OSCL-LXR linux-6.0.1/​drivers/​md/​raid5-cache.c	Source navigation Diff markup Identifier search General search
	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-only
 /*
  * Copyright (C) 2015 Shaohua Li <shli@fb.com>
  * Copyright (C) 2016 Song Liu <songliubraving@fb.com>
  */
 #include <linux/kernel.h>
 #include <linux/wait.h>
 #include <linux/blkdev.h>
 #include <linux/slab.h>
 #include <linux/raid/md_p.h>
 #include <linux/crc32c.h>
 #include <linux/random.h>
 #include <linux/kthread.h>
 #include <linux/types.h>
 #include "md.h"
 #include "raid5.h"
 #include "md-bitmap.h"
 #include "raid5-log.h"
 
 /*
  * metadata/data stored in disk with 4k size unit (a block) regardless
  * underneath hardware sector size. only works with PAGE_SIZE == 4096
  */
 #define BLOCK_SECTORS (8)
 #define BLOCK_SECTOR_SHIFT (3)
 
 /*
  * log->max_free_space is min(1/4 disk size, 10G reclaimable space).
  *
  * In write through mode, the reclaim runs every log->max_free_space.
  * This can prevent the recovery scans for too long
  */
 #define RECLAIM_MAX_FREE_SPACE (10 * 1024 * 1024 * 2) /* sector */
 #define RECLAIM_MAX_FREE_SPACE_SHIFT (2)
 
 /* wake up reclaim thread periodically */
 #define R5C_RECLAIM_WAKEUP_INTERVAL (30 * HZ)
 /* start flush with these full stripes */
 #define R5C_FULL_STRIPE_FLUSH_BATCH(conf) (conf->max_nr_stripes / 4)
 /* reclaim stripes in groups */
 #define R5C_RECLAIM_STRIPE_GROUP (NR_STRIPE_HASH_LOCKS * 2)
 
 /*
  * We only need 2 bios per I/O unit to make progress, but ensure we
  * have a few more available to not get too tight.
  */
 #define R5L_POOL_SIZE   4
 
 static char *r5c_journal_mode_str[] = {"write-through",
                        "write-back"};
 /*
  * raid5 cache state machine
  *
  * With the RAID cache, each stripe works in two phases:
  *  - caching phase
  *  - writing-out phase
  *
  * These two phases are controlled by bit STRIPE_R5C_CACHING:
  *   if STRIPE_R5C_CACHING == 0, the stripe is in writing-out phase
  *   if STRIPE_R5C_CACHING == 1, the stripe is in caching phase
  *
  * When there is no journal, or the journal is in write-through mode,
  * the stripe is always in writing-out phase.
  *
  * For write-back journal, the stripe is sent to caching phase on write
  * (r5c_try_caching_write). r5c_make_stripe_write_out() kicks off
  * the write-out phase by clearing STRIPE_R5C_CACHING.
  *
  * Stripes in caching phase do not write the raid disks. Instead, all
  * writes are committed from the log device. Therefore, a stripe in
  * caching phase handles writes as:
  *  - write to log device
  *  - return IO
  *
  * Stripes in writing-out phase handle writes as:
  *  - calculate parity
  *  - write pending data and parity to journal
  *  - write data and parity to raid disks
  *  - return IO for pending writes
  */
 
 struct r5l_log {
     struct md_rdev *rdev;
 
     u32 uuid_checksum;
 
     sector_t device_size;       /* log device size, round to
                      * BLOCK_SECTORS */
     sector_t max_free_space;    /* reclaim run if free space is at
                      * this size */
 
     sector_t last_checkpoint;   /* log tail. where recovery scan
                      * starts from */
     u64 last_cp_seq;        /* log tail sequence */
 
     sector_t log_start;     /* log head. where new data appends */
     u64 seq;            /* log head sequence */
 
     sector_t next_checkpoint;
 
     struct mutex io_mutex;
     struct r5l_io_unit *current_io; /* current io_unit accepting new data */
 
     spinlock_t io_list_lock;
     struct list_head running_ios;   /* io_units which are still running,
                      * and have not yet been completely
                      * written to the log */
     struct list_head io_end_ios;    /* io_units which have been completely
                      * written to the log but not yet written
                      * to the RAID */
     struct list_head flushing_ios;  /* io_units which are waiting for log
                      * cache flush */
     struct list_head finished_ios;  /* io_units which settle down in log disk */
     struct bio flush_bio;
 
     struct list_head no_mem_stripes;   /* pending stripes, -ENOMEM */
 
     struct kmem_cache *io_kc;
     mempool_t io_pool;
     struct bio_set bs;
     mempool_t meta_pool;
 
     struct md_thread *reclaim_thread;
     unsigned long reclaim_target;   /* number of space that need to be
                      * reclaimed.  if it's 0, reclaim spaces
                      * used by io_units which are in
                      * IO_UNIT_STRIPE_END state (eg, reclaim
                      * dones't wait for specific io_unit
                      * switching to IO_UNIT_STRIPE_END
                      * state) */
     wait_queue_head_t iounit_wait;
 
     struct list_head no_space_stripes; /* pending stripes, log has no space */
     spinlock_t no_space_stripes_lock;
 
     bool need_cache_flush;
 
     /* for r5c_cache */
     enum r5c_journal_mode r5c_journal_mode;
 
     /* all stripes in r5cache, in the order of seq at sh->log_start */
     struct list_head stripe_in_journal_list;
 
     spinlock_t stripe_in_journal_lock;
     atomic_t stripe_in_journal_count;
 
     /* to submit async io_units, to fulfill ordering of flush */
     struct work_struct deferred_io_work;
     /* to disable write back during in degraded mode */
     struct work_struct disable_writeback_work;
 
     /* to for chunk_aligned_read in writeback mode, details below */
     spinlock_t tree_lock;
     struct radix_tree_root big_stripe_tree;
 };
 
 /*
  * Enable chunk_aligned_read() with write back cache.
  *
  * Each chunk may contain more than one stripe (for example, a 256kB
  * chunk contains 64 4kB-page, so this chunk contain 64 stripes). For
  * chunk_aligned_read, these stripes are grouped into one "big_stripe".
  * For each big_stripe, we count how many stripes of this big_stripe
  * are in the write back cache. These data are tracked in a radix tree
  * (big_stripe_tree). We use radix_tree item pointer as the counter.
  * r5c_tree_index() is used to calculate keys for the radix tree.
  *
  * chunk_aligned_read() calls r5c_big_stripe_cached() to look up
  * big_stripe of each chunk in the tree. If this big_stripe is in the
  * tree, chunk_aligned_read() aborts. This look up is protected by
  * rcu_read_lock().
  *
  * It is necessary to remember whether a stripe is counted in
  * big_stripe_tree. Instead of adding new flag, we reuses existing flags:
  * STRIPE_R5C_PARTIAL_STRIPE and STRIPE_R5C_FULL_STRIPE. If either of these
  * two flags are set, the stripe is counted in big_stripe_tree. This
  * requires moving set_bit(STRIPE_R5C_PARTIAL_STRIPE) to
  * r5c_try_caching_write(); and moving clear_bit of
  * STRIPE_R5C_PARTIAL_STRIPE and STRIPE_R5C_FULL_STRIPE to
  * r5c_finish_stripe_write_out().
  */
 
 /*
  * radix tree requests lowest 2 bits of data pointer to be 2b'00.
  * So it is necessary to left shift the counter by 2 bits before using it
  * as data pointer of the tree.
  */
 #define R5C_RADIX_COUNT_SHIFT 2
 
 /*
  * calculate key for big_stripe_tree
  *
  * sect: align_bi->bi_iter.bi_sector or sh->sector
  */
 static inline sector_t r5c_tree_index(struct r5conf *conf,
                       sector_t sect)
 {
     sector_div(sect, conf->chunk_sectors);
     return sect;
 }
 
 /*
  * an IO range starts from a meta data block and end at the next meta data
  * block. The io unit's the meta data block tracks data/parity followed it. io
  * unit is written to log disk with normal write, as we always flush log disk
  * first and then start move data to raid disks, there is no requirement to
  * write io unit with FLUSH/FUA
  */
 struct r5l_io_unit {
     struct r5l_log *log;
 
     struct page *meta_page; /* store meta block */
     int meta_offset;    /* current offset in meta_page */
 
     struct bio *current_bio;/* current_bio accepting new data */
 
     atomic_t pending_stripe;/* how many stripes not flushed to raid */
     u64 seq;        /* seq number of the metablock */
     sector_t log_start; /* where the io_unit starts */
     sector_t log_end;   /* where the io_unit ends */
     struct list_head log_sibling; /* log->running_ios */
     struct list_head stripe_list; /* stripes added to the io_unit */
 
     int state;
     bool need_split_bio;
     struct bio *split_bio;
 
     unsigned int has_flush:1;       /* include flush request */
     unsigned int has_fua:1;         /* include fua request */
     unsigned int has_null_flush:1;      /* include null flush request */
     unsigned int has_flush_payload:1;   /* include flush payload  */
     /*
      * io isn't sent yet, flush/fua request can only be submitted till it's
      * the first IO in running_ios list
      */
     unsigned int io_deferred:1;
 
     struct bio_list flush_barriers;   /* size == 0 flush bios */
 };
 
 /* r5l_io_unit state */
 enum r5l_io_unit_state {
     IO_UNIT_RUNNING = 0,    /* accepting new IO */
     IO_UNIT_IO_START = 1,   /* io_unit bio start writing to log,
                  * don't accepting new bio */
     IO_UNIT_IO_END = 2, /* io_unit bio finish writing to log */
     IO_UNIT_STRIPE_END = 3, /* stripes data finished writing to raid */
 };
 
 bool r5c_is_writeback(struct r5l_log *log)
 {
     return (log != NULL &&
         log->r5c_journal_mode == R5C_JOURNAL_MODE_WRITE_BACK);
 }
 
 static sector_t r5l_ring_add(struct r5l_log *log, sector_t start, sector_t inc)
 {
     start += inc;
     if (start >= log->device_size)
         start = start - log->device_size;
     return start;
 }
 
 static sector_t r5l_ring_distance(struct r5l_log *log, sector_t start,
                   sector_t end)
 {
     if (end >= start)
         return end - start;
     else
         return end + log->device_size - start;
 }
 
 static bool r5l_has_free_space(struct r5l_log *log, sector_t size)
 {
     sector_t used_size;
 
     used_size = r5l_ring_distance(log, log->last_checkpoint,
                     log->log_start);
 
     return log->device_size > used_size + size;
 }
 
 static void __r5l_set_io_unit_state(struct r5l_io_unit *io,
                     enum r5l_io_unit_state state)
 {
     if (WARN_ON(io->state >= state))
         return;
     io->state = state;
 }
 
 static void
 r5c_return_dev_pending_writes(struct r5conf *conf, struct r5dev *dev)
 {
     struct bio *wbi, *wbi2;
 
     wbi = dev->written;
     dev->written = NULL;
     while (wbi && wbi->bi_iter.bi_sector <
            dev->sector + RAID5_STRIPE_SECTORS(conf)) {
         wbi2 = r5_next_bio(conf, wbi, dev->sector);
         md_write_end(conf->mddev);
         bio_endio(wbi);
         wbi = wbi2;
     }
 }
 
 void r5c_handle_cached_data_endio(struct r5conf *conf,
                   struct stripe_head *sh, int disks)
 {
     int i;
 
     for (i = sh->disks; i--; ) {
         if (sh->dev[i].written) {
             set_bit(R5_UPTODATE, &sh->dev[i].flags);
             r5c_return_dev_pending_writes(conf, &sh->dev[i]);
             md_bitmap_endwrite(conf->mddev->bitmap, sh->sector,
                        RAID5_STRIPE_SECTORS(conf),
                        !test_bit(STRIPE_DEGRADED, &sh->state),
                        0);
         }
     }
 }
 
 void r5l_wake_reclaim(struct r5l_log *log, sector_t space);
 
 /* Check whether we should flush some stripes to free up stripe cache */
 void r5c_check_stripe_cache_usage(struct r5conf *conf)
 {
     int total_cached;
 
     if (!r5c_is_writeback(conf->log))
         return;
 
     total_cached = atomic_read(&conf->r5c_cached_partial_stripes) +
         atomic_read(&conf->r5c_cached_full_stripes);
 
     /*
      * The following condition is true for either of the following:
      *   - stripe cache pressure high:
      *          total_cached > 3/4 min_nr_stripes ||
      *          empty_inactive_list_nr > 0
      *   - stripe cache pressure moderate:
      *          total_cached > 1/2 min_nr_stripes
      */
     if (total_cached > conf->min_nr_stripes * 1 / 2 ||
         atomic_read(&conf->empty_inactive_list_nr) > 0)
         r5l_wake_reclaim(conf->log, 0);
 }
 
 /*
  * flush cache when there are R5C_FULL_STRIPE_FLUSH_BATCH or more full
  * stripes in the cache
  */
 void r5c_check_cached_full_stripe(struct r5conf *conf)
 {
     if (!r5c_is_writeback(conf->log))
         return;
 
     /*
      * wake up reclaim for R5C_FULL_STRIPE_FLUSH_BATCH cached stripes
      * or a full stripe (chunk size / 4k stripes).
      */
     if (atomic_read(&conf->r5c_cached_full_stripes) >=
         min(R5C_FULL_STRIPE_FLUSH_BATCH(conf),
         conf->chunk_sectors >> RAID5_STRIPE_SHIFT(conf)))
         r5l_wake_reclaim(conf->log, 0);
 }
 
