diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
new file mode 100644
index 0000000..f24a9e1
--- /dev/null
+++ b/drivers/md/raid1.c
@@ -0,0 +1,3215 @@
+/*
+ * raid1.c : Multiple Devices driver for Linux
+ *
+ * Copyright (C) 1999, 2000, 2001 Ingo Molnar, Red Hat
+ *
+ * Copyright (C) 1996, 1997, 1998 Ingo Molnar, Miguel de Icaza, Gadi Oxman
+ *
+ * RAID-1 management functions.
+ *
+ * Better read-balancing code written by Mika Kuoppala <miku@iki.fi>, 2000
+ *
+ * Fixes to reconstruction by Jakob Østergaard" <jakob@ostenfeld.dk>
+ * Various fixes by Neil Brown <neilb@cse.unsw.edu.au>
+ *
+ * Changes by Peter T. Breuer <ptb@it.uc3m.es> 31/1/2003 to support
+ * bitmapped intelligence in resync:
+ *
+ *      - bitmap marked during normal i/o
+ *      - bitmap used to skip nondirty blocks during sync
+ *
+ * Additions to bitmap code, (C) 2003-2004 Paul Clements, SteelEye Technology:
+ * - persistent bitmap code
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2, or (at your option)
+ * any later version.
+ *
+ * You should have received a copy of the GNU General Public License
+ * (for example /usr/src/linux/COPYING); if not, write to the Free
+ * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <linux/slab.h>
+#include <linux/delay.h>
+#include <linux/blkdev.h>
+#include <linux/module.h>
+#include <linux/seq_file.h>
+#include <linux/ratelimit.h>
+#include "md.h"
+#include "raid1.h"
+#include "bitmap.h"
+
+/*
+ * Number of guaranteed r1bios in case of extreme VM load:
+ */
+#define	NR_RAID1_BIOS 256
+
+/* when we get a read error on a read-only array, we redirect to another
+ * device without failing the first device, or trying to over-write to
+ * correct the read error.  To keep track of bad blocks on a per-bio
+ * level, we store IO_BLOCKED in the appropriate 'bios' pointer
+ */
+#define IO_BLOCKED ((struct bio *)1)
+/* When we successfully write to a known bad-block, we need to remove the
+ * bad-block marking which must be done from process context.  So we record
+ * the success by setting devs[n].bio to IO_MADE_GOOD
+ */
+#define IO_MADE_GOOD ((struct bio *)2)
+
+#define BIO_SPECIAL(bio) ((unsigned long)bio <= 2)
+
+/* When there are this many requests queue to be written by
+ * the raid1 thread, we become 'congested' to provide back-pressure
+ * for writeback.
+ */
+static int max_queued_requests = 1024;
+
+static void allow_barrier(struct r1conf *conf, sector_t start_next_window,
+			  sector_t bi_sector);
+static void lower_barrier(struct r1conf *conf);
+
+static void * r1bio_pool_alloc(gfp_t gfp_flags, void *data)
+{
+	struct pool_info *pi = data;
+	int size = offsetof(struct r1bio, bios[pi->raid_disks]);
+
+	/* allocate a r1bio with room for raid_disks entries in the bios array */
+	return kzalloc(size, gfp_flags);
+}
+
+static void r1bio_pool_free(void *r1_bio, void *data)
+{
+	kfree(r1_bio);
+}
+
+#define RESYNC_BLOCK_SIZE (64*1024)
+#define RESYNC_DEPTH 32
+#define RESYNC_SECTORS (RESYNC_BLOCK_SIZE >> 9)
+#define RESYNC_PAGES ((RESYNC_BLOCK_SIZE + PAGE_SIZE-1) / PAGE_SIZE)
+#define RESYNC_WINDOW (RESYNC_BLOCK_SIZE * RESYNC_DEPTH)
+#define RESYNC_WINDOW_SECTORS (RESYNC_WINDOW >> 9)
+#define CLUSTER_RESYNC_WINDOW (16 * RESYNC_WINDOW)
+#define CLUSTER_RESYNC_WINDOW_SECTORS (CLUSTER_RESYNC_WINDOW >> 9)
+#define NEXT_NORMALIO_DISTANCE (3 * RESYNC_WINDOW_SECTORS)
+
+static void * r1buf_pool_alloc(gfp_t gfp_flags, void *data)
+{
+	struct pool_info *pi = data;
+	struct r1bio *r1_bio;
+	struct bio *bio;
+	int need_pages;
+	int i, j;
+
+	r1_bio = r1bio_pool_alloc(gfp_flags, pi);
+	if (!r1_bio)
+		return NULL;
+
+	/*
+	 * Allocate bios : 1 for reading, n-1 for writing
+	 */
+	for (j = pi->raid_disks ; j-- ; ) {
+		bio = bio_kmalloc(gfp_flags, RESYNC_PAGES);
+		if (!bio)
+			goto out_free_bio;
+		r1_bio->bios[j] = bio;
+	}
+	/*
+	 * Allocate RESYNC_PAGES data pages and attach them to
+	 * the first bio.
+	 * If this is a user-requested check/repair, allocate
+	 * RESYNC_PAGES for each bio.
+	 */
+	if (test_bit(MD_RECOVERY_REQUESTED, &pi->mddev->recovery))
+		need_pages = pi->raid_disks;
+	else
+		need_pages = 1;
+	for (j = 0; j < need_pages; j++) {
+		bio = r1_bio->bios[j];
+		bio->bi_vcnt = RESYNC_PAGES;
+
+		if (bio_alloc_pages(bio, gfp_flags))
+			goto out_free_pages;
+	}
+	/* If not user-requests, copy the page pointers to all bios */
+	if (!test_bit(MD_RECOVERY_REQUESTED, &pi->mddev->recovery)) {
+		for (i=0; i<RESYNC_PAGES ; i++)
+			for (j=1; j<pi->raid_disks; j++)
+				r1_bio->bios[j]->bi_io_vec[i].bv_page =
+					r1_bio->bios[0]->bi_io_vec[i].bv_page;
+	}
+
+	r1_bio->master_bio = NULL;
+
+	return r1_bio;
+
+out_free_pages:
+	while (--j >= 0) {
+		struct bio_vec *bv;
+
+		bio_for_each_segment_all(bv, r1_bio->bios[j], i)
+			__free_page(bv->bv_page);
+	}
+
+out_free_bio:
+	while (++j < pi->raid_disks)
+		bio_put(r1_bio->bios[j]);
+	r1bio_pool_free(r1_bio, data);
+	return NULL;
+}
+
+static void r1buf_pool_free(void *__r1_bio, void *data)
+{
+	struct pool_info *pi = data;
+	int i,j;
+	struct r1bio *r1bio = __r1_bio;
+
+	for (i = 0; i < RESYNC_PAGES; i++)
+		for (j = pi->raid_disks; j-- ;) {
+			if (j == 0 ||
+			    r1bio->bios[j]->bi_io_vec[i].bv_page !=
+			    r1bio->bios[0]->bi_io_vec[i].bv_page)
+				safe_put_page(r1bio->bios[j]->bi_io_vec[i].bv_page);
+		}
+	for (i=0 ; i < pi->raid_disks; i++)
+		bio_put(r1bio->bios[i]);
+
+	r1bio_pool_free(r1bio, data);
+}
+
+static void put_all_bios(struct r1conf *conf, struct r1bio *r1_bio)
+{
+	int i;
+
+	for (i = 0; i < conf->raid_disks * 2; i++) {
+		struct bio **bio = r1_bio->bios + i;
+		if (!BIO_SPECIAL(*bio))
+			bio_put(*bio);
+		*bio = NULL;
+	}
+}
+
+static void free_r1bio(struct r1bio *r1_bio)
+{
+	struct r1conf *conf = r1_bio->mddev->private;
+
+	put_all_bios(conf, r1_bio);
+	mempool_free(r1_bio, conf->r1bio_pool);
+}
+
+static void put_buf(struct r1bio *r1_bio)
+{
+	struct r1conf *conf = r1_bio->mddev->private;
+	int i;
+
+	for (i = 0; i < conf->raid_disks * 2; i++) {
+		struct bio *bio = r1_bio->bios[i];
+		if (bio->bi_end_io)
+			rdev_dec_pending(conf->mirrors[i].rdev, r1_bio->mddev);
+	}
+
+	mempool_free(r1_bio, conf->r1buf_pool);
+
+	lower_barrier(conf);
+}
+
+static void reschedule_retry(struct r1bio *r1_bio)
+{
+	unsigned long flags;
+	struct mddev *mddev = r1_bio->mddev;
+	struct r1conf *conf = mddev->private;
+
+	spin_lock_irqsave(&conf->device_lock, flags);
+	list_add(&r1_bio->retry_list, &conf->retry_list);
+	conf->nr_queued ++;
+	spin_unlock_irqrestore(&conf->device_lock, flags);
+
+	wake_up(&conf->wait_barrier);
+	md_wakeup_thread(mddev->thread);
+}
+
+/*
+ * raid_end_bio_io() is called when we have finished servicing a mirrored
+ * operation and are ready to return a success/failure code to the buffer
+ * cache layer.
+ */
+static void call_bio_endio(struct r1bio *r1_bio)
+{
+	struct bio *bio = r1_bio->master_bio;
+	int done;
+	struct r1conf *conf = r1_bio->mddev->private;
+	sector_t start_next_window = r1_bio->start_next_window;
+	sector_t bi_sector = bio->bi_iter.bi_sector;
+
+	if (bio->bi_phys_segments) {
+		unsigned long flags;
+		spin_lock_irqsave(&conf->device_lock, flags);
+		bio->bi_phys_segments--;
+		done = (bio->bi_phys_segments == 0);
+		spin_unlock_irqrestore(&conf->device_lock, flags);
+		/*
+		 * make_request() might be waiting for
+		 * bi_phys_segments to decrease
+		 */
+		wake_up(&conf->wait_barrier);
+	} else
+		done = 1;
+
+	if (!test_bit(R1BIO_Uptodate, &r1_bio->state))
+		bio->bi_error = -EIO;
+
+	if (done) {
+		bio_endio(bio);
+		/*
+		 * Wake up any possible resync thread that waits for the device
+		 * to go idle.
+		 */
+		allow_barrier(conf, start_next_window, bi_sector);
+	}
+}
+
+static void raid_end_bio_io(struct r1bio *r1_bio)
+{
+	struct bio *bio = r1_bio->master_bio;
+
+	/* if nobody has done the final endio yet, do it now */
+	if (!test_and_set_bit(R1BIO_Returned, &r1_bio->state)) {
+		pr_debug("raid1: sync end %s on sectors %llu-%llu\n",
+			 (bio_data_dir(bio) == WRITE) ? "write" : "read",
+			 (unsigned long long) bio->bi_iter.bi_sector,
+			 (unsigned long long) bio_end_sector(bio) - 1);
+
+		call_bio_endio(r1_bio);
+	}
+	free_r1bio(r1_bio);
+}
+
+/*
+ * Update disk head position estimator based on IRQ completion info.
+ */
+static inline void update_head_pos(int disk, struct r1bio *r1_bio)
+{
+	struct r1conf *conf = r1_bio->mddev->private;
+
+	conf->mirrors[disk].head_position =
+		r1_bio->sector + (r1_bio->sectors);
+}
+
+/*
+ * Find the disk number which triggered given bio
+ */
+static int find_bio_disk(struct r1bio *r1_bio, struct bio *bio)
+{
+	int mirror;
+	struct r1conf *conf = r1_bio->mddev->private;
+	int raid_disks = conf->raid_disks;
+
+	for (mirror = 0; mirror < raid_disks * 2; mirror++)
+		if (r1_bio->bios[mirror] == bio)
+			break;
+
+	BUG_ON(mirror == raid_disks * 2);
+	update_head_pos(mirror, r1_bio);
+
+	return mirror;
+}
+
+static void raid1_end_read_request(struct bio *bio)
+{
+	int uptodate = !bio->bi_error;
+	struct r1bio *r1_bio = bio->bi_private;
+	int mirror;
+	struct r1conf *conf = r1_bio->mddev->private;
+
+	mirror = r1_bio->read_disk;
+	/*
+	 * this branch is our 'one mirror IO has finished' event handler:
+	 */
+	update_head_pos(mirror, r1_bio);
+
+	if (uptodate)
+		set_bit(R1BIO_Uptodate, &r1_bio->state);
+	else {
+		/* If all other devices have failed, we want to return
+		 * the error upwards rather than fail the last device.
+		 * Here we redefine "uptodate" to mean "Don't want to retry"
+		 */
+		unsigned long flags;
+		spin_lock_irqsave(&conf->device_lock, flags);
+		if (r1_bio->mddev->degraded == conf->raid_disks ||
+		    (r1_bio->mddev->degraded == conf->raid_disks-1 &&
+		     test_bit(In_sync, &conf->mirrors[mirror].rdev->flags)))
+			uptodate = 1;
+		spin_unlock_irqrestore(&conf->device_lock, flags);
+	}
+
+	if (uptodate) {
+		raid_end_bio_io(r1_bio);
+		rdev_dec_pending(conf->mirrors[mirror].rdev, conf->mddev);
+	} else {
+		/*
+		 * oops, read error:
+		 */
+		char b[BDEVNAME_SIZE];
+		printk_ratelimited(
+			KERN_ERR "md/raid1:%s: %s: "
+			"rescheduling sector %llu\n",
+			mdname(conf->mddev),
+			bdevname(conf->mirrors[mirror].rdev->bdev,
+				 b),
+			(unsigned long long)r1_bio->sector);
+		set_bit(R1BIO_ReadError, &r1_bio->state);
+		reschedule_retry(r1_bio);
+		/* don't drop the reference on read_disk yet */
+	}
+}
+
+static void close_write(struct r1bio *r1_bio)
+{
+	/* it really is the end of this request */
+	if (test_bit(R1BIO_BehindIO, &r1_bio->state)) {
+		/* free extra copy of the data pages */
+		int i = r1_bio->behind_page_count;
+		while (i--)
+			safe_put_page(r1_bio->behind_bvecs[i].bv_page);
+		kfree(r1_bio->behind_bvecs);
+		r1_bio->behind_bvecs = NULL;
+	}
+	/* clear the bitmap if all writes complete successfully */
+	bitmap_endwrite(r1_bio->mddev->bitmap, r1_bio->sector,
+			r1_bio->sectors,
+			!test_bit(R1BIO_Degraded, &r1_bio->state),
+			test_bit(R1BIO_BehindIO, &r1_bio->state));
+	md_write_end(r1_bio->mddev);
+}
+
+static void r1_bio_write_done(struct r1bio *r1_bio)
+{
+	if (!atomic_dec_and_test(&r1_bio->remaining))
+		return;
+
+	if (test_bit(R1BIO_WriteError, &r1_bio->state))
+		reschedule_retry(r1_bio);
+	else {
+		close_write(r1_bio);
+		if (test_bit(R1BIO_MadeGood, &r1_bio->state))
+			reschedule_retry(r1_bio);
+		else
+			raid_end_bio_io(r1_bio);
+	}
+}
+
+static void raid1_end_write_request(struct bio *bio)
+{
+	struct r1bio *r1_bio = bio->bi_private;
+	int mirror, behind = test_bit(R1BIO_BehindIO, &r1_bio->state);
+	struct r1conf *conf = r1_bio->mddev->private;
+	struct bio *to_put = NULL;
+
+	mirror = find_bio_disk(r1_bio, bio);
+
+	/*
+	 * 'one mirror IO has finished' event handler:
+	 */
+	if (bio->bi_error) {
+		set_bit(WriteErrorSeen,
+			&conf->mirrors[mirror].rdev->flags);
+		if (!test_and_set_bit(WantReplacement,
+				      &conf->mirrors[mirror].rdev->flags))
+			set_bit(MD_RECOVERY_NEEDED, &
+				conf->mddev->recovery);
+
+		set_bit(R1BIO_WriteError, &r1_bio->state);
+	} else {
+		/*
+		 * Set R1BIO_Uptodate in our master bio, so that we
+		 * will return a good error code for to the higher
+		 * levels even if IO on some other mirrored buffer
+		 * fails.
