Merge tag 'md-6.12-20240829' of https://git.kernel.org/pub/scm/linux/kernel/git/song/md into for-6.12/block

Pull MD updates from Song:

"Major changes in this set are:

 1. md-bitmap refactoring, by Yu Kuai;
 2. raid5 performance optimization, by Artur Paszkiewicz;
 3. Other small fixes, by Yu Kuai and Chen Ni."

* tag 'md-6.12-20240829' of https://git.kernel.org/pub/scm/linux/kernel/git/song/md: (49 commits)
  md/raid5: rename wait_for_overlap to wait_for_reshape
  md/raid5: only add to wq if reshape is in progress
  md/raid5: use wait_on_bit() for R5_Overlap
  md: Remove flush handling
  md/md-bitmap: make in memory structure internal
  md/md-bitmap: merge md_bitmap_enabled() into bitmap_operations
  md/md-bitmap: merge md_bitmap_wait_behind_writes() into bitmap_operations
  md/md-bitmap: merge md_bitmap_free() into bitmap_operations
  md/md-bitmap: merge md_bitmap_set_pages() into struct bitmap_operations
  md/md-bitmap: merge md_bitmap_copy_from_slot() into struct bitmap_operation.
  md/md-bitmap: merge get_bitmap_from_slot() into bitmap_operations
  md/md-bitmap: merge md_bitmap_resize() into bitmap_operations
  md/md-bitmap: pass in mddev directly for md_bitmap_resize()
  md/md-bitmap: merge md_bitmap_daemon_work() into bitmap_operations
  md/md-bitmap: merge bitmap_unplug() into bitmap_operations
  md/md-bitmap: merge md_bitmap_unplug_async() into md_bitmap_unplug()
  md/md-bitmap: merge md_bitmap_sync_with_cluster() into bitmap_operations
  md/md-bitmap: merge md_bitmap_cond_end_sync() into bitmap_operations
  md/md-bitmap: merge md_bitmap_close_sync() into bitmap_operations
  md/md-bitmap: merge md_bitmap_end_sync() into bitmap_operations
  ...

12 files changed, 832 insertions, 765 deletions

diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
index 0c3323e0adb2..63682d27fc8d 100644
--- a/drivers/md/dm-raid.c
+++ b/drivers/md/dm-raid.c
@@ -3949,7 +3949,9 @@ static int __load_dirty_region_bitmap(struct raid_set *rs)
 	/* Try loading the bitmap unless "raid0", which does not have one */
 	if (!rs_is_raid0(rs) &&
 	    !test_and_set_bit(RT_FLAG_RS_BITMAP_LOADED, &rs->runtime_flags)) {
-		r = md_bitmap_load(&rs->md);
+		struct mddev *mddev = &rs->md;
+
+		r = mddev->bitmap_ops->load(mddev);
 		if (r)
 			DMERR("Failed to load bitmap");
 	}
@@ -4066,7 +4068,8 @@ static int raid_preresume(struct dm_target *ti)
 	       mddev->bitmap_info.chunksize != to_bytes(rs->requested_bitmap_chunk_sectors)))) {
 		int chunksize = to_bytes(rs->requested_bitmap_chunk_sectors) ?: mddev->bitmap_info.chunksize;
 
-		r = md_bitmap_resize(mddev->bitmap, mddev->dev_sectors, chunksize, 0);
+		r = mddev->bitmap_ops->resize(mddev, mddev->dev_sectors,
+					      chunksize, false);
 		if (r)
 			DMERR("Failed to resize bitmap");
 	}
diff --git a/drivers/md/md-bitmap.c b/drivers/md/md-bitmap.c
index 08232d8dc815..864418c8c028 100644
--- a/drivers/md/md-bitmap.c
+++ b/drivers/md/md-bitmap.c
@@ -32,11 +32,210 @@
 #include "md.h"
 #include "md-bitmap.h"
 
+#define BITMAP_MAJOR_LO 3
+/* version 4 insists the bitmap is in little-endian order
+ * with version 3, it is host-endian which is non-portable
+ * Version 5 is currently set only for clustered devices
+ */
+#define BITMAP_MAJOR_HI 4
+#define BITMAP_MAJOR_CLUSTERED 5
+#define	BITMAP_MAJOR_HOSTENDIAN 3
+
+/*
+ * in-memory bitmap:
+ *
+ * Use 16 bit block counters to track pending writes to each "chunk".
+ * The 2 high order bits are special-purpose, the first is a flag indicating
+ * whether a resync is needed.  The second is a flag indicating whether a
+ * resync is active.
+ * This means that the counter is actually 14 bits:
+ *
+ * +--------+--------+------------------------------------------------+
+ * | resync | resync |               counter                          |
+ * | needed | active |                                                |
+ * |  (0-1) |  (0-1) |              (0-16383)                         |
+ * +--------+--------+------------------------------------------------+
+ *
+ * The "resync needed" bit is set when:
+ *    a '1' bit is read from storage at startup.
+ *    a write request fails on some drives
+ *    a resync is aborted on a chunk with 'resync active' set
+ * It is cleared (and resync-active set) when a resync starts across all drives
+ * of the chunk.
+ *
+ *
+ * The "resync active" bit is set when:
+ *    a resync is started on all drives, and resync_needed is set.
+ *       resync_needed will be cleared (as long as resync_active wasn't already set).
+ * It is cleared when a resync completes.
+ *
+ * The counter counts pending write requests, plus the on-disk bit.
+ * When the counter is '1' and the resync bits are clear, the on-disk
+ * bit can be cleared as well, thus setting the counter to 0.
+ * When we set a bit, or in the counter (to start a write), if the fields is
+ * 0, we first set the disk bit and set the counter to 1.
+ *
+ * If the counter is 0, the on-disk bit is clear and the stripe is clean
+ * Anything that dirties the stripe pushes the counter to 2 (at least)
+ * and sets the on-disk bit (lazily).
+ * If a periodic sweep find the counter at 2, it is decremented to 1.
+ * If the sweep find the counter at 1, the on-disk bit is cleared and the
+ * counter goes to zero.
+ *
+ * Also, we'll hijack the "map" pointer itself and use it as two 16 bit block
+ * counters as a fallback when "page" memory cannot be allocated:
+ *
+ * Normal case (page memory allocated):
+ *
+ *     page pointer (32-bit)
+ *
+ *     [ ] ------+
+ *               |
+ *               +-------> [   ][   ]..[   ] (4096 byte page == 2048 counters)
+ *                          c1   c2    c2048
+ *
+ * Hijacked case (page memory allocation failed):
+ *
+ *     hijacked page pointer (32-bit)
+ *
+ *     [		  ][		  ] (no page memory allocated)
+ *      counter #1 (16-bit) counter #2 (16-bit)
+ *
+ */
+
+#define PAGE_BITS (PAGE_SIZE << 3)
+#define PAGE_BIT_SHIFT (PAGE_SHIFT + 3)
+
+#define NEEDED(x) (((bitmap_counter_t) x) & NEEDED_MASK)
+#define RESYNC(x) (((bitmap_counter_t) x) & RESYNC_MASK)
+#define COUNTER(x) (((bitmap_counter_t) x) & COUNTER_MAX)
+
+/* how many counters per page? */
+#define PAGE_COUNTER_RATIO (PAGE_BITS / COUNTER_BITS)
+/* same, except a shift value for more efficient bitops */
+#define PAGE_COUNTER_SHIFT (PAGE_BIT_SHIFT - COUNTER_BIT_SHIFT)
+/* same, except a mask value for more efficient bitops */
+#define PAGE_COUNTER_MASK  (PAGE_COUNTER_RATIO - 1)
+
+#define BITMAP_BLOCK_SHIFT 9
+
+/*
+ * bitmap structures:
+ */
+
+/* the in-memory bitmap is represented by bitmap_pages */
+struct bitmap_page {
+	/*
+	 * map points to the actual memory page
+	 */
+	char *map;
+	/*
+	 * in emergencies (when map cannot be alloced), hijack the map
+	 * pointer and use it as two counters itself
+	 */
+	unsigned int hijacked:1;
+	/*
+	 * If any counter in this page is '1' or '2' - and so could be
+	 * cleared then that page is marked as 'pending'
+	 */
+	unsigned int pending:1;
+	/*
+	 * count of dirty bits on the page
+	 */
+	unsigned int  count:30;
+};
+
+/* the main bitmap structure - one per mddev */
+struct bitmap {
+
+	struct bitmap_counts {
+		spinlock_t lock;
+		struct bitmap_page *bp;
+		/* total number of pages in the bitmap */
+		unsigned long pages;
+		/* number of pages not yet allocated */
+		unsigned long missing_pages;
+		/* chunksize = 2^chunkshift (for bitops) */
+		unsigned long chunkshift;
+		/* total number of data chunks for the array */
+		unsigned long chunks;
+	} counts;
+
+	struct mddev *mddev; /* the md device that the bitmap is for */
+
+	__u64	events_cleared;
+	int need_sync;
+
+	struct bitmap_storage {
+		/* backing disk file */
+		struct file *file;
+		/* cached copy of the bitmap file superblock */
+		struct page *sb_page;
+		unsigned long sb_index;
+		/* list of cache pages for the file */
+		struct page **filemap;
+		/* attributes associated filemap pages */
+		unsigned long *filemap_attr;
+		/* number of pages in the file */
+		unsigned long file_pages;
+		/* total bytes in the bitmap */
+		unsigned long bytes;
+	} storage;
+
+	unsigned long flags;
+
+	int allclean;
+
+	atomic_t behind_writes;
+	/* highest actual value at runtime */
+	unsigned long behind_writes_used;
+
+	/*
+	 * the bitmap daemon - periodically wakes up and sweeps the bitmap
+	 * file, cleaning up bits and flushing out pages to disk as necessary
+	 */
+	unsigned long daemon_lastrun; /* jiffies of last run */
+	/*
+	 * when we lasted called end_sync to update bitmap with resync
+	 * progress.
+	 */
+	unsigned long last_end_sync;
+
+	/* pending writes to the bitmap file */
+	atomic_t pending_writes;
+	wait_queue_head_t write_wait;
+	wait_queue_head_t overflow_wait;
+	wait_queue_head_t behind_wait;
+
+	struct kernfs_node *sysfs_can_clear;
+	/* slot offset for clustered env */
+	int cluster_slot;
+};
+
+static int __bitmap_resize(struct bitmap *bitmap, sector_t blocks,
+			   int chunksize, bool init);
+
 static inline char *bmname(struct bitmap *bitmap)
 {
 	return bitmap->mddev ? mdname(bitmap->mddev) : "mdX";
 }
 
+static bool __bitmap_enabled(struct bitmap *bitmap)
+{
+	return bitmap->storage.filemap &&
+	       !test_bit(BITMAP_STALE, &bitmap->flags);
+}
+
+static bool bitmap_enabled(struct mddev *mddev)
+{
+	struct bitmap *bitmap = mddev->bitmap;
+
+	if (!bitmap)
+		return false;
+
+	return __bitmap_enabled(bitmap);
+}
+
 /*
  * check a page and, if necessary, allocate it (or hijack it if the alloc fails)
  *
@@ -472,9 +671,10 @@ static void md_bitmap_wait_writes(struct bitmap *bitmap)
 
 
 /* update the event counter and sync the superblock to disk */
-void md_bitmap_update_sb(struct bitmap *bitmap)
+static void bitmap_update_sb(void *data)
 {
 	bitmap_super_t *sb;
+	struct bitmap *bitmap = data;
 
 	if (!bitmap || !bitmap->mddev) /* no bitmap for this array */
 		return;
@@ -510,10 +710,8 @@ void md_bitmap_update_sb(struct bitmap *bitmap)
 		write_sb_page(bitmap, bitmap->storage.sb_index,
 			      bitmap->storage.sb_page, 1);
 }
-EXPORT_SYMBOL(md_bitmap_update_sb);
 
-/* print out the bitmap file superblock */
-void md_bitmap_print_sb(struct bitmap *bitmap)
+static void bitmap_print_sb(struct bitmap *bitmap)
 {
 	bitmap_super_t *sb;
 
@@ -760,7 +958,7 @@ out_no_sb:
 			bitmap->mddev->bitmap_info.space > sectors_reserved)
 			bitmap->mddev->bitmap_info.space = sectors_reserved;
 	} else {
-		md_bitmap_print_sb(bitmap);
+		bitmap_print_sb(bitmap);
 		if (bitmap->cluster_slot < 0)
 			md_cluster_stop(bitmap->mddev);
 	}
@@ -893,7 +1091,7 @@ static void md_bitmap_file_unmap(struct bitmap_storage *store)
 static void md_bitmap_file_kick(struct bitmap *bitmap)
 {
 	if (!test_and_set_bit(BITMAP_STALE, &bitmap->flags)) {
-		md_bitmap_update_sb(bitmap);
+		bitmap_update_sb(bitmap);
 
 		if (bitmap->storage.file) {
 			pr_warn("%s: kicking failed bitmap file %pD4 from array!\n",
@@ -1028,13 +1226,13 @@ static int md_bitmap_file_test_bit(struct bitmap *bitmap, sector_t block)
 /* this gets called when the md device is ready to unplug its underlying
  * (slave) device queues -- before we let any writes go down, we need to
  * sync the dirty pages of the bitmap file to disk */
-void md_bitmap_unplug(struct bitmap *bitmap)
+static void __bitmap_unplug(struct bitmap *bitmap)
 {
 	unsigned long i;
 	int dirty, need_write;
 	int writing = 0;
 
-	if (!md_bitmap_enabled(bitmap))
+	if (!__bitmap_enabled(bitmap))
 		return;
 
 	/* look at each page to see if there are any set bits that need to be
@@ -1060,7 +1258,6 @@ void md_bitmap_unplug(struct bitmap *bitmap)
 	if (test_bit(BITMAP_WRITE_ERROR, &bitmap->flags))
 		md_bitmap_file_kick(bitmap);
 }
-EXPORT_SYMBOL(md_bitmap_unplug);
 
 struct bitmap_unplug_work {
 	struct work_struct work;
@@ -1073,11 +1270,11 @@ static void md_bitmap_unplug_fn(struct work_struct *work)
 	struct bitmap_unplug_work *unplug_work =
 		container_of(work, struct bitmap_unplug_work, work);
 
-	md_bitmap_unplug(unplug_work->bitmap);
+	__bitmap_unplug(unplug_work->bitmap);
 	complete(unplug_work->done);
 }
 
-void md_bitmap_unplug_async(struct bitmap *bitmap)
+static void bitmap_unplug_async(struct bitmap *bitmap)
 {
 	DECLARE_COMPLETION_ONSTACK(done);
 	struct bitmap_unplug_work unplug_work;
@@ -1089,7 +1286,19 @@ void md_bitmap_unplug_async(struct bitmap *bitmap)
 	queue_work(md_bitmap_wq, &unplug_work.work);
 	wait_for_completion(&done);
 }
-EXPORT_SYMBOL(md_bitmap_unplug_async);
+
+static void bitmap_unplug(struct mddev *mddev, bool sync)
+{
+	struct bitmap *bitmap = mddev->bitmap;
+
+	if (!bitmap)
+		return;
+
+	if (sync)
+		__bitmap_unplug(bitmap);
+	else
+		bitmap_unplug_async(bitmap);
+}
 
 static void md_bitmap_set_memory_bits(struct bitmap *bitmap, sector_t offset, int needed);
 
@@ -1226,22 +1435,21 @@ static int md_bitmap_init_from_disk(struct bitmap *bitmap, sector_t start)
 	return ret;
 }
 
-void md_bitmap_write_all(struct bitmap *bitmap)
+/* just flag bitmap pages as needing to be written. */
+static void bitmap_write_all(struct mddev *mddev)
 {
-	/* We don't actually write all bitmap blocks here,
-	 * just flag them as needing to be written
-	 */
 	int i;
+	struct bitmap *bitmap = mddev->bitmap;
 
 	if (!bitmap || !bitmap->storage.filemap)
 		return;
+
+	/* Only one copy, so nothing needed */
 	if (bitmap->storage.file)
-		/* Only one copy, so nothing needed */
 		return;
 
 	for (i = 0; i < bitmap->storage.file_pages; i++)
-		set_page_attr(bitmap, i,
-			      BITMAP_PAGE_NEEDWRITE);
+		set_page_attr(bitmap, i, BITMAP_PAGE_NEEDWRITE);
 	bitmap->allclean = 0;
 }
 
@@ -1290,7 +1498,7 @@ out:
  * bitmap daemon -- periodically wakes up to clean bits and flush pages
  *			out to disk
  */
-void md_bitmap_daemon_work(struct mddev *mddev)
+static void bitmap_daemon_work(struct mddev *mddev)
 {
 	struct bitmap *bitmap;
 	unsigned long j;
@@ -1461,8 +1669,11 @@ __acquires(bitmap->lock)
 			&(bitmap->bp[page].map[pageoff]);
 }
 