 /*
  * Total log space (in sectors) needed to flush all data in cache
  *
  * To avoid deadlock due to log space, it is necessary to reserve log
  * space to flush critical stripes (stripes that occupying log space near
  * last_checkpoint). This function helps check how much log space is
  * required to flush all cached stripes.
  *
  * To reduce log space requirements, two mechanisms are used to give cache
  * flush higher priorities:
  *    1. In handle_stripe_dirtying() and schedule_reconstruction(),
  *       stripes ALREADY in journal can be flushed w/o pending writes;
  *    2. In r5l_write_stripe() and r5c_cache_data(), stripes NOT in journal
  *       can be delayed (r5l_add_no_space_stripe).
  *
  * In cache flush, the stripe goes through 1 and then 2. For a stripe that
  * already passed 1, flushing it requires at most (conf->max_degraded + 1)
  * pages of journal space. For stripes that has not passed 1, flushing it
  * requires (conf->raid_disks + 1) pages of journal space. There are at
  * most (conf->group_cnt + 1) stripe that passed 1. So total journal space
  * required to flush all cached stripes (in pages) is:
  *
  *     (stripe_in_journal_count - group_cnt - 1) * (max_degraded + 1) +
  *     (group_cnt + 1) * (raid_disks + 1)
  * or
  *     (stripe_in_journal_count) * (max_degraded + 1) +
  *     (group_cnt + 1) * (raid_disks - max_degraded)
  */
 static sector_t r5c_log_required_to_flush_cache(struct r5conf *conf)
 {
     struct r5l_log *log = conf->log;
 
     if (!r5c_is_writeback(log))
         return 0;
 
     return BLOCK_SECTORS *
         ((conf->max_degraded + 1) * atomic_read(&log->stripe_in_journal_count) +
          (conf->raid_disks - conf->max_degraded) * (conf->group_cnt + 1));
 }
 
 /*
  * evaluate log space usage and update R5C_LOG_TIGHT and R5C_LOG_CRITICAL
  *
  * R5C_LOG_TIGHT is set when free space on the log device is less than 3x of
  * reclaim_required_space. R5C_LOG_CRITICAL is set when free space on the log
  * device is less than 2x of reclaim_required_space.
  */
 static inline void r5c_update_log_state(struct r5l_log *log)
 {
     struct r5conf *conf = log->rdev->mddev->private;
     sector_t free_space;
     sector_t reclaim_space;
     bool wake_reclaim = false;
 
     if (!r5c_is_writeback(log))
         return;
 
     free_space = r5l_ring_distance(log, log->log_start,
                        log->last_checkpoint);
     reclaim_space = r5c_log_required_to_flush_cache(conf);
     if (free_space < 2 * reclaim_space)
         set_bit(R5C_LOG_CRITICAL, &conf->cache_state);
     else {
         if (test_bit(R5C_LOG_CRITICAL, &conf->cache_state))
             wake_reclaim = true;
         clear_bit(R5C_LOG_CRITICAL, &conf->cache_state);
     }
     if (free_space < 3 * reclaim_space)
         set_bit(R5C_LOG_TIGHT, &conf->cache_state);
     else
         clear_bit(R5C_LOG_TIGHT, &conf->cache_state);
 
     if (wake_reclaim)
         r5l_wake_reclaim(log, 0);
 }
 
 /*
  * Put the stripe into writing-out phase by clearing STRIPE_R5C_CACHING.
  * This function should only be called in write-back mode.
  */
 void r5c_make_stripe_write_out(struct stripe_head *sh)
 {
     struct r5conf *conf = sh->raid_conf;
     struct r5l_log *log = conf->log;
 
     BUG_ON(!r5c_is_writeback(log));
 
     WARN_ON(!test_bit(STRIPE_R5C_CACHING, &sh->state));
     clear_bit(STRIPE_R5C_CACHING, &sh->state);
 
     if (!test_and_set_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
         atomic_inc(&conf->preread_active_stripes);
 }
 
 static void r5c_handle_data_cached(struct stripe_head *sh)
 {
     int i;
 
     for (i = sh->disks; i--; )
         if (test_and_clear_bit(R5_Wantwrite, &sh->dev[i].flags)) {
             set_bit(R5_InJournal, &sh->dev[i].flags);
             clear_bit(R5_LOCKED, &sh->dev[i].flags);
         }
     clear_bit(STRIPE_LOG_TRAPPED, &sh->state);
 }
 
 /*
  * this journal write must contain full parity,
  * it may also contain some data pages
  */
 static void r5c_handle_parity_cached(struct stripe_head *sh)
 {
     int i;
 
     for (i = sh->disks; i--; )
         if (test_bit(R5_InJournal, &sh->dev[i].flags))
             set_bit(R5_Wantwrite, &sh->dev[i].flags);
 }
 
 /*
  * Setting proper flags after writing (or flushing) data and/or parity to the
  * log device. This is called from r5l_log_endio() or r5l_log_flush_endio().
  */
 static void r5c_finish_cache_stripe(struct stripe_head *sh)
 {
     struct r5l_log *log = sh->raid_conf->log;
 
     if (log->r5c_journal_mode == R5C_JOURNAL_MODE_WRITE_THROUGH) {
         BUG_ON(test_bit(STRIPE_R5C_CACHING, &sh->state));
         /*
          * Set R5_InJournal for parity dev[pd_idx]. This means
          * all data AND parity in the journal. For RAID 6, it is
          * NOT necessary to set the flag for dev[qd_idx], as the
          * two parities are written out together.
          */
         set_bit(R5_InJournal, &sh->dev[sh->pd_idx].flags);
     } else if (test_bit(STRIPE_R5C_CACHING, &sh->state)) {
         r5c_handle_data_cached(sh);
     } else {
         r5c_handle_parity_cached(sh);
         set_bit(R5_InJournal, &sh->dev[sh->pd_idx].flags);
     }
 }
 
 static void r5l_io_run_stripes(struct r5l_io_unit *io)
 {
     struct stripe_head *sh, *next;
 
     list_for_each_entry_safe(sh, next, &io->stripe_list, log_list) {
         list_del_init(&sh->log_list);
 
         r5c_finish_cache_stripe(sh);
 
         set_bit(STRIPE_HANDLE, &sh->state);
         raid5_release_stripe(sh);
     }
 }
 
 static void r5l_log_run_stripes(struct r5l_log *log)
 {
     struct r5l_io_unit *io, *next;
 
     lockdep_assert_held(&log->io_list_lock);
 
     list_for_each_entry_safe(io, next, &log->running_ios, log_sibling) {
         /* don't change list order */
         if (io->state < IO_UNIT_IO_END)
             break;
 
         list_move_tail(&io->log_sibling, &log->finished_ios);
         r5l_io_run_stripes(io);
     }
 }
 
 static void r5l_move_to_end_ios(struct r5l_log *log)
 {
     struct r5l_io_unit *io, *next;
 
     lockdep_assert_held(&log->io_list_lock);
 
     list_for_each_entry_safe(io, next, &log->running_ios, log_sibling) {
         /* don't change list order */
         if (io->state < IO_UNIT_IO_END)
             break;
         list_move_tail(&io->log_sibling, &log->io_end_ios);
     }
 }
 
 static void __r5l_stripe_write_finished(struct r5l_io_unit *io);
 static void r5l_log_endio(struct bio *bio)
 {
     struct r5l_io_unit *io = bio->bi_private;
     struct r5l_io_unit *io_deferred;
     struct r5l_log *log = io->log;
     unsigned long flags;
     bool has_null_flush;
     bool has_flush_payload;
 
     if (bio->bi_status)
         md_error(log->rdev->mddev, log->rdev);
 
     bio_put(bio);
     mempool_free(io->meta_page, &log->meta_pool);
 
     spin_lock_irqsave(&log->io_list_lock, flags);
     __r5l_set_io_unit_state(io, IO_UNIT_IO_END);
 
     /*
      * if the io doesn't not have null_flush or flush payload,
      * it is not safe to access it after releasing io_list_lock.
      * Therefore, it is necessary to check the condition with
      * the lock held.
      */
     has_null_flush = io->has_null_flush;
     has_flush_payload = io->has_flush_payload;
 
     if (log->need_cache_flush && !list_empty(&io->stripe_list))
         r5l_move_to_end_ios(log);
     else
         r5l_log_run_stripes(log);
     if (!list_empty(&log->running_ios)) {
         /*
          * FLUSH/FUA io_unit is deferred because of ordering, now we
          * can dispatch it
          */
         io_deferred = list_first_entry(&log->running_ios,
                            struct r5l_io_unit, log_sibling);
         if (io_deferred->io_deferred)
             schedule_work(&log->deferred_io_work);
     }
 
     spin_unlock_irqrestore(&log->io_list_lock, flags);
 
     if (log->need_cache_flush)
         md_wakeup_thread(log->rdev->mddev->thread);
 
     /* finish flush only io_unit and PAYLOAD_FLUSH only io_unit */
     if (has_null_flush) {
         struct bio *bi;
 
         WARN_ON(bio_list_empty(&io->flush_barriers));
         while ((bi = bio_list_pop(&io->flush_barriers)) != NULL) {
             bio_endio(bi);
             if (atomic_dec_and_test(&io->pending_stripe)) {
                 __r5l_stripe_write_finished(io);
                 return;
             }
         }
     }
     /* decrease pending_stripe for flush payload */
     if (has_flush_payload)
         if (atomic_dec_and_test(&io->pending_stripe))
             __r5l_stripe_write_finished(io);
 }
 
 static void r5l_do_submit_io(struct r5l_log *log, struct r5l_io_unit *io)
 {
     unsigned long flags;
 
     spin_lock_irqsave(&log->io_list_lock, flags);
     __r5l_set_io_unit_state(io, IO_UNIT_IO_START);
     spin_unlock_irqrestore(&log->io_list_lock, flags);
 
     /*
      * In case of journal device failures, submit_bio will get error
      * and calls endio, then active stripes will continue write
      * process. Therefore, it is not necessary to check Faulty bit
      * of journal device here.
      *
      * We can't check split_bio after current_bio is submitted. If
      * io->split_bio is null, after current_bio is submitted, current_bio
      * might already be completed and the io_unit is freed. We submit
      * split_bio first to avoid the issue.
      */
     if (io->split_bio) {
         if (io->has_flush)
             io->split_bio->bi_opf |= REQ_PREFLUSH;
         if (io->has_fua)
             io->split_bio->bi_opf |= REQ_FUA;
         submit_bio(io->split_bio);
     }
 
     if (io->has_flush)
         io->current_bio->bi_opf |= REQ_PREFLUSH;
     if (io->has_fua)
         io->current_bio->bi_opf |= REQ_FUA;
     submit_bio(io->current_bio);
 }
 
 /* deferred io_unit will be dispatched here */
 static void r5l_submit_io_async(struct work_struct *work)
 {
     struct r5l_log *log = container_of(work, struct r5l_log,
                        deferred_io_work);
     struct r5l_io_unit *io = NULL;
     unsigned long flags;
 
     spin_lock_irqsave(&log->io_list_lock, flags);
     if (!list_empty(&log->running_ios)) {
         io = list_first_entry(&log->running_ios, struct r5l_io_unit,
                       log_sibling);
         if (!io->io_deferred)
             io = NULL;
         else
             io->io_deferred = 0;
     }
     spin_unlock_irqrestore(&log->io_list_lock, flags);
     if (io)
         r5l_do_submit_io(log, io);
 }
 
 static void r5c_disable_writeback_async(struct work_struct *work)
 {
     struct r5l_log *log = container_of(work, struct r5l_log,
                        disable_writeback_work);
     struct mddev *mddev = log->rdev->mddev;
     struct r5conf *conf = mddev->private;
     int locked = 0;
 
     if (log->r5c_journal_mode == R5C_JOURNAL_MODE_WRITE_THROUGH)
         return;
     pr_info("md/raid:%s: Disabling writeback cache for degraded array.\n",
         mdname(mddev));
 
     /* wait superblock change before suspend */
     wait_event(mddev->sb_wait,
            conf->log == NULL ||
            (!test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags) &&
             (locked = mddev_trylock(mddev))));
     if (locked) {
         mddev_suspend(mddev);
         log->r5c_journal_mode = R5C_JOURNAL_MODE_WRITE_THROUGH;
         mddev_resume(mddev);
         mddev_unlock(mddev);
     }
 }
 
 static void r5l_submit_current_io(struct r5l_log *log)
 {
     struct r5l_io_unit *io = log->current_io;
     struct r5l_meta_block *block;
     unsigned long flags;
     u32 crc;
     bool do_submit = true;
 
     if (!io)
         return;
 
     block = page_address(io->meta_page);
     block->meta_size = cpu_to_le32(io->meta_offset);
     crc = crc32c_le(log->uuid_checksum, block, PAGE_SIZE);
     block->checksum = cpu_to_le32(crc);
 
     log->current_io = NULL;
     spin_lock_irqsave(&log->io_list_lock, flags);
     if (io->has_flush || io->has_fua) {
         if (io != list_first_entry(&log->running_ios,
                        struct r5l_io_unit, log_sibling)) {
             io->io_deferred = 1;
             do_submit = false;
         }
     }
     spin_unlock_irqrestore(&log->io_list_lock, flags);
     if (do_submit)
         r5l_do_submit_io(log, io);
 }
 
 static struct bio *r5l_bio_alloc(struct r5l_log *log)
 {
     struct bio *bio = bio_alloc_bioset(log->rdev->bdev, BIO_MAX_VECS,
                        REQ_OP_WRITE, GFP_NOIO, &log->bs);
 
     bio->bi_iter.bi_sector = log->rdev->data_offset + log->log_start;
 
     return bio;
 }
 
 static void r5_reserve_log_entry(struct r5l_log *log, struct r5l_io_unit *io)
 {
     log->log_start = r5l_ring_add(log, log->log_start, BLOCK_SECTORS);
 
     r5c_update_log_state(log);
     /*
      * If we filled up the log device start from the beginning again,
      * which will require a new bio.
      *
      * Note: for this to work properly the log size needs to me a multiple
      * of BLOCK_SECTORS.
      */
     if (log->log_start == 0)
         io->need_split_bio = true;
 
     io->log_end = log->log_start;
 }
 
 static struct r5l_io_unit *r5l_new_meta(struct r5l_log *log)
 {
     struct r5l_io_unit *io;
     struct r5l_meta_block *block;
 
     io = mempool_alloc(&log->io_pool, GFP_ATOMIC);
     if (!io)
         return NULL;
     memset(io, 0, sizeof(*io));
 
     io->log = log;
     INIT_LIST_HEAD(&io->log_sibling);
     INIT_LIST_HEAD(&io->stripe_list);
     bio_list_init(&io->flush_barriers);
     io->state = IO_UNIT_RUNNING;
 
     io->meta_page = mempool_alloc(&log->meta_pool, GFP_NOIO);
     block = page_address(io->meta_page);
     clear_page(block);
     block->magic = cpu_to_le32(R5LOG_MAGIC);
     block->version = R5LOG_VERSION;
     block->seq = cpu_to_le64(log->seq);
     block->position = cpu_to_le64(log->log_start);
 
