Adding upstream version 4.19.249.upstream/4.19.249

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

1 files changed, 1505 insertions, 0 deletions

diff --git a/drivers/md/raid5-ppl.c b/drivers/md/raid5-ppl.c
new file mode 100644
index 000000000..3a7c36326
--- /dev/null
+++ b/drivers/md/raid5-ppl.c
@@ -0,0 +1,1505 @@
+/*
+ * Partial Parity Log for closing the RAID5 write hole
+ * Copyright (c) 2017, Intel Corporation.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ */
+
+#include <linux/kernel.h>
+#include <linux/blkdev.h>
+#include <linux/slab.h>
+#include <linux/crc32c.h>
+#include <linux/flex_array.h>
+#include <linux/async_tx.h>
+#include <linux/raid/md_p.h>
+#include "md.h"
+#include "raid5.h"
+
+/*
+ * PPL consists of a 4KB header (struct ppl_header) and at least 128KB for
+ * partial parity data. The header contains an array of entries
+ * (struct ppl_header_entry) which describe the logged write requests.
+ * Partial parity for the entries comes after the header, written in the same
+ * sequence as the entries:
+ *
+ * Header
+ *   entry0
+ *   ...
+ *   entryN
+ * PP data
+ *   PP for entry0
+ *   ...
+ *   PP for entryN
+ *
+ * An entry describes one or more consecutive stripe_heads, up to a full
+ * stripe. The modifed raid data chunks form an m-by-n matrix, where m is the
+ * number of stripe_heads in the entry and n is the number of modified data
+ * disks. Every stripe_head in the entry must write to the same data disks.
+ * An example of a valid case described by a single entry (writes to the first
+ * stripe of a 4 disk array, 16k chunk size):
+ *
+ * sh->sector   dd0   dd1   dd2    ppl
+ *            +-----+-----+-----+
+ * 0          | --- | --- | --- | +----+
+ * 8          | -W- | -W- | --- | | pp |   data_sector = 8
+ * 16         | -W- | -W- | --- | | pp |   data_size = 3 * 2 * 4k
+ * 24         | -W- | -W- | --- | | pp |   pp_size = 3 * 4k
+ *            +-----+-----+-----+ +----+
+ *
+ * data_sector is the first raid sector of the modified data, data_size is the
+ * total size of modified data and pp_size is the size of partial parity for
+ * this entry. Entries for full stripe writes contain no partial parity
+ * (pp_size = 0), they only mark the stripes for which parity should be
+ * recalculated after an unclean shutdown. Every entry holds a checksum of its
+ * partial parity, the header also has a checksum of the header itself.
+ *
+ * A write request is always logged to the PPL instance stored on the parity
+ * disk of the corresponding stripe. For each member disk there is one ppl_log
+ * used to handle logging for this disk, independently from others. They are
+ * grouped in child_logs array in struct ppl_conf, which is assigned to
+ * r5conf->log_private.
+ *
+ * ppl_io_unit represents a full PPL write, header_page contains the ppl_header.
+ * PPL entries for logged stripes are added in ppl_log_stripe(). A stripe_head
+ * can be appended to the last entry if it meets the conditions for a valid
+ * entry described above, otherwise a new entry is added. Checksums of entries
+ * are calculated incrementally as stripes containing partial parity are being
+ * added. ppl_submit_iounit() calculates the checksum of the header and submits
+ * a bio containing the header page and partial parity pages (sh->ppl_page) for
+ * all stripes of the io_unit. When the PPL write completes, the stripes
+ * associated with the io_unit are released and raid5d starts writing their data
+ * and parity. When all stripes are written, the io_unit is freed and the next
+ * can be submitted.
+ *
+ * An io_unit is used to gather stripes until it is submitted or becomes full
+ * (if the maximum number of entries or size of PPL is reached). Another io_unit
+ * can't be submitted until the previous has completed (PPL and stripe
+ * data+parity is written). The log->io_list tracks all io_units of a log
+ * (for a single member disk). New io_units are added to the end of the list
+ * and the first io_unit is submitted, if it is not submitted already.
+ * The current io_unit accepting new stripes is always at the end of the list.
+ *
+ * If write-back cache is enabled for any of the disks in the array, its data
+ * must be flushed before next io_unit is submitted.
+ */
+
+#define PPL_SPACE_SIZE (128 * 1024)
+
+struct ppl_conf {
+	struct mddev *mddev;
+
+	/* array of child logs, one for each raid disk */
+	struct ppl_log *child_logs;
+	int count;
+
+	int block_size;		/* the logical block size used for data_sector
+				 * in ppl_header_entry */
+	u32 signature;		/* raid array identifier */
+	atomic64_t seq;		/* current log write sequence number */
+
+	struct kmem_cache *io_kc;
+	mempool_t io_pool;
+	struct bio_set bs;
+	struct bio_set flush_bs;
+
+	/* used only for recovery */
+	int recovered_entries;
+	int mismatch_count;
+
+	/* stripes to retry if failed to allocate io_unit */
+	struct list_head no_mem_stripes;
+	spinlock_t no_mem_stripes_lock;
+};
+
+struct ppl_log {
+	struct ppl_conf *ppl_conf;	/* shared between all log instances */
+
+	struct md_rdev *rdev;		/* array member disk associated with
+					 * this log instance */
+	struct mutex io_mutex;
+	struct ppl_io_unit *current_io;	/* current io_unit accepting new data
+					 * always at the end of io_list */
+	spinlock_t io_list_lock;
+	struct list_head io_list;	/* all io_units of this log */
+
+	sector_t next_io_sector;
+	unsigned int entry_space;
+	bool use_multippl;
+	bool wb_cache_on;
+	unsigned long disk_flush_bitmap;
+};
+
+#define PPL_IO_INLINE_BVECS 32
+
+struct ppl_io_unit {
+	struct ppl_log *log;
+
+	struct page *header_page;	/* for ppl_header */
+
+	unsigned int entries_count;	/* number of entries in ppl_header */
+	unsigned int pp_size;		/* total size current of partial parity */
+
+	u64 seq;			/* sequence number of this log write */
+	struct list_head log_sibling;	/* log->io_list */
+
+	struct list_head stripe_list;	/* stripes added to the io_unit */
+	atomic_t pending_stripes;	/* how many stripes not written to raid */
+	atomic_t pending_flushes;	/* how many disk flushes are in progress */
+
+	bool submitted;			/* true if write to log started */
+
+	/* inline bio and its biovec for submitting the iounit */
+	struct bio bio;
+	struct bio_vec biovec[PPL_IO_INLINE_BVECS];
+};
+
+struct dma_async_tx_descriptor *
+ops_run_partial_parity(struct stripe_head *sh, struct raid5_percpu *percpu,
+		       struct dma_async_tx_descriptor *tx)
+{
+	int disks = sh->disks;
+	struct page **srcs = flex_array_get(percpu->scribble, 0);
+	int count = 0, pd_idx = sh->pd_idx, i;
+	struct async_submit_ctl submit;
+
+	pr_debug("%s: stripe %llu\n", __func__, (unsigned long long)sh->sector);
+
+	/*
+	 * Partial parity is the XOR of stripe data chunks that are not changed
+	 * during the write request. Depending on available data
+	 * (read-modify-write vs. reconstruct-write case) we calculate it
+	 * differently.