-int md_bitmap_startwrite(struct bitmap *bitmap, sector_t offset, unsigned long sectors, int behind)
+static int bitmap_startwrite(struct mddev *mddev, sector_t offset,
+			     unsigned long sectors, bool behind)
 {
+	struct bitmap *bitmap = mddev->bitmap;
+
 	if (!bitmap)
 		return 0;
 
@@ -1523,13 +1734,15 @@ int md_bitmap_startwrite(struct bitmap *bitmap, sector_t offset, unsigned long s
 	}
 	return 0;
 }
-EXPORT_SYMBOL(md_bitmap_startwrite);
 
-void md_bitmap_endwrite(struct bitmap *bitmap, sector_t offset,
-			unsigned long sectors, int success, int behind)
+static void bitmap_endwrite(struct mddev *mddev, sector_t offset,
+			    unsigned long sectors, bool success, bool behind)
 {
+	struct bitmap *bitmap = mddev->bitmap;
+
 	if (!bitmap)
 		return;
+
 	if (behind) {
 		if (atomic_dec_and_test(&bitmap->behind_writes))
 			wake_up(&bitmap->behind_wait);
@@ -1576,26 +1789,27 @@ void md_bitmap_endwrite(struct bitmap *bitmap, sector_t offset,
 			sectors = 0;
 	}
 }
-EXPORT_SYMBOL(md_bitmap_endwrite);
 
-static int __bitmap_start_sync(struct bitmap *bitmap, sector_t offset, sector_t *blocks,
-			       int degraded)
+static bool __bitmap_start_sync(struct bitmap *bitmap, sector_t offset,
+				sector_t *blocks, bool degraded)
 {
 	bitmap_counter_t *bmc;
-	int rv;
+	bool rv;
+
 	if (bitmap == NULL) {/* FIXME or bitmap set as 'failed' */
 		*blocks = 1024;
-		return 1; /* always resync if no bitmap */
+		return true; /* always resync if no bitmap */
 	}
 	spin_lock_irq(&bitmap->counts.lock);
+
+	rv = false;
 	bmc = md_bitmap_get_counter(&bitmap->counts, offset, blocks, 0);
-	rv = 0;
 	if (bmc) {
 		/* locked */
-		if (RESYNC(*bmc))
-			rv = 1;
-		else if (NEEDED(*bmc)) {
-			rv = 1;
+		if (RESYNC(*bmc)) {
+			rv = true;
+		} else if (NEEDED(*bmc)) {
+			rv = true;
 			if (!degraded) { /* don't set/clear bits if degraded */
 				*bmc |= RESYNC_MASK;
 				*bmc &= ~NEEDED_MASK;
@@ -1603,11 +1817,12 @@ static int __bitmap_start_sync(struct bitmap *bitmap, sector_t offset, sector_t
 		}
 	}
 	spin_unlock_irq(&bitmap->counts.lock);
+
 	return rv;
 }
 
-int md_bitmap_start_sync(struct bitmap *bitmap, sector_t offset, sector_t *blocks,
-			 int degraded)
+static bool bitmap_start_sync(struct mddev *mddev, sector_t offset,
+			      sector_t *blocks, bool degraded)
 {
 	/* bitmap_start_sync must always report on multiples of whole
 	 * pages, otherwise resync (which is very PAGE_SIZE based) will
@@ -1616,21 +1831,22 @@ int md_bitmap_start_sync(struct bitmap *bitmap, sector_t offset, sector_t *block
 	 * At least PAGE_SIZE>>9 blocks are covered.
 	 * Return the 'or' of the result.
 	 */
-	int rv = 0;
+	bool rv = false;
 	sector_t blocks1;
 
 	*blocks = 0;
 	while (*blocks < (PAGE_SIZE>>9)) {
-		rv |= __bitmap_start_sync(bitmap, offset,
+		rv |= __bitmap_start_sync(mddev->bitmap, offset,
 					  &blocks1, degraded);
 		offset += blocks1;
 		*blocks += blocks1;
 	}
+
 	return rv;
 }
-EXPORT_SYMBOL(md_bitmap_start_sync);
 
-void md_bitmap_end_sync(struct bitmap *bitmap, sector_t offset, sector_t *blocks, int aborted)
+static void __bitmap_end_sync(struct bitmap *bitmap, sector_t offset,
+			      sector_t *blocks, bool aborted)
 {
 	bitmap_counter_t *bmc;
 	unsigned long flags;
@@ -1659,9 +1875,14 @@ void md_bitmap_end_sync(struct bitmap *bitmap, sector_t offset, sector_t *blocks
  unlock:
 	spin_unlock_irqrestore(&bitmap->counts.lock, flags);
 }
-EXPORT_SYMBOL(md_bitmap_end_sync);
 
-void md_bitmap_close_sync(struct bitmap *bitmap)
+static void bitmap_end_sync(struct mddev *mddev, sector_t offset,
+			    sector_t *blocks)
+{
+	__bitmap_end_sync(mddev->bitmap, offset, blocks, true);
+}
+
+static void bitmap_close_sync(struct mddev *mddev)
 {
 	/* Sync has finished, and any bitmap chunks that weren't synced
 	 * properly have been aborted.  It remains to us to clear the
@@ -1669,19 +1890,23 @@ void md_bitmap_close_sync(struct bitmap *bitmap)
 	 */
 	sector_t sector = 0;
 	sector_t blocks;
+	struct bitmap *bitmap = mddev->bitmap;
+
 	if (!bitmap)
 		return;
+
 	while (sector < bitmap->mddev->resync_max_sectors) {
-		md_bitmap_end_sync(bitmap, sector, &blocks, 0);
+		__bitmap_end_sync(bitmap, sector, &blocks, false);
 		sector += blocks;
 	}
 }
-EXPORT_SYMBOL(md_bitmap_close_sync);
 
-void md_bitmap_cond_end_sync(struct bitmap *bitmap, sector_t sector, bool force)
+static void bitmap_cond_end_sync(struct mddev *mddev, sector_t sector,
+				 bool force)
 {
 	sector_t s = 0;
 	sector_t blocks;
+	struct bitmap *bitmap = mddev->bitmap;
 
 	if (!bitmap)
 		return;
@@ -1700,34 +1925,32 @@ void md_bitmap_cond_end_sync(struct bitmap *bitmap, sector_t sector, bool force)
 	sector &= ~((1ULL << bitmap->counts.chunkshift) - 1);
 	s = 0;
 	while (s < sector && s < bitmap->mddev->resync_max_sectors) {
-		md_bitmap_end_sync(bitmap, s, &blocks, 0);
+		__bitmap_end_sync(bitmap, s, &blocks, false);
 		s += blocks;
 	}
 	bitmap->last_end_sync = jiffies;
 	sysfs_notify_dirent_safe(bitmap->mddev->sysfs_completed);
 }
-EXPORT_SYMBOL(md_bitmap_cond_end_sync);
 
-void md_bitmap_sync_with_cluster(struct mddev *mddev,
-			      sector_t old_lo, sector_t old_hi,
-			      sector_t new_lo, sector_t new_hi)
+static void bitmap_sync_with_cluster(struct mddev *mddev,
+				     sector_t old_lo, sector_t old_hi,
+				     sector_t new_lo, sector_t new_hi)
 {
 	struct bitmap *bitmap = mddev->bitmap;
 	sector_t sector, blocks = 0;
 
 	for (sector = old_lo; sector < new_lo; ) {
-		md_bitmap_end_sync(bitmap, sector, &blocks, 0);
+		__bitmap_end_sync(bitmap, sector, &blocks, false);
 		sector += blocks;
 	}
 	WARN((blocks > new_lo) && old_lo, "alignment is not correct for lo\n");
 
 	for (sector = old_hi; sector < new_hi; ) {
-		md_bitmap_start_sync(bitmap, sector, &blocks, 0);
+		bitmap_start_sync(mddev, sector, &blocks, false);
 		sector += blocks;
 	}
 	WARN((blocks > new_hi) && old_hi, "alignment is not correct for hi\n");
 }
-EXPORT_SYMBOL(md_bitmap_sync_with_cluster);
 
 static void md_bitmap_set_memory_bits(struct bitmap *bitmap, sector_t offset, int needed)
 {
@@ -1756,12 +1979,18 @@ static void md_bitmap_set_memory_bits(struct bitmap *bitmap, sector_t offset, in
 }
 
 /* dirty the memory and file bits for bitmap chunks "s" to "e" */
-void md_bitmap_dirty_bits(struct bitmap *bitmap, unsigned long s, unsigned long e)
+static void bitmap_dirty_bits(struct mddev *mddev, unsigned long s,
+			      unsigned long e)
 {
 	unsigned long chunk;
+	struct bitmap *bitmap = mddev->bitmap;
+
+	if (!bitmap)
+		return;
 
 	for (chunk = s; chunk <= e; chunk++) {
 		sector_t sec = (sector_t)chunk << bitmap->counts.chunkshift;
+
 		md_bitmap_set_memory_bits(bitmap, sec, 1);
 		md_bitmap_file_set_bit(bitmap, sec);
 		if (sec < bitmap->mddev->recovery_cp)
@@ -1773,10 +2002,7 @@ void md_bitmap_dirty_bits(struct bitmap *bitmap, unsigned long s, unsigned long
 	}
 }
 
-/*
- * flush out any pending updates
- */
-void md_bitmap_flush(struct mddev *mddev)
+static void bitmap_flush(struct mddev *mddev)
 {
 	struct bitmap *bitmap = mddev->bitmap;
 	long sleep;
@@ -1789,23 +2015,21 @@ void md_bitmap_flush(struct mddev *mddev)
 	 */
 	sleep = mddev->bitmap_info.daemon_sleep * 2;
 	bitmap->daemon_lastrun -= sleep;
-	md_bitmap_daemon_work(mddev);
+	bitmap_daemon_work(mddev);
 	bitmap->daemon_lastrun -= sleep;
-	md_bitmap_daemon_work(mddev);
+	bitmap_daemon_work(mddev);
 	bitmap->daemon_lastrun -= sleep;
-	md_bitmap_daemon_work(mddev);
+	bitmap_daemon_work(mddev);
 	if (mddev->bitmap_info.external)
 		md_super_wait(mddev);
-	md_bitmap_update_sb(bitmap);
+	bitmap_update_sb(bitmap);
 }
 
-/*
- * free memory that was allocated
- */
-void md_bitmap_free(struct bitmap *bitmap)
+static void md_bitmap_free(void *data)
 {
 	unsigned long k, pages;
 	struct bitmap_page *bp;
+	struct bitmap *bitmap = data;
 
 	if (!bitmap) /* there was no bitmap */
 		return;
@@ -1836,9 +2060,8 @@ void md_bitmap_free(struct bitmap *bitmap)
 	kfree(bp);
 	kfree(bitmap);
 }
-EXPORT_SYMBOL(md_bitmap_free);
 
-void md_bitmap_wait_behind_writes(struct mddev *mddev)
+static void bitmap_wait_behind_writes(struct mddev *mddev)
 {
 	struct bitmap *bitmap = mddev->bitmap;
 
@@ -1852,14 +2075,14 @@ void md_bitmap_wait_behind_writes(struct mddev *mddev)
 	}
 }
 
-void md_bitmap_destroy(struct mddev *mddev)
+static void bitmap_destroy(struct mddev *mddev)
 {
 	struct bitmap *bitmap = mddev->bitmap;
 
 	if (!bitmap) /* there was no bitmap */
 		return;
 
-	md_bitmap_wait_behind_writes(mddev);
+	bitmap_wait_behind_writes(mddev);
 	if (!mddev->serialize_policy)
 		mddev_destroy_serial_pool(mddev, NULL);
 
@@ -1878,7 +2101,7 @@ void md_bitmap_destroy(struct mddev *mddev)
  * if this returns an error, bitmap_destroy must be called to do clean up
  * once mddev->bitmap is set
  */
-struct bitmap *md_bitmap_create(struct mddev *mddev, int slot)
+static struct bitmap *__bitmap_create(struct mddev *mddev, int slot)
 {
 	struct bitmap *bitmap;
 	sector_t blocks = mddev->resync_max_sectors;
@@ -1948,7 +2171,8 @@ struct bitmap *md_bitmap_create(struct mddev *mddev, int slot)
 		goto error;
 
 	bitmap->daemon_lastrun = jiffies;
-	err = md_bitmap_resize(bitmap, blocks, mddev->bitmap_info.chunksize, 1);
+	err = __bitmap_resize(bitmap, blocks, mddev->bitmap_info.chunksize,
+			      true);
 	if (err)
 		goto error;
 
@@ -1965,7 +2189,18 @@ struct bitmap *md_bitmap_create(struct mddev *mddev, int slot)
 	return ERR_PTR(err);
 }
 
-int md_bitmap_load(struct mddev *mddev)
+static int bitmap_create(struct mddev *mddev, int slot)
+{
+	struct bitmap *bitmap = __bitmap_create(mddev, slot);
+
+	if (IS_ERR(bitmap))
+		return PTR_ERR(bitmap);
+
+	mddev->bitmap = bitmap;
+	return 0;
+}
+
+static int bitmap_load(struct mddev *mddev)
 {
 	int err = 0;
 	sector_t start = 0;
@@ -1989,10 +2224,10 @@ int md_bitmap_load(struct mddev *mddev)
 	 */
 	while (sector < mddev->resync_max_sectors) {
 		sector_t blocks;
-		md_bitmap_start_sync(bitmap, sector, &blocks, 0);
+		bitmap_start_sync(mddev, sector, &blocks, false);
 		sector += blocks;
 	}
-	md_bitmap_close_sync(bitmap);
+	bitmap_close_sync(mddev);
 
 	if (mddev->degraded == 0
 	    || bitmap->events_cleared == mddev->events)
@@ -2014,22 +2249,21 @@ int md_bitmap_load(struct mddev *mddev)
 	mddev_set_timeout(mddev, mddev->bitmap_info.daemon_sleep, true);
 	md_wakeup_thread(mddev->thread);
 
-	md_bitmap_update_sb(bitmap);
+	bitmap_update_sb(bitmap);
 
 	if (test_bit(BITMAP_WRITE_ERROR, &bitmap->flags))
 		err = -EIO;
 out:
 	return err;
 }
-EXPORT_SYMBOL_GPL(md_bitmap_load);
 
 /* caller need to free returned bitmap with md_bitmap_free() */
-struct bitmap *get_bitmap_from_slot(struct mddev *mddev, int slot)
+static void *bitmap_get_from_slot(struct mddev *mddev, int slot)
 {
 	int rv = 0;
 	struct bitmap *bitmap;
 
-	bitmap = md_bitmap_create(mddev, slot);
+	bitmap = __bitmap_create(mddev, slot);
 	if (IS_ERR(bitmap)) {
 		rv = PTR_ERR(bitmap);
 		return ERR_PTR(rv);
@@ -2043,20 +2277,19 @@ struct bitmap *get_bitmap_from_slot(struct mddev *mddev, int slot)
 
 	return bitmap;
 }
-EXPORT_SYMBOL(get_bitmap_from_slot);
 
 /* Loads the bitmap associated with slot and copies the resync information
  * to our bitmap
  */
-int md_bitmap_copy_from_slot(struct mddev *mddev, int slot,
-		sector_t *low, sector_t *high, bool clear_bits)
+static int bitmap_copy_from_slot(struct mddev *mddev, int slot, sector_t *low,
+				 sector_t *high, bool clear_bits)
 {
 	int rv = 0, i, j;
 	sector_t block, lo = 0, hi = 0;
 	struct bitmap_counts *counts;
 	struct bitmap *bitmap;
 
-	bitmap = get_bitmap_from_slot(mddev, slot);
+	bitmap = bitmap_get_from_slot(mddev, slot);
 	if (IS_ERR(bitmap)) {
 		pr_err("%s can't get bitmap from slot %d\n", __func__, slot);
 		return -1;
@@ -2076,53 +2309,59 @@ int md_bitmap_copy_from_slot(struct mddev *mddev, int slot,
 	}
 
 	if (clear_bits) {
-		md_bitmap_update_sb(bitmap);
+		bitmap_update_sb(bitmap);
 		/* BITMAP_PAGE_PENDING is set, but bitmap_unplug needs
 		 * BITMAP_PAGE_DIRTY or _NEEDWRITE to write ... */
 		for (i = 0; i < bitmap->storage.file_pages; i++)
 			if (test_page_attr(bitmap, i, BITMAP_PAGE_PENDING))
 				set_page_attr(bitmap, i, BITMAP_PAGE_NEEDWRITE);
-		md_bitmap_unplug(bitmap);
+		__bitmap_unplug(bitmap);
 	}
-	md_bitmap_unplug(mddev->bitmap);
+	__bitmap_unplug(mddev->bitmap);
 	*low = lo;
 	*high = hi;
 	md_bitmap_free(bitmap);
 
 	return rv;
 }
-EXPORT_SYMBOL_GPL(md_bitmap_copy_from_slot);
 