     io->log_start = log->log_start;
     io->meta_offset = sizeof(struct r5l_meta_block);
     io->seq = log->seq++;
 
     io->current_bio = r5l_bio_alloc(log);
     io->current_bio->bi_end_io = r5l_log_endio;
     io->current_bio->bi_private = io;
     bio_add_page(io->current_bio, io->meta_page, PAGE_SIZE, 0);
 
     r5_reserve_log_entry(log, io);
 
     spin_lock_irq(&log->io_list_lock);
     list_add_tail(&io->log_sibling, &log->running_ios);
     spin_unlock_irq(&log->io_list_lock);
 
     return io;
 }
 
 static int r5l_get_meta(struct r5l_log *log, unsigned int payload_size)
 {
     if (log->current_io &&
         log->current_io->meta_offset + payload_size > PAGE_SIZE)
         r5l_submit_current_io(log);
 
     if (!log->current_io) {
         log->current_io = r5l_new_meta(log);
         if (!log->current_io)
             return -ENOMEM;
     }
 
     return 0;
 }
 
 static void r5l_append_payload_meta(struct r5l_log *log, u16 type,
                     sector_t location,
                     u32 checksum1, u32 checksum2,
                     bool checksum2_valid)
 {
     struct r5l_io_unit *io = log->current_io;
     struct r5l_payload_data_parity *payload;
 
     payload = page_address(io->meta_page) + io->meta_offset;
     payload->header.type = cpu_to_le16(type);
     payload->header.flags = cpu_to_le16(0);
     payload->size = cpu_to_le32((1 + !!checksum2_valid) <<
                     (PAGE_SHIFT - 9));
     payload->location = cpu_to_le64(location);
     payload->checksum[0] = cpu_to_le32(checksum1);
     if (checksum2_valid)
         payload->checksum[1] = cpu_to_le32(checksum2);
 
     io->meta_offset += sizeof(struct r5l_payload_data_parity) +
         sizeof(__le32) * (1 + !!checksum2_valid);
 }
 
 static void r5l_append_payload_page(struct r5l_log *log, struct page *page)
 {
     struct r5l_io_unit *io = log->current_io;
 
     if (io->need_split_bio) {
         BUG_ON(io->split_bio);
         io->split_bio = io->current_bio;
         io->current_bio = r5l_bio_alloc(log);
         bio_chain(io->current_bio, io->split_bio);
         io->need_split_bio = false;
     }
 
     if (!bio_add_page(io->current_bio, page, PAGE_SIZE, 0))
         BUG();
 
     r5_reserve_log_entry(log, io);
 }
 
 static void r5l_append_flush_payload(struct r5l_log *log, sector_t sect)
 {
     struct mddev *mddev = log->rdev->mddev;
     struct r5conf *conf = mddev->private;
     struct r5l_io_unit *io;
     struct r5l_payload_flush *payload;
     int meta_size;
 
     /*
      * payload_flush requires extra writes to the journal.
      * To avoid handling the extra IO in quiesce, just skip
      * flush_payload
      */
     if (conf->quiesce)
         return;
 
     mutex_lock(&log->io_mutex);
     meta_size = sizeof(struct r5l_payload_flush) + sizeof(__le64);
 
     if (r5l_get_meta(log, meta_size)) {
         mutex_unlock(&log->io_mutex);
         return;
     }
 
     /* current implementation is one stripe per flush payload */
     io = log->current_io;
     payload = page_address(io->meta_page) + io->meta_offset;
     payload->header.type = cpu_to_le16(R5LOG_PAYLOAD_FLUSH);
     payload->header.flags = cpu_to_le16(0);
     payload->size = cpu_to_le32(sizeof(__le64));
     payload->flush_stripes[0] = cpu_to_le64(sect);
     io->meta_offset += meta_size;
     /* multiple flush payloads count as one pending_stripe */
     if (!io->has_flush_payload) {
         io->has_flush_payload = 1;
         atomic_inc(&io->pending_stripe);
     }
     mutex_unlock(&log->io_mutex);
 }
 
 static int r5l_log_stripe(struct r5l_log *log, struct stripe_head *sh,
                int data_pages, int parity_pages)
 {
     int i;
     int meta_size;
     int ret;
     struct r5l_io_unit *io;
 
     meta_size =
         ((sizeof(struct r5l_payload_data_parity) + sizeof(__le32))
          * data_pages) +
         sizeof(struct r5l_payload_data_parity) +
         sizeof(__le32) * parity_pages;
 
     ret = r5l_get_meta(log, meta_size);
     if (ret)
         return ret;
 
     io = log->current_io;
 
     if (test_and_clear_bit(STRIPE_R5C_PREFLUSH, &sh->state))
         io->has_flush = 1;
 
     for (i = 0; i < sh->disks; i++) {
         if (!test_bit(R5_Wantwrite, &sh->dev[i].flags) ||
             test_bit(R5_InJournal, &sh->dev[i].flags))
             continue;
         if (i == sh->pd_idx || i == sh->qd_idx)
             continue;
         if (test_bit(R5_WantFUA, &sh->dev[i].flags) &&
             log->r5c_journal_mode == R5C_JOURNAL_MODE_WRITE_BACK) {
             io->has_fua = 1;
             /*
              * we need to flush journal to make sure recovery can
              * reach the data with fua flag
              */
             io->has_flush = 1;
         }
         r5l_append_payload_meta(log, R5LOG_PAYLOAD_DATA,
                     raid5_compute_blocknr(sh, i, 0),
                     sh->dev[i].log_checksum, 0, false);
         r5l_append_payload_page(log, sh->dev[i].page);
     }
 
     if (parity_pages == 2) {
         r5l_append_payload_meta(log, R5LOG_PAYLOAD_PARITY,
                     sh->sector, sh->dev[sh->pd_idx].log_checksum,
                     sh->dev[sh->qd_idx].log_checksum, true);
         r5l_append_payload_page(log, sh->dev[sh->pd_idx].page);
         r5l_append_payload_page(log, sh->dev[sh->qd_idx].page);
     } else if (parity_pages == 1) {
         r5l_append_payload_meta(log, R5LOG_PAYLOAD_PARITY,
                     sh->sector, sh->dev[sh->pd_idx].log_checksum,
                     0, false);
         r5l_append_payload_page(log, sh->dev[sh->pd_idx].page);
     } else  /* Just writing data, not parity, in caching phase */
         BUG_ON(parity_pages != 0);
 
     list_add_tail(&sh->log_list, &io->stripe_list);
     atomic_inc(&io->pending_stripe);
     sh->log_io = io;
 
     if (log->r5c_journal_mode == R5C_JOURNAL_MODE_WRITE_THROUGH)
         return 0;
 
     if (sh->log_start == MaxSector) {
         BUG_ON(!list_empty(&sh->r5c));
         sh->log_start = io->log_start;
         spin_lock_irq(&log->stripe_in_journal_lock);
         list_add_tail(&sh->r5c,
                   &log->stripe_in_journal_list);
         spin_unlock_irq(&log->stripe_in_journal_lock);
         atomic_inc(&log->stripe_in_journal_count);
     }
     return 0;
 }
 
 /* add stripe to no_space_stripes, and then wake up reclaim */
 static inline void r5l_add_no_space_stripe(struct r5l_log *log,
                        struct stripe_head *sh)
 {
     spin_lock(&log->no_space_stripes_lock);
     list_add_tail(&sh->log_list, &log->no_space_stripes);
     spin_unlock(&log->no_space_stripes_lock);
 }
 
 /*
  * running in raid5d, where reclaim could wait for raid5d too (when it flushes
  * data from log to raid disks), so we shouldn't wait for reclaim here
  */
 int r5l_write_stripe(struct r5l_log *log, struct stripe_head *sh)
 {
     struct r5conf *conf = sh->raid_conf;
     int write_disks = 0;
     int data_pages, parity_pages;
     int reserve;
     int i;
     int ret = 0;
     bool wake_reclaim = false;
 
     if (!log)
         return -EAGAIN;
     /* Don't support stripe batch */
     if (sh->log_io || !test_bit(R5_Wantwrite, &sh->dev[sh->pd_idx].flags) ||
         test_bit(STRIPE_SYNCING, &sh->state)) {
         /* the stripe is written to log, we start writing it to raid */
         clear_bit(STRIPE_LOG_TRAPPED, &sh->state);
         return -EAGAIN;
     }
 
     WARN_ON(test_bit(STRIPE_R5C_CACHING, &sh->state));
 
     for (i = 0; i < sh->disks; i++) {
         void *addr;
 
         if (!test_bit(R5_Wantwrite, &sh->dev[i].flags) ||
             test_bit(R5_InJournal, &sh->dev[i].flags))
             continue;
 
         write_disks++;
         /* checksum is already calculated in last run */
         if (test_bit(STRIPE_LOG_TRAPPED, &sh->state))
             continue;
         addr = kmap_atomic(sh->dev[i].page);
         sh->dev[i].log_checksum = crc32c_le(log->uuid_checksum,
                             addr, PAGE_SIZE);
         kunmap_atomic(addr);
     }
     parity_pages = 1 + !!(sh->qd_idx >= 0);
     data_pages = write_disks - parity_pages;
 
     set_bit(STRIPE_LOG_TRAPPED, &sh->state);
     /*
      * The stripe must enter state machine again to finish the write, so
      * don't delay.
      */
     clear_bit(STRIPE_DELAYED, &sh->state);
     atomic_inc(&sh->count);
 
     mutex_lock(&log->io_mutex);
     /* meta + data */
     reserve = (1 + write_disks) << (PAGE_SHIFT - 9);
 
     if (log->r5c_journal_mode == R5C_JOURNAL_MODE_WRITE_THROUGH) {
         if (!r5l_has_free_space(log, reserve)) {
             r5l_add_no_space_stripe(log, sh);
             wake_reclaim = true;
         } else {
             ret = r5l_log_stripe(log, sh, data_pages, parity_pages);
             if (ret) {
                 spin_lock_irq(&log->io_list_lock);
                 list_add_tail(&sh->log_list,
                           &log->no_mem_stripes);
                 spin_unlock_irq(&log->io_list_lock);
             }
         }
     } else {  /* R5C_JOURNAL_MODE_WRITE_BACK */
         /*
          * log space critical, do not process stripes that are
          * not in cache yet (sh->log_start == MaxSector).
          */
         if (test_bit(R5C_LOG_CRITICAL, &conf->cache_state) &&
             sh->log_start == MaxSector) {
             r5l_add_no_space_stripe(log, sh);
             wake_reclaim = true;
             reserve = 0;
         } else if (!r5l_has_free_space(log, reserve)) {
             if (sh->log_start == log->last_checkpoint)
                 BUG();
             else
                 r5l_add_no_space_stripe(log, sh);
         } else {
             ret = r5l_log_stripe(log, sh, data_pages, parity_pages);
             if (ret) {
                 spin_lock_irq(&log->io_list_lock);
                 list_add_tail(&sh->log_list,
                           &log->no_mem_stripes);
                 spin_unlock_irq(&log->io_list_lock);
             }
         }
     }
 
     mutex_unlock(&log->io_mutex);
     if (wake_reclaim)
         r5l_wake_reclaim(log, reserve);
     return 0;
 }
 
 void r5l_write_stripe_run(struct r5l_log *log)
 {
     if (!log)
         return;
     mutex_lock(&log->io_mutex);
     r5l_submit_current_io(log);
     mutex_unlock(&log->io_mutex);
 }
 
 int r5l_handle_flush_request(struct r5l_log *log, struct bio *bio)
 {
     if (log->r5c_journal_mode == R5C_JOURNAL_MODE_WRITE_THROUGH) {
         /*
          * in write through (journal only)
          * we flush log disk cache first, then write stripe data to
          * raid disks. So if bio is finished, the log disk cache is
          * flushed already. The recovery guarantees we can recovery
          * the bio from log disk, so we don't need to flush again
          */
         if (bio->bi_iter.bi_size == 0) {
             bio_endio(bio);
             return 0;
         }
         bio->bi_opf &= ~REQ_PREFLUSH;
     } else {
         /* write back (with cache) */
         if (bio->bi_iter.bi_size == 0) {
             mutex_lock(&log->io_mutex);
             r5l_get_meta(log, 0);
             bio_list_add(&log->current_io->flush_barriers, bio);
             log->current_io->has_flush = 1;
             log->current_io->has_null_flush = 1;
             atomic_inc(&log->current_io->pending_stripe);
             r5l_submit_current_io(log);
             mutex_unlock(&log->io_mutex);
             return 0;
         }
     }
     return -EAGAIN;
 }
 
 /* This will run after log space is reclaimed */
 static void r5l_run_no_space_stripes(struct r5l_log *log)
 {
     struct stripe_head *sh;
 
     spin_lock(&log->no_space_stripes_lock);
     while (!list_empty(&log->no_space_stripes)) {
         sh = list_first_entry(&log->no_space_stripes,
                       struct stripe_head, log_list);
         list_del_init(&sh->log_list);
         set_bit(STRIPE_HANDLE, &sh->state);
         raid5_release_stripe(sh);
     }
     spin_unlock(&log->no_space_stripes_lock);
 }
 
