Merge tag 'i3c/for-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/i3c/linuxgrafted

Pull I3C updates from Alexandre Belloni:
 "A new driver this cycle, for the AMD AXI I3C controller.

  There are also new features such as IBI wakeup support, SETAASA device
  discovery and ACPI support for the the DAA methods, meaning we can now
  communicate with the SPD devices on DDR5 modules.

  New driver:
   - AMD AXI I3C master controller

  Subsystem:
   - I3C Common Command Code (CCC) handling improvements, especially
     around GET CCCs
   - SETAASA device discovery support
   - ACPI support for all existing DAA methods like SETDASA, SETNEWDA as
     well as I2C devices on I3C bus
   - IBI-based wakeup support

  Drivers:
   - dw: SETAASA support
   - mipi-i3c-hci: advertise IBI wakeup capability, AMD_PT I3C
     controller support, PIO queue management support for HCI v1.2
   - renesas: improve suspend to RAM support, add runtime PM support"

* tag 'i3c/for-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/i3c/linux: (70 commits)
  i3c: dw: reduce do_daa time if there's no client
  i3c: mipi-i3c-hci: Add support for AMD_PT I3C controller
  i3c: mipi-i3c-hci: Add PIO queue management support for HCI v1.2
  i3c: mipi-i3c-hci: Fix missing STAT_IBI_STATUS_THLD in PIO mode
  i3c: dw: rename "pclk" to "apb" to match dt-binding
  i3c: dw: make struct dw_i3c_cmd smaller
  i3c: dw: use COMMAND_PORT_TRANSFER_ARG instead of hardcoding
  i3c: renesas: Don't register devices when ENTDAA times out
  i3c: master: dw-i3c-master: fix OD timing for first broadcast
  i3c: mipi-i3c-hci: Advertise IBI wakeup capability
  i3c: mipi-i3c-hci: Factor out i3c_hci_sysdev()
  i3c: mipi-i3c-hci-pci: Propagate I3C wakeup requirements to PCI
  i3c: master: Reject IBI requests from non-IBI-capable devices
  i3c: master: Add helper to query bus wakeup requirements
  i3c: master: Report wakeup events for IBIs
  i3c: master: Support IBI-based wakeup capability
  i3c: master: Fix potential UAF in i3c_device_match()
  i3c: master: Fix potential UAF in i3c_device_uevent()
  i3c: Make dev->desc locking assumptions explicit
  i3c: master: Fix use-after-free of master->this
  ...

1 files changed, 2421 insertions, 0 deletions

diff --git a/drivers/md/md-llbitmap.c b/drivers/md/md-llbitmap.c
new file mode 100644
index 000000000..e1a783ee2
--- /dev/null
+++ b/drivers/md/md-llbitmap.c
@@ -0,0 +1,2421 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <linux/blkdev.h>
+#include <linux/module.h>
+#include <linux/errno.h>
+#include <linux/slab.h>
+#include <linux/init.h>
+#include <linux/timer.h>
+#include <linux/sched.h>
+#include <linux/list.h>
+#include <linux/file.h>
+#include <linux/math64.h>
+#include <linux/seq_file.h>
+#include <trace/events/block.h>
+
+#include "md.h"
+#include "md-bitmap.h"
+
+/*
+ * #### Background
+ *
+ * Redundant data is used to enhance data fault tolerance, and the storage
+ * methods for redundant data vary depending on the RAID levels. And it's
+ * important to maintain the consistency of redundant data.
+ *
+ * Bitmap is used to record which data blocks have been synchronized and which
+ * ones need to be resynchronized or recovered. Each bit in the bitmap
+ * represents a segment of data in the array. When a bit is set, it indicates
+ * that the multiple redundant copies of that data segment may not be
+ * consistent. Data synchronization can be performed based on the bitmap after
+ * power failure or readding a disk. If there is no bitmap, a full disk
+ * synchronization is required.
+ *
+ * #### Key Features
+ *
+ *  - IO fastpath is lockless, if user issues lots of write IO to the same
+ *  bitmap bit in a short time, only the first write has additional overhead
+ *  to update bitmap bit, no additional overhead for the following writes;
+ *  - support only resync or recover written data, means in the case creating
+ *  new array or replacing with a new disk, there is no need to do a full disk
+ *  resync/recovery;
+ *
+ * #### Key Concept
+ *
+ * ##### State Machine
+ *
+ * Each bit is one byte, contain 6 different states, see llbitmap_state. And
+ * there are total 8 different actions, see llbitmap_action, can change state:
+ *
+ * llbitmap state machine: transitions between states
+ *
+ * |           | Startwrite | Startsync | Endsync | Abortsync|
+ * | --------- | ---------- | --------- | ------- | -------  |
+ * | Unwritten | Dirty      | x         | x       | x        |
+ * | Clean     | Dirty      | x         | x       | x        |
+ * | Dirty     | x          | x         | x       | x        |
+ * | NeedSync  | x          | Syncing   | x       | x        |
+ * | Syncing   | x          | Syncing   | Dirty   | NeedSync |
+ *
+ * |           | Reload   | Daemon | Discard   | Stale     |
+ * | --------- | -------- | ------ | --------- | --------- |
+ * | Unwritten | x        | x      | x         | x         |
+ * | Clean     | x        | x      | Unwritten | NeedSync  |
+ * | Dirty     | NeedSync | Clean  | Unwritten | NeedSync  |
+ * | NeedSync  | x        | x      | Unwritten | x         |
+ * | Syncing   | NeedSync | x      | Unwritten | NeedSync  |
+ *
+ * Typical scenarios:
+ *
+ * 1) Create new array
+ * All bits will be set to Unwritten by default, if --assume-clean is set,
+ * all bits will be set to Clean instead.
+ *
+ * 2) write data, raid1/raid10 have full copy of data, while raid456 doesn't and
+ * rely on xor data
+ *
+ * 2.1) write new data to raid1/raid10:
+ * Unwritten --StartWrite--> Dirty
+ *
+ * 2.2) write new data to raid456:
+ * Unwritten --StartWrite--> NeedSync
+ *
+ * Because the initial recover for raid456 is skipped, the xor data is not built
+ * yet, the bit must be set to NeedSync first and after lazy initial recover is
+ * finished, the bit will finally set to Dirty(see 5.1 and 5.4);
+ *
+ * 2.3) cover write
+ * Clean --StartWrite--> Dirty
+ *
+ * 3) daemon, if the array is not degraded:
+ * Dirty --Daemon--> Clean
+ *
+ * 4) discard
+ * {Clean, Dirty, NeedSync, Syncing} --Discard--> Unwritten
+ *
+ * 5) resync and recover
+ *
+ * 5.1) common process
+ * NeedSync --Startsync--> Syncing --Endsync--> Dirty --Daemon--> Clean
+ *
+ * 5.2) resync after power failure
+ * Dirty --Reload--> NeedSync
+ *
+ * 5.3) recover while replacing with a new disk
+ * By default, the old bitmap framework will recover all data, and llbitmap
+ * implements this by a new helper, see llbitmap_skip_sync_blocks:
+ *
+ * skip recover for bits other than dirty or clean;
+ *
+ * 5.4) lazy initial recover for raid5:
+ * By default, the old bitmap framework will only allow new recover when there
+ * are spares(new disk), a new recovery flag MD_RECOVERY_LAZY_RECOVER is added
+ * to perform raid456 lazy recover for set bits(from 2.2).
+ *
+ * 6. special handling for degraded array:
+ *
+ * - Dirty bits will never be cleared, daemon will just do nothing, so that if
+ *   a disk is readded, Clean bits can be skipped with recovery;
+ * - Dirty bits will convert to Syncing from start write, to do data recovery
+ *   for new added disks;
+ * - New write will convert bits to NeedSync directly;
+ *
+ * ##### Bitmap IO
+ *
+ * ##### Chunksize
+ *
+ * The default bitmap size is 128k, incluing 1k bitmap super block, and
+ * the default size of segment of data in the array each bit(chunksize) is 64k,
+ * and chunksize will adjust to twice the old size each time if the total number
+ * bits is not less than 127k.(see llbitmap_init)
+ *
+ * ##### READ
+ *
+ * While creating bitmap, all pages will be allocated and read for llbitmap,
+ * there won't be read afterwards
+ *
+ * ##### WRITE
+ *
+ * WRITE IO is divided into logical_block_size of the array, the dirty state
+ * of each block is tracked independently, for example:
+ *
+ * each page is 4k, contain 8 blocks; each block is 512 bytes contain 512 bit;
+ *
+ * | page0 | page1 | ... | page 31 |
+ * |       |
+ * |        \-----------------------\
+ * |                                |
+ * | block0 | block1 | ... | block 8|
+ * |        |
+ * |         \-----------------\
+ * |                            |
+ * | bit0 | bit1 | ... | bit511 |
+ *
+ * From IO path, if one bit is changed to Dirty or NeedSync, the corresponding
+ * subpage will be marked dirty, such block must write first before the IO is
+ * issued. This behaviour will affect IO performance, to reduce the impact, if
+ * multiple bits are changed in the same block in a short time, all bits in this
+ * block will be changed to Dirty/NeedSync, so that there won't be any overhead
+ * until daemon clears dirty bits.