+static void bitmap_set_pages(void *data, unsigned long pages)
+{
+	struct bitmap *bitmap = data;
+
+	bitmap->counts.pages = pages;
+}
 
-void md_bitmap_status(struct seq_file *seq, struct bitmap *bitmap)
+static int bitmap_get_stats(void *data, struct md_bitmap_stats *stats)
 {
-	unsigned long chunk_kb;
+	struct bitmap_storage *storage;
 	struct bitmap_counts *counts;
+	struct bitmap *bitmap = data;
+	bitmap_super_t *sb;
 
 	if (!bitmap)
-		return;
+		return -ENOENT;
+
+	sb = kmap_local_page(bitmap->storage.sb_page);
+	stats->sync_size = le64_to_cpu(sb->sync_size);
+	kunmap_local(sb);
 
 	counts = &bitmap->counts;
+	stats->missing_pages = counts->missing_pages;
+	stats->pages = counts->pages;
 
-	chunk_kb = bitmap->mddev->bitmap_info.chunksize >> 10;
-	seq_printf(seq, "bitmap: %lu/%lu pages [%luKB], "
-		   "%lu%s chunk",
-		   counts->pages - counts->missing_pages,
-		   counts->pages,
-		   (counts->pages - counts->missing_pages)
-		   << (PAGE_SHIFT - 10),
-		   chunk_kb ? chunk_kb : bitmap->mddev->bitmap_info.chunksize,
-		   chunk_kb ? "KB" : "B");
-	if (bitmap->storage.file) {
-		seq_printf(seq, ", file: ");
-		seq_file_path(seq, bitmap->storage.file, " \t\n");
-	}
+	storage = &bitmap->storage;
+	stats->file_pages = storage->file_pages;
+	stats->file = storage->file;
 
-	seq_printf(seq, "\n");
+	stats->behind_writes = atomic_read(&bitmap->behind_writes);
+	stats->behind_wait = wq_has_sleeper(&bitmap->behind_wait);
+	stats->events_cleared = bitmap->events_cleared;
+	return 0;
 }
 
-int md_bitmap_resize(struct bitmap *bitmap, sector_t blocks,
-		  int chunksize, int init)
+static int __bitmap_resize(struct bitmap *bitmap, sector_t blocks,
+			   int chunksize, bool init)
 {
 	/* If chunk_size is 0, choose an appropriate chunk size.
 	 * Then possibly allocate new storage space.
@@ -2320,14 +2559,24 @@ int md_bitmap_resize(struct bitmap *bitmap, sector_t blocks,
 	spin_unlock_irq(&bitmap->counts.lock);
 
 	if (!init) {
-		md_bitmap_unplug(bitmap);
+		__bitmap_unplug(bitmap);
 		bitmap->mddev->pers->quiesce(bitmap->mddev, 0);
 	}
 	ret = 0;
 err:
 	return ret;
 }
-EXPORT_SYMBOL_GPL(md_bitmap_resize);
+
+static int bitmap_resize(struct mddev *mddev, sector_t blocks, int chunksize,
+			 bool init)
+{
+	struct bitmap *bitmap = mddev->bitmap;
+
+	if (!bitmap)
+		return 0;
+
+	return __bitmap_resize(bitmap, blocks, chunksize, init);
+}
 
 static ssize_t
 location_show(struct mddev *mddev, char *page)
@@ -2367,7 +2616,7 @@ location_store(struct mddev *mddev, const char *buf, size_t len)
 			goto out;
 		}
 
-		md_bitmap_destroy(mddev);
+		bitmap_destroy(mddev);
 		mddev->bitmap_info.offset = 0;
 		if (mddev->bitmap_info.file) {
 			struct file *f = mddev->bitmap_info.file;
@@ -2377,7 +2626,6 @@ location_store(struct mddev *mddev, const char *buf, size_t len)
 	} else {
 		/* No bitmap, OK to set a location */
 		long long offset;
-		struct bitmap *bitmap;
 
 		if (strncmp(buf, "none", 4) == 0)
 			/* nothing to be done */;
@@ -2404,17 +2652,14 @@ location_store(struct mddev *mddev, const char *buf, size_t len)
 			}
 
 			mddev->bitmap_info.offset = offset;
-			bitmap = md_bitmap_create(mddev, -1);
-			if (IS_ERR(bitmap)) {
-				rv = PTR_ERR(bitmap);
+			rv = bitmap_create(mddev, -1);
+			if (rv)
 				goto out;
-			}
 
-			mddev->bitmap = bitmap;
-			rv = md_bitmap_load(mddev);
+			rv = bitmap_load(mddev);
 			if (rv) {
 				mddev->bitmap_info.offset = 0;
-				md_bitmap_destroy(mddev);
+				bitmap_destroy(mddev);
 				goto out;
 			}
 		}
@@ -2450,6 +2695,7 @@ space_show(struct mddev *mddev, char *page)
 static ssize_t
 space_store(struct mddev *mddev, const char *buf, size_t len)
 {
+	struct bitmap *bitmap;
 	unsigned long sectors;
 	int rv;
 
@@ -2460,8 +2706,8 @@ space_store(struct mddev *mddev, const char *buf, size_t len)
 	if (sectors == 0)
 		return -EINVAL;
 
-	if (mddev->bitmap &&
-	    sectors < (mddev->bitmap->storage.bytes + 511) >> 9)
+	bitmap = mddev->bitmap;
+	if (bitmap && sectors < (bitmap->storage.bytes + 511) >> 9)
 		return -EFBIG; /* Bitmap is too big for this small space */
 
 	/* could make sure it isn't too big, but that isn't really
@@ -2569,7 +2815,7 @@ backlog_store(struct mddev *mddev, const char *buf, size_t len)
 			mddev_create_serial_pool(mddev, rdev);
 	}
 	if (old_mwb != backlog)
-		md_bitmap_update_sb(mddev->bitmap);
+		bitmap_update_sb(mddev->bitmap);
 
 	mddev_unlock_and_resume(mddev);
 	return len;
@@ -2638,10 +2884,13 @@ __ATTR(metadata, S_IRUGO|S_IWUSR, metadata_show, metadata_store);
 static ssize_t can_clear_show(struct mddev *mddev, char *page)
 {
 	int len;
+	struct bitmap *bitmap;
+
 	spin_lock(&mddev->lock);
-	if (mddev->bitmap)
-		len = sprintf(page, "%s\n", (mddev->bitmap->need_sync ?
-					     "false" : "true"));
+	bitmap = mddev->bitmap;
+	if (bitmap)
+		len = sprintf(page, "%s\n", (bitmap->need_sync ? "false" :
+								 "true"));
 	else
 		len = sprintf(page, "\n");
 	spin_unlock(&mddev->lock);
@@ -2650,17 +2899,24 @@ static ssize_t can_clear_show(struct mddev *mddev, char *page)
 
 static ssize_t can_clear_store(struct mddev *mddev, const char *buf, size_t len)
 {
-	if (mddev->bitmap == NULL)
+	struct bitmap *bitmap = mddev->bitmap;
+
+	if (!bitmap)
 		return -ENOENT;
-	if (strncmp(buf, "false", 5) == 0)
-		mddev->bitmap->need_sync = 1;
-	else if (strncmp(buf, "true", 4) == 0) {
+
+	if (strncmp(buf, "false", 5) == 0) {
+		bitmap->need_sync = 1;
+		return len;
+	}
+
+	if (strncmp(buf, "true", 4) == 0) {
 		if (mddev->degraded)
 			return -EBUSY;
-		mddev->bitmap->need_sync = 0;
-	} else
-		return -EINVAL;
-	return len;
+		bitmap->need_sync = 0;
+		return len;
+	}
+
+	return -EINVAL;
 }
 
 static struct md_sysfs_entry bitmap_can_clear =
@@ -2670,21 +2926,26 @@ static ssize_t
 behind_writes_used_show(struct mddev *mddev, char *page)
 {
 	ssize_t ret;
+	struct bitmap *bitmap;
+
 	spin_lock(&mddev->lock);
-	if (mddev->bitmap == NULL)
+	bitmap = mddev->bitmap;
+	if (!bitmap)
 		ret = sprintf(page, "0\n");
 	else
-		ret = sprintf(page, "%lu\n",
-			      mddev->bitmap->behind_writes_used);
+		ret = sprintf(page, "%lu\n", bitmap->behind_writes_used);
 	spin_unlock(&mddev->lock);
+
 	return ret;
 }
 
 static ssize_t
 behind_writes_used_reset(struct mddev *mddev, const char *buf, size_t len)
 {
-	if (mddev->bitmap)
-		mddev->bitmap->behind_writes_used = 0;
+	struct bitmap *bitmap = mddev->bitmap;
+
+	if (bitmap)
+		bitmap->behind_writes_used = 0;
 	return len;
 }
 
@@ -2707,3 +2968,38 @@ const struct attribute_group md_bitmap_group = {
 	.name = "bitmap",
 	.attrs = md_bitmap_attrs,
 };
+
+static struct bitmap_operations bitmap_ops = {
+	.enabled		= bitmap_enabled,
+	.create			= bitmap_create,
+	.resize			= bitmap_resize,
+	.load			= bitmap_load,
+	.destroy		= bitmap_destroy,
+	.flush			= bitmap_flush,
+	.write_all		= bitmap_write_all,
+	.dirty_bits		= bitmap_dirty_bits,
+	.unplug			= bitmap_unplug,
+	.daemon_work		= bitmap_daemon_work,
+	.wait_behind_writes	= bitmap_wait_behind_writes,
+
+	.startwrite		= bitmap_startwrite,
+	.endwrite		= bitmap_endwrite,
+	.start_sync		= bitmap_start_sync,
+	.end_sync		= bitmap_end_sync,
+	.cond_end_sync		= bitmap_cond_end_sync,
+	.close_sync		= bitmap_close_sync,
+
+	.update_sb		= bitmap_update_sb,
+	.get_stats		= bitmap_get_stats,
+
+	.sync_with_cluster	= bitmap_sync_with_cluster,
+	.get_from_slot		= bitmap_get_from_slot,
+	.copy_from_slot		= bitmap_copy_from_slot,
+	.set_pages		= bitmap_set_pages,
+	.free			= md_bitmap_free,
+};
+
+void mddev_set_bitmap_ops(struct mddev *mddev)
+{
+	mddev->bitmap_ops = &bitmap_ops;
+}
diff --git a/drivers/md/md-bitmap.h b/drivers/md/md-bitmap.h
index bb9eb418780a..662e6fc141a7 100644
--- a/drivers/md/md-bitmap.h
+++ b/drivers/md/md-bitmap.h
@@ -7,81 +7,7 @@
 #ifndef BITMAP_H
 #define BITMAP_H 1
 
-#define BITMAP_MAJOR_LO 3
-/* version 4 insists the bitmap is in little-endian order
- * with version 3, it is host-endian which is non-portable
- * Version 5 is currently set only for clustered devices
- */
-#define BITMAP_MAJOR_HI 4
-#define BITMAP_MAJOR_CLUSTERED 5
-#define	BITMAP_MAJOR_HOSTENDIAN 3
-
-/*
- * in-memory bitmap:
- *
- * Use 16 bit block counters to track pending writes to each "chunk".
- * The 2 high order bits are special-purpose, the first is a flag indicating
- * whether a resync is needed.  The second is a flag indicating whether a
- * resync is active.
- * This means that the counter is actually 14 bits:
- *
- * +--------+--------+------------------------------------------------+
- * | resync | resync |               counter                          |
- * | needed | active |                                                |
- * |  (0-1) |  (0-1) |              (0-16383)                         |
- * +--------+--------+------------------------------------------------+
- *
- * The "resync needed" bit is set when:
- *    a '1' bit is read from storage at startup.
- *    a write request fails on some drives
- *    a resync is aborted on a chunk with 'resync active' set
- * It is cleared (and resync-active set) when a resync starts across all drives
- * of the chunk.
- *
- *
- * The "resync active" bit is set when:
- *    a resync is started on all drives, and resync_needed is set.
- *       resync_needed will be cleared (as long as resync_active wasn't already set).
- * It is cleared when a resync completes.
- *
- * The counter counts pending write requests, plus the on-disk bit.
- * When the counter is '1' and the resync bits are clear, the on-disk
- * bit can be cleared as well, thus setting the counter to 0.
- * When we set a bit, or in the counter (to start a write), if the fields is
- * 0, we first set the disk bit and set the counter to 1.
- *
- * If the counter is 0, the on-disk bit is clear and the stripe is clean
- * Anything that dirties the stripe pushes the counter to 2 (at least)
- * and sets the on-disk bit (lazily).
- * If a periodic sweep find the counter at 2, it is decremented to 1.
- * If the sweep find the counter at 1, the on-disk bit is cleared and the
- * counter goes to zero.
- *
- * Also, we'll hijack the "map" pointer itself and use it as two 16 bit block
- * counters as a fallback when "page" memory cannot be allocated:
- *
- * Normal case (page memory allocated):
- *
- *     page pointer (32-bit)
- *
- *     [ ] ------+
- *               |
- *               +-------> [   ][   ]..[   ] (4096 byte page == 2048 counters)
- *                          c1   c2    c2048
- *
- * Hijacked case (page memory allocation failed):
- *
- *     hijacked page pointer (32-bit)
- *
- *     [		  ][		  ] (no page memory allocated)
- *      counter #1 (16-bit) counter #2 (16-bit)
- *
- */
-
-#ifdef __KERNEL__
-
-#define PAGE_BITS (PAGE_SIZE << 3)
-#define PAGE_BIT_SHIFT (PAGE_SHIFT + 3)
+#define BITMAP_MAGIC 0x6d746962
 
 typedef __u16 bitmap_counter_t;
 #define COUNTER_BITS 16
@@ -91,26 +17,6 @@ typedef __u16 bitmap_counter_t;
 #define NEEDED_MASK ((bitmap_counter_t) (1 << (COUNTER_BITS - 1)))
 #define RESYNC_MASK ((bitmap_counter_t) (1 << (COUNTER_BITS - 2)))
 #define COUNTER_MAX ((bitmap_counter_t) RESYNC_MASK - 1)
-#define NEEDED(x) (((bitmap_counter_t) x) & NEEDED_MASK)
-#define RESYNC(x) (((bitmap_counter_t) x) & RESYNC_MASK)
-#define COUNTER(x) (((bitmap_counter_t) x) & COUNTER_MAX)
-
-/* how many counters per page? */
-#define PAGE_COUNTER_RATIO (PAGE_BITS / COUNTER_BITS)
-/* same, except a shift value for more efficient bitops */
-#define PAGE_COUNTER_SHIFT (PAGE_BIT_SHIFT - COUNTER_BIT_SHIFT)
-/* same, except a mask value for more efficient bitops */
-#define PAGE_COUNTER_MASK  (PAGE_COUNTER_RATIO - 1)
-
-#define BITMAP_BLOCK_SHIFT 9
-
-#endif
-
-/*
- * bitmap structures:
- */
-
-#define BITMAP_MAGIC 0x6d746962
 
 /* use these for bitmap->flags and bitmap->sb->state bit-fields */
 enum bitmap_state {
@@ -152,136 +58,58 @@ typedef struct bitmap_super_s {
  *    devices.  For raid10 it is the size of the array.
  */
 
-#ifdef __KERNEL__
+struct md_bitmap_stats {
+	u64		events_cleared;
+	int		behind_writes;
+	bool		behind_wait;
 
-/* the in-memory bitmap is represented by bitmap_pages */
-struct bitmap_page {
-	/*
-	 * map points to the actual memory page
-	 */
-	char *map;
-	/*
-	 * in emergencies (when map cannot be alloced), hijack the map
-	 * pointer and use it as two counters itself
-	 */
-	unsigned int hijacked:1;
-	/*
-	 * If any counter in this page is '1' or '2' - and so could be
-	 * cleared then that page is marked as 'pending'
-	 */
-	unsigned int pending:1;
-	/*
-	 * count of dirty bits on the page
-	 */
-	unsigned int  count:30;
+	unsigned long	missing_pages;
+	unsigned long	file_pages;
+	unsigned long	sync_size;
+	unsigned long	pages;
+	struct file	*file;
 };
 
