Adding upstream version 4.19.249.upstream/4.19.249upstream

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

1 files changed, 1500 insertions, 0 deletions

diff --git a/drivers/md/dm-raid1.c b/drivers/md/dm-raid1.c
new file mode 100644
index 000000000..5a51151f6
--- /dev/null
+++ b/drivers/md/dm-raid1.c
@@ -0,0 +1,1500 @@
+/*
+ * Copyright (C) 2003 Sistina Software Limited.
+ * Copyright (C) 2005-2008 Red Hat, Inc. All rights reserved.
+ *
+ * This file is released under the GPL.
+ */
+
+#include "dm-bio-record.h"
+
+#include <linux/init.h>
+#include <linux/mempool.h>
+#include <linux/module.h>
+#include <linux/pagemap.h>
+#include <linux/slab.h>
+#include <linux/workqueue.h>
+#include <linux/device-mapper.h>
+#include <linux/dm-io.h>
+#include <linux/dm-dirty-log.h>
+#include <linux/dm-kcopyd.h>
+#include <linux/dm-region-hash.h>
+
+#define DM_MSG_PREFIX "raid1"
+
+#define MAX_RECOVERY 1	/* Maximum number of regions recovered in parallel. */
+
+#define MAX_NR_MIRRORS	(DM_KCOPYD_MAX_REGIONS + 1)
+
+#define DM_RAID1_HANDLE_ERRORS	0x01
+#define DM_RAID1_KEEP_LOG	0x02
+#define errors_handled(p)	((p)->features & DM_RAID1_HANDLE_ERRORS)
+#define keep_log(p)		((p)->features & DM_RAID1_KEEP_LOG)
+
+static DECLARE_WAIT_QUEUE_HEAD(_kmirrord_recovery_stopped);
+
+/*-----------------------------------------------------------------
+ * Mirror set structures.
+ *---------------------------------------------------------------*/
+enum dm_raid1_error {
+	DM_RAID1_WRITE_ERROR,
+	DM_RAID1_FLUSH_ERROR,
+	DM_RAID1_SYNC_ERROR,
+	DM_RAID1_READ_ERROR
+};
+
+struct mirror {
+	struct mirror_set *ms;
+	atomic_t error_count;
+	unsigned long error_type;
+	struct dm_dev *dev;
+	sector_t offset;
+};
+
+struct mirror_set {
+	struct dm_target *ti;
+	struct list_head list;
+
+	uint64_t features;
+
+	spinlock_t lock;	/* protects the lists */
+	struct bio_list reads;
+	struct bio_list writes;
+	struct bio_list failures;
+	struct bio_list holds;	/* bios are waiting until suspend */
+
+	struct dm_region_hash *rh;
+	struct dm_kcopyd_client *kcopyd_client;
+	struct dm_io_client *io_client;
+
+	/* recovery */
+	region_t nr_regions;
+	int in_sync;
+	int log_failure;
+	int leg_failure;
+	atomic_t suspend;
+
+	atomic_t default_mirror;	/* Default mirror */
+
+	struct workqueue_struct *kmirrord_wq;
+	struct work_struct kmirrord_work;
+	struct timer_list timer;
+	unsigned long timer_pending;
+
+	struct work_struct trigger_event;
+
+	unsigned nr_mirrors;
+	struct mirror mirror[0];
+};
+
+DECLARE_DM_KCOPYD_THROTTLE_WITH_MODULE_PARM(raid1_resync_throttle,
+		"A percentage of time allocated for raid resynchronization");
+
+static void wakeup_mirrord(void *context)
+{
+	struct mirror_set *ms = context;
+
+	queue_work(ms->kmirrord_wq, &ms->kmirrord_work);
+}
+
+static void delayed_wake_fn(struct timer_list *t)
+{
+	struct mirror_set *ms = from_timer(ms, t, timer);
+
+	clear_bit(0, &ms->timer_pending);
+	wakeup_mirrord(ms);
+}
+
+static void delayed_wake(struct mirror_set *ms)
+{
+	if (test_and_set_bit(0, &ms->timer_pending))
+		return;
+
+	ms->timer.expires = jiffies + HZ / 5;
+	add_timer(&ms->timer);
+}
+
+static void wakeup_all_recovery_waiters(void *context)
+{
+	wake_up_all(&_kmirrord_recovery_stopped);
+}
+
+static void queue_bio(struct mirror_set *ms, struct bio *bio, int rw)
+{
+	unsigned long flags;
+	int should_wake = 0;
+	struct bio_list *bl;
+
+	bl = (rw == WRITE) ? &ms->writes : &ms->reads;
+	spin_lock_irqsave(&ms->lock, flags);
+	should_wake = !(bl->head);
+	bio_list_add(bl, bio);
+	spin_unlock_irqrestore(&ms->lock, flags);
+
+	if (should_wake)
+		wakeup_mirrord(ms);
+}
+
+static void dispatch_bios(void *context, struct bio_list *bio_list)
+{
+	struct mirror_set *ms = context;
+	struct bio *bio;
+
+	while ((bio = bio_list_pop(bio_list)))
+		queue_bio(ms, bio, WRITE);
+}
+
+struct dm_raid1_bio_record {
+	struct mirror *m;
+	/* if details->bi_disk == NULL, details were not saved */
+	struct dm_bio_details details;
+	region_t write_region;
+};
+
+/*
+ * Every mirror should look like this one.
+ */
+#define DEFAULT_MIRROR 0
+
+/*
+ * This is yucky.  We squirrel the mirror struct away inside
+ * bi_next for read/write buffers.  This is safe since the bh
+ * doesn't get submitted to the lower levels of block layer.