+ *
+ * ##### Dirty Bits synchronization
+ *
+ * IO fast path will set bits to dirty, and those dirty bits will be cleared
+ * by daemon after IO is done. llbitmap_page_ctl is used to synchronize between
+ * IO path and daemon;
+ *
+ * IO path:
+ *  1) try to grab a reference, if succeed, set expire time after 5s and return;
+ *  2) if failed to grab a reference, wait for daemon to finish clearing dirty
+ *  bits;
+ *
+ * Daemon (Daemon will be woken up every daemon_sleep seconds):
+ * For each page:
+ *  1) check if page expired, if not skip this page; for expired page:
+ *  2) suspend the page and wait for inflight write IO to be done;
+ *  3) change dirty page to clean;
+ *  4) resume the page;
+ */
+
+#define BITMAP_DATA_OFFSET 1024
+
+/* 64k is the max IO size of sync IO for raid1/raid10 */
+#define MIN_CHUNK_SIZE (64 * 2)
+
+/* By default, daemon will be woken up every 30s */
+#define DEFAULT_DAEMON_SLEEP 30
+
+/*
+ * Dirtied bits that have not been accessed for more than 5s will be cleared
+ * by daemon.
+ */
+#define DEFAULT_BARRIER_IDLE 5
+
+enum llbitmap_state {
+	/* No valid data, init state after assemble the array */
+	BitUnwritten = 0,
+	/* data is consistent */
+	BitClean,
+	/* data will be consistent after IO is done, set directly for writes */
+	BitDirty,
+	/*
+	 * data need to be resynchronized:
+	 * 1) set directly for writes if array is degraded, prevent full disk
+	 * synchronization after readding a disk;
+	 * 2) reassemble the array after power failure, and dirty bits are
+	 * found after reloading the bitmap;
+	 * 3) set for first write for raid5, to build initial xor data lazily
+	 */
+	BitNeedSync,
+	/* data is synchronizing */
+	BitSyncing,
+	/*
+	 * Proactive sync requested for unwritten region (raid456 only).
+	 * Triggered via sysfs when user wants to pre-build XOR parity
+	 * for regions that have never been written.
+	 */
+	BitNeedSyncUnwritten,
+	/* Proactive sync in progress for unwritten region */
+	BitSyncingUnwritten,
+	/*
+	 * XOR parity has been pre-built for a region that has never had
+	 * user data written. When user writes to this region, it transitions
+	 * to BitDirty.
+	 */
+	BitCleanUnwritten,
+	BitStateCount,
+	BitNone = 0xff,
+};
+
+enum llbitmap_action {
+	/* User write new data, this is the only action from IO fast path */
+	BitmapActionStartwrite = 0,
+	/* Start recovery */
+	BitmapActionStartsync,
+	/* Finish recovery */
+	BitmapActionEndsync,
+	/* Failed recovery */
+	BitmapActionAbortsync,
+	/* Reassemble the array */
+	BitmapActionReload,
+	/* Daemon thread is trying to clear dirty bits */
+	BitmapActionDaemon,
+	/* Data is deleted */
+	BitmapActionDiscard,
+	/*
+	 * Bitmap is stale, mark all bits in addition to BitUnwritten to
+	 * BitNeedSync.
+	 */
+	BitmapActionStale,
+	/*
+	 * Proactive sync trigger for raid456 - builds XOR parity for
+	 * Unwritten regions without requiring user data write first.
+	 */
+	BitmapActionProactiveSync,
+	BitmapActionClearUnwritten,
+	BitmapActionCount,
+	/* Init state is BitUnwritten */
+	BitmapActionInit,
+};
+
+enum llbitmap_page_state {
+	LLPageFlush = 0,
+	LLPageDirty,
+};
+
+struct llbitmap_page_ctl {
+	char *state;
+	struct page *page;
+	unsigned long expire;
+	unsigned long flags;
+	wait_queue_head_t wait;
+	struct percpu_ref active;
+	/* Per block size dirty state, maximum 64k page / 1 sector = 128 */
+	unsigned long dirty[];
+};
+
+struct llbitmap {
+	struct mddev *mddev;
+	struct llbitmap_page_ctl **pctl;
+
+	unsigned int nr_pages;
+	unsigned int io_size;
+	unsigned int blocks_per_page;
+
+	/* shift of one chunk */
+	unsigned long chunkshift;
+	/* size of one chunk in sector */
+	unsigned long chunksize;
+	/* total number of chunks */
+	unsigned long chunks;
+	/* total number of sectors tracked by current bitmap geometry */
+	sector_t sync_size;
+	unsigned long reshape_chunksize;
+	unsigned long reshape_chunks;
+	sector_t reshape_sync_size;
+	unsigned long last_end_sync;
+	/*
+	 * time in seconds that dirty bits will be cleared if the page is not
+	 * accessed.
+	 */
+	unsigned long barrier_idle;
+	/* fires on first BitDirty state */
+	struct timer_list pending_timer;
+	struct work_struct daemon_work;
+	/*
+	 * Serialize reshape checkpoint remapping against normal I/O bitmap
+	 * updates without blocking concurrent I/O updates on each other.
+	 */
+	rwlock_t reshape_lock;
+
+	unsigned long flags;
+	__u64	events_cleared;
+
+	/* for slow disks */
+	atomic_t behind_writes;
+	wait_queue_head_t behind_wait;
+};
+
+struct llbitmap_unplug_work {
+	struct work_struct work;
+	struct llbitmap *llbitmap;
+	struct completion *done;
+};
+
+static struct workqueue_struct *md_llbitmap_io_wq;
+static struct workqueue_struct *md_llbitmap_unplug_wq;
+
+static char state_machine[BitStateCount][BitmapActionCount] = {
+	[BitUnwritten] = {
+		[BitmapActionStartwrite]	= BitDirty,
+		[BitmapActionStartsync]		= BitNone,
+		[BitmapActionEndsync]		= BitNone,
+		[BitmapActionAbortsync]		= BitNone,
+		[BitmapActionReload]		= BitNone,
+		[BitmapActionDaemon]		= BitNone,
+		[BitmapActionDiscard]		= BitNone,
+		[BitmapActionStale]		= BitNone,
+		[BitmapActionProactiveSync]	= BitNeedSyncUnwritten,
+		[BitmapActionClearUnwritten]	= BitNone,
+	},
+	[BitClean] = {
+		[BitmapActionStartwrite]	= BitDirty,
+		[BitmapActionStartsync]		= BitNone,
+		[BitmapActionEndsync]		= BitNone,
+		[BitmapActionAbortsync]		= BitNone,
+		[BitmapActionReload]		= BitNone,
+		[BitmapActionDaemon]		= BitNone,
+		[BitmapActionDiscard]		= BitUnwritten,
+		[BitmapActionStale]		= BitNeedSync,
+		[BitmapActionProactiveSync]	= BitNone,
+		[BitmapActionClearUnwritten]	= BitNone,
+	},
+	[BitDirty] = {
+		[BitmapActionStartwrite]	= BitNone,
+		[BitmapActionStartsync]		= BitNone,
+		[BitmapActionEndsync]		= BitNone,
+		[BitmapActionAbortsync]		= BitNone,
+		[BitmapActionReload]		= BitNeedSync,
+		[BitmapActionDaemon]		= BitClean,
+		[BitmapActionDiscard]		= BitUnwritten,
+		[BitmapActionStale]		= BitNeedSync,
+		[BitmapActionProactiveSync]	= BitNone,
+		[BitmapActionClearUnwritten]	= BitNone,
+	},
+	[BitNeedSync] = {
+		[BitmapActionStartwrite]	= BitNone,
+		[BitmapActionStartsync]		= BitSyncing,
+		[BitmapActionEndsync]		= BitNone,
+		[BitmapActionAbortsync]		= BitNone,
+		[BitmapActionReload]		= BitNone,
+		[BitmapActionDaemon]		= BitNone,
+		[BitmapActionDiscard]		= BitUnwritten,
+		[BitmapActionStale]		= BitNone,
+		[BitmapActionProactiveSync]	= BitNone,
+		[BitmapActionClearUnwritten]	= BitNone,
+	},
+	[BitSyncing] = {
+		[BitmapActionStartwrite]	= BitNone,
+		[BitmapActionStartsync]		= BitSyncing,
+		[BitmapActionEndsync]		= BitDirty,
+		[BitmapActionAbortsync]		= BitNeedSync,
+		[BitmapActionReload]		= BitNeedSync,
+		[BitmapActionDaemon]		= BitNone,
+		[BitmapActionDiscard]		= BitUnwritten,
+		[BitmapActionStale]		= BitNeedSync,