-/* the main bitmap structure - one per mddev */
-struct bitmap {
-
-	struct bitmap_counts {
-		spinlock_t lock;
-		struct bitmap_page *bp;
-		unsigned long pages;		/* total number of pages
-						 * in the bitmap */
-		unsigned long missing_pages;	/* number of pages
-						 * not yet allocated */
-		unsigned long chunkshift;	/* chunksize = 2^chunkshift
-						 * (for bitops) */
-		unsigned long chunks;		/* Total number of data
-						 * chunks for the array */
-	} counts;
-
-	struct mddev *mddev; /* the md device that the bitmap is for */
-
-	__u64	events_cleared;
-	int need_sync;
-
-	struct bitmap_storage {
-		struct file *file;		/* backing disk file */
-		struct page *sb_page;		/* cached copy of the bitmap
-						 * file superblock */
-		unsigned long sb_index;
-		struct page **filemap;		/* list of cache pages for
-						 * the file */
-		unsigned long *filemap_attr;	/* attributes associated
-						 * w/ filemap pages */
-		unsigned long file_pages;	/* number of pages in the file*/
-		unsigned long bytes;		/* total bytes in the bitmap */
-	} storage;
-
-	unsigned long flags;
-
-	int allclean;
-
-	atomic_t behind_writes;
-	unsigned long behind_writes_used; /* highest actual value at runtime */
-
-	/*
-	 * the bitmap daemon - periodically wakes up and sweeps the bitmap
-	 * file, cleaning up bits and flushing out pages to disk as necessary
-	 */
-	unsigned long daemon_lastrun; /* jiffies of last run */
-	unsigned long last_end_sync; /* when we lasted called end_sync to
-				      * update bitmap with resync progress */
-
-	atomic_t pending_writes; /* pending writes to the bitmap file */
-	wait_queue_head_t write_wait;
-	wait_queue_head_t overflow_wait;
-	wait_queue_head_t behind_wait;
-
-	struct kernfs_node *sysfs_can_clear;
-	int cluster_slot;		/* Slot offset for clustered env */
+struct bitmap_operations {
+	bool (*enabled)(struct mddev *mddev);
+	int (*create)(struct mddev *mddev, int slot);
+	int (*resize)(struct mddev *mddev, sector_t blocks, int chunksize,
+		      bool init);
+
+	int (*load)(struct mddev *mddev);
+	void (*destroy)(struct mddev *mddev);
+	void (*flush)(struct mddev *mddev);
+	void (*write_all)(struct mddev *mddev);
+	void (*dirty_bits)(struct mddev *mddev, unsigned long s,
+			   unsigned long e);
+	void (*unplug)(struct mddev *mddev, bool sync);
+	void (*daemon_work)(struct mddev *mddev);
+	void (*wait_behind_writes)(struct mddev *mddev);
+
+	int (*startwrite)(struct mddev *mddev, sector_t offset,
+			  unsigned long sectors, bool behind);
+	void (*endwrite)(struct mddev *mddev, sector_t offset,
+			 unsigned long sectors, bool success, bool behind);
+	bool (*start_sync)(struct mddev *mddev, sector_t offset,
+			   sector_t *blocks, bool degraded);
+	void (*end_sync)(struct mddev *mddev, sector_t offset, sector_t *blocks);
+	void (*cond_end_sync)(struct mddev *mddev, sector_t sector, bool force);
+	void (*close_sync)(struct mddev *mddev);
+
+	void (*update_sb)(void *data);
+	int (*get_stats)(void *data, struct md_bitmap_stats *stats);
+
+	void (*sync_with_cluster)(struct mddev *mddev,
+				  sector_t old_lo, sector_t old_hi,
+				  sector_t new_lo, sector_t new_hi);
+	void *(*get_from_slot)(struct mddev *mddev, int slot);
+	int (*copy_from_slot)(struct mddev *mddev, int slot, sector_t *lo,
+			      sector_t *hi, bool clear_bits);
+	void (*set_pages)(void *data, unsigned long pages);
+	void (*free)(void *data);
 };
 
 /* the bitmap API */
-
-/* these are used only by md/bitmap */
-struct bitmap *md_bitmap_create(struct mddev *mddev, int slot);
-int md_bitmap_load(struct mddev *mddev);
-void md_bitmap_flush(struct mddev *mddev);
-void md_bitmap_destroy(struct mddev *mddev);
-
-void md_bitmap_print_sb(struct bitmap *bitmap);
-void md_bitmap_update_sb(struct bitmap *bitmap);
-void md_bitmap_status(struct seq_file *seq, struct bitmap *bitmap);
-
-int  md_bitmap_setallbits(struct bitmap *bitmap);
-void md_bitmap_write_all(struct bitmap *bitmap);
-
-void md_bitmap_dirty_bits(struct bitmap *bitmap, unsigned long s, unsigned long e);
-
-/* these are exported */
-int md_bitmap_startwrite(struct bitmap *bitmap, sector_t offset,
-			 unsigned long sectors, int behind);
-void md_bitmap_endwrite(struct bitmap *bitmap, sector_t offset,
-			unsigned long sectors, int success, int behind);
-int md_bitmap_start_sync(struct bitmap *bitmap, sector_t offset, sector_t *blocks, int degraded);
-void md_bitmap_end_sync(struct bitmap *bitmap, sector_t offset, sector_t *blocks, int aborted);
-void md_bitmap_close_sync(struct bitmap *bitmap);
-void md_bitmap_cond_end_sync(struct bitmap *bitmap, sector_t sector, bool force);
-void md_bitmap_sync_with_cluster(struct mddev *mddev,
-				 sector_t old_lo, sector_t old_hi,
-				 sector_t new_lo, sector_t new_hi);
-
-void md_bitmap_unplug(struct bitmap *bitmap);
-void md_bitmap_unplug_async(struct bitmap *bitmap);
-void md_bitmap_daemon_work(struct mddev *mddev);
-
-int md_bitmap_resize(struct bitmap *bitmap, sector_t blocks,
-		     int chunksize, int init);
-struct bitmap *get_bitmap_from_slot(struct mddev *mddev, int slot);
-int md_bitmap_copy_from_slot(struct mddev *mddev, int slot,
-			     sector_t *lo, sector_t *hi, bool clear_bits);
-void md_bitmap_free(struct bitmap *bitmap);
-void md_bitmap_wait_behind_writes(struct mddev *mddev);
-
-static inline bool md_bitmap_enabled(struct bitmap *bitmap)
-{
-	return bitmap && bitmap->storage.filemap &&
-	       !test_bit(BITMAP_STALE, &bitmap->flags);
-}
-
-#endif
+void mddev_set_bitmap_ops(struct mddev *mddev);
 
 #endif
diff --git a/drivers/md/md-cluster.c b/drivers/md/md-cluster.c
index 1d0db62f0351..6595f89becdb 100644
--- a/drivers/md/md-cluster.c
+++ b/drivers/md/md-cluster.c
@@ -317,7 +317,7 @@ static void recover_bitmaps(struct md_thread *thread)
 					str, ret);
 			goto clear_bit;
 		}
-		ret = md_bitmap_copy_from_slot(mddev, slot, &lo, &hi, true);
+		ret = mddev->bitmap_ops->copy_from_slot(mddev, slot, &lo, &hi, true);
 		if (ret) {
 			pr_err("md-cluster: Could not copy data from bitmap %d\n", slot);
 			goto clear_bit;
@@ -497,8 +497,8 @@ static void process_suspend_info(struct mddev *mddev,
 	 * we don't want to trigger lots of WARN.
 	 */
 	if (sb && !(le32_to_cpu(sb->feature_map) & MD_FEATURE_RESHAPE_ACTIVE))
-		md_bitmap_sync_with_cluster(mddev, cinfo->sync_low,
-					    cinfo->sync_hi, lo, hi);
+		mddev->bitmap_ops->sync_with_cluster(mddev, cinfo->sync_low,
+						     cinfo->sync_hi, lo, hi);
 	cinfo->sync_low = lo;
 	cinfo->sync_hi = hi;
 
@@ -628,8 +628,9 @@ static int process_recvd_msg(struct mddev *mddev, struct cluster_msg *msg)
 		break;
 	case BITMAP_RESIZE:
 		if (le64_to_cpu(msg->high) != mddev->pers->size(mddev, 0, 0))
-			ret = md_bitmap_resize(mddev->bitmap,
-					    le64_to_cpu(msg->high), 0, 0);
+			ret = mddev->bitmap_ops->resize(mddev,
+							le64_to_cpu(msg->high),
+							0, false);
 		break;
 	default:
 		ret = -1;
@@ -856,7 +857,7 @@ static int gather_all_resync_info(struct mddev *mddev, int total_slots)
 		}
 
 		/* Read the disk bitmap sb and check if it needs recovery */
-		ret = md_bitmap_copy_from_slot(mddev, i, &lo, &hi, false);
+		ret = mddev->bitmap_ops->copy_from_slot(mddev, i, &lo, &hi, false);
 		if (ret) {
 			pr_warn("md-cluster: Could not gather bitmaps from slot %d", i);
 			lockres_free(bm_lockres);
@@ -1143,13 +1144,16 @@ static int update_bitmap_size(struct mddev *mddev, sector_t size)
 
 static int resize_bitmaps(struct mddev *mddev, sector_t newsize, sector_t oldsize)
 {
-	struct bitmap_counts *counts;
-	char str[64];
-	struct dlm_lock_resource *bm_lockres;
-	struct bitmap *bitmap = mddev->bitmap;
-	unsigned long my_pages = bitmap->counts.pages;
+	void *bitmap = mddev->bitmap;
+	struct md_bitmap_stats stats;
+	unsigned long my_pages;
 	int i, rv;
 
+	rv = mddev->bitmap_ops->get_stats(bitmap, &stats);
+	if (rv)
+		return rv;
+
+	my_pages = stats.pages;
 	/*
 	 * We need to ensure all the nodes can grow to a larger
 	 * bitmap size before make the reshaping.
@@ -1159,17 +1163,22 @@ static int resize_bitmaps(struct mddev *mddev, sector_t newsize, sector_t oldsiz
 		return rv;
 
 	for (i = 0; i < mddev->bitmap_info.nodes; i++) {
+		struct dlm_lock_resource *bm_lockres;
+		char str[64];
+
 		if (i == md_cluster_ops->slot_number(mddev))
 			continue;
 
-		bitmap = get_bitmap_from_slot(mddev, i);
+		bitmap = mddev->bitmap_ops->get_from_slot(mddev, i);
 		if (IS_ERR(bitmap)) {
 			pr_err("can't get bitmap from slot %d\n", i);
 			bitmap = NULL;
 			goto out;
 		}
-		counts = &bitmap->counts;
 
+		rv = mddev->bitmap_ops->get_stats(bitmap, &stats);
+		if (rv)
+			goto out;
 		/*
 		 * If we can hold the bitmap lock of one node then
 		 * the slot is not occupied, update the pages.
@@ -1183,21 +1192,21 @@ static int resize_bitmaps(struct mddev *mddev, sector_t newsize, sector_t oldsiz
 		bm_lockres->flags |= DLM_LKF_NOQUEUE;
 		rv = dlm_lock_sync(bm_lockres, DLM_LOCK_PW);
 		if (!rv)
-			counts->pages = my_pages;
+			mddev->bitmap_ops->set_pages(bitmap, my_pages);
 		lockres_free(bm_lockres);
 
-		if (my_pages != counts->pages)
+		if (my_pages != stats.pages)
 			/*
 			 * Let's revert the bitmap size if one node
 			 * can't resize bitmap
 			 */
 			goto out;
-		md_bitmap_free(bitmap);
+		mddev->bitmap_ops->free(bitmap);
 	}
 
 	return 0;
 out:
-	md_bitmap_free(bitmap);
+	mddev->bitmap_ops->free(bitmap);
 	update_bitmap_size(mddev, oldsize);
 	return -1;
 }
@@ -1207,24 +1216,27 @@ out:
  */
 static int cluster_check_sync_size(struct mddev *mddev)
 {
-	int i, rv;
-	bitmap_super_t *sb;
-	unsigned long my_sync_size, sync_size = 0;
-	int node_num = mddev->bitmap_info.nodes;
 	int current_slot = md_cluster_ops->slot_number(mddev);
-	struct bitmap *bitmap = mddev->bitmap;
-	char str[64];
+	int node_num = mddev->bitmap_info.nodes;
 	struct dlm_lock_resource *bm_lockres;
+	struct md_bitmap_stats stats;
+	void *bitmap = mddev->bitmap;
+	unsigned long sync_size = 0;
+	unsigned long my_sync_size;
+	char str[64];
+	int i, rv;
 
-	sb = kmap_atomic(bitmap->storage.sb_page);
-	my_sync_size = sb->sync_size;
-	kunmap_atomic(sb);
+	rv = mddev->bitmap_ops->get_stats(bitmap, &stats);
+	if (rv)
+		return rv;
+
+	my_sync_size = stats.sync_size;
 
 	for (i = 0; i < node_num; i++) {
 		if (i == current_slot)
 			continue;
 
-		bitmap = get_bitmap_from_slot(mddev, i);
+		bitmap = mddev->bitmap_ops->get_from_slot(mddev, i);
 		if (IS_ERR(bitmap)) {
 			pr_err("can't get bitmap from slot %d\n", i);
 			return -1;
@@ -1238,25 +1250,28 @@ static int cluster_check_sync_size(struct mddev *mddev)
 		bm_lockres = lockres_init(mddev, str, NULL, 1);
 		if (!bm_lockres) {
 			pr_err("md-cluster: Cannot initialize %s\n", str);
-			md_bitmap_free(bitmap);
+			mddev->bitmap_ops->free(bitmap);
 			return -1;
 		}
 		bm_lockres->flags |= DLM_LKF_NOQUEUE;
 		rv = dlm_lock_sync(bm_lockres, DLM_LOCK_PW);
 		if (!rv)
-			md_bitmap_update_sb(bitmap);
+			mddev->bitmap_ops->update_sb(bitmap);
 		lockres_free(bm_lockres);
 
-		sb = kmap_atomic(bitmap->storage.sb_page);
-		if (sync_size == 0)
-			sync_size = sb->sync_size;
-		else if (sync_size != sb->sync_size) {
-			kunmap_atomic(sb);
-			md_bitmap_free(bitmap);
+		rv = mddev->bitmap_ops->get_stats(bitmap, &stats);
+		if (rv) {
+			mddev->bitmap_ops->free(bitmap);
+			return rv;
+		}
+
+		if (sync_size == 0) {
+			sync_size = stats.sync_size;
+		} else if (sync_size != stats.sync_size) {
+			mddev->bitmap_ops->free(bitmap);
 			return -1;
 		}
-		kunmap_atomic(sb);
-		md_bitmap_free(bitmap);
+		mddev->bitmap_ops->free(bitmap);
 	}
 
 	return (my_sync_size == sync_size) ? 0 : -1;
@@ -1585,7 +1600,7 @@ static int gather_bitmaps(struct md_rdev *rdev)
 	for (sn = 0; sn < mddev->bitmap_info.nodes; sn++) {
 		if (sn == (cinfo->slot_number - 1))
 			continue;
-		err = md_bitmap_copy_from_slot(mddev, sn, &lo, &hi, false);
+		err = mddev->bitmap_ops->copy_from_slot(mddev, sn, &lo, &hi, false);
 		if (err) {
 			pr_warn("md-cluster: Could not gather bitmaps from slot %d", sn);
 			goto out;
diff --git a/drivers/md/md.c b/drivers/md/md.c
index d3a837506a36..414146111425 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -546,137 +546,30 @@ static int mddev_set_closing_and_sync_blockdev(struct mddev *mddev, int opener_n
 	return 0;
 }
 
-/*
- * Generic flush handling for md
- */
-
-static void md_end_flush(struct bio *bio)
-{
-	struct md_rdev *rdev = bio->bi_private;
-	struct mddev *mddev = rdev->mddev;
-
-	bio_put(bio);
-
-	rdev_dec_pending(rdev, mddev);
-
-	if (atomic_dec_and_test(&mddev->flush_pending))
-		/* The pre-request flush has finished */
-		queue_work(md_wq, &mddev->flush_work);
-}
-
-static void md_submit_flush_data(struct work_struct *ws);
-
-static void submit_flushes(struct work_struct *ws)
+bool md_flush_request(struct mddev *mddev, struct bio *bio)
 {
-	struct mddev *mddev = container_of(ws, struct mddev, flush_work);
 	struct md_rdev *rdev;
-
-	mddev->start_flush = ktime_get_boottime();
-	INIT_WORK(&mddev->flush_work, md_submit_flush_data);
-	atomic_set(&mddev->flush_pending, 1);
-	rcu_read_lock();
-	rdev_for_each_rcu(rdev, mddev)
-		if (rdev->raid_disk >= 0 &&
-		    !test_bit(Faulty, &rdev->flags)) {
-			struct bio *bi;
-
-			atomic_inc(&rdev->nr_pending);
-			rcu_read_unlock();
-			bi = bio_alloc_bioset(rdev->bdev, 0,
-					      REQ_OP_WRITE | REQ_PREFLUSH,
-					      GFP_NOIO, &mddev->bio_set);
-			bi->bi_end_io = md_end_flush;
-			bi->bi_private = rdev;
-			atomic_inc(&mddev->flush_pending);
-			submit_bio(bi);
-			rcu_read_lock();
-		}
-	rcu_read_unlock();
-	if (atomic_dec_and_test(&mddev->flush_pending))
-		queue_work(md_wq, &mddev->flush_work);
-}
-
-static void md_submit_flush_data(struct work_struct *ws)
-{
-	struct mddev *mddev = container_of(ws, struct mddev, flush_work);
-	struct bio *bio = mddev->flush_bio;
+	struct bio *new;
 
