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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * 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
  */
 
 #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 <linux/interval_tree_generic.h>
 
 #include <trace/events/block.h>
 
 #include "md.h"
 #include "raid1.h"
 #include "md-bitmap.h"
 
 #define UNSUPPORTED_MDDEV_FLAGS     \
     ((1L << MD_HAS_JOURNAL) |   \
      (1L << MD_JOURNAL_CLEAN) | \
      (1L << MD_HAS_PPL) |       \
      (1L << MD_HAS_MULTIPLE_PPLS))
 
 static void allow_barrier(struct r1conf *conf, sector_t sector_nr);
 static void lower_barrier(struct r1conf *conf, sector_t sector_nr);
 
 #define raid1_log(md, fmt, args...)             \
     do { if ((md)->queue) blk_add_trace_msg((md)->queue, "raid1 " fmt, ##args); } while (0)
 
 #include "raid1-10.c"
 
 #define START(node) ((node)->start)
 #define LAST(node) ((node)->last)
 INTERVAL_TREE_DEFINE(struct serial_info, node, sector_t, _subtree_last,
              START, LAST, static inline, raid1_rb);
 
 static int check_and_add_serial(struct md_rdev *rdev, struct r1bio *r1_bio,
                 struct serial_info *si, int idx)
 {
     unsigned long flags;
     int ret = 0;
     sector_t lo = r1_bio->sector;
     sector_t hi = lo + r1_bio->sectors;
     struct serial_in_rdev *serial = &rdev->serial[idx];
 
     spin_lock_irqsave(&serial->serial_lock, flags);
     /* collision happened */
     if (raid1_rb_iter_first(&serial->serial_rb, lo, hi))
         ret = -EBUSY;
     else {
         si->start = lo;
         si->last = hi;
         raid1_rb_insert(si, &serial->serial_rb);
     }
     spin_unlock_irqrestore(&serial->serial_lock, flags);
 
     return ret;
 }
 
 static void wait_for_serialization(struct md_rdev *rdev, struct r1bio *r1_bio)
 {
     struct mddev *mddev = rdev->mddev;
     struct serial_info *si;
     int idx = sector_to_idx(r1_bio->sector);
     struct serial_in_rdev *serial = &rdev->serial[idx];
 
     if (WARN_ON(!mddev->serial_info_pool))
         return;
     si = mempool_alloc(mddev->serial_info_pool, GFP_NOIO);
     wait_event(serial->serial_io_wait,
            check_and_add_serial(rdev, r1_bio, si, idx) == 0);
 }
 
 static void remove_serial(struct md_rdev *rdev, sector_t lo, sector_t hi)
 {
     struct serial_info *si;
     unsigned long flags;
     int found = 0;
     struct mddev *mddev = rdev->mddev;
     int idx = sector_to_idx(lo);
     struct serial_in_rdev *serial = &rdev->serial[idx];
 
     spin_lock_irqsave(&serial->serial_lock, flags);
     for (si = raid1_rb_iter_first(&serial->serial_rb, lo, hi);
          si; si = raid1_rb_iter_next(si, lo, hi)) {
         if (si->start == lo && si->last == hi) {
             raid1_rb_remove(si, &serial->serial_rb);
             mempool_free(si, mddev->serial_info_pool);
             found = 1;
             break;
         }
     }
     if (!found)
         WARN(1, "The write IO is not recorded for serialization\n");
     spin_unlock_irqrestore(&serial->serial_lock, flags);
     wake_up(&serial->serial_io_wait);
 }
 
 /*
  * for resync bio, r1bio pointer can be retrieved from the per-bio
  * 'struct resync_pages'.
  */
 static inline struct r1bio *get_resync_r1bio(struct bio *bio)
 {
     return get_resync_pages(bio)->raid_bio;
 }
 
 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);
 }
 
 #define RESYNC_DEPTH 32
 #define RESYNC_SECTORS (RESYNC_BLOCK_SIZE >> 9)
 #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)
 
 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 j;
     struct resync_pages *rps;
 
     r1_bio = r1bio_pool_alloc(gfp_flags, pi);
     if (!r1_bio)
         return NULL;
 
     rps = kmalloc_array(pi->raid_disks, sizeof(struct resync_pages),
                 gfp_flags);
     if (!rps)
         goto out_free_r1bio;
 
     /*
      * Allocate bios : 1 for reading, n-1 for writing
      */
     for (j = pi->raid_disks ; j-- ; ) {
         bio = bio_kmalloc(RESYNC_PAGES, gfp_flags);
         if (!bio)
             goto out_free_bio;
         bio_init(bio, NULL, bio->bi_inline_vecs, RESYNC_PAGES, 0);
         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 < pi->raid_disks; j++) {
         struct resync_pages *rp = &rps[j];
 
         bio = r1_bio->bios[j];
 
         if (j < need_pages) {
             if (resync_alloc_pages(rp, gfp_flags))
                 goto out_free_pages;
         } else {
             memcpy(rp, &rps[0], sizeof(*rp));
             resync_get_all_pages(rp);
         }
 
         rp->raid_bio = r1_bio;
         bio->bi_private = rp;
     }
 
     r1_bio->master_bio = NULL;
 
     return r1_bio;
 
 out_free_pages:
     while (--j >= 0)
         resync_free_pages(&rps[j]);
 
 out_free_bio:
     while (++j < pi->raid_disks) {
         bio_uninit(r1_bio->bios[j]);
         kfree(r1_bio->bios[j]);
     }
     kfree(rps);
 
 out_free_r1bio:
     rbio_pool_free(r1_bio, data);
     return NULL;
 }
 
 static void r1buf_pool_free(void *__r1_bio, void *data)
 {
     struct pool_info *pi = data;
     int i;
     struct r1bio *r1bio = __r1_bio;
     struct resync_pages *rp = NULL;
 
     for (i = pi->raid_disks; i--; ) {
         rp = get_resync_pages(r1bio->bios[i]);
         resync_free_pages(rp);
         bio_uninit(r1bio->bios[i]);
         kfree(r1bio->bios[i]);
     }
 
     /* resync pages array stored in the 1st bio's .bi_private */
     kfree(rp);
 
     rbio_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;
     sector_t sect = r1_bio->sector;
     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, sect);
 }
 
 static void reschedule_retry(struct r1bio *r1_bio)
 {
     unsigned long flags;
     struct mddev *mddev = r1_bio->mddev;
     struct r1conf *conf = mddev->private;
     int idx;
 
     idx = sector_to_idx(r1_bio->sector);
     spin_lock_irqsave(&conf->device_lock, flags);
     list_add(&r1_bio->retry_list, &conf->retry_list);
     atomic_inc(&conf->nr_queued[idx]);
     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;
 
     if (!test_bit(R1BIO_Uptodate, &r1_bio->state))
         bio->bi_status = BLK_STS_IOERR;
 
     if (blk_queue_io_stat(bio->bi_bdev->bd_disk->queue))
         bio_end_io_acct(bio, r1_bio->start_time);
     bio_endio(bio);
 }
 
 static void raid_end_bio_io(struct r1bio *r1_bio)
 {
     struct bio *bio = r1_bio->master_bio;
     struct r1conf *conf = r1_bio->mddev->private;
 
     /* 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);
     }
     /*
      * Wake up any possible resync thread that waits for the device
      * to go idle.  All I/Os, even write-behind writes, are done.
      */
     allow_barrier(conf, r1_bio->sector);
 
     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_status;
     struct r1bio *r1_bio = bio->bi_private;
     struct r1conf *conf = r1_bio->mddev->private;
     struct md_rdev *rdev = conf->mirrors[r1_bio->read_disk].rdev;
 