+		[BitmapActionProactiveSync]	= BitNone,
+		[BitmapActionClearUnwritten]	= BitNone,
+	},
+	[BitNeedSyncUnwritten] = {
+		[BitmapActionStartwrite]	= BitNeedSync,
+		[BitmapActionStartsync]		= BitSyncingUnwritten,
+		[BitmapActionEndsync]		= BitNone,
+		[BitmapActionAbortsync]		= BitUnwritten,
+		[BitmapActionReload]		= BitUnwritten,
+		[BitmapActionDaemon]		= BitNone,
+		[BitmapActionDiscard]		= BitUnwritten,
+		[BitmapActionStale]		= BitUnwritten,
+		[BitmapActionProactiveSync]	= BitNone,
+		[BitmapActionClearUnwritten]	= BitUnwritten,
+	},
+	[BitSyncingUnwritten] = {
+		[BitmapActionStartwrite]	= BitSyncing,
+		[BitmapActionStartsync]		= BitSyncingUnwritten,
+		[BitmapActionEndsync]		= BitCleanUnwritten,
+		[BitmapActionAbortsync]		= BitUnwritten,
+		[BitmapActionReload]		= BitUnwritten,
+		[BitmapActionDaemon]		= BitNone,
+		[BitmapActionDiscard]		= BitUnwritten,
+		[BitmapActionStale]		= BitUnwritten,
+		[BitmapActionProactiveSync]	= BitNone,
+		[BitmapActionClearUnwritten]	= BitUnwritten,
+	},
+	[BitCleanUnwritten] = {
+		[BitmapActionStartwrite]	= BitDirty,
+		[BitmapActionStartsync]		= BitNone,
+		[BitmapActionEndsync]		= BitNone,
+		[BitmapActionAbortsync]		= BitNone,
+		[BitmapActionReload]		= BitNone,
+		[BitmapActionDaemon]		= BitNone,
+		[BitmapActionDiscard]		= BitUnwritten,
+		[BitmapActionStale]		= BitUnwritten,
+		[BitmapActionProactiveSync]	= BitNone,
+		[BitmapActionClearUnwritten]	= BitUnwritten,
+	},
+};
+
+static void __llbitmap_flush(struct mddev *mddev);
+static void llbitmap_flush(struct mddev *mddev);
+static void llbitmap_update_sb(void *data);
+
+static void llbitmap_calculate_chunks(struct mddev *mddev, sector_t blocks,
+				      unsigned long *chunksize,
+				      unsigned long *chunks)
+{
+	*chunks = DIV_ROUND_UP_SECTOR_T(blocks, *chunksize);
+	while (*chunks > mddev->bitmap_info.space << SECTOR_SHIFT) {
+		*chunksize = *chunksize << 1;
+		*chunks = DIV_ROUND_UP_SECTOR_T(blocks, *chunksize);
+	}
+}
+
+static sector_t llbitmap_personality_sync_size(struct llbitmap *llbitmap,
+					       bool previous)
+{
+	struct mddev *mddev = llbitmap->mddev;
+
+	if (READ_ONCE(mddev->reshape_position) == MaxSector ||
+	    !mddev->private || !mddev->pers ||
+	    !mddev->pers->bitmap_sync_size)
+		return llbitmap->sync_size;
+	return mddev->pers->bitmap_sync_size(mddev, previous);
+}
+
+static sector_t llbitmap_logical_size(struct llbitmap *llbitmap, bool previous)
+{
+	struct mddev *mddev = llbitmap->mddev;
+
+	if (!mddev->private || !mddev->pers ||
+	    !mddev->pers->bitmap_array_sectors)
+		return llbitmap_personality_sync_size(llbitmap, previous);
+	return mddev->pers->bitmap_array_sectors(mddev, previous);
+}
+
+static void llbitmap_refresh_reshape(struct llbitmap *llbitmap)
+{
+	unsigned long old_chunks = DIV_ROUND_UP_SECTOR_T(llbitmap->sync_size,
+						 llbitmap->chunksize);
+	sector_t blocks = llbitmap_personality_sync_size(llbitmap, false);
+	unsigned long chunksize = llbitmap->chunksize;
+	unsigned long chunks = DIV_ROUND_UP_SECTOR_T(blocks, chunksize);
+
+	llbitmap->reshape_sync_size = blocks;
+	llbitmap->reshape_chunksize = chunksize;
+	llbitmap->reshape_chunks = chunks;
+	llbitmap_calculate_chunks(llbitmap->mddev, blocks,
+				  &llbitmap->reshape_chunksize,
+				  &llbitmap->reshape_chunks);
+	llbitmap->chunks = max(old_chunks, llbitmap->reshape_chunks);
+}
+
+static void llbitmap_map_layout(struct llbitmap *llbitmap, sector_t *offset,
+				unsigned long *sectors, bool previous)
+{
+	sector_t limit = llbitmap_logical_size(llbitmap, previous);
+	sector_t start = *offset;
+	sector_t end = start + *sectors;
+
+	if (start >= limit) {
+		*sectors = 0;
+		return;
+	}
+	if (end > limit)
+		end = limit;
+
+	*offset = start;
+	*sectors = end - start;
+	if (!*sectors)
+		return;
+
+	if (llbitmap->mddev->pers->bitmap_sector_map)
+		llbitmap->mddev->pers->bitmap_sector_map(llbitmap->mddev, offset,
+							 sectors, previous);
+	else if (!previous && llbitmap->mddev->pers->bitmap_sector)
+		llbitmap->mddev->pers->bitmap_sector(llbitmap->mddev, offset,
+							 sectors);
+
+	limit = llbitmap_personality_sync_size(llbitmap, previous);
+	start = *offset;
+	end = start + *sectors;
+	if (start >= limit)
+		*sectors = 0;
+	else if (end > limit)
+		*sectors = limit - start;
+}
+
+static void llbitmap_encode_range(struct llbitmap *llbitmap, sector_t *offset,
+				  unsigned long *sectors, bool previous)
+{
+	unsigned long chunksize = previous ? llbitmap->chunksize :
+				      llbitmap->reshape_chunksize;
+	u64 start;
+	u64 end;
+
+	if (!*sectors) {
+		*offset = 0;
+		return;
+	}
+
+	start = div64_u64(*offset, chunksize);
+	end = div64_u64(*offset + *sectors - 1, chunksize);
+	*offset = (sector_t)start << llbitmap->chunkshift;
+	*sectors = (end - start + 1) << llbitmap->chunkshift;
+}
+
+static void llbitmap_encode_discard_range(struct llbitmap *llbitmap,
+					  sector_t *offset,
+					  unsigned long *sectors,
+					  bool previous)
+{
+	unsigned long chunksize = previous ? llbitmap->chunksize :
+					      llbitmap->reshape_chunksize;
+	sector_t end = *offset + *sectors;
+	u64 start;
+	u64 last;
+
+	if (!*sectors) {
+		*offset = 0;
+		return;
+	}
+
+	start = DIV_ROUND_UP_SECTOR_T(*offset, chunksize);
+	last = div64_u64(end, chunksize);
+	if (start >= last) {
+		*offset = 0;
+		*sectors = 0;
+		return;
+	}
+
+	*offset = (sector_t)start << llbitmap->chunkshift;
+	*sectors = (last - start) << llbitmap->chunkshift;
+}
+
+static enum llbitmap_state llbitmap_read(struct llbitmap *llbitmap, loff_t pos)
+{
+	unsigned int idx;
+	unsigned int offset;
+
+	pos += BITMAP_DATA_OFFSET;
+	idx = pos >> PAGE_SHIFT;
+	offset = offset_in_page(pos);
+
+	return llbitmap->pctl[idx]->state[offset];
+}
+
+/* set all the bits in the subpage as dirty */
+static void llbitmap_infect_dirty_bits(struct llbitmap *llbitmap,
+				       struct llbitmap_page_ctl *pctl,
+				       unsigned int block)
+{
+	bool level_456 = raid_is_456(llbitmap->mddev);
+	unsigned int io_size = llbitmap->io_size;
+	int pos;
+
+	for (pos = block * io_size; pos < (block + 1) * io_size; pos++) {
+		switch (pctl->state[pos]) {
+		case BitUnwritten:
+			pctl->state[pos] = level_456 ? BitNeedSync : BitDirty;
+			break;
+		case BitClean:
+		case BitCleanUnwritten:
+			pctl->state[pos] = BitDirty;
+			break;
+		}
+	}
+}
+
+static void llbitmap_set_page_dirty(struct llbitmap *llbitmap, int idx,
+				    int offset, bool infect)
+{
+	struct llbitmap_page_ctl *pctl = llbitmap->pctl[idx];
+	unsigned int io_size = llbitmap->io_size;
+	int block = offset / io_size;
+	int pos;
+
+	if (!test_bit(LLPageDirty, &pctl->flags))
+		set_bit(LLPageDirty, &pctl->flags);
+
+	/*
+	 * For degraded array, dirty bits will never be cleared, and we must
+	 * resync all the dirty bits, hence skip infect new dirty bits to
+	 * prevent resync unnecessary data.