 	/*
-	 * must reset flush_bio before calling into md_handle_request to avoid a
-	 * deadlock, because other bios passed md_handle_request suspend check
-	 * could wait for this and below md_handle_request could wait for those
-	 * bios because of suspend check
+	 * md_flush_reqeust() should be called under md_handle_request() and
+	 * 'active_io' is already grabbed. Hence it's safe to get rdev directly
+	 * without rcu protection.
 	 */
-	spin_lock_irq(&mddev->lock);
-	mddev->prev_flush_start = mddev->start_flush;
-	mddev->flush_bio = NULL;
-	spin_unlock_irq(&mddev->lock);
-	wake_up(&mddev->sb_wait);
-
-	if (bio->bi_iter.bi_size == 0) {
-		/* an empty barrier - all done */
-		bio_endio(bio);
-	} else {
-		bio->bi_opf &= ~REQ_PREFLUSH;
-
-		/*
-		 * make_requst() will never return error here, it only
-		 * returns error in raid5_make_request() by dm-raid.
-		 * Since dm always splits data and flush operation into
-		 * two separate io, io size of flush submitted by dm
-		 * always is 0, make_request() will not be called here.
-		 */
-		if (WARN_ON_ONCE(!mddev->pers->make_request(mddev, bio)))
-			bio_io_error(bio);
-	}
+	WARN_ON(percpu_ref_is_zero(&mddev->active_io));
 
-	/* The pair is percpu_ref_get() from md_flush_request() */
-	percpu_ref_put(&mddev->active_io);
-}
+	rdev_for_each(rdev, mddev) {
+		if (rdev->raid_disk < 0 || test_bit(Faulty, &rdev->flags))
+			continue;
 
-/*
- * Manages consolidation of flushes and submitting any flushes needed for
- * a bio with REQ_PREFLUSH.  Returns true if the bio is finished or is
- * being finished in another context.  Returns false if the flushing is
- * complete but still needs the I/O portion of the bio to be processed.
- */
-bool md_flush_request(struct mddev *mddev, struct bio *bio)
-{
-	ktime_t req_start = ktime_get_boottime();
-	spin_lock_irq(&mddev->lock);
-	/* flush requests wait until ongoing flush completes,
-	 * hence coalescing all the pending requests.
-	 */
-	wait_event_lock_irq(mddev->sb_wait,
-			    !mddev->flush_bio ||
-			    ktime_before(req_start, mddev->prev_flush_start),
-			    mddev->lock);
-	/* new request after previous flush is completed */
-	if (ktime_after(req_start, mddev->prev_flush_start)) {
-		WARN_ON(mddev->flush_bio);
-		/*
-		 * Grab a reference to make sure mddev_suspend() will wait for
-		 * this flush to be done.
-		 *
-		 * md_flush_reqeust() is called under md_handle_request() and
-		 * 'active_io' is already grabbed, hence percpu_ref_is_zero()
-		 * won't pass, percpu_ref_tryget_live() can't be used because
-		 * percpu_ref_kill() can be called by mddev_suspend()
-		 * concurrently.
-		 */
-		WARN_ON(percpu_ref_is_zero(&mddev->active_io));
-		percpu_ref_get(&mddev->active_io);
-		mddev->flush_bio = bio;
-		spin_unlock_irq(&mddev->lock);
-		INIT_WORK(&mddev->flush_work, submit_flushes);
-		queue_work(md_wq, &mddev->flush_work);
-		return true;
+		new = bio_alloc_bioset(rdev->bdev, 0,
+				       REQ_OP_WRITE | REQ_PREFLUSH, GFP_NOIO,
+				       &mddev->bio_set);
+		bio_chain(new, bio);
+		submit_bio(new);
 	}
 
-	/* flush was performed for some other bio while we waited. */
-	spin_unlock_irq(&mddev->lock);
-	if (bio->bi_iter.bi_size == 0) {
-		/* pure flush without data - all done */
+	if (bio_sectors(bio) == 0) {
 		bio_endio(bio);
 		return true;
 	}
@@ -763,7 +656,6 @@ int mddev_init(struct mddev *mddev)
 	atomic_set(&mddev->openers, 0);
 	atomic_set(&mddev->sync_seq, 0);
 	spin_lock_init(&mddev->lock);
-	atomic_set(&mddev->flush_pending, 0);
 	init_waitqueue_head(&mddev->sb_wait);
 	init_waitqueue_head(&mddev->recovery_wait);
 	mddev->reshape_position = MaxSector;
@@ -772,6 +664,7 @@ int mddev_init(struct mddev *mddev)
 	mddev->resync_min = 0;
 	mddev->resync_max = MaxSector;
 	mddev->level = LEVEL_NONE;
+	mddev_set_bitmap_ops(mddev);
 
 	INIT_WORK(&mddev->sync_work, md_start_sync);
 	INIT_WORK(&mddev->del_work, mddev_delayed_delete);
@@ -1372,6 +1265,18 @@ static int super_90_load(struct md_rdev *rdev, struct md_rdev *refdev, int minor
 	return ret;
 }
 
+static u64 md_bitmap_events_cleared(struct mddev *mddev)
+{
+	struct md_bitmap_stats stats;
+	int err;
+
+	err = mddev->bitmap_ops->get_stats(mddev->bitmap, &stats);
+	if (err)
+		return 0;
+
+	return stats.events_cleared;
+}
+
 /*
  * validate_super for 0.90.0
  * note: we are not using "freshest" for 0.9 superblock
@@ -1464,7 +1369,7 @@ static int super_90_validate(struct mddev *mddev, struct md_rdev *freshest, stru
 		/* if adding to array with a bitmap, then we can accept an
 		 * older device ... but not too old.
 		 */
-		if (ev1 < mddev->bitmap->events_cleared)
+		if (ev1 < md_bitmap_events_cleared(mddev))
 			return 0;
 		if (ev1 < mddev->events)
 			set_bit(Bitmap_sync, &rdev->flags);
@@ -1991,7 +1896,7 @@ static int super_1_validate(struct mddev *mddev, struct md_rdev *freshest, struc
 		/* If adding to array with a bitmap, then we can accept an
 		 * older device, but not too old.
 		 */
-		if (ev1 < mddev->bitmap->events_cleared)
+		if (ev1 < md_bitmap_events_cleared(mddev))
 			return 0;
 		if (ev1 < mddev->events)
 			set_bit(Bitmap_sync, &rdev->flags);
@@ -2323,7 +2228,6 @@ super_1_allow_new_offset(struct md_rdev *rdev,
 			 unsigned long long new_offset)
 {
 	/* All necessary checks on new >= old have been done */
-	struct bitmap *bitmap;
 	if (new_offset >= rdev->data_offset)
 		return 1;
 
@@ -2340,11 +2244,18 @@ super_1_allow_new_offset(struct md_rdev *rdev,
 	 */
 	if (rdev->sb_start + (32+4)*2 > new_offset)
 		return 0;
-	bitmap = rdev->mddev->bitmap;
-	if (bitmap && !rdev->mddev->bitmap_info.file &&
-	    rdev->sb_start + rdev->mddev->bitmap_info.offset +
-	    bitmap->storage.file_pages * (PAGE_SIZE>>9) > new_offset)
-		return 0;
+
+	if (!rdev->mddev->bitmap_info.file) {
+		struct mddev *mddev = rdev->mddev;
+		struct md_bitmap_stats stats;
+		int err;
+
+		err = mddev->bitmap_ops->get_stats(mddev->bitmap, &stats);
+		if (!err && rdev->sb_start + mddev->bitmap_info.offset +
+		    stats.file_pages * (PAGE_SIZE >> 9) > new_offset)
+			return 0;
+	}
+
 	if (rdev->badblocks.sector + rdev->badblocks.size > new_offset)
 		return 0;
 
@@ -2820,7 +2731,7 @@ repeat:
 
 	mddev_add_trace_msg(mddev, "md md_update_sb");
 rewrite:
-	md_bitmap_update_sb(mddev->bitmap);
+	mddev->bitmap_ops->update_sb(mddev->bitmap);
 	rdev_for_each(rdev, mddev) {
 		if (rdev->sb_loaded != 1)
 			continue; /* no noise on spare devices */
@@ -4680,17 +4591,23 @@ bitmap_store(struct mddev *mddev, const char *buf, size_t len)
 	/* buf should be <chunk> <chunk> ... or <chunk>-<chunk> ... (range) */
 	while (*buf) {
 		chunk = end_chunk = simple_strtoul(buf, &end, 0);
-		if (buf == end) break;
+		if (buf == end)
+			break;
+
 		if (*end == '-') { /* range */
 			buf = end + 1;
 			end_chunk = simple_strtoul(buf, &end, 0);
-			if (buf == end) break;
+			if (buf == end)
+				break;
 		}
-		if (*end && !isspace(*end)) break;
-		md_bitmap_dirty_bits(mddev->bitmap, chunk, end_chunk);
+
+		if (*end && !isspace(*end))
+			break;
+
+		mddev->bitmap_ops->dirty_bits(mddev, chunk, end_chunk);
 		buf = skip_spaces(end);
 	}
-	md_bitmap_unplug(mddev->bitmap); /* flush the bits to disk */
+	mddev->bitmap_ops->unplug(mddev, true); /* flush the bits to disk */
 out:
 	mddev_unlock(mddev);
 	return len;
@@ -6206,16 +6123,10 @@ int md_run(struct mddev *mddev)
 	}
 	if (err == 0 && pers->sync_request &&
 	    (mddev->bitmap_info.file || mddev->bitmap_info.offset)) {
-		struct bitmap *bitmap;
-
-		bitmap = md_bitmap_create(mddev, -1);
-		if (IS_ERR(bitmap)) {
-			err = PTR_ERR(bitmap);
+		err = mddev->bitmap_ops->create(mddev, -1);
+		if (err)
 			pr_warn("%s: failed to create bitmap (%d)\n",
 				mdname(mddev), err);
-		} else
-			mddev->bitmap = bitmap;
-
 	}
 	if (err)
 		goto bitmap_abort;
@@ -6285,7 +6196,7 @@ bitmap_abort:
 		pers->free(mddev, mddev->private);
 	mddev->private = NULL;
 	module_put(pers->owner);
-	md_bitmap_destroy(mddev);
+	mddev->bitmap_ops->destroy(mddev);
 abort:
 	bioset_exit(&mddev->io_clone_set);
 exit_sync_set:
@@ -6304,9 +6215,10 @@ int do_md_run(struct mddev *mddev)
 	err = md_run(mddev);
 	if (err)
 		goto out;
-	err = md_bitmap_load(mddev);
+
+	err = mddev->bitmap_ops->load(mddev);
 	if (err) {
-		md_bitmap_destroy(mddev);
+		mddev->bitmap_ops->destroy(mddev);
 		goto out;
 	}
 
@@ -6450,7 +6362,8 @@ static void __md_stop_writes(struct mddev *mddev)
 		mddev->pers->quiesce(mddev, 1);
 		mddev->pers->quiesce(mddev, 0);
 	}
-	md_bitmap_flush(mddev);
+
+	mddev->bitmap_ops->flush(mddev);
 
 	if (md_is_rdwr(mddev) &&
 	    ((!mddev->in_sync && !mddev_is_clustered(mddev)) ||
@@ -6477,7 +6390,7 @@ EXPORT_SYMBOL_GPL(md_stop_writes);
 
 static void mddev_detach(struct mddev *mddev)
 {
-	md_bitmap_wait_behind_writes(mddev);
+	mddev->bitmap_ops->wait_behind_writes(mddev);
 	if (mddev->pers && mddev->pers->quiesce && !is_md_suspended(mddev)) {
 		mddev->pers->quiesce(mddev, 1);
 		mddev->pers->quiesce(mddev, 0);
@@ -6492,7 +6405,8 @@ static void mddev_detach(struct mddev *mddev)
 static void __md_stop(struct mddev *mddev)
 {
 	struct md_personality *pers = mddev->pers;
-	md_bitmap_destroy(mddev);
+
+	mddev->bitmap_ops->destroy(mddev);
 	mddev_detach(mddev);
 	spin_lock(&mddev->lock);
 	mddev->pers = NULL;
@@ -7270,22 +7184,19 @@ static int set_bitmap_file(struct mddev *mddev, int fd)
 	err = 0;
 	if (mddev->pers) {
 		if (fd >= 0) {
-			struct bitmap *bitmap;
+			err = mddev->bitmap_ops->create(mddev, -1);
+			if (!err)
+				err = mddev->bitmap_ops->load(mddev);
 
-			bitmap = md_bitmap_create(mddev, -1);
-			if (!IS_ERR(bitmap)) {
-				mddev->bitmap = bitmap;
-				err = md_bitmap_load(mddev);
-			} else
-				err = PTR_ERR(bitmap);
 			if (err) {
-				md_bitmap_destroy(mddev);
+				mddev->bitmap_ops->destroy(mddev);
 				fd = -1;
 			}
 		} else if (fd < 0) {
-			md_bitmap_destroy(mddev);
+			mddev->bitmap_ops->destroy(mddev);
 		}
 	}
+
 	if (fd < 0) {
 		struct file *f = mddev->bitmap_info.file;
 		if (f) {
@@ -7554,7 +7465,6 @@ static int update_array_info(struct mddev *mddev, mdu_array_info_t *info)
 			goto err;
 		}
 		if (info->state & (1<<MD_SB_BITMAP_PRESENT)) {
-			struct bitmap *bitmap;
 			/* add the bitmap */
 			if (mddev->bitmap) {
 				rv = -EEXIST;
@@ -7568,24 +7478,24 @@ static int update_array_info(struct mddev *mddev, mdu_array_info_t *info)
 				mddev->bitmap_info.default_offset;
 			mddev->bitmap_info.space =
 				mddev->bitmap_info.default_space;
-			bitmap = md_bitmap_create(mddev, -1);
-			if (!IS_ERR(bitmap)) {
-				mddev->bitmap = bitmap;
-				rv = md_bitmap_load(mddev);
-			} else
-				rv = PTR_ERR(bitmap);
+			rv = mddev->bitmap_ops->create(mddev, -1);
+			if (!rv)
+				rv = mddev->bitmap_ops->load(mddev);
+
 			if (rv)
-				md_bitmap_destroy(mddev);
+				mddev->bitmap_ops->destroy(mddev);
 		} else {
-			/* remove the bitmap */
-			if (!mddev->bitmap) {
-				rv = -ENOENT;
+			struct md_bitmap_stats stats;
+
+			rv = mddev->bitmap_ops->get_stats(mddev->bitmap, &stats);
+			if (rv)
 				goto err;
-			}
-			if (mddev->bitmap->storage.file) {
+
+			if (stats.file) {
 				rv = -EINVAL;
 				goto err;
 			}
+
 			if (mddev->bitmap_info.nodes) {
 				/* hold PW on all the bitmap lock */
 				if (md_cluster_ops->lock_all_bitmaps(mddev) <= 0) {
@@ -7600,7 +7510,7 @@ static int update_array_info(struct mddev *mddev, mdu_array_info_t *info)
 				module_put(md_cluster_mod);
 				mddev->safemode_delay = DEFAULT_SAFEMODE_DELAY;
 			}
-			md_bitmap_destroy(mddev);
+			mddev->bitmap_ops->destroy(mddev);
 			mddev->bitmap_info.offset = 0;
 		}
 	}
@@ -8370,6 +8280,33 @@ static void md_seq_stop(struct seq_file *seq, void *v)
 	spin_unlock(&all_mddevs_lock);
 }
 
+static void md_bitmap_status(struct seq_file *seq, struct mddev *mddev)
+{
+	struct md_bitmap_stats stats;
+	unsigned long used_pages;
+	unsigned long chunk_kb;
+	int err;
+
+	err = mddev->bitmap_ops->get_stats(mddev->bitmap, &stats);
+	if (err)
+		return;
+
+	chunk_kb = mddev->bitmap_info.chunksize >> 10;
+	used_pages = stats.pages - stats.missing_pages;
+
+	seq_printf(seq, "bitmap: %lu/%lu pages [%luKB], %lu%s chunk",
+		   used_pages, stats.pages, used_pages << (PAGE_SHIFT - 10),
+		   chunk_kb ? chunk_kb : mddev->bitmap_info.chunksize,
+		   chunk_kb ? "KB" : "B");
+
+	if (stats.file) {
+		seq_puts(seq, ", file: ");
+		seq_file_path(seq, stats.file, " \t\n");
+	}
+
+	seq_putc(seq, '\n');
+}
+
 static int md_seq_show(struct seq_file *seq, void *v)
 {
 	struct mddev *mddev;
@@ -8453,7 +8390,7 @@ static int md_seq_show(struct seq_file *seq, void *v)
 		} else
 			seq_printf(seq, "\n       ");
 