     /*
      * this branch is our 'one mirror IO has finished' event handler:
      */
     update_head_pos(r1_bio->read_disk, r1_bio);
 
     if (uptodate)
         set_bit(R1BIO_Uptodate, &r1_bio->state);
     else if (test_bit(FailFast, &rdev->flags) &&
          test_bit(R1BIO_FailFast, &r1_bio->state))
         /* This was a fail-fast read so we definitely
          * want to retry */
         ;
     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, &rdev->flags)))
             uptodate = 1;
         spin_unlock_irqrestore(&conf->device_lock, flags);
     }
 
     if (uptodate) {
         raid_end_bio_io(r1_bio);
         rdev_dec_pending(rdev, conf->mddev);
     } else {
         /*
          * oops, read error:
          */
         pr_err_ratelimited("md/raid1:%s: %pg: rescheduling sector %llu\n",
                    mdname(conf->mddev),
                    rdev->bdev,
                    (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)) {
         bio_free_pages(r1_bio->behind_master_bio);
         bio_put(r1_bio->behind_master_bio);
         r1_bio->behind_master_bio = NULL;
     }
     /* clear the bitmap if all writes complete successfully */
     md_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 behind = test_bit(R1BIO_BehindIO, &r1_bio->state);
     struct r1conf *conf = r1_bio->mddev->private;
     struct bio *to_put = NULL;
     int mirror = find_bio_disk(r1_bio, bio);
     struct md_rdev *rdev = conf->mirrors[mirror].rdev;
     bool discard_error;
     sector_t lo = r1_bio->sector;
     sector_t hi = r1_bio->sector + r1_bio->sectors;
 
     discard_error = bio->bi_status && bio_op(bio) == REQ_OP_DISCARD;
 
     /*
      * 'one mirror IO has finished' event handler:
      */
     if (bio->bi_status && !discard_error) {
         set_bit(WriteErrorSeen, &rdev->flags);
         if (!test_and_set_bit(WantReplacement, &rdev->flags))
             set_bit(MD_RECOVERY_NEEDED, &
                 conf->mddev->recovery);
 
         if (test_bit(FailFast, &rdev->flags) &&
             (bio->bi_opf & MD_FAILFAST) &&
             /* We never try FailFast to WriteMostly devices */
             !test_bit(WriteMostly, &rdev->flags)) {
             md_error(r1_bio->mddev, rdev);
         }
 
         /*
          * When the device is faulty, it is not necessary to
          * handle write error.
          */
         if (!test_bit(Faulty, &rdev->flags))
             set_bit(R1BIO_WriteError, &r1_bio->state);
         else {
             /* Fail the request */
             set_bit(R1BIO_Degraded, &r1_bio->state);
             /* Finished with this branch */
             r1_bio->bios[mirror] = NULL;
             to_put = bio;
         }
     } 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, &rdev->flags) &&
             !test_bit(Faulty, &rdev->flags))
             set_bit(R1BIO_Uptodate, &r1_bio->state);
 
         /* Maybe we can clear some bad blocks. */
         if (is_badblock(rdev, r1_bio->sector, r1_bio->sectors,
                 &first_bad, &bad_sectors) && !discard_error) {
             r1_bio->bios[mirror] = IO_MADE_GOOD;
             set_bit(R1BIO_MadeGood, &r1_bio->state);
         }
     }
 
     if (behind) {
         if (test_bit(CollisionCheck, &rdev->flags))
             remove_serial(rdev, lo, hi);
         if (test_bit(WriteMostly, &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);
             }
         }
     } else if (rdev->mddev->serialize_policy)
         remove_serial(rdev, lo, hi);
     if (r1_bio->bios[mirror] == NULL)
         rdev_dec_pending(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);
 }
 
 static sector_t align_to_barrier_unit_end(sector_t start_sector,
                       sector_t sectors)
 {
     sector_t len;
 
     WARN_ON(sectors == 0);
     /*
      * len is the number of sectors from start_sector to end of the
      * barrier unit which start_sector belongs to.
      */
     len = round_up(start_sector + 1, BARRIER_UNIT_SECTOR_SIZE) -
           start_sector;
 
     if (len > sectors)
         len = sectors;
 
     return len;
 }
 
 /*
  * 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;
     clear_bit(R1BIO_FailFast, &r1_bio->state);
 
     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 {
             if ((sectors > best_good_sectors) && (best_disk >= 0))
                 best_disk = -1;
             best_good_sectors = sectors;
         }
 
         if (best_disk >= 0)
             /* At least two disks to choose from so failfast is OK */
             set_bit(R1BIO_FailFast, &r1_bio->state);
 
         nonrot = bdev_nonrot(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 (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 || min_pending == 0)
             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);
         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 void flush_bio_list(struct r1conf *conf, struct bio *bio)
 {
     /* flush any pending bitmap writes to disk before proceeding w/ I/O */
     md_bitmap_unplug(conf->mddev->bitmap);
     wake_up(&conf->wait_barrier);
 
     while (bio) { /* submit pending writes */
         struct bio *next = bio->bi_next;
         struct md_rdev *rdev = (void *)bio->bi_bdev;
         bio->bi_next = NULL;
         bio_set_dev(bio, rdev->bdev);
         if (test_bit(Faulty, &rdev->flags)) {
             bio_io_error(bio);
         } else if (unlikely((bio_op(bio) == REQ_OP_DISCARD) &&
                     !bdev_max_discard_sectors(bio->bi_bdev)))
             /* Just ignore it */
             bio_endio(bio);
         else
             submit_bio_noacct(bio);
         bio = next;
         cond_resched();
     }
 }
 
 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 blk_plug plug;
         struct bio *bio;
 
         bio = bio_list_get(&conf->pending_bio_list);
         spin_unlock_irq(&conf->device_lock);
 
         /*
          * As this is called in a wait_event() loop (see freeze_array),
          * current->state might be TASK_UNINTERRUPTIBLE which will
          * cause a warning when we prepare to wait again.  As it is
          * rare that this path is taken, it is perfectly safe to force
          * us to go around the wait_event() loop again, so the warning
          * is a false-positive.  Silence the warning by resetting
          * thread state
          */
         __set_current_state(TASK_RUNNING);
         blk_start_plug(&plug);
         flush_bio_list(conf, bio);
         blk_finish_plug(&plug);
     } 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.
  *
  * If resync/recovery is interrupted, returns -EINTR;
  * Otherwise, returns 0.
  */
 static int raise_barrier(struct r1conf *conf, sector_t sector_nr)
 {
     int idx = sector_to_idx(sector_nr);
 
     spin_lock_irq(&conf->resync_lock);
 
     /* Wait until no block IO is waiting */
     wait_event_lock_irq(conf->wait_barrier,
                 !atomic_read(&conf->nr_waiting[idx]),
                 conf->resync_lock);
 
     /* block any new IO from starting */
     atomic_inc(&conf->barrier[idx]);
     /*
      * In raise_barrier() we firstly increase conf->barrier[idx] then
      * check conf->nr_pending[idx]. In _wait_barrier() we firstly
      * increase conf->nr_pending[idx] then check conf->barrier[idx].
      * A memory barrier here to make sure conf->nr_pending[idx] won't
      * be fetched before conf->barrier[idx] is increased. Otherwise
      * there will be a race between raise_barrier() and _wait_barrier().
      */
     smp_mb__after_atomic();
 