+	 */
+	if (llbitmap->mddev->degraded || !infect) {
+		set_bit(block, pctl->dirty);
+		return;
+	}
+
+	/*
+	 * The subpage usually contains a total of 512 bits. If any single bit
+	 * within the subpage is marked as dirty, the entire sector will be
+	 * written. To avoid impacting write performance, when multiple bits
+	 * within the same sector are modified within llbitmap->barrier_idle,
+	 * all bits in the sector will be collectively marked as dirty at once.
+	 */
+	if (test_and_set_bit(block, pctl->dirty)) {
+		llbitmap_infect_dirty_bits(llbitmap, pctl, block);
+		return;
+	}
+
+	for (pos = block * io_size; pos < (block + 1) * io_size; pos++) {
+		if (pos == offset)
+			continue;
+		if (pctl->state[pos] == BitDirty ||
+		    pctl->state[pos] == BitNeedSync) {
+			llbitmap_infect_dirty_bits(llbitmap, pctl, block);
+			return;
+		}
+	}
+}
+
+static void llbitmap_write(struct llbitmap *llbitmap, enum llbitmap_state state,
+			   loff_t pos)
+{
+	unsigned int idx;
+	unsigned int bit;
+
+	pos += BITMAP_DATA_OFFSET;
+	idx = pos >> PAGE_SHIFT;
+	bit = offset_in_page(pos);
+
+	llbitmap->pctl[idx]->state[bit] = state;
+	if (state == BitDirty || state == BitNeedSync)
+		llbitmap_set_page_dirty(llbitmap, idx, bit, true);
+	else if (state == BitNeedSyncUnwritten)
+		llbitmap_set_page_dirty(llbitmap, idx, bit, false);
+}
+
+static unsigned int llbitmap_used_pages(struct llbitmap *llbitmap,
+					unsigned long chunks)
+{
+	return DIV_ROUND_UP(chunks + BITMAP_DATA_OFFSET, PAGE_SIZE);
+}
+
+static struct page *llbitmap_read_page(struct llbitmap *llbitmap, int idx)
+{
+	struct mddev *mddev = llbitmap->mddev;
+	struct page *page = NULL;
+	struct md_rdev *rdev;
+
+	if (llbitmap->pctl && idx < llbitmap->nr_pages && llbitmap->pctl[idx])
+		page = llbitmap->pctl[idx]->page;
+	if (page)
+		return page;
+
+	page = alloc_page(GFP_NOIO | __GFP_ZERO);
+	if (!page)
+		return ERR_PTR(-ENOMEM);
+	if (idx >= llbitmap_used_pages(llbitmap, llbitmap->chunks))
+		return page;
+
+	rdev_for_each(rdev, mddev) {
+		sector_t sector;
+
+		if (rdev->raid_disk < 0 || test_bit(Faulty, &rdev->flags) ||
+		    !test_bit(In_sync, &rdev->flags))
+			continue;
+
+		sector = mddev->bitmap_info.offset +
+			 (idx << PAGE_SECTORS_SHIFT);
+
+		if (sync_page_io(rdev, sector, PAGE_SIZE, page, REQ_OP_READ,
+				 true))
+			return page;
+
+		md_error(mddev, rdev);
+	}
+
+	__free_page(page);
+	return ERR_PTR(-EIO);
+}
+
+static void llbitmap_write_page(struct llbitmap *llbitmap, int idx)
+{
+	struct page *page = llbitmap->pctl[idx]->page;
+	struct mddev *mddev = llbitmap->mddev;
+	struct md_rdev *rdev;
+	int block;
+
+	for (block = 0; block < llbitmap->blocks_per_page; block++) {
+		struct llbitmap_page_ctl *pctl = llbitmap->pctl[idx];
+
+		if (!test_and_clear_bit(block, pctl->dirty))
+			continue;
+
+		rdev_for_each(rdev, mddev) {
+			sector_t sector;
+			sector_t bit_sector = llbitmap->io_size >> SECTOR_SHIFT;
+
+			if (rdev->raid_disk < 0 || test_bit(Faulty, &rdev->flags))
+				continue;
+
+			sector = mddev->bitmap_info.offset + rdev->sb_start +
+				 (idx << PAGE_SECTORS_SHIFT) +
+				 block * bit_sector;
+			md_write_metadata(mddev, rdev, sector,
+					  llbitmap->io_size, page,
+					  block * llbitmap->io_size);
+		}
+	}
+}
+
+static void active_release(struct percpu_ref *ref)
+{
+	struct llbitmap_page_ctl *pctl =
+		container_of(ref, struct llbitmap_page_ctl, active);
+
+	wake_up(&pctl->wait);
+}
+
+static void llbitmap_free_pages(struct llbitmap *llbitmap)
+{
+	int i;
+
+	if (!llbitmap->pctl)
+		return;
+
+	for (i = 0; i < llbitmap->nr_pages; i++) {
+		struct llbitmap_page_ctl *pctl = llbitmap->pctl[i];
+
+		if (!pctl)
+			continue;
+		if (pctl->page)
+			__free_page(pctl->page);
+		percpu_ref_exit(&pctl->active);
+		kfree(pctl);
+	}
+
+	kfree(llbitmap->pctl);
+	llbitmap->pctl = NULL;
+}
+
+static struct llbitmap_page_ctl *
+llbitmap_alloc_page_ctl(struct llbitmap *llbitmap, int idx)
+{
+	struct llbitmap_page_ctl *pctl;
+	struct page *page;
+	unsigned int size = struct_size(pctl, dirty, BITS_TO_LONGS(
+						llbitmap->blocks_per_page));
+
+	size = round_up(size, cache_line_size());
+	pctl = kzalloc(size, GFP_NOIO);
+	if (!pctl)
+		return ERR_PTR(-ENOMEM);
+
+	page = llbitmap_read_page(llbitmap, idx);
+
+	if (IS_ERR(page)) {
+		kfree(pctl);
+		return ERR_CAST(page);
+	}
+
+	if (percpu_ref_init(&pctl->active, active_release,
+			    PERCPU_REF_ALLOW_REINIT, GFP_NOIO)) {
+		__free_page(page);
+		kfree(pctl);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	pctl->page = page;
+	pctl->state = page_address(page);
+	init_waitqueue_head(&pctl->wait);
+	return pctl;
+}
+
+static unsigned int llbitmap_reserved_pages(struct llbitmap *llbitmap)
+{
+	return DIV_ROUND_UP(llbitmap->mddev->bitmap_info.space << SECTOR_SHIFT,
+			    PAGE_SIZE);
+}
+
+static int llbitmap_expand_pages(struct llbitmap *llbitmap,
+				 unsigned long chunks)
+{
+	struct llbitmap_page_ctl **pctl;
+	unsigned int old_nr_pages = llbitmap->nr_pages;
+	unsigned int nr_pages = llbitmap_used_pages(llbitmap, chunks);
+	unsigned int i;
+	int ret;
+
+	if (nr_pages <= old_nr_pages)
+		return 0;
+
+	pctl = kcalloc(nr_pages, sizeof(*pctl), GFP_NOIO);
+	if (!pctl)
+		return -ENOMEM;
+
+	if (llbitmap->pctl)
+		memcpy(pctl, llbitmap->pctl,
+		       array_size(old_nr_pages, sizeof(*pctl)));
+
+	for (i = old_nr_pages; i < nr_pages; i++) {
+		pctl[i] = llbitmap_alloc_page_ctl(llbitmap, i);
+		if (IS_ERR(pctl[i]))
+			goto err_alloc_ptr;
+	}
+
+	kfree(llbitmap->pctl);
+	llbitmap->pctl = pctl;
+	llbitmap->nr_pages = nr_pages;
+	return 0;
+
+err_alloc_ptr:
+	ret = PTR_ERR(pctl[i]);
+	while (i-- > old_nr_pages) {
+		__free_page(pctl[i]->page);
+		percpu_ref_exit(&pctl[i]->active);
+		kfree(pctl[i]);
+	}
+	kfree(pctl);
+	return ret;
+}
+
+static int llbitmap_alloc_pages(struct llbitmap *llbitmap)
+{
+	unsigned int used_pages = llbitmap_used_pages(llbitmap, llbitmap->chunks);
+	unsigned int nr_pages = max(used_pages, llbitmap_reserved_pages(llbitmap));
+	int i;
+
+	llbitmap->pctl = kcalloc(nr_pages, sizeof(*llbitmap->pctl), GFP_NOIO);
+	if (!llbitmap->pctl)
+		return -ENOMEM;
+
+	llbitmap->nr_pages = nr_pages;
+
+	for (i = 0; i < nr_pages; i++) {
+		llbitmap->pctl[i] = llbitmap_alloc_page_ctl(llbitmap, i);
+		if (IS_ERR(llbitmap->pctl[i])) {
+			int ret = PTR_ERR(llbitmap->pctl[i]);
+
+			llbitmap->pctl[i] = NULL;
+			llbitmap_free_pages(llbitmap);
+			return ret;
+		}
+	}
+
+	return 0;
+}
+
+/*
+ * Check if all underlying disks support write_zeroes with unmap.