+	 */
+	if (sh->reconstruct_state == reconstruct_state_prexor_drain_run) {
+		/*
+		 * rmw: xor old data and parity from updated disks
+		 * This is calculated earlier by ops_run_prexor5() so just copy
+		 * the parity dev page.
+		 */
+		srcs[count++] = sh->dev[pd_idx].page;
+	} else if (sh->reconstruct_state == reconstruct_state_drain_run) {
+		/* rcw: xor data from all not updated disks */
+		for (i = disks; i--;) {
+			struct r5dev *dev = &sh->dev[i];
+			if (test_bit(R5_UPTODATE, &dev->flags))
+				srcs[count++] = dev->page;
+		}
+	} else {
+		return tx;
+	}
+
+	init_async_submit(&submit, ASYNC_TX_FENCE|ASYNC_TX_XOR_ZERO_DST, tx,
+			  NULL, sh, flex_array_get(percpu->scribble, 0)
+			  + sizeof(struct page *) * (sh->disks + 2));
+
+	if (count == 1)
+		tx = async_memcpy(sh->ppl_page, srcs[0], 0, 0, PAGE_SIZE,
+				  &submit);
+	else
+		tx = async_xor(sh->ppl_page, srcs, 0, count, PAGE_SIZE,
+			       &submit);
+
+	return tx;
+}
+
+static void *ppl_io_pool_alloc(gfp_t gfp_mask, void *pool_data)
+{
+	struct kmem_cache *kc = pool_data;
+	struct ppl_io_unit *io;
+
+	io = kmem_cache_alloc(kc, gfp_mask);
+	if (!io)
+		return NULL;
+
+	io->header_page = alloc_page(gfp_mask);
+	if (!io->header_page) {
+		kmem_cache_free(kc, io);
+		return NULL;
+	}
+
+	return io;
+}
+
+static void ppl_io_pool_free(void *element, void *pool_data)
+{
+	struct kmem_cache *kc = pool_data;
+	struct ppl_io_unit *io = element;
+
+	__free_page(io->header_page);
+	kmem_cache_free(kc, io);
+}
+
+static struct ppl_io_unit *ppl_new_iounit(struct ppl_log *log,
+					  struct stripe_head *sh)
+{
+	struct ppl_conf *ppl_conf = log->ppl_conf;
+	struct ppl_io_unit *io;
+	struct ppl_header *pplhdr;
+	struct page *header_page;
+
+	io = mempool_alloc(&ppl_conf->io_pool, GFP_NOWAIT);
+	if (!io)
+		return NULL;
+
+	header_page = io->header_page;
+	memset(io, 0, sizeof(*io));
+	io->header_page = header_page;
+
+	io->log = log;
+	INIT_LIST_HEAD(&io->log_sibling);
+	INIT_LIST_HEAD(&io->stripe_list);
+	atomic_set(&io->pending_stripes, 0);
+	atomic_set(&io->pending_flushes, 0);
+	bio_init(&io->bio, io->biovec, PPL_IO_INLINE_BVECS);
+
+	pplhdr = page_address(io->header_page);
+	clear_page(pplhdr);
+	memset(pplhdr->reserved, 0xff, PPL_HDR_RESERVED);
+	pplhdr->signature = cpu_to_le32(ppl_conf->signature);
+
+	io->seq = atomic64_add_return(1, &ppl_conf->seq);
+	pplhdr->generation = cpu_to_le64(io->seq);
+
+	return io;
+}
+
+static int ppl_log_stripe(struct ppl_log *log, struct stripe_head *sh)
+{
+	struct ppl_io_unit *io = log->current_io;
+	struct ppl_header_entry *e = NULL;
+	struct ppl_header *pplhdr;
+	int i;
+	sector_t data_sector = 0;
+	int data_disks = 0;
+	struct r5conf *conf = sh->raid_conf;
+
+	pr_debug("%s: stripe: %llu\n", __func__, (unsigned long long)sh->sector);
+
+	/* check if current io_unit is full */
+	if (io && (io->pp_size == log->entry_space ||
+		   io->entries_count == PPL_HDR_MAX_ENTRIES)) {
+		pr_debug("%s: add io_unit blocked by seq: %llu\n",
+			 __func__, io->seq);
+		io = NULL;
+	}
+
+	/* add a new unit if there is none or the current is full */
+	if (!io) {
+		io = ppl_new_iounit(log, sh);
+		if (!io)
+			return -ENOMEM;
+		spin_lock_irq(&log->io_list_lock);
+		list_add_tail(&io->log_sibling, &log->io_list);
+		spin_unlock_irq(&log->io_list_lock);
+
+		log->current_io = io;
+	}
+
+	for (i = 0; i < sh->disks; i++) {
+		struct r5dev *dev = &sh->dev[i];
+
+		if (i != sh->pd_idx && test_bit(R5_Wantwrite, &dev->flags)) {
+			if (!data_disks || dev->sector < data_sector)
+				data_sector = dev->sector;
+			data_disks++;
+		}
+	}
+	BUG_ON(!data_disks);
+
+	pr_debug("%s: seq: %llu data_sector: %llu data_disks: %d\n", __func__,
+		 io->seq, (unsigned long long)data_sector, data_disks);
+
+	pplhdr = page_address(io->header_page);
+
+	if (io->entries_count > 0) {
+		struct ppl_header_entry *last =
+				&pplhdr->entries[io->entries_count - 1];
+		struct stripe_head *sh_last = list_last_entry(
+				&io->stripe_list, struct stripe_head, log_list);
+		u64 data_sector_last = le64_to_cpu(last->data_sector);
+		u32 data_size_last = le32_to_cpu(last->data_size);
+
+		/*
+		 * Check if we can append the stripe to the last entry. It must
+		 * be just after the last logged stripe and write to the same
+		 * disks. Use bit shift and logarithm to avoid 64-bit division.