-		md_bitmap_status(seq, mddev->bitmap);
+		md_bitmap_status(seq, mddev);
 
 		seq_printf(seq, "\n");
 	}
@@ -8668,7 +8605,6 @@ void md_write_start(struct mddev *mddev, struct bio *bi)
 	BUG_ON(mddev->ro == MD_RDONLY);
 	if (mddev->ro == MD_AUTO_READ) {
 		/* need to switch to read/write */
-		flush_work(&mddev->sync_work);
 		mddev->ro = MD_RDWR;
 		set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
 		md_wakeup_thread(mddev->thread);
@@ -9506,7 +9442,7 @@ static void md_start_sync(struct work_struct *ws)
 	 * stored on all devices. So make sure all bitmap pages get written.
 	 */
 	if (spares)
-		md_bitmap_write_all(mddev->bitmap);
+		mddev->bitmap_ops->write_all(mddev);
 
 	name = test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery) ?
 			"reshape" : "resync";
@@ -9594,7 +9530,7 @@ static void unregister_sync_thread(struct mddev *mddev)
 void md_check_recovery(struct mddev *mddev)
 {
 	if (mddev->bitmap)
-		md_bitmap_daemon_work(mddev);
+		mddev->bitmap_ops->daemon_work(mddev);
 
 	if (signal_pending(current)) {
 		if (mddev->pers->sync_request && !mddev->external) {
@@ -9965,7 +9901,7 @@ static void check_sb_changes(struct mddev *mddev, struct md_rdev *rdev)
 		if (ret)
 			pr_info("md-cluster: resize failed\n");
 		else
-			md_bitmap_update_sb(mddev->bitmap);
+			mddev->bitmap_ops->update_sb(mddev->bitmap);
 	}
 
 	/* Check for change of roles in the active devices */
diff --git a/drivers/md/md.h b/drivers/md/md.h
index a0d6827dced9..5d2e6bd58e4d 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -535,7 +535,8 @@ struct mddev {
 	struct percpu_ref		writes_pending;
 	int				sync_checkers;	/* # of threads checking writes_pending */
 
-	struct bitmap			*bitmap; /* the bitmap for the device */
+	void				*bitmap; /* the bitmap for the device */
+	struct bitmap_operations	*bitmap_ops;
 	struct {
 		struct file		*file; /* the bitmap file */
 		loff_t			offset; /* offset from superblock of
@@ -571,16 +572,6 @@ struct mddev {
 						   */
 	struct bio_set			io_clone_set;
 
-	/* Generic flush handling.
-	 * The last to finish preflush schedules a worker to submit
-	 * the rest of the request (without the REQ_PREFLUSH flag).
-	 */
-	struct bio *flush_bio;
-	atomic_t flush_pending;
-	ktime_t start_flush, prev_flush_start; /* prev_flush_start is when the previous completed
-						* flush was started.
-						*/
-	struct work_struct flush_work;
 	struct work_struct event_work;	/* used by dm to report failure event */
 	mempool_t *serial_info_pool;
 	void (*sync_super)(struct mddev *mddev, struct md_rdev *rdev);
diff --git a/drivers/md/raid1-10.c b/drivers/md/raid1-10.c
index 2ea1710a3b70..4378d3250bd7 100644
--- a/drivers/md/raid1-10.c
+++ b/drivers/md/raid1-10.c
@@ -140,7 +140,7 @@ static inline bool raid1_add_bio_to_plug(struct mddev *mddev, struct bio *bio,
 	 * If bitmap is not enabled, it's safe to submit the io directly, and
 	 * this can get optimal performance.
 	 */
-	if (!md_bitmap_enabled(mddev->bitmap)) {
+	if (!mddev->bitmap_ops->enabled(mddev)) {
 		raid1_submit_write(bio);
 		return true;
 	}
@@ -166,12 +166,9 @@ static inline bool raid1_add_bio_to_plug(struct mddev *mddev, struct bio *bio,
  * while current io submission must wait for bitmap io to be done. In order to
  * avoid such deadlock, submit bitmap io asynchronously.
  */
-static inline void raid1_prepare_flush_writes(struct bitmap *bitmap)
+static inline void raid1_prepare_flush_writes(struct mddev *mddev)
 {
-	if (current->bio_list)
-		md_bitmap_unplug_async(bitmap);
-	else
-		md_bitmap_unplug(bitmap);
+	mddev->bitmap_ops->unplug(mddev, current->bio_list == NULL);
 }
 
 /*
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 7acfe7c9dc8d..f55c8e67d059 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -411,18 +411,20 @@ static void raid1_end_read_request(struct bio *bio)
 
 static void close_write(struct r1bio *r1_bio)
 {
+	struct mddev *mddev = r1_bio->mddev;
+
 	/* it really is the end of this request */
 	if (test_bit(R1BIO_BehindIO, &r1_bio->state)) {
 		bio_free_pages(r1_bio->behind_master_bio);
 		bio_put(r1_bio->behind_master_bio);
 		r1_bio->behind_master_bio = NULL;
 	}
+
 	/* clear the bitmap if all writes complete successfully */
-	md_bitmap_endwrite(r1_bio->mddev->bitmap, r1_bio->sector,
-			   r1_bio->sectors,
-			   !test_bit(R1BIO_Degraded, &r1_bio->state),
-			   test_bit(R1BIO_BehindIO, &r1_bio->state));
-	md_write_end(r1_bio->mddev);
+	mddev->bitmap_ops->endwrite(mddev, r1_bio->sector, r1_bio->sectors,
+				    !test_bit(R1BIO_Degraded, &r1_bio->state),
+				    test_bit(R1BIO_BehindIO, &r1_bio->state));
+	md_write_end(mddev);
 }
 
 static void r1_bio_write_done(struct r1bio *r1_bio)
@@ -894,7 +896,7 @@ static void wake_up_barrier(struct r1conf *conf)
 static void flush_bio_list(struct r1conf *conf, struct bio *bio)
 {
 	/* flush any pending bitmap writes to disk before proceeding w/ I/O */
-	raid1_prepare_flush_writes(conf->mddev->bitmap);
+	raid1_prepare_flush_writes(conf->mddev);
 	wake_up_barrier(conf);
 
 	while (bio) { /* submit pending writes */
@@ -1311,13 +1313,11 @@ static void raid1_read_request(struct mddev *mddev, struct bio *bio,
 	struct r1conf *conf = mddev->private;
 	struct raid1_info *mirror;
 	struct bio *read_bio;
-	struct bitmap *bitmap = mddev->bitmap;
 	const enum req_op op = bio_op(bio);
 	const blk_opf_t do_sync = bio->bi_opf & REQ_SYNC;
 	int max_sectors;
 	int rdisk;
 	bool r1bio_existed = !!r1_bio;
-	char b[BDEVNAME_SIZE];
 
 	/*
 	 * If r1_bio is set, we are blocking the raid1d thread
@@ -1326,16 +1326,6 @@ static void raid1_read_request(struct mddev *mddev, struct bio *bio,
 	 */
 	gfp_t gfp = r1_bio ? (GFP_NOIO | __GFP_HIGH) : GFP_NOIO;
 
-	if (r1bio_existed) {
-		/* Need to get the block device name carefully */
-		struct md_rdev *rdev = conf->mirrors[r1_bio->read_disk].rdev;
-
-		if (rdev)
-			snprintf(b, sizeof(b), "%pg", rdev->bdev);
-		else
-			strcpy(b, "???");
-	}
-
 	/*
 	 * Still need barrier for READ in case that whole
 	 * array is frozen.
@@ -1357,15 +1347,13 @@ static void raid1_read_request(struct mddev *mddev, struct bio *bio,
 	 * used and no empty request is available.
 	 */
 	rdisk = read_balance(conf, r1_bio, &max_sectors);
-
 	if (rdisk < 0) {
 		/* couldn't find anywhere to read from */
-		if (r1bio_existed) {
-			pr_crit_ratelimited("md/raid1:%s: %s: unrecoverable I/O read error for block %llu\n",
+		if (r1bio_existed)
+			pr_crit_ratelimited("md/raid1:%s: %pg: unrecoverable I/O read error for block %llu\n",
 					    mdname(mddev),
-					    b,
-					    (unsigned long long)r1_bio->sector);
-		}
+					    conf->mirrors[r1_bio->read_disk].rdev->bdev,
+					    r1_bio->sector);
 		raid_end_bio_io(r1_bio);
 		return;
 	}
@@ -1377,15 +1365,13 @@ static void raid1_read_request(struct mddev *mddev, struct bio *bio,
 				    (unsigned long long)r1_bio->sector,
 				    mirror->rdev->bdev);
 
-	if (test_bit(WriteMostly, &mirror->rdev->flags) &&
-	    bitmap) {
+	if (test_bit(WriteMostly, &mirror->rdev->flags)) {
 		/*
 		 * Reading from a write-mostly device must take care not to
 		 * over-take any writes that are 'behind'
 		 */
 		mddev_add_trace_msg(mddev, "raid1 wait behind writes");
-		wait_event(bitmap->behind_wait,
-			   atomic_read(&bitmap->behind_writes) == 0);
+		mddev->bitmap_ops->wait_behind_writes(mddev);
 	}
 
 	if (max_sectors < bio_sectors(bio)) {
@@ -1426,7 +1412,6 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio,
 	struct r1conf *conf = mddev->private;
 	struct r1bio *r1_bio;
 	int i, disks;
-	struct bitmap *bitmap = mddev->bitmap;
 	unsigned long flags;
 	struct md_rdev *blocked_rdev;
 	int first_clone;
@@ -1579,7 +1564,7 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio,
 	 * at a time and thus needs a new bio that can fit the whole payload
 	 * this bio in page sized chunks.
 	 */
-	if (write_behind && bitmap)
+	if (write_behind && mddev->bitmap)
 		max_sectors = min_t(int, max_sectors,
 				    BIO_MAX_VECS * (PAGE_SIZE >> 9));
 	if (max_sectors < bio_sectors(bio)) {
@@ -1606,19 +1591,23 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio,
 			continue;
 
 		if (first_clone) {
+			unsigned long max_write_behind =
+				mddev->bitmap_info.max_write_behind;
+			struct md_bitmap_stats stats;
+			int err;
+
 			/* do behind I/O ?
 			 * Not if there are too many, or cannot
 			 * allocate memory, or a reader on WriteMostly
 			 * is waiting for behind writes to flush */
-			if (bitmap && write_behind &&
-			    (atomic_read(&bitmap->behind_writes)
-			     < mddev->bitmap_info.max_write_behind) &&
-			    !waitqueue_active(&bitmap->behind_wait)) {
+			err = mddev->bitmap_ops->get_stats(mddev->bitmap, &stats);
+			if (!err && write_behind && !stats.behind_wait &&
+			    stats.behind_writes < max_write_behind)
 				alloc_behind_master_bio(r1_bio, bio);
-			}
 
-			md_bitmap_startwrite(bitmap, r1_bio->sector, r1_bio->sectors,
-					     test_bit(R1BIO_BehindIO, &r1_bio->state));
+			mddev->bitmap_ops->startwrite(
+				mddev, r1_bio->sector, r1_bio->sectors,
+				test_bit(R1BIO_BehindIO, &r1_bio->state));
 			first_clone = 0;
 		}
 
@@ -2036,7 +2025,7 @@ static void abort_sync_write(struct mddev *mddev, struct r1bio *r1_bio)
 
 	/* make sure these bits don't get cleared. */
 	do {
-		md_bitmap_end_sync(mddev->bitmap, s, &sync_blocks, 1);
+		mddev->bitmap_ops->end_sync(mddev, s, &sync_blocks);
 		s += sync_blocks;
 		sectors_to_go -= sync_blocks;
 	} while (sectors_to_go > 0);
@@ -2765,7 +2754,7 @@ static sector_t raid1_sync_request(struct mddev *mddev, sector_t sector_nr,
 	int wonly = -1;
 	int write_targets = 0, read_targets = 0;
 	sector_t sync_blocks;
-	int still_degraded = 0;
+	bool still_degraded = false;
 	int good_sectors = RESYNC_SECTORS;
 	int min_bad = 0; /* number of sectors that are bad in all devices */
 	int idx = sector_to_idx(sector_nr);
@@ -2782,12 +2771,12 @@ static sector_t raid1_sync_request(struct mddev *mddev, sector_t sector_nr,
 		 * We can find the current addess in mddev->curr_resync
 		 */
 		if (mddev->curr_resync < max_sector) /* aborted */
-			md_bitmap_end_sync(mddev->bitmap, mddev->curr_resync,
-					   &sync_blocks, 1);
+			mddev->bitmap_ops->end_sync(mddev, mddev->curr_resync,
+						    &sync_blocks);
 		else /* completed sync */
 			conf->fullsync = 0;
 
-		md_bitmap_close_sync(mddev->bitmap);
+		mddev->bitmap_ops->close_sync(mddev);
 		close_sync(conf);
 
 		if (mddev_is_clustered(mddev)) {
@@ -2807,7 +2796,7 @@ static sector_t raid1_sync_request(struct mddev *mddev, sector_t sector_nr,
 	/* before building a request, check if we can skip these blocks..
 	 * This call the bitmap_start_sync doesn't actually record anything
 	 */
-	if (!md_bitmap_start_sync(mddev->bitmap, sector_nr, &sync_blocks, 1) &&
+	if (!mddev->bitmap_ops->start_sync(mddev, sector_nr, &sync_blocks, true) &&
 	    !conf->fullsync && !test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery)) {
 		/* We can skip this block, and probably several more */
 		*skipped = 1;
@@ -2825,9 +2814,9 @@ static sector_t raid1_sync_request(struct mddev *mddev, sector_t sector_nr,
 	 * sector_nr + two times RESYNC_SECTORS
 	 */
 
-	md_bitmap_cond_end_sync(mddev->bitmap, sector_nr,
-		mddev_is_clustered(mddev) && (sector_nr + 2 * RESYNC_SECTORS > conf->cluster_sync_high));
-
+	mddev->bitmap_ops->cond_end_sync(mddev, sector_nr,
+		mddev_is_clustered(mddev) &&
+		(sector_nr + 2 * RESYNC_SECTORS > conf->cluster_sync_high));
 
 	if (raise_barrier(conf, sector_nr))
 		return 0;
@@ -2858,7 +2847,7 @@ static sector_t raid1_sync_request(struct mddev *mddev, sector_t sector_nr,
 		if (rdev == NULL ||
 		    test_bit(Faulty, &rdev->flags)) {
 			if (i < conf->raid_disks)
-				still_degraded = 1;
+				still_degraded = true;
 		} else if (!test_bit(In_sync, &rdev->flags)) {
 			bio->bi_opf = REQ_OP_WRITE;
 			bio->bi_end_io = end_sync_write;
@@ -2982,8 +2971,8 @@ static sector_t raid1_sync_request(struct mddev *mddev, sector_t sector_nr,
 		if (len == 0)
 			break;
 		if (sync_blocks == 0) {
-			if (!md_bitmap_start_sync(mddev->bitmap, sector_nr,
-						  &sync_blocks, still_degraded) &&
+			if (!mddev->bitmap_ops->start_sync(mddev, sector_nr,
+						&sync_blocks, still_degraded) &&
 			    !conf->fullsync &&
 			    !test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery))
 				break;
@@ -3307,14 +3296,16 @@ static int raid1_resize(struct mddev *mddev, sector_t sectors)
 	 * worth it.
 	 */
 	sector_t newsize = raid1_size(mddev, sectors, 0);
+	int ret;
+
 	if (mddev->external_size &&
 	    mddev->array_sectors > newsize)
 		return -EINVAL;
-	if (mddev->bitmap) {
-		int ret = md_bitmap_resize(mddev->bitmap, newsize, 0, 0);
-		if (ret)
-			return ret;
-	}
+
+	ret = mddev->bitmap_ops->resize(mddev, newsize, 0, false);
+	if (ret)
+		return ret;
+
 	md_set_array_sectors(mddev, newsize);
 	if (sectors > mddev->dev_sectors &&
 	    mddev->recovery_cp > mddev->dev_sectors) {
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 2a9c4ee982e0..f3bf1116794a 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -426,12 +426,13 @@ static void raid10_end_read_request(struct bio *bio)
 
 static void close_write(struct r10bio *r10_bio)
 {
+	struct mddev *mddev = r10_bio->mddev;
+
 	/* clear the bitmap if all writes complete successfully */
-	md_bitmap_endwrite(r10_bio->mddev->bitmap, r10_bio->sector,
-			   r10_bio->sectors,
-			   !test_bit(R10BIO_Degraded, &r10_bio->state),
-			   0);
-	md_write_end(r10_bio->mddev);
+	mddev->bitmap_ops->endwrite(mddev, r10_bio->sector, r10_bio->sectors,
+				    !test_bit(R10BIO_Degraded, &r10_bio->state),
+				    false);
+	md_write_end(mddev);
 }
 
 static void one_write_done(struct r10bio *r10_bio)
@@ -884,7 +885,7 @@ static void flush_pending_writes(struct r10conf *conf)
 		__set_current_state(TASK_RUNNING);
 
 		blk_start_plug(&plug);
-		raid1_prepare_flush_writes(conf->mddev->bitmap);
+		raid1_prepare_flush_writes(conf->mddev);
 		wake_up(&conf->wait_barrier);
 
 		while (bio) { /* submit pending writes */
@@ -1100,7 +1101,7 @@ static void raid10_unplug(struct blk_plug_cb *cb, bool from_schedule)
 