+		 *
+		 * The 'master' represents the composite IO operation
+		 * to user-side. So if something waits for IO, then it
+		 * will wait for the 'master' bio.
+		 */
+		sector_t first_bad;
+		int bad_sectors;
+
+		r1_bio->bios[mirror] = NULL;
+		to_put = bio;
+		/*
+		 * Do not set R1BIO_Uptodate if the current device is
+		 * rebuilding or Faulty. This is because we cannot use
+		 * such device for properly reading the data back (we could
+		 * potentially use it, if the current write would have felt
+		 * before rdev->recovery_offset, but for simplicity we don't
+		 * check this here.
+		 */
+		if (test_bit(In_sync, &conf->mirrors[mirror].rdev->flags) &&
+		    !test_bit(Faulty, &conf->mirrors[mirror].rdev->flags))
+			set_bit(R1BIO_Uptodate, &r1_bio->state);
+
+		/* Maybe we can clear some bad blocks. */
+		if (is_badblock(conf->mirrors[mirror].rdev,
+				r1_bio->sector, r1_bio->sectors,
+				&first_bad, &bad_sectors)) {
+			r1_bio->bios[mirror] = IO_MADE_GOOD;
+			set_bit(R1BIO_MadeGood, &r1_bio->state);
+		}
+	}
+
+	if (behind) {
+		if (test_bit(WriteMostly, &conf->mirrors[mirror].rdev->flags))
+			atomic_dec(&r1_bio->behind_remaining);
+
+		/*
+		 * In behind mode, we ACK the master bio once the I/O
+		 * has safely reached all non-writemostly
+		 * disks. Setting the Returned bit ensures that this
+		 * gets done only once -- we don't ever want to return
+		 * -EIO here, instead we'll wait
+		 */
+		if (atomic_read(&r1_bio->behind_remaining) >= (atomic_read(&r1_bio->remaining)-1) &&
+		    test_bit(R1BIO_Uptodate, &r1_bio->state)) {
+			/* Maybe we can return now */
+			if (!test_and_set_bit(R1BIO_Returned, &r1_bio->state)) {
+				struct bio *mbio = r1_bio->master_bio;
+				pr_debug("raid1: behind end write sectors"
+					 " %llu-%llu\n",
+					 (unsigned long long) mbio->bi_iter.bi_sector,
+					 (unsigned long long) bio_end_sector(mbio) - 1);
+				call_bio_endio(r1_bio);
+			}
+		}
+	}
+	if (r1_bio->bios[mirror] == NULL)
+		rdev_dec_pending(conf->mirrors[mirror].rdev,
+				 conf->mddev);
+
+	/*
+	 * Let's see if all mirrored write operations have finished
+	 * already.
+	 */
+	r1_bio_write_done(r1_bio);
+
+	if (to_put)
+		bio_put(to_put);
+}
+
+/*
+ * This routine returns the disk from which the requested read should
+ * be done. There is a per-array 'next expected sequential IO' sector
+ * number - if this matches on the next IO then we use the last disk.
+ * There is also a per-disk 'last know head position' sector that is
+ * maintained from IRQ contexts, both the normal and the resync IO
+ * completion handlers update this position correctly. If there is no
+ * perfect sequential match then we pick the disk whose head is closest.
+ *
+ * If there are 2 mirrors in the same 2 devices, performance degrades
+ * because position is mirror, not device based.
+ *
+ * The rdev for the device selected will have nr_pending incremented.
+ */
+static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sectors)
+{
+	const sector_t this_sector = r1_bio->sector;
+	int sectors;
+	int best_good_sectors;
+	int best_disk, best_dist_disk, best_pending_disk;
+	int has_nonrot_disk;
+	int disk;
+	sector_t best_dist;
+	unsigned int min_pending;
+	struct md_rdev *rdev;
+	int choose_first;
+	int choose_next_idle;
+
+	rcu_read_lock();
+	/*
+	 * Check if we can balance. We can balance on the whole
+	 * device if no resync is going on, or below the resync window.
+	 * We take the first readable disk when above the resync window.
+	 */
+ retry:
+	sectors = r1_bio->sectors;
+	best_disk = -1;
+	best_dist_disk = -1;
+	best_dist = MaxSector;
+	best_pending_disk = -1;
+	min_pending = UINT_MAX;
+	best_good_sectors = 0;
+	has_nonrot_disk = 0;
+	choose_next_idle = 0;
+
+	if ((conf->mddev->recovery_cp < this_sector + sectors) ||
+	    (mddev_is_clustered(conf->mddev) &&
+	    md_cluster_ops->area_resyncing(conf->mddev, READ, this_sector,
+		    this_sector + sectors)))
+		choose_first = 1;
+	else
+		choose_first = 0;
+
+	for (disk = 0 ; disk < conf->raid_disks * 2 ; disk++) {
+		sector_t dist;
+		sector_t first_bad;
+		int bad_sectors;
+		unsigned int pending;
+		bool nonrot;
+
+		rdev = rcu_dereference(conf->mirrors[disk].rdev);
+		if (r1_bio->bios[disk] == IO_BLOCKED
+		    || rdev == NULL
+		    || test_bit(Faulty, &rdev->flags))
+			continue;
+		if (!test_bit(In_sync, &rdev->flags) &&
+		    rdev->recovery_offset < this_sector + sectors)
+			continue;
+		if (test_bit(WriteMostly, &rdev->flags)) {
+			/* Don't balance among write-mostly, just
+			 * use the first as a last resort */
+			if (best_dist_disk < 0) {
+				if (is_badblock(rdev, this_sector, sectors,
+						&first_bad, &bad_sectors)) {
+					if (first_bad <= this_sector)
+						/* Cannot use this */
+						continue;
+					best_good_sectors = first_bad - this_sector;
+				} else
+					best_good_sectors = sectors;
+				best_dist_disk = disk;
+				best_pending_disk = disk;
+			}
+			continue;
+		}
+		/* This is a reasonable device to use.  It might
+		 * even be best.
+		 */
+		if (is_badblock(rdev, this_sector, sectors,
+				&first_bad, &bad_sectors)) {
+			if (best_dist < MaxSector)
+				/* already have a better device */
+				continue;
+			if (first_bad <= this_sector) {
+				/* cannot read here. If this is the 'primary'
+				 * device, then we must not read beyond
+				 * bad_sectors from another device..
+				 */
+				bad_sectors -= (this_sector - first_bad);
+				if (choose_first && sectors > bad_sectors)
+					sectors = bad_sectors;
+				if (best_good_sectors > sectors)
+					best_good_sectors = sectors;
+
+			} else {
+				sector_t good_sectors = first_bad - this_sector;
+				if (good_sectors > best_good_sectors) {
+					best_good_sectors = good_sectors;
+					best_disk = disk;
+				}
+				if (choose_first)
+					break;
+			}
+			continue;
+		} else
+			best_good_sectors = sectors;
+
+		nonrot = blk_queue_nonrot(bdev_get_queue(rdev->bdev));
+		has_nonrot_disk |= nonrot;
+		pending = atomic_read(&rdev->nr_pending);
+		dist = abs(this_sector - conf->mirrors[disk].head_position);
+		if (choose_first) {
+			best_disk = disk;
+			break;
+		}
+		/* Don't change to another disk for sequential reads */
+		if (conf->mirrors[disk].next_seq_sect == this_sector
+		    || dist == 0) {
+			int opt_iosize = bdev_io_opt(rdev->bdev) >> 9;
+			struct raid1_info *mirror = &conf->mirrors[disk];
+
+			best_disk = disk;
+			/*
+			 * If buffered sequential IO size exceeds optimal
+			 * iosize, check if there is idle disk. If yes, choose
+			 * the idle disk. read_balance could already choose an
+			 * idle disk before noticing it's a sequential IO in
+			 * this disk. This doesn't matter because this disk
+			 * will idle, next time it will be utilized after the
+			 * first disk has IO size exceeds optimal iosize. In
+			 * this way, iosize of the first disk will be optimal
+			 * iosize at least. iosize of the second disk might be
+			 * small, but not a big deal since when the second disk
+			 * starts IO, the first disk is likely still busy.
+			 */
+			if (nonrot && opt_iosize > 0 &&
+			    mirror->seq_start != MaxSector &&
+			    mirror->next_seq_sect > opt_iosize &&
+			    mirror->next_seq_sect - opt_iosize >=
+			    mirror->seq_start) {
+				choose_next_idle = 1;
+				continue;
+			}
+			break;
+		}
+		/* If device is idle, use it */
+		if (pending == 0) {
+			best_disk = disk;
+			break;
+		}
+
+		if (choose_next_idle)
+			continue;
+
+		if (min_pending > pending) {
+			min_pending = pending;
+			best_pending_disk = disk;
+		}
+
+		if (dist < best_dist) {
+			best_dist = dist;
+			best_dist_disk = disk;
+		}
+	}
+
+	/*
+	 * If all disks are rotational, choose the closest disk. If any disk is
+	 * non-rotational, choose the disk with less pending request even the
+	 * disk is rotational, which might/might not be optimal for raids with
+	 * mixed ratation/non-rotational disks depending on workload.
+	 */
+	if (best_disk == -1) {
+		if (has_nonrot_disk)
+			best_disk = best_pending_disk;
+		else
+			best_disk = best_dist_disk;
+	}
+
+	if (best_disk >= 0) {
+		rdev = rcu_dereference(conf->mirrors[best_disk].rdev);
+		if (!rdev)
+			goto retry;
+		atomic_inc(&rdev->nr_pending);
+		if (test_bit(Faulty, &rdev->flags)) {
+			/* cannot risk returning a device that failed
+			 * before we inc'ed nr_pending
+			 */
+			rdev_dec_pending(rdev, conf->mddev);
+			goto retry;
+		}
+		sectors = best_good_sectors;
+
+		if (conf->mirrors[best_disk].next_seq_sect != this_sector)
+			conf->mirrors[best_disk].seq_start = this_sector;
+
+		conf->mirrors[best_disk].next_seq_sect = this_sector + sectors;
+	}
+	rcu_read_unlock();
+	*max_sectors = sectors;
+
+	return best_disk;
+}
+
+static int raid1_congested(struct mddev *mddev, int bits)
+{
+	struct r1conf *conf = mddev->private;
+	int i, ret = 0;
+
+	if ((bits & (1 << WB_async_congested)) &&
+	    conf->pending_count >= max_queued_requests)
+		return 1;
+
+	rcu_read_lock();
+	for (i = 0; i < conf->raid_disks * 2; i++) {
+		struct md_rdev *rdev = rcu_dereference(conf->mirrors[i].rdev);
+		if (rdev && !test_bit(Faulty, &rdev->flags)) {
+			struct request_queue *q = bdev_get_queue(rdev->bdev);
+
+			BUG_ON(!q);
+
+			/* Note the '|| 1' - when read_balance prefers
+			 * non-congested targets, it can be removed
+			 */
+			if ((bits & (1 << WB_async_congested)) || 1)
+				ret |= bdi_congested(&q->backing_dev_info, bits);
+			else
+				ret &= bdi_congested(&q->backing_dev_info, bits);
+		}
+	}
+	rcu_read_unlock();
+	return ret;
+}
+
+static void flush_pending_writes(struct r1conf *conf)
+{
+	/* Any writes that have been queued but are awaiting
+	 * bitmap updates get flushed here.
+	 */
+	spin_lock_irq(&conf->device_lock);
+
+	if (conf->pending_bio_list.head) {
+		struct bio *bio;
+		bio = bio_list_get(&conf->pending_bio_list);
+		conf->pending_count = 0;
+		spin_unlock_irq(&conf->device_lock);
+		/* flush any pending bitmap writes to
+		 * disk before proceeding w/ I/O */
+		bitmap_unplug(conf->mddev->bitmap);
+		wake_up(&conf->wait_barrier);
+
+		while (bio) { /* submit pending writes */
+			struct bio *next = bio->bi_next;
+			bio->bi_next = NULL;
+			if (unlikely((bio->bi_rw & REQ_DISCARD) &&
+			    !blk_queue_discard(bdev_get_queue(bio->bi_bdev))))
+				/* Just ignore it */
+				bio_endio(bio);
+			else
+				generic_make_request(bio);
+			bio = next;
+		}
+	} else
+		spin_unlock_irq(&conf->device_lock);
+}
+
+/* Barriers....
+ * Sometimes we need to suspend IO while we do something else,
+ * either some resync/recovery, or reconfigure the array.
+ * To do this we raise a 'barrier'.
+ * The 'barrier' is a counter that can be raised multiple times
+ * to count how many activities are happening which preclude
+ * normal IO.
+ * We can only raise the barrier if there is no pending IO.
+ * i.e. if nr_pending == 0.
+ * We choose only to raise the barrier if no-one is waiting for the
+ * barrier to go down.  This means that as soon as an IO request
+ * is ready, no other operations which require a barrier will start
+ * until the IO request has had a chance.
+ *
+ * So: regular IO calls 'wait_barrier'.  When that returns there
+ *    is no backgroup IO happening,  It must arrange to call
+ *    allow_barrier when it has finished its IO.