 /*
  * calculate new last_checkpoint
  * for write through mode, returns log->next_checkpoint
  * for write back, returns log_start of first sh in stripe_in_journal_list
  */
 static sector_t r5c_calculate_new_cp(struct r5conf *conf)
 {
     struct stripe_head *sh;
     struct r5l_log *log = conf->log;
     sector_t new_cp;
     unsigned long flags;
 
     if (log->r5c_journal_mode == R5C_JOURNAL_MODE_WRITE_THROUGH)
         return log->next_checkpoint;
 
     spin_lock_irqsave(&log->stripe_in_journal_lock, flags);
     if (list_empty(&conf->log->stripe_in_journal_list)) {
         /* all stripes flushed */
         spin_unlock_irqrestore(&log->stripe_in_journal_lock, flags);
         return log->next_checkpoint;
     }
     sh = list_first_entry(&conf->log->stripe_in_journal_list,
                   struct stripe_head, r5c);
     new_cp = sh->log_start;
     spin_unlock_irqrestore(&log->stripe_in_journal_lock, flags);
     return new_cp;
 }
 
 static sector_t r5l_reclaimable_space(struct r5l_log *log)
 {
     struct r5conf *conf = log->rdev->mddev->private;
 
     return r5l_ring_distance(log, log->last_checkpoint,
                  r5c_calculate_new_cp(conf));
 }
 
 static void r5l_run_no_mem_stripe(struct r5l_log *log)
 {
     struct stripe_head *sh;
 
     lockdep_assert_held(&log->io_list_lock);
 
     if (!list_empty(&log->no_mem_stripes)) {
         sh = list_first_entry(&log->no_mem_stripes,
                       struct stripe_head, log_list);
         list_del_init(&sh->log_list);
         set_bit(STRIPE_HANDLE, &sh->state);
         raid5_release_stripe(sh);
     }
 }
 
 static bool r5l_complete_finished_ios(struct r5l_log *log)
 {
     struct r5l_io_unit *io, *next;
     bool found = false;
 
     lockdep_assert_held(&log->io_list_lock);
 
     list_for_each_entry_safe(io, next, &log->finished_ios, log_sibling) {
         /* don't change list order */
         if (io->state < IO_UNIT_STRIPE_END)
             break;
 
         log->next_checkpoint = io->log_start;
 
         list_del(&io->log_sibling);
         mempool_free(io, &log->io_pool);
         r5l_run_no_mem_stripe(log);
 
         found = true;
     }
 
     return found;
 }
 
 static void __r5l_stripe_write_finished(struct r5l_io_unit *io)
 {
     struct r5l_log *log = io->log;
     struct r5conf *conf = log->rdev->mddev->private;
     unsigned long flags;
 
     spin_lock_irqsave(&log->io_list_lock, flags);
     __r5l_set_io_unit_state(io, IO_UNIT_STRIPE_END);
 
     if (!r5l_complete_finished_ios(log)) {
         spin_unlock_irqrestore(&log->io_list_lock, flags);
         return;
     }
 
     if (r5l_reclaimable_space(log) > log->max_free_space ||
         test_bit(R5C_LOG_TIGHT, &conf->cache_state))
         r5l_wake_reclaim(log, 0);
 
     spin_unlock_irqrestore(&log->io_list_lock, flags);
     wake_up(&log->iounit_wait);
 }
 
 void r5l_stripe_write_finished(struct stripe_head *sh)
 {
     struct r5l_io_unit *io;
 
     io = sh->log_io;
     sh->log_io = NULL;
 
     if (io && atomic_dec_and_test(&io->pending_stripe))
         __r5l_stripe_write_finished(io);
 }
 
 static void r5l_log_flush_endio(struct bio *bio)
 {
     struct r5l_log *log = container_of(bio, struct r5l_log,
         flush_bio);
     unsigned long flags;
     struct r5l_io_unit *io;
 
     if (bio->bi_status)
         md_error(log->rdev->mddev, log->rdev);
 
     spin_lock_irqsave(&log->io_list_lock, flags);
     list_for_each_entry(io, &log->flushing_ios, log_sibling)
         r5l_io_run_stripes(io);
     list_splice_tail_init(&log->flushing_ios, &log->finished_ios);
     spin_unlock_irqrestore(&log->io_list_lock, flags);
 
     bio_uninit(bio);
 }
 
 /*
  * Starting dispatch IO to raid.
  * io_unit(meta) consists of a log. There is one situation we want to avoid. A
  * broken meta in the middle of a log causes recovery can't find meta at the
  * head of log. If operations require meta at the head persistent in log, we
  * must make sure meta before it persistent in log too. A case is:
  *
  * stripe data/parity is in log, we start write stripe to raid disks. stripe
  * data/parity must be persistent in log before we do the write to raid disks.
  *
  * The solution is we restrictly maintain io_unit list order. In this case, we
  * only write stripes of an io_unit to raid disks till the io_unit is the first
  * one whose data/parity is in log.
  */
 void r5l_flush_stripe_to_raid(struct r5l_log *log)
 {
     bool do_flush;
 
     if (!log || !log->need_cache_flush)
         return;
 
     spin_lock_irq(&log->io_list_lock);
     /* flush bio is running */
     if (!list_empty(&log->flushing_ios)) {
         spin_unlock_irq(&log->io_list_lock);
         return;
     }
     list_splice_tail_init(&log->io_end_ios, &log->flushing_ios);
     do_flush = !list_empty(&log->flushing_ios);
     spin_unlock_irq(&log->io_list_lock);
 
     if (!do_flush)
         return;
     bio_init(&log->flush_bio, log->rdev->bdev, NULL, 0,
           REQ_OP_WRITE | REQ_PREFLUSH);
     log->flush_bio.bi_end_io = r5l_log_flush_endio;
     submit_bio(&log->flush_bio);
 }
 
 static void r5l_write_super(struct r5l_log *log, sector_t cp);
 static void r5l_write_super_and_discard_space(struct r5l_log *log,
     sector_t end)
 {
     struct block_device *bdev = log->rdev->bdev;
     struct mddev *mddev;
 
     r5l_write_super(log, end);
 
     if (!bdev_max_discard_sectors(bdev))
         return;
 
     mddev = log->rdev->mddev;
     /*
      * Discard could zero data, so before discard we must make sure
      * superblock is updated to new log tail. Updating superblock (either
      * directly call md_update_sb() or depend on md thread) must hold
      * reconfig mutex. On the other hand, raid5_quiesce is called with
      * reconfig_mutex hold. The first step of raid5_quiesce() is waitting
      * for all IO finish, hence waitting for reclaim thread, while reclaim
      * thread is calling this function and waitting for reconfig mutex. So
      * there is a deadlock. We workaround this issue with a trylock.
      * FIXME: we could miss discard if we can't take reconfig mutex
      */
     set_mask_bits(&mddev->sb_flags, 0,
         BIT(MD_SB_CHANGE_DEVS) | BIT(MD_SB_CHANGE_PENDING));
     if (!mddev_trylock(mddev))
         return;
     md_update_sb(mddev, 1);
     mddev_unlock(mddev);
 
     /* discard IO error really doesn't matter, ignore it */
     if (log->last_checkpoint < end) {
         blkdev_issue_discard(bdev,
                 log->last_checkpoint + log->rdev->data_offset,
                 end - log->last_checkpoint, GFP_NOIO);
     } else {
         blkdev_issue_discard(bdev,
                 log->last_checkpoint + log->rdev->data_offset,
                 log->device_size - log->last_checkpoint,
                 GFP_NOIO);
         blkdev_issue_discard(bdev, log->rdev->data_offset, end,
                 GFP_NOIO);
     }
 }
 
 /*
  * r5c_flush_stripe moves stripe from cached list to handle_list. When called,
  * the stripe must be on r5c_cached_full_stripes or r5c_cached_partial_stripes.
  *
  * must hold conf->device_lock
  */
 static void r5c_flush_stripe(struct r5conf *conf, struct stripe_head *sh)
 {
     BUG_ON(list_empty(&sh->lru));
     BUG_ON(!test_bit(STRIPE_R5C_CACHING, &sh->state));
     BUG_ON(test_bit(STRIPE_HANDLE, &sh->state));
 
     /*
      * The stripe is not ON_RELEASE_LIST, so it is safe to call
      * raid5_release_stripe() while holding conf->device_lock
      */
     BUG_ON(test_bit(STRIPE_ON_RELEASE_LIST, &sh->state));
     lockdep_assert_held(&conf->device_lock);
 
     list_del_init(&sh->lru);
     atomic_inc(&sh->count);
 
     set_bit(STRIPE_HANDLE, &sh->state);
     atomic_inc(&conf->active_stripes);
     r5c_make_stripe_write_out(sh);
 
     if (test_bit(STRIPE_R5C_PARTIAL_STRIPE, &sh->state))
         atomic_inc(&conf->r5c_flushing_partial_stripes);
     else
         atomic_inc(&conf->r5c_flushing_full_stripes);
     raid5_release_stripe(sh);
 }
 
 /*
  * if num == 0, flush all full stripes
  * if num > 0, flush all full stripes. If less than num full stripes are
  *             flushed, flush some partial stripes until totally num stripes are
  *             flushed or there is no more cached stripes.
  */
 void r5c_flush_cache(struct r5conf *conf, int num)
 {
     int count;
     struct stripe_head *sh, *next;
 
     lockdep_assert_held(&conf->device_lock);
     if (!conf->log)
         return;
 
     count = 0;
     list_for_each_entry_safe(sh, next, &conf->r5c_full_stripe_list, lru) {
         r5c_flush_stripe(conf, sh);
         count++;
     }
 
     if (count >= num)
         return;
     list_for_each_entry_safe(sh, next,
                  &conf->r5c_partial_stripe_list, lru) {
         r5c_flush_stripe(conf, sh);
         if (++count >= num)
             break;
     }
 }
 
 static void r5c_do_reclaim(struct r5conf *conf)
 {
     struct r5l_log *log = conf->log;
     struct stripe_head *sh;
     int count = 0;
     unsigned long flags;
     int total_cached;
     int stripes_to_flush;
     int flushing_partial, flushing_full;
 
     if (!r5c_is_writeback(log))
         return;
 
     flushing_partial = atomic_read(&conf->r5c_flushing_partial_stripes);
     flushing_full = atomic_read(&conf->r5c_flushing_full_stripes);
     total_cached = atomic_read(&conf->r5c_cached_partial_stripes) +
         atomic_read(&conf->r5c_cached_full_stripes) -
         flushing_full - flushing_partial;
 
     if (total_cached > conf->min_nr_stripes * 3 / 4 ||
         atomic_read(&conf->empty_inactive_list_nr) > 0)
         /*
          * if stripe cache pressure high, flush all full stripes and
          * some partial stripes
          */
         stripes_to_flush = R5C_RECLAIM_STRIPE_GROUP;
     else if (total_cached > conf->min_nr_stripes * 1 / 2 ||
          atomic_read(&conf->r5c_cached_full_stripes) - flushing_full >
          R5C_FULL_STRIPE_FLUSH_BATCH(conf))
         /*
          * if stripe cache pressure moderate, or if there is many full
          * stripes,flush all full stripes
          */
         stripes_to_flush = 0;
     else
         /* no need to flush */
         stripes_to_flush = -1;
 
     if (stripes_to_flush >= 0) {
         spin_lock_irqsave(&conf->device_lock, flags);
         r5c_flush_cache(conf, stripes_to_flush);
         spin_unlock_irqrestore(&conf->device_lock, flags);
     }
 
     /* if log space is tight, flush stripes on stripe_in_journal_list */
     if (test_bit(R5C_LOG_TIGHT, &conf->cache_state)) {
         spin_lock_irqsave(&log->stripe_in_journal_lock, flags);
         spin_lock(&conf->device_lock);
         list_for_each_entry(sh, &log->stripe_in_journal_list, r5c) {
             /*
              * stripes on stripe_in_journal_list could be in any
              * state of the stripe_cache state machine. In this
              * case, we only want to flush stripe on
              * r5c_cached_full/partial_stripes. The following
              * condition makes sure the stripe is on one of the
              * two lists.
              */
             if (!list_empty(&sh->lru) &&
                 !test_bit(STRIPE_HANDLE, &sh->state) &&
                 atomic_read(&sh->count) == 0) {
                 r5c_flush_stripe(conf, sh);
                 if (count++ >= R5C_RECLAIM_STRIPE_GROUP)
                     break;
             }
         }
         spin_unlock(&conf->device_lock);
         spin_unlock_irqrestore(&log->stripe_in_journal_lock, flags);
     }
 
     if (!test_bit(R5C_LOG_CRITICAL, &conf->cache_state))
         r5l_run_no_space_stripes(log);
 
     md_wakeup_thread(conf->mddev->thread);
 }
 
 static void r5l_do_reclaim(struct r5l_log *log)
 {
     struct r5conf *conf = log->rdev->mddev->private;
     sector_t reclaim_target = xchg(&log->reclaim_target, 0);
     sector_t reclaimable;
     sector_t next_checkpoint;
     bool write_super;
 
     spin_lock_irq(&log->io_list_lock);
     write_super = r5l_reclaimable_space(log) > log->max_free_space ||
         reclaim_target != 0 || !list_empty(&log->no_space_stripes);
     /*
      * move proper io_unit to reclaim list. We should not change the order.
      * reclaimable/unreclaimable io_unit can be mixed in the list, we
      * shouldn't reuse space of an unreclaimable io_unit
      */
     while (1) {
         reclaimable = r5l_reclaimable_space(log);
         if (reclaimable >= reclaim_target ||
             (list_empty(&log->running_ios) &&
              list_empty(&log->io_end_ios) &&
              list_empty(&log->flushing_ios) &&
              list_empty(&log->finished_ios)))
             break;
 
         md_wakeup_thread(log->rdev->mddev->thread);
         wait_event_lock_irq(log->iounit_wait,
                     r5l_reclaimable_space(log) > reclaimable,
                     log->io_list_lock);
     }
 
     next_checkpoint = r5c_calculate_new_cp(conf);
     spin_unlock_irq(&log->io_list_lock);
 
     if (reclaimable == 0 || !write_super)
         return;
 
     /*
      * write_super will flush cache of each raid disk. We must write super
      * here, because the log area might be reused soon and we don't want to
      * confuse recovery
      */
     r5l_write_super_and_discard_space(log, next_checkpoint);
 
     mutex_lock(&log->io_mutex);
     log->last_checkpoint = next_checkpoint;
     r5c_update_log_state(log);
     mutex_unlock(&log->io_mutex);
 
     r5l_run_no_space_stripes(log);
 }
 
 static void r5l_reclaim_thread(struct md_thread *thread)
 {
     struct mddev *mddev = thread->mddev;
     struct r5conf *conf = mddev->private;
     struct r5l_log *log = conf->log;
 
     if (!log)
         return;
     r5c_do_reclaim(conf);
     r5l_do_reclaim(log);
 }
 
 void r5l_wake_reclaim(struct r5l_log *log, sector_t space)
 {
     unsigned long target;
     unsigned long new = (unsigned long)space; /* overflow in theory */
 
     if (!log)
         return;
     do {
         target = log->reclaim_target;
         if (new < target)
             return;
     } while (cmpxchg(&log->reclaim_target, target, new) != target);
     md_wakeup_thread(log->reclaim_thread);
 }
 
 void r5l_quiesce(struct r5l_log *log, int quiesce)
 {
     struct mddev *mddev;
 
     if (quiesce) {
         /* make sure r5l_write_super_and_discard_space exits */
         mddev = log->rdev->mddev;
         wake_up(&mddev->sb_wait);
         kthread_park(log->reclaim_thread->tsk);
         r5l_wake_reclaim(log, MaxSector);
         r5l_do_reclaim(log);
     } else
         kthread_unpark(log->reclaim_thread->tsk);
 }
 
 bool r5l_log_disk_error(struct r5conf *conf)
 {
     struct r5l_log *log = conf->log;
 