     /* For these conditions we must wait:
      * A: while the array is in frozen state
      * B: while conf->nr_pending[idx] is not 0, meaning regular I/O
      *    existing in corresponding I/O barrier bucket.
      * C: while conf->barrier[idx] >= RESYNC_DEPTH, meaning reaches
      *    max resync count which allowed on current I/O barrier bucket.
      */
     wait_event_lock_irq(conf->wait_barrier,
                 (!conf->array_frozen &&
                  !atomic_read(&conf->nr_pending[idx]) &&
                  atomic_read(&conf->barrier[idx]) < RESYNC_DEPTH) ||
                 test_bit(MD_RECOVERY_INTR, &conf->mddev->recovery),
                 conf->resync_lock);
 
     if (test_bit(MD_RECOVERY_INTR, &conf->mddev->recovery)) {
         atomic_dec(&conf->barrier[idx]);
         spin_unlock_irq(&conf->resync_lock);
         wake_up(&conf->wait_barrier);
         return -EINTR;
     }
 
     atomic_inc(&conf->nr_sync_pending);
     spin_unlock_irq(&conf->resync_lock);
 
     return 0;
 }
 
 static void lower_barrier(struct r1conf *conf, sector_t sector_nr)
 {
     int idx = sector_to_idx(sector_nr);
 
     BUG_ON(atomic_read(&conf->barrier[idx]) <= 0);
 
     atomic_dec(&conf->barrier[idx]);
     atomic_dec(&conf->nr_sync_pending);
     wake_up(&conf->wait_barrier);
 }
 
 static bool _wait_barrier(struct r1conf *conf, int idx, bool nowait)
 {
     bool ret = true;
 
     /*
      * We need to increase conf->nr_pending[idx] very early here,
      * then raise_barrier() can be blocked when it waits for
      * conf->nr_pending[idx] to be 0. Then we can avoid holding
      * conf->resync_lock when there is no barrier raised in same
      * barrier unit bucket. Also if the array is frozen, I/O
      * should be blocked until array is unfrozen.
      */
     atomic_inc(&conf->nr_pending[idx]);
     /*
      * In _wait_barrier() we firstly increase conf->nr_pending[idx], then
      * check conf->barrier[idx]. In raise_barrier() we firstly increase
      * conf->barrier[idx], then check conf->nr_pending[idx]. A memory
      * barrier is necessary here to make sure conf->barrier[idx] won't be
      * fetched before conf->nr_pending[idx] is increased. Otherwise there
      * will be a race between _wait_barrier() and raise_barrier().
      */
     smp_mb__after_atomic();
 
     /*
      * Don't worry about checking two atomic_t variables at same time
      * here. If during we check conf->barrier[idx], the array is
      * frozen (conf->array_frozen is 1), and chonf->barrier[idx] is
      * 0, it is safe to return and make the I/O continue. Because the
      * array is frozen, all I/O returned here will eventually complete
      * or be queued, no race will happen. See code comment in
      * frozen_array().
      */
     if (!READ_ONCE(conf->array_frozen) &&
         !atomic_read(&conf->barrier[idx]))
         return ret;
 
     /*
      * After holding conf->resync_lock, conf->nr_pending[idx]
      * should be decreased before waiting for barrier to drop.
      * Otherwise, we may encounter a race condition because
      * raise_barrer() might be waiting for conf->nr_pending[idx]
      * to be 0 at same time.
      */
     spin_lock_irq(&conf->resync_lock);
     atomic_inc(&conf->nr_waiting[idx]);
     atomic_dec(&conf->nr_pending[idx]);
     /*
      * In case freeze_array() is waiting for
      * get_unqueued_pending() == extra
      */
     wake_up(&conf->wait_barrier);
     /* Wait for the barrier in same barrier unit bucket to drop. */
 
     /* Return false when nowait flag is set */
     if (nowait) {
         ret = false;
     } else {
         wait_event_lock_irq(conf->wait_barrier,
                 !conf->array_frozen &&
                 !atomic_read(&conf->barrier[idx]),
                 conf->resync_lock);
         atomic_inc(&conf->nr_pending[idx]);
     }
 
     atomic_dec(&conf->nr_waiting[idx]);
     spin_unlock_irq(&conf->resync_lock);
     return ret;
 }
 
 static bool wait_read_barrier(struct r1conf *conf, sector_t sector_nr, bool nowait)
 {
     int idx = sector_to_idx(sector_nr);
     bool ret = true;
 
     /*
      * Very similar to _wait_barrier(). The difference is, for read
      * I/O we don't need wait for sync I/O, but if the whole array
      * is frozen, the read I/O still has to wait until the array is
      * unfrozen. Since there is no ordering requirement with
      * conf->barrier[idx] here, memory barrier is unnecessary as well.
      */
     atomic_inc(&conf->nr_pending[idx]);
 
     if (!READ_ONCE(conf->array_frozen))
         return ret;
 
     spin_lock_irq(&conf->resync_lock);
     atomic_inc(&conf->nr_waiting[idx]);
     atomic_dec(&conf->nr_pending[idx]);
     /*
      * In case freeze_array() is waiting for
      * get_unqueued_pending() == extra
      */
     wake_up(&conf->wait_barrier);
     /* Wait for array to be unfrozen */
 
     /* Return false when nowait flag is set */
     if (nowait) {
         /* Return false when nowait flag is set */
         ret = false;
     } else {
         wait_event_lock_irq(conf->wait_barrier,
                 !conf->array_frozen,
                 conf->resync_lock);
         atomic_inc(&conf->nr_pending[idx]);
     }
 
     atomic_dec(&conf->nr_waiting[idx]);
     spin_unlock_irq(&conf->resync_lock);
     return ret;
 }
 
 static bool wait_barrier(struct r1conf *conf, sector_t sector_nr, bool nowait)
 {
     int idx = sector_to_idx(sector_nr);
 
     return _wait_barrier(conf, idx, nowait);
 }
 
 static void _allow_barrier(struct r1conf *conf, int idx)
 {
     atomic_dec(&conf->nr_pending[idx]);
     wake_up(&conf->wait_barrier);
 }
 
 static void allow_barrier(struct r1conf *conf, sector_t sector_nr)
 {
     int idx = sector_to_idx(sector_nr);
 
     _allow_barrier(conf, idx);
 }
 
 /* conf->resync_lock should be held */
 static int get_unqueued_pending(struct r1conf *conf)
 {
     int idx, ret;
 
     ret = atomic_read(&conf->nr_sync_pending);
     for (idx = 0; idx < BARRIER_BUCKETS_NR; idx++)
         ret += atomic_read(&conf->nr_pending[idx]) -
             atomic_read(&conf->nr_queued[idx]);
 
     return ret;
 }
 
 static void freeze_array(struct r1conf *conf, int extra)
 {
     /* Stop sync I/O and normal I/O and wait for everything to
      * go quiet.
      * This is called in two situations:
      * 1) management command handlers (reshape, remove disk, quiesce).
      * 2) one normal I/O request failed.
 
      * After array_frozen is set to 1, new sync IO will be blocked at
      * raise_barrier(), and new normal I/O will blocked at _wait_barrier()
      * or wait_read_barrier(). The flying I/Os will either complete or be
      * queued. When everything goes quite, there are only queued I/Os left.
 
