	rcu_read_lock();
+	for (i = 0; i < conf->raid_disks; i++) {
+		struct md_rdev *rdev = rcu_dereference(conf->disks[i].rdev);
+		seq_printf (seq, "%s", rdev && test_bit(In_sync, &rdev->flags) ? "U" : "_");
+	}
+	rcu_read_unlock();
+	seq_printf (seq, "]");
+}
+
+static void print_raid5_conf (struct r5conf *conf)
+{
+	struct md_rdev *rdev;
+	int i;
+
+	pr_debug("RAID conf printout:\n");
+	if (!conf) {
+		pr_debug("(conf==NULL)\n");
+		return;
+	}
+	pr_debug(" --- level:%d rd:%d wd:%d\n", conf->level,
+	       conf->raid_disks,
+	       conf->raid_disks - conf->mddev->degraded);
+
+	rcu_read_lock();
+	for (i = 0; i < conf->raid_disks; i++) {
+		rdev = rcu_dereference(conf->disks[i].rdev);
+		if (rdev)
+			pr_debug(" disk %d, o:%d, dev:%pg\n",
+			       i, !test_bit(Faulty, &rdev->flags),
+			       rdev->bdev);
+	}
+	rcu_read_unlock();
+}
+
+static int raid5_spare_active(struct mddev *mddev)
+{
+	int i;
+	struct r5conf *conf = mddev->private;
+	struct md_rdev *rdev, *replacement;
+	int count = 0;
+	unsigned long flags;
+
+	for (i = 0; i < conf->raid_disks; i++) {
+		rdev = rdev_mdlock_deref(mddev, conf->disks[i].rdev);
+		replacement = rdev_mdlock_deref(mddev,
+						conf->disks[i].replacement);
+		if (replacement
+		    && replacement->recovery_offset == MaxSector
+		    && !test_bit(Faulty, &replacement->flags)
+		    && !test_and_set_bit(In_sync, &replacement->flags)) {
+			/* Replacement has just become active. */
+			if (!rdev
+			    || !test_and_clear_bit(In_sync, &rdev->flags))
+				count++;
+			if (rdev) {
+				/* Replaced device not technically faulty,
+				 * but we need to be sure it gets removed
+				 * and never re-added.
+				 */
+				set_bit(Faulty, &rdev->flags);
+				sysfs_notify_dirent_safe(
+					rdev->sysfs_state);
+			}
+			sysfs_notify_dirent_safe(replacement->sysfs_state);
+		} else if (rdev
+		    && rdev->recovery_offset == MaxSector
+		    && !test_bit(Faulty, &rdev->flags)
+		    && !test_and_set_bit(In_sync, &rdev->flags)) {
+			count++;
+			sysfs_notify_dirent_safe(rdev->sysfs_state);
+		}
+	}
+	spin_lock_irqsave(&conf->device_lock, flags);
+	mddev->degraded = raid5_calc_degraded(conf);
+	spin_unlock_irqrestore(&conf->device_lock, flags);
+	print_raid5_conf(conf);
+	return count;
+}
+
+static int raid5_remove_disk(struct mddev *mddev, struct md_rdev *rdev)
+{
+	struct r5conf *conf = mddev->private;
+	int err = 0;
+	int number = rdev->raid_disk;
+	struct md_rdev __rcu **rdevp;
+	struct disk_info *p;
+	struct md_rdev *tmp;
+
+	print_raid5_conf(conf);
+	if (test_bit(Journal, &rdev->flags) && conf->log) {
+		/*
+		 * we can't wait pending write here, as this is called in
+		 * raid5d, wait will deadlock.
+		 * neilb: there is no locking about new writes here,
+		 * so this cannot be safe.
+		 */
+		if (atomic_read(&conf->active_stripes) ||
+		    atomic_read(&conf->r5c_cached_full_stripes) ||
+		    atomic_read(&conf->r5c_cached_partial_stripes)) {
+			return -EBUSY;
+		}
+		log_exit(conf);
+		return 0;
+	}
+	if (unlikely(number >= conf->pool_size))
+		return 0;
+	p = conf->disks + number;
+	if (rdev == rcu_access_pointer(p->rdev))
+		rdevp = &p->rdev;
+	else if (rdev == rcu_access_pointer(p->replacement))
+		rdevp = &p->replacement;
+	else
+		return 0;
+
+	if (number >= conf->raid_disks &&
+	    conf->reshape_progress == MaxSector)
+		clear_bit(In_sync, &rdev->flags);
+
+	if (test_bit(In_sync, &rdev->flags) ||
+	    atomic_read(&rdev->nr_pending)) {
+		err = -EBUSY;
+		goto abort;
+	}
+	/* Only remove non-faulty devices if recovery
+	 * isn't possible.