     /* don't allow write if journal disk is missing */
     if (!log)
         return test_bit(MD_HAS_JOURNAL, &conf->mddev->flags);
     else
         return test_bit(Faulty, &log->rdev->flags);
 }
 
 #define R5L_RECOVERY_PAGE_POOL_SIZE 256
 
 struct r5l_recovery_ctx {
     struct page *meta_page;     /* current meta */
     sector_t meta_total_blocks; /* total size of current meta and data */
     sector_t pos;           /* recovery position */
     u64 seq;            /* recovery position seq */
     int data_parity_stripes;    /* number of data_parity stripes */
     int data_only_stripes;      /* number of data_only stripes */
     struct list_head cached_list;
 
     /*
      * read ahead page pool (ra_pool)
      * in recovery, log is read sequentially. It is not efficient to
      * read every page with sync_page_io(). The read ahead page pool
      * reads multiple pages with one IO, so further log read can
      * just copy data from the pool.
      */
     struct page *ra_pool[R5L_RECOVERY_PAGE_POOL_SIZE];
     struct bio_vec ra_bvec[R5L_RECOVERY_PAGE_POOL_SIZE];
     sector_t pool_offset;   /* offset of first page in the pool */
     int total_pages;    /* total allocated pages */
     int valid_pages;    /* pages with valid data */
 };
 
 static int r5l_recovery_allocate_ra_pool(struct r5l_log *log,
                         struct r5l_recovery_ctx *ctx)
 {
     struct page *page;
 
     ctx->valid_pages = 0;
     ctx->total_pages = 0;
     while (ctx->total_pages < R5L_RECOVERY_PAGE_POOL_SIZE) {
         page = alloc_page(GFP_KERNEL);
 
         if (!page)
             break;
         ctx->ra_pool[ctx->total_pages] = page;
         ctx->total_pages += 1;
     }
 
     if (ctx->total_pages == 0)
         return -ENOMEM;
 
     ctx->pool_offset = 0;
     return 0;
 }
 
 static void r5l_recovery_free_ra_pool(struct r5l_log *log,
                     struct r5l_recovery_ctx *ctx)
 {
     int i;
 
     for (i = 0; i < ctx->total_pages; ++i)
         put_page(ctx->ra_pool[i]);
 }
 
 /*
  * fetch ctx->valid_pages pages from offset
  * In normal cases, ctx->valid_pages == ctx->total_pages after the call.
  * However, if the offset is close to the end of the journal device,
  * ctx->valid_pages could be smaller than ctx->total_pages
  */
 static int r5l_recovery_fetch_ra_pool(struct r5l_log *log,
                       struct r5l_recovery_ctx *ctx,
                       sector_t offset)
 {
     struct bio bio;
     int ret;
 
     bio_init(&bio, log->rdev->bdev, ctx->ra_bvec,
          R5L_RECOVERY_PAGE_POOL_SIZE, REQ_OP_READ);
     bio.bi_iter.bi_sector = log->rdev->data_offset + offset;
 
     ctx->valid_pages = 0;
     ctx->pool_offset = offset;
 
     while (ctx->valid_pages < ctx->total_pages) {
         __bio_add_page(&bio, ctx->ra_pool[ctx->valid_pages], PAGE_SIZE,
                    0);
         ctx->valid_pages += 1;
 
         offset = r5l_ring_add(log, offset, BLOCK_SECTORS);
 
         if (offset == 0)  /* reached end of the device */
             break;
     }
 
     ret = submit_bio_wait(&bio);
     bio_uninit(&bio);
     return ret;
 }
 
 /*
  * try read a page from the read ahead page pool, if the page is not in the
  * pool, call r5l_recovery_fetch_ra_pool
  */
 static int r5l_recovery_read_page(struct r5l_log *log,
                   struct r5l_recovery_ctx *ctx,
                   struct page *page,
                   sector_t offset)
 {
     int ret;
 
     if (offset < ctx->pool_offset ||
         offset >= ctx->pool_offset + ctx->valid_pages * BLOCK_SECTORS) {
         ret = r5l_recovery_fetch_ra_pool(log, ctx, offset);
         if (ret)
             return ret;
     }
 
     BUG_ON(offset < ctx->pool_offset ||
            offset >= ctx->pool_offset + ctx->valid_pages * BLOCK_SECTORS);
 
     memcpy(page_address(page),
            page_address(ctx->ra_pool[(offset - ctx->pool_offset) >>
                      BLOCK_SECTOR_SHIFT]),
            PAGE_SIZE);
     return 0;
 }
 
 static int r5l_recovery_read_meta_block(struct r5l_log *log,
                     struct r5l_recovery_ctx *ctx)
 {
     struct page *page = ctx->meta_page;
     struct r5l_meta_block *mb;
     u32 crc, stored_crc;
     int ret;
 
     ret = r5l_recovery_read_page(log, ctx, page, ctx->pos);
     if (ret != 0)
         return ret;
 
     mb = page_address(page);
     stored_crc = le32_to_cpu(mb->checksum);
     mb->checksum = 0;
 
     if (le32_to_cpu(mb->magic) != R5LOG_MAGIC ||
         le64_to_cpu(mb->seq) != ctx->seq ||
         mb->version != R5LOG_VERSION ||
         le64_to_cpu(mb->position) != ctx->pos)
         return -EINVAL;
 
     crc = crc32c_le(log->uuid_checksum, mb, PAGE_SIZE);
     if (stored_crc != crc)
         return -EINVAL;
 
     if (le32_to_cpu(mb->meta_size) > PAGE_SIZE)
         return -EINVAL;
 
     ctx->meta_total_blocks = BLOCK_SECTORS;
 
     return 0;
 }
 
 static void
 r5l_recovery_create_empty_meta_block(struct r5l_log *log,
                      struct page *page,
                      sector_t pos, u64 seq)
 {
     struct r5l_meta_block *mb;
 
     mb = page_address(page);
     clear_page(mb);
     mb->magic = cpu_to_le32(R5LOG_MAGIC);
     mb->version = R5LOG_VERSION;
     mb->meta_size = cpu_to_le32(sizeof(struct r5l_meta_block));
     mb->seq = cpu_to_le64(seq);
     mb->position = cpu_to_le64(pos);
 }
 
 static int r5l_log_write_empty_meta_block(struct r5l_log *log, sector_t pos,
                       u64 seq)
 {
     struct page *page;
     struct r5l_meta_block *mb;
 
     page = alloc_page(GFP_KERNEL);
     if (!page)
         return -ENOMEM;
     r5l_recovery_create_empty_meta_block(log, page, pos, seq);
     mb = page_address(page);
     mb->checksum = cpu_to_le32(crc32c_le(log->uuid_checksum,
                          mb, PAGE_SIZE));
     if (!sync_page_io(log->rdev, pos, PAGE_SIZE, page, REQ_OP_WRITE |
               REQ_SYNC | REQ_FUA, false)) {
         __free_page(page);
         return -EIO;
     }
     __free_page(page);
     return 0;
 }
 
 /*
  * r5l_recovery_load_data and r5l_recovery_load_parity uses flag R5_Wantwrite
  * to mark valid (potentially not flushed) data in the journal.
  *
  * We already verified checksum in r5l_recovery_verify_data_checksum_for_mb,
  * so there should not be any mismatch here.
  */
 static void r5l_recovery_load_data(struct r5l_log *log,
                    struct stripe_head *sh,
                    struct r5l_recovery_ctx *ctx,
                    struct r5l_payload_data_parity *payload,
                    sector_t log_offset)
 {
     struct mddev *mddev = log->rdev->mddev;
     struct r5conf *conf = mddev->private;
     int dd_idx;
 
     raid5_compute_sector(conf,
                  le64_to_cpu(payload->location), 0,
                  &dd_idx, sh);
     r5l_recovery_read_page(log, ctx, sh->dev[dd_idx].page, log_offset);
     sh->dev[dd_idx].log_checksum =
         le32_to_cpu(payload->checksum[0]);
     ctx->meta_total_blocks += BLOCK_SECTORS;
 
     set_bit(R5_Wantwrite, &sh->dev[dd_idx].flags);
     set_bit(STRIPE_R5C_CACHING, &sh->state);
 }
 
 static void r5l_recovery_load_parity(struct r5l_log *log,
                      struct stripe_head *sh,
                      struct r5l_recovery_ctx *ctx,
                      struct r5l_payload_data_parity *payload,
                      sector_t log_offset)
 {
     struct mddev *mddev = log->rdev->mddev;
     struct r5conf *conf = mddev->private;
 
     ctx->meta_total_blocks += BLOCK_SECTORS * conf->max_degraded;
     r5l_recovery_read_page(log, ctx, sh->dev[sh->pd_idx].page, log_offset);
     sh->dev[sh->pd_idx].log_checksum =
         le32_to_cpu(payload->checksum[0]);
     set_bit(R5_Wantwrite, &sh->dev[sh->pd_idx].flags);
 
     if (sh->qd_idx >= 0) {
         r5l_recovery_read_page(
             log, ctx, sh->dev[sh->qd_idx].page,
             r5l_ring_add(log, log_offset, BLOCK_SECTORS));
         sh->dev[sh->qd_idx].log_checksum =
             le32_to_cpu(payload->checksum[1]);
         set_bit(R5_Wantwrite, &sh->dev[sh->qd_idx].flags);
     }
     clear_bit(STRIPE_R5C_CACHING, &sh->state);
 }
 
 static void r5l_recovery_reset_stripe(struct stripe_head *sh)
 {
     int i;
 
     sh->state = 0;
     sh->log_start = MaxSector;
     for (i = sh->disks; i--; )
         sh->dev[i].flags = 0;
 }
 
 static void
 r5l_recovery_replay_one_stripe(struct r5conf *conf,
                    struct stripe_head *sh,
                    struct r5l_recovery_ctx *ctx)
 {
     struct md_rdev *rdev, *rrdev;
     int disk_index;
     int data_count = 0;
 
     for (disk_index = 0; disk_index < sh->disks; disk_index++) {
         if (!test_bit(R5_Wantwrite, &sh->dev[disk_index].flags))
             continue;
         if (disk_index == sh->qd_idx || disk_index == sh->pd_idx)
             continue;
         data_count++;
     }
 
     /*
      * stripes that only have parity must have been flushed
      * before the crash that we are now recovering from, so
      * there is nothing more to recovery.
      */
     if (data_count == 0)
         goto out;
 
     for (disk_index = 0; disk_index < sh->disks; disk_index++) {
         if (!test_bit(R5_Wantwrite, &sh->dev[disk_index].flags))
             continue;
 
         /* in case device is broken */
         rcu_read_lock();
         rdev = rcu_dereference(conf->disks[disk_index].rdev);
         if (rdev) {
             atomic_inc(&rdev->nr_pending);
             rcu_read_unlock();
             sync_page_io(rdev, sh->sector, PAGE_SIZE,
                      sh->dev[disk_index].page, REQ_OP_WRITE,
                      false);
             rdev_dec_pending(rdev, rdev->mddev);
             rcu_read_lock();
         }
         rrdev = rcu_dereference(conf->disks[disk_index].replacement);
         if (rrdev) {
             atomic_inc(&rrdev->nr_pending);
             rcu_read_unlock();
             sync_page_io(rrdev, sh->sector, PAGE_SIZE,
                      sh->dev[disk_index].page, REQ_OP_WRITE,
                      false);
             rdev_dec_pending(rrdev, rrdev->mddev);
             rcu_read_lock();
         }
         rcu_read_unlock();
     }
     ctx->data_parity_stripes++;
 out:
     r5l_recovery_reset_stripe(sh);
 }
 
 static struct stripe_head *
 r5c_recovery_alloc_stripe(
         struct r5conf *conf,
         sector_t stripe_sect,
         int noblock)
 {
     struct stripe_head *sh;
 
     sh = raid5_get_active_stripe(conf, stripe_sect, 0, noblock, 0);
     if (!sh)
         return NULL;  /* no more stripe available */
 
     r5l_recovery_reset_stripe(sh);
 
     return sh;
 }
 
 static struct stripe_head *
 r5c_recovery_lookup_stripe(struct list_head *list, sector_t sect)
 {
     struct stripe_head *sh;
 
     list_for_each_entry(sh, list, lru)
         if (sh->sector == sect)
             return sh;
     return NULL;
 }
 
 static void
 r5c_recovery_drop_stripes(struct list_head *cached_stripe_list,
               struct r5l_recovery_ctx *ctx)
 {
     struct stripe_head *sh, *next;
 
     list_for_each_entry_safe(sh, next, cached_stripe_list, lru) {
         r5l_recovery_reset_stripe(sh);
         list_del_init(&sh->lru);
         raid5_release_stripe(sh);
     }
 }
 
 static void
 r5c_recovery_replay_stripes(struct list_head *cached_stripe_list,
                 struct r5l_recovery_ctx *ctx)
 {
     struct stripe_head *sh, *next;
 
     list_for_each_entry_safe(sh, next, cached_stripe_list, lru)
         if (!test_bit(STRIPE_R5C_CACHING, &sh->state)) {
             r5l_recovery_replay_one_stripe(sh->raid_conf, sh, ctx);
             list_del_init(&sh->lru);
             raid5_release_stripe(sh);
         }
 }
 
 /* if matches return 0; otherwise return -EINVAL */
 static int
 r5l_recovery_verify_data_checksum(struct r5l_log *log,
                   struct r5l_recovery_ctx *ctx,
                   struct page *page,
                   sector_t log_offset, __le32 log_checksum)
 {
     void *addr;
     u32 checksum;
 
     r5l_recovery_read_page(log, ctx, page, log_offset);
     addr = kmap_atomic(page);
     checksum = crc32c_le(log->uuid_checksum, addr, PAGE_SIZE);
     kunmap_atomic(addr);
     return (le32_to_cpu(log_checksum) == checksum) ? 0 : -EINVAL;
 }
 