      * Every flying I/O contributes to a conf->nr_pending[idx], idx is the
      * barrier bucket index which this I/O request hits. When all sync and
      * normal I/O are queued, sum of all conf->nr_pending[] will match sum
      * of all conf->nr_queued[]. But normal I/O failure is an exception,
      * in handle_read_error(), we may call freeze_array() before trying to
      * fix the read error. In this case, the error read I/O is not queued,
      * so get_unqueued_pending() == 1.
      *
      * Therefore before this function returns, we need to wait until
      * get_unqueued_pendings(conf) gets equal to extra. For
      * normal I/O context, extra is 1, in rested situations extra is 0.
      */
     spin_lock_irq(&conf->resync_lock);
     conf->array_frozen = 1;
     raid1_log(conf->mddev, "wait freeze");
     wait_event_lock_irq_cmd(
         conf->wait_barrier,
         get_unqueued_pending(conf) == 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;
     spin_unlock_irq(&conf->resync_lock);
     wake_up(&conf->wait_barrier);
 }
 
 static void alloc_behind_master_bio(struct r1bio *r1_bio,
                        struct bio *bio)
 {
     int size = bio->bi_iter.bi_size;
     unsigned vcnt = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
     int i = 0;
     struct bio *behind_bio = NULL;
 
     behind_bio = bio_alloc_bioset(NULL, vcnt, 0, GFP_NOIO,
                       &r1_bio->mddev->bio_set);
     if (!behind_bio)
         return;
 
     /* discard op, we don't support writezero/writesame yet */
     if (!bio_has_data(bio)) {
         behind_bio->bi_iter.bi_size = size;
         goto skip_copy;
     }
 
     while (i < vcnt && size) {
         struct page *page;
         int len = min_t(int, PAGE_SIZE, size);
 
         page = alloc_page(GFP_NOIO);
         if (unlikely(!page))
             goto free_pages;
 
         bio_add_page(behind_bio, page, len, 0);
 
         size -= len;
         i++;
     }
 
     bio_copy_data(behind_bio, bio);
 skip_copy:
     r1_bio->behind_master_bio = behind_bio;
     set_bit(R1BIO_BehindIO, &r1_bio->state);
 
     return;
 
 free_pages:
     pr_debug("%dB behind alloc failed, doing sync I/O\n",
          bio->bi_iter.bi_size);
     bio_free_pages(behind_bio);
     bio_put(behind_bio);
 }
 
 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);
         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);
     flush_bio_list(conf, bio);
     kfree(plug);
 }
 
 static void init_r1bio(struct r1bio *r1_bio, struct mddev *mddev, struct bio *bio)
 {
     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;
 }
 
 static inline struct r1bio *
 alloc_r1bio(struct mddev *mddev, struct bio *bio)
 {
     struct r1conf *conf = mddev->private;
     struct r1bio *r1_bio;
 
     r1_bio = mempool_alloc(&conf->r1bio_pool, GFP_NOIO);
     /* Ensure no bio records IO_BLOCKED */
     memset(r1_bio->bios, 0, conf->raid_disks * sizeof(r1_bio->bios[0]));
     init_r1bio(r1_bio, mddev, bio);
     return r1_bio;
 }
 
 static void raid1_read_request(struct mddev *mddev, struct bio *bio,
                    int max_read_sectors, struct r1bio *r1_bio)
 {
     struct r1conf *conf = mddev->private;
     struct raid1_info *mirror;
     struct bio *read_bio;
     struct bitmap *bitmap = mddev->bitmap;
     const enum req_op op = bio_op(bio);
     const blk_opf_t do_sync = bio->bi_opf & REQ_SYNC;
     int max_sectors;
     int rdisk;
     bool r1bio_existed = !!r1_bio;
     char b[BDEVNAME_SIZE];
 
     /*
      * If r1_bio is set, we are blocking the raid1d thread
      * so there is a tiny risk of deadlock.  So ask for
      * emergency memory if needed.
      */
     gfp_t gfp = r1_bio ? (GFP_NOIO | __GFP_HIGH) : GFP_NOIO;
 
     if (r1bio_existed) {
         /* Need to get the block device name carefully */
         struct md_rdev *rdev;
         rcu_read_lock();
         rdev = rcu_dereference(conf->mirrors[r1_bio->read_disk].rdev);
         if (rdev)
             snprintf(b, sizeof(b), "%pg", rdev->bdev);
         else
             strcpy(b, "???");
         rcu_read_unlock();
     }
 
     /*
      * Still need barrier for READ in case that whole
      * array is frozen.
      */
     if (!wait_read_barrier(conf, bio->bi_iter.bi_sector,
                 bio->bi_opf & REQ_NOWAIT)) {
         bio_wouldblock_error(bio);
         return;
     }
 
     if (!r1_bio)
         r1_bio = alloc_r1bio(mddev, bio);
     else
         init_r1bio(r1_bio, mddev, bio);
     r1_bio->sectors = max_read_sectors;
 
     /*
      * make_request() can abort the operation when read-ahead is being
      * used and no empty request is available.
      */
     rdisk = read_balance(conf, r1_bio, &max_sectors);
 
     if (rdisk < 0) {
         /* couldn't find anywhere to read from */
         if (r1bio_existed) {
             pr_crit_ratelimited("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);
         return;
     }
     mirror = conf->mirrors + rdisk;
 
     if (r1bio_existed)
         pr_info_ratelimited("md/raid1:%s: redirecting sector %llu to other mirror: %pg\n",
                     mdname(mddev),
                     (unsigned long long)r1_bio->sector,
                     mirror->rdev->bdev);
 
     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'
          */
         raid1_log(mddev, "wait behind writes");
         wait_event(bitmap->behind_wait,
                atomic_read(&bitmap->behind_writes) == 0);
     }
 
     if (max_sectors < bio_sectors(bio)) {
         struct bio *split = bio_split(bio, max_sectors,
                           gfp, &conf->bio_split);
         bio_chain(split, bio);
         submit_bio_noacct(bio);
         bio = split;
         r1_bio->master_bio = bio;
         r1_bio->sectors = max_sectors;
     }
 
     r1_bio->read_disk = rdisk;
 
     if (!r1bio_existed && blk_queue_io_stat(bio->bi_bdev->bd_disk->queue))
         r1_bio->start_time = bio_start_io_acct(bio);
 
     read_bio = bio_alloc_clone(mirror->rdev->bdev, bio, gfp,
                    &mddev->bio_set);
 
     r1_bio->bios[rdisk] = read_bio;
 
     read_bio->bi_iter.bi_sector = r1_bio->sector +
         mirror->rdev->data_offset;
     read_bio->bi_end_io = raid1_end_read_request;
     bio_set_op_attrs(read_bio, op, do_sync);
     if (test_bit(FailFast, &mirror->rdev->flags) &&
         test_bit(R1BIO_FailFast, &r1_bio->state))
             read_bio->bi_opf |= MD_FAILFAST;
     read_bio->bi_private = r1_bio;
 
     if (mddev->gendisk)
             trace_block_bio_remap(read_bio, disk_devt(mddev->gendisk),
                       r1_bio->sector);
 
     submit_bio_noacct(read_bio);
 }
 
 static void raid1_write_request(struct mddev *mddev, struct bio *bio,
                 int max_write_sectors)
 {
     struct r1conf *conf = mddev->private;
     struct r1bio *r1_bio;
     int i, disks;
     struct bitmap *bitmap = mddev->bitmap;
     unsigned long flags;
     struct md_rdev *blocked_rdev;
     struct blk_plug_cb *cb;
     struct raid1_plug_cb *plug = NULL;
     int first_clone;
     int max_sectors;
     bool write_behind = false;
 
     if (mddev_is_clustered(mddev) &&
          md_cluster_ops->area_resyncing(mddev, WRITE,
              bio->bi_iter.bi_sector, bio_end_sector(bio))) {
 
         DEFINE_WAIT(w);
         if (bio->bi_opf & REQ_NOWAIT) {
             bio_wouldblock_error(bio);
             return;
         }
         for (;;) {
             prepare_to_wait(&conf->wait_barrier,
                     &w, TASK_IDLE);
             if (!md_cluster_ops->area_resyncing(mddev, WRITE,
                             bio->bi_iter.bi_sector,
                             bio_end_sector(bio)))
                 break;
             schedule();
         }
         finish_wait(&conf->wait_barrier, &w);
     }
 
     /*
      * 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.
      */
     if (!wait_barrier(conf, bio->bi_iter.bi_sector,
                 bio->bi_opf & REQ_NOWAIT)) {
         bio_wouldblock_error(bio);
         return;
     }
 
     r1_bio = alloc_r1bio(mddev, bio);
     r1_bio->sectors = max_write_sectors;
 