+	 */
+	if (!test_bit(Faulty, &rdev->flags) &&
+	    mddev->recovery_disabled != conf->recovery_disabled &&
+	    !has_failed(conf) &&
+	    (!rcu_access_pointer(p->replacement) ||
+	     rcu_access_pointer(p->replacement) == rdev) &&
+	    number < conf->raid_disks) {
+		err = -EBUSY;
+		goto abort;
+	}
+	*rdevp = NULL;
+	if (!test_bit(RemoveSynchronized, &rdev->flags)) {
+		lockdep_assert_held(&mddev->reconfig_mutex);
+		synchronize_rcu();
+		if (atomic_read(&rdev->nr_pending)) {
+			/* lost the race, try later */
+			err = -EBUSY;
+			rcu_assign_pointer(*rdevp, rdev);
+		}
+	}
+	if (!err) {
+		err = log_modify(conf, rdev, false);
+		if (err)
+			goto abort;
+	}
+
+	tmp = rcu_access_pointer(p->replacement);
+	if (tmp) {
+		/* We must have just cleared 'rdev' */
+		rcu_assign_pointer(p->rdev, tmp);
+		clear_bit(Replacement, &tmp->flags);
+		smp_mb(); /* Make sure other CPUs may see both as identical
+			   * but will never see neither - if they are careful
+			   */
+		rcu_assign_pointer(p->replacement, NULL);
+
+		if (!err)
+			err = log_modify(conf, tmp, true);
+	}
+
+	clear_bit(WantReplacement, &rdev->flags);
+abort:
+
+	print_raid5_conf(conf);
+	return err;
+}
+
+static int raid5_add_disk(struct mddev *mddev, struct md_rdev *rdev)
+{
+	struct r5conf *conf = mddev->private;
+	int ret, err = -EEXIST;
+	int disk;
+	struct disk_info *p;
+	struct md_rdev *tmp;
+	int first = 0;
+	int last = conf->raid_disks - 1;
+
+	if (test_bit(Journal, &rdev->flags)) {
+		if (conf->log)
+			return -EBUSY;
+
+		rdev->raid_disk = 0;
+		/*
+		 * The array is in readonly mode if journal is missing, so no
+		 * write requests running. We should be safe
+		 */
+		ret = log_init(conf, rdev, false);
+		if (ret)
+			return ret;
+
+		ret = r5l_start(conf->log);
+		if (ret)
+			return ret;
+
+		return 0;
+	}
+	if (mddev->recovery_disabled == conf->recovery_disabled)
+		return -EBUSY;
+
+	if (rdev->saved_raid_disk < 0 && has_failed(conf))
+		/* no point adding a device */
+		return -EINVAL;
+
+	if (rdev->raid_disk >= 0)
+		first = last = rdev->raid_disk;
+
+	/*
+	 * find the disk ... but prefer rdev->saved_raid_disk
+	 * if possible.
+	 */
+	if (rdev->saved_raid_disk >= first &&
+	    rdev->saved_raid_disk <= last &&
+	    conf->disks[rdev->saved_raid_disk].rdev == NULL)
+		first = rdev->saved_raid_disk;
+
+	for (disk = first; disk <= last; disk++) {
+		p = conf->disks + disk;
+		if (p->rdev == NULL) {
+			clear_bit(In_sync, &rdev->flags);
+			rdev->raid_disk = disk;
+			if (rdev->saved_raid_disk != disk)
+				conf->fullsync = 1;
+			rcu_assign_pointer(p->rdev, rdev);
+
+			err = log_modify(conf, rdev, true);
+
+			goto out;
+		}
+	}
+	for (disk = first; disk <= last; disk++) {
+		p = conf->disks + disk;
+		tmp = rdev_mdlock_deref(mddev, p->rdev);
+		if (test_bit(WantReplacement, &tmp->flags) &&
+		    mddev->reshape_position == MaxSector &&
+		    p->replacement == NULL) {
+			clear_bit(In_sync, &rdev->flags);
+			set_bit(Replacement, &rdev->flags);
+			rdev->raid_disk = disk;
+			err = 0;
+			conf->fullsync = 1;
+			rcu_assign_pointer(p->replacement, rdev);
+			break;
+		}
+	}
+out:
+	print_raid5_conf(conf);
+	return err;
+}
+
+static int raid5_resize(struct mddev *mddev, sector_t sectors)
+{
+	/* no resync is happening, and there is enough space
+	 * on all devices, so we can resize.
+	 * We need to make sure resync covers any new space.
+	 * If the array is shrinking we should possibly wait until
+	 * any io in the removed space completes, but it hardly seems
+	 * worth it.
+	 */
+	sector_t newsize;
+	struct r5conf *conf = mddev->private;
+
+	if (raid5_has_log(conf) || raid5_has_ppl(conf))
+		return -EINVAL;
+	sectors &= ~((sector_t)conf->chunk_sectors - 1);
+	newsize = raid5_size(mddev, sectors, mddev->raid_disks);
+	if (mddev->external_size &&
+	    mddev->array_sectors > newsize)
+		return -EINVAL;
+	if (mddev->bitmap) {
+		int ret = md_bitmap_resize(mddev->bitmap, sectors, 0, 0);
+		if (ret)
+			return ret;
+	}
+	md_set_array_sectors(mddev, newsize);
+	if (sectors > mddev->dev_sectors &&
+	    mddev->recovery_cp > mddev->dev_sectors) {
+		mddev->recovery_cp = mddev->dev_sectors;
+		set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
+	}
+	mddev->dev_sectors = sectors;
+	mddev->resync_max_sectors = sectors;
+	return 0;
+}
+
+static int check_stripe_cache(struct mddev *mddev)
+{
+	/* Can only proceed if there are plenty of stripe_heads.