+ */
+static bool llbitmap_all_disks_support_wzeroes_unmap(struct llbitmap *llbitmap)
+{
+	struct mddev *mddev = llbitmap->mddev;
+	struct md_rdev *rdev;
+
+	rdev_for_each(rdev, mddev) {
+		if (rdev->raid_disk < 0 || test_bit(Faulty, &rdev->flags))
+			continue;
+
+		if (bdev_write_zeroes_unmap_sectors(rdev->bdev) == 0)
+			return false;
+	}
+
+	return true;
+}
+
+/*
+ * Issue write_zeroes to all underlying disks to zero their data regions.
+ * This ensures parity consistency for RAID-456 (0 XOR 0 = 0).
+ * Returns true if all disks were successfully zeroed.
+ */
+static bool llbitmap_zero_all_disks(struct llbitmap *llbitmap)
+{
+	struct mddev *mddev = llbitmap->mddev;
+	struct md_rdev *rdev;
+	sector_t dev_sectors = mddev->dev_sectors;
+	int ret;
+
+	rdev_for_each(rdev, mddev) {
+		if (rdev->raid_disk < 0 || test_bit(Faulty, &rdev->flags))
+			continue;
+
+		ret = blkdev_issue_zeroout(rdev->bdev,
+					   rdev->data_offset,
+					   dev_sectors,
+					   GFP_KERNEL, 0);
+		if (ret) {
+			pr_warn("md/llbitmap: failed to zero disk %pg: %d\n",
+				rdev->bdev, ret);
+			return false;
+		}
+	}
+
+	return true;
+}
+
+static void llbitmap_mark_range(struct llbitmap *llbitmap,
+				unsigned long start,
+				unsigned long end,
+				enum llbitmap_state state)
+{
+	while (start <= end) {
+		llbitmap_write(llbitmap, state, start);
+		start++;
+	}
+}
+
+static int llbitmap_prepare_resize(struct llbitmap *llbitmap,
+				   unsigned long old_chunks,
+				   unsigned long new_chunks,
+				   unsigned long cache_chunks)
+{
+	int ret;
+
+	llbitmap_flush(llbitmap->mddev);
+	ret = llbitmap_expand_pages(llbitmap, cache_chunks);
+	if (ret)
+		return ret;
+	if (new_chunks > old_chunks)
+		llbitmap_mark_range(llbitmap, old_chunks, new_chunks - 1,
+				    BitUnwritten);
+	return 0;
+}
+
+static enum llbitmap_state
+llbitmap_rmerge_state(struct llbitmap *llbitmap,
+		      enum llbitmap_state dst,
+		      enum llbitmap_state src)
+{
+	bool level_456 = raid_is_456(llbitmap->mddev);
+
+	if (dst == BitNeedSync || dst == BitSyncing ||
+	    src == BitNeedSync || src == BitSyncing)
+		return BitNeedSync;
+
+	if (dst == BitDirty || src == BitDirty)
+		return BitDirty;
+
+	/*
+	 * Reshape generates valid target parity/data for both already-written
+	 * and not-yet-written regions in the checkpointed range, so a mix of
+	 * clean and unwritten still results in a clean destination bit.
+	 */
+	if (level_456 && ((dst == BitClean && src == BitUnwritten) ||
+			  (src == BitClean && dst == BitUnwritten)))
+		return BitClean;
+	if (dst == BitClean || src == BitClean)
+		return BitClean;
+	return BitUnwritten;
+}
+
+static void llbitmap_init_state(struct llbitmap *llbitmap)
+{
+	struct mddev *mddev = llbitmap->mddev;
+	enum llbitmap_state state = BitUnwritten;
+	unsigned long i;
+
+	if (test_and_clear_bit(BITMAP_CLEAN, &llbitmap->flags)) {
+		state = BitClean;
+	} else if (raid_is_456(mddev) &&
+		   llbitmap_all_disks_support_wzeroes_unmap(llbitmap)) {
+		/*
+		 * All disks support write_zeroes with unmap. Zero all disks
+		 * to ensure parity consistency, then set BitCleanUnwritten
+		 * to skip initial sync.
+		 */
+		if (llbitmap_zero_all_disks(llbitmap))
+			state = BitCleanUnwritten;
+	}
+
+	for (i = 0; i < llbitmap->chunks; i++)
+		llbitmap_write(llbitmap, state, i);
+}
+
+/* The return value is only used from resync, where @start == @end. */
+static enum llbitmap_state llbitmap_state_machine(struct llbitmap *llbitmap,
+						  unsigned long start,
+						  unsigned long end,
+						  enum llbitmap_action action)
+{
+	struct mddev *mddev = llbitmap->mddev;
+	enum llbitmap_state state = BitNone;
+	bool level_456 = raid_is_456(llbitmap->mddev);
+	bool need_resync = false;
+	bool need_recovery = false;
+
+	if (test_bit(BITMAP_WRITE_ERROR, &llbitmap->flags))
+		return BitNone;
+
+	if (action == BitmapActionInit) {
+		llbitmap_init_state(llbitmap);
+		return BitNone;
+	}
+	if (start >= llbitmap->chunks)
+		return BitNone;
+	if (end >= llbitmap->chunks)
+		end = llbitmap->chunks - 1;
+	while (start <= end) {
+		enum llbitmap_state c = llbitmap_read(llbitmap, start);
+
+		if (c < 0 || c >= BitStateCount) {
+			pr_err("%s: invalid bit %lu state %d action %d, forcing resync\n",
+			       __func__, start, c, action);
+			state = BitNeedSync;
+			goto write_bitmap;
+		}
+
+		if (c == BitNeedSync || c == BitNeedSyncUnwritten)
+			need_resync = !mddev->degraded;
+
+		state = state_machine[c][action];
+write_bitmap:
+		if (unlikely(mddev->degraded)) {
+			/* For degraded array, mark new data as need sync. */
+			if (state == BitDirty &&
+			    action == BitmapActionStartwrite)
+				state = BitNeedSync;
+			/*
+			 * For degraded array, resync dirty data as well, noted
+			 * if array is still degraded after resync is done, all
+			 * new data will still be dirty until array is clean.