+		 */
+		if ((sh->sector == sh_last->sector + STRIPE_SECTORS) &&
+		    (data_sector >> ilog2(conf->chunk_sectors) ==
+		     data_sector_last >> ilog2(conf->chunk_sectors)) &&
+		    ((data_sector - data_sector_last) * data_disks ==
+		     data_size_last >> 9))
+			e = last;
+	}
+
+	if (!e) {
+		e = &pplhdr->entries[io->entries_count++];
+		e->data_sector = cpu_to_le64(data_sector);
+		e->parity_disk = cpu_to_le32(sh->pd_idx);
+		e->checksum = cpu_to_le32(~0);
+	}
+
+	le32_add_cpu(&e->data_size, data_disks << PAGE_SHIFT);
+
+	/* don't write any PP if full stripe write */
+	if (!test_bit(STRIPE_FULL_WRITE, &sh->state)) {
+		le32_add_cpu(&e->pp_size, PAGE_SIZE);
+		io->pp_size += PAGE_SIZE;
+		e->checksum = cpu_to_le32(crc32c_le(le32_to_cpu(e->checksum),
+						    page_address(sh->ppl_page),
+						    PAGE_SIZE));
+	}
+
+	list_add_tail(&sh->log_list, &io->stripe_list);
+	atomic_inc(&io->pending_stripes);
+	sh->ppl_io = io;
+
+	return 0;
+}
+
+int ppl_write_stripe(struct r5conf *conf, struct stripe_head *sh)
+{
+	struct ppl_conf *ppl_conf = conf->log_private;
+	struct ppl_io_unit *io = sh->ppl_io;
+	struct ppl_log *log;
+
+	if (io || test_bit(STRIPE_SYNCING, &sh->state) || !sh->ppl_page ||
+	    !test_bit(R5_Wantwrite, &sh->dev[sh->pd_idx].flags) ||
+	    !test_bit(R5_Insync, &sh->dev[sh->pd_idx].flags)) {
+		clear_bit(STRIPE_LOG_TRAPPED, &sh->state);
+		return -EAGAIN;
+	}
+
+	log = &ppl_conf->child_logs[sh->pd_idx];
+
+	mutex_lock(&log->io_mutex);
+
+	if (!log->rdev || test_bit(Faulty, &log->rdev->flags)) {
+		mutex_unlock(&log->io_mutex);
+		return -EAGAIN;
+	}
+
+	set_bit(STRIPE_LOG_TRAPPED, &sh->state);
+	clear_bit(STRIPE_DELAYED, &sh->state);
+	atomic_inc(&sh->count);
+
+	if (ppl_log_stripe(log, sh)) {
+		spin_lock_irq(&ppl_conf->no_mem_stripes_lock);
+		list_add_tail(&sh->log_list, &ppl_conf->no_mem_stripes);
+		spin_unlock_irq(&ppl_conf->no_mem_stripes_lock);
+	}
+
+	mutex_unlock(&log->io_mutex);
+
+	return 0;
+}
+
+static void ppl_log_endio(struct bio *bio)
+{
+	struct ppl_io_unit *io = bio->bi_private;
+	struct ppl_log *log = io->log;
+	struct ppl_conf *ppl_conf = log->ppl_conf;
+	struct stripe_head *sh, *next;
+
+	pr_debug("%s: seq: %llu\n", __func__, io->seq);
+
+	if (bio->bi_status)
+		md_error(ppl_conf->mddev, log->rdev);
+
+	list_for_each_entry_safe(sh, next, &io->stripe_list, log_list) {
+		list_del_init(&sh->log_list);
+
+		set_bit(STRIPE_HANDLE, &sh->state);
+		raid5_release_stripe(sh);
+	}
+}
+
+static void ppl_submit_iounit_bio(struct ppl_io_unit *io, struct bio *bio)
+{
+	char b[BDEVNAME_SIZE];
+
+	pr_debug("%s: seq: %llu size: %u sector: %llu dev: %s\n",
+		 __func__, io->seq, bio->bi_iter.bi_size,
+		 (unsigned long long)bio->bi_iter.bi_sector,
+		 bio_devname(bio, b));
+
+	submit_bio(bio);
+}
+
+static void ppl_submit_iounit(struct ppl_io_unit *io)
+{
+	struct ppl_log *log = io->log;
+	struct ppl_conf *ppl_conf = log->ppl_conf;
+	struct ppl_header *pplhdr = page_address(io->header_page);
+	struct bio *bio = &io->bio;
+	struct stripe_head *sh;
+	int i;
+
+	bio->bi_private = io;
+
+	if (!log->rdev || test_bit(Faulty, &log->rdev->flags)) {
+		ppl_log_endio(bio);
+		return;
+	}
+
+	for (i = 0; i < io->entries_count; i++) {
+		struct ppl_header_entry *e = &pplhdr->entries[i];
+
+		pr_debug("%s: seq: %llu entry: %d data_sector: %llu pp_size: %u data_size: %u\n",
+			 __func__, io->seq, i, le64_to_cpu(e->data_sector),
+			 le32_to_cpu(e->pp_size), le32_to_cpu(e->data_size));
+
+		e->data_sector = cpu_to_le64(le64_to_cpu(e->data_sector) >>
+					     ilog2(ppl_conf->block_size >> 9));
+		e->checksum = cpu_to_le32(~le32_to_cpu(e->checksum));
+	}
+
+	pplhdr->entries_count = cpu_to_le32(io->entries_count);
+	pplhdr->checksum = cpu_to_le32(~crc32c_le(~0, pplhdr, PPL_HEADER_SIZE));
+
+	/* Rewind the buffer if current PPL is larger then remaining space */
+	if (log->use_multippl &&
+	    log->rdev->ppl.sector + log->rdev->ppl.size - log->next_io_sector <
+	    (PPL_HEADER_SIZE + io->pp_size) >> 9)
+		log->next_io_sector = log->rdev->ppl.sector;
+
+
+	bio->bi_end_io = ppl_log_endio;
+	bio->bi_opf = REQ_OP_WRITE | REQ_FUA;
+	bio_set_dev(bio, log->rdev->bdev);
+	bio->bi_iter.bi_sector = log->next_io_sector;
+	bio_add_page(bio, io->header_page, PAGE_SIZE, 0);
+
+	pr_debug("%s: log->current_io_sector: %llu\n", __func__,
+	    (unsigned long long)log->next_io_sector);
+
+	if (log->use_multippl)
+		log->next_io_sector += (PPL_HEADER_SIZE + io->pp_size) >> 9;
+
+	WARN_ON(log->disk_flush_bitmap != 0);
+
+	list_for_each_entry(sh, &io->stripe_list, log_list) {
+		for (i = 0; i < sh->disks; i++) {
+			struct r5dev *dev = &sh->dev[i];
+
+			if ((ppl_conf->child_logs[i].wb_cache_on) &&
+			    (test_bit(R5_Wantwrite, &dev->flags))) {
+				set_bit(i, &log->disk_flush_bitmap);
+			}
+		}
+
+		/* entries for full stripe writes have no partial parity */
+		if (test_bit(STRIPE_FULL_WRITE, &sh->state))
+			continue;
+
+		if (!bio_add_page(bio, sh->ppl_page, PAGE_SIZE, 0)) {
+			struct bio *prev = bio;
+
+			bio = bio_alloc_bioset(GFP_NOIO, BIO_MAX_PAGES,
+					       &ppl_conf->bs);
+			bio->bi_opf = prev->bi_opf;
+			bio_copy_dev(bio, prev);
+			bio->bi_iter.bi_sector = bio_end_sector(prev);
+			bio_add_page(bio, sh->ppl_page, PAGE_SIZE, 0);
+
+			bio_chain(bio, prev);
+			ppl_submit_iounit_bio(io, prev);
+		}
+	}
+
+	ppl_submit_iounit_bio(io, bio);
+}
+
+static void ppl_submit_current_io(struct ppl_log *log)