+ * backgroup IO calls must call raise_barrier.  Once that returns
+ *    there is no normal IO happeing.  It must arrange to call
+ *    lower_barrier when the particular background IO completes.
+ */
+static void raise_barrier(struct r1conf *conf, sector_t sector_nr)
+{
+	spin_lock_irq(&conf->resync_lock);
+
+	/* Wait until no block IO is waiting */
+	wait_event_lock_irq(conf->wait_barrier, !conf->nr_waiting,
+			    conf->resync_lock);
+
+	/* block any new IO from starting */
+	conf->barrier++;
+	conf->next_resync = sector_nr;
+
+	/* For these conditions we must wait:
+	 * A: while the array is in frozen state
+	 * B: while barrier >= RESYNC_DEPTH, meaning resync reach
+	 *    the max count which allowed.
+	 * C: next_resync + RESYNC_SECTORS > start_next_window, meaning
+	 *    next resync will reach to the window which normal bios are
+	 *    handling.
+	 * D: while there are any active requests in the current window.
+	 */
+	wait_event_lock_irq(conf->wait_barrier,
+			    !conf->array_frozen &&
+			    conf->barrier < RESYNC_DEPTH &&
+			    conf->current_window_requests == 0 &&
+			    (conf->start_next_window >=
+			     conf->next_resync + RESYNC_SECTORS),
+			    conf->resync_lock);
+
+	conf->nr_pending++;
+	spin_unlock_irq(&conf->resync_lock);
+}
+
+static void lower_barrier(struct r1conf *conf)
+{
+	unsigned long flags;
+	BUG_ON(conf->barrier <= 0);
+	spin_lock_irqsave(&conf->resync_lock, flags);
+	conf->barrier--;
+	conf->nr_pending--;
+	spin_unlock_irqrestore(&conf->resync_lock, flags);
+	wake_up(&conf->wait_barrier);
+}
+
+static bool need_to_wait_for_sync(struct r1conf *conf, struct bio *bio)
+{
+	bool wait = false;
+
+	if (conf->array_frozen || !bio)
+		wait = true;
+	else if (conf->barrier && bio_data_dir(bio) == WRITE) {
+		if ((conf->mddev->curr_resync_completed
+		     >= bio_end_sector(bio)) ||
+		    (conf->next_resync + NEXT_NORMALIO_DISTANCE
+		     <= bio->bi_iter.bi_sector))
+			wait = false;
+		else
+			wait = true;
+	}
+
+	return wait;
+}
+
+static sector_t wait_barrier(struct r1conf *conf, struct bio *bio)
+{
+	sector_t sector = 0;
+
+	spin_lock_irq(&conf->resync_lock);
+	if (need_to_wait_for_sync(conf, bio)) {
+		conf->nr_waiting++;
+		/* Wait for the barrier to drop.
+		 * However if there are already pending
+		 * requests (preventing the barrier from
+		 * rising completely), and the
+		 * per-process bio queue isn't empty,
+		 * then don't wait, as we need to empty
+		 * that queue to allow conf->start_next_window
+		 * to increase.
+		 */
+		wait_event_lock_irq(conf->wait_barrier,
+				    !conf->array_frozen &&
+				    (!conf->barrier ||
+				     ((conf->start_next_window <
+				       conf->next_resync + RESYNC_SECTORS) &&
+				      current->bio_list &&
+				     (!bio_list_empty(&current->bio_list[0]) ||
+				      !bio_list_empty(&current->bio_list[1])))),
+				    conf->resync_lock);
+		conf->nr_waiting--;
+	}
+
+	if (bio && bio_data_dir(bio) == WRITE) {
+		if (bio->bi_iter.bi_sector >= conf->next_resync) {
+			if (conf->start_next_window == MaxSector)
+				conf->start_next_window =
+					conf->next_resync +
+					NEXT_NORMALIO_DISTANCE;
+
+			if ((conf->start_next_window + NEXT_NORMALIO_DISTANCE)
+			    <= bio->bi_iter.bi_sector)
+				conf->next_window_requests++;
+			else
+				conf->current_window_requests++;
+			sector = conf->start_next_window;
+		}
+	}
+
+	conf->nr_pending++;
+	spin_unlock_irq(&conf->resync_lock);
+	return sector;
+}
+
+static void allow_barrier(struct r1conf *conf, sector_t start_next_window,
+			  sector_t bi_sector)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&conf->resync_lock, flags);
+	conf->nr_pending--;
+	if (start_next_window) {
+		if (start_next_window == conf->start_next_window) {
+			if (conf->start_next_window + NEXT_NORMALIO_DISTANCE
+			    <= bi_sector)
+				conf->next_window_requests--;
+			else
+				conf->current_window_requests--;
+		} else
+			conf->current_window_requests--;
+
+		if (!conf->current_window_requests) {
+			if (conf->next_window_requests) {
+				conf->current_window_requests =
+					conf->next_window_requests;
+				conf->next_window_requests = 0;
+				conf->start_next_window +=
+					NEXT_NORMALIO_DISTANCE;
+			} else
+				conf->start_next_window = MaxSector;
+		}
+	}
+	spin_unlock_irqrestore(&conf->resync_lock, flags);
+	wake_up(&conf->wait_barrier);
+}
+
+static void freeze_array(struct r1conf *conf, int extra)
+{
+	/* stop syncio and normal IO and wait for everything to
+	 * go quite.
+	 * We wait until nr_pending match nr_queued+extra
+	 * This is called in the context of one normal IO request
+	 * that has failed. Thus any sync request that might be pending
+	 * will be blocked by nr_pending, and we need to wait for
+	 * pending IO requests to complete or be queued for re-try.
+	 * Thus the number queued (nr_queued) plus this request (extra)
+	 * must match the number of pending IOs (nr_pending) before
+	 * we continue.
+	 */
+	spin_lock_irq(&conf->resync_lock);
+	conf->array_frozen = 1;
+	wait_event_lock_irq_cmd(conf->wait_barrier,
+				conf->nr_pending == conf->nr_queued+extra,
+				conf->resync_lock,
+				flush_pending_writes(conf));
+	spin_unlock_irq(&conf->resync_lock);
+}
+static void unfreeze_array(struct r1conf *conf)
+{
+	/* reverse the effect of the freeze */
+	spin_lock_irq(&conf->resync_lock);
+	conf->array_frozen = 0;
+	wake_up(&conf->wait_barrier);
+	spin_unlock_irq(&conf->resync_lock);
+}
+
+/* duplicate the data pages for behind I/O
+ */
+static void alloc_behind_pages(struct bio *bio, struct r1bio *r1_bio)
+{
+	int i;
+	struct bio_vec *bvec;
+	struct bio_vec *bvecs = kzalloc(bio->bi_vcnt * sizeof(struct bio_vec),
+					GFP_NOIO);
+	if (unlikely(!bvecs))
+		return;
+
+	bio_for_each_segment_all(bvec, bio, i) {
+		bvecs[i] = *bvec;
+		bvecs[i].bv_page = alloc_page(GFP_NOIO);
+		if (unlikely(!bvecs[i].bv_page))
+			goto do_sync_io;
+		memcpy(kmap(bvecs[i].bv_page) + bvec->bv_offset,
+		       kmap(bvec->bv_page) + bvec->bv_offset, bvec->bv_len);
+		kunmap(bvecs[i].bv_page);
+		kunmap(bvec->bv_page);
+	}
+	r1_bio->behind_bvecs = bvecs;
+	r1_bio->behind_page_count = bio->bi_vcnt;
+	set_bit(R1BIO_BehindIO, &r1_bio->state);
+	return;
+
+do_sync_io:
+	for (i = 0; i < bio->bi_vcnt; i++)
+		if (bvecs[i].bv_page)
+			put_page(bvecs[i].bv_page);
+	kfree(bvecs);
+	pr_debug("%dB behind alloc failed, doing sync I/O\n",
+		 bio->bi_iter.bi_size);
+}
+
+struct raid1_plug_cb {
+	struct blk_plug_cb	cb;
+	struct bio_list		pending;
+	int			pending_cnt;
+};
+
+static void raid1_unplug(struct blk_plug_cb *cb, bool from_schedule)
+{
+	struct raid1_plug_cb *plug = container_of(cb, struct raid1_plug_cb,
+						  cb);
+	struct mddev *mddev = plug->cb.data;
+	struct r1conf *conf = mddev->private;
+	struct bio *bio;
+
+	if (from_schedule || current->bio_list) {
+		spin_lock_irq(&conf->device_lock);
+		bio_list_merge(&conf->pending_bio_list, &plug->pending);
+		conf->pending_count += plug->pending_cnt;
+		spin_unlock_irq(&conf->device_lock);
+		wake_up(&conf->wait_barrier);
+		md_wakeup_thread(mddev->thread);
+		kfree(plug);
+		return;
+	}
+
+	/* we aren't scheduling, so we can do the write-out directly. */
+	bio = bio_list_get(&plug->pending);
+	bitmap_unplug(mddev->bitmap);
+	wake_up(&conf->wait_barrier);
+
+	while (bio) { /* submit pending writes */
+		struct bio *next = bio->bi_next;
+		bio->bi_next = NULL;
+		if (unlikely((bio->bi_rw & REQ_DISCARD) &&
+		    !blk_queue_discard(bdev_get_queue(bio->bi_bdev))))
+			/* Just ignore it */
+			bio_endio(bio);
+		else
+			generic_make_request(bio);
+		bio = next;
+	}
+	kfree(plug);
+}
+
+static void make_request(struct mddev *mddev, struct bio * bio)
+{
+	struct r1conf *conf = mddev->private;
+	struct raid1_info *mirror;
+	struct r1bio *r1_bio;
+	struct bio *read_bio;
+	int i, disks;
+	struct bitmap *bitmap;
+	unsigned long flags;
+	const int rw = bio_data_dir(bio);
+	const unsigned long do_sync = (bio->bi_rw & REQ_SYNC);
+	const unsigned long do_flush_fua = (bio->bi_rw & (REQ_FLUSH | REQ_FUA));
+	const unsigned long do_discard = (bio->bi_rw
+					  & (REQ_DISCARD | REQ_SECURE));
+	const unsigned long do_same = (bio->bi_rw & REQ_WRITE_SAME);
+	struct md_rdev *blocked_rdev;
+	struct blk_plug_cb *cb;
+	struct raid1_plug_cb *plug = NULL;
+	int first_clone;
+	int sectors_handled;
+	int max_sectors;
+	sector_t start_next_window;
+
+	/*
+	 * Register the new request and wait if the reconstruction
+	 * thread has put up a bar for new requests.
+	 * Continue immediately if no resync is active currently.
+	 */
+
+	md_write_start(mddev, bio); /* wait on superblock update early */
+
+	if (bio_data_dir(bio) == WRITE &&
+	    ((bio_end_sector(bio) > mddev->suspend_lo &&
+	    bio->bi_iter.bi_sector < mddev->suspend_hi) ||
+	    (mddev_is_clustered(mddev) &&
+	     md_cluster_ops->area_resyncing(mddev, WRITE,
+		     bio->bi_iter.bi_sector, bio_end_sector(bio))))) {
+		/* As the suspend_* range is controlled by
+		 * userspace, we want an interruptible
+		 * wait.
+		 */
+		DEFINE_WAIT(w);
+		for (;;) {
+			sigset_t full, old;
+			prepare_to_wait(&conf->wait_barrier,
+					&w, TASK_INTERRUPTIBLE);
+			if (bio_end_sector(bio) <= mddev->suspend_lo ||
+			    bio->bi_iter.bi_sector >= mddev->suspend_hi ||
+			    (mddev_is_clustered(mddev) &&
+			     !md_cluster_ops->area_resyncing(mddev, WRITE,
+				     bio->bi_iter.bi_sector, bio_end_sector(bio))))
+				break;
+			sigfillset(&full);
+			sigprocmask(SIG_BLOCK, &full, &old);
+			schedule();
+			sigprocmask(SIG_SETMASK, &old, NULL);
+		}
+		finish_wait(&conf->wait_barrier, &w);
+	}
+
+	start_next_window = wait_barrier(conf, bio);
+
+	bitmap = mddev->bitmap;
+
+	/*
+	 * make_request() can abort the operation when READA is being
+	 * used and no empty request is available.
+	 *
+	 */
+	r1_bio = mempool_alloc(conf->r1bio_pool, GFP_NOIO);
+
+	r1_bio->master_bio = bio;
+	r1_bio->sectors = bio_sectors(bio);
+	r1_bio->state = 0;
+	r1_bio->mddev = mddev;
+	r1_bio->sector = bio->bi_iter.bi_sector;
+
+	/* We might need to issue multiple reads to different
+	 * devices if there are bad blocks around, so we keep
+	 * track of the number of reads in bio->bi_phys_segments.
+	 * If this is 0, there is only one r1_bio and no locking
+	 * will be needed when requests complete.  If it is
+	 * non-zero, then it is the number of not-completed requests.
+	 */
+	bio->bi_phys_segments = 0;
+	bio_clear_flag(bio, BIO_SEG_VALID);
+
+	if (rw == READ) {
+		/*
+		 * read balancing logic:
+		 */
+		int rdisk;
+
+read_again:
+		rdisk = read_balance(conf, r1_bio, &max_sectors);
+
+		if (rdisk < 0) {
+			/* couldn't find anywhere to read from */
+			raid_end_bio_io(r1_bio);
+			return;
+		}
+		mirror = conf->mirrors + rdisk;
+
+		if (test_bit(WriteMostly, &mirror->rdev->flags) &&
+		    bitmap) {
+			/* Reading from a write-mostly device must
+			 * take care not to over-take any writes
+			 * that are 'behind'
+			 */
+			wait_event(bitmap->behind_wait,
+				   atomic_read(&bitmap->behind_writes) == 0);
+		}
+		r1_bio->read_disk = rdisk;
+		r1_bio->start_next_window = 0;
+
+		read_bio = bio_clone_mddev(bio, GFP_NOIO, mddev);
+		bio_trim(read_bio, r1_bio->sector - bio->bi_iter.bi_sector,
+			 max_sectors);
+
+		r1_bio->bios[rdisk] = read_bio;
+
+		read_bio->bi_iter.bi_sector = r1_bio->sector +
+			mirror->rdev->data_offset;
+		read_bio->bi_bdev = mirror->rdev->bdev;
+		read_bio->bi_end_io = raid1_end_read_request;
+		read_bio->bi_rw = READ | do_sync;
+		read_bio->bi_private = r1_bio;
+
+		if (max_sectors < r1_bio->sectors) {
+			/* could not read all from this device, so we will
+			 * need another r1_bio.