     /* 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:
     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);
 
         /*
          * The write-behind io is only attempted on drives marked as
          * write-mostly, which means we could allocate write behind
          * bio later.
          */
         if (rdev && test_bit(WriteMostly, &rdev->flags))
             write_behind = true;
 
         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;
 
         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, bio->bi_iter.bi_sector);
 
         if (bio->bi_opf & REQ_NOWAIT) {
             bio_wouldblock_error(bio);
             return;
         }
         raid1_log(mddev, "wait rdev %d blocked", blocked_rdev->raid_disk);
         md_wait_for_blocked_rdev(blocked_rdev, mddev);
         wait_barrier(conf, bio->bi_iter.bi_sector, false);
         goto retry_write;
     }
 
     /*
      * When using a bitmap, we may call alloc_behind_master_bio below.
      * alloc_behind_master_bio allocates a copy of the data payload a page
      * at a time and thus needs a new bio that can fit the whole payload
      * this bio in page sized chunks.
      */
     if (write_behind && bitmap)
         max_sectors = min_t(int, max_sectors,
                     BIO_MAX_VECS * (PAGE_SIZE >> 9));
     if (max_sectors < bio_sectors(bio)) {
         struct bio *split = bio_split(bio, max_sectors,
                           GFP_NOIO, &conf->bio_split);
         bio_chain(split, bio);
         submit_bio_noacct(bio);
         bio = split;
         r1_bio->master_bio = bio;
         r1_bio->sectors = max_sectors;
     }
 
     if (blk_queue_io_stat(bio->bi_bdev->bd_disk->queue))
         r1_bio->start_time = bio_start_io_acct(bio);
     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 = NULL;
         struct md_rdev *rdev = conf->mirrors[i].rdev;
         if (!r1_bio->bios[i])
             continue;
 
         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 &&
                 test_bit(WriteMostly, &rdev->flags) &&
                 (atomic_read(&bitmap->behind_writes)
                  < mddev->bitmap_info.max_write_behind) &&
                 !waitqueue_active(&bitmap->behind_wait)) {
                 alloc_behind_master_bio(r1_bio, bio);
             }
 
             md_bitmap_startwrite(bitmap, r1_bio->sector, r1_bio->sectors,
                          test_bit(R1BIO_BehindIO, &r1_bio->state));
             first_clone = 0;
         }
 
         if (r1_bio->behind_master_bio) {
             mbio = bio_alloc_clone(rdev->bdev,
                            r1_bio->behind_master_bio,
                            GFP_NOIO, &mddev->bio_set);
             if (test_bit(CollisionCheck, &rdev->flags))
                 wait_for_serialization(rdev, r1_bio);
             if (test_bit(WriteMostly, &rdev->flags))
                 atomic_inc(&r1_bio->behind_remaining);
         } else {
             mbio = bio_alloc_clone(rdev->bdev, bio, GFP_NOIO,
                            &mddev->bio_set);
 
             if (mddev->serialize_policy)
                 wait_for_serialization(rdev, r1_bio);
         }
 
         r1_bio->bios[i] = mbio;
 
         mbio->bi_iter.bi_sector = (r1_bio->sector + rdev->data_offset);
         mbio->bi_end_io = raid1_end_write_request;
         mbio->bi_opf = bio_op(bio) | (bio->bi_opf & (REQ_SYNC | REQ_FUA));
         if (test_bit(FailFast, &rdev->flags) &&
             !test_bit(WriteMostly, &rdev->flags) &&
             conf->raid_disks - mddev->degraded > 1)
             mbio->bi_opf |= MD_FAILFAST;
         mbio->bi_private = r1_bio;
 
         atomic_inc(&r1_bio->remaining);
 
         if (mddev->gendisk)
             trace_block_bio_remap(mbio, disk_devt(mddev->gendisk),
                           r1_bio->sector);
         /* flush_pending_writes() needs access to the rdev so...*/
         mbio->bi_bdev = (void *)rdev;
 
         cb = blk_check_plugged(raid1_unplug, mddev, sizeof(*plug));
         if (cb)
             plug = container_of(cb, struct raid1_plug_cb, cb);
         else
             plug = NULL;
         if (plug) {
             bio_list_add(&plug->pending, mbio);
         } else {
             spin_lock_irqsave(&conf->device_lock, flags);
             bio_list_add(&conf->pending_bio_list, mbio);
             spin_unlock_irqrestore(&conf->device_lock, flags);
             md_wakeup_thread(mddev->thread);
         }
     }
 
     r1_bio_write_done(r1_bio);
 
     /* In case raid1d snuck in to freeze_array */
     wake_up(&conf->wait_barrier);
 }
 
 static bool raid1_make_request(struct mddev *mddev, struct bio *bio)
 {
     sector_t sectors;
 
     if (unlikely(bio->bi_opf & REQ_PREFLUSH)
         && md_flush_request(mddev, bio))
         return true;
 
     /*
      * There is a limit to the maximum size, but
      * the read/write handler might find a lower limit
      * due to bad blocks.  To avoid multiple splits,
      * we pass the maximum number of sectors down
      * and let the lower level perform the split.
      */
     sectors = align_to_barrier_unit_end(
         bio->bi_iter.bi_sector, bio_sectors(bio));
 
     if (bio_data_dir(bio) == READ)
         raid1_read_request(mddev, bio, sectors, NULL);
     else {
         if (!md_write_start(mddev,bio))
             return false;
         raid1_write_request(mddev, bio, sectors);
     }
     return true;
 }
 
 static void raid1_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, "]");
 }
 
 /**
  * raid1_error() - RAID1 error handler.
  * @mddev: affected md device.
  * @rdev: member device to fail.
  *
  * The routine acknowledges &rdev failure and determines new @mddev state.
  * If it failed, then:
  *  - &MD_BROKEN flag is set in &mddev->flags.
  *  - recovery is disabled.
  * Otherwise, it must be degraded:
  *  - recovery is interrupted.
  *  - &mddev->degraded is bumped.
  *
  * @rdev is marked as &Faulty excluding case when array is failed and
  * &mddev->fail_last_dev is off.
  */
 static void raid1_error(struct mddev *mddev, struct md_rdev *rdev)
 {
     struct r1conf *conf = mddev->private;
     unsigned long flags;
 
     spin_lock_irqsave(&conf->device_lock, flags);
 
     if (test_bit(In_sync, &rdev->flags) &&
         (conf->raid_disks - mddev->degraded) == 1) {
         set_bit(MD_BROKEN, &mddev->flags);
 
         if (!mddev->fail_last_dev) {
             conf->recovery_disabled = mddev->recovery_disabled;
             spin_unlock_irqrestore(&conf->device_lock, flags);
             return;
         }
     }
     set_bit(Blocked, &rdev->flags);
     if (test_and_clear_bit(In_sync, &rdev->flags))
         mddev->degraded++;
     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_mask_bits(&mddev->sb_flags, 0,
               BIT(MD_SB_CHANGE_DEVS) | BIT(MD_SB_CHANGE_PENDING));
     pr_crit("md/raid1:%s: Disk failure on %pg, disabling device.\n"
         "md/raid1:%s: Operation continuing on %d devices.\n",
         mdname(mddev), rdev->bdev,
         mdname(mddev), conf->raid_disks - mddev->degraded);
 }
 
 static void print_conf(struct r1conf *conf)
 {
     int i;
 