 /*
  * before loading data to stripe cache, we need verify checksum for all data,
  * if there is mismatch for any data page, we drop all data in the mata block
  */
 static int
 r5l_recovery_verify_data_checksum_for_mb(struct r5l_log *log,
                      struct r5l_recovery_ctx *ctx)
 {
     struct mddev *mddev = log->rdev->mddev;
     struct r5conf *conf = mddev->private;
     struct r5l_meta_block *mb = page_address(ctx->meta_page);
     sector_t mb_offset = sizeof(struct r5l_meta_block);
     sector_t log_offset = r5l_ring_add(log, ctx->pos, BLOCK_SECTORS);
     struct page *page;
     struct r5l_payload_data_parity *payload;
     struct r5l_payload_flush *payload_flush;
 
     page = alloc_page(GFP_KERNEL);
     if (!page)
         return -ENOMEM;
 
     while (mb_offset < le32_to_cpu(mb->meta_size)) {
         payload = (void *)mb + mb_offset;
         payload_flush = (void *)mb + mb_offset;
 
         if (le16_to_cpu(payload->header.type) == R5LOG_PAYLOAD_DATA) {
             if (r5l_recovery_verify_data_checksum(
                     log, ctx, page, log_offset,
                     payload->checksum[0]) < 0)
                 goto mismatch;
         } else if (le16_to_cpu(payload->header.type) == R5LOG_PAYLOAD_PARITY) {
             if (r5l_recovery_verify_data_checksum(
                     log, ctx, page, log_offset,
                     payload->checksum[0]) < 0)
                 goto mismatch;
             if (conf->max_degraded == 2 && /* q for RAID 6 */
                 r5l_recovery_verify_data_checksum(
                     log, ctx, page,
                     r5l_ring_add(log, log_offset,
                          BLOCK_SECTORS),
                     payload->checksum[1]) < 0)
                 goto mismatch;
         } else if (le16_to_cpu(payload->header.type) == R5LOG_PAYLOAD_FLUSH) {
             /* nothing to do for R5LOG_PAYLOAD_FLUSH here */
         } else /* not R5LOG_PAYLOAD_DATA/PARITY/FLUSH */
             goto mismatch;
 
         if (le16_to_cpu(payload->header.type) == R5LOG_PAYLOAD_FLUSH) {
             mb_offset += sizeof(struct r5l_payload_flush) +
                 le32_to_cpu(payload_flush->size);
         } else {
             /* DATA or PARITY payload */
             log_offset = r5l_ring_add(log, log_offset,
                           le32_to_cpu(payload->size));
             mb_offset += sizeof(struct r5l_payload_data_parity) +
                 sizeof(__le32) *
                 (le32_to_cpu(payload->size) >> (PAGE_SHIFT - 9));
         }
 
     }
 
     put_page(page);
     return 0;
 
 mismatch:
     put_page(page);
     return -EINVAL;
 }
 
 /*
  * Analyze all data/parity pages in one meta block
  * Returns:
  * 0 for success
  * -EINVAL for unknown playload type
  * -EAGAIN for checksum mismatch of data page
  * -ENOMEM for run out of memory (alloc_page failed or run out of stripes)
  */
 static int
 r5c_recovery_analyze_meta_block(struct r5l_log *log,
                 struct r5l_recovery_ctx *ctx,
                 struct list_head *cached_stripe_list)
 {
     struct mddev *mddev = log->rdev->mddev;
     struct r5conf *conf = mddev->private;
     struct r5l_meta_block *mb;
     struct r5l_payload_data_parity *payload;
     struct r5l_payload_flush *payload_flush;
     int mb_offset;
     sector_t log_offset;
     sector_t stripe_sect;
     struct stripe_head *sh;
     int ret;
 
     /*
      * for mismatch in data blocks, we will drop all data in this mb, but
      * we will still read next mb for other data with FLUSH flag, as
      * io_unit could finish out of order.
      */
     ret = r5l_recovery_verify_data_checksum_for_mb(log, ctx);
     if (ret == -EINVAL)
         return -EAGAIN;
     else if (ret)
         return ret;   /* -ENOMEM duo to alloc_page() failed */
 
     mb = page_address(ctx->meta_page);
     mb_offset = sizeof(struct r5l_meta_block);
     log_offset = r5l_ring_add(log, ctx->pos, BLOCK_SECTORS);
 
     while (mb_offset < le32_to_cpu(mb->meta_size)) {
         int dd;
 
         payload = (void *)mb + mb_offset;
         payload_flush = (void *)mb + mb_offset;
 
         if (le16_to_cpu(payload->header.type) == R5LOG_PAYLOAD_FLUSH) {
             int i, count;
 
             count = le32_to_cpu(payload_flush->size) / sizeof(__le64);
             for (i = 0; i < count; ++i) {
                 stripe_sect = le64_to_cpu(payload_flush->flush_stripes[i]);
                 sh = r5c_recovery_lookup_stripe(cached_stripe_list,
                                 stripe_sect);
                 if (sh) {
                     WARN_ON(test_bit(STRIPE_R5C_CACHING, &sh->state));
                     r5l_recovery_reset_stripe(sh);
                     list_del_init(&sh->lru);
                     raid5_release_stripe(sh);
                 }
             }
 
             mb_offset += sizeof(struct r5l_payload_flush) +
                 le32_to_cpu(payload_flush->size);
             continue;
         }
 
         /* DATA or PARITY payload */
         stripe_sect = (le16_to_cpu(payload->header.type) == R5LOG_PAYLOAD_DATA) ?
             raid5_compute_sector(
                 conf, le64_to_cpu(payload->location), 0, &dd,
                 NULL)
             : le64_to_cpu(payload->location);
 
         sh = r5c_recovery_lookup_stripe(cached_stripe_list,
                         stripe_sect);
 
         if (!sh) {
             sh = r5c_recovery_alloc_stripe(conf, stripe_sect, 1);
             /*
              * cannot get stripe from raid5_get_active_stripe
              * try replay some stripes
              */
             if (!sh) {
                 r5c_recovery_replay_stripes(
                     cached_stripe_list, ctx);
                 sh = r5c_recovery_alloc_stripe(
                     conf, stripe_sect, 1);
             }
             if (!sh) {
                 int new_size = conf->min_nr_stripes * 2;
                 pr_debug("md/raid:%s: Increasing stripe cache size to %d to recovery data on journal.\n",
                     mdname(mddev),
                     new_size);
                 ret = raid5_set_cache_size(mddev, new_size);
                 if (conf->min_nr_stripes <= new_size / 2) {
                     pr_err("md/raid:%s: Cannot increase cache size, ret=%d, new_size=%d, min_nr_stripes=%d, max_nr_stripes=%d\n",
                         mdname(mddev),
                         ret,
                         new_size,
                         conf->min_nr_stripes,
                         conf->max_nr_stripes);
                     return -ENOMEM;
                 }
                 sh = r5c_recovery_alloc_stripe(
                     conf, stripe_sect, 0);
             }
             if (!sh) {
                 pr_err("md/raid:%s: Cannot get enough stripes due to memory pressure. Recovery failed.\n",
                     mdname(mddev));
                 return -ENOMEM;
             }
             list_add_tail(&sh->lru, cached_stripe_list);
         }
 
         if (le16_to_cpu(payload->header.type) == R5LOG_PAYLOAD_DATA) {
             if (!test_bit(STRIPE_R5C_CACHING, &sh->state) &&
                 test_bit(R5_Wantwrite, &sh->dev[sh->pd_idx].flags)) {
                 r5l_recovery_replay_one_stripe(conf, sh, ctx);
                 list_move_tail(&sh->lru, cached_stripe_list);
             }
             r5l_recovery_load_data(log, sh, ctx, payload,
                            log_offset);
         } else if (le16_to_cpu(payload->header.type) == R5LOG_PAYLOAD_PARITY)
             r5l_recovery_load_parity(log, sh, ctx, payload,
                          log_offset);
         else
             return -EINVAL;
 
         log_offset = r5l_ring_add(log, log_offset,
                       le32_to_cpu(payload->size));
 
         mb_offset += sizeof(struct r5l_payload_data_parity) +
             sizeof(__le32) *
             (le32_to_cpu(payload->size) >> (PAGE_SHIFT - 9));
     }
 
     return 0;
 }
 
 /*
  * Load the stripe into cache. The stripe will be written out later by
  * the stripe cache state machine.
  */
 static void r5c_recovery_load_one_stripe(struct r5l_log *log,
                      struct stripe_head *sh)
 {
     struct r5dev *dev;
     int i;
 
     for (i = sh->disks; i--; ) {
         dev = sh->dev + i;
         if (test_and_clear_bit(R5_Wantwrite, &dev->flags)) {
             set_bit(R5_InJournal, &dev->flags);
             set_bit(R5_UPTODATE, &dev->flags);
         }
     }
 }
 
 /*
  * Scan through the log for all to-be-flushed data
  *
  * For stripes with data and parity, namely Data-Parity stripe
  * (STRIPE_R5C_CACHING == 0), we simply replay all the writes.
  *
  * For stripes with only data, namely Data-Only stripe
  * (STRIPE_R5C_CACHING == 1), we load them to stripe cache state machine.
  *
  * For a stripe, if we see data after parity, we should discard all previous
  * data and parity for this stripe, as these data are already flushed to
  * the array.
  *
  * At the end of the scan, we return the new journal_tail, which points to
  * first data-only stripe on the journal device, or next invalid meta block.
  */
 static int r5c_recovery_flush_log(struct r5l_log *log,
                   struct r5l_recovery_ctx *ctx)
 {
     struct stripe_head *sh;
     int ret = 0;
 
     /* scan through the log */
     while (1) {
         if (r5l_recovery_read_meta_block(log, ctx))
             break;
 
         ret = r5c_recovery_analyze_meta_block(log, ctx,
                               &ctx->cached_list);
         /*
          * -EAGAIN means mismatch in data block, in this case, we still
          * try scan the next metablock
          */
         if (ret && ret != -EAGAIN)
             break;   /* ret == -EINVAL or -ENOMEM */
         ctx->seq++;
         ctx->pos = r5l_ring_add(log, ctx->pos, ctx->meta_total_blocks);
     }
 
     if (ret == -ENOMEM) {
         r5c_recovery_drop_stripes(&ctx->cached_list, ctx);
         return ret;
     }
 
     /* replay data-parity stripes */
     r5c_recovery_replay_stripes(&ctx->cached_list, ctx);
 
     /* load data-only stripes to stripe cache */
     list_for_each_entry(sh, &ctx->cached_list, lru) {
         WARN_ON(!test_bit(STRIPE_R5C_CACHING, &sh->state));
         r5c_recovery_load_one_stripe(log, sh);
         ctx->data_only_stripes++;
     }
 
     return 0;
 }
 
 /*
  * we did a recovery. Now ctx.pos points to an invalid meta block. New
  * log will start here. but we can't let superblock point to last valid
  * meta block. The log might looks like:
  * | meta 1| meta 2| meta 3|
  * meta 1 is valid, meta 2 is invalid. meta 3 could be valid. If
  * superblock points to meta 1, we write a new valid meta 2n.  if crash
  * happens again, new recovery will start from meta 1. Since meta 2n is
  * valid now, recovery will think meta 3 is valid, which is wrong.
  * The solution is we create a new meta in meta2 with its seq == meta
  * 1's seq + 10000 and let superblock points to meta2. The same recovery
  * will not think meta 3 is a valid meta, because its seq doesn't match
  */
 
 /*
  * Before recovery, the log looks like the following
  *
  *   ---------------------------------------------
  *   |           valid log        | invalid log  |
  *   ---------------------------------------------
  *   ^
  *   |- log->last_checkpoint
  *   |- log->last_cp_seq
  *
  * Now we scan through the log until we see invalid entry
  *
  *   ---------------------------------------------
  *   |           valid log        | invalid log  |
  *   ---------------------------------------------
  *   ^                            ^
  *   |- log->last_checkpoint      |- ctx->pos
  *   |- log->last_cp_seq          |- ctx->seq
  *
  * From this point, we need to increase seq number by 10 to avoid
  * confusing next recovery.
  *
  *   ---------------------------------------------
  *   |           valid log        | invalid log  |
  *   ---------------------------------------------
  *   ^                              ^
  *   |- log->last_checkpoint        |- ctx->pos+1
  *   |- log->last_cp_seq            |- ctx->seq+10001
  *
  * However, it is not safe to start the state machine yet, because data only
  * parities are not yet secured in RAID. To save these data only parities, we
  * rewrite them from seq+11.
  *
  *   -----------------------------------------------------------------
  *   |           valid log        | data only stripes | invalid log  |
  *   -----------------------------------------------------------------
  *   ^                                                ^
  *   |- log->last_checkpoint                          |- ctx->pos+n
  *   |- log->last_cp_seq                              |- ctx->seq+10000+n
  *
  * If failure happens again during this process, the recovery can safe start
  * again from log->last_checkpoint.
  *
  * Once data only stripes are rewritten to journal, we move log_tail
  *
  *   -----------------------------------------------------------------
  *   |     old log        |    data only stripes    | invalid log  |
  *   -----------------------------------------------------------------
  *                        ^                         ^
  *                        |- log->last_checkpoint   |- ctx->pos+n
  *                        |- log->last_cp_seq       |- ctx->seq+10000+n
  *
  * Then we can safely start the state machine. If failure happens from this
  * point on, the recovery will start from new log->last_checkpoint.
  */
 static int
 r5c_recovery_rewrite_data_only_stripes(struct r5l_log *log,
                        struct r5l_recovery_ctx *ctx)
 {
     struct stripe_head *sh;
     struct mddev *mddev = log->rdev->mddev;
     struct page *page;
     sector_t next_checkpoint = MaxSector;
 
     page = alloc_page(GFP_KERNEL);
     if (!page) {
         pr_err("md/raid:%s: cannot allocate memory to rewrite data only stripes\n",
                mdname(mddev));
         return -ENOMEM;
     }
 
     WARN_ON(list_empty(&ctx->cached_list));
 
     list_for_each_entry(sh, &ctx->cached_list, lru) {
         struct r5l_meta_block *mb;
         int i;
         int offset;
         sector_t write_pos;
 