+			 */
+
+			sectors_handled = (r1_bio->sector + max_sectors
+					   - bio->bi_iter.bi_sector);
+			r1_bio->sectors = max_sectors;
+			spin_lock_irq(&conf->device_lock);
+			if (bio->bi_phys_segments == 0)
+				bio->bi_phys_segments = 2;
+			else
+				bio->bi_phys_segments++;
+			spin_unlock_irq(&conf->device_lock);
+			/* Cannot call generic_make_request directly
+			 * as that will be queued in __make_request
+			 * and subsequent mempool_alloc might block waiting
+			 * for it.  So hand bio over to raid1d.
+			 */
+			reschedule_retry(r1_bio);
+
+			r1_bio = mempool_alloc(conf->r1bio_pool, GFP_NOIO);
+
+			r1_bio->master_bio = bio;
+			r1_bio->sectors = bio_sectors(bio) - sectors_handled;
+			r1_bio->state = 0;
+			r1_bio->mddev = mddev;
+			r1_bio->sector = bio->bi_iter.bi_sector +
+				sectors_handled;
+			goto read_again;
+		} else
+			generic_make_request(read_bio);
+		return;
+	}
+
+	/*
+	 * WRITE:
+	 */
+	if (conf->pending_count >= max_queued_requests) {
+		md_wakeup_thread(mddev->thread);
+		wait_event(conf->wait_barrier,
+			   conf->pending_count < max_queued_requests);
+	}
+	/* first select target devices under rcu_lock and
+	 * inc refcount on their rdev.  Record them by setting
+	 * bios[x] to bio
+	 * If there are known/acknowledged bad blocks on any device on
+	 * which we have seen a write error, we want to avoid writing those
+	 * blocks.
+	 * This potentially requires several writes to write around
+	 * the bad blocks.  Each set of writes gets it's own r1bio
+	 * with a set of bios attached.
+	 */
+
+	disks = conf->raid_disks * 2;
+ retry_write:
+	r1_bio->start_next_window = start_next_window;
+	blocked_rdev = NULL;
+	rcu_read_lock();
+	max_sectors = r1_bio->sectors;
+	for (i = 0;  i < disks; i++) {
+		struct md_rdev *rdev = rcu_dereference(conf->mirrors[i].rdev);
+		if (rdev && unlikely(test_bit(Blocked, &rdev->flags))) {
+			atomic_inc(&rdev->nr_pending);
+			blocked_rdev = rdev;
+			break;
+		}
+		r1_bio->bios[i] = NULL;
+		if (!rdev || test_bit(Faulty, &rdev->flags)) {
+			if (i < conf->raid_disks)
+				set_bit(R1BIO_Degraded, &r1_bio->state);
+			continue;
+		}
+
+		atomic_inc(&rdev->nr_pending);
+		if (test_bit(WriteErrorSeen, &rdev->flags)) {
+			sector_t first_bad;
+			int bad_sectors;
+			int is_bad;
+
+			is_bad = is_badblock(rdev, r1_bio->sector,
+					     max_sectors,
+					     &first_bad, &bad_sectors);
+			if (is_bad < 0) {
+				/* mustn't write here until the bad block is
+				 * acknowledged*/
+				set_bit(BlockedBadBlocks, &rdev->flags);
+				blocked_rdev = rdev;
+				break;
+			}
+			if (is_bad && first_bad <= r1_bio->sector) {
+				/* Cannot write here at all */
+				bad_sectors -= (r1_bio->sector - first_bad);
+				if (bad_sectors < max_sectors)
+					/* mustn't write more than bad_sectors
+					 * to other devices yet
+					 */
+					max_sectors = bad_sectors;
+				rdev_dec_pending(rdev, mddev);
+				/* We don't set R1BIO_Degraded as that
+				 * only applies if the disk is
+				 * missing, so it might be re-added,
+				 * and we want to know to recover this
+				 * chunk.
+				 * In this case the device is here,
+				 * and the fact that this chunk is not
+				 * in-sync is recorded in the bad
+				 * block log
+				 */
+				continue;
+			}
+			if (is_bad) {
+				int good_sectors = first_bad - r1_bio->sector;
+				if (good_sectors < max_sectors)
+					max_sectors = good_sectors;
+			}
+		}
+		r1_bio->bios[i] = bio;
+	}
+	rcu_read_unlock();
+
+	if (unlikely(blocked_rdev)) {
+		/* Wait for this device to become unblocked */
+		int j;
+		sector_t old = start_next_window;
+
+		for (j = 0; j < i; j++)
+			if (r1_bio->bios[j])
+				rdev_dec_pending(conf->mirrors[j].rdev, mddev);
+		r1_bio->state = 0;
+		allow_barrier(conf, start_next_window, bio->bi_iter.bi_sector);
+		md_wait_for_blocked_rdev(blocked_rdev, mddev);
+		start_next_window = wait_barrier(conf, bio);
+		/*
+		 * We must make sure the multi r1bios of bio have
+		 * the same value of bi_phys_segments
+		 */
+		if (bio->bi_phys_segments && old &&
+		    old != start_next_window)
+			/* Wait for the former r1bio(s) to complete */
+			wait_event(conf->wait_barrier,
+				   bio->bi_phys_segments == 1);
+		goto retry_write;
+	}
+
+	if (max_sectors < r1_bio->sectors) {
+		/* We are splitting this write into multiple parts, so
+		 * we need to prepare for allocating another r1_bio.
+		 */
+		r1_bio->sectors = max_sectors;
+		spin_lock_irq(&conf->device_lock);
+		if (bio->bi_phys_segments == 0)
+			bio->bi_phys_segments = 2;
+		else
+			bio->bi_phys_segments++;
+		spin_unlock_irq(&conf->device_lock);
+	}
+	sectors_handled = r1_bio->sector + max_sectors - bio->bi_iter.bi_sector;
+
+	atomic_set(&r1_bio->remaining, 1);
+	atomic_set(&r1_bio->behind_remaining, 0);
+
+	first_clone = 1;
+	for (i = 0; i < disks; i++) {
+		struct bio *mbio;
+		if (!r1_bio->bios[i])
+			continue;
+
+		mbio = bio_clone_mddev(bio, GFP_NOIO, mddev);
+		bio_trim(mbio, r1_bio->sector - bio->bi_iter.bi_sector, max_sectors);
+
+		if (first_clone) {
+			/* do behind I/O ?
+			 * Not if there are too many, or cannot
+			 * allocate memory, or a reader on WriteMostly
+			 * is waiting for behind writes to flush */
+			if (bitmap &&
+			    (atomic_read(&bitmap->behind_writes)
+			     < mddev->bitmap_info.max_write_behind) &&
+			    !waitqueue_active(&bitmap->behind_wait))
+				alloc_behind_pages(mbio, r1_bio);
+
+			bitmap_startwrite(bitmap, r1_bio->sector,
+					  r1_bio->sectors,
+					  test_bit(R1BIO_BehindIO,
+						   &r1_bio->state));
+			first_clone = 0;
+		}
+		if (r1_bio->behind_bvecs) {
+			struct bio_vec *bvec;
+			int j;
+
+			/*
+			 * We trimmed the bio, so _all is legit
+			 */
+			bio_for_each_segment_all(bvec, mbio, j)
+				bvec->bv_page = r1_bio->behind_bvecs[j].bv_page;
+			if (test_bit(WriteMostly, &conf->mirrors[i].rdev->flags))
+				atomic_inc(&r1_bio->behind_remaining);
+		}
+
+		r1_bio->bios[i] = mbio;
+
+		mbio->bi_iter.bi_sector	= (r1_bio->sector +
+				   conf->mirrors[i].rdev->data_offset);
+		mbio->bi_bdev = conf->mirrors[i].rdev->bdev;
+		mbio->bi_end_io	= raid1_end_write_request;
+		mbio->bi_rw =
+			WRITE | do_flush_fua | do_sync | do_discard | do_same;
+		mbio->bi_private = r1_bio;
+
+		atomic_inc(&r1_bio->remaining);
+
+		cb = blk_check_plugged(raid1_unplug, mddev, sizeof(*plug));
+		if (cb)
+			plug = container_of(cb, struct raid1_plug_cb, cb);
+		else
+			plug = NULL;
+		spin_lock_irqsave(&conf->device_lock, flags);
+		if (plug) {
+			bio_list_add(&plug->pending, mbio);
+			plug->pending_cnt++;
+		} else {
+			bio_list_add(&conf->pending_bio_list, mbio);
+			conf->pending_count++;
+		}
+		spin_unlock_irqrestore(&conf->device_lock, flags);
+		if (!plug)
+			md_wakeup_thread(mddev->thread);
+	}
+	/* Mustn't call r1_bio_write_done before this next test,
+	 * as it could result in the bio being freed.
+	 */
+	if (sectors_handled < bio_sectors(bio)) {
+		r1_bio_write_done(r1_bio);
+		/* We need another r1_bio.  It has already been counted
+		 * in bio->bi_phys_segments
+		 */
+		r1_bio = mempool_alloc(conf->r1bio_pool, GFP_NOIO);
+		r1_bio->master_bio = bio;
+		r1_bio->sectors = bio_sectors(bio) - sectors_handled;
+		r1_bio->state = 0;
+		r1_bio->mddev = mddev;
+		r1_bio->sector = bio->bi_iter.bi_sector + sectors_handled;
+		goto retry_write;
+	}
+
+	r1_bio_write_done(r1_bio);
+
+	/* In case raid1d snuck in to freeze_array */
+	wake_up(&conf->wait_barrier);
+}
+
+static void status(struct seq_file *seq, struct mddev *mddev)
+{
+	struct r1conf *conf = mddev->private;
+	int i;
+
+	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->mirrors[i].rdev);
+		seq_printf(seq, "%s",
+			   rdev && test_bit(In_sync, &rdev->flags) ? "U" : "_");
+	}
+	rcu_read_unlock();
+	seq_printf(seq, "]");
+}
+
+static void error(struct mddev *mddev, struct md_rdev *rdev)
+{
+	char b[BDEVNAME_SIZE];
+	struct r1conf *conf = mddev->private;
+	unsigned long flags;
+
+	/*
+	 * If it is not operational, then we have already marked it as dead
+	 * else if it is the last working disks, ignore the error, let the
+	 * next level up know.
+	 * else mark the drive as failed
+	 */
+	if (test_bit(In_sync, &rdev->flags)
+	    && (conf->raid_disks - mddev->degraded) == 1) {
+		/*
+		 * Don't fail the drive, act as though we were just a
+		 * normal single drive.
+		 * However don't try a recovery from this drive as
+		 * it is very likely to fail.
+		 */
+		conf->recovery_disabled = mddev->recovery_disabled;
+		return;
+	}
+	set_bit(Blocked, &rdev->flags);
+	spin_lock_irqsave(&conf->device_lock, flags);
+	if (test_and_clear_bit(In_sync, &rdev->flags)) {
+		mddev->degraded++;
+		set_bit(Faulty, &rdev->flags);
+	} else
+		set_bit(Faulty, &rdev->flags);
+	spin_unlock_irqrestore(&conf->device_lock, flags);
+	/*
+	 * if recovery is running, make sure it aborts.
+	 */
+	set_bit(MD_RECOVERY_INTR, &mddev->recovery);
+	set_bit(MD_CHANGE_DEVS, &mddev->flags);
+	set_bit(MD_CHANGE_PENDING, &mddev->flags);
+	printk(KERN_ALERT
+	       "md/raid1:%s: Disk failure on %s, disabling device.\n"
+	       "md/raid1:%s: Operation continuing on %d devices.\n",
+	       mdname(mddev), bdevname(rdev->bdev, b),
+	       mdname(mddev), conf->raid_disks - mddev->degraded);
+}
+
+static void print_conf(struct r1conf *conf)
+{
+	int i;
+
+	printk(KERN_DEBUG "RAID1 conf printout:\n");
+	if (!conf) {
+		printk(KERN_DEBUG "(!conf)\n");
+		return;
+	}
+	printk(KERN_DEBUG " --- wd:%d rd:%d\n", conf->raid_disks - conf->mddev->degraded,
+		conf->raid_disks);
+
+	rcu_read_lock();
+	for (i = 0; i < conf->raid_disks; i++) {
+		char b[BDEVNAME_SIZE];
+		struct md_rdev *rdev = rcu_dereference(conf->mirrors[i].rdev);
+		if (rdev)
+			printk(KERN_DEBUG " disk %d, wo:%d, o:%d, dev:%s\n",
+			       i, !test_bit(In_sync, &rdev->flags),
+			       !test_bit(Faulty, &rdev->flags),
+			       bdevname(rdev->bdev,b));
+	}
+	rcu_read_unlock();
+}
+
+static void close_sync(struct r1conf *conf)
+{
+	wait_barrier(conf, NULL);
+	allow_barrier(conf, 0, 0);
+
+	mempool_destroy(conf->r1buf_pool);
+	conf->r1buf_pool = NULL;
+
+	spin_lock_irq(&conf->resync_lock);
+	conf->next_resync = MaxSector - 2 * NEXT_NORMALIO_DISTANCE;
+	conf->start_next_window = MaxSector;
+	conf->current_window_requests +=
+		conf->next_window_requests;
+	conf->next_window_requests = 0;
+	spin_unlock_irq(&conf->resync_lock);
+}
+
+static int raid1_spare_active(struct mddev *mddev)
+{
+	int i;
+	struct r1conf *conf = mddev->private;
+	int count = 0;
+	unsigned long flags;
+
+	/*
+	 * Find all failed disks within the RAID1 configuration
+	 * and mark them readable.
+	 * Called under mddev lock, so rcu protection not needed.
+	 * device_lock used to avoid races with raid1_end_read_request
+	 * which expects 'In_sync' flags and ->degraded to be consistent.