+			 */
+			else if (c == BitDirty &&
+				action == BitmapActionStartsync)
+				state = BitSyncing;
+		} else if (c == BitUnwritten && state == BitDirty &&
+			   action == BitmapActionStartwrite && level_456) {
+			/* Delay raid456 initial recovery to first write. */
+			state = BitNeedSync;
+		}
+
+		if (state == BitNone) {
+			start++;
+			continue;
+		}
+
+		llbitmap_write(llbitmap, state, start);
+		if (state == BitNeedSync || state == BitNeedSyncUnwritten)
+			need_resync = !mddev->degraded;
+		else if (state == BitDirty &&
+			 !test_bit(BITMAP_SHUTDOWN, &llbitmap->flags) &&
+			 !timer_pending(&llbitmap->pending_timer))
+			mod_timer(&llbitmap->pending_timer,
+				  jiffies + mddev->bitmap_info.daemon_sleep * HZ);
+
+		start++;
+	}
+
+	if (need_resync && level_456)
+		need_recovery = true;
+
+	if (need_recovery) {
+		set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
+		set_bit(MD_RECOVERY_LAZY_RECOVER, &mddev->recovery);
+		md_wakeup_thread(mddev->thread);
+	} else if (need_resync) {
+		set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
+		set_bit(MD_RECOVERY_SYNC, &mddev->recovery);
+		md_wakeup_thread(mddev->thread);
+	}
+
+	return state;
+}
+
+static void llbitmap_raise_barrier(struct llbitmap *llbitmap, int page_idx)
+{
+	struct llbitmap_page_ctl *pctl = llbitmap->pctl[page_idx];
+
+retry:
+	if (likely(percpu_ref_tryget_live(&pctl->active))) {
+		WRITE_ONCE(pctl->expire, jiffies + llbitmap->barrier_idle * HZ);
+		return;
+	}
+
+	wait_event(pctl->wait, !percpu_ref_is_dying(&pctl->active));
+	goto retry;
+}
+
+static void llbitmap_release_barrier(struct llbitmap *llbitmap, int page_idx)
+{
+	struct llbitmap_page_ctl *pctl = llbitmap->pctl[page_idx];
+
+	percpu_ref_put(&pctl->active);
+}
+
+static int llbitmap_suspend_timeout(struct llbitmap *llbitmap, int page_idx)
+{
+	struct llbitmap_page_ctl *pctl = llbitmap->pctl[page_idx];
+
+	percpu_ref_kill(&pctl->active);
+
+	if (!wait_event_timeout(pctl->wait, percpu_ref_is_zero(&pctl->active),
+			llbitmap->mddev->bitmap_info.daemon_sleep * HZ)) {
+		percpu_ref_resurrect(&pctl->active);
+		return -ETIMEDOUT;
+	}
+
+	return 0;
+}
+
+static void llbitmap_resume(struct llbitmap *llbitmap, int page_idx)
+{
+	struct llbitmap_page_ctl *pctl = llbitmap->pctl[page_idx];
+
+	pctl->expire = LONG_MAX;
+	percpu_ref_resurrect(&pctl->active);
+	wake_up(&pctl->wait);
+}
+
+static int llbitmap_check_support(struct mddev *mddev)
+{
+	if (test_bit(MD_HAS_JOURNAL, &mddev->flags)) {
+		pr_notice("md/llbitmap: %s: array with journal cannot have bitmap\n",
+			  mdname(mddev));
+		return -EBUSY;
+	}
+
+	if (mddev->bitmap_info.space == 0) {
+		if (mddev->bitmap_info.default_space == 0) {
+			pr_notice("md/llbitmap: %s: no space for bitmap\n",
+				  mdname(mddev));
+			return -ENOSPC;
+		}
+	}
+
+	if (!mddev->persistent) {
+		pr_notice("md/llbitmap: %s: array must be persistent\n",
+			  mdname(mddev));
+		return -EOPNOTSUPP;
+	}
+
+	if (mddev->bitmap_info.file) {
+		pr_notice("md/llbitmap: %s: doesn't support bitmap file\n",
+			  mdname(mddev));
+		return -EOPNOTSUPP;
+	}
+
+	if (mddev->bitmap_info.external) {
+		pr_notice("md/llbitmap: %s: doesn't support external metadata\n",
+			  mdname(mddev));
+		return -EOPNOTSUPP;
+	}
+
+	if (mddev_is_dm(mddev)) {
+		pr_notice("md/llbitmap: %s: doesn't support dm-raid\n",
+			  mdname(mddev));
+		return -EOPNOTSUPP;
+	}
+
+	return 0;
+}
+
+static int llbitmap_init(struct llbitmap *llbitmap)
+{
+	struct mddev *mddev = llbitmap->mddev;
+	sector_t blocks = mddev->resync_max_sectors;
+	unsigned long chunksize = MIN_CHUNK_SIZE;
+	unsigned long chunks = DIV_ROUND_UP(blocks, chunksize);
+	unsigned long space = mddev->bitmap_info.space << SECTOR_SHIFT;
+	int ret;
+
+	while (chunks > space) {
+		chunksize = chunksize << 1;
+		chunks = DIV_ROUND_UP_SECTOR_T(blocks, chunksize);
+	}
+
+	llbitmap->barrier_idle = DEFAULT_BARRIER_IDLE;
+	llbitmap->chunkshift = ffz(~chunksize);
+	llbitmap->chunksize = chunksize;
+	llbitmap->chunks = chunks;
+	llbitmap->sync_size = blocks;
+	llbitmap_refresh_reshape(llbitmap);
+	mddev->bitmap_info.daemon_sleep = DEFAULT_DAEMON_SLEEP;
+
+	ret = llbitmap_alloc_pages(llbitmap);
+	if (ret)
+		return ret;
+
+	llbitmap_state_machine(llbitmap, 0, llbitmap->chunks - 1,
+			       BitmapActionInit);
+	/* flush initial llbitmap to disk */
+	__llbitmap_flush(mddev);
+
+	return 0;
+}
+
+static int llbitmap_read_sb(struct llbitmap *llbitmap)
+{
+	struct mddev *mddev = llbitmap->mddev;
+	unsigned long daemon_sleep;
+	unsigned long chunksize;
+	unsigned long events;
+	sector_t sync_size;
+	struct page *sb_page;
+	bitmap_super_t *sb;
+	int ret = -EINVAL;
+
+	if (!mddev->bitmap_info.offset) {
+		pr_err("md/llbitmap: %s: no super block found", mdname(mddev));
+		return -EINVAL;
+	}
+
+	sb_page = llbitmap_read_page(llbitmap, 0);
+	if (IS_ERR(sb_page)) {
+		pr_err("md/llbitmap: %s: read super block failed",
+		       mdname(mddev));
+		return -EIO;
+	}
+
+	sb = kmap_local_page(sb_page);
+	if (sb->magic != cpu_to_le32(BITMAP_MAGIC)) {
+		pr_err("md/llbitmap: %s: invalid super block magic number",
+		       mdname(mddev));
+		goto out_put_page;
+	}
+
+	if (sb->version != cpu_to_le32(BITMAP_MAJOR_LOCKLESS)) {
+		pr_err("md/llbitmap: %s: invalid super block version",
+		       mdname(mddev));
+		goto out_put_page;
+	}
+
+	if (memcmp(sb->uuid, mddev->uuid, 16)) {
+		pr_err("md/llbitmap: %s: bitmap superblock UUID mismatch\n",
+		       mdname(mddev));
+		goto out_put_page;
+	}
+
+	if (mddev->bitmap_info.space == 0) {
+		int room = le32_to_cpu(sb->sectors_reserved);
+
+		if (room)
+			mddev->bitmap_info.space = room;
+		else
+			mddev->bitmap_info.space = mddev->bitmap_info.default_space;
+	}
+	llbitmap->flags = le32_to_cpu(sb->state) & ~BIT(BITMAP_SHUTDOWN);
+	if (test_and_clear_bit(BITMAP_FIRST_USE, &llbitmap->flags)) {
+		ret = llbitmap_init(llbitmap);
+		goto out_put_page;
+	}
+
+	sync_size = le64_to_cpu(sb->sync_size);
+	if (!sync_size)
+		sync_size = mddev->resync_max_sectors;
+	if (sync_size > mddev->resync_max_sectors) {
+		pr_err("md/llbitmap: %s: sync_size %llu exceeds array sync size %llu",
+		       mdname(mddev), sync_size, mddev->resync_max_sectors);
+		goto out_put_page;
+	}
+	chunksize = le32_to_cpu(sb->chunksize);
+	if (!is_power_of_2(chunksize)) {
+		pr_err("md/llbitmap: %s: chunksize not a power of 2",
+		       mdname(mddev));
+		goto out_put_page;
+	}
+
+	if (chunksize < DIV_ROUND_UP_SECTOR_T(sync_size,
+					      mddev->bitmap_info.space << SECTOR_SHIFT)) {
+		pr_err("md/llbitmap: %s: chunksize too small %lu < %llu / %lu",
+		       mdname(mddev), chunksize, sync_size,
+		       mddev->bitmap_info.space);
+		goto out_put_page;
+	}
+
+	daemon_sleep = le32_to_cpu(sb->daemon_sleep);
+	if (daemon_sleep < 1 || daemon_sleep > MAX_SCHEDULE_TIMEOUT / HZ) {
+		pr_err("md/llbitmap: %s: daemon sleep %lu period out of range",
+		       mdname(mddev), daemon_sleep);
+		goto out_put_page;
+	}
+
+	events = le64_to_cpu(sb->events);
+	if (events < mddev->events) {
+		pr_warn("md/llbitmap :%s: bitmap file is out of date (%lu < %llu) -- forcing full recovery",
+			mdname(mddev), events, mddev->events);
+		set_bit(BITMAP_STALE, &llbitmap->flags);
+	}
+
+	sb->sync_size = cpu_to_le64(mddev->resync_max_sectors);
+	mddev->bitmap_info.chunksize = chunksize;
+	mddev->bitmap_info.daemon_sleep = daemon_sleep;
+
+	llbitmap->barrier_idle = DEFAULT_BARRIER_IDLE;
+	llbitmap->chunksize = chunksize;
+	llbitmap->chunks = DIV_ROUND_UP_SECTOR_T(sync_size, chunksize);
+	llbitmap->chunkshift = ffz(~chunksize);
+	llbitmap->sync_size = sync_size;
+	llbitmap_refresh_reshape(llbitmap);
+	ret = llbitmap_alloc_pages(llbitmap);
+
+out_put_page:
+	__free_page(sb_page);
+	kunmap_local(sb);
+	return ret;
+}
+
+static void llbitmap_pending_timer_fn(struct timer_list *pending_timer)
+{
+	struct llbitmap *llbitmap =
+		container_of(pending_timer, struct llbitmap, pending_timer);
+
+	if (test_bit(BITMAP_SHUTDOWN, &llbitmap->flags))
+		return;
+
+	if (work_busy(&llbitmap->daemon_work)) {
+		pr_warn("md/llbitmap: %s daemon_work not finished in %lu seconds\n",
+			mdname(llbitmap->mddev),
+			llbitmap->mddev->bitmap_info.daemon_sleep);
+		set_bit(BITMAP_DAEMON_BUSY, &llbitmap->flags);
+		return;
+	}
+
+	queue_work(md_llbitmap_io_wq, &llbitmap->daemon_work);
+}
+
+static void md_llbitmap_daemon_fn(struct work_struct *work)
+{
+	struct llbitmap *llbitmap =
+		container_of(work, struct llbitmap, daemon_work);
+	unsigned long start;
+	unsigned long end;
+	bool restart;
+	int idx;
+
+	if (test_bit(BITMAP_SHUTDOWN, &llbitmap->flags))
+		return;
+
+	if (llbitmap->mddev->degraded)
+		return;
+
+retry:
+	start = 0;
+	end = min(llbitmap->chunks, PAGE_SIZE - BITMAP_DATA_OFFSET) - 1;
+	restart = false;
+
+	for (idx = 0; idx < llbitmap->nr_pages; idx++) {
+		struct llbitmap_page_ctl *pctl = llbitmap->pctl[idx];
+		bool flush = test_and_clear_bit(LLPageFlush, &pctl->flags);
+
+		if (idx > 0) {
+			start = end + 1;
+			end = min(end + PAGE_SIZE, llbitmap->chunks - 1);
+		}
+
+		if (!flush && time_before(jiffies, pctl->expire)) {
+			restart = true;
+			continue;
+		}
+
+		if (llbitmap_suspend_timeout(llbitmap, idx) < 0) {
+			pr_warn("md/llbitmap: %s: %s waiting for page %d timeout\n",
+				mdname(llbitmap->mddev), __func__, idx);
+			continue;
+		}
+
+		llbitmap_state_machine(llbitmap, start, end, BitmapActionDaemon);
+		llbitmap_resume(llbitmap, idx);
+	}
+
+	/*
+	 * If the daemon took a long time to finish, retry to prevent missing
+	 * clearing dirty bits.