+{
+	struct ppl_io_unit *io;
+
+	spin_lock_irq(&log->io_list_lock);
+
+	io = list_first_entry_or_null(&log->io_list, struct ppl_io_unit,
+				      log_sibling);
+	if (io && io->submitted)
+		io = NULL;
+
+	spin_unlock_irq(&log->io_list_lock);
+
+	if (io) {
+		io->submitted = true;
+
+		if (io == log->current_io)
+			log->current_io = NULL;
+
+		ppl_submit_iounit(io);
+	}
+}
+
+void ppl_write_stripe_run(struct r5conf *conf)
+{
+	struct ppl_conf *ppl_conf = conf->log_private;
+	struct ppl_log *log;
+	int i;
+
+	for (i = 0; i < ppl_conf->count; i++) {
+		log = &ppl_conf->child_logs[i];
+
+		mutex_lock(&log->io_mutex);
+		ppl_submit_current_io(log);
+		mutex_unlock(&log->io_mutex);
+	}
+}
+
+static void ppl_io_unit_finished(struct ppl_io_unit *io)
+{
+	struct ppl_log *log = io->log;
+	struct ppl_conf *ppl_conf = log->ppl_conf;
+	struct r5conf *conf = ppl_conf->mddev->private;
+	unsigned long flags;
+
+	pr_debug("%s: seq: %llu\n", __func__, io->seq);
+
+	local_irq_save(flags);
+
+	spin_lock(&log->io_list_lock);
+	list_del(&io->log_sibling);
+	spin_unlock(&log->io_list_lock);
+
+	mempool_free(io, &ppl_conf->io_pool);
+
+	spin_lock(&ppl_conf->no_mem_stripes_lock);
+	if (!list_empty(&ppl_conf->no_mem_stripes)) {
+		struct stripe_head *sh;
+
+		sh = list_first_entry(&ppl_conf->no_mem_stripes,
+				      struct stripe_head, log_list);
+		list_del_init(&sh->log_list);
+		set_bit(STRIPE_HANDLE, &sh->state);
+		raid5_release_stripe(sh);
+	}
+	spin_unlock(&ppl_conf->no_mem_stripes_lock);
+
+	local_irq_restore(flags);
+
+	wake_up(&conf->wait_for_quiescent);
+}
+
+static void ppl_flush_endio(struct bio *bio)
+{
+	struct ppl_io_unit *io = bio->bi_private;
+	struct ppl_log *log = io->log;
+	struct ppl_conf *ppl_conf = log->ppl_conf;
+	struct r5conf *conf = ppl_conf->mddev->private;
+	char b[BDEVNAME_SIZE];
+
+	pr_debug("%s: dev: %s\n", __func__, bio_devname(bio, b));
+
+	if (bio->bi_status) {
+		struct md_rdev *rdev;
+
+		rcu_read_lock();
+		rdev = md_find_rdev_rcu(conf->mddev, bio_dev(bio));
+		if (rdev)
+			md_error(rdev->mddev, rdev);
+		rcu_read_unlock();
+	}
+
+	bio_put(bio);
+
+	if (atomic_dec_and_test(&io->pending_flushes)) {
+		ppl_io_unit_finished(io);
+		md_wakeup_thread(conf->mddev->thread);
+	}
+}
+
+static void ppl_do_flush(struct ppl_io_unit *io)
+{
+	struct ppl_log *log = io->log;
+	struct ppl_conf *ppl_conf = log->ppl_conf;
+	struct r5conf *conf = ppl_conf->mddev->private;
+	int raid_disks = conf->raid_disks;
+	int flushed_disks = 0;
+	int i;
+
+	atomic_set(&io->pending_flushes, raid_disks);
+
+	for_each_set_bit(i, &log->disk_flush_bitmap, raid_disks) {
+		struct md_rdev *rdev;
+		struct block_device *bdev = NULL;
+
+		rcu_read_lock();
+		rdev = rcu_dereference(conf->disks[i].rdev);
+		if (rdev && !test_bit(Faulty, &rdev->flags))
+			bdev = rdev->bdev;
+		rcu_read_unlock();
+
+		if (bdev) {
+			struct bio *bio;
+			char b[BDEVNAME_SIZE];
+
+			bio = bio_alloc_bioset(GFP_NOIO, 0, &ppl_conf->flush_bs);
+			bio_set_dev(bio, bdev);
+			bio->bi_private = io;
+			bio->bi_opf = REQ_OP_WRITE | REQ_PREFLUSH;
+			bio->bi_end_io = ppl_flush_endio;
+
+			pr_debug("%s: dev: %s\n", __func__,
+				 bio_devname(bio, b));
+
+			submit_bio(bio);
+			flushed_disks++;
+		}
+	}
+
+	log->disk_flush_bitmap = 0;
+
+	for (i = flushed_disks ; i < raid_disks; i++) {
+		if (atomic_dec_and_test(&io->pending_flushes))
+			ppl_io_unit_finished(io);
+	}
+}
+
+static inline bool ppl_no_io_unit_submitted(struct r5conf *conf,
+					    struct ppl_log *log)
+{
+	struct ppl_io_unit *io;
+
+	io = list_first_entry_or_null(&log->io_list, struct ppl_io_unit,
+				      log_sibling);
+
+	return !io || !io->submitted;
+}
+
+void ppl_quiesce(struct r5conf *conf, int quiesce)
+{
+	struct ppl_conf *ppl_conf = conf->log_private;
+	int i;
+
+	if (quiesce) {
+		for (i = 0; i < ppl_conf->count; i++) {
+			struct ppl_log *log = &ppl_conf->child_logs[i];
+
+			spin_lock_irq(&log->io_list_lock);
+			wait_event_lock_irq(conf->wait_for_quiescent,
+					    ppl_no_io_unit_submitted(conf, log),
+					    log->io_list_lock);
+			spin_unlock_irq(&log->io_list_lock);
+		}
+	}
+}
+
+int ppl_handle_flush_request(struct r5l_log *log, struct bio *bio)
+{
+	if (bio->bi_iter.bi_size == 0) {
+		bio_endio(bio);
+		return 0;
+	}
+	bio->bi_opf &= ~REQ_PREFLUSH;
+	return -EAGAIN;
+}
+
+void ppl_stripe_write_finished(struct stripe_head *sh)
+{
+	struct ppl_io_unit *io;
+
+	io = sh->ppl_io;
+	sh->ppl_io = NULL;
+
+	if (io && atomic_dec_and_test(&io->pending_stripes)) {
+		if (io->log->disk_flush_bitmap)
+			ppl_do_flush(io);
+		else
+			ppl_io_unit_finished(io);
+	}
+}
+
+static void ppl_xor(int size, struct page *page1, struct page *page2)
+{
+	struct async_submit_ctl submit;
+	struct dma_async_tx_descriptor *tx;
+	struct page *xor_srcs[] = { page1, page2 };
+
+	init_async_submit(&submit, ASYNC_TX_ACK|ASYNC_TX_XOR_DROP_DST,
+			  NULL, NULL, NULL, NULL);
+	tx = async_xor(page1, xor_srcs, 0, 2, size, &submit);
+
+	async_tx_quiesce(&tx);
+}
+
+/*
+ * PPL recovery strategy: xor partial parity and data from all modified data
+ * disks within a stripe and write the result as the new stripe parity. If all
+ * stripe data disks are modified (full stripe write), no partial parity is
+ * available, so just xor the data disks.
+ *
+ * Recovery of a PPL entry shall occur only if all modified data disks are
+ * available and read from all of them succeeds.