+	 */
+	spin_lock_irqsave(&conf->device_lock, flags);
+	for (i = 0; i < conf->raid_disks; i++) {
+		struct md_rdev *rdev = conf->mirrors[i].rdev;
+		struct md_rdev *repl = conf->mirrors[conf->raid_disks + i].rdev;
+		if (repl
+		    && !test_bit(Candidate, &repl->flags)
+		    && repl->recovery_offset == MaxSector
+		    && !test_bit(Faulty, &repl->flags)
+		    && !test_and_set_bit(In_sync, &repl->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);
+			}
+		}
+		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);
+		}
+	}
+	mddev->degraded -= count;
+	spin_unlock_irqrestore(&conf->device_lock, flags);
+
+	print_conf(conf);
+	return count;
+}
+
+static int raid1_add_disk(struct mddev *mddev, struct md_rdev *rdev)
+{
+	struct r1conf *conf = mddev->private;
+	int err = -EEXIST;
+	int mirror = 0;
+	struct raid1_info *p;
+	int first = 0;
+	int last = conf->raid_disks - 1;
+
+	if (mddev->recovery_disabled == conf->recovery_disabled)
+		return -EBUSY;
+
+	if (md_integrity_add_rdev(rdev, mddev))
+		return -ENXIO;
+
+	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 >= 0 &&
+	    rdev->saved_raid_disk >= first &&
+	    conf->mirrors[rdev->saved_raid_disk].rdev == NULL)
+		first = last = rdev->saved_raid_disk;
+
+	for (mirror = first; mirror <= last; mirror++) {
+		p = conf->mirrors+mirror;
+		if (!p->rdev) {
+
+			if (mddev->gendisk)
+				disk_stack_limits(mddev->gendisk, rdev->bdev,
+						  rdev->data_offset << 9);
+
+			p->head_position = 0;
+			rdev->raid_disk = mirror;
+			err = 0;
+			/* As all devices are equivalent, we don't need a full recovery
+			 * if this was recently any drive of the array
+			 */
+			if (rdev->saved_raid_disk < 0)
+				conf->fullsync = 1;
+			rcu_assign_pointer(p->rdev, rdev);
+			break;
+		}
+		if (test_bit(WantReplacement, &p->rdev->flags) &&
+		    p[conf->raid_disks].rdev == NULL) {
+			/* Add this device as a replacement */
+			clear_bit(In_sync, &rdev->flags);
+			set_bit(Replacement, &rdev->flags);
+			rdev->raid_disk = mirror;
+			err = 0;
+			conf->fullsync = 1;
+			rcu_assign_pointer(p[conf->raid_disks].rdev, rdev);
+			break;
+		}
+	}
+	if (mddev->queue && blk_queue_discard(bdev_get_queue(rdev->bdev)))
+		queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, mddev->queue);
+	print_conf(conf);
+	return err;
+}
+
+static int raid1_remove_disk(struct mddev *mddev, struct md_rdev *rdev)
+{
+	struct r1conf *conf = mddev->private;
+	int err = 0;
+	int number = rdev->raid_disk;
+	struct raid1_info *p = conf->mirrors + number;
+
+	if (rdev != p->rdev)
+		p = conf->mirrors + conf->raid_disks + number;
+
+	print_conf(conf);
+	if (rdev == p->rdev) {
+		if (test_bit(In_sync, &rdev->flags) ||
+		    atomic_read(&rdev->nr_pending)) {
+			err = -EBUSY;
+			goto abort;
+		}
+		/* Only remove non-faulty devices if recovery
+		 * is not possible.
+		 */
+		if (!test_bit(Faulty, &rdev->flags) &&
+		    mddev->recovery_disabled != conf->recovery_disabled &&
+		    mddev->degraded < conf->raid_disks) {
+			err = -EBUSY;
+			goto abort;
+		}
+		p->rdev = NULL;
+		synchronize_rcu();
+		if (atomic_read(&rdev->nr_pending)) {
+			/* lost the race, try later */
+			err = -EBUSY;
+			p->rdev = rdev;
+			goto abort;
+		} else if (conf->mirrors[conf->raid_disks + number].rdev) {
+			/* We just removed a device that is being replaced.
+			 * Move down the replacement.  We drain all IO before
+			 * doing this to avoid confusion.
+			 */
+			struct md_rdev *repl =
+				conf->mirrors[conf->raid_disks + number].rdev;
+			freeze_array(conf, 0);
+			clear_bit(Replacement, &repl->flags);
+			p->rdev = repl;
+			conf->mirrors[conf->raid_disks + number].rdev = NULL;
+			unfreeze_array(conf);
+			clear_bit(WantReplacement, &rdev->flags);
+		} else
+			clear_bit(WantReplacement, &rdev->flags);
+		err = md_integrity_register(mddev);
+	}
+abort:
+
+	print_conf(conf);
+	return err;
+}
+
+static void end_sync_read(struct bio *bio)
+{
+	struct r1bio *r1_bio = bio->bi_private;
+
+	update_head_pos(r1_bio->read_disk, r1_bio);
+
+	/*
+	 * we have read a block, now it needs to be re-written,
+	 * or re-read if the read failed.
+	 * We don't do much here, just schedule handling by raid1d
+	 */
+	if (!bio->bi_error)
+		set_bit(R1BIO_Uptodate, &r1_bio->state);
+
+	if (atomic_dec_and_test(&r1_bio->remaining))
+		reschedule_retry(r1_bio);
+}
+
+static void end_sync_write(struct bio *bio)
+{
+	int uptodate = !bio->bi_error;
+	struct r1bio *r1_bio = bio->bi_private;
+	struct mddev *mddev = r1_bio->mddev;
+	struct r1conf *conf = mddev->private;
+	int mirror=0;
+	sector_t first_bad;
+	int bad_sectors;
+
+	mirror = find_bio_disk(r1_bio, bio);
+
+	if (!uptodate) {
+		sector_t sync_blocks = 0;
+		sector_t s = r1_bio->sector;
+		long sectors_to_go = r1_bio->sectors;
+		/* make sure these bits doesn't get cleared. */
+		do {
+			bitmap_end_sync(mddev->bitmap, s,
+					&sync_blocks, 1);
+			s += sync_blocks;
+			sectors_to_go -= sync_blocks;
+		} while (sectors_to_go > 0);
+		set_bit(WriteErrorSeen,
+			&conf->mirrors[mirror].rdev->flags);
+		if (!test_and_set_bit(WantReplacement,
+				      &conf->mirrors[mirror].rdev->flags))
+			set_bit(MD_RECOVERY_NEEDED, &
+				mddev->recovery);
+		set_bit(R1BIO_WriteError, &r1_bio->state);
+	} else if (is_badblock(conf->mirrors[mirror].rdev,
+			       r1_bio->sector,
+			       r1_bio->sectors,
+			       &first_bad, &bad_sectors) &&
+		   !is_badblock(conf->mirrors[r1_bio->read_disk].rdev,
+				r1_bio->sector,
+				r1_bio->sectors,
+				&first_bad, &bad_sectors)
+		)
+		set_bit(R1BIO_MadeGood, &r1_bio->state);
+
+	if (atomic_dec_and_test(&r1_bio->remaining)) {
+		int s = r1_bio->sectors;
+		if (test_bit(R1BIO_MadeGood, &r1_bio->state) ||
+		    test_bit(R1BIO_WriteError, &r1_bio->state))
+			reschedule_retry(r1_bio);
+		else {
+			put_buf(r1_bio);
+			md_done_sync(mddev, s, uptodate);
+		}
+	}
+}
+
+static int r1_sync_page_io(struct md_rdev *rdev, sector_t sector,
+			    int sectors, struct page *page, int rw)
+{
+	if (sync_page_io(rdev, sector, sectors << 9, page, rw, false))
+		/* success */
+		return 1;
+	if (rw == WRITE) {
+		set_bit(WriteErrorSeen, &rdev->flags);
+		if (!test_and_set_bit(WantReplacement,
+				      &rdev->flags))
+			set_bit(MD_RECOVERY_NEEDED, &
+				rdev->mddev->recovery);
+	}
+	/* need to record an error - either for the block or the device */
+	if (!rdev_set_badblocks(rdev, sector, sectors, 0))
+		md_error(rdev->mddev, rdev);
+	return 0;
+}
+
+static int fix_sync_read_error(struct r1bio *r1_bio)
+{
+	/* Try some synchronous reads of other devices to get
+	 * good data, much like with normal read errors.  Only
+	 * read into the pages we already have so we don't
+	 * need to re-issue the read request.
+	 * We don't need to freeze the array, because being in an
+	 * active sync request, there is no normal IO, and
+	 * no overlapping syncs.
+	 * We don't need to check is_badblock() again as we
+	 * made sure that anything with a bad block in range
+	 * will have bi_end_io clear.
+	 */
+	struct mddev *mddev = r1_bio->mddev;
+	struct r1conf *conf = mddev->private;
+	struct bio *bio = r1_bio->bios[r1_bio->read_disk];
+	sector_t sect = r1_bio->sector;
+	int sectors = r1_bio->sectors;
+	int idx = 0;
+
+	while(sectors) {
+		int s = sectors;
+		int d = r1_bio->read_disk;
+		int success = 0;
+		struct md_rdev *rdev;
+		int start;
+
+		if (s > (PAGE_SIZE>>9))
+			s = PAGE_SIZE >> 9;
+		do {
+			if (r1_bio->bios[d]->bi_end_io == end_sync_read) {
+				/* No rcu protection needed here devices
+				 * can only be removed when no resync is
+				 * active, and resync is currently active
+				 */
+				rdev = conf->mirrors[d].rdev;
+				if (sync_page_io(rdev, sect, s<<9,
+						 bio->bi_io_vec[idx].bv_page,
+						 READ, false)) {
+					success = 1;
+					break;
+				}
+			}
+			d++;
+			if (d == conf->raid_disks * 2)
+				d = 0;
+		} while (!success && d != r1_bio->read_disk);
+
+		if (!success) {
+			char b[BDEVNAME_SIZE];
+			int abort = 0;
+			/* Cannot read from anywhere, this block is lost.
+			 * Record a bad block on each device.  If that doesn't
+			 * work just disable and interrupt the recovery.
+			 * Don't fail devices as that won't really help.
+			 */
+			printk(KERN_ALERT "md/raid1:%s: %s: unrecoverable I/O read error"
+			       " for block %llu\n",
+			       mdname(mddev),
+			       bdevname(bio->bi_bdev, b),
+			       (unsigned long long)r1_bio->sector);
+			for (d = 0; d < conf->raid_disks * 2; d++) {
+				rdev = conf->mirrors[d].rdev;
+				if (!rdev || test_bit(Faulty, &rdev->flags))
+					continue;
+				if (!rdev_set_badblocks(rdev, sect, s, 0))
+					abort = 1;
+			}
+			if (abort) {
+				conf->recovery_disabled =
+					mddev->recovery_disabled;
+				set_bit(MD_RECOVERY_INTR, &mddev->recovery);
+				md_done_sync(mddev, r1_bio->sectors, 0);
+				put_buf(r1_bio);
+				return 0;
+			}
+			/* Try next page */
+			sectors -= s;
+			sect += s;
+			idx++;
+			continue;
+		}
+
+		start = d;
+		/* write it back and re-read */
+		while (d != r1_bio->read_disk) {
+			if (d == 0)
+				d = conf->raid_disks * 2;
+			d--;
+			if (r1_bio->bios[d]->bi_end_io != end_sync_read)
+				continue;
+			rdev = conf->mirrors[d].rdev;
+			if (r1_sync_page_io(rdev, sect, s,
+					    bio->bi_io_vec[idx].bv_page,
+					    WRITE) == 0) {
+				r1_bio->bios[d]->bi_end_io = NULL;
+				rdev_dec_pending(rdev, mddev);
+			}
+		}
+		d = start;
+		while (d != r1_bio->read_disk) {
+			if (d == 0)
+				d = conf->raid_disks * 2;
+			d--;
+			if (r1_bio->bios[d]->bi_end_io != end_sync_read)
+				continue;
+			rdev = conf->mirrors[d].rdev;
+			if (r1_sync_page_io(rdev, sect, s,
+					    bio->bi_io_vec[idx].bv_page,
+					    READ) != 0)
+				atomic_add(s, &rdev->corrected_errors);
+		}
+		sectors -= s;
+		sect += s;
+		idx ++;
+	}
+	set_bit(R1BIO_Uptodate, &r1_bio->state);
+	bio->bi_error = 0;
+	return 1;
+}
+
+static void process_checks(struct r1bio *r1_bio)
+{
+	/* We have read all readable devices.  If we haven't
+	 * got the block, then there is no hope left.
+	 * If we have, then we want to do a comparison
+	 * and skip the write if everything is the same.
+	 * If any blocks failed to read, then we need to
+	 * attempt an over-write
+	 */
+	struct mddev *mddev = r1_bio->mddev;
+	struct r1conf *conf = mddev->private;
+	int primary;
+	int i;
+	int vcnt;
+
+	/* Fix variable parts of all bios */
+	vcnt = (r1_bio->sectors + PAGE_SIZE / 512 - 1) >> (PAGE_SHIFT - 9);
+	for (i = 0; i < conf->raid_disks * 2; i++) {
+		int j;
+		int size;
+		int error;
+		struct bio *b = r1_bio->bios[i];
+		if (b->bi_end_io != end_sync_read)
+			continue;
+		/* fixup the bio for reuse, but preserve errno */
+		error = b->bi_error;
+		bio_reset(b);
+		b->bi_error = error;
+		b->bi_vcnt = vcnt;
+		b->bi_iter.bi_size = r1_bio->sectors << 9;
+		b->bi_iter.bi_sector = r1_bio->sector +
+			conf->mirrors[i].rdev->data_offset;
+		b->bi_bdev = conf->mirrors[i].rdev->bdev;
+		b->bi_end_io = end_sync_read;
+		b->bi_private = r1_bio;
+
+		size = b->bi_iter.bi_size;
+		for (j = 0; j < vcnt ; j++) {
+			struct bio_vec *bi;
+			bi = &b->bi_io_vec[j];
+			bi->bv_offset = 0;
+			if (size > PAGE_SIZE)
+				bi->bv_len = PAGE_SIZE;
+			else
+				bi->bv_len = size;
+			size -= PAGE_SIZE;
+		}
+	}
+	for (primary = 0; primary < conf->raid_disks * 2; primary++)
+		if (r1_bio->bios[primary]->bi_end_io == end_sync_read &&
+		    !r1_bio->bios[primary]->bi_error) {
+			r1_bio->bios[primary]->bi_end_io = NULL;
+			rdev_dec_pending(conf->mirrors[primary].rdev, mddev);
+			break;
+		}
+	r1_bio->read_disk = primary;
+	for (i = 0; i < conf->raid_disks * 2; i++) {
+		int j;
+		struct bio *pbio = r1_bio->bios[primary];
+		struct bio *sbio = r1_bio->bios[i];
+		int error = sbio->bi_error;
+
+		if (sbio->bi_end_io != end_sync_read)
+			continue;
+		/* Now we can 'fixup' the error value */
+		sbio->bi_error = 0;
+
+		if (!error) {
+			for (j = vcnt; j-- ; ) {
+				struct page *p, *s;
+				p = pbio->bi_io_vec[j].bv_page;
+				s = sbio->bi_io_vec[j].bv_page;
+				if (memcmp(page_address(p),
+					   page_address(s),
+					   sbio->bi_io_vec[j].bv_len))
+					break;
+			}
+		} else
+			j = 0;
+		if (j >= 0)
+			atomic64_add(r1_bio->sectors, &mddev->resync_mismatches);
+		if (j < 0 || (test_bit(MD_RECOVERY_CHECK, &mddev->recovery)
+			      && !error)) {
+			/* No need to write to this device. */
+			sbio->bi_end_io = NULL;
+			rdev_dec_pending(conf->mirrors[i].rdev, mddev);
+			continue;
+		}
+
+		bio_copy_data(sbio, pbio);
+	}
+}
+
+static void sync_request_write(struct mddev *mddev, struct r1bio *r1_bio)
+{
+	struct r1conf *conf = mddev->private;
+	int i;
+	int disks = conf->raid_disks * 2;
+	struct bio *bio, *wbio;
+
+	bio = r1_bio->bios[r1_bio->read_disk];
+
+	if (!test_bit(R1BIO_Uptodate, &r1_bio->state))
+		/* ouch - failed to read all of that. */
+		if (!fix_sync_read_error(r1_bio))
+			return;
+
+	if (test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery))
+		process_checks(r1_bio);
+
+	/*
+	 * schedule writes
+	 */
+	atomic_set(&r1_bio->remaining, 1);
+	for (i = 0; i < disks ; i++) {
+		wbio = r1_bio->bios[i];
+		if (wbio->bi_end_io == NULL ||
+		    (wbio->bi_end_io == end_sync_read &&
+		     (i == r1_bio->read_disk ||
+		      !test_bit(MD_RECOVERY_SYNC, &mddev->recovery))))
+			continue;
+
+		wbio->bi_rw = WRITE;
+		wbio->bi_end_io = end_sync_write;
+		atomic_inc(&r1_bio->remaining);
+		md_sync_acct(conf->mirrors[i].rdev->bdev, bio_sectors(wbio));
+
+		generic_make_request(wbio);
+	}
+
+	if (atomic_dec_and_test(&r1_bio->remaining)) {
+		/* if we're here, all write(s) have completed, so clean up */
+		int s = r1_bio->sectors;
+		if (test_bit(R1BIO_MadeGood, &r1_bio->state) ||
+		    test_bit(R1BIO_WriteError, &r1_bio->state))
+			reschedule_retry(r1_bio);
+		else {
+			put_buf(r1_bio);
+			md_done_sync(mddev, s, 1);
+		}
+	}
+}
+
+/*
+ * This is a kernel thread which:
+ *
+ *	1.	Retries failed read operations on working mirrors.