+	 */
+	if (test_and_clear_bit(BITMAP_DAEMON_BUSY, &llbitmap->flags))
+		goto retry;
+
+	/* If some page is dirty but not expired, setup timer again */
+	if (restart && !test_bit(BITMAP_SHUTDOWN, &llbitmap->flags))
+		mod_timer(&llbitmap->pending_timer,
+			  jiffies + llbitmap->mddev->bitmap_info.daemon_sleep * HZ);
+}
+
+static int llbitmap_create(struct mddev *mddev)
+{
+	struct llbitmap *llbitmap;
+	int ret;
+
+	ret = llbitmap_check_support(mddev);
+	if (ret)
+		return ret;
+
+	llbitmap = kzalloc_obj(*llbitmap, GFP_NOIO);
+	if (!llbitmap)
+		return -ENOMEM;
+
+	llbitmap->mddev = mddev;
+	llbitmap->io_size = bdev_logical_block_size(mddev->gendisk->part0);
+	llbitmap->blocks_per_page = PAGE_SIZE / llbitmap->io_size;
+
+	timer_setup(&llbitmap->pending_timer, llbitmap_pending_timer_fn, 0);
+	INIT_WORK(&llbitmap->daemon_work, md_llbitmap_daemon_fn);
+	rwlock_init(&llbitmap->reshape_lock);
+	atomic_set(&llbitmap->behind_writes, 0);
+	init_waitqueue_head(&llbitmap->behind_wait);
+
+	mutex_lock(&mddev->bitmap_info.mutex);
+	mddev->bitmap = llbitmap;
+	ret = llbitmap_read_sb(llbitmap);
+	if (ret)
+		mddev->bitmap = NULL;
+	mutex_unlock(&mddev->bitmap_info.mutex);
+	if (ret) {
+		kfree(llbitmap);
+	}
+
+	return ret;
+}
+
+static int llbitmap_resize(struct mddev *mddev, sector_t blocks, int chunksize)
+{
+	struct llbitmap *llbitmap = mddev->bitmap;
+	sector_t old_blocks = llbitmap->sync_size;
+	unsigned long old_chunks = llbitmap->chunks;
+	unsigned long chunks;
+	unsigned long cache_chunks;
+	int ret = 0;
+	unsigned long bitmap_chunksize;
+	bool reshape;
+	bool quiesced = false;
+
+	if (chunksize == 0)
+		chunksize = llbitmap->chunksize;
+
+	bitmap_chunksize = chunksize;
+	llbitmap_calculate_chunks(mddev, blocks, &bitmap_chunksize, &chunks);
+
+	reshape = mddev->delta_disks || mddev->new_level != mddev->level ||
+		mddev->new_layout != mddev->layout ||
+		mddev->new_chunk_sectors != mddev->chunk_sectors;
+	if (!reshape && bitmap_chunksize != llbitmap->chunksize)
+		return -EOPNOTSUPP;
+	if (blocks == old_blocks && chunks == llbitmap->chunks)
+		return 0;
+
+	if (mddev->pers->quiesce) {
+		mddev->pers->quiesce(mddev, 1);
+		quiesced = true;
+	}
+
+	mutex_lock(&mddev->bitmap_info.mutex);
+	cache_chunks = reshape ? max(old_chunks, chunks) : chunks;
+	ret = llbitmap_prepare_resize(llbitmap, old_chunks, chunks, cache_chunks);
+	if (ret)
+		goto out;
+
+	if (reshape) {
+		llbitmap->reshape_sync_size = blocks;
+		llbitmap->reshape_chunksize = bitmap_chunksize;
+		llbitmap->reshape_chunks = chunks;
+		llbitmap->chunks = max(old_chunks, chunks);
+	} else {
+		if (blocks < old_blocks && chunks < old_chunks)
+			llbitmap_mark_range(llbitmap, chunks, old_chunks - 1,
+					    BitUnwritten);
+		mddev->bitmap_info.chunksize = bitmap_chunksize;
+		llbitmap->chunks = chunks;
+		llbitmap->sync_size = blocks;
+		llbitmap_refresh_reshape(llbitmap);
+		llbitmap_update_sb(llbitmap);
+	}
+	__llbitmap_flush(mddev);
+	mutex_unlock(&mddev->bitmap_info.mutex);
+	if (quiesced)
+		mddev->pers->quiesce(mddev, 0);
+	return 0;
+
+out:
+	mutex_unlock(&mddev->bitmap_info.mutex);
+	if (quiesced)
+		mddev->pers->quiesce(mddev, 0);
+	return ret;
+}
+
+static int llbitmap_load(struct mddev *mddev)
+{
+	enum llbitmap_action action = BitmapActionReload;
+	struct llbitmap *llbitmap = mddev->bitmap;
+	int ret;
+
+	if (test_and_clear_bit(BITMAP_STALE, &llbitmap->flags))
+		action = BitmapActionStale;
+
+	mutex_lock(&mddev->bitmap_info.mutex);
+	llbitmap_refresh_reshape(llbitmap);
+	ret = llbitmap_expand_pages(llbitmap, llbitmap->chunks);
+	if (ret) {
+		mutex_unlock(&mddev->bitmap_info.mutex);
+		return ret;
+	}
+	llbitmap_state_machine(llbitmap, 0, llbitmap->chunks - 1, action);
+	mutex_unlock(&mddev->bitmap_info.mutex);
+	return 0;
+}
+
+static void llbitmap_destroy(struct mddev *mddev)
+{
+	struct llbitmap *llbitmap = mddev->bitmap;
+
+	if (!llbitmap)
+		return;
+
+	mutex_lock(&mddev->bitmap_info.mutex);
+
+	set_bit(BITMAP_SHUTDOWN, &llbitmap->flags);
+	timer_shutdown_sync(&llbitmap->pending_timer);
+	cancel_work_sync(&llbitmap->daemon_work);
+	flush_workqueue(md_llbitmap_io_wq);
+	flush_workqueue(md_llbitmap_unplug_wq);
+
+	mddev->bitmap = NULL;
+	llbitmap_free_pages(llbitmap);
+	kfree(llbitmap);
+	mutex_unlock(&mddev->bitmap_info.mutex);
+}
+
+static bool llbitmap_map_previous(struct llbitmap *llbitmap, sector_t offset,
+				  unsigned long sectors)
+{
+	struct mddev *mddev = llbitmap->mddev;
+	sector_t boundary = READ_ONCE(mddev->reshape_position);
+
+	if (boundary == MaxSector)
+		return false;
+
+	WARN_ON_ONCE(sectors && offset < boundary && offset + sectors > boundary);
+
+	return mddev->reshape_backwards ? offset < boundary : offset >= boundary;
+}
+
+static void llbitmap_prepare_range(struct mddev *mddev, sector_t *offset,
+				   unsigned long *sectors, bool discard)
+{
+	struct llbitmap *llbitmap = mddev->bitmap;
+	bool previous;
+
+	if (!llbitmap)
+		return;
+
+	previous = llbitmap_map_previous(llbitmap, *offset, *sectors);
+	llbitmap_map_layout(llbitmap, offset, sectors, previous);
+	if (discard)
+		llbitmap_encode_discard_range(llbitmap, offset, sectors, previous);
+	else
+		llbitmap_encode_range(llbitmap, offset, sectors, previous);
+}
+
+static void llbitmap_start_write(struct mddev *mddev, sector_t offset,
+				 unsigned long sectors)
+{
+	struct llbitmap *llbitmap = mddev->bitmap;
+	unsigned long start = offset >> llbitmap->chunkshift;
+	unsigned long end = (offset + sectors - 1) >> llbitmap->chunkshift;
+	int page_start = (start + BITMAP_DATA_OFFSET) >> PAGE_SHIFT;
+	int page_end = (end + BITMAP_DATA_OFFSET) >> PAGE_SHIFT;
+
+	while (page_start <= page_end) {
+		llbitmap_raise_barrier(llbitmap, page_start);