+ */
+static struct mirror *bio_get_m(struct bio *bio)
+{
+	return (struct mirror *) bio->bi_next;
+}
+
+static void bio_set_m(struct bio *bio, struct mirror *m)
+{
+	bio->bi_next = (struct bio *) m;
+}
+
+static struct mirror *get_default_mirror(struct mirror_set *ms)
+{
+	return &ms->mirror[atomic_read(&ms->default_mirror)];
+}
+
+static void set_default_mirror(struct mirror *m)
+{
+	struct mirror_set *ms = m->ms;
+	struct mirror *m0 = &(ms->mirror[0]);
+
+	atomic_set(&ms->default_mirror, m - m0);
+}
+
+static struct mirror *get_valid_mirror(struct mirror_set *ms)
+{
+	struct mirror *m;
+
+	for (m = ms->mirror; m < ms->mirror + ms->nr_mirrors; m++)
+		if (!atomic_read(&m->error_count))
+			return m;
+
+	return NULL;
+}
+
+/* fail_mirror
+ * @m: mirror device to fail
+ * @error_type: one of the enum's, DM_RAID1_*_ERROR
+ *
+ * If errors are being handled, record the type of
+ * error encountered for this device.  If this type
+ * of error has already been recorded, we can return;
+ * otherwise, we must signal userspace by triggering
+ * an event.  Additionally, if the device is the
+ * primary device, we must choose a new primary, but
+ * only if the mirror is in-sync.
+ *
+ * This function must not block.
+ */
+static void fail_mirror(struct mirror *m, enum dm_raid1_error error_type)
+{
+	struct mirror_set *ms = m->ms;
+	struct mirror *new;
+
+	ms->leg_failure = 1;
+
+	/*
+	 * error_count is used for nothing more than a
+	 * simple way to tell if a device has encountered
+	 * errors.
+	 */
+	atomic_inc(&m->error_count);
+
+	if (test_and_set_bit(error_type, &m->error_type))
+		return;
+
+	if (!errors_handled(ms))
+		return;
+
+	if (m != get_default_mirror(ms))
+		goto out;
+
+	if (!ms->in_sync && !keep_log(ms)) {
+		/*
+		 * Better to issue requests to same failing device
+		 * than to risk returning corrupt data.
+		 */
+		DMERR("Primary mirror (%s) failed while out-of-sync: "
+		      "Reads may fail.", m->dev->name);
+		goto out;
+	}
+
+	new = get_valid_mirror(ms);
+	if (new)
+		set_default_mirror(new);
+	else
+		DMWARN("All sides of mirror have failed.");
+
+out:
+	schedule_work(&ms->trigger_event);
+}
+
+static int mirror_flush(struct dm_target *ti)
+{
+	struct mirror_set *ms = ti->private;
+	unsigned long error_bits;
+
+	unsigned int i;
+	struct dm_io_region io[MAX_NR_MIRRORS];
+	struct mirror *m;
+	struct dm_io_request io_req = {
+		.bi_op = REQ_OP_WRITE,
+		.bi_op_flags = REQ_PREFLUSH | REQ_SYNC,
+		.mem.type = DM_IO_KMEM,
+		.mem.ptr.addr = NULL,
+		.client = ms->io_client,
+	};
+
+	for (i = 0, m = ms->mirror; i < ms->nr_mirrors; i++, m++) {
+		io[i].bdev = m->dev->bdev;
+		io[i].sector = 0;
+		io[i].count = 0;
+	}
+
+	error_bits = -1;
+	dm_io(&io_req, ms->nr_mirrors, io, &error_bits);
+	if (unlikely(error_bits != 0)) {
+		for (i = 0; i < ms->nr_mirrors; i++)
+			if (test_bit(i, &error_bits))
+				fail_mirror(ms->mirror + i,
+					    DM_RAID1_FLUSH_ERROR);
+		return -EIO;
+	}
+
+	return 0;
+}
+
+/*-----------------------------------------------------------------
+ * Recovery.
+ *
+ * When a mirror is first activated we may find that some regions
+ * are in the no-sync state.  We have to recover these by
+ * recopying from the default mirror to all the others.
+ *---------------------------------------------------------------*/
+static void recovery_complete(int read_err, unsigned long write_err,
+			      void *context)
+{
+	struct dm_region *reg = context;
+	struct mirror_set *ms = dm_rh_region_context(reg);
+	int m, bit = 0;
+
+	if (read_err) {
+		/* Read error means the failure of default mirror. */
+		DMERR_LIMIT("Unable to read primary mirror during recovery");
+		fail_mirror(get_default_mirror(ms), DM_RAID1_SYNC_ERROR);
+	}
+
+	if (write_err) {
+		DMERR_LIMIT("Write error during recovery (error = 0x%lx)",
+			    write_err);
+		/*
+		 * Bits correspond to devices (excluding default mirror).
+		 * The default mirror cannot change during recovery.
+		 */
+		for (m = 0; m < ms->nr_mirrors; m++) {
+			if (&ms->mirror[m] == get_default_mirror(ms))
+				continue;
+			if (test_bit(bit, &write_err))
+				fail_mirror(ms->mirror + m,
+					    DM_RAID1_SYNC_ERROR);
+			bit++;
+		}
+	}
+
+	dm_rh_recovery_end(reg, !(read_err || write_err));
+}
+
+static void recover(struct mirror_set *ms, struct dm_region *reg)
+{
+	unsigned i;
+	struct dm_io_region from, to[DM_KCOPYD_MAX_REGIONS], *dest;
+	struct mirror *m;
+	unsigned long flags = 0;
+	region_t key = dm_rh_get_region_key(reg);
+	sector_t region_size = dm_rh_get_region_size(ms->rh);
+
+	/* fill in the source */
+	m = get_default_mirror(ms);
+	from.bdev = m->dev->bdev;
+	from.sector = m->offset + dm_rh_region_to_sector(ms->rh, key);
+	if (key == (ms->nr_regions - 1)) {
+		/*
+		 * The final region may be smaller than
+		 * region_size.
+		 */
+		from.count = ms->ti->len & (region_size - 1);
+		if (!from.count)
+			from.count = region_size;
+	} else
+		from.count = region_size;
+
+	/* fill in the destinations */
+	for (i = 0, dest = to; i < ms->nr_mirrors; i++) {
+		if (&ms->mirror[i] == get_default_mirror(ms))
+			continue;
+
+		m = ms->mirror + i;
+		dest->bdev = m->dev->bdev;
+		dest->sector = m->offset + dm_rh_region_to_sector(ms->rh, key);
+		dest->count = from.count;
+		dest++;
+	}
+
+	/* hand to kcopyd */
+	if (!errors_handled(ms))
+		set_bit(DM_KCOPYD_IGNORE_ERROR, &flags);
+
+	dm_kcopyd_copy(ms->kcopyd_client, &from, ms->nr_mirrors - 1, to,
+		       flags, recovery_complete, reg);
+}
+
+static void reset_ms_flags(struct mirror_set *ms)
+{
+	unsigned int m;
+
+	ms->leg_failure = 0;
+	for (m = 0; m < ms->nr_mirrors; m++) {
+		atomic_set(&(ms->mirror[m].error_count), 0);
+		ms->mirror[m].error_type = 0;
+	}
+}
+
+static void do_recovery(struct mirror_set *ms)
+{
+	struct dm_region *reg;
+	struct dm_dirty_log *log = dm_rh_dirty_log(ms->rh);
+
+	/*
+	 * Start quiescing some regions.