     pr_debug("RAID1 conf printout:\n");
     if (!conf) {
         pr_debug("(!conf)\n");
         return;
     }
     pr_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++) {
         struct md_rdev *rdev = rcu_dereference(conf->mirrors[i].rdev);
         if (rdev)
             pr_debug(" disk %d, wo:%d, o:%d, dev:%pg\n",
                  i, !test_bit(In_sync, &rdev->flags),
                  !test_bit(Faulty, &rdev->flags),
                  rdev->bdev);
     }
     rcu_read_unlock();
 }
 
 static void close_sync(struct r1conf *conf)
 {
     int idx;
 
     for (idx = 0; idx < BARRIER_BUCKETS_NR; idx++) {
         _wait_barrier(conf, idx, false);
         _allow_barrier(conf, idx);
     }
 
     mempool_exit(&conf->r1buf_pool);
 }
 
 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 &&
         rdev->saved_raid_disk < conf->raid_disks &&
         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;
         }
     }
     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;
         if (!test_bit(RemoveSynchronized, &rdev->flags)) {
             synchronize_rcu();
             if (atomic_read(&rdev->nr_pending)) {
                 /* lost the race, try later */
                 err = -EBUSY;
                 p->rdev = rdev;
                 goto abort;
             }
         }
         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);
             if (atomic_read(&repl->nr_pending)) {
                 /* It means that some queued IO of retry_list
                  * hold repl. Thus, we cannot set replacement
                  * as NULL, avoiding rdev NULL pointer
                  * dereference in sync_request_write and
                  * handle_write_finished.
                  */
                 err = -EBUSY;
                 unfreeze_array(conf);
                 goto abort;
             }
             clear_bit(Replacement, &repl->flags);
             p->rdev = repl;
             conf->mirrors[conf->raid_disks + number].rdev = NULL;
             unfreeze_array(conf);
         }
 
         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 = get_resync_r1bio(bio);
 
     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_status)
         set_bit(R1BIO_Uptodate, &r1_bio->state);
 
     if (atomic_dec_and_test(&r1_bio->remaining))
         reschedule_retry(r1_bio);
 }
 
 static void abort_sync_write(struct mddev *mddev, struct r1bio *r1_bio)
 {
     sector_t sync_blocks = 0;
     sector_t s = r1_bio->sector;
     long sectors_to_go = r1_bio->sectors;
 
     /* make sure these bits don't get cleared. */
     do {
         md_bitmap_end_sync(mddev->bitmap, s, &sync_blocks, 1);
         s += sync_blocks;
         sectors_to_go -= sync_blocks;
     } while (sectors_to_go > 0);
 }
 
 static void put_sync_write_buf(struct r1bio *r1_bio, int uptodate)
 {
     if (atomic_dec_and_test(&r1_bio->remaining)) {
         struct mddev *mddev = r1_bio->mddev;
         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 void end_sync_write(struct bio *bio)
 {
     int uptodate = !bio->bi_status;
     struct r1bio *r1_bio = get_resync_r1bio(bio);
     struct mddev *mddev = r1_bio->mddev;
     struct r1conf *conf = mddev->private;
     sector_t first_bad;
     int bad_sectors;
     struct md_rdev *rdev = conf->mirrors[find_bio_disk(r1_bio, bio)].rdev;
 
     if (!uptodate) {
         abort_sync_write(mddev, r1_bio);
         set_bit(WriteErrorSeen, &rdev->flags);
         if (!test_and_set_bit(WantReplacement, &rdev->flags))
             set_bit(MD_RECOVERY_NEEDED, &
                 mddev->recovery);
         set_bit(R1BIO_WriteError, &r1_bio->state);
     } else if (is_badblock(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);
 
     put_sync_write_buf(r1_bio, 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];
     struct page **pages = get_resync_pages(bio)->pages;
     sector_t sect = r1_bio->sector;
     int sectors = r1_bio->sectors;
     int idx = 0;
     struct md_rdev *rdev;
 
     rdev = conf->mirrors[r1_bio->read_disk].rdev;
     if (test_bit(FailFast, &rdev->flags)) {
         /* Don't try recovering from here - just fail it
          * ... unless it is the last working device of course */
         md_error(mddev, rdev);
         if (test_bit(Faulty, &rdev->flags))
             /* Don't try to read from here, but make sure
              * put_buf does it's thing
              */
             bio->bi_end_io = end_sync_write;
     }
 
     while(sectors) {
         int s = sectors;
         int d = r1_bio->read_disk;
         int success = 0;
         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,
                          pages[idx],
                          REQ_OP_READ, false)) {
                     success = 1;
                     break;
                 }
             }
             d++;
             if (d == conf->raid_disks * 2)
                 d = 0;
         } while (!success && d != r1_bio->read_disk);
 
         if (!success) {
             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.
              */
             pr_crit_ratelimited("md/raid1:%s: %pg: unrecoverable I/O read error for block %llu\n",
                         mdname(mddev), bio->bi_bdev,
                         (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,
                         pages[idx],
                         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,
                         pages[idx],
                         READ) != 0)
                 atomic_add(s, &rdev->corrected_errors);
         }
         sectors -= s;
         sect += s;
         idx ++;
     }
     set_bit(R1BIO_Uptodate, &r1_bio->state);
     bio->bi_status = 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++) {
         blk_status_t status;
         struct bio *b = r1_bio->bios[i];
         struct resync_pages *rp = get_resync_pages(b);
         if (b->bi_end_io != end_sync_read)
             continue;
         /* fixup the bio for reuse, but preserve errno */
         status = b->bi_status;
         bio_reset(b, conf->mirrors[i].rdev->bdev, REQ_OP_READ);
         b->bi_status = status;
         b->bi_iter.bi_sector = r1_bio->sector +
             conf->mirrors[i].rdev->data_offset;
         b->bi_end_io = end_sync_read;
         rp->raid_bio = r1_bio;
         b->bi_private = rp;
 
         /* initialize bvec table again */
         md_bio_reset_resync_pages(b, rp, r1_bio->sectors << 9);
     }
     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_status) {
             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 = 0;
         struct bio *pbio = r1_bio->bios[primary];
         struct bio *sbio = r1_bio->bios[i];
         blk_status_t status = sbio->bi_status;
         struct page **ppages = get_resync_pages(pbio)->pages;
         struct page **spages = get_resync_pages(sbio)->pages;
         struct bio_vec *bi;
         int page_len[RESYNC_PAGES] = { 0 };
         struct bvec_iter_all iter_all;
 
         if (sbio->bi_end_io != end_sync_read)
             continue;
         /* Now we can 'fixup' the error value */
         sbio->bi_status = 0;
 
         bio_for_each_segment_all(bi, sbio, iter_all)
             page_len[j++] = bi->bv_len;
 
         if (!status) {
             for (j = vcnt; j-- ; ) {
                 if (memcmp(page_address(ppages[j]),
                        page_address(spages[j]),
                        page_len[j]))
                     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)
                   && !status)) {
             /* 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 *wbio;
 