+ *	2.	Updates the raid superblock when problems encounter.
+ *	3.	Performs writes following reads for array synchronising.
+ */
+
+static void fix_read_error(struct r1conf *conf, int read_disk,
+			   sector_t sect, int sectors)
+{
+	struct mddev *mddev = conf->mddev;
+	while(sectors) {
+		int s = sectors;
+		int d = read_disk;
+		int success = 0;
+		int start;
+		struct md_rdev *rdev;
+
+		if (s > (PAGE_SIZE>>9))
+			s = PAGE_SIZE >> 9;
+
+		do {
+			/* Note: no rcu protection needed here
+			 * as this is synchronous in the raid1d thread
+			 * which is the thread that might remove
+			 * a device.  If raid1d ever becomes multi-threaded....
+			 */
+			sector_t first_bad;
+			int bad_sectors;
+
+			rdev = conf->mirrors[d].rdev;
+			if (rdev &&
+			    (test_bit(In_sync, &rdev->flags) ||
+			     (!test_bit(Faulty, &rdev->flags) &&
+			      rdev->recovery_offset >= sect + s)) &&
+			    is_badblock(rdev, sect, s,
+					&first_bad, &bad_sectors) == 0 &&
+			    sync_page_io(rdev, sect, s<<9,
+					 conf->tmppage, READ, false))
+				success = 1;
+			else {
+				d++;
+				if (d == conf->raid_disks * 2)
+					d = 0;
+			}
+		} while (!success && d != read_disk);
+
+		if (!success) {
+			/* Cannot read from anywhere - mark it bad */
+			struct md_rdev *rdev = conf->mirrors[read_disk].rdev;
+			if (!rdev_set_badblocks(rdev, sect, s, 0))
+				md_error(mddev, rdev);
+			break;
+		}
+		/* write it back and re-read */
+		start = d;
+		while (d != read_disk) {
+			if (d==0)
+				d = conf->raid_disks * 2;
+			d--;
+			rdev = conf->mirrors[d].rdev;
+			if (rdev &&
+			    !test_bit(Faulty, &rdev->flags))
+				r1_sync_page_io(rdev, sect, s,
+						conf->tmppage, WRITE);
+		}
+		d = start;
+		while (d != read_disk) {
+			char b[BDEVNAME_SIZE];
+			if (d==0)
+				d = conf->raid_disks * 2;
+			d--;
+			rdev = conf->mirrors[d].rdev;
+			if (rdev &&
+			    !test_bit(Faulty, &rdev->flags)) {
+				if (r1_sync_page_io(rdev, sect, s,
+						    conf->tmppage, READ)) {
+					atomic_add(s, &rdev->corrected_errors);
+					printk(KERN_INFO
+					       "md/raid1:%s: read error corrected "
+					       "(%d sectors at %llu on %s)\n",
+					       mdname(mddev), s,
+					       (unsigned long long)(sect +
+					           rdev->data_offset),
+					       bdevname(rdev->bdev, b));
+				}
+			}
+		}
+		sectors -= s;
+		sect += s;
+	}
+}
+
+static int narrow_write_error(struct r1bio *r1_bio, int i)
+{
+	struct mddev *mddev = r1_bio->mddev;
+	struct r1conf *conf = mddev->private;
+	struct md_rdev *rdev = conf->mirrors[i].rdev;
+
+	/* bio has the data to be written to device 'i' where
+	 * we just recently had a write error.
+	 * We repeatedly clone the bio and trim down to one block,
+	 * then try the write.  Where the write fails we record
+	 * a bad block.
+	 * It is conceivable that the bio doesn't exactly align with
+	 * blocks.  We must handle this somehow.
+	 *
+	 * We currently own a reference on the rdev.
+	 */
+
+	int block_sectors;
+	sector_t sector;
+	int sectors;
+	int sect_to_write = r1_bio->sectors;
+	int ok = 1;
+
+	if (rdev->badblocks.shift < 0)
+		return 0;
+
+	block_sectors = roundup(1 << rdev->badblocks.shift,
+				bdev_logical_block_size(rdev->bdev) >> 9);
+	sector = r1_bio->sector;
+	sectors = ((sector + block_sectors)
+		   & ~(sector_t)(block_sectors - 1))
+		- sector;
+
+	while (sect_to_write) {
+		struct bio *wbio;
+		if (sectors > sect_to_write)
+			sectors = sect_to_write;
+		/* Write at 'sector' for 'sectors'*/
+
+		if (test_bit(R1BIO_BehindIO, &r1_bio->state)) {
+			unsigned vcnt = r1_bio->behind_page_count;
+			struct bio_vec *vec = r1_bio->behind_bvecs;
+
+			while (!vec->bv_page) {
+				vec++;
+				vcnt--;
+			}
+
+			wbio = bio_alloc_mddev(GFP_NOIO, vcnt, mddev);
+			memcpy(wbio->bi_io_vec, vec, vcnt * sizeof(struct bio_vec));
+
+			wbio->bi_vcnt = vcnt;
+		} else {
+			wbio = bio_clone_mddev(r1_bio->master_bio, GFP_NOIO, mddev);
+		}
+
+		wbio->bi_rw = WRITE;
+		wbio->bi_iter.bi_sector = r1_bio->sector;
+		wbio->bi_iter.bi_size = r1_bio->sectors << 9;
+
+		bio_trim(wbio, sector - r1_bio->sector, sectors);
+		wbio->bi_iter.bi_sector += rdev->data_offset;
+		wbio->bi_bdev = rdev->bdev;
+		if (submit_bio_wait(WRITE, wbio) < 0)
+			/* failure! */
+			ok = rdev_set_badblocks(rdev, sector,
+						sectors, 0)
+				&& ok;
+
+		bio_put(wbio);
+		sect_to_write -= sectors;
+		sector += sectors;
+		sectors = block_sectors;
+	}
+	return ok;
+}
+
+static void handle_sync_write_finished(struct r1conf *conf, struct r1bio *r1_bio)
+{
+	int m;
+	int s = r1_bio->sectors;
+	for (m = 0; m < conf->raid_disks * 2 ; m++) {
+		struct md_rdev *rdev = conf->mirrors[m].rdev;
+		struct bio *bio = r1_bio->bios[m];
+		if (bio->bi_end_io == NULL)
+			continue;
+		if (!bio->bi_error &&
+		    test_bit(R1BIO_MadeGood, &r1_bio->state)) {
+			rdev_clear_badblocks(rdev, r1_bio->sector, s, 0);
+		}
+		if (bio->bi_error &&
+		    test_bit(R1BIO_WriteError, &r1_bio->state)) {
+			if (!rdev_set_badblocks(rdev, r1_bio->sector, s, 0))
+				md_error(conf->mddev, rdev);
+		}
+	}
+	put_buf(r1_bio);
+	md_done_sync(conf->mddev, s, 1);
+}
+
+static void handle_write_finished(struct r1conf *conf, struct r1bio *r1_bio)
+{
+	int m;
+	bool fail = false;
+	for (m = 0; m < conf->raid_disks * 2 ; m++)
+		if (r1_bio->bios[m] == IO_MADE_GOOD) {
+			struct md_rdev *rdev = conf->mirrors[m].rdev;
+			rdev_clear_badblocks(rdev,
+					     r1_bio->sector,
+					     r1_bio->sectors, 0);
+			rdev_dec_pending(rdev, conf->mddev);
+		} else if (r1_bio->bios[m] != NULL) {
+			/* This drive got a write error.  We need to
+			 * narrow down and record precise write
+			 * errors.
+			 */
+			fail = true;
+			if (!narrow_write_error(r1_bio, m)) {
+				md_error(conf->mddev,
+					 conf->mirrors[m].rdev);
+				/* an I/O failed, we can't clear the bitmap */
+				set_bit(R1BIO_Degraded, &r1_bio->state);
+			}
+			rdev_dec_pending(conf->mirrors[m].rdev,
+					 conf->mddev);
+		}
+	if (fail) {
+		spin_lock_irq(&conf->device_lock);
+		list_add(&r1_bio->retry_list, &conf->bio_end_io_list);
+		conf->nr_queued++;
+		spin_unlock_irq(&conf->device_lock);
+		md_wakeup_thread(conf->mddev->thread);
+	} else {
+		if (test_bit(R1BIO_WriteError, &r1_bio->state))
+			close_write(r1_bio);
+		raid_end_bio_io(r1_bio);
+	}
+}
+
+static void handle_read_error(struct r1conf *conf, struct r1bio *r1_bio)
+{
+	int disk;
+	int max_sectors;
+	struct mddev *mddev = conf->mddev;
+	struct bio *bio;
+	char b[BDEVNAME_SIZE];
+	struct md_rdev *rdev;
+
+	clear_bit(R1BIO_ReadError, &r1_bio->state);
+	/* we got a read error. Maybe the drive is bad.  Maybe just
+	 * the block and we can fix it.
+	 * We freeze all other IO, and try reading the block from
+	 * other devices.  When we find one, we re-write
+	 * and check it that fixes the read error.