+ *
+ * A PPL entry applies to a stripe, partial parity size for an entry is at most
+ * the size of the chunk. Examples of possible cases for a single entry:
+ *
+ * case 0: single data disk write:
+ *   data0    data1    data2     ppl        parity
+ * +--------+--------+--------+           +--------------------+
+ * | ------ | ------ | ------ | +----+    | (no change)        |
+ * | ------ | -data- | ------ | | pp | -> | data1 ^ pp         |
+ * | ------ | -data- | ------ | | pp | -> | data1 ^ pp         |
+ * | ------ | ------ | ------ | +----+    | (no change)        |
+ * +--------+--------+--------+           +--------------------+
+ * pp_size = data_size
+ *
+ * case 1: more than one data disk write:
+ *   data0    data1    data2     ppl        parity
+ * +--------+--------+--------+           +--------------------+
+ * | ------ | ------ | ------ | +----+    | (no change)        |
+ * | -data- | -data- | ------ | | pp | -> | data0 ^ data1 ^ pp |
+ * | -data- | -data- | ------ | | pp | -> | data0 ^ data1 ^ pp |
+ * | ------ | ------ | ------ | +----+    | (no change)        |
+ * +--------+--------+--------+           +--------------------+
+ * pp_size = data_size / modified_data_disks
+ *
+ * case 2: write to all data disks (also full stripe write):
+ *   data0    data1    data2                parity
+ * +--------+--------+--------+           +--------------------+
+ * | ------ | ------ | ------ |           | (no change)        |
+ * | -data- | -data- | -data- | --------> | xor all data       |
+ * | ------ | ------ | ------ | --------> | (no change)        |
+ * | ------ | ------ | ------ |           | (no change)        |
+ * +--------+--------+--------+           +--------------------+
+ * pp_size = 0
+ *
+ * The following cases are possible only in other implementations. The recovery
+ * code can handle them, but they are not generated at runtime because they can
+ * be reduced to cases 0, 1 and 2:
+ *
+ * case 3:
+ *   data0    data1    data2     ppl        parity
+ * +--------+--------+--------+ +----+    +--------------------+
+ * | ------ | -data- | -data- | | pp |    | data1 ^ data2 ^ pp |
+ * | ------ | -data- | -data- | | pp | -> | data1 ^ data2 ^ pp |
+ * | -data- | -data- | -data- | | -- | -> | xor all data       |
+ * | -data- | -data- | ------ | | pp |    | data0 ^ data1 ^ pp |
+ * +--------+--------+--------+ +----+    +--------------------+
+ * pp_size = chunk_size
+ *
+ * case 4:
+ *   data0    data1    data2     ppl        parity
+ * +--------+--------+--------+ +----+    +--------------------+
+ * | ------ | -data- | ------ | | pp |    | data1 ^ pp         |
+ * | ------ | ------ | ------ | | -- | -> | (no change)        |
+ * | ------ | ------ | ------ | | -- | -> | (no change)        |
+ * | -data- | ------ | ------ | | pp |    | data0 ^ pp         |
+ * +--------+--------+--------+ +----+    +--------------------+
+ * pp_size = chunk_size
+ */
+static int ppl_recover_entry(struct ppl_log *log, struct ppl_header_entry *e,
+			     sector_t ppl_sector)
+{
+	struct ppl_conf *ppl_conf = log->ppl_conf;
+	struct mddev *mddev = ppl_conf->mddev;
+	struct r5conf *conf = mddev->private;
+	int block_size = ppl_conf->block_size;
+	struct page *page1;
+	struct page *page2;
+	sector_t r_sector_first;
+	sector_t r_sector_last;
+	int strip_sectors;
+	int data_disks;
+	int i;
+	int ret = 0;
+	char b[BDEVNAME_SIZE];
+	unsigned int pp_size = le32_to_cpu(e->pp_size);
+	unsigned int data_size = le32_to_cpu(e->data_size);
+
+	page1 = alloc_page(GFP_KERNEL);
+	page2 = alloc_page(GFP_KERNEL);
+
+	if (!page1 || !page2) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	r_sector_first = le64_to_cpu(e->data_sector) * (block_size >> 9);
+
+	if ((pp_size >> 9) < conf->chunk_sectors) {
+		if (pp_size > 0) {
+			data_disks = data_size / pp_size;
+			strip_sectors = pp_size >> 9;
+		} else {
+			data_disks = conf->raid_disks - conf->max_degraded;
+			strip_sectors = (data_size >> 9) / data_disks;
+		}
+		r_sector_last = r_sector_first +
+				(data_disks - 1) * conf->chunk_sectors +
+				strip_sectors;
+	} else {
+		data_disks = conf->raid_disks - conf->max_degraded;
+		strip_sectors = conf->chunk_sectors;
+		r_sector_last = r_sector_first + (data_size >> 9);
+	}
+
+	pr_debug("%s: array sector first: %llu last: %llu\n", __func__,
+		 (unsigned long long)r_sector_first,
+		 (unsigned long long)r_sector_last);
+
+	/* if start and end is 4k aligned, use a 4k block */
+	if (block_size == 512 &&
+	    (r_sector_first & (STRIPE_SECTORS - 1)) == 0 &&
+	    (r_sector_last & (STRIPE_SECTORS - 1)) == 0)
+		block_size = STRIPE_SIZE;
+
+	/* iterate through blocks in strip */
+	for (i = 0; i < strip_sectors; i += (block_size >> 9)) {
+		bool update_parity = false;
+		sector_t parity_sector;
+		struct md_rdev *parity_rdev;
+		struct stripe_head sh;
+		int disk;
+		int indent = 0;
+
+		pr_debug("%s:%*s iter %d start\n", __func__, indent, "", i);
+		indent += 2;
+
+		memset(page_address(page1), 0, PAGE_SIZE);
+
+		/* iterate through data member disks */
+		for (disk = 0; disk < data_disks; disk++) {
+			int dd_idx;
+			struct md_rdev *rdev;
+			sector_t sector;
+			sector_t r_sector = r_sector_first + i +
+					    (disk * conf->chunk_sectors);
+
+			pr_debug("%s:%*s data member disk %d start\n",
+				 __func__, indent, "", disk);
+			indent += 2;
+
+			if (r_sector >= r_sector_last) {
+				pr_debug("%s:%*s array sector %llu doesn't need parity update\n",
+					 __func__, indent, "",
+					 (unsigned long long)r_sector);
+				indent -= 2;
+				continue;
+			}
+
+			update_parity = true;
+
+			/* map raid sector to member disk */
+			sector = raid5_compute_sector(conf, r_sector, 0,
+						      &dd_idx, NULL);
+			pr_debug("%s:%*s processing array sector %llu => data member disk %d, sector %llu\n",
+				 __func__, indent, "",
+				 (unsigned long long)r_sector, dd_idx,
+				 (unsigned long long)sector);
+
+			rdev = conf->disks[dd_idx].rdev;
+			if (!rdev || (!test_bit(In_sync, &rdev->flags) &&
+				      sector >= rdev->recovery_offset)) {
+				pr_debug("%s:%*s data member disk %d missing\n",
+					 __func__, indent, "", dd_idx);
+				update_parity = false;
+				break;
+			}
+
+			pr_debug("%s:%*s reading data member disk %s sector %llu\n",
+				 __func__, indent, "", bdevname(rdev->bdev, b),