     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;
         if (test_bit(Faulty, &conf->mirrors[i].rdev->flags)) {
             abort_sync_write(mddev, r1_bio);
             continue;
         }
 
         bio_set_op_attrs(wbio, REQ_OP_WRITE, 0);
         if (test_bit(FailFast, &conf->mirrors[i].rdev->flags))
             wbio->bi_opf |= MD_FAILFAST;
 
         wbio->bi_end_io = end_sync_write;
         atomic_inc(&r1_bio->remaining);
         md_sync_acct(conf->mirrors[i].rdev->bdev, bio_sectors(wbio));
 
         submit_bio_noacct(wbio);
     }
 
     put_sync_write_buf(r1_bio, 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 {
             sector_t first_bad;
             int bad_sectors;
 
             rcu_read_lock();
             rdev = rcu_dereference(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) {
                 atomic_inc(&rdev->nr_pending);
                 rcu_read_unlock();
                 if (sync_page_io(rdev, sect, s<<9,
                      conf->tmppage, REQ_OP_READ, false))
                     success = 1;
                 rdev_dec_pending(rdev, mddev);
                 if (success)
                     break;
             } else
                 rcu_read_unlock();
             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--;
             rcu_read_lock();
             rdev = rcu_dereference(conf->mirrors[d].rdev);
             if (rdev &&
                 !test_bit(Faulty, &rdev->flags)) {
                 atomic_inc(&rdev->nr_pending);
                 rcu_read_unlock();
                 r1_sync_page_io(rdev, sect, s,
                         conf->tmppage, WRITE);
                 rdev_dec_pending(rdev, mddev);
             } else
                 rcu_read_unlock();
         }
         d = start;
         while (d != read_disk) {
             if (d==0)
                 d = conf->raid_disks * 2;
             d--;
             rcu_read_lock();
             rdev = rcu_dereference(conf->mirrors[d].rdev);
             if (rdev &&
                 !test_bit(Faulty, &rdev->flags)) {
                 atomic_inc(&rdev->nr_pending);
                 rcu_read_unlock();
                 if (r1_sync_page_io(rdev, sect, s,
                             conf->tmppage, READ)) {
                     atomic_add(s, &rdev->corrected_errors);
                     pr_info("md/raid1:%s: read error corrected (%d sectors at %llu on %pg)\n",
                         mdname(mddev), s,
                         (unsigned long long)(sect +
                                      rdev->data_offset),
                         rdev->bdev);
                 }
                 rdev_dec_pending(rdev, mddev);
             } else
                 rcu_read_unlock();
         }
         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)) {
             wbio = bio_alloc_clone(rdev->bdev,
                            r1_bio->behind_master_bio,
                            GFP_NOIO, &mddev->bio_set);
         } else {
             wbio = bio_alloc_clone(rdev->bdev, r1_bio->master_bio,
                            GFP_NOIO, &mddev->bio_set);
         }
 
         bio_set_op_attrs(wbio, REQ_OP_WRITE, 0);
         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;
 
         if (submit_bio_wait(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_status &&
             test_bit(R1BIO_MadeGood, &r1_bio->state)) {
             rdev_clear_badblocks(rdev, r1_bio->sector, s, 0);
         }
         if (bio->bi_status &&
             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, idx;
     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);
         idx = sector_to_idx(r1_bio->sector);
         atomic_inc(&conf->nr_queued[idx]);
         spin_unlock_irq(&conf->device_lock);
         /*
          * In case freeze_array() is waiting for condition
          * get_unqueued_pending() == extra to be true.
          */
         wake_up(&conf->wait_barrier);
         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)
 {
     struct mddev *mddev = conf->mddev;
     struct bio *bio;
     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
      */
 
     bio = r1_bio->bios[r1_bio->read_disk];
     bio_put(bio);
     r1_bio->bios[r1_bio->read_disk] = NULL;
 
     rdev = conf->mirrors[r1_bio->read_disk].rdev;
     if (mddev->ro == 0
         && !test_bit(FailFast, &rdev->flags)) {
         freeze_array(conf, 1);
         fix_read_error(conf, r1_bio->read_disk,
                    r1_bio->sector, r1_bio->sectors);
         unfreeze_array(conf);
     } else if (mddev->ro == 0 && test_bit(FailFast, &rdev->flags)) {
         md_error(mddev, rdev);
     } else {
         r1_bio->bios[r1_bio->read_disk] = IO_BLOCKED;
     }
 
     rdev_dec_pending(rdev, conf->mddev);
     allow_barrier(conf, r1_bio->sector);
     bio = r1_bio->master_bio;
 
     /* Reuse the old r1_bio so that the IO_BLOCKED settings are preserved */
     r1_bio->state = 0;
     raid1_read_request(mddev, bio, r1_bio->sectors, r1_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;
     int idx;
 
     md_check_recovery(mddev);
 
     if (!list_empty_careful(&conf->bio_end_io_list) &&
         !test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags)) {
         LIST_HEAD(tmp);
         spin_lock_irqsave(&conf->device_lock, flags);
         if (!test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags))
             list_splice_init(&conf->bio_end_io_list, &tmp);
         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);
             idx = sector_to_idx(r1_bio->sector);
             atomic_dec(&conf->nr_queued[idx]);
             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);
         idx = sector_to_idx(r1_bio->sector);
         atomic_dec(&conf->nr_queued[idx]);
         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
             WARN_ON_ONCE(1);
 
         cond_resched();
         if (mddev->sb_flags & ~(1<<MD_SB_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(mempool_initialized(&conf->r1buf_pool));
 
     return mempool_init(&conf->r1buf_pool, buffs, r1buf_pool_alloc,
                 r1buf_pool_free, conf->poolinfo);
 }
 
 static struct r1bio *raid1_alloc_init_r1buf(struct r1conf *conf)
 {
     struct r1bio *r1bio = mempool_alloc(&conf->r1buf_pool, GFP_NOIO);
     struct resync_pages *rps;
     struct bio *bio;
     int i;
 
     for (i = conf->poolinfo->raid_disks; i--; ) {
         bio = r1bio->bios[i];
         rps = bio->bi_private;
         bio_reset(bio, NULL, 0);
         bio->bi_private = rps;
     }
     r1bio->master_bio = NULL;
     return r1bio;
 }
 
 /*
  * 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 raid1_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 */
     int idx = sector_to_idx(sector_nr);
     int page_idx = 0;
 
     if (!mempool_initialized(&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 */
             md_bitmap_end_sync(mddev->bitmap, mddev->curr_resync,
                        &sync_blocks, 1);
         else /* completed sync */
             conf->fullsync = 0;
 
         md_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 (!md_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;
     }
 
     /*
      * If there is non-resync activity waiting for a turn, then let it
      * though before starting on this new sync request.
      */
     if (atomic_read(&conf->nr_waiting[idx]))
         schedule_timeout_uninterruptible(1);
 
     /* we are incrementing sector_nr below. To be safe, we check against
      * sector_nr + two times RESYNC_SECTORS
      */
 
     md_bitmap_cond_end_sync(mddev->bitmap, sector_nr,
         mddev_is_clustered(mddev) && (sector_nr + 2 * RESYNC_SECTORS > conf->cluster_sync_high));
 
 
     if (raise_barrier(conf, sector_nr))
         return 0;
 
     r1_bio = raid1_alloc_init_r1buf(conf);
 
     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);
     /* make sure good_sectors won't go across barrier unit boundary */
     good_sectors = align_to_barrier_unit_end(sector_nr, good_sectors);
 
     for (i = 0; i < conf->raid_disks * 2; i++) {
         struct md_rdev *rdev;
         bio = r1_bio->bios[i];
 
         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_set_op_attrs(bio, REQ_OP_WRITE, 0);
             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_set_op_attrs(bio, REQ_OP_READ, 0);
                 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_set_op_attrs(bio, REQ_OP_WRITE, 0);
                 bio->bi_end_io = end_sync_write;
                 write_targets++;
             }
         }
         if (rdev && bio->bi_end_io) {
             atomic_inc(&rdev->nr_pending);
             bio->bi_iter.bi_sector = sector_nr + rdev->data_offset;
             bio_set_dev(bio, rdev->bdev);
             if (test_bit(FailFast, &rdev->flags))
                 bio->bi_opf |= MD_FAILFAST;
         }
     }
     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_SB_CHANGE_DEVS, &mddev->sb_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 (!md_bitmap_start_sync(mddev->bitmap, sector_nr,
                           &sync_blocks, still_degraded) &&
                 !conf->fullsync &&
                 !test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery))
                 break;
             if ((len >> 9) > sync_blocks)
                 len = sync_blocks<<9;
         }
 
         for (i = 0 ; i < conf->raid_disks * 2; i++) {
             struct resync_pages *rp;
 
             bio = r1_bio->bios[i];
             rp = get_resync_pages(bio);
             if (bio->bi_end_io) {
                 page = resync_fetch_page(rp, page_idx);
 