+	 * We need a minimum of one full stripe,, and for sensible progress
+	 * it is best to have about 4 times that.
+	 * If we require 4 times, then the default 256 4K stripe_heads will
+	 * allow for chunk sizes up to 256K, which is probably OK.
+	 * If the chunk size is greater, user-space should request more
+	 * stripe_heads first.
+	 */
+	struct r5conf *conf = mddev->private;
+	if (((mddev->chunk_sectors << 9) / RAID5_STRIPE_SIZE(conf)) * 4
+	    > conf->min_nr_stripes ||
+	    ((mddev->new_chunk_sectors << 9) / RAID5_STRIPE_SIZE(conf)) * 4
+	    > conf->min_nr_stripes) {
+		pr_warn("md/raid:%s: reshape: not enough stripes.  Needed %lu\n",
+			mdname(mddev),
+			((max(mddev->chunk_sectors, mddev->new_chunk_sectors) << 9)
+			 / RAID5_STRIPE_SIZE(conf))*4);
+		return 0;
+	}
+	return 1;
+}
+
+static int check_reshape(struct mddev *mddev)
+{
+	struct r5conf *conf = mddev->private;
+
+	if (raid5_has_log(conf) || raid5_has_ppl(conf))
+		return -EINVAL;
+	if (mddev->delta_disks == 0 &&
+	    mddev->new_layout == mddev->layout &&
+	    mddev->new_chunk_sectors == mddev->chunk_sectors)
+		return 0; /* nothing to do */
+	if (has_failed(conf))
+		return -EINVAL;
+	if (mddev->delta_disks < 0 && mddev->reshape_position == MaxSector) {
+		/* We might be able to shrink, but the devices must
+		 * be made bigger first.
+		 * For raid6, 4 is the minimum size.
+		 * Otherwise 2 is the minimum
+		 */
+		int min = 2;
+		if (mddev->level == 6)
+			min = 4;
+		if (mddev->raid_disks + mddev->delta_disks < min)
+			return -EINVAL;
+	}
+
+	if (!check_stripe_cache(mddev))
+		return -ENOSPC;
+
+	if (mddev->new_chunk_sectors > mddev->chunk_sectors ||
+	    mddev->delta_disks > 0)
+		if (resize_chunks(conf,
+				  conf->previous_raid_disks
+				  + max(0, mddev->delta_disks),
+				  max(mddev->new_chunk_sectors,
+				      mddev->chunk_sectors)
+			    ) < 0)
+			return -ENOMEM;
+
+	if (conf->previous_raid_disks + mddev->delta_disks <= conf->pool_size)
+		return 0; /* never bother to shrink */
+	return resize_stripes(conf, (conf->previous_raid_disks
+				     + mddev->delta_disks));
+}
+
+static int raid5_start_reshape(struct mddev *mddev)
+{
+	struct r5conf *conf = mddev->private;
+	struct md_rdev *rdev;
+	int spares = 0;
+	int i;
+	unsigned long flags;
+
+	if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery))
+		return -EBUSY;
+
+	if (!check_stripe_cache(mddev))
+		return -ENOSPC;
+
+	if (has_failed(conf))
+		return -EINVAL;
+
+	/* raid5 can't handle concurrent reshape and recovery */
+	if (mddev->recovery_cp < MaxSector)
+		return -EBUSY;
+	for (i = 0; i < conf->raid_disks; i++)
+		if (rdev_mdlock_deref(mddev, conf->disks[i].replacement))
+			return -EBUSY;
+
+	rdev_for_each(rdev, mddev) {
+		if (!test_bit(In_sync, &rdev->flags)
+		    && !test_bit(Faulty, &rdev->flags))
+			spares++;
+	}
+
+	if (spares - mddev->degraded < mddev->delta_disks - conf->max_degraded)
+		/* Not enough devices even to make a degraded array
+		 * of that size
+		 */
+		return -EINVAL;
+
+	/* Refuse to reduce size of the array.  Any reductions in
+	 * array size must be through explicit setting of array_size
+	 * attribute.