+				 (unsigned long long)sector);
+			if (!sync_page_io(rdev, sector, block_size, page2,
+					REQ_OP_READ, 0, false)) {
+				md_error(mddev, rdev);
+				pr_debug("%s:%*s read failed!\n", __func__,
+					 indent, "");
+				ret = -EIO;
+				goto out;
+			}
+
+			ppl_xor(block_size, page1, page2);
+
+			indent -= 2;
+		}
+
+		if (!update_parity)
+			continue;
+
+		if (pp_size > 0) {
+			pr_debug("%s:%*s reading pp disk sector %llu\n",
+				 __func__, indent, "",
+				 (unsigned long long)(ppl_sector + i));
+			if (!sync_page_io(log->rdev,
+					ppl_sector - log->rdev->data_offset + i,
+					block_size, page2, REQ_OP_READ, 0,
+					false)) {
+				pr_debug("%s:%*s read failed!\n", __func__,
+					 indent, "");
+				md_error(mddev, log->rdev);
+				ret = -EIO;
+				goto out;
+			}
+
+			ppl_xor(block_size, page1, page2);
+		}
+
+		/* map raid sector to parity disk */
+		parity_sector = raid5_compute_sector(conf, r_sector_first + i,
+				0, &disk, &sh);
+		BUG_ON(sh.pd_idx != le32_to_cpu(e->parity_disk));
+		parity_rdev = conf->disks[sh.pd_idx].rdev;
+
+		BUG_ON(parity_rdev->bdev->bd_dev != log->rdev->bdev->bd_dev);
+		pr_debug("%s:%*s write parity at sector %llu, disk %s\n",
+			 __func__, indent, "",
+			 (unsigned long long)parity_sector,
+			 bdevname(parity_rdev->bdev, b));
+		if (!sync_page_io(parity_rdev, parity_sector, block_size,
+				page1, REQ_OP_WRITE, 0, false)) {
+			pr_debug("%s:%*s parity write error!\n", __func__,
+				 indent, "");
+			md_error(mddev, parity_rdev);
+			ret = -EIO;
+			goto out;
+		}
+	}
+out:
+	if (page1)
+		__free_page(page1);
+	if (page2)
+		__free_page(page2);
+	return ret;
+}
+
+static int ppl_recover(struct ppl_log *log, struct ppl_header *pplhdr,
+		       sector_t offset)
+{
+	struct ppl_conf *ppl_conf = log->ppl_conf;
+	struct md_rdev *rdev = log->rdev;
+	struct mddev *mddev = rdev->mddev;
+	sector_t ppl_sector = rdev->ppl.sector + offset +
+			      (PPL_HEADER_SIZE >> 9);
+	struct page *page;
+	int i;
+	int ret = 0;
+
+	page = alloc_page(GFP_KERNEL);
+	if (!page)
+		return -ENOMEM;
+
+	/* iterate through all PPL entries saved */
+	for (i = 0; i < le32_to_cpu(pplhdr->entries_count); i++) {
+		struct ppl_header_entry *e = &pplhdr->entries[i];
+		u32 pp_size = le32_to_cpu(e->pp_size);
+		sector_t sector = ppl_sector;
+		int ppl_entry_sectors = pp_size >> 9;
+		u32 crc, crc_stored;
+
+		pr_debug("%s: disk: %d entry: %d ppl_sector: %llu pp_size: %u\n",
+			 __func__, rdev->raid_disk, i,
+			 (unsigned long long)ppl_sector, pp_size);
+
+		crc = ~0;
+		crc_stored = le32_to_cpu(e->checksum);
+
+		/* read parial parity for this entry and calculate its checksum */
+		while (pp_size) {
+			int s = pp_size > PAGE_SIZE ? PAGE_SIZE : pp_size;
+
+			if (!sync_page_io(rdev, sector - rdev->data_offset,
+					s, page, REQ_OP_READ, 0, false)) {
+				md_error(mddev, rdev);
+				ret = -EIO;
+				goto out;
+			}
+
+			crc = crc32c_le(crc, page_address(page), s);
+
+			pp_size -= s;
+			sector += s >> 9;
+		}
+
+		crc = ~crc;
+
+		if (crc != crc_stored) {
+			/*
+			 * Don't recover this entry if the checksum does not
+			 * match, but keep going and try to recover other
+			 * entries.
+			 */
+			pr_debug("%s: ppl entry crc does not match: stored: 0x%x calculated: 0x%x\n",
+				 __func__, crc_stored, crc);
+			ppl_conf->mismatch_count++;
+		} else {
+			ret = ppl_recover_entry(log, e, ppl_sector);
+			if (ret)
+				goto out;
+			ppl_conf->recovered_entries++;
+		}
+
+		ppl_sector += ppl_entry_sectors;
+	}
+
+	/* flush the disk cache after recovery if necessary */
+	ret = blkdev_issue_flush(rdev->bdev, GFP_KERNEL, NULL);
+out:
+	__free_page(page);
+	return ret;
+}
+
+static int ppl_write_empty_header(struct ppl_log *log)
+{
+	struct page *page;
+	struct ppl_header *pplhdr;
+	struct md_rdev *rdev = log->rdev;
+	int ret = 0;
+
+	pr_debug("%s: disk: %d ppl_sector: %llu\n", __func__,
+		 rdev->raid_disk, (unsigned long long)rdev->ppl.sector);
+
+	page = alloc_page(GFP_NOIO | __GFP_ZERO);
+	if (!page)
+		return -ENOMEM;
+
+	pplhdr = page_address(page);
+	/* zero out PPL space to avoid collision with old PPLs */
+	blkdev_issue_zeroout(rdev->bdev, rdev->ppl.sector,
+			    log->rdev->ppl.size, GFP_NOIO, 0);
+	memset(pplhdr->reserved, 0xff, PPL_HDR_RESERVED);
+	pplhdr->signature = cpu_to_le32(log->ppl_conf->signature);
+	pplhdr->checksum = cpu_to_le32(~crc32c_le(~0, pplhdr, PAGE_SIZE));
+
+	if (!sync_page_io(rdev, rdev->ppl.sector - rdev->data_offset,
+			  PPL_HEADER_SIZE, page, REQ_OP_WRITE | REQ_SYNC |
+			  REQ_FUA, 0, false)) {
+		md_error(rdev->mddev, rdev);
+		ret = -EIO;
+	}
+
+	__free_page(page);
+	return ret;
+}
+
+static int ppl_load_distributed(struct ppl_log *log)
+{
+	struct ppl_conf *ppl_conf = log->ppl_conf;
+	struct md_rdev *rdev = log->rdev;
+	struct mddev *mddev = rdev->mddev;
+	struct page *page, *page2, *tmp;
+	struct ppl_header *pplhdr = NULL, *prev_pplhdr = NULL;
+	u32 crc, crc_stored;
+	u32 signature;
+	int ret = 0, i;
+	sector_t pplhdr_offset = 0, prev_pplhdr_offset = 0;
+
+	pr_debug("%s: disk: %d\n", __func__, rdev->raid_disk);
+	/* read PPL headers, find the recent one */
+	page = alloc_page(GFP_KERNEL);
+	if (!page)
+		return -ENOMEM;
+
+	page2 = alloc_page(GFP_KERNEL);
+	if (!page2) {
+		__free_page(page);
+		return -ENOMEM;
+	}
+
+	/* searching ppl area for latest ppl */
+	while (pplhdr_offset < rdev->ppl.size - (PPL_HEADER_SIZE >> 9)) {
+		if (!sync_page_io(rdev,
+				  rdev->ppl.sector - rdev->data_offset +
+				  pplhdr_offset, PAGE_SIZE, page, REQ_OP_READ,
+				  0, false)) {
+			md_error(mddev, rdev);
+			ret = -EIO;
+			/* if not able to read - don't recover any PPL */
+			pplhdr = NULL;
+			break;
+		}
+		pplhdr = page_address(page);
+
+		/* check header validity */
+		crc_stored = le32_to_cpu(pplhdr->checksum);
+		pplhdr->checksum = 0;
+		crc = ~crc32c_le(~0, pplhdr, PAGE_SIZE);
+
+		if (crc_stored != crc) {
+			pr_debug("%s: ppl header crc does not match: stored: 0x%x calculated: 0x%x (offset: %llu)\n",
+				 __func__, crc_stored, crc,
+				 (unsigned long long)pplhdr_offset);
+			pplhdr = prev_pplhdr;
+			pplhdr_offset = prev_pplhdr_offset;
+			break;
+		}
+
+		signature = le32_to_cpu(pplhdr->signature);
+
+		if (mddev->external) {
+			/*
+			 * For external metadata the header signature is set and
+			 * validated in userspace.