 	/* we aren't scheduling, so we can do the write-out directly. */
 	bio = bio_list_get(&plug->pending);
-	raid1_prepare_flush_writes(mddev->bitmap);
+	raid1_prepare_flush_writes(mddev);
 	wake_up_barrier(conf);
 
 	while (bio) { /* submit pending writes */
@@ -1492,7 +1493,8 @@ static void raid10_write_request(struct mddev *mddev, struct bio *bio,
 	md_account_bio(mddev, &bio);
 	r10_bio->master_bio = bio;
 	atomic_set(&r10_bio->remaining, 1);
-	md_bitmap_startwrite(mddev->bitmap, r10_bio->sector, r10_bio->sectors, 0);
+	mddev->bitmap_ops->startwrite(mddev, r10_bio->sector, r10_bio->sectors,
+				      false);
 
 	for (i = 0; i < conf->copies; i++) {
 		if (r10_bio->devs[i].bio)
@@ -2465,7 +2467,7 @@ static void fix_recovery_read_error(struct r10bio *r10_bio)
 			s = PAGE_SIZE >> 9;
 
 		rdev = conf->mirrors[dr].rdev;
-		addr = r10_bio->devs[0].addr + sect,
+		addr = r10_bio->devs[0].addr + sect;
 		ok = sync_page_io(rdev,
 				  addr,
 				  s << 9,
@@ -3192,13 +3194,15 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
 
 		if (mddev->curr_resync < max_sector) { /* aborted */
 			if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery))
-				md_bitmap_end_sync(mddev->bitmap, mddev->curr_resync,
-						   &sync_blocks, 1);
+				mddev->bitmap_ops->end_sync(mddev,
+							    mddev->curr_resync,
+							    &sync_blocks);
 			else for (i = 0; i < conf->geo.raid_disks; i++) {
 				sector_t sect =
 					raid10_find_virt(conf, mddev->curr_resync, i);
-				md_bitmap_end_sync(mddev->bitmap, sect,
-						   &sync_blocks, 1);
+
+				mddev->bitmap_ops->end_sync(mddev, sect,
+							    &sync_blocks);
 			}
 		} else {
 			/* completed sync */
@@ -3218,7 +3222,7 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
 			}
 			conf->fullsync = 0;
 		}
-		md_bitmap_close_sync(mddev->bitmap);
+		mddev->bitmap_ops->close_sync(mddev);
 		close_sync(conf);
 		*skipped = 1;
 		return sectors_skipped;
@@ -3287,10 +3291,10 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
 		r10_bio = NULL;
 
 		for (i = 0 ; i < conf->geo.raid_disks; i++) {
-			int still_degraded;
+			bool still_degraded;
 			struct r10bio *rb2;
 			sector_t sect;
-			int must_sync;
+			bool must_sync;
 			int any_working;
 			struct raid10_info *mirror = &conf->mirrors[i];
 			struct md_rdev *mrdev, *mreplace;
@@ -3307,7 +3311,7 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
 			if (!mrdev && !mreplace)
 				continue;
 
-			still_degraded = 0;
+			still_degraded = false;
 			/* want to reconstruct this device */
 			rb2 = r10_bio;
 			sect = raid10_find_virt(conf, sector_nr, i);
@@ -3320,8 +3324,9 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
 			 * we only need to recover the block if it is set in
 			 * the bitmap
 			 */
-			must_sync = md_bitmap_start_sync(mddev->bitmap, sect,
-							 &sync_blocks, 1);
+			must_sync = mddev->bitmap_ops->start_sync(mddev, sect,
+								  &sync_blocks,
+								  true);
 			if (sync_blocks < max_sync)
 				max_sync = sync_blocks;
 			if (!must_sync &&
@@ -3359,13 +3364,13 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
 				struct md_rdev *rdev = conf->mirrors[j].rdev;
 
 				if (rdev == NULL || test_bit(Faulty, &rdev->flags)) {
-					still_degraded = 1;
+					still_degraded = false;
 					break;
 				}
 			}
 
-			must_sync = md_bitmap_start_sync(mddev->bitmap, sect,
-							 &sync_blocks, still_degraded);
+			must_sync = mddev->bitmap_ops->start_sync(mddev, sect,
+						&sync_blocks, still_degraded);
 
 			any_working = 0;
 			for (j=0; j<conf->copies;j++) {
@@ -3538,12 +3543,13 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
 		 * safety reason, which ensures curr_resync_completed is
 		 * updated in bitmap_cond_end_sync.
 		 */
-		md_bitmap_cond_end_sync(mddev->bitmap, sector_nr,
+		mddev->bitmap_ops->cond_end_sync(mddev, sector_nr,
 					mddev_is_clustered(mddev) &&
 					(sector_nr + 2 * RESYNC_SECTORS > conf->cluster_sync_high));
 
-		if (!md_bitmap_start_sync(mddev->bitmap, sector_nr,
-					  &sync_blocks, mddev->degraded) &&
+		if (!mddev->bitmap_ops->start_sync(mddev, sector_nr,
+						   &sync_blocks,
+						   mddev->degraded) &&
 		    !conf->fullsync && !test_bit(MD_RECOVERY_REQUESTED,
 						 &mddev->recovery)) {
 			/* We can skip this block */
@@ -4190,6 +4196,7 @@ static int raid10_resize(struct mddev *mddev, sector_t sectors)
 	 */
 	struct r10conf *conf = mddev->private;
 	sector_t oldsize, size;
+	int ret;
 
 	if (mddev->reshape_position != MaxSector)
 		return -EBUSY;
@@ -4202,11 +4209,11 @@ static int raid10_resize(struct mddev *mddev, sector_t sectors)
 	if (mddev->external_size &&
 	    mddev->array_sectors > size)
 		return -EINVAL;
-	if (mddev->bitmap) {
-		int ret = md_bitmap_resize(mddev->bitmap, size, 0, 0);
-		if (ret)
-			return ret;
-	}
+
+	ret = mddev->bitmap_ops->resize(mddev, size, 0, false);
+	if (ret)
+		return ret;
+
 	md_set_array_sectors(mddev, size);
 	if (sectors > mddev->dev_sectors &&
 	    mddev->recovery_cp > oldsize) {
@@ -4472,7 +4479,7 @@ static int raid10_start_reshape(struct mddev *mddev)
 		newsize = raid10_size(mddev, 0, conf->geo.raid_disks);
 
 		if (!mddev_is_clustered(mddev)) {
-			ret = md_bitmap_resize(mddev->bitmap, newsize, 0, 0);
+			ret = mddev->bitmap_ops->resize(mddev, newsize, 0, false);
 			if (ret)
 				goto abort;
 			else
@@ -4487,20 +4494,20 @@ static int raid10_start_reshape(struct mddev *mddev)
 
 		/*
 		 * some node is already performing reshape, and no need to
-		 * call md_bitmap_resize again since it should be called when
+		 * call bitmap_ops->resize again since it should be called when
 		 * receiving BITMAP_RESIZE msg
 		 */
 		if ((sb && (le32_to_cpu(sb->feature_map) &
 			    MD_FEATURE_RESHAPE_ACTIVE)) || (oldsize == newsize))
 			goto out;
 
-		ret = md_bitmap_resize(mddev->bitmap, newsize, 0, 0);
+		ret = mddev->bitmap_ops->resize(mddev, newsize, 0, false);
 		if (ret)
 			goto abort;
 
 		ret = md_cluster_ops->resize_bitmaps(mddev, newsize, oldsize);
 		if (ret) {
-			md_bitmap_resize(mddev->bitmap, oldsize, 0, 0);
+			mddev->bitmap_ops->resize(mddev, oldsize, 0, false);
 			goto abort;
 		}
 	}
diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c
index 874874fe4fa1..b4f7b79fd187 100644
--- a/drivers/md/raid5-cache.c
+++ b/drivers/md/raid5-cache.c
@@ -313,10 +313,10 @@ void r5c_handle_cached_data_endio(struct r5conf *conf,
 		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);
+			conf->mddev->bitmap_ops->endwrite(conf->mddev,
+					sh->sector, RAID5_STRIPE_SECTORS(conf),
+					!test_bit(STRIPE_DEGRADED, &sh->state),
+					false);
 		}
 	}
 }
@@ -2798,7 +2798,6 @@ void r5c_finish_stripe_write_out(struct r5conf *conf,
 {
 	struct r5l_log *log = READ_ONCE(conf->log);
 	int i;
-	int do_wakeup = 0;
 	sector_t tree_index;
 	void __rcu **pslot;
 	uintptr_t refcount;
@@ -2815,7 +2814,7 @@ void r5c_finish_stripe_write_out(struct r5conf *conf,
 	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;
+			wake_up_bit(&sh->dev[i].flags, R5_Overlap);
 	}
 
 	/*
@@ -2828,9 +2827,6 @@ void r5c_finish_stripe_write_out(struct r5conf *conf,
 		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);
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index c14cf2410365..dc2ea636d173 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -2337,7 +2337,7 @@ static void raid_run_ops(struct stripe_head *sh, unsigned long ops_request)
 		for (i = disks; i--; ) {
 			struct r5dev *dev = &sh->dev[i];
 			if (test_and_clear_bit(R5_Overlap, &dev->flags))
-				wake_up(&sh->raid_conf->wait_for_overlap);
+				wake_up_bit(&dev->flags, R5_Overlap);
 		}
 	}
 	local_unlock(&conf->percpu->lock);
@@ -3473,7 +3473,7 @@ static bool stripe_bio_overlaps(struct stripe_head *sh, struct bio *bi,
 		 * With PPL only writes to consecutive data chunks within a
 		 * stripe are allowed because for a single stripe_head we can
 		 * only have one PPL entry at a time, which describes one data
-		 * range. Not really an overlap, but wait_for_overlap can be
+		 * range. Not really an overlap, but R5_Overlap can be
 		 * used to handle this.
 		 */
 		sector_t sector;
@@ -3563,8 +3563,8 @@ static void __add_stripe_bio(struct stripe_head *sh, struct bio *bi,
 		 */
 		set_bit(STRIPE_BITMAP_PENDING, &sh->state);
 		spin_unlock_irq(&sh->stripe_lock);
-		md_bitmap_startwrite(conf->mddev->bitmap, sh->sector,
-				     RAID5_STRIPE_SECTORS(conf), 0);
+		conf->mddev->bitmap_ops->startwrite(conf->mddev, sh->sector,
+					RAID5_STRIPE_SECTORS(conf), false);
 		spin_lock_irq(&sh->stripe_lock);
 		clear_bit(STRIPE_BITMAP_PENDING, &sh->state);
 		if (!sh->batch_head) {
@@ -3652,7 +3652,7 @@ handle_failed_stripe(struct r5conf *conf, struct stripe_head *sh,
 		log_stripe_write_finished(sh);
 
 		if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
-			wake_up(&conf->wait_for_overlap);
+			wake_up_bit(&sh->dev[i].flags, R5_Overlap);
 
 		while (bi && bi->bi_iter.bi_sector <
 			sh->dev[i].sector + RAID5_STRIPE_SECTORS(conf)) {
@@ -3663,8 +3663,9 @@ handle_failed_stripe(struct r5conf *conf, struct stripe_head *sh,
 			bi = nextbi;
 		}
 		if (bitmap_end)
-			md_bitmap_endwrite(conf->mddev->bitmap, sh->sector,
-					   RAID5_STRIPE_SECTORS(conf), 0, 0);
+			conf->mddev->bitmap_ops->endwrite(conf->mddev,
+					sh->sector, RAID5_STRIPE_SECTORS(conf),
+					false, false);
 		bitmap_end = 0;
 		/* and fail all 'written' */
 		bi = sh->dev[i].written;
@@ -3696,7 +3697,7 @@ handle_failed_stripe(struct r5conf *conf, struct stripe_head *sh,
 			sh->dev[i].toread = NULL;
 			spin_unlock_irq(&sh->stripe_lock);
 			if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
-				wake_up(&conf->wait_for_overlap);
+				wake_up_bit(&sh->dev[i].flags, R5_Overlap);
 			if (bi)
 				s->to_read--;
 			while (bi && bi->bi_iter.bi_sector <
@@ -3709,8 +3710,9 @@ handle_failed_stripe(struct r5conf *conf, struct stripe_head *sh,
 			}
 		}
 		if (bitmap_end)
-			md_bitmap_endwrite(conf->mddev->bitmap, sh->sector,
-					   RAID5_STRIPE_SECTORS(conf), 0, 0);
+			conf->mddev->bitmap_ops->endwrite(conf->mddev,
+					sh->sector, RAID5_STRIPE_SECTORS(conf),
+					false, false);
 		/* If we were in the middle of a write the parity block might
 		 * still be locked - so just clear all R5_LOCKED flags
 		 */
@@ -3734,7 +3736,7 @@ handle_failed_sync(struct r5conf *conf, struct stripe_head *sh,
 	BUG_ON(sh->batch_head);
 	clear_bit(STRIPE_SYNCING, &sh->state);
 	if (test_and_clear_bit(R5_Overlap, &sh->dev[sh->pd_idx].flags))
-		wake_up(&conf->wait_for_overlap);
+		wake_up_bit(&sh->dev[sh->pd_idx].flags, R5_Overlap);
 	s->syncing = 0;
 	s->replacing = 0;
 	/* There is nothing more to do for sync/check/repair.
@@ -4059,10 +4061,10 @@ returnbi:
 					bio_endio(wbi);
 					wbi = wbi2;
 				}
-				md_bitmap_endwrite(conf->mddev->bitmap, sh->sector,
-						   RAID5_STRIPE_SECTORS(conf),
-						   !test_bit(STRIPE_DEGRADED, &sh->state),
-						   0);
+				conf->mddev->bitmap_ops->endwrite(conf->mddev,
+					sh->sector, RAID5_STRIPE_SECTORS(conf),
+					!test_bit(STRIPE_DEGRADED, &sh->state),
+					false);
 				if (head_sh->batch_head) {
 					sh = list_first_entry(&sh->batch_list,
 							      struct stripe_head,
@@ -4875,7 +4877,6 @@ static void break_stripe_batch_list(struct stripe_head *head_sh,
 {
 	struct stripe_head *sh, *next;
 	int i;
-	int do_wakeup = 0;
 
 	list_for_each_entry_safe(sh, next, &head_sh->batch_list, batch_list) {
 
@@ -4911,7 +4912,7 @@ static void break_stripe_batch_list(struct stripe_head *head_sh,
 		spin_unlock_irq(&sh->stripe_lock);
 		for (i = 0; i < sh->disks; i++) {
 			if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
-				do_wakeup = 1;
+				wake_up_bit(&sh->dev[i].flags, R5_Overlap);
 			sh->dev[i].flags = head_sh->dev[i].flags &
 				(~((1 << R5_WriteError) | (1 << R5_Overlap)));
 		}
@@ -4925,12 +4926,9 @@ static void break_stripe_batch_list(struct stripe_head *head_sh,
 	spin_unlock_irq(&head_sh->stripe_lock);
 	for (i = 0; i < head_sh->disks; i++)
 		if (test_and_clear_bit(R5_Overlap, &head_sh->dev[i].flags))
-			do_wakeup = 1;
+			wake_up_bit(&head_sh->dev[i].flags, R5_Overlap);
 	if (head_sh->state & handle_flags)
 		set_bit(STRIPE_HANDLE, &head_sh->state);
-
-	if (do_wakeup)
-		wake_up(&head_sh->raid_conf->wait_for_overlap);
 }
 
 static void handle_stripe(struct stripe_head *sh)
@@ -5196,7 +5194,7 @@ static void handle_stripe(struct stripe_head *sh)
 		md_done_sync(conf->mddev, RAID5_STRIPE_SECTORS(conf), 1);
 		clear_bit(STRIPE_SYNCING, &sh->state);
 		if (test_and_clear_bit(R5_Overlap, &sh->dev[sh->pd_idx].flags))
-			wake_up(&conf->wait_for_overlap);
+			wake_up_bit(&sh->dev[sh->pd_idx].flags, R5_Overlap);
 	}
 
 	/* If the failed drives are just a ReadError, then we might need
@@ -5259,7 +5257,7 @@ static void handle_stripe(struct stripe_head *sh)
 	} else if (s.expanded && !sh->reconstruct_state && s.locked == 0) {
 		clear_bit(STRIPE_EXPAND_READY, &sh->state);
 		atomic_dec(&conf->reshape_stripes);
-		wake_up(&conf->wait_for_overlap);
+		wake_up(&conf->wait_for_reshape);
 		md_done_sync(conf->mddev, RAID5_STRIPE_SECTORS(conf), 1);
 	}
 