+	 */
+	if (raid5_size(mddev, 0, conf->raid_disks + mddev->delta_disks)
+	    < mddev->array_sectors) {
+		pr_warn("md/raid:%s: array size must be reduced before number of disks\n",
+			mdname(mddev));
+		return -EINVAL;
+	}
+
+	atomic_set(&conf->reshape_stripes, 0);
+	spin_lock_irq(&conf->device_lock);
+	write_seqcount_begin(&conf->gen_lock);
+	conf->previous_raid_disks = conf->raid_disks;
+	conf->raid_disks += mddev->delta_disks;
+	conf->prev_chunk_sectors = conf->chunk_sectors;
+	conf->chunk_sectors = mddev->new_chunk_sectors;
+	conf->prev_algo = conf->algorithm;
+	conf->algorithm = mddev->new_layout;
+	conf->generation++;
+	/* Code that selects data_offset needs to see the generation update
+	 * if reshape_progress has been set - so a memory barrier needed.
+	 */
+	smp_mb();
+	if (mddev->reshape_backwards)
+		conf->reshape_progress = raid5_size(mddev, 0, 0);
+	else
+		conf->reshape_progress = 0;
+	conf->reshape_safe = conf->reshape_progress;
+	write_seqcount_end(&conf->gen_lock);
+	spin_unlock_irq(&conf->device_lock);
+
+	/* Now make sure any requests that proceeded on the assumption
+	 * the reshape wasn't running - like Discard or Read - have
+	 * completed.
+	 */
+	mddev_suspend(mddev);
+	mddev_resume(mddev);
+
+	/* Add some new drives, as many as will fit.
+	 * We know there are enough to make the newly sized array work.
+	 * Don't add devices if we are reducing the number of
+	 * devices in the array.  This is because it is not possible
+	 * to correctly record the "partially reconstructed" state of
+	 * such devices during the reshape and confusion could result.
+	 */
+	if (mddev->delta_disks >= 0) {
+		rdev_for_each(rdev, mddev)
+			if (rdev->raid_disk < 0 &&
+			    !test_bit(Faulty, &rdev->flags)) {
+				if (raid5_add_disk(mddev, rdev) == 0) {
+					if (rdev->raid_disk
+					    >= conf->previous_raid_disks)
+						set_bit(In_sync, &rdev->flags);
+					else
+						rdev->recovery_offset = 0;
+
+					/* Failure here is OK */
+					sysfs_link_rdev(mddev, rdev);
+				}
+			} else if (rdev->raid_disk >= conf->previous_raid_disks
+				   && !test_bit(Faulty, &rdev->flags)) {
+				/* This is a spare that was manually added */
+				set_bit(In_sync, &rdev->flags);
+			}
+
+		/* When a reshape changes the number of devices,
+		 * ->degraded is measured against the larger of the
+		 * pre and post number of devices.
+		 */
+		spin_lock_irqsave(&conf->device_lock, flags);
+		mddev->degraded = raid5_calc_degraded(conf);
+		spin_unlock_irqrestore(&conf->device_lock, flags);
+	}
+	mddev->raid_disks = conf->raid_disks;
+	mddev->reshape_position = conf->reshape_progress;
+	set_bit(MD_SB_CHANGE_DEVS, &mddev->sb_flags);
+
+	clear_bit(MD_RECOVERY_SYNC, &mddev->recovery);
+	clear_bit(MD_RECOVERY_CHECK, &mddev->recovery);
+	clear_bit(MD_RECOVERY_DONE, &mddev->recovery);
+	set_bit(MD_RECOVERY_RESHAPE, &mddev->recovery);
+	set_bit(MD_RECOVERY_RUNNING, &mddev->recovery);
+	rcu_assign_pointer(mddev->sync_thread,
+			   md_register_thread(md_do_sync, mddev, "reshape"));
+	if (!mddev->sync_thread) {
+		mddev->recovery = 0;
+		spin_lock_irq(&conf->device_lock);
+		write_seqcount_begin(&conf->gen_lock);
+		mddev->raid_disks = conf->raid_disks = conf->previous_raid_disks;
+		mddev->new_chunk_sectors =
+			conf->chunk_sectors = conf->prev_chunk_sectors;
+		mddev->new_layout = conf->algorithm = conf->prev_algo;
+		rdev_for_each(rdev, mddev)
+			rdev->new_data_offset = rdev->data_offset;
+		smp_wmb();
+		conf->generation --;
+		conf->reshape_progress = MaxSector;
+		mddev->reshape_position = MaxSector;
+		write_seqcount_end(&conf->gen_lock);
+		spin_unlock_irq(&conf->device_lock);
+		return -EAGAIN;
+	}
+	conf->reshape_checkpoint = jiffies;
+	md_wakeup_thread(mddev->sync_thread);
+	md_new_event();
+	return 0;
+}
+
+/* This is called from the reshape thread and should make any
+ * changes needed in 'conf'
+ */
+static void end_reshape(struct r5conf *conf)
+{
+
+	if (!test_bit(MD_RECOVERY_INTR, &conf->mddev->recovery)) {
+		struct md_rdev *rdev;
+
+		spin_lock_irq(&conf->device_lock);
+		conf->previous_raid_disks = conf->raid_disks;
+		md_finish_reshape(conf->mddev);
+		smp_wmb();
+		conf->reshape_progress = MaxSector;
+		conf->mddev->reshape_position = MaxSector;
+		rdev_for_each(rdev, conf->mddev)
+			if (rdev->raid_disk >= 0 &&
+			    !test_bit(Journal, &rdev->flags) &&
+			    !test_bit(In_sync, &rdev->flags))
+				rdev->recovery_offset = MaxSector;
+		spin_unlock_irq(&conf->device_lock);
+		wake_up(&conf->wait_for_overlap);
+
+		if (conf->mddev->queue)
+			raid5_set_io_opt(conf);
+	}
+}
+
+/* This is called from the raid5d thread with mddev_lock held.