+	 */
+	dm_rh_recovery_prepare(ms->rh);
+
+	/*
+	 * Copy any already quiesced regions.
+	 */
+	while ((reg = dm_rh_recovery_start(ms->rh)))
+		recover(ms, reg);
+
+	/*
+	 * Update the in sync flag.
+	 */
+	if (!ms->in_sync &&
+	    (log->type->get_sync_count(log) == ms->nr_regions)) {
+		/* the sync is complete */
+		dm_table_event(ms->ti->table);
+		ms->in_sync = 1;
+		reset_ms_flags(ms);
+	}
+}
+
+/*-----------------------------------------------------------------
+ * Reads
+ *---------------------------------------------------------------*/
+static struct mirror *choose_mirror(struct mirror_set *ms, sector_t sector)
+{
+	struct mirror *m = get_default_mirror(ms);
+
+	do {
+		if (likely(!atomic_read(&m->error_count)))
+			return m;
+
+		if (m-- == ms->mirror)
+			m += ms->nr_mirrors;
+	} while (m != get_default_mirror(ms));
+
+	return NULL;
+}
+
+static int default_ok(struct mirror *m)
+{
+	struct mirror *default_mirror = get_default_mirror(m->ms);
+
+	return !atomic_read(&default_mirror->error_count);
+}
+
+static int mirror_available(struct mirror_set *ms, struct bio *bio)
+{
+	struct dm_dirty_log *log = dm_rh_dirty_log(ms->rh);
+	region_t region = dm_rh_bio_to_region(ms->rh, bio);
+
+	if (log->type->in_sync(log, region, 0))
+		return choose_mirror(ms,  bio->bi_iter.bi_sector) ? 1 : 0;
+
+	return 0;
+}
+
+/*
+ * remap a buffer to a particular mirror.
+ */
+static sector_t map_sector(struct mirror *m, struct bio *bio)
+{
+	if (unlikely(!bio->bi_iter.bi_size))
+		return 0;
+	return m->offset + dm_target_offset(m->ms->ti, bio->bi_iter.bi_sector);
+}
+
+static void map_bio(struct mirror *m, struct bio *bio)
+{
+	bio_set_dev(bio, m->dev->bdev);
+	bio->bi_iter.bi_sector = map_sector(m, bio);
+}
+
+static void map_region(struct dm_io_region *io, struct mirror *m,
+		       struct bio *bio)
+{
+	io->bdev = m->dev->bdev;
+	io->sector = map_sector(m, bio);
+	io->count = bio_sectors(bio);
+}
+
+static void hold_bio(struct mirror_set *ms, struct bio *bio)
+{
+	/*
+	 * Lock is required to avoid race condition during suspend
+	 * process.
+	 */
+	spin_lock_irq(&ms->lock);
+
+	if (atomic_read(&ms->suspend)) {
+		spin_unlock_irq(&ms->lock);
+
+		/*
+		 * If device is suspended, complete the bio.
+		 */
+		if (dm_noflush_suspending(ms->ti))
+			bio->bi_status = BLK_STS_DM_REQUEUE;
+		else
+			bio->bi_status = BLK_STS_IOERR;
+
+		bio_endio(bio);
+		return;
+	}
+
+	/*
+	 * Hold bio until the suspend is complete.
+	 */
+	bio_list_add(&ms->holds, bio);
+	spin_unlock_irq(&ms->lock);
+}
+
+/*-----------------------------------------------------------------
+ * Reads
+ *---------------------------------------------------------------*/
+static void read_callback(unsigned long error, void *context)
+{
+	struct bio *bio = context;
+	struct mirror *m;
+
+	m = bio_get_m(bio);
+	bio_set_m(bio, NULL);
+
+	if (likely(!error)) {
+		bio_endio(bio);
+		return;
+	}
+
+	fail_mirror(m, DM_RAID1_READ_ERROR);
+
+	if (likely(default_ok(m)) || mirror_available(m->ms, bio)) {
+		DMWARN_LIMIT("Read failure on mirror device %s.  "
+			     "Trying alternative device.",
+			     m->dev->name);
+		queue_bio(m->ms, bio, bio_data_dir(bio));
+		return;
+	}
+
+	DMERR_LIMIT("Read failure on mirror device %s.  Failing I/O.",
+		    m->dev->name);
+	bio_io_error(bio);
+}
+
+/* Asynchronous read. */
+static void read_async_bio(struct mirror *m, struct bio *bio)
+{
+	struct dm_io_region io;
+	struct dm_io_request io_req = {
+		.bi_op = REQ_OP_READ,
+		.bi_op_flags = 0,
+		.mem.type = DM_IO_BIO,
+		.mem.ptr.bio = bio,
+		.notify.fn = read_callback,
+		.notify.context = bio,
+		.client = m->ms->io_client,
+	};
+
+	map_region(&io, m, bio);
+	bio_set_m(bio, m);
+	BUG_ON(dm_io(&io_req, 1, &io, NULL));
+}
+
+static inline int region_in_sync(struct mirror_set *ms, region_t region,
+				 int may_block)
+{
+	int state = dm_rh_get_state(ms->rh, region, may_block);
+	return state == DM_RH_CLEAN || state == DM_RH_DIRTY;
+}
+
+static void do_reads(struct mirror_set *ms, struct bio_list *reads)
+{
+	region_t region;
+	struct bio *bio;
+	struct mirror *m;
+
+	while ((bio = bio_list_pop(reads))) {
+		region = dm_rh_bio_to_region(ms->rh, bio);
+		m = get_default_mirror(ms);
+
+		/*
+		 * We can only read balance if the region is in sync.