+		page_start++;
+	}
+
+	read_lock(&llbitmap->reshape_lock);
+	llbitmap_state_machine(llbitmap, start, end, BitmapActionStartwrite);
+	read_unlock(&llbitmap->reshape_lock);
+}
+
+static void llbitmap_end_write(struct mddev *mddev, sector_t offset,
+			       unsigned long sectors)
+{
+	struct llbitmap *llbitmap = mddev->bitmap;
+	unsigned long start = offset >> llbitmap->chunkshift;
+	unsigned long end = (offset + sectors - 1) >> llbitmap->chunkshift;
+	int page_start = (start + BITMAP_DATA_OFFSET) >> PAGE_SHIFT;
+	int page_end = (end + BITMAP_DATA_OFFSET) >> PAGE_SHIFT;
+
+	while (page_start <= page_end) {
+		llbitmap_release_barrier(llbitmap, page_start);
+		page_start++;
+	}
+}
+
+static void llbitmap_start_discard(struct mddev *mddev, sector_t offset,
+				   unsigned long sectors)
+{
+	struct llbitmap *llbitmap = mddev->bitmap;
+	unsigned long start = DIV_ROUND_UP_SECTOR_T(offset, llbitmap->chunksize);
+	unsigned long end = (offset + sectors - 1) >> llbitmap->chunkshift;
+	int page_start = (start + BITMAP_DATA_OFFSET) >> PAGE_SHIFT;
+	int page_end = (end + BITMAP_DATA_OFFSET) >> PAGE_SHIFT;
+
+	while (page_start <= page_end) {
+		llbitmap_raise_barrier(llbitmap, page_start);
+		page_start++;
+	}
+
+	read_lock(&llbitmap->reshape_lock);
+	llbitmap_state_machine(llbitmap, start, end, BitmapActionDiscard);
+	read_unlock(&llbitmap->reshape_lock);
+}
+
+static void llbitmap_end_discard(struct mddev *mddev, sector_t offset,
+				 unsigned long sectors)
+{
+	struct llbitmap *llbitmap = mddev->bitmap;
+	unsigned long start = DIV_ROUND_UP_SECTOR_T(offset, llbitmap->chunksize);
+	unsigned long end = (offset + sectors - 1) >> llbitmap->chunkshift;
+	int page_start = (start + BITMAP_DATA_OFFSET) >> PAGE_SHIFT;
+	int page_end = (end + BITMAP_DATA_OFFSET) >> PAGE_SHIFT;
+
+	while (page_start <= page_end) {
+		llbitmap_release_barrier(llbitmap, page_start);
+		page_start++;
+	}
+}
+
+static void llbitmap_unplug_fn(struct work_struct *work)
+{
+	struct llbitmap_unplug_work *unplug_work =
+		container_of(work, struct llbitmap_unplug_work, work);
+	struct llbitmap *llbitmap = unplug_work->llbitmap;
+	struct blk_plug plug;
+	int i;
+
+	blk_start_plug(&plug);
+
+	for (i = 0; i < llbitmap->nr_pages; i++) {
+		if (!test_bit(LLPageDirty, &llbitmap->pctl[i]->flags) ||
+		    !test_and_clear_bit(LLPageDirty, &llbitmap->pctl[i]->flags))
+			continue;
+
+		llbitmap_write_page(llbitmap, i);
+	}
+
+	blk_finish_plug(&plug);
+	md_super_wait(llbitmap->mddev);
+	complete(unplug_work->done);
+}
+
+static bool llbitmap_dirty(struct llbitmap *llbitmap)
+{
+	int i;
+
+	for (i = 0; i < llbitmap->nr_pages; i++)
+		if (test_bit(LLPageDirty, &llbitmap->pctl[i]->flags))
+			return true;
+
+	return false;
+}
+
+static void llbitmap_unplug(struct mddev *mddev, bool sync)
+{
+	DECLARE_COMPLETION_ONSTACK(done);
+	struct llbitmap *llbitmap = mddev->bitmap;
+	struct llbitmap_unplug_work unplug_work = {
+		.llbitmap = llbitmap,
+		.done = &done,
+	};
+
+	if (!llbitmap_dirty(llbitmap))
+		return;
+
+	/*
+	 * Issue new bitmap IO under submit_bio() context will deadlock:
+	 *  - the bio will wait for bitmap bio to be done, before it can be
+	 *  issued;
+	 *  - bitmap bio will be added to current->bio_list and wait for this
+	 *  bio to be issued;
+	 */
+	INIT_WORK_ONSTACK(&unplug_work.work, llbitmap_unplug_fn);
+	queue_work(md_llbitmap_unplug_wq, &unplug_work.work);
+	wait_for_completion(&done);
+	destroy_work_on_stack(&unplug_work.work);
+}
+
+/*
+ * Force to write all bitmap pages to disk, called when stopping the array, or
+ * every daemon_sleep seconds when sync_thread is running.
+ */
+static void __llbitmap_flush(struct mddev *mddev)
+{
+	struct llbitmap *llbitmap = mddev->bitmap;
+	struct blk_plug plug;
+	int i;
+
+	blk_start_plug(&plug);
+	for (i = 0; i < llbitmap->nr_pages; i++) {
+		struct llbitmap_page_ctl *pctl = llbitmap->pctl[i];
+
+		/* mark all blocks as dirty */
+		set_bit(LLPageDirty, &pctl->flags);
+		bitmap_fill(pctl->dirty, llbitmap->blocks_per_page);
+		llbitmap_write_page(llbitmap, i);
+	}
+	blk_finish_plug(&plug);
+	md_super_wait(llbitmap->mddev);
+}
+
+static void llbitmap_flush(struct mddev *mddev)
+{
+	struct llbitmap *llbitmap = mddev->bitmap;
+	int i;
+
+	for (i = 0; i < llbitmap->nr_pages; i++)
+		set_bit(LLPageFlush, &llbitmap->pctl[i]->flags);
+
+	timer_delete_sync(&llbitmap->pending_timer);
+	queue_work(md_llbitmap_io_wq, &llbitmap->daemon_work);
+	flush_work(&llbitmap->daemon_work);
+
+	__llbitmap_flush(mddev);
+}
+
+/* This is used for raid5 lazy initial recovery */
+static bool llbitmap_blocks_synced(struct mddev *mddev, sector_t offset)
+{
+	struct llbitmap *llbitmap = mddev->bitmap;
+	unsigned long p = offset >> llbitmap->chunkshift;
+	enum llbitmap_state c;
+
+	if (p >= llbitmap->chunks)
+		return false;
+	c = llbitmap_read(llbitmap, p);
+
+	return c == BitClean || c == BitDirty || c == BitCleanUnwritten;
+}
+
+static sector_t llbitmap_skip_sync_blocks(struct mddev *mddev, sector_t offset)
+{
+	struct llbitmap *llbitmap = mddev->bitmap;
+	unsigned long p = offset >> llbitmap->chunkshift;
+	int blocks = llbitmap->chunksize - (offset & (llbitmap->chunksize - 1));
+	enum llbitmap_state c;
+
+	if (p >= llbitmap->chunks)
+		return 0;
+	c = llbitmap_read(llbitmap, p);
+
+	/*
+	 * Reshape progress is tracked by array metadata rather than llbitmap.
+	 * Skipping reshape ranges from stale bitmap state can lose data after a
+	 * restart before the corresponding bits are checkpointed to disk.
+	 */
+	if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery))
+		return 0;
+
+	/* always skip unwritten blocks */
+	if (c == BitUnwritten)
+		return blocks;
+
+	/* Skip CleanUnwritten - no user data, will