+	 * This is all done synchronously while the array is
+	 * frozen
+	 */
+	if (mddev->ro == 0) {
+		freeze_array(conf, 1);
+		fix_read_error(conf, r1_bio->read_disk,
+			       r1_bio->sector, r1_bio->sectors);
+		unfreeze_array(conf);
+	} else
+		md_error(mddev, conf->mirrors[r1_bio->read_disk].rdev);
+	rdev_dec_pending(conf->mirrors[r1_bio->read_disk].rdev, conf->mddev);
+
+	bio = r1_bio->bios[r1_bio->read_disk];
+	bdevname(bio->bi_bdev, b);
+read_more:
+	disk = read_balance(conf, r1_bio, &max_sectors);
+	if (disk == -1) {
+		printk(KERN_ALERT "md/raid1:%s: %s: unrecoverable I/O"
+		       " read error for block %llu\n",
+		       mdname(mddev), b, (unsigned long long)r1_bio->sector);
+		raid_end_bio_io(r1_bio);
+	} else {
+		const unsigned long do_sync
+			= r1_bio->master_bio->bi_rw & REQ_SYNC;
+		if (bio) {
+			r1_bio->bios[r1_bio->read_disk] =
+				mddev->ro ? IO_BLOCKED : NULL;
+			bio_put(bio);
+		}
+		r1_bio->read_disk = disk;
+		bio = bio_clone_mddev(r1_bio->master_bio, GFP_NOIO, mddev);
+		bio_trim(bio, r1_bio->sector - bio->bi_iter.bi_sector,
+			 max_sectors);
+		r1_bio->bios[r1_bio->read_disk] = bio;
+		rdev = conf->mirrors[disk].rdev;
+		printk_ratelimited(KERN_ERR
+				   "md/raid1:%s: redirecting sector %llu"
+				   " to other mirror: %s\n",
+				   mdname(mddev),
+				   (unsigned long long)r1_bio->sector,
+				   bdevname(rdev->bdev, b));
+		bio->bi_iter.bi_sector = r1_bio->sector + rdev->data_offset;
+		bio->bi_bdev = rdev->bdev;
+		bio->bi_end_io = raid1_end_read_request;
+		bio->bi_rw = READ | do_sync;
+		bio->bi_private = r1_bio;
+		if (max_sectors < r1_bio->sectors) {
+			/* Drat - have to split this up more */
+			struct bio *mbio = r1_bio->master_bio;
+			int sectors_handled = (r1_bio->sector + max_sectors
+					       - mbio->bi_iter.bi_sector);
+			r1_bio->sectors = max_sectors;
+			spin_lock_irq(&conf->device_lock);
+			if (mbio->bi_phys_segments == 0)
+				mbio->bi_phys_segments = 2;
+			else
+				mbio->bi_phys_segments++;
+			spin_unlock_irq(&conf->device_lock);
+			generic_make_request(bio);
+			bio = NULL;
+
+			r1_bio = mempool_alloc(conf->r1bio_pool, GFP_NOIO);
+
+			r1_bio->master_bio = mbio;
+			r1_bio->sectors = bio_sectors(mbio) - sectors_handled;
+			r1_bio->state = 0;
+			set_bit(R1BIO_ReadError, &r1_bio->state);
+			r1_bio->mddev = mddev;
+			r1_bio->sector = mbio->bi_iter.bi_sector +
+				sectors_handled;
+
+			goto read_more;
+		} else
+			generic_make_request(bio);
+	}
+}
+
+static void raid1d(struct md_thread *thread)
+{
+	struct mddev *mddev = thread->mddev;
+	struct r1bio *r1_bio;
+	unsigned long flags;
+	struct r1conf *conf = mddev->private;
+	struct list_head *head = &conf->retry_list;
+	struct blk_plug plug;
+
+	md_check_recovery(mddev);
+
+	if (!list_empty_careful(&conf->bio_end_io_list) &&
+	    !test_bit(MD_CHANGE_PENDING, &mddev->flags)) {
+		LIST_HEAD(tmp);
+		spin_lock_irqsave(&conf->device_lock, flags);
+		if (!test_bit(MD_CHANGE_PENDING, &mddev->flags)) {
+			while (!list_empty(&conf->bio_end_io_list)) {
+				list_move(conf->bio_end_io_list.prev, &tmp);
+				conf->nr_queued--;
+			}
+		}
+		spin_unlock_irqrestore(&conf->device_lock, flags);
+		while (!list_empty(&tmp)) {
+			r1_bio = list_first_entry(&tmp, struct r1bio,
+						  retry_list);
+			list_del(&r1_bio->retry_list);
+			if (mddev->degraded)
+				set_bit(R1BIO_Degraded, &r1_bio->state);
+			if (test_bit(R1BIO_WriteError, &r1_bio->state))
+				close_write(r1_bio);
+			raid_end_bio_io(r1_bio);
+		}
+	}
+
+	blk_start_plug(&plug);
+	for (;;) {
+
+		flush_pending_writes(conf);
+
+		spin_lock_irqsave(&conf->device_lock, flags);
+		if (list_empty(head)) {
+			spin_unlock_irqrestore(&conf->device_lock, flags);
+			break;
+		}
+		r1_bio = list_entry(head->prev, struct r1bio, retry_list);
+		list_del(head->prev);
+		conf->nr_queued--;
+		spin_unlock_irqrestore(&conf->device_lock, flags);
+
+		mddev = r1_bio->mddev;
+		conf = mddev->private;
+		if (test_bit(R1BIO_IsSync, &r1_bio->state)) {
+			if (test_bit(R1BIO_MadeGood, &r1_bio->state) ||
+			    test_bit(R1BIO_WriteError, &r1_bio->state))
+				handle_sync_write_finished(conf, r1_bio);
+			else
+				sync_request_write(mddev, r1_bio);
+		} else if (test_bit(R1BIO_MadeGood, &r1_bio->state) ||
+			   test_bit(R1BIO_WriteError, &r1_bio->state))
+			handle_write_finished(conf, r1_bio);
+		else if (test_bit(R1BIO_ReadError, &r1_bio->state))
+			handle_read_error(conf, r1_bio);
+		else
+			/* just a partial read to be scheduled from separate
+			 * context
+			 */
+			generic_make_request(r1_bio->bios[r1_bio->read_disk]);
+
+		cond_resched();
+		if (mddev->flags & ~(1<<MD_CHANGE_PENDING))
+			md_check_recovery(mddev);
+	}
+	blk_finish_plug(&plug);
+}
+
+static int init_resync(struct r1conf *conf)
+{
+	int buffs;
+
+	buffs = RESYNC_WINDOW / RESYNC_BLOCK_SIZE;
+	BUG_ON(conf->r1buf_pool);
+	conf->r1buf_pool = mempool_create(buffs, r1buf_pool_alloc, r1buf_pool_free,
+					  conf->poolinfo);
+	if (!conf->r1buf_pool)
+		return -ENOMEM;
+	conf->next_resync = 0;
+	return 0;
+}
+
+/*
+ * perform a "sync" on one "block"
+ *
+ * We need to make sure that no normal I/O request - particularly write
+ * requests - conflict with active sync requests.
+ *
+ * This is achieved by tracking pending requests and a 'barrier' concept
+ * that can be installed to exclude normal IO requests.
+ */
+
+static sector_t sync_request(struct mddev *mddev, sector_t sector_nr, int *skipped)
+{
+	struct r1conf *conf = mddev->private;
+	struct r1bio *r1_bio;
+	struct bio *bio;
+	sector_t max_sector, nr_sectors;
+	int disk = -1;
+	int i;
+	int wonly = -1;
+	int write_targets = 0, read_targets = 0;
+	sector_t sync_blocks;
+	int still_degraded = 0;
+	int good_sectors = RESYNC_SECTORS;
+	int min_bad = 0; /* number of sectors that are bad in all devices */
+
+	if (!conf->r1buf_pool)
+		if (init_resync(conf))
+			return 0;
+
+	max_sector = mddev->dev_sectors;
+	if (sector_nr >= max_sector) {
+		/* If we aborted, we need to abort the
+		 * sync on the 'current' bitmap chunk (there will
+		 * only be one in raid1 resync.
+		 * We can find the current addess in mddev->curr_resync
+		 */
+		if (mddev->curr_resync < max_sector) /* aborted */
+			bitmap_end_sync(mddev->bitmap, mddev->curr_resync,
+						&sync_blocks, 1);
+		else /* completed sync */
+			conf->fullsync = 0;
+
+		bitmap_close_sync(mddev->bitmap);
+		close_sync(conf);
+
+		if (mddev_is_clustered(mddev)) {
+			conf->cluster_sync_low = 0;
+			conf->cluster_sync_high = 0;
+		}
+		return 0;
+	}
+
+	if (mddev->bitmap == NULL &&
+	    mddev->recovery_cp == MaxSector &&
+	    !test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery) &&
+	    conf->fullsync == 0) {
+		*skipped = 1;
+		return max_sector - sector_nr;
+	}
+	/* before building a request, check if we can skip these blocks..
+	 * This call the bitmap_start_sync doesn't actually record anything
+	 */
+	if (!bitmap_start_sync(mddev->bitmap, sector_nr, &sync_blocks, 1) &&
+	    !conf->fullsync && !test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery)) {
+		/* We can skip this block, and probably several more */
+		*skipped = 1;
+		return sync_blocks;
+	}
+
+	/* we are incrementing sector_nr below. To be safe, we check against
+	 * sector_nr + two times RESYNC_SECTORS
+	 */
+
+	bitmap_cond_end_sync(mddev->bitmap, sector_nr,
+		mddev_is_clustered(mddev) && (sector_nr + 2 * RESYNC_SECTORS > conf->cluster_sync_high));
+	r1_bio = mempool_alloc(conf->r1buf_pool, GFP_NOIO);
+
+	raise_barrier(conf, sector_nr);
+
+	rcu_read_lock();
+	/*
+	 * If we get a correctably read error during resync or recovery,
+	 * we might want to read from a different device.  So we
+	 * flag all drives that could conceivably be read from for READ,
+	 * and any others (which will be non-In_sync devices) for WRITE.
+	 * If a read fails, we try reading from something else for which READ
+	 * is OK.
+	 */
+
+	r1_bio->mddev = mddev;
+	r1_bio->sector = sector_nr;
+	r1_bio->state = 0;
+	set_bit(R1BIO_IsSync, &r1_bio->state);
+
+	for (i = 0; i < conf->raid_disks * 2; i++) {
+		struct md_rdev *rdev;
+		bio = r1_bio->bios[i];
+		bio_reset(bio);
+
+		rdev = rcu_dereference(conf->mirrors[i].rdev);
+		if (rdev == NULL ||
+		    test_bit(Faulty, &rdev->flags)) {
+			if (i < conf->raid_disks)
+				still_degraded = 1;
+		} else if (!test_bit(In_sync, &rdev->flags)) {
+			bio->bi_rw = WRITE;
+			bio->bi_end_io = end_sync_write;
+			write_targets ++;
+		} else {
+			/* may need to read from here */
+			sector_t first_bad = MaxSector;
+			int bad_sectors;
+
+			if (is_badblock(rdev, sector_nr, good_sectors,
+					&first_bad, &bad_sectors)) {
+				if (first_bad > sector_nr)
+					good_sectors = first_bad - sector_nr;
+				else {
+					bad_sectors -= (sector_nr - first_bad);
+					if (min_bad == 0 ||
+					    min_bad > bad_sectors)
+						min_bad = bad_sectors;
+				}
+			}
+			if (sector_nr < first_bad) {
+				if (test_bit(WriteMostly, &rdev->flags)) {
+					if (wonly < 0)
+						wonly = i;
+				} else {
+					if (disk < 0)
+						disk = i;
+				}
+				bio->bi_rw = READ;
+				bio->bi_end_io = end_sync_read;
+				read_targets++;
+			} else if (!test_bit(WriteErrorSeen, &rdev->flags) &&
+				test_bit(MD_RECOVERY_SYNC, &mddev->recovery) &&
+				!test_bit(MD_RECOVERY_CHECK, &mddev->recovery)) {
+				/*
+				 * The device is suitable for reading (InSync),
+				 * but has bad block(s) here. Let's try to correct them,
+				 * if we are doing resync or repair. Otherwise, leave
+				 * this device alone for this sync request.
+				 */
+				bio->bi_rw = WRITE;
+				bio->bi_end_io = end_sync_write;
+				write_targets++;
+			}
+		}
+		if (bio->bi_end_io) {
+			atomic_inc(&rdev->nr_pending);
+			bio->bi_iter.bi_sector = sector_nr + rdev->data_offset;
+			bio->bi_bdev = rdev->bdev;
+			bio->bi_private = r1_bio;
+		}
+	}
+	rcu_read_unlock();
+	if (disk < 0)
+		disk = wonly;
+	r1_bio->read_disk = disk;
+
+	if (read_targets == 0 && min_bad > 0) {
+		/* These sectors are bad on all InSync devices, so we
+		 * need to mark them bad on all write targets
+		 */
+		int ok = 1;
+		for (i = 0 ; i < conf->raid_disks * 2 ; i++)
+			if (r1_bio->bios[i]->bi_end_io == end_sync_write) {
+				struct md_rdev *rdev = conf->mirrors[i].rdev;
+				ok = rdev_set_badblocks(rdev, sector_nr,
+							min_bad, 0
+					) && ok;
+			}
+		set_bit(MD_CHANGE_DEVS, &mddev->flags);
+		*skipped = 1;
+		put_buf(r1_bio);
+
+		if (!ok) {
+			/* Cannot record the badblocks, so need to
+			 * abort the resync.
+			 * If there are multiple read targets, could just
+			 * fail the really bad ones ???