+ * It makes config changes to the device.
+ */
+static void raid5_finish_reshape(struct mddev *mddev)
+{
+	struct r5conf *conf = mddev->private;
+	struct md_rdev *rdev;
+
+	if (!test_bit(MD_RECOVERY_INTR, &mddev->recovery)) {
+
+		if (mddev->delta_disks <= 0) {
+			int d;
+			spin_lock_irq(&conf->device_lock);
+			mddev->degraded = raid5_calc_degraded(conf);
+			spin_unlock_irq(&conf->device_lock);
+			for (d = conf->raid_disks ;
+			     d < conf->raid_disks - mddev->delta_disks;
+			     d++) {
+				rdev = rdev_mdlock_deref(mddev,
+							 conf->disks[d].rdev);
+				if (rdev)
+					clear_bit(In_sync, &rdev->flags);
+				rdev = rdev_mdlock_deref(mddev,
+						conf->disks[d].replacement);
+				if (rdev)
+					clear_bit(In_sync, &rdev->flags);
+			}
+		}
+		mddev->layout = conf->algorithm;
+		mddev->chunk_sectors = conf->chunk_sectors;
+		mddev->reshape_position = MaxSector;
+		mddev->delta_disks = 0;
+		mddev->reshape_backwards = 0;
+	}
+}
+
+static void raid5_quiesce(struct mddev *mddev, int quiesce)
+{
+	struct r5conf *conf = mddev->private;
+
+	if (quiesce) {
+		/* stop all writes */
+		lock_all_device_hash_locks_irq(conf);
+		/* '2' tells resync/reshape to pause so that all
+		 * active stripes can drain
+		 */
+		r5c_flush_cache(conf, INT_MAX);
+		/* need a memory barrier to make sure read_one_chunk() sees
+		 * quiesce started and reverts to slow (locked) path.
+		 */
+		smp_store_release(&conf->quiesce, 2);
+		wait_event_cmd(conf->wait_for_quiescent,
+				    atomic_read(&conf->active_stripes) == 0 &&
+				    atomic_read(&conf->active_aligned_reads) == 0,
+				    unlock_all_device_hash_locks_irq(conf),
+				    lock_all_device_hash_locks_irq(conf));
+		conf->quiesce = 1;
+		unlock_all_device_hash_locks_irq(conf);
+		/* allow reshape to continue */
+		wake_up(&conf->wait_for_overlap);
+	} else {
+		/* re-enable writes */
+		lock_all_device_hash_locks_irq(conf);
+		conf->quiesce = 0;
+		wake_up(&conf->wait_for_quiescent);
+		wake_up(&conf->wait_for_overlap);
+		unlock_all_device_hash_locks_irq(conf);
+	}
+	log_quiesce(conf, quiesce);
+}
+
+static void *raid45_takeover_raid0(struct mddev *mddev, int level)
+{
+	struct r0conf *raid0_conf = mddev->private;
+	sector_t sectors;
+
+	/* for raid0 takeover only one zone is supported */
+	if (raid0_conf->nr_strip_zones > 1) {
+		pr_warn("md/raid:%s: cannot takeover raid0 with more than one zone.\n",
+			mdname(mddev));
+		return ERR_PTR(-EINVAL);
+	}
+
+	sectors = raid0_conf->strip_zone[0].zone_end;
+	sector_div(sectors, raid0_conf->strip_zone[0].nb_dev);
+	mddev->dev_sectors = sectors;
+	mddev->new_level = level;
+	mddev->new_layout = ALGORITHM_PARITY_N;
+	mddev->new_chunk_sectors = mddev->chunk_sectors;
+	mddev->raid_disks += 1;
+	mddev->delta_disks = 1;
+	/* make sure it will be not marked as dirty */
+	mddev->recovery_cp = MaxSector;
+
+	return setup_conf(mddev);
+}
+
+static void *raid5_takeover_raid1(struct mddev *mddev)
+{
+	int chunksect;
+	void *ret;
+
+	if (mddev->raid_disks != 2 ||
+	    mddev->degraded > 1)
+		return ERR_PTR(-EINVAL);
+
+	/* Should check if there are write-behind devices? */
+
+	chunksect = 64*2; /* 64K by default */
+
+	/* The array must be an exact multiple of chunksize */
+	while (chunksect && (mddev->array_sectors & (chunksect-1)))
+		chunksect >>= 1;
+
+	if ((chunksect<<9) < RAID5_STRIPE_SIZE((struct r5conf *)mddev->private))
+		/* array size does not allow a suitable chunk size */
+		return ERR_PTR(-EINVAL);
+
+	mddev->new_level = 5;
+	mddev->new_layout = ALGORITHM_LEFT_SYMMETRIC;
+	mddev->new_chunk_sectors = chunksect;
+
+	ret = setup_conf(mddev);
+	if (!IS_ERR(ret))
+		mddev_clear_unsupported_flags(mddev,
+			UNSUPPORTED_MDDEV_FLAGS);
+	return ret;
+}
+
+static void *raid5_takeover_raid6(struct mddev *mddev)