                 /*
                  * won't fail because the vec table is big
                  * enough to hold all these pages
                  */
                 bio_add_page(bio, page, len, 0);
             }
         }
         nr_sectors += len>>9;
         sector_nr += len>>9;
         sync_blocks -= (len>>9);
     } while (++page_idx < RESYNC_PAGES);
 
     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(bio, nr_sectors);
                 if (read_targets == 1)
                     bio->bi_opf &= ~MD_FAILFAST;
                 submit_bio_noacct(bio);
             }
         }
     } else {
         atomic_set(&r1_bio->remaining, 1);
         bio = r1_bio->bios[r1_bio->read_disk];
         md_sync_acct_bio(bio, nr_sectors);
         if (read_targets == 1)
             bio->bi_opf &= ~MD_FAILFAST;
         submit_bio_noacct(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->nr_pending = kcalloc(BARRIER_BUCKETS_NR,
                    sizeof(atomic_t), GFP_KERNEL);
     if (!conf->nr_pending)
         goto abort;
 
     conf->nr_waiting = kcalloc(BARRIER_BUCKETS_NR,
                    sizeof(atomic_t), GFP_KERNEL);
     if (!conf->nr_waiting)
         goto abort;
 
     conf->nr_queued = kcalloc(BARRIER_BUCKETS_NR,
                   sizeof(atomic_t), GFP_KERNEL);
     if (!conf->nr_queued)
         goto abort;
 
     conf->barrier = kcalloc(BARRIER_BUCKETS_NR,
                 sizeof(atomic_t), GFP_KERNEL);
     if (!conf->barrier)
         goto abort;
 
     conf->mirrors = kzalloc(array3_size(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;
     err = mempool_init(&conf->r1bio_pool, NR_RAID_BIOS, r1bio_pool_alloc,
                rbio_pool_free, conf->poolinfo);
     if (err)
         goto abort;
 
     err = bioset_init(&conf->bio_split, BIO_POOL_SIZE, 0, 0);
     if (err)
         goto abort;
 
     conf->poolinfo->mddev = mddev;
 
     err = -EINVAL;
     spin_lock_init(&conf->device_lock);
     rdev_for_each(rdev, mddev) {
         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;
         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->recovery_disabled = mddev->recovery_disabled - 1;
 
     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)
         goto abort;
 
     return conf;
 
  abort:
     if (conf) {
         mempool_exit(&conf->r1bio_pool);
         kfree(conf->mirrors);
         safe_put_page(conf->tmppage);
         kfree(conf->poolinfo);
         kfree(conf->nr_pending);
         kfree(conf->nr_waiting);
         kfree(conf->nr_queued);
         kfree(conf->barrier);
         bioset_exit(&conf->bio_split);
         kfree(conf);
     }
     return ERR_PTR(err);
 }
 
 static void raid1_free(struct mddev *mddev, void *priv);
 static int raid1_run(struct mddev *mddev)
 {
     struct r1conf *conf;
     int i;
     struct md_rdev *rdev;
     int ret;
 
     if (mddev->level != 1) {
         pr_warn("md/raid1:%s: raid level not set to mirroring (%d)\n",
             mdname(mddev), mddev->level);
         return -EIO;
     }
     if (mddev->reshape_position != MaxSector) {
         pr_warn("md/raid1:%s: reshape_position set but not supported\n",
             mdname(mddev));
         return -EIO;
     }
     if (mddev_init_writes_pending(mddev) < 0)
         return -ENOMEM;
     /*
      * 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_zeroes_sectors(mddev->queue, 0);
 
     rdev_for_each(rdev, mddev) {
         if (!mddev->gendisk)
             continue;
         disk_stack_limits(mddev->gendisk, rdev->bdev,
                   rdev->data_offset << 9);
     }
 
     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++;
     /*
      * RAID1 needs at least one disk in active
      */
     if (conf->raid_disks - mddev->degraded < 1) {
         ret = -EINVAL;
         goto abort;
     }
 
     if (conf->raid_disks - mddev->degraded == 1)
         mddev->recovery_cp = MaxSector;
 
     if (mddev->recovery_cp != MaxSector)
         pr_info("md/raid1:%s: not clean -- starting background reconstruction\n",
             mdname(mddev));
     pr_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;
     set_bit(MD_FAILFAST_SUPPORTED, &mddev->flags);
 
     md_set_array_sectors(mddev, raid1_size(mddev, 0, 0));
 
     ret = md_integrity_register(mddev);
     if (ret) {
         md_unregister_thread(&mddev->thread);
         goto abort;
     }
     return 0;
 
 abort:
     raid1_free(mddev, conf);
     return ret;
 }
 
 static void raid1_free(struct mddev *mddev, void *priv)
 {
     struct r1conf *conf = priv;
 
     mempool_exit(&conf->r1bio_pool);
     kfree(conf->mirrors);
     safe_put_page(conf->tmppage);
     kfree(conf->poolinfo);
     kfree(conf->nr_pending);
     kfree(conf->nr_waiting);
     kfree(conf->nr_queued);
     kfree(conf->barrier);
     bioset_exit(&conf->bio_split);
     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 = md_bitmap_resize(mddev->bitmap, newsize, 0, 0);
         if (ret)
             return ret;
     }
     md_set_array_sectors(mddev, newsize);
     if (sectors > mddev->dev_sectors &&
         mddev->recovery_cp > mddev->dev_sectors) {
         mddev->recovery_cp = mddev->dev_sectors;
         set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
     }
     mddev->dev_sectors = sectors;
     mddev->resync_max_sectors = sectors;
     return 0;
 }
 
 static int 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;
     int ret;
 
     memset(&newpool, 0, sizeof(newpool));
     memset(&oldpool, 0, sizeof(oldpool));
 
     /* 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))
         md_allow_write(mddev);
 
     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;
 
     ret = mempool_init(&newpool, NR_RAID_BIOS, r1bio_pool_alloc,
                rbio_pool_free, newpoolinfo);
     if (ret) {
         kfree(newpoolinfo);
         return ret;
     }
     newmirrors = kzalloc(array3_size(sizeof(struct raid1_info),
                      raid_disks, 2),
                  GFP_KERNEL);
     if (!newmirrors) {
         kfree(newpoolinfo);
         mempool_exit(&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))
                 pr_warn("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_exit(&oldpool);
     return 0;
 }
 
 static void raid1_quiesce(struct mddev *mddev, int quiesce)
 {
     struct r1conf *conf = mddev->private;
 
     if (quiesce)
         freeze_array(conf, 0);
     else
         unfreeze_array(conf);
 }
 
 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;
             mddev_clear_unsupported_flags(mddev,
                 UNSUPPORTED_MDDEV_FLAGS);
         }
         return conf;
     }
     return ERR_PTR(-EINVAL);
 }
 
 static struct md_personality raid1_personality =
 {
     .name       = "raid1",
     .level      = 1,
     .owner      = THIS_MODULE,
     .make_request   = raid1_make_request,
     .run        = raid1_run,
     .free       = raid1_free,
     .status     = raid1_status,
     .error_handler  = raid1_error,
     .hot_add_disk   = raid1_add_disk,
     .hot_remove_disk= raid1_remove_disk,
     .spare_active   = raid1_spare_active,
     .sync_request   = raid1_sync_request,
     .resize     = raid1_resize,
     .size       = raid1_size,
     .check_reshape  = raid1_reshape,
     .quiesce    = raid1_quiesce,
     .takeover   = raid1_takeover,
 };
 
 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");