@@ -5753,12 +5751,11 @@ static void make_discard_request(struct mddev *mddev, struct bio *bi)
 		int d;
 	again:
 		sh = raid5_get_active_stripe(conf, NULL, logical_sector, 0);
-		prepare_to_wait(&conf->wait_for_overlap, &w,
-				TASK_UNINTERRUPTIBLE);
 		set_bit(R5_Overlap, &sh->dev[sh->pd_idx].flags);
 		if (test_bit(STRIPE_SYNCING, &sh->state)) {
 			raid5_release_stripe(sh);
-			schedule();
+			wait_on_bit(&sh->dev[sh->pd_idx].flags, R5_Overlap,
+				    TASK_UNINTERRUPTIBLE);
 			goto again;
 		}
 		clear_bit(R5_Overlap, &sh->dev[sh->pd_idx].flags);
@@ -5770,12 +5767,12 @@ static void make_discard_request(struct mddev *mddev, struct bio *bi)
 				set_bit(R5_Overlap, &sh->dev[d].flags);
 				spin_unlock_irq(&sh->stripe_lock);
 				raid5_release_stripe(sh);
-				schedule();
+				wait_on_bit(&sh->dev[d].flags, R5_Overlap,
+					    TASK_UNINTERRUPTIBLE);
 				goto again;
 			}
 		}
 		set_bit(STRIPE_DISCARD, &sh->state);
-		finish_wait(&conf->wait_for_overlap, &w);
 		sh->overwrite_disks = 0;
 		for (d = 0; d < conf->raid_disks; d++) {
 			if (d == sh->pd_idx || d == sh->qd_idx)
@@ -5788,13 +5785,10 @@ static void make_discard_request(struct mddev *mddev, struct bio *bi)
 		}
 		spin_unlock_irq(&sh->stripe_lock);
 		if (conf->mddev->bitmap) {
-			for (d = 0;
-			     d < conf->raid_disks - conf->max_degraded;
+			for (d = 0; d < conf->raid_disks - conf->max_degraded;
 			     d++)
-				md_bitmap_startwrite(mddev->bitmap,
-						     sh->sector,
-						     RAID5_STRIPE_SECTORS(conf),
-						     0);
+				mddev->bitmap_ops->startwrite(mddev, sh->sector,
+					RAID5_STRIPE_SECTORS(conf), false);
 			sh->bm_seq = conf->seq_flush + 1;
 			set_bit(STRIPE_BIT_DELAY, &sh->state);
 		}
@@ -5855,7 +5849,6 @@ static int add_all_stripe_bios(struct r5conf *conf,
 		struct bio *bi, int forwrite, int previous)
 {
 	int dd_idx;
-	int ret = 1;
 
 	spin_lock_irq(&sh->stripe_lock);
 
@@ -5871,14 +5864,19 @@ static int add_all_stripe_bios(struct r5conf *conf,
 
 		if (stripe_bio_overlaps(sh, bi, dd_idx, forwrite)) {
 			set_bit(R5_Overlap, &dev->flags);
-			ret = 0;
-			continue;
+			spin_unlock_irq(&sh->stripe_lock);
+			raid5_release_stripe(sh);
+			/* release batch_last before wait to avoid risk of deadlock */
+			if (ctx->batch_last) {
+				raid5_release_stripe(ctx->batch_last);
+				ctx->batch_last = NULL;
+			}
+			md_wakeup_thread(conf->mddev->thread);
+			wait_on_bit(&dev->flags, R5_Overlap, TASK_UNINTERRUPTIBLE);
+			return 0;
 		}
 	}
 
-	if (!ret)
-		goto out;
-
 	for (dd_idx = 0; dd_idx < sh->disks; dd_idx++) {
 		struct r5dev *dev = &sh->dev[dd_idx];
 
@@ -5894,9 +5892,8 @@ static int add_all_stripe_bios(struct r5conf *conf,
 			  RAID5_STRIPE_SHIFT(conf), ctx->sectors_to_do);
 	}
 
-out:
 	spin_unlock_irq(&sh->stripe_lock);
-	return ret;
+	return 1;
 }
 
 enum reshape_loc {
@@ -5992,17 +5989,17 @@ static enum stripe_result make_stripe_request(struct mddev *mddev,
 		goto out_release;
 	}
 
-	if (test_bit(STRIPE_EXPANDING, &sh->state) ||
-	    !add_all_stripe_bios(conf, ctx, sh, bi, rw, previous)) {
-		/*
-		 * Stripe is busy expanding or add failed due to
-		 * overlap. Flush everything and wait a while.
-		 */
+	if (test_bit(STRIPE_EXPANDING, &sh->state)) {
 		md_wakeup_thread(mddev->thread);
 		ret = STRIPE_SCHEDULE_AND_RETRY;
 		goto out_release;
 	}
 
+	if (!add_all_stripe_bios(conf, ctx, sh, bi, rw, previous)) {
+		ret = STRIPE_RETRY;
+		goto out;
+	}
+
 	if (stripe_can_batch(sh)) {
 		stripe_add_to_batch_list(conf, sh, ctx->batch_last);
 		if (ctx->batch_last)
@@ -6073,6 +6070,7 @@ static sector_t raid5_bio_lowest_chunk_sector(struct r5conf *conf,
 static bool raid5_make_request(struct mddev *mddev, struct bio * bi)
 {
 	DEFINE_WAIT_FUNC(wait, woken_wake_function);
+	bool on_wq;
 	struct r5conf *conf = mddev->private;
 	sector_t logical_sector;
 	struct stripe_request_ctx ctx = {};
@@ -6146,11 +6144,15 @@ static bool raid5_make_request(struct mddev *mddev, struct bio * bi)
 	 * sequential IO pattern. We don't bother with the optimization when
 	 * reshaping as the performance benefit is not worth the complexity.
 	 */
-	if (likely(conf->reshape_progress == MaxSector))
+	if (likely(conf->reshape_progress == MaxSector)) {
 		logical_sector = raid5_bio_lowest_chunk_sector(conf, bi);
+		on_wq = false;
+	} else {
+		add_wait_queue(&conf->wait_for_reshape, &wait);
+		on_wq = true;
+	}
 	s = (logical_sector - ctx.first_sector) >> RAID5_STRIPE_SHIFT(conf);
 
-	add_wait_queue(&conf->wait_for_overlap, &wait);
 	while (1) {
 		res = make_stripe_request(mddev, conf, &ctx, logical_sector,
 					  bi);
@@ -6161,6 +6163,7 @@ static bool raid5_make_request(struct mddev *mddev, struct bio * bi)
 			continue;
 
 		if (res == STRIPE_SCHEDULE_AND_RETRY) {
+			WARN_ON_ONCE(!on_wq);
 			/*
 			 * Must release the reference to batch_last before
 			 * scheduling and waiting for work to be done,
@@ -6185,7 +6188,8 @@ static bool raid5_make_request(struct mddev *mddev, struct bio * bi)
 		logical_sector = ctx.first_sector +
 			(s << RAID5_STRIPE_SHIFT(conf));
 	}
-	remove_wait_queue(&conf->wait_for_overlap, &wait);
+	if (unlikely(on_wq))
+		remove_wait_queue(&conf->wait_for_reshape, &wait);
 
 	if (ctx.batch_last)
 		raid5_release_stripe(ctx.batch_last);
@@ -6338,7 +6342,7 @@ static sector_t reshape_request(struct mddev *mddev, sector_t sector_nr, int *sk
 	     : (safepos < writepos && readpos > writepos)) ||
 	    time_after(jiffies, conf->reshape_checkpoint + 10*HZ)) {
 		/* Cannot proceed until we've updated the superblock... */
-		wait_event(conf->wait_for_overlap,
+		wait_event(conf->wait_for_reshape,
 			   atomic_read(&conf->reshape_stripes)==0
 			   || test_bit(MD_RECOVERY_INTR, &mddev->recovery));
 		if (atomic_read(&conf->reshape_stripes) != 0)
@@ -6364,7 +6368,7 @@ static sector_t reshape_request(struct mddev *mddev, sector_t sector_nr, int *sk
 		spin_lock_irq(&conf->device_lock);
 		conf->reshape_safe = mddev->reshape_position;
 		spin_unlock_irq(&conf->device_lock);
-		wake_up(&conf->wait_for_overlap);
+		wake_up(&conf->wait_for_reshape);
 		sysfs_notify_dirent_safe(mddev->sysfs_completed);
 	}
 
@@ -6447,7 +6451,7 @@ finish:
 	    (sector_nr - mddev->curr_resync_completed) * 2
 	    >= mddev->resync_max - mddev->curr_resync_completed) {
 		/* Cannot proceed until we've updated the superblock... */
-		wait_event(conf->wait_for_overlap,
+		wait_event(conf->wait_for_reshape,
 			   atomic_read(&conf->reshape_stripes) == 0
 			   || test_bit(MD_RECOVERY_INTR, &mddev->recovery));
 		if (atomic_read(&conf->reshape_stripes) != 0)
@@ -6473,7 +6477,7 @@ finish:
 		spin_lock_irq(&conf->device_lock);
 		conf->reshape_safe = mddev->reshape_position;
 		spin_unlock_irq(&conf->device_lock);
-		wake_up(&conf->wait_for_overlap);
+		wake_up(&conf->wait_for_reshape);
 		sysfs_notify_dirent_safe(mddev->sysfs_completed);
 	}
 ret:
@@ -6486,7 +6490,7 @@ static inline sector_t raid5_sync_request(struct mddev *mddev, sector_t sector_n
 	struct r5conf *conf = mddev->private;
 	struct stripe_head *sh;
 	sector_t sync_blocks;
-	int still_degraded = 0;
+	bool still_degraded = false;
 	int i;
 
 	if (sector_nr >= max_sector) {
@@ -6498,17 +6502,17 @@ static inline sector_t raid5_sync_request(struct mddev *mddev, sector_t sector_n
 		}
 
 		if (mddev->curr_resync < max_sector) /* aborted */
-			md_bitmap_end_sync(mddev->bitmap, mddev->curr_resync,
-					   &sync_blocks, 1);
+			mddev->bitmap_ops->end_sync(mddev, mddev->curr_resync,
+						    &sync_blocks);
 		else /* completed sync */
 			conf->fullsync = 0;
-		md_bitmap_close_sync(mddev->bitmap);
+		mddev->bitmap_ops->close_sync(mddev);
 
 		return 0;
 	}
 
 	/* Allow raid5_quiesce to complete */
-	wait_event(conf->wait_for_overlap, conf->quiesce != 2);
+	wait_event(conf->wait_for_reshape, conf->quiesce != 2);
 
 	if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery))
 		return reshape_request(mddev, sector_nr, skipped);
@@ -6531,7 +6535,8 @@ static inline sector_t raid5_sync_request(struct mddev *mddev, sector_t sector_n
 	}
 	if (!test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery) &&
 	    !conf->fullsync &&
-	    !md_bitmap_start_sync(mddev->bitmap, sector_nr, &sync_blocks, 1) &&
+	    !mddev->bitmap_ops->start_sync(mddev, sector_nr, &sync_blocks,
+					   true) &&
 	    sync_blocks >= RAID5_STRIPE_SECTORS(conf)) {
 		/* we can skip this block, and probably more */
 		do_div(sync_blocks, RAID5_STRIPE_SECTORS(conf));
@@ -6540,7 +6545,7 @@ static inline sector_t raid5_sync_request(struct mddev *mddev, sector_t sector_n
 		return sync_blocks * RAID5_STRIPE_SECTORS(conf);
 	}
 
-	md_bitmap_cond_end_sync(mddev->bitmap, sector_nr, false);
+	mddev->bitmap_ops->cond_end_sync(mddev, sector_nr, false);
 
 	sh = raid5_get_active_stripe(conf, NULL, sector_nr,
 				     R5_GAS_NOBLOCK);
@@ -6559,10 +6564,11 @@ static inline sector_t raid5_sync_request(struct mddev *mddev, sector_t sector_n
 		struct md_rdev *rdev = conf->disks[i].rdev;
 
 		if (rdev == NULL || test_bit(Faulty, &rdev->flags))
-			still_degraded = 1;
+			still_degraded = true;
 	}
 
-	md_bitmap_start_sync(mddev->bitmap, sector_nr, &sync_blocks, still_degraded);
+	mddev->bitmap_ops->start_sync(mddev, sector_nr, &sync_blocks,
+				      still_degraded);
 
 	set_bit(STRIPE_SYNC_REQUESTED, &sh->state);
 	set_bit(STRIPE_HANDLE, &sh->state);
@@ -6767,7 +6773,7 @@ static void raid5d(struct md_thread *thread)
 			/* Now is a good time to flush some bitmap updates */
 			conf->seq_flush++;
 			spin_unlock_irq(&conf->device_lock);
-			md_bitmap_unplug(mddev->bitmap);
+			mddev->bitmap_ops->unplug(mddev, true);
 			spin_lock_irq(&conf->device_lock);
 			conf->seq_write = conf->seq_flush;
 			activate_bit_delay(conf, conf->temp_inactive_list);
@@ -7492,7 +7498,7 @@ static struct r5conf *setup_conf(struct mddev *mddev)
 
 	init_waitqueue_head(&conf->wait_for_quiescent);
 	init_waitqueue_head(&conf->wait_for_stripe);
-	init_waitqueue_head(&conf->wait_for_overlap);
+	init_waitqueue_head(&conf->wait_for_reshape);
 	INIT_LIST_HEAD(&conf->handle_list);
 	INIT_LIST_HEAD(&conf->loprio_list);
 	INIT_LIST_HEAD(&conf->hold_list);
@@ -8312,6 +8318,7 @@ static int raid5_resize(struct mddev *mddev, sector_t sectors)
 	 */
 	sector_t newsize;
 	struct r5conf *conf = mddev->private;
+	int ret;
 
 	if (raid5_has_log(conf) || raid5_has_ppl(conf))
 		return -EINVAL;
@@ -8320,11 +8327,11 @@ static int raid5_resize(struct mddev *mddev, sector_t sectors)
 	if (mddev->external_size &&
 	    mddev->array_sectors > newsize)
 		return -EINVAL;
-	if (mddev->bitmap) {
-		int ret = md_bitmap_resize(mddev->bitmap, sectors, 0, 0);
-		if (ret)
-			return ret;
-	}
+
+	ret = mddev->bitmap_ops->resize(mddev, sectors, 0, false);
+	if (ret)
+		return ret;
+
 	md_set_array_sectors(mddev, newsize);
 	if (sectors > mddev->dev_sectors &&
 	    mddev->recovery_cp > mddev->dev_sectors) {
@@ -8550,7 +8557,7 @@ static void end_reshape(struct r5conf *conf)
 			    !test_bit(In_sync, &rdev->flags))
 				rdev->recovery_offset = MaxSector;
 		spin_unlock_irq(&conf->device_lock);
-		wake_up(&conf->wait_for_overlap);
+		wake_up(&conf->wait_for_reshape);
 
 		mddev_update_io_opt(conf->mddev,
 			conf->raid_disks - conf->max_degraded);
@@ -8614,13 +8621,13 @@ static void raid5_quiesce(struct mddev *mddev, int quiesce)
 		conf->quiesce = 1;
 		unlock_all_device_hash_locks_irq(conf);
 		/* allow reshape to continue */
-		wake_up(&conf->wait_for_overlap);
+		wake_up(&conf->wait_for_reshape);
 	} else {
 		/* re-enable writes */
 		lock_all_device_hash_locks_irq(conf);
 		conf->quiesce = 0;
 		wake_up(&conf->wait_for_quiescent);
-		wake_up(&conf->wait_for_overlap);
+		wake_up(&conf->wait_for_reshape);
 		unlock_all_device_hash_locks_irq(conf);
 	}
 	log_quiesce(conf, quiesce);
@@ -8939,7 +8946,7 @@ static void raid5_prepare_suspend(struct mddev *mddev)
 {
 	struct r5conf *conf = mddev->private;
 
-	wake_up(&conf->wait_for_overlap);
+	wake_up(&conf->wait_for_reshape);
 }
 
 static struct md_personality raid6_personality =
diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
index 9b5a7dc3f2a0..896ecfc4afa6 100644
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h
@@ -668,7 +668,7 @@ struct r5conf {
 	struct llist_head	released_stripes;
 	wait_queue_head_t	wait_for_quiescent;
 	wait_queue_head_t	wait_for_stripe;
-	wait_queue_head_t	wait_for_overlap;
+	wait_queue_head_t	wait_for_reshape;
 	unsigned long		cache_state;
 	struct shrinker		*shrinker;
 	int			pool_size; /* number of disks in stripeheads in pool */