+{
+	int new_layout;
+
+	switch (mddev->layout) {
+	case ALGORITHM_LEFT_ASYMMETRIC_6:
+		new_layout = ALGORITHM_LEFT_ASYMMETRIC;
+		break;
+	case ALGORITHM_RIGHT_ASYMMETRIC_6:
+		new_layout = ALGORITHM_RIGHT_ASYMMETRIC;
+		break;
+	case ALGORITHM_LEFT_SYMMETRIC_6:
+		new_layout = ALGORITHM_LEFT_SYMMETRIC;
+		break;
+	case ALGORITHM_RIGHT_SYMMETRIC_6:
+		new_layout = ALGORITHM_RIGHT_SYMMETRIC;
+		break;
+	case ALGORITHM_PARITY_0_6:
+		new_layout = ALGORITHM_PARITY_0;
+		break;
+	case ALGORITHM_PARITY_N:
+		new_layout = ALGORITHM_PARITY_N;
+		break;
+	default:
+		return ERR_PTR(-EINVAL);
+	}
+	mddev->new_level = 5;
+	mddev->new_layout = new_layout;
+	mddev->delta_disks = -1;
+	mddev->raid_disks -= 1;
+	return setup_conf(mddev);
+}
+
+static int raid5_check_reshape(struct mddev *mddev)
+{
+	/* For a 2-drive array, the layout and chunk size can be changed
+	 * immediately as not restriping is needed.
+	 * For larger arrays we record the new value - after validation
+	 * to be used by a reshape pass.
+	 */
+	struct r5conf *conf = mddev->private;
+	int new_chunk = mddev->new_chunk_sectors;
+
+	if (mddev->new_layout >= 0 && !algorithm_valid_raid5(mddev->new_layout))
+		return -EINVAL;
+	if (new_chunk > 0) {
+		if (!is_power_of_2(new_chunk))
+			return -EINVAL;
+		if (new_chunk < (PAGE_SIZE>>9))
+			return -EINVAL;
+		if (mddev->array_sectors & (new_chunk-1))
+			/* not factor of array size */
+			return -EINVAL;
+	}
+
+	/* They look valid */
+
+	if (mddev->raid_disks == 2) {
+		/* can make the change immediately */
+		if (mddev->new_layout >= 0) {
+			conf->algorithm = mddev->new_layout;
+			mddev->layout = mddev->new_layout;
+		}
+		if (new_chunk > 0) {
+			conf->chunk_sectors = new_chunk ;
+			mddev->chunk_sectors = new_chunk;
+		}
+		set_bit(MD_SB_CHANGE_DEVS, &mddev->sb_flags);
+		md_wakeup_thread(mddev->thread);
+	}
+	return check_reshape(mddev);
+}
+
+static int raid6_check_reshape(struct mddev *mddev)
+{
+	int new_chunk = mddev->new_chunk_sectors;
+
+	if (mddev->new_layout >= 0 && !algorithm_valid_raid6(mddev->new_layout))
+		return -EINVAL;
+	if (new_chunk > 0) {
+		if (!is_power_of_2(new_chunk))
+			return -EINVAL;
+		if (new_chunk < (PAGE_SIZE >> 9))
+			return -EINVAL;
+		if (mddev->array_sectors & (new_chunk-1))
+			/* not factor of array size */
+			return -EINVAL;
+	}
+
+	/* They look valid */
+	return check_reshape(mddev);
+}
+
+static void *raid5_takeover(struct mddev *mddev)
+{
+	/* raid5 can take over:
+	 *  raid0 - if there is only one strip zone - make it a raid4 layout
+	 *  raid1 - if there are two drives.  We need to know the chunk size
+	 *  raid4 - trivial - just use a raid4 layout.
+	 *  raid6 - Providing it is a *_6 layout
+	 */
+	if (mddev->level == 0)
+		return raid45_takeover_raid0(mddev, 5);
+	if (mddev->level == 1)
+		return raid5_takeover_raid1(mddev);
+	if (mddev->level == 4) {
+		mddev->new_layout = ALGORITHM_PARITY_N;
+		mddev->new_level = 5;
+		return setup_conf(mddev);
+	}
+	if (mddev->level == 6)
+		return raid5_takeover_raid6(mddev);
+
+	return ERR_PTR(-EINVAL);
+}
+
+static void *raid4_takeover(struct mddev *mddev)
+{
+	/* raid4 can take over:
+	 *  raid0 - if there is only one strip zone
+	 *  raid5 - if layout is right
+	 */
+	if (mddev->level == 0)
+		return raid45_takeover_raid0(mddev, 4);
+	if (mddev->level == 5 &&
+	    mddev->layout == ALGORITHM_PARITY_N) {
+		mddev->new_layout = 0;
+		mddev->new_level = 4;
+		return setup_conf(mddev);
+	}
+	return ERR_PTR(-EINVAL);
+}
+
+static struct md_personality raid5_personality;
+
+static void *raid6_takeover(struct mddev *mddev)
+{
+	/* Currently can only take over a raid5.  We map the
+	 * personality to an equivalent raid6 personality
+	 * with the Q block at the end.