+		 */
+		if (likely(region_in_sync(ms, region, 1)))
+			m = choose_mirror(ms, bio->bi_iter.bi_sector);
+		else if (m && atomic_read(&m->error_count))
+			m = NULL;
+
+		if (likely(m))
+			read_async_bio(m, bio);
+		else
+			bio_io_error(bio);
+	}
+}
+
+/*-----------------------------------------------------------------
+ * Writes.
+ *
+ * We do different things with the write io depending on the
+ * state of the region that it's in:
+ *
+ * SYNC: 	increment pending, use kcopyd to write to *all* mirrors
+ * RECOVERING:	delay the io until recovery completes
+ * NOSYNC:	increment pending, just write to the default mirror
+ *---------------------------------------------------------------*/
+
+
+static void write_callback(unsigned long error, void *context)
+{
+	unsigned i;
+	struct bio *bio = (struct bio *) context;
+	struct mirror_set *ms;
+	int should_wake = 0;
+	unsigned long flags;
+
+	ms = bio_get_m(bio)->ms;
+	bio_set_m(bio, NULL);
+
+	/*
+	 * NOTE: We don't decrement the pending count here,
+	 * instead it is done by the targets endio function.
+	 * This way we handle both writes to SYNC and NOSYNC
+	 * regions with the same code.
+	 */
+	if (likely(!error)) {
+		bio_endio(bio);
+		return;
+	}
+
+	/*
+	 * If the bio is discard, return an error, but do not
+	 * degrade the array.
+	 */
+	if (bio_op(bio) == REQ_OP_DISCARD) {
+		bio->bi_status = BLK_STS_NOTSUPP;
+		bio_endio(bio);
+		return;
+	}
+
+	for (i = 0; i < ms->nr_mirrors; i++)
+		if (test_bit(i, &error))
+			fail_mirror(ms->mirror + i, DM_RAID1_WRITE_ERROR);
+
+	/*
+	 * Need to raise event.  Since raising
+	 * events can block, we need to do it in
+	 * the main thread.
+	 */
+	spin_lock_irqsave(&ms->lock, flags);
+	if (!ms->failures.head)
+		should_wake = 1;
+	bio_list_add(&ms->failures, bio);
+	spin_unlock_irqrestore(&ms->lock, flags);
+	if (should_wake)
+		wakeup_mirrord(ms);
+}
+
+static void do_write(struct mirror_set *ms, struct bio *bio)
+{
+	unsigned int i;
+	struct dm_io_region io[MAX_NR_MIRRORS], *dest = io;
+	struct mirror *m;
+	struct dm_io_request io_req = {
+		.bi_op = REQ_OP_WRITE,
+		.bi_op_flags = bio->bi_opf & (REQ_FUA | REQ_PREFLUSH),
+		.mem.type = DM_IO_BIO,
+		.mem.ptr.bio = bio,
+		.notify.fn = write_callback,
+		.notify.context = bio,
+		.client = ms->io_client,
+	};
+
+	if (bio_op(bio) == REQ_OP_DISCARD) {
+		io_req.bi_op = REQ_OP_DISCARD;
+		io_req.mem.type = DM_IO_KMEM;
+		io_req.mem.ptr.addr = NULL;
+	}
+
+	for (i = 0, m = ms->mirror; i < ms->nr_mirrors; i++, m++)
+		map_region(dest++, m, bio);
+
+	/*
+	 * Use default mirror because we only need it to retrieve the reference
+	 * to the mirror set in write_callback().
+	 */
+	bio_set_m(bio, get_default_mirror(ms));
+
+	BUG_ON(dm_io(&io_req, ms->nr_mirrors, io, NULL));
+}
+
+static void do_writes(struct mirror_set *ms, struct bio_list *writes)
+{
+	int state;
+	struct bio *bio;
+	struct bio_list sync, nosync, recover, *this_list = NULL;
+	struct bio_list requeue;
+	struct dm_dirty_log *log = dm_rh_dirty_log(ms->rh);
+	region_t region;
+
+	if (!writes->head)
+		return;
+
+	/*
+	 * Classify each write.
+	 */
+	bio_list_init(&sync);
+	bio_list_init(&nosync);
+	bio_list_init(&recover);
+	bio_list_init(&requeue);
+
+	while ((bio = bio_list_pop(writes))) {
+		if ((bio->bi_opf & REQ_PREFLUSH) ||
+		    (bio_op(bio) == REQ_OP_DISCARD)) {
+			bio_list_add(&sync, bio);
+			continue;
+		}
+
+		region = dm_rh_bio_to_region(ms->rh, bio);
+
+		if (log->type->is_remote_recovering &&
+		    log->type->is_remote_recovering(log, region)) {
+			bio_list_add(&requeue, bio);
+			continue;
+		}
+
+		state = dm_rh_get_state(ms->rh, region, 1);
+		switch (state) {
+		case DM_RH_CLEAN:
+		case DM_RH_DIRTY:
+			this_list = &sync;
+			break;
+
+		case DM_RH_NOSYNC:
+			this_list = &nosync;
+			break;
+
+		case DM_RH_RECOVERING:
+			this_list = &recover;
+			break;
+		}
+
+		bio_list_add(this_list, bio);
+	}
+
+	/*
+	 * Add bios that are delayed due to remote recovery
+	 * back on to the write queue
+	 */
+	if (unlikely(requeue.head)) {
+		spin_lock_irq(&ms->lock);
+		bio_list_merge(&ms->writes, &requeue);
+		spin_unlock_irq(&ms->lock);
+		delayed_wake(ms);
+	}
+
+	/*
+	 * Increment the pending counts for any regions that will
+	 * be written to (writes to recover regions are going to
+	 * be delayed).
+	 */
+	dm_rh_inc_pending(ms->rh, &sync);
+	dm_rh_inc_pending(ms->rh, &nosync);
+
+	/*
+	 * If the flush fails on a previous call and succeeds here,
+	 * we must not reset the log_failure variable.  We need
+	 * userspace interaction to do that.
+	 */
+	ms->log_failure = dm_rh_flush(ms->rh) ? 1 : ms->log_failure;
+
+	/*
+	 * Dispatch io.
+	 */
+	if (unlikely(ms->log_failure) && errors_handled(ms)) {
+		spin_lock_irq(&ms->lock);
+		bio_list_merge(&ms->failures, &sync);
+		spin_unlock_irq(&ms->lock);
+		wakeup_mirrord(ms);
+	} else
+		while ((bio = bio_list_pop(&sync)))
+			do_write(ms, bio);
+
+	while ((bio = bio_list_pop(&recover)))
+		dm_rh_delay(ms->rh, bio);
+
+	while ((bio = bio_list_pop(&nosync))) {
+		if (unlikely(ms->leg_failure) && errors_handled(ms) && !keep_log(ms)) {
+			spin_lock_irq(&ms->lock);
+			bio_list_add(&ms->failures, bio);
+			spin_unlock_irq(&ms->lock);
+			wakeup_mirrord(ms);
+		} else {
+			map_bio(get_default_mirror(ms), bio);
+			generic_make_request(bio);
+		}
+	}
+}
+
+static void do_failures(struct mirror_set *ms, struct bio_list *failures)
+{
+	struct bio *bio;
+
+	if (likely(!failures->head))
+		return;
+
+	/*
+	 * If the log has failed, unattempted writes are being
+	 * put on the holds list.  We can't issue those writes
+	 * until a log has been marked, so we must store them.
+	 *
+	 * If a 'noflush' suspend is in progress, we can requeue
+	 * the I/O's to the core.  This give userspace a chance
+	 * to reconfigure the mirror, at which point the core
+	 * will reissue the writes.  If the 'noflush' flag is
+	 * not set, we have no choice but to return errors.
+	 *
+	 * Some writes on the failures list may have been
+	 * submitted before the log failure and represent a
+	 * failure to write to one of the devices.  It is ok
+	 * for us to treat them the same and requeue them
+	 * as well.
+	 */
+	while ((bio = bio_list_pop(failures))) {
+		if (!ms->log_failure) {
+			ms->in_sync = 0;
+			dm_rh_mark_nosync(ms->rh, bio);
+		}
+
+		/*
+		 * If all the legs are dead, fail the I/O.
+		 * If the device has failed and keep_log is enabled,
+		 * fail the I/O.
+		 *
+		 * If we have been told to handle errors, and keep_log
+		 * isn't enabled, hold the bio and wait for userspace to
+		 * deal with the problem.
+		 *
+		 * Otherwise pretend that the I/O succeeded. (This would
+		 * be wrong if the failed leg returned after reboot and
+		 * got replicated back to the good legs.)
+		 */
+		if (unlikely(!get_valid_mirror(ms) || (keep_log(ms) && ms->log_failure)))
+			bio_io_error(bio);
+		else if (errors_handled(ms) && !keep_log(ms))
+			hold_bio(ms, bio);
+		else
+			bio_endio(bio);
+	}
+}
+
+static void trigger_event(struct work_struct *work)
+{
+	struct mirror_set *ms =
+		container_of(work, struct mirror_set, trigger_event);
+
+	dm_table_event(ms->ti->table);
+}
+
+/*-----------------------------------------------------------------
+ * kmirrord
+ *---------------------------------------------------------------*/
+static void do_mirror(struct work_struct *work)
+{
+	struct mirror_set *ms = container_of(work, struct mirror_set,
+					     kmirrord_work);
+	struct bio_list reads, writes, failures;
+	unsigned long flags;
+
+	spin_lock_irqsave(&ms->lock, flags);
+	reads = ms->reads;
+	writes = ms->writes;
+	failures = ms->failures;
+	bio_list_init(&ms->reads);
+	bio_list_init(&ms->writes);
+	bio_list_init(&ms->failures);
+	spin_unlock_irqrestore(&ms->lock, flags);
+
+	dm_rh_update_states(ms->rh, errors_handled(ms));
+	do_recovery(ms);
+	do_reads(ms, &reads);
+	do_writes(ms, &writes);
+	do_failures(ms, &failures);
+}
+
+/*-----------------------------------------------------------------
+ * Target functions
+ *---------------------------------------------------------------*/
+static struct mirror_set *alloc_context(unsigned int nr_mirrors,
+					uint32_t region_size,
+					struct dm_target *ti,
+					struct dm_dirty_log *dl)
+{
+	size_t len;
+	struct mirror_set *ms = NULL;
+
+	len = sizeof(*ms) + (sizeof(ms->mirror[0]) * nr_mirrors);
+
+	ms = kzalloc(len, GFP_KERNEL);
+	if (!ms) {
+		ti->error = "Cannot allocate mirror context";
+		return NULL;
+	}
+
+	spin_lock_init(&ms->lock);
+	bio_list_init(&ms->reads);
+	bio_list_init(&ms->writes);
+	bio_list_init(&ms->failures);
+	bio_list_init(&ms->holds);
+
+	ms->ti = ti;
+	ms->nr_mirrors = nr_mirrors;
+	ms->nr_regions = dm_sector_div_up(ti->len, region_size);
+	ms->in_sync = 0;
+	ms->log_failure = 0;
+	ms->leg_failure = 0;
+	atomic_set(&ms->suspend, 0);
+	atomic_set(&ms->default_mirror, DEFAULT_MIRROR);
+
+	ms->io_client = dm_io_client_create();
+	if (IS_ERR(ms->io_client)) {
+		ti->error = "Error creating dm_io client";
+		kfree(ms);
+ 		return NULL;
+	}
+
+	ms->rh = dm_region_hash_create(ms, dispatch_bios, wakeup_mirrord,
+				       wakeup_all_recovery_waiters,
+				       ms->ti->begin, MAX_RECOVERY,
+				       dl, region_size, ms->nr_regions);
+	if (IS_ERR(ms->rh)) {
+		ti->error = "Error creating dirty region hash";
+		dm_io_client_destroy(ms->io_client);
+		kfree(ms);
+		return NULL;
+	}
+
+	return ms;
+}
+
+static void free_context(struct mirror_set *ms, struct dm_target *ti,
+			 unsigned int m)
+{
+	while (m--)
+		dm_put_device(ti, ms->mirror[m].dev);
+
+	dm_io_client_destroy(ms->io_client);
+	dm_region_hash_destroy(ms->rh);
+	kfree(ms);
+}
+
+static int get_mirror(struct mirror_set *ms, struct dm_target *ti,
+		      unsigned int mirror, char **argv)
+{
+	unsigned long long offset;
+	char dummy;
+	int ret;
+
+	if (sscanf(argv[1], "%llu%c", &offset, &dummy) != 1 ||
+	    offset != (sector_t)offset) {
+		ti->error = "Invalid offset";
+		return -EINVAL;
+	}
+
+	ret = dm_get_device(ti, argv[0], dm_table_get_mode(ti->table),
+			    &ms->mirror[mirror].dev);
+	if (ret) {
+		ti->error = "Device lookup failure";
+		return ret;
+	}
+
+	ms->mirror[mirror].ms = ms;
+	atomic_set(&(ms->mirror[mirror].error_count), 0);
+	ms->mirror[mirror].error_type = 0;
+	ms->mirror[mirror].offset = offset;
+
+	return 0;
+}
+
+/*
+ * Create dirty log: log_type #log_params <log_params>
+ */
+static struct dm_dirty_log *create_dirty_log(struct dm_target *ti,
+					     unsigned argc, char **argv,
+					     unsigned *args_used)
+{
+	unsigned param_count;
+	struct dm_dirty_log *dl;
+	char dummy;
+
+	if (argc < 2) {
+		ti->error = "Insufficient mirror log arguments";
+		return NULL;
+	}
+
+	if (sscanf(argv[1], "%u%c", &param_count, &dummy) != 1) {
+		ti->error = "Invalid mirror log argument count";
+		return NULL;
+	}
+
+	*args_used = 2 + param_count;
+
+	if (argc < *args_used) {
+		ti->error = "Insufficient mirror log arguments";
+		return NULL;
+	}
+
+	dl = dm_dirty_log_create(argv[0], ti, mirror_flush, param_count,
+				 argv + 2);
+	if (!dl) {
+		ti->error = "Error creating mirror dirty log";
+		return NULL;
+	}
+
+	return dl;
+}
+
+static int parse_features(struct mirror_set *ms, unsigned argc, char **argv,
+			  unsigned *args_used)
+{
+	unsigned num_features;
+	struct dm_target *ti = ms->ti;
+	char dummy;
+	int i;
+
+	*args_used = 0;
+
+	if (!argc)
+		return 0;
+
+	if (sscanf(argv[0], "%u%c", &num_features, &dummy) != 1) {
+		ti->error = "Invalid number of features";
+		return -EINVAL;
+	}
+
+	argc--;
+	argv++;
+	(*args_used)++;
+
+	if (num_features > argc) {
+		ti->error = "Not enough arguments to support feature count";
+		return -EINVAL;
+	}
+
+	for (i = 0; i < num_features; i++) {
+		if (!strcmp("handle_errors", argv[0]))
+			ms->features |= DM_RAID1_HANDLE_ERRORS;
+		else if (!strcmp("keep_log", argv[0]))
+			ms->features |= DM_RAID1_KEEP_LOG;
+		else {
+			ti->error = "Unrecognised feature requested";
+			return -EINVAL;
+		}
+
+		argc--;
+		argv++;
+		(*args_used)++;
+	}
+	if (!errors_handled(ms) && keep_log(ms)) {
+		ti->error = "keep_log feature requires the handle_errors feature";
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+/*
+ * Construct a mirror mapping:
+ *
+ * log_type #log_params <log_params>
+ * #mirrors [mirror_path offset]{2,}
+ * [#features <features>]
+ *
+ * log_type is "core" or "disk"
+ * #log_params is between 1 and 3
+ *
+ * If present, supported features are "handle_errors" and "keep_log".
+ */
+static int mirror_ctr(struct dm_target *ti, unsigned int argc, char **argv)
+{
+	int r;
+	unsigned int nr_mirrors, m, args_used;
+	struct mirror_set *ms;
+	struct dm_dirty_log *dl;
+	char dummy;
+
+	dl = create_dirty_log(ti, argc, argv, &args_used);
+	if (!dl)
+		return -EINVAL;
+
+	argv += args_used;
+	argc -= args_used;
+
+	if (!argc || sscanf(argv[0], "%u%c", &nr_mirrors, &dummy) != 1 ||
+	    nr_mirrors < 2 || nr_mirrors > MAX_NR_MIRRORS) {
+		ti->error = "Invalid number of mirrors";
+		dm_dirty_log_destroy(dl);
+		return -EINVAL;
+	}
+
+	argv++, argc--;
+
+	if (argc < nr_mirrors * 2) {
+		ti->error = "Too few mirror arguments";
+		dm_dirty_log_destroy(dl);
+		return -EINVAL;
+	}
+
+	ms = alloc_context(nr_mirrors, dl->type->get_region_size(dl), ti, dl);
+	if (!ms) {
+		dm_dirty_log_destroy(dl);
+		return -ENOMEM;
+	}
+
+	/* Get the mirror parameter sets */
+	for (m = 0; m < nr_mirrors; m++) {
+		r = get_mirror(ms, ti, m, argv);
+		if (r) {
+			free_context(ms, ti, m);
+			return r;
+		}
+		argv += 2;
+		argc -= 2;
+	}
+
+	ti->private = ms;
+
+	r = dm_set_target_max_io_len(ti, dm_rh_get_region_size(ms->rh));
+	if (r)
+		goto err_free_context;
+
+	ti->num_flush_bios = 1;
+	ti->num_discard_bios = 1;
+	ti->per_io_data_size = sizeof(struct dm_raid1_bio_record);
+
+	ms->kmirrord_wq = alloc_workqueue("kmirrord", WQ_MEM_RECLAIM, 0);
+	if (!ms->kmirrord_wq) {
+		DMERR("couldn't start kmirrord");
+		r = -ENOMEM;
+		goto err_free_context;
+	}
+	INIT_WORK(&ms->kmirrord_work, do_mirror);
+	timer_setup(&ms->timer, delayed_wake_fn, 0);
+	ms->timer_pending = 0;
+	INIT_WORK(&ms->trigger_event, trigger_event);
+
+	r = parse_features(ms, argc, argv, &args_used);
+	if (r)
+		goto err_destroy_wq;
+
+	argv += args_used;
+	argc -= args_used;
+
+	/*
+	 * Any read-balancing addition depends on the
+	 * DM_RAID1_HANDLE_ERRORS flag being present.
+	 * This is because the decision to balance depends
+	 * on the sync state of a region.  If the above
+	 * flag is not present, we ignore errors; and
+	 * the sync state may be inaccurate.
+	 */
+
+	if (argc) {
+		ti->error = "Too many mirror arguments";
+		r = -EINVAL;
+		goto err_destroy_wq;
+	}
+
+	ms->kcopyd_client = dm_kcopyd_client_create(&dm_kcopyd_throttle);
+	if (IS_ERR(ms->kcopyd_client)) {
+		r = PTR_ERR(ms->kcopyd_client);
+		goto err_destroy_wq;
+	}
+
+	wakeup_mirrord(ms);
+	return 0;
+
+err_destroy_wq:
+	destroy_workqueue(ms->kmirrord_wq);
+err_free_context:
+	free_context(ms, ti, ms->nr_mirrors);
+	return r;
+}
+
+static void mirror_dtr(struct dm_target *ti)
+{
+	struct mirror_set *ms = (struct mirror_set *) ti->private;
+
+	del_timer_sync(&ms->timer);
+	flush_workqueue(ms->kmirrord_wq);
+	flush_work(&ms->trigger_event);
+	dm_kcopyd_client_destroy(ms->kcopyd_client);
+	destroy_workqueue(ms->kmirrord_wq);
+	free_context(ms, ti, ms->nr_mirrors);
+}
+
+/*
+ * Mirror mapping function
+ */
+static int mirror_map(struct dm_target *ti, struct bio *bio)
+{
+	int r, rw = bio_data_dir(bio);
+	struct mirror *m;
+	struct mirror_set *ms = ti->private;
+	struct dm_dirty_log *log = dm_rh_dirty_log(ms->rh);
+	struct dm_raid1_bio_record *bio_record =
+	  dm_per_bio_data(bio, sizeof(struct dm_raid1_bio_record));
+
+	bio_record->details.bi_disk = NULL;
+
+	if (rw == WRITE) {
+		/* Save region for mirror_end_io() handler */
+		bio_record->write_region = dm_rh_bio_to_region(ms->rh, bio);
+		queue_bio(ms, bio, rw);
+		return DM_MAPIO_SUBMITTED;
+	}
+
+	r = log->type->in_sync(log, dm_rh_bio_to_region(ms->rh, bio), 0);
+	if (r < 0 && r != -EWOULDBLOCK)
+		return DM_MAPIO_KILL;
+
+	/*
+	 * If region is not in-sync queue the bio.
+	 */
+	if (!r || (r == -EWOULDBLOCK)) {
+		if (bio->bi_opf & REQ_RAHEAD)
+			return DM_MAPIO_KILL;
+
+		queue_bio(ms, bio, rw);
+		return DM_MAPIO_SUBMITTED;
+	}
+
+	/*
+	 * The region is in-sync and we can perform reads directly.
+	 * Store enough information so we can retry if it fails.
+	 */
+	m = choose_mirror(ms, bio->bi_iter.bi_sector);
+	if (unlikely(!m))
+		return DM_MAPIO_KILL;
+
+	dm_bio_record(&bio_record->details, bio);
+	bio_record->m = m;
+
+	map_bio(m, bio);
+
+	return DM_MAPIO_REMAPPED;
+}
+
+static int mirror_end_io(struct dm_target *ti, struct bio *bio,
+		blk_status_t *error)
+{
+	int rw = bio_data_dir(bio);
+	struct mirror_set *ms = (struct mirror_set *) ti->private;
+	struct mirror *m = NULL;
+	struct dm_bio_details *bd = NULL;
+	struct dm_raid1_bio_record *bio_record =
+	  dm_per_bio_data(bio, sizeof(struct dm_raid1_bio_record));
+
+	/*
+	 * We need to dec pending if this was a write.
+	 */
+	if (rw == WRITE) {
+		if (!(bio->bi_opf & REQ_PREFLUSH) &&
+		    bio_op(bio) != REQ_OP_DISCARD)
+			dm_rh_dec(ms->rh, bio_record->write_region);
+		return DM_ENDIO_DONE;
+	}
+
+	if (*error == BLK_STS_NOTSUPP)
+		goto out;
+
+	if (bio->bi_opf & REQ_RAHEAD)
+		goto out;
+
+	if (unlikely(*error)) {
+		if (!bio_record->details.bi_disk) {
+			/*
+			 * There wasn't enough memory to record necessary
+			 * information for a retry or there was no other
+			 * mirror in-sync.
+			 */
+			DMERR_LIMIT("Mirror read failed.");
+			return DM_ENDIO_DONE;
+		}
+
+		m = bio_record->m;
+
+		DMERR("Mirror read failed from %s. Trying alternative device.",
+		      m->dev->name);
+
+		fail_mirror(m, DM_RAID1_READ_ERROR);
+
+		/*
+		 * A failed read is requeued for another attempt using an intact
+		 * mirror.
+		 */
+		if (default_ok(m) || mirror_available(ms, bio)) {
+			bd = &bio_record->details;
+
+			dm_bio_restore(bd, bio);
+			bio_record->details.bi_disk = NULL;
+			bio->bi_status = 0;
+
+			queue_bio(ms, bio, rw);
+			return DM_ENDIO_INCOMPLETE;
+		}
+		DMERR("All replicated volumes dead, failing I/O");
+	}
+
+out:
+	bio_record->details.bi_disk = NULL;
+
+	return DM_ENDIO_DONE;
+}
+
+static void mirror_presuspend(struct dm_target *ti)
+{
+	struct mirror_set *ms = (struct mirror_set *) ti->private;
+	struct dm_dirty_log *log = dm_rh_dirty_log(ms->rh);
+
+	struct bio_list holds;
+	struct bio *bio;
+
+	atomic_set(&ms->suspend, 1);
+
+	/*
+	 * Process bios in the hold list to start recovery waiting
+	 * for bios in the hold list. After the process, no bio has
+	 * a chance to be added in the hold list because ms->suspend
+	 * is set.
+	 */
+	spin_lock_irq(&ms->lock);
+	holds = ms->holds;
+	bio_list_init(&ms->holds);
+	spin_unlock_irq(&ms->lock);
+
+	while ((bio = bio_list_pop(&holds)))
+		hold_bio(ms, bio);
+
+	/*
+	 * We must finish up all the work that we've
+	 * generated (i.e. recovery work).
+	 */
+	dm_rh_stop_recovery(ms->rh);
+
+	wait_event(_kmirrord_recovery_stopped,
+		   !dm_rh_recovery_in_flight(ms->rh));
+
+	if (log->type->presuspend && log->type->presuspend(log))
+		/* FIXME: need better error handling */
+		DMWARN("log presuspend failed");
+
+	/*
+	 * Now that recovery is complete/stopped and the
+	 * delayed bios are queued, we need to wait for
+	 * the worker thread to complete.  This way,
+	 * we know that all of our I/O has been pushed.
+	 */
+	flush_workqueue(ms->kmirrord_wq);
+}
+
+static void mirror_postsuspend(struct dm_target *ti)
+{
+	struct mirror_set *ms = ti->private;
+	struct dm_dirty_log *log = dm_rh_dirty_log(ms->rh);
+
+	if (log->type->postsuspend && log->type->postsuspend(log))
+		/* FIXME: need better error handling */
+		DMWARN("log postsuspend failed");
+}
+
+static void mirror_resume(struct dm_target *ti)
+{
+	struct mirror_set *ms = ti->private;
+	struct dm_dirty_log *log = dm_rh_dirty_log(ms->rh);
+
+	atomic_set(&ms->suspend, 0);
+	if (log->type->resume && log->type->resume(log))
+		/* FIXME: need better error handling */
+		DMWARN("log resume failed");
+	dm_rh_start_recovery(ms->rh);
+}
+
+/*
+ * device_status_char
+ * @m: mirror device/leg we want the status of
+ *
+ * We return one character representing the most severe error
+ * we have encountered.
+ *    A => Alive - No failures
+ *    D => Dead - A write failure occurred leaving mirror out-of-sync
+ *    S => Sync - A sychronization failure occurred, mirror out-of-sync
+ *    R => Read - A read failure occurred, mirror data unaffected
+ *
+ * Returns: <char>
+ */
+static char device_status_char(struct mirror *m)
+{
+	if (!atomic_read(&(m->error_count)))
+		return 'A';
+
+	return (test_bit(DM_RAID1_FLUSH_ERROR, &(m->error_type))) ? 'F' :
+		(test_bit(DM_RAID1_WRITE_ERROR, &(m->error_type))) ? 'D' :
+		(test_bit(DM_RAID1_SYNC_ERROR, &(m->error_type))) ? 'S' :
+		(test_bit(DM_RAID1_READ_ERROR, &(m->error_type))) ? 'R' : 'U';
+}
+
+
+static void mirror_status(struct dm_target *ti, status_type_t type,
+			  unsigned status_flags, char *result, unsigned maxlen)
+{
+	unsigned int m, sz = 0;
+	int num_feature_args = 0;
+	struct mirror_set *ms = (struct mirror_set *) ti->private;
+	struct dm_dirty_log *log = dm_rh_dirty_log(ms->rh);
+	char buffer[MAX_NR_MIRRORS + 1];
+
+	switch (type) {
+	case STATUSTYPE_INFO:
+		DMEMIT("%d ", ms->nr_mirrors);
+		for (m = 0; m < ms->nr_mirrors; m++) {
+			DMEMIT("%s ", ms->mirror[m].dev->name);
+			buffer[m] = device_status_char(&(ms->mirror[m]));
+		}
+		buffer[m] = '\0';
+
+		DMEMIT("%llu/%llu 1 %s ",
+		      (unsigned long long)log->type->get_sync_count(log),
+		      (unsigned long long)ms->nr_regions, buffer);
+
+		sz += log->type->status(log, type, result+sz, maxlen-sz);
+
+		break;
+
+	case STATUSTYPE_TABLE:
+		sz = log->type->status(log, type, result, maxlen);
+
+		DMEMIT("%d", ms->nr_mirrors);
+		for (m = 0; m < ms->nr_mirrors; m++)
+			DMEMIT(" %s %llu", ms->mirror[m].dev->name,
+			       (unsigned long long)ms->mirror[m].offset);
+
+		num_feature_args += !!errors_handled(ms);
+		num_feature_args += !!keep_log(ms);
+		if (num_feature_args) {
+			DMEMIT(" %d", num_feature_args);
+			if (errors_handled(ms))
+				DMEMIT(" handle_errors");
+			if (keep_log(ms))
+				DMEMIT(" keep_log");
+		}
+
+		break;
+	}
+}
+
+static int mirror_iterate_devices(struct dm_target *ti,
+				  iterate_devices_callout_fn fn, void *data)
+{
+	struct mirror_set *ms = ti->private;
+	int ret = 0;
+	unsigned i;
+
+	for (i = 0; !ret && i < ms->nr_mirrors; i++)
+		ret = fn(ti, ms->mirror[i].dev,
+			 ms->mirror[i].offset, ti->len, data);
+
+	return ret;
+}
+
+static struct target_type mirror_target = {
+	.name	 = "mirror",
+	.version = {1, 14, 0},
+	.module	 = THIS_MODULE,
+	.ctr	 = mirror_ctr,
+	.dtr	 = mirror_dtr,
+	.map	 = mirror_map,
+	.end_io	 = mirror_end_io,
+	.presuspend = mirror_presuspend,
+	.postsuspend = mirror_postsuspend,
+	.resume	 = mirror_resume,
+	.status	 = mirror_status,
+	.iterate_devices = mirror_iterate_devices,
+};
+
+static int __init dm_mirror_init(void)
+{
+	int r;
+
+	r = dm_register_target(&mirror_target);
+	if (r < 0) {
+		DMERR("Failed to register mirror target");
+		goto bad_target;
+	}
+
+	return 0;
+
+bad_target:
+	return r;
+}
+
+static void __exit dm_mirror_exit(void)
+{
+	dm_unregister_target(&mirror_target);
+}
+
+/* Module hooks */
+module_init(dm_mirror_init);
+module_exit(dm_mirror_exit);
+
+MODULE_DESCRIPTION(DM_NAME " mirror target");
+MODULE_AUTHOR("Joe Thornber");
+MODULE_LICENSE("GPL");