+			 */
+			ppl_conf->signature = signature;
+		} else if (ppl_conf->signature != signature) {
+			pr_debug("%s: ppl header signature does not match: stored: 0x%x configured: 0x%x (offset: %llu)\n",
+				 __func__, signature, ppl_conf->signature,
+				 (unsigned long long)pplhdr_offset);
+			pplhdr = prev_pplhdr;
+			pplhdr_offset = prev_pplhdr_offset;
+			break;
+		}
+
+		if (prev_pplhdr && le64_to_cpu(prev_pplhdr->generation) >
+		    le64_to_cpu(pplhdr->generation)) {
+			/* previous was newest */
+			pplhdr = prev_pplhdr;
+			pplhdr_offset = prev_pplhdr_offset;
+			break;
+		}
+
+		prev_pplhdr_offset = pplhdr_offset;
+		prev_pplhdr = pplhdr;
+
+		tmp = page;
+		page = page2;
+		page2 = tmp;
+
+		/* calculate next potential ppl offset */
+		for (i = 0; i < le32_to_cpu(pplhdr->entries_count); i++)
+			pplhdr_offset +=
+			    le32_to_cpu(pplhdr->entries[i].pp_size) >> 9;
+		pplhdr_offset += PPL_HEADER_SIZE >> 9;
+	}
+
+	/* no valid ppl found */
+	if (!pplhdr)
+		ppl_conf->mismatch_count++;
+	else
+		pr_debug("%s: latest PPL found at offset: %llu, with generation: %llu\n",
+		    __func__, (unsigned long long)pplhdr_offset,
+		    le64_to_cpu(pplhdr->generation));
+
+	/* attempt to recover from log if we are starting a dirty array */
+	if (pplhdr && !mddev->pers && mddev->recovery_cp != MaxSector)
+		ret = ppl_recover(log, pplhdr, pplhdr_offset);
+
+	/* write empty header if we are starting the array */
+	if (!ret && !mddev->pers)
+		ret = ppl_write_empty_header(log);
+
+	__free_page(page);
+	__free_page(page2);
+
+	pr_debug("%s: return: %d mismatch_count: %d recovered_entries: %d\n",
+		 __func__, ret, ppl_conf->mismatch_count,
+		 ppl_conf->recovered_entries);
+	return ret;
+}
+
+static int ppl_load(struct ppl_conf *ppl_conf)
+{
+	int ret = 0;
+	u32 signature = 0;
+	bool signature_set = false;
+	int i;
+
+	for (i = 0; i < ppl_conf->count; i++) {
+		struct ppl_log *log = &ppl_conf->child_logs[i];
+
+		/* skip missing drive */
+		if (!log->rdev)
+			continue;
+
+		ret = ppl_load_distributed(log);
+		if (ret)
+			break;
+
+		/*
+		 * For external metadata we can't check if the signature is
+		 * correct on a single drive, but we can check if it is the same
+		 * on all drives.
+		 */
+		if (ppl_conf->mddev->external) {
+			if (!signature_set) {
+				signature = ppl_conf->signature;
+				signature_set = true;
+			} else if (signature != ppl_conf->signature) {
+				pr_warn("md/raid:%s: PPL header signature does not match on all member drives\n",
+					mdname(ppl_conf->mddev));
+				ret = -EINVAL;
+				break;
+			}
+		}
+	}
+
+	pr_debug("%s: return: %d mismatch_count: %d recovered_entries: %d\n",
+		 __func__, ret, ppl_conf->mismatch_count,
+		 ppl_conf->recovered_entries);
+	return ret;
+}
+
+static void __ppl_exit_log(struct ppl_conf *ppl_conf)
+{
+	clear_bit(MD_HAS_PPL, &ppl_conf->mddev->flags);
+	clear_bit(MD_HAS_MULTIPLE_PPLS, &ppl_conf->mddev->flags);
+
+	kfree(ppl_conf->child_logs);
+
+	bioset_exit(&ppl_conf->bs);
+	bioset_exit(&ppl_conf->flush_bs);
+	mempool_exit(&ppl_conf->io_pool);
+	kmem_cache_destroy(ppl_conf->io_kc);
+
+	kfree(ppl_conf);
+}
+
+void ppl_exit_log(struct r5conf *conf)
+{
+	struct ppl_conf *ppl_conf = conf->log_private;
+
+	if (ppl_conf) {
+		__ppl_exit_log(ppl_conf);
+		conf->log_private = NULL;
+	}
+}
+
+static int ppl_validate_rdev(struct md_rdev *rdev)
+{
+	char b[BDEVNAME_SIZE];
+	int ppl_data_sectors;
+	int ppl_size_new;
+
+	/*
+	 * The configured PPL size must be enough to store
+	 * the header and (at the very least) partial parity
+	 * for one stripe. Round it down to ensure the data
+	 * space is cleanly divisible by stripe size.