+	 */
+	int new_layout;
+
+	if (mddev->pers != &raid5_personality)
+		return ERR_PTR(-EINVAL);
+	if (mddev->degraded > 1)
+		return ERR_PTR(-EINVAL);
+	if (mddev->raid_disks > 253)
+		return ERR_PTR(-EINVAL);
+	if (mddev->raid_disks < 3)
+		return ERR_PTR(-EINVAL);
+
+	switch (mddev->layout) {
+	case ALGORITHM_LEFT_ASYMMETRIC:
+		new_layout = ALGORITHM_LEFT_ASYMMETRIC_6;
+		break;
+	case ALGORITHM_RIGHT_ASYMMETRIC:
+		new_layout = ALGORITHM_RIGHT_ASYMMETRIC_6;
+		break;
+	case ALGORITHM_LEFT_SYMMETRIC:
+		new_layout = ALGORITHM_LEFT_SYMMETRIC_6;
+		break;
+	case ALGORITHM_RIGHT_SYMMETRIC:
+		new_layout = ALGORITHM_RIGHT_SYMMETRIC_6;
+		break;
+	case ALGORITHM_PARITY_0:
+		new_layout = ALGORITHM_PARITY_0_6;
+		break;
+	case ALGORITHM_PARITY_N:
+		new_layout = ALGORITHM_PARITY_N;
+		break;
+	default:
+		return ERR_PTR(-EINVAL);
+	}
+	mddev->new_level = 6;
+	mddev->new_layout = new_layout;
+	mddev->delta_disks = 1;
+	mddev->raid_disks += 1;
+	return setup_conf(mddev);
+}
+
+static int raid5_change_consistency_policy(struct mddev *mddev, const char *buf)
+{
+	struct r5conf *conf;
+	int err;
+
+	err = mddev_lock(mddev);
+	if (err)
+		return err;
+	conf = mddev->private;
+	if (!conf) {
+		mddev_unlock(mddev);
+		return -ENODEV;
+	}
+
+	if (strncmp(buf, "ppl", 3) == 0) {
+		/* ppl only works with RAID 5 */
+		if (!raid5_has_ppl(conf) && conf->level == 5) {
+			err = log_init(conf, NULL, true);
+			if (!err) {
+				err = resize_stripes(conf, conf->pool_size);
+				if (err) {
+					mddev_suspend(mddev);
+					log_exit(conf);
+					mddev_resume(mddev);
+				}
+			}
+		} else
+			err = -EINVAL;
+	} else if (strncmp(buf, "resync", 6) == 0) {
+		if (raid5_has_ppl(conf)) {
+			mddev_suspend(mddev);
+			log_exit(conf);
+			mddev_resume(mddev);
+			err = resize_stripes(conf, conf->pool_size);
+		} else if (test_bit(MD_HAS_JOURNAL, &conf->mddev->flags) &&
+			   r5l_log_disk_error(conf)) {
+			bool journal_dev_exists = false;
+			struct md_rdev *rdev;
+
+			rdev_for_each(rdev, mddev)
+				if (test_bit(Journal, &rdev->flags)) {
+					journal_dev_exists = true;
+					break;
+				}
+
+			if (!journal_dev_exists) {
+				mddev_suspend(mddev);
+				clear_bit(MD_HAS_JOURNAL, &mddev->flags);
+				mddev_resume(mddev);
+			} else  /* need remove journal device first */
+				err = -EBUSY;
+		} else
+			err = -EINVAL;
+	} else {
+		err = -EINVAL;
+	}
+
+	if (!err)
+		md_update_sb(mddev, 1);
+
+	mddev_unlock(mddev);
+
+	return err;
+}
+
+static int raid5_start(struct mddev *mddev)
+{
+	struct r5conf *conf = mddev->private;
+
+	return r5l_start(conf->log);
+}
+
+static void raid5_prepare_suspend(struct mddev *mddev)
+{
+	struct r5conf *conf = mddev->private;
+
+	wait_event(mddev->sb_wait, !reshape_inprogress(mddev) ||
+				    percpu_ref_is_zero(&mddev->active_io));
+	if (percpu_ref_is_zero(&mddev->active_io))
+		return;
+
+	/*
+	 * Reshape is not in progress, and array is suspended, io that is
+	 * waiting for reshpape can never be done.