         WARN_ON(!test_bit(STRIPE_R5C_CACHING, &sh->state));
         r5l_recovery_create_empty_meta_block(log, page,
                              ctx->pos, ctx->seq);
         mb = page_address(page);
         offset = le32_to_cpu(mb->meta_size);
         write_pos = r5l_ring_add(log, ctx->pos, BLOCK_SECTORS);
 
         for (i = sh->disks; i--; ) {
             struct r5dev *dev = &sh->dev[i];
             struct r5l_payload_data_parity *payload;
             void *addr;
 
             if (test_bit(R5_InJournal, &dev->flags)) {
                 payload = (void *)mb + offset;
                 payload->header.type = cpu_to_le16(
                     R5LOG_PAYLOAD_DATA);
                 payload->size = cpu_to_le32(BLOCK_SECTORS);
                 payload->location = cpu_to_le64(
                     raid5_compute_blocknr(sh, i, 0));
                 addr = kmap_atomic(dev->page);
                 payload->checksum[0] = cpu_to_le32(
                     crc32c_le(log->uuid_checksum, addr,
                           PAGE_SIZE));
                 kunmap_atomic(addr);
                 sync_page_io(log->rdev, write_pos, PAGE_SIZE,
                          dev->page, REQ_OP_WRITE, false);
                 write_pos = r5l_ring_add(log, write_pos,
                              BLOCK_SECTORS);
                 offset += sizeof(__le32) +
                     sizeof(struct r5l_payload_data_parity);
 
             }
         }
         mb->meta_size = cpu_to_le32(offset);
         mb->checksum = cpu_to_le32(crc32c_le(log->uuid_checksum,
                              mb, PAGE_SIZE));
         sync_page_io(log->rdev, ctx->pos, PAGE_SIZE, page,
                  REQ_OP_WRITE | REQ_SYNC | REQ_FUA, false);
         sh->log_start = ctx->pos;
         list_add_tail(&sh->r5c, &log->stripe_in_journal_list);
         atomic_inc(&log->stripe_in_journal_count);
         ctx->pos = write_pos;
         ctx->seq += 1;
         next_checkpoint = sh->log_start;
     }
     log->next_checkpoint = next_checkpoint;
     __free_page(page);
     return 0;
 }
 
 static void r5c_recovery_flush_data_only_stripes(struct r5l_log *log,
                          struct r5l_recovery_ctx *ctx)
 {
     struct mddev *mddev = log->rdev->mddev;
     struct r5conf *conf = mddev->private;
     struct stripe_head *sh, *next;
     bool cleared_pending = false;
 
     if (ctx->data_only_stripes == 0)
         return;
 
     if (test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags)) {
         cleared_pending = true;
         clear_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags);
     }
     log->r5c_journal_mode = R5C_JOURNAL_MODE_WRITE_BACK;
 
     list_for_each_entry_safe(sh, next, &ctx->cached_list, lru) {
         r5c_make_stripe_write_out(sh);
         set_bit(STRIPE_HANDLE, &sh->state);
         list_del_init(&sh->lru);
         raid5_release_stripe(sh);
     }
 
     /* reuse conf->wait_for_quiescent in recovery */
     wait_event(conf->wait_for_quiescent,
            atomic_read(&conf->active_stripes) == 0);
 
     log->r5c_journal_mode = R5C_JOURNAL_MODE_WRITE_THROUGH;
     if (cleared_pending)
         set_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags);
 }
 
 static int r5l_recovery_log(struct r5l_log *log)
 {
     struct mddev *mddev = log->rdev->mddev;
     struct r5l_recovery_ctx *ctx;
     int ret;
     sector_t pos;
 
     ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
     if (!ctx)
         return -ENOMEM;
 
     ctx->pos = log->last_checkpoint;
     ctx->seq = log->last_cp_seq;
     INIT_LIST_HEAD(&ctx->cached_list);
     ctx->meta_page = alloc_page(GFP_KERNEL);
 
     if (!ctx->meta_page) {
         ret =  -ENOMEM;
         goto meta_page;
     }
 
     if (r5l_recovery_allocate_ra_pool(log, ctx) != 0) {
         ret = -ENOMEM;
         goto ra_pool;
     }
 
     ret = r5c_recovery_flush_log(log, ctx);
 
     if (ret)
         goto error;
 
     pos = ctx->pos;
     ctx->seq += 10000;
 
     if ((ctx->data_only_stripes == 0) && (ctx->data_parity_stripes == 0))
         pr_info("md/raid:%s: starting from clean shutdown\n",
              mdname(mddev));
     else
         pr_info("md/raid:%s: recovering %d data-only stripes and %d data-parity stripes\n",
              mdname(mddev), ctx->data_only_stripes,
              ctx->data_parity_stripes);
 
     if (ctx->data_only_stripes == 0) {
         log->next_checkpoint = ctx->pos;
         r5l_log_write_empty_meta_block(log, ctx->pos, ctx->seq++);
         ctx->pos = r5l_ring_add(log, ctx->pos, BLOCK_SECTORS);
     } else if (r5c_recovery_rewrite_data_only_stripes(log, ctx)) {
         pr_err("md/raid:%s: failed to rewrite stripes to journal\n",
                mdname(mddev));
         ret =  -EIO;
         goto error;
     }
 
     log->log_start = ctx->pos;
     log->seq = ctx->seq;
     log->last_checkpoint = pos;
     r5l_write_super(log, pos);
 
     r5c_recovery_flush_data_only_stripes(log, ctx);
     ret = 0;
 error:
     r5l_recovery_free_ra_pool(log, ctx);
 ra_pool:
     __free_page(ctx->meta_page);
 meta_page:
     kfree(ctx);
     return ret;
 }
 
 static void r5l_write_super(struct r5l_log *log, sector_t cp)
 {
     struct mddev *mddev = log->rdev->mddev;
 
     log->rdev->journal_tail = cp;
     set_bit(MD_SB_CHANGE_DEVS, &mddev->sb_flags);
 }
 
 static ssize_t r5c_journal_mode_show(struct mddev *mddev, char *page)
 {
     struct r5conf *conf;
     int ret;
 
     ret = mddev_lock(mddev);
     if (ret)
         return ret;
 
     conf = mddev->private;
     if (!conf || !conf->log)
         goto out_unlock;
 
     switch (conf->log->r5c_journal_mode) {
     case R5C_JOURNAL_MODE_WRITE_THROUGH:
         ret = snprintf(
             page, PAGE_SIZE, "[%s] %s\n",
             r5c_journal_mode_str[R5C_JOURNAL_MODE_WRITE_THROUGH],
             r5c_journal_mode_str[R5C_JOURNAL_MODE_WRITE_BACK]);
         break;
     case R5C_JOURNAL_MODE_WRITE_BACK:
         ret = snprintf(
             page, PAGE_SIZE, "%s [%s]\n",
             r5c_journal_mode_str[R5C_JOURNAL_MODE_WRITE_THROUGH],
             r5c_journal_mode_str[R5C_JOURNAL_MODE_WRITE_BACK]);
         break;
     default:
         ret = 0;
     }
 
 out_unlock:
     mddev_unlock(mddev);
     return ret;
 }
 
 /*
  * Set journal cache mode on @mddev (external API initially needed by dm-raid).
  *
  * @mode as defined in 'enum r5c_journal_mode'.
  *
  */
 int r5c_journal_mode_set(struct mddev *mddev, int mode)
 {
     struct r5conf *conf;
 
     if (mode < R5C_JOURNAL_MODE_WRITE_THROUGH ||
         mode > R5C_JOURNAL_MODE_WRITE_BACK)
         return -EINVAL;
 
     conf = mddev->private;
     if (!conf || !conf->log)
         return -ENODEV;
 
     if (raid5_calc_degraded(conf) > 0 &&
         mode == R5C_JOURNAL_MODE_WRITE_BACK)
         return -EINVAL;
 
     mddev_suspend(mddev);
     conf->log->r5c_journal_mode = mode;
     mddev_resume(mddev);
 
     pr_debug("md/raid:%s: setting r5c cache mode to %d: %s\n",
          mdname(mddev), mode, r5c_journal_mode_str[mode]);
     return 0;
 }
 EXPORT_SYMBOL(r5c_journal_mode_set);
 
 static ssize_t r5c_journal_mode_store(struct mddev *mddev,
                       const char *page, size_t length)
 {
     int mode = ARRAY_SIZE(r5c_journal_mode_str);
     size_t len = length;
     int ret;
 
     if (len < 2)
         return -EINVAL;
 
     if (page[len - 1] == '\n')
         len--;
 
     while (mode--)
         if (strlen(r5c_journal_mode_str[mode]) == len &&
             !strncmp(page, r5c_journal_mode_str[mode], len))
             break;
     ret = mddev_lock(mddev);
     if (ret)
         return ret;
     ret = r5c_journal_mode_set(mddev, mode);
     mddev_unlock(mddev);
     return ret ?: length;
 }
 
 struct md_sysfs_entry
 r5c_journal_mode = __ATTR(journal_mode, 0644,
               r5c_journal_mode_show, r5c_journal_mode_store);
 
 /*
  * Try handle write operation in caching phase. This function should only
  * be called in write-back mode.
  *
  * If all outstanding writes can be handled in caching phase, returns 0
  * If writes requires write-out phase, call r5c_make_stripe_write_out()
  * and returns -EAGAIN
  */
 int r5c_try_caching_write(struct r5conf *conf,
               struct stripe_head *sh,
               struct stripe_head_state *s,
               int disks)
 {
     struct r5l_log *log = conf->log;
     int i;
     struct r5dev *dev;
     int to_cache = 0;
     void __rcu **pslot;
     sector_t tree_index;
     int ret;
     uintptr_t refcount;
 
     BUG_ON(!r5c_is_writeback(log));
 
     if (!test_bit(STRIPE_R5C_CACHING, &sh->state)) {
         /*
          * There are two different scenarios here:
          *  1. The stripe has some data cached, and it is sent to
          *     write-out phase for reclaim
          *  2. The stripe is clean, and this is the first write
          *
          * For 1, return -EAGAIN, so we continue with
          * handle_stripe_dirtying().
          *
          * For 2, set STRIPE_R5C_CACHING and continue with caching
          * write.
          */
 
         /* case 1: anything injournal or anything in written */
         if (s->injournal > 0 || s->written > 0)
             return -EAGAIN;
         /* case 2 */
         set_bit(STRIPE_R5C_CACHING, &sh->state);
     }
 
     /*
      * When run in degraded mode, array is set to write-through mode.
      * This check helps drain pending write safely in the transition to
      * write-through mode.
      *
      * When a stripe is syncing, the write is also handled in write
      * through mode.
      */
     if (s->failed || test_bit(STRIPE_SYNCING, &sh->state)) {
         r5c_make_stripe_write_out(sh);
         return -EAGAIN;
     }
 
     for (i = disks; i--; ) {
         dev = &sh->dev[i];
         /* if non-overwrite, use writing-out phase */
         if (dev->towrite && !test_bit(R5_OVERWRITE, &dev->flags) &&
             !test_bit(R5_InJournal, &dev->flags)) {
             r5c_make_stripe_write_out(sh);
             return -EAGAIN;
         }
     }
 
     /* if the stripe is not counted in big_stripe_tree, add it now */
     if (!test_bit(STRIPE_R5C_PARTIAL_STRIPE, &sh->state) &&
         !test_bit(STRIPE_R5C_FULL_STRIPE, &sh->state)) {
         tree_index = r5c_tree_index(conf, sh->sector);
         spin_lock(&log->tree_lock);
         pslot = radix_tree_lookup_slot(&log->big_stripe_tree,
                            tree_index);
         if (pslot) {
             refcount = (uintptr_t)radix_tree_deref_slot_protected(
                 pslot, &log->tree_lock) >>
                 R5C_RADIX_COUNT_SHIFT;
             radix_tree_replace_slot(
                 &log->big_stripe_tree, pslot,
                 (void *)((refcount + 1) << R5C_RADIX_COUNT_SHIFT));
         } else {
             /*
              * this radix_tree_insert can fail safely, so no
              * need to call radix_tree_preload()
              */
             ret = radix_tree_insert(
                 &log->big_stripe_tree, tree_index,
                 (void *)(1 << R5C_RADIX_COUNT_SHIFT));
             if (ret) {
                 spin_unlock(&log->tree_lock);
                 r5c_make_stripe_write_out(sh);
                 return -EAGAIN;
             }
         }
         spin_unlock(&log->tree_lock);
 
         /*
          * set STRIPE_R5C_PARTIAL_STRIPE, this shows the stripe is
          * counted in the radix tree
          */
         set_bit(STRIPE_R5C_PARTIAL_STRIPE, &sh->state);
         atomic_inc(&conf->r5c_cached_partial_stripes);
     }
 
     for (i = disks; i--; ) {
         dev = &sh->dev[i];
         if (dev->towrite) {
             set_bit(R5_Wantwrite, &dev->flags);
             set_bit(R5_Wantdrain, &dev->flags);
             set_bit(R5_LOCKED, &dev->flags);
             to_cache++;
         }
     }
 
     if (to_cache) {
         set_bit(STRIPE_OP_BIODRAIN, &s->ops_request);
         /*
          * set STRIPE_LOG_TRAPPED, which triggers r5c_cache_data()
          * in ops_run_io(). STRIPE_LOG_TRAPPED will be cleared in
          * r5c_handle_data_cached()
          */
         set_bit(STRIPE_LOG_TRAPPED, &sh->state);
     }
 
     return 0;
 }
 
 /*
  * free extra pages (orig_page) we allocated for prexor
  */
 void r5c_release_extra_page(struct stripe_head *sh)
 {
     struct r5conf *conf = sh->raid_conf;
     int i;
     bool using_disk_info_extra_page;
 
     using_disk_info_extra_page =
         sh->dev[0].orig_page == conf->disks[0].extra_page;
 
     for (i = sh->disks; i--; )
         if (sh->dev[i].page != sh->dev[i].orig_page) {
             struct page *p = sh->dev[i].orig_page;
 
             sh->dev[i].orig_page = sh->dev[i].page;
             clear_bit(R5_OrigPageUPTDODATE, &sh->dev[i].flags);
 
             if (!using_disk_info_extra_page)
                 put_page(p);
         }
 
     if (using_disk_info_extra_page) {
         clear_bit(R5C_EXTRA_PAGE_IN_USE, &conf->cache_state);
         md_wakeup_thread(conf->mddev->thread);
     }
 }
 
 void r5c_use_extra_page(struct stripe_head *sh)
 {
     struct r5conf *conf = sh->raid_conf;
     int i;
     struct r5dev *dev;
 
     for (i = sh->disks; i--; ) {
         dev = &sh->dev[i];
         if (dev->orig_page != dev->page)
             put_page(dev->orig_page);
         dev->orig_page = conf->disks[i].extra_page;
     }
 }
 
 /*
  * clean up the stripe (clear R5_InJournal for dev[pd_idx] etc.) after the
  * stripe is committed to RAID disks.
  */
 void r5c_finish_stripe_write_out(struct r5conf *conf,
                  struct stripe_head *sh,
                  struct stripe_head_state *s)
 {
     struct r5l_log *log = conf->log;
     int i;
     int do_wakeup = 0;
     sector_t tree_index;
     void __rcu **pslot;
     uintptr_t refcount;
 
     if (!log || !test_bit(R5_InJournal, &sh->dev[sh->pd_idx].flags))
         return;
 
     WARN_ON(test_bit(STRIPE_R5C_CACHING, &sh->state));
     clear_bit(R5_InJournal, &sh->dev[sh->pd_idx].flags);
 
     if (log->r5c_journal_mode == R5C_JOURNAL_MODE_WRITE_THROUGH)
         return;
 
     for (i = sh->disks; i--; ) {
         clear_bit(R5_InJournal, &sh->dev[i].flags);
         if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
             do_wakeup = 1;
     }
 
     /*
      * analyse_stripe() runs before r5c_finish_stripe_write_out(),
      * We updated R5_InJournal, so we also update s->injournal.
      */
     s->injournal = 0;
 
     if (test_and_clear_bit(STRIPE_FULL_WRITE, &sh->state))
         if (atomic_dec_and_test(&conf->pending_full_writes))
             md_wakeup_thread(conf->mddev->thread);
 
     if (do_wakeup)
         wake_up(&conf->wait_for_overlap);
 
     spin_lock_irq(&log->stripe_in_journal_lock);
     list_del_init(&sh->r5c);
     spin_unlock_irq(&log->stripe_in_journal_lock);
     sh->log_start = MaxSector;
 
     atomic_dec(&log->stripe_in_journal_count);
     r5c_update_log_state(log);
 
     /* stop counting this stripe in big_stripe_tree */
     if (test_bit(STRIPE_R5C_PARTIAL_STRIPE, &sh->state) ||
         test_bit(STRIPE_R5C_FULL_STRIPE, &sh->state)) {
         tree_index = r5c_tree_index(conf, sh->sector);
         spin_lock(&log->tree_lock);
         pslot = radix_tree_lookup_slot(&log->big_stripe_tree,
                            tree_index);
         BUG_ON(pslot == NULL);
         refcount = (uintptr_t)radix_tree_deref_slot_protected(
             pslot, &log->tree_lock) >>
             R5C_RADIX_COUNT_SHIFT;
         if (refcount == 1)
             radix_tree_delete(&log->big_stripe_tree, tree_index);
         else
             radix_tree_replace_slot(
                 &log->big_stripe_tree, pslot,
                 (void *)((refcount - 1) << R5C_RADIX_COUNT_SHIFT));
         spin_unlock(&log->tree_lock);
     }
 
     if (test_and_clear_bit(STRIPE_R5C_PARTIAL_STRIPE, &sh->state)) {
         BUG_ON(atomic_read(&conf->r5c_cached_partial_stripes) == 0);
         atomic_dec(&conf->r5c_flushing_partial_stripes);
         atomic_dec(&conf->r5c_cached_partial_stripes);
     }
 
     if (test_and_clear_bit(STRIPE_R5C_FULL_STRIPE, &sh->state)) {
         BUG_ON(atomic_read(&conf->r5c_cached_full_stripes) == 0);
         atomic_dec(&conf->r5c_flushing_full_stripes);
         atomic_dec(&conf->r5c_cached_full_stripes);
     }
 
     r5l_append_flush_payload(log, sh->sector);
     /* stripe is flused to raid disks, we can do resync now */
     if (test_bit(STRIPE_SYNC_REQUESTED, &sh->state))
         set_bit(STRIPE_HANDLE, &sh->state);
 }
 
 int r5c_cache_data(struct r5l_log *log, struct stripe_head *sh)
 {
     struct r5conf *conf = sh->raid_conf;
     int pages = 0;
     int reserve;
     int i;
     int ret = 0;
 
     BUG_ON(!log);
 
     for (i = 0; i < sh->disks; i++) {
         void *addr;
 
         if (!test_bit(R5_Wantwrite, &sh->dev[i].flags))
             continue;
         addr = kmap_atomic(sh->dev[i].page);
         sh->dev[i].log_checksum = crc32c_le(log->uuid_checksum,
                             addr, PAGE_SIZE);
         kunmap_atomic(addr);
         pages++;
     }
     WARN_ON(pages == 0);
 
     /*
      * The stripe must enter state machine again to call endio, so
      * don't delay.
      */
     clear_bit(STRIPE_DELAYED, &sh->state);
     atomic_inc(&sh->count);
 
     mutex_lock(&log->io_mutex);
     /* meta + data */
     reserve = (1 + pages) << (PAGE_SHIFT - 9);
 
     if (test_bit(R5C_LOG_CRITICAL, &conf->cache_state) &&
         sh->log_start == MaxSector)
         r5l_add_no_space_stripe(log, sh);
     else if (!r5l_has_free_space(log, reserve)) {
         if (sh->log_start == log->last_checkpoint)
             BUG();
         else
             r5l_add_no_space_stripe(log, sh);
     } else {
         ret = r5l_log_stripe(log, sh, pages, 0);
         if (ret) {
             spin_lock_irq(&log->io_list_lock);
             list_add_tail(&sh->log_list, &log->no_mem_stripes);
             spin_unlock_irq(&log->io_list_lock);
         }
     }
 
     mutex_unlock(&log->io_mutex);
     return 0;
 }
 
 /* check whether this big stripe is in write back cache. */
 bool r5c_big_stripe_cached(struct r5conf *conf, sector_t sect)
 {
     struct r5l_log *log = conf->log;
     sector_t tree_index;
     void *slot;
 
     if (!log)
         return false;
 
     WARN_ON_ONCE(!rcu_read_lock_held());
     tree_index = r5c_tree_index(conf, sect);
     slot = radix_tree_lookup(&log->big_stripe_tree, tree_index);
     return slot != NULL;
 }
 
 static int r5l_load_log(struct r5l_log *log)
 {
     struct md_rdev *rdev = log->rdev;
     struct page *page;
     struct r5l_meta_block *mb;
     sector_t cp = log->rdev->journal_tail;
     u32 stored_crc, expected_crc;
     bool create_super = false;
     int ret = 0;
 
     /* Make sure it's valid */
     if (cp >= rdev->sectors || round_down(cp, BLOCK_SECTORS) != cp)
         cp = 0;
     page = alloc_page(GFP_KERNEL);
     if (!page)
         return -ENOMEM;
 
     if (!sync_page_io(rdev, cp, PAGE_SIZE, page, REQ_OP_READ, false)) {
         ret = -EIO;
         goto ioerr;
     }
     mb = page_address(page);
 
     if (le32_to_cpu(mb->magic) != R5LOG_MAGIC ||
         mb->version != R5LOG_VERSION) {
         create_super = true;
         goto create;
     }
     stored_crc = le32_to_cpu(mb->checksum);
     mb->checksum = 0;
     expected_crc = crc32c_le(log->uuid_checksum, mb, PAGE_SIZE);
     if (stored_crc != expected_crc) {
         create_super = true;
         goto create;
     }
     if (le64_to_cpu(mb->position) != cp) {
         create_super = true;
         goto create;
     }
 create:
     if (create_super) {
         log->last_cp_seq = prandom_u32();
         cp = 0;
         r5l_log_write_empty_meta_block(log, cp, log->last_cp_seq);
         /*
          * Make sure super points to correct address. Log might have
          * data very soon. If super hasn't correct log tail address,
          * recovery can't find the log
          */
         r5l_write_super(log, cp);
     } else
         log->last_cp_seq = le64_to_cpu(mb->seq);
 
     log->device_size = round_down(rdev->sectors, BLOCK_SECTORS);
     log->max_free_space = log->device_size >> RECLAIM_MAX_FREE_SPACE_SHIFT;
     if (log->max_free_space > RECLAIM_MAX_FREE_SPACE)
         log->max_free_space = RECLAIM_MAX_FREE_SPACE;
     log->last_checkpoint = cp;
 
     __free_page(page);
 
     if (create_super) {
         log->log_start = r5l_ring_add(log, cp, BLOCK_SECTORS);
         log->seq = log->last_cp_seq + 1;
         log->next_checkpoint = cp;
     } else
         ret = r5l_recovery_log(log);
 
     r5c_update_log_state(log);
     return ret;
 ioerr:
     __free_page(page);
     return ret;
 }
 
 int r5l_start(struct r5l_log *log)
 {
     int ret;
 
     if (!log)
         return 0;
 
     ret = r5l_load_log(log);
     if (ret) {
         struct mddev *mddev = log->rdev->mddev;
         struct r5conf *conf = mddev->private;
 
         r5l_exit_log(conf);
     }
     return ret;
 }
 
 void r5c_update_on_rdev_error(struct mddev *mddev, struct md_rdev *rdev)
 {
     struct r5conf *conf = mddev->private;
     struct r5l_log *log = conf->log;
 
     if (!log)
         return;
 
     if ((raid5_calc_degraded(conf) > 0 ||
          test_bit(Journal, &rdev->flags)) &&
         conf->log->r5c_journal_mode == R5C_JOURNAL_MODE_WRITE_BACK)
         schedule_work(&log->disable_writeback_work);
 }
 
 int r5l_init_log(struct r5conf *conf, struct md_rdev *rdev)
 {
     struct request_queue *q = bdev_get_queue(rdev->bdev);
     struct r5l_log *log;
     int ret;
 
     pr_debug("md/raid:%s: using device %pg as journal\n",
          mdname(conf->mddev), rdev->bdev);
 
     if (PAGE_SIZE != 4096)
         return -EINVAL;
 
     /*
      * The PAGE_SIZE must be big enough to hold 1 r5l_meta_block and
      * raid_disks r5l_payload_data_parity.
      *
      * Write journal and cache does not work for very big array
      * (raid_disks > 203)
      */
     if (sizeof(struct r5l_meta_block) +
         ((sizeof(struct r5l_payload_data_parity) + sizeof(__le32)) *
          conf->raid_disks) > PAGE_SIZE) {
         pr_err("md/raid:%s: write journal/cache doesn't work for array with %d disks\n",
                mdname(conf->mddev), conf->raid_disks);
         return -EINVAL;
     }
 
     log = kzalloc(sizeof(*log), GFP_KERNEL);
     if (!log)
         return -ENOMEM;
     log->rdev = rdev;
 
     log->need_cache_flush = test_bit(QUEUE_FLAG_WC, &q->queue_flags) != 0;
 
     log->uuid_checksum = crc32c_le(~0, rdev->mddev->uuid,
                        sizeof(rdev->mddev->uuid));
 
     mutex_init(&log->io_mutex);
 
     spin_lock_init(&log->io_list_lock);
     INIT_LIST_HEAD(&log->running_ios);
     INIT_LIST_HEAD(&log->io_end_ios);
     INIT_LIST_HEAD(&log->flushing_ios);
     INIT_LIST_HEAD(&log->finished_ios);
 
     log->io_kc = KMEM_CACHE(r5l_io_unit, 0);
     if (!log->io_kc)
         goto io_kc;
 
     ret = mempool_init_slab_pool(&log->io_pool, R5L_POOL_SIZE, log->io_kc);
     if (ret)
         goto io_pool;
 
     ret = bioset_init(&log->bs, R5L_POOL_SIZE, 0, BIOSET_NEED_BVECS);
     if (ret)
         goto io_bs;
 
     ret = mempool_init_page_pool(&log->meta_pool, R5L_POOL_SIZE, 0);
     if (ret)
         goto out_mempool;
 
     spin_lock_init(&log->tree_lock);
     INIT_RADIX_TREE(&log->big_stripe_tree, GFP_NOWAIT | __GFP_NOWARN);
 
     log->reclaim_thread = md_register_thread(r5l_reclaim_thread,
                          log->rdev->mddev, "reclaim");
     if (!log->reclaim_thread)
         goto reclaim_thread;
     log->reclaim_thread->timeout = R5C_RECLAIM_WAKEUP_INTERVAL;
 
     init_waitqueue_head(&log->iounit_wait);
 
     INIT_LIST_HEAD(&log->no_mem_stripes);
 
     INIT_LIST_HEAD(&log->no_space_stripes);
     spin_lock_init(&log->no_space_stripes_lock);
 
     INIT_WORK(&log->deferred_io_work, r5l_submit_io_async);
     INIT_WORK(&log->disable_writeback_work, r5c_disable_writeback_async);
 
     log->r5c_journal_mode = R5C_JOURNAL_MODE_WRITE_THROUGH;
     INIT_LIST_HEAD(&log->stripe_in_journal_list);
     spin_lock_init(&log->stripe_in_journal_lock);
     atomic_set(&log->stripe_in_journal_count, 0);
 
     conf->log = log;
 
     set_bit(MD_HAS_JOURNAL, &conf->mddev->flags);
     return 0;
 
 reclaim_thread:
     mempool_exit(&log->meta_pool);
 out_mempool:
     bioset_exit(&log->bs);
 io_bs:
     mempool_exit(&log->io_pool);
 io_pool:
     kmem_cache_destroy(log->io_kc);
 io_kc:
     kfree(log);
     return -EINVAL;
 }
 
 void r5l_exit_log(struct r5conf *conf)
 {
     struct r5l_log *log = conf->log;
 
     /* Ensure disable_writeback_work wakes up and exits */
     wake_up(&conf->mddev->sb_wait);
     flush_work(&log->disable_writeback_work);
     md_unregister_thread(&log->reclaim_thread);
 
     conf->log = NULL;
 
     mempool_exit(&log->meta_pool);
     bioset_exit(&log->bs);
     mempool_exit(&log->io_pool);
     kmem_cache_destroy(log->io_kc);
     kfree(log);
 }