+	 */
+	ppl_data_sectors = rdev->ppl.size - (PPL_HEADER_SIZE >> 9);
+
+	if (ppl_data_sectors > 0)
+		ppl_data_sectors = rounddown(ppl_data_sectors, STRIPE_SECTORS);
+
+	if (ppl_data_sectors <= 0) {
+		pr_warn("md/raid:%s: PPL space too small on %s\n",
+			mdname(rdev->mddev), bdevname(rdev->bdev, b));
+		return -ENOSPC;
+	}
+
+	ppl_size_new = ppl_data_sectors + (PPL_HEADER_SIZE >> 9);
+
+	if ((rdev->ppl.sector < rdev->data_offset &&
+	     rdev->ppl.sector + ppl_size_new > rdev->data_offset) ||
+	    (rdev->ppl.sector >= rdev->data_offset &&
+	     rdev->data_offset + rdev->sectors > rdev->ppl.sector)) {
+		pr_warn("md/raid:%s: PPL space overlaps with data on %s\n",
+			mdname(rdev->mddev), bdevname(rdev->bdev, b));
+		return -EINVAL;
+	}
+
+	if (!rdev->mddev->external &&
+	    ((rdev->ppl.offset > 0 && rdev->ppl.offset < (rdev->sb_size >> 9)) ||
+	     (rdev->ppl.offset <= 0 && rdev->ppl.offset + ppl_size_new > 0))) {
+		pr_warn("md/raid:%s: PPL space overlaps with superblock on %s\n",
+			mdname(rdev->mddev), bdevname(rdev->bdev, b));
+		return -EINVAL;
+	}
+
+	rdev->ppl.size = ppl_size_new;
+
+	return 0;
+}
+
+static void ppl_init_child_log(struct ppl_log *log, struct md_rdev *rdev)
+{
+	struct request_queue *q;
+
+	if ((rdev->ppl.size << 9) >= (PPL_SPACE_SIZE +
+				      PPL_HEADER_SIZE) * 2) {
+		log->use_multippl = true;
+		set_bit(MD_HAS_MULTIPLE_PPLS,
+			&log->ppl_conf->mddev->flags);
+		log->entry_space = PPL_SPACE_SIZE;
+	} else {
+		log->use_multippl = false;
+		log->entry_space = (log->rdev->ppl.size << 9) -
+				   PPL_HEADER_SIZE;
+	}
+	log->next_io_sector = rdev->ppl.sector;
+
+	q = bdev_get_queue(rdev->bdev);
+	if (test_bit(QUEUE_FLAG_WC, &q->queue_flags))
+		log->wb_cache_on = true;
+}
+
+int ppl_init_log(struct r5conf *conf)
+{
+	struct ppl_conf *ppl_conf;
+	struct mddev *mddev = conf->mddev;
+	int ret = 0;
+	int max_disks;
+	int i;
+
+	pr_debug("md/raid:%s: enabling distributed Partial Parity Log\n",
+		 mdname(conf->mddev));
+
+	if (PAGE_SIZE != 4096)
+		return -EINVAL;
+
+	if (mddev->level != 5) {
+		pr_warn("md/raid:%s PPL is not compatible with raid level %d\n",
+			mdname(mddev), mddev->level);
+		return -EINVAL;
+	}
+
+	if (mddev->bitmap_info.file || mddev->bitmap_info.offset) {
+		pr_warn("md/raid:%s PPL is not compatible with bitmap\n",
+			mdname(mddev));
+		return -EINVAL;
+	}
+
+	if (test_bit(MD_HAS_JOURNAL, &mddev->flags)) {
+		pr_warn("md/raid:%s PPL is not compatible with journal\n",
+			mdname(mddev));
+		return -EINVAL;
+	}
+
+	max_disks = FIELD_SIZEOF(struct ppl_log, disk_flush_bitmap) *
+		BITS_PER_BYTE;
+	if (conf->raid_disks > max_disks) {
+		pr_warn("md/raid:%s PPL doesn't support over %d disks in the array\n",
+			mdname(mddev), max_disks);
+		return -EINVAL;
+	}
+
+	ppl_conf = kzalloc(sizeof(struct ppl_conf), GFP_KERNEL);
+	if (!ppl_conf)
+		return -ENOMEM;
+
+	ppl_conf->mddev = mddev;
+
+	ppl_conf->io_kc = KMEM_CACHE(ppl_io_unit, 0);
+	if (!ppl_conf->io_kc) {
+		ret = -ENOMEM;
+		goto err;
+	}
+
+	ret = mempool_init(&ppl_conf->io_pool, conf->raid_disks, ppl_io_pool_alloc,
+			   ppl_io_pool_free, ppl_conf->io_kc);
+	if (ret)
+		goto err;
+
+	ret = bioset_init(&ppl_conf->bs, conf->raid_disks, 0, BIOSET_NEED_BVECS);
+	if (ret)
+		goto err;
+
+	ret = bioset_init(&ppl_conf->flush_bs, conf->raid_disks, 0, 0);
+	if (ret)
+		goto err;
+
+	ppl_conf->count = conf->raid_disks;
+	ppl_conf->child_logs = kcalloc(ppl_conf->count, sizeof(struct ppl_log),
+				       GFP_KERNEL);
+	if (!ppl_conf->child_logs) {
+		ret = -ENOMEM;
+		goto err;
+	}
+
+	atomic64_set(&ppl_conf->seq, 0);
+	INIT_LIST_HEAD(&ppl_conf->no_mem_stripes);
+	spin_lock_init(&ppl_conf->no_mem_stripes_lock);
+
+	if (!mddev->external) {
+		ppl_conf->signature = ~crc32c_le(~0, mddev->uuid, sizeof(mddev->uuid));
+		ppl_conf->block_size = 512;
+	} else {
+		ppl_conf->block_size = queue_logical_block_size(mddev->queue);
+	}
+
+	for (i = 0; i < ppl_conf->count; i++) {
+		struct ppl_log *log = &ppl_conf->child_logs[i];
+		struct md_rdev *rdev = conf->disks[i].rdev;
+
+		mutex_init(&log->io_mutex);
+		spin_lock_init(&log->io_list_lock);
+		INIT_LIST_HEAD(&log->io_list);
+
+		log->ppl_conf = ppl_conf;
+		log->rdev = rdev;
+
+		if (rdev) {
+			ret = ppl_validate_rdev(rdev);
+			if (ret)
+				goto err;
+
+			ppl_init_child_log(log, rdev);
+		}
+	}
+
+	/* load and possibly recover the logs from the member disks */
+	ret = ppl_load(ppl_conf);
+
+	if (ret) {
+		goto err;
+	} else if (!mddev->pers && mddev->recovery_cp == 0 &&
+		   ppl_conf->recovered_entries > 0 &&
+		   ppl_conf->mismatch_count == 0) {
+		/*
+		 * If we are starting a dirty array and the recovery succeeds
+		 * without any issues, set the array as clean.
+		 */
+		mddev->recovery_cp = MaxSector;
+		set_bit(MD_SB_CHANGE_CLEAN, &mddev->sb_flags);
+	} else if (mddev->pers && ppl_conf->mismatch_count > 0) {
+		/* no mismatch allowed when enabling PPL for a running array */
+		ret = -EINVAL;
+		goto err;
+	}
+
+	conf->log_private = ppl_conf;
+	set_bit(MD_HAS_PPL, &ppl_conf->mddev->flags);
+
+	return 0;
+err:
+	__ppl_exit_log(ppl_conf);
+	return ret;
+}
+
+int ppl_modify_log(struct r5conf *conf, struct md_rdev *rdev, bool add)
+{
+	struct ppl_conf *ppl_conf = conf->log_private;
+	struct ppl_log *log;
+	int ret = 0;
+	char b[BDEVNAME_SIZE];
+
+	if (!rdev)
+		return -EINVAL;
+
+	pr_debug("%s: disk: %d operation: %s dev: %s\n",
+		 __func__, rdev->raid_disk, add ? "add" : "remove",
+		 bdevname(rdev->bdev, b));
+
+	if (rdev->raid_disk < 0)
+		return 0;
+
+	if (rdev->raid_disk >= ppl_conf->count)
+		return -ENODEV;
+
+	log = &ppl_conf->child_logs[rdev->raid_disk];
+
+	mutex_lock(&log->io_mutex);
+	if (add) {
+		ret = ppl_validate_rdev(rdev);
+		if (!ret) {
+			log->rdev = rdev;
+			ret = ppl_write_empty_header(log);
+			ppl_init_child_log(log, rdev);
+		}
+	} else {
+		log->rdev = NULL;
+	}
+	mutex_unlock(&log->io_mutex);
+
+	return ret;
+}