+	 */
+	wake_up(&conf->wait_for_overlap);
+}
+
+static struct md_personality raid6_personality =
+{
+	.name		= "raid6",
+	.level		= 6,
+	.owner		= THIS_MODULE,
+	.make_request	= raid5_make_request,
+	.run		= raid5_run,
+	.start		= raid5_start,
+	.free		= raid5_free,
+	.status		= raid5_status,
+	.error_handler	= raid5_error,
+	.hot_add_disk	= raid5_add_disk,
+	.hot_remove_disk= raid5_remove_disk,
+	.spare_active	= raid5_spare_active,
+	.sync_request	= raid5_sync_request,
+	.resize		= raid5_resize,
+	.size		= raid5_size,
+	.check_reshape	= raid6_check_reshape,
+	.start_reshape  = raid5_start_reshape,
+	.finish_reshape = raid5_finish_reshape,
+	.prepare_suspend = raid5_prepare_suspend,
+	.quiesce	= raid5_quiesce,
+	.takeover	= raid6_takeover,
+	.change_consistency_policy = raid5_change_consistency_policy,
+};
+static struct md_personality raid5_personality =
+{
+	.name		= "raid5",
+	.level		= 5,
+	.owner		= THIS_MODULE,
+	.make_request	= raid5_make_request,
+	.run		= raid5_run,
+	.start		= raid5_start,
+	.free		= raid5_free,
+	.status		= raid5_status,
+	.error_handler	= raid5_error,
+	.hot_add_disk	= raid5_add_disk,
+	.hot_remove_disk= raid5_remove_disk,
+	.spare_active	= raid5_spare_active,
+	.sync_request	= raid5_sync_request,
+	.resize		= raid5_resize,
+	.size		= raid5_size,
+	.check_reshape	= raid5_check_reshape,
+	.start_reshape  = raid5_start_reshape,
+	.finish_reshape = raid5_finish_reshape,
+	.prepare_suspend = raid5_prepare_suspend,
+	.quiesce	= raid5_quiesce,
+	.takeover	= raid5_takeover,
+	.change_consistency_policy = raid5_change_consistency_policy,
+};
+
+static struct md_personality raid4_personality =
+{
+	.name		= "raid4",
+	.level		= 4,
+	.owner		= THIS_MODULE,
+	.make_request	= raid5_make_request,
+	.run		= raid5_run,
+	.start		= raid5_start,
+	.free		= raid5_free,
+	.status		= raid5_status,
+	.error_handler	= raid5_error,
+	.hot_add_disk	= raid5_add_disk,
+	.hot_remove_disk= raid5_remove_disk,
+	.spare_active	= raid5_spare_active,
+	.sync_request	= raid5_sync_request,
+	.resize		= raid5_resize,
+	.size		= raid5_size,
+	.check_reshape	= raid5_check_reshape,
+	.start_reshape  = raid5_start_reshape,
+	.finish_reshape = raid5_finish_reshape,
+	.prepare_suspend = raid5_prepare_suspend,
+	.quiesce	= raid5_quiesce,
+	.takeover	= raid4_takeover,
+	.change_consistency_policy = raid5_change_consistency_policy,
+};
+
+static int __init raid5_init(void)
+{
+	int ret;
+
+	raid5_wq = alloc_workqueue("raid5wq",
+		WQ_UNBOUND|WQ_MEM_RECLAIM|WQ_CPU_INTENSIVE|WQ_SYSFS, 0);
+	if (!raid5_wq)
+		return -ENOMEM;
+
+	ret = cpuhp_setup_state_multi(CPUHP_MD_RAID5_PREPARE,
+				      "md/raid5:prepare",
+				      raid456_cpu_up_prepare,
+				      raid456_cpu_dead);
+	if (ret) {
+		destroy_workqueue(raid5_wq);
+		return ret;
+	}
+	register_md_personality(&raid6_personality);
+	register_md_personality(&raid5_personality);
+	register_md_personality(&raid4_personality);
+	return 0;
+}
+
+static void raid5_exit(void)
+{
+	unregister_md_personality(&raid6_personality);
+	unregister_md_personality(&raid5_personality);
+	unregister_md_personality(&raid4_personality);
+	cpuhp_remove_multi_state(CPUHP_MD_RAID5_PREPARE);
+	destroy_workqueue(raid5_wq);
+}
+
+module_init(raid5_init);
+module_exit(raid5_exit);
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("RAID4/5/6 (striping with parity) personality for MD");
+MODULE_ALIAS("md-personality-4"); /* RAID5 */
+MODULE_ALIAS("md-raid5");
+MODULE_ALIAS("md-raid4");
+MODULE_ALIAS("md-level-5");
+MODULE_ALIAS("md-level-4");
+MODULE_ALIAS("md-personality-8"); /* RAID6 */
+MODULE_ALIAS("md-raid6");
+MODULE_ALIAS("md-level-6");
+
+/* This used to be two separate modules, they were: */
+MODULE_ALIAS("raid5");
+MODULE_ALIAS("raid6");