+			 */
+			conf->recovery_disabled = mddev->recovery_disabled;
+			set_bit(MD_RECOVERY_INTR, &mddev->recovery);
+			return 0;
+		} else
+			return min_bad;
+
+	}
+	if (min_bad > 0 && min_bad < good_sectors) {
+		/* only resync enough to reach the next bad->good
+		 * transition */
+		good_sectors = min_bad;
+	}
+
+	if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery) && read_targets > 0)
+		/* extra read targets are also write targets */
+		write_targets += read_targets-1;
+
+	if (write_targets == 0 || read_targets == 0) {
+		/* There is nowhere to write, so all non-sync
+		 * drives must be failed - so we are finished
+		 */
+		sector_t rv;
+		if (min_bad > 0)
+			max_sector = sector_nr + min_bad;
+		rv = max_sector - sector_nr;
+		*skipped = 1;
+		put_buf(r1_bio);
+		return rv;
+	}
+
+	if (max_sector > mddev->resync_max)
+		max_sector = mddev->resync_max; /* Don't do IO beyond here */
+	if (max_sector > sector_nr + good_sectors)
+		max_sector = sector_nr + good_sectors;
+	nr_sectors = 0;
+	sync_blocks = 0;
+	do {
+		struct page *page;
+		int len = PAGE_SIZE;
+		if (sector_nr + (len>>9) > max_sector)
+			len = (max_sector - sector_nr) << 9;
+		if (len == 0)
+			break;
+		if (sync_blocks == 0) {
+			if (!bitmap_start_sync(mddev->bitmap, sector_nr,
+					       &sync_blocks, still_degraded) &&
+			    !conf->fullsync &&
+			    !test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery))
+				break;
+			BUG_ON(sync_blocks < (PAGE_SIZE>>9));
+			if ((len >> 9) > sync_blocks)
+				len = sync_blocks<<9;
+		}
+
+		for (i = 0 ; i < conf->raid_disks * 2; i++) {
+			bio = r1_bio->bios[i];
+			if (bio->bi_end_io) {
+				page = bio->bi_io_vec[bio->bi_vcnt].bv_page;
+				if (bio_add_page(bio, page, len, 0) == 0) {
+					/* stop here */
+					bio->bi_io_vec[bio->bi_vcnt].bv_page = page;
+					while (i > 0) {
+						i--;
+						bio = r1_bio->bios[i];
+						if (bio->bi_end_io==NULL)
+							continue;
+						/* remove last page from this bio */
+						bio->bi_vcnt--;
+						bio->bi_iter.bi_size -= len;
+						bio_clear_flag(bio, BIO_SEG_VALID);
+					}
+					goto bio_full;
+				}
+			}
+		}
+		nr_sectors += len>>9;
+		sector_nr += len>>9;
+		sync_blocks -= (len>>9);
+	} while (r1_bio->bios[disk]->bi_vcnt < RESYNC_PAGES);
+ bio_full:
+	r1_bio->sectors = nr_sectors;
+
+	if (mddev_is_clustered(mddev) &&
+			conf->cluster_sync_high < sector_nr + nr_sectors) {
+		conf->cluster_sync_low = mddev->curr_resync_completed;
+		conf->cluster_sync_high = conf->cluster_sync_low + CLUSTER_RESYNC_WINDOW_SECTORS;
+		/* Send resync message */
+		md_cluster_ops->resync_info_update(mddev,
+				conf->cluster_sync_low,
+				conf->cluster_sync_high);
+	}
+
+	/* For a user-requested sync, we read all readable devices and do a
+	 * compare
+	 */
+	if (test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery)) {
+		atomic_set(&r1_bio->remaining, read_targets);
+		for (i = 0; i < conf->raid_disks * 2 && read_targets; i++) {
+			bio = r1_bio->bios[i];
+			if (bio->bi_end_io == end_sync_read) {
+				read_targets--;
+				md_sync_acct(bio->bi_bdev, nr_sectors);
+				generic_make_request(bio);
+			}
+		}
+	} else {
+		atomic_set(&r1_bio->remaining, 1);
+		bio = r1_bio->bios[r1_bio->read_disk];
+		md_sync_acct(bio->bi_bdev, nr_sectors);
+		generic_make_request(bio);
+
+	}
+	return nr_sectors;
+}
+
+static sector_t raid1_size(struct mddev *mddev, sector_t sectors, int raid_disks)
+{
+	if (sectors)
+		return sectors;
+
+	return mddev->dev_sectors;
+}
+
+static struct r1conf *setup_conf(struct mddev *mddev)
+{
+	struct r1conf *conf;
+	int i;
+	struct raid1_info *disk;
+	struct md_rdev *rdev;
+	int err = -ENOMEM;
+
+	conf = kzalloc(sizeof(struct r1conf), GFP_KERNEL);
+	if (!conf)
+		goto abort;
+
+	conf->mirrors = kzalloc(sizeof(struct raid1_info)
+				* mddev->raid_disks * 2,
+				 GFP_KERNEL);
+	if (!conf->mirrors)
+		goto abort;
+
+	conf->tmppage = alloc_page(GFP_KERNEL);
+	if (!conf->tmppage)
+		goto abort;
+
+	conf->poolinfo = kzalloc(sizeof(*conf->poolinfo), GFP_KERNEL);
+	if (!conf->poolinfo)
+		goto abort;
+	conf->poolinfo->raid_disks = mddev->raid_disks * 2;
+	conf->r1bio_pool = mempool_create(NR_RAID1_BIOS, r1bio_pool_alloc,
+					  r1bio_pool_free,
+					  conf->poolinfo);
+	if (!conf->r1bio_pool)
+		goto abort;
+
+	conf->poolinfo->mddev = mddev;
+
+	err = -EINVAL;
+	spin_lock_init(&conf->device_lock);
+	rdev_for_each(rdev, mddev) {
+		struct request_queue *q;
+		int disk_idx = rdev->raid_disk;
+		if (disk_idx >= mddev->raid_disks
+		    || disk_idx < 0)
+			continue;
+		if (test_bit(Replacement, &rdev->flags))
+			disk = conf->mirrors + mddev->raid_disks + disk_idx;
+		else
+			disk = conf->mirrors + disk_idx;
+
+		if (disk->rdev)
+			goto abort;
+		disk->rdev = rdev;
+		q = bdev_get_queue(rdev->bdev);
+
+		disk->head_position = 0;
+		disk->seq_start = MaxSector;
+	}
+	conf->raid_disks = mddev->raid_disks;
+	conf->mddev = mddev;
+	INIT_LIST_HEAD(&conf->retry_list);
+	INIT_LIST_HEAD(&conf->bio_end_io_list);
+
+	spin_lock_init(&conf->resync_lock);
+	init_waitqueue_head(&conf->wait_barrier);
+
+	bio_list_init(&conf->pending_bio_list);
+	conf->pending_count = 0;
+	conf->recovery_disabled = mddev->recovery_disabled - 1;
+
+	conf->start_next_window = MaxSector;
+	conf->current_window_requests = conf->next_window_requests = 0;
+
+	err = -EIO;
+	for (i = 0; i < conf->raid_disks * 2; i++) {
+
+		disk = conf->mirrors + i;
+
+		if (i < conf->raid_disks &&
+		    disk[conf->raid_disks].rdev) {
+			/* This slot has a replacement. */
+			if (!disk->rdev) {
+				/* No original, just make the replacement
+				 * a recovering spare
+				 */
+				disk->rdev =
+					disk[conf->raid_disks].rdev;
+				disk[conf->raid_disks].rdev = NULL;
+			} else if (!test_bit(In_sync, &disk->rdev->flags))
+				/* Original is not in_sync - bad */
+				goto abort;
+		}
+
+		if (!disk->rdev ||
+		    !test_bit(In_sync, &disk->rdev->flags)) {
+			disk->head_position = 0;
+			if (disk->rdev &&
+			    (disk->rdev->saved_raid_disk < 0))
+				conf->fullsync = 1;
+		}
+	}
+
+	err = -ENOMEM;
+	conf->thread = md_register_thread(raid1d, mddev, "raid1");
+	if (!conf->thread) {
+		printk(KERN_ERR
+		       "md/raid1:%s: couldn't allocate thread\n",
+		       mdname(mddev));
+		goto abort;
+	}
+
+	return conf;
+
+ abort:
+	if (conf) {
+		mempool_destroy(conf->r1bio_pool);
+		kfree(conf->mirrors);
+		safe_put_page(conf->tmppage);
+		kfree(conf->poolinfo);
+		kfree(conf);
+	}
+	return ERR_PTR(err);
+}
+
+static void raid1_free(struct mddev *mddev, void *priv);
+static int run(struct mddev *mddev)
+{
+	struct r1conf *conf;
+	int i;
+	struct md_rdev *rdev;
+	int ret;
+	bool discard_supported = false;
+
+	if (mddev->level != 1) {
+		printk(KERN_ERR "md/raid1:%s: raid level not set to mirroring (%d)\n",
+		       mdname(mddev), mddev->level);
+		return -EIO;
+	}
+	if (mddev->reshape_position != MaxSector) {
+		printk(KERN_ERR "md/raid1:%s: reshape_position set but not supported\n",
+		       mdname(mddev));
+		return -EIO;
+	}
+	/*
+	 * copy the already verified devices into our private RAID1
+	 * bookkeeping area. [whatever we allocate in run(),
+	 * should be freed in raid1_free()]
+	 */
+	if (mddev->private == NULL)
+		conf = setup_conf(mddev);
+	else
+		conf = mddev->private;
+
+	if (IS_ERR(conf))
+		return PTR_ERR(conf);
+
+	if (mddev->queue)
+		blk_queue_max_write_same_sectors(mddev->queue, 0);
+
+	rdev_for_each(rdev, mddev) {
+		if (!mddev->gendisk)
+			continue;
+		disk_stack_limits(mddev->gendisk, rdev->bdev,
+				  rdev->data_offset << 9);
+		if (blk_queue_discard(bdev_get_queue(rdev->bdev)))
+			discard_supported = true;
+	}
+
+	mddev->degraded = 0;
+	for (i=0; i < conf->raid_disks; i++)
+		if (conf->mirrors[i].rdev == NULL ||
+		    !test_bit(In_sync, &conf->mirrors[i].rdev->flags) ||
+		    test_bit(Faulty, &conf->mirrors[i].rdev->flags))
+			mddev->degraded++;
+
+	if (conf->raid_disks - mddev->degraded == 1)
+		mddev->recovery_cp = MaxSector;
+
+	if (mddev->recovery_cp != MaxSector)
+		printk(KERN_NOTICE "md/raid1:%s: not clean"
+		       " -- starting background reconstruction\n",
+		       mdname(mddev));
+	printk(KERN_INFO
+		"md/raid1:%s: active with %d out of %d mirrors\n",
+		mdname(mddev), mddev->raid_disks - mddev->degraded,
+		mddev->raid_disks);
+
+	/*
+	 * Ok, everything is just fine now
+	 */
+	mddev->thread = conf->thread;
+	conf->thread = NULL;
+	mddev->private = conf;
+
+	md_set_array_sectors(mddev, raid1_size(mddev, 0, 0));
+
+	if (mddev->queue) {
+		if (discard_supported)
+			queue_flag_set_unlocked(QUEUE_FLAG_DISCARD,
+						mddev->queue);
+		else
+			queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD,
+						  mddev->queue);
+	}
+
+	ret =  md_integrity_register(mddev);
+	if (ret) {
+		md_unregister_thread(&mddev->thread);
+		raid1_free(mddev, conf);
+	}
+	return ret;
+}
+
+static void raid1_free(struct mddev *mddev, void *priv)
+{
+	struct r1conf *conf = priv;
+
+	mempool_destroy(conf->r1bio_pool);
+	kfree(conf->mirrors);
+	safe_put_page(conf->tmppage);
+	kfree(conf->poolinfo);
+	kfree(conf);
+}
+
+static int raid1_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 = raid1_size(mddev, sectors, 0);
+	if (mddev->external_size &&
+	    mddev->array_sectors > newsize)
+		return -EINVAL;
+	if (mddev->bitmap) {
+		int ret = bitmap_resize(mddev->bitmap, newsize, 0, 0);
+		if (ret)
+			return ret;
+	}
+	md_set_array_sectors(mddev, newsize);
+	set_capacity(mddev->gendisk, mddev->array_sectors);
+	revalidate_disk(mddev->gendisk);
+	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 raid1_reshape(struct mddev *mddev)
+{
+	/* We need to:
+	 * 1/ resize the r1bio_pool
+	 * 2/ resize conf->mirrors
+	 *
+	 * We allocate a new r1bio_pool if we can.
+	 * Then raise a device barrier and wait until all IO stops.
+	 * Then resize conf->mirrors and swap in the new r1bio pool.
+	 *
+	 * At the same time, we "pack" the devices so that all the missing
+	 * devices have the higher raid_disk numbers.
+	 */
+	mempool_t *newpool, *oldpool;
+	struct pool_info *newpoolinfo;
+	struct raid1_info *newmirrors;
+	struct r1conf *conf = mddev->private;
+	int cnt, raid_disks;
+	unsigned long flags;
+	int d, d2, err;
+
+	/* Cannot change chunk_size, layout, or level */
+	if (mddev->chunk_sectors != mddev->new_chunk_sectors ||
+	    mddev->layout != mddev->new_layout ||
+	    mddev->level != mddev->new_level) {
+		mddev->new_chunk_sectors = mddev->chunk_sectors;
+		mddev->new_layout = mddev->layout;
+		mddev->new_level = mddev->level;
+		return -EINVAL;
+	}
+
+	if (!mddev_is_clustered(mddev)) {
+		err = md_allow_write(mddev);
+		if (err)
+			return err;
+	}
+
+	raid_disks = mddev->raid_disks + mddev->delta_disks;
+
+	if (raid_disks < conf->raid_disks) {
+		cnt=0;
+		for (d= 0; d < conf->raid_disks; d++)
+			if (conf->mirrors[d].rdev)
+				cnt++;
+		if (cnt > raid_disks)
+			return -EBUSY;
+	}
+
+	newpoolinfo = kmalloc(sizeof(*newpoolinfo), GFP_KERNEL);
+	if (!newpoolinfo)
+		return -ENOMEM;
+	newpoolinfo->mddev = mddev;
+	newpoolinfo->raid_disks = raid_disks * 2;
+
+	newpool = mempool_create(NR_RAID1_BIOS, r1bio_pool_alloc,
+				 r1bio_pool_free, newpoolinfo);
+	if (!newpool) {
+		kfree(newpoolinfo);
+		return -ENOMEM;
+	}
+	newmirrors = kzalloc(sizeof(struct raid1_info) * raid_disks * 2,
+			     GFP_KERNEL);
+	if (!newmirrors) {
+		kfree(newpoolinfo);
+		mempool_destroy(newpool);
+		return -ENOMEM;
+	}
+
+	freeze_array(conf, 0);
+
+	/* ok, everything is stopped */
+	oldpool = conf->r1bio_pool;
+	conf->r1bio_pool = newpool;
+
+	for (d = d2 = 0; d < conf->raid_disks; d++) {
+		struct md_rdev *rdev = conf->mirrors[d].rdev;
+		if (rdev && rdev->raid_disk != d2) {
+			sysfs_unlink_rdev(mddev, rdev);
+			rdev->raid_disk = d2;
+			sysfs_unlink_rdev(mddev, rdev);
+			if (sysfs_link_rdev(mddev, rdev))
+				printk(KERN_WARNING
+				       "md/raid1:%s: cannot register rd%d\n",
+				       mdname(mddev), rdev->raid_disk);
+		}
+		if (rdev)
+			newmirrors[d2++].rdev = rdev;
+	}
+	kfree(conf->mirrors);
+	conf->mirrors = newmirrors;
+	kfree(conf->poolinfo);
+	conf->poolinfo = newpoolinfo;
+
+	spin_lock_irqsave(&conf->device_lock, flags);
+	mddev->degraded += (raid_disks - conf->raid_disks);
+	spin_unlock_irqrestore(&conf->device_lock, flags);
+	conf->raid_disks = mddev->raid_disks = raid_disks;
+	mddev->delta_disks = 0;
+
+	unfreeze_array(conf);
+
+	set_bit(MD_RECOVERY_RECOVER, &mddev->recovery);
+	set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
+	md_wakeup_thread(mddev->thread);
+
+	mempool_destroy(oldpool);
+	return 0;
+}
+
+static void raid1_quiesce(struct mddev *mddev, int state)
+{
+	struct r1conf *conf = mddev->private;
+
+	switch(state) {
+	case 2: /* wake for suspend */
+		wake_up(&conf->wait_barrier);
+		break;
+	case 1:
+		freeze_array(conf, 0);
+		break;
+	case 0:
+		unfreeze_array(conf);
+		break;
+	}
+}
+
+static void *raid1_takeover(struct mddev *mddev)
+{
+	/* raid1 can take over:
+	 *  raid5 with 2 devices, any layout or chunk size
+	 */
+	if (mddev->level == 5 && mddev->raid_disks == 2) {
+		struct r1conf *conf;
+		mddev->new_level = 1;
+		mddev->new_layout = 0;
+		mddev->new_chunk_sectors = 0;
+		conf = setup_conf(mddev);
+		if (!IS_ERR(conf))
+			/* Array must appear to be quiesced */
+			conf->array_frozen = 1;
+		return conf;
+	}
+	return ERR_PTR(-EINVAL);
+}
+
+static struct md_personality raid1_personality =
+{
+	.name		= "raid1",
+	.level		= 1,
+	.owner		= THIS_MODULE,
+	.make_request	= make_request,
+	.run		= run,
+	.free		= raid1_free,
+	.status		= status,
+	.error_handler	= error,
+	.hot_add_disk	= raid1_add_disk,
+	.hot_remove_disk= raid1_remove_disk,
+	.spare_active	= raid1_spare_active,
+	.sync_request	= sync_request,
+	.resize		= raid1_resize,
+	.size		= raid1_size,
+	.check_reshape	= raid1_reshape,
+	.quiesce	= raid1_quiesce,
+	.takeover	= raid1_takeover,
+	.congested	= raid1_congested,
+};
+
+static int __init raid_init(void)
+{
+	return register_md_personality(&raid1_personality);
+}
+
+static void raid_exit(void)
+{
+	unregister_md_personality(&raid1_personality);
+}
+
+module_init(raid_init);
+module_exit(raid_exit);
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("RAID1 (mirroring) personality for MD");
+MODULE_ALIAS("md-personality-3"); /* RAID1 */
+MODULE_ALIAS("md-raid1");
+MODULE_ALIAS("md-level-1");
+
+module_param(max_queued_requests, int, S_IRUGO|S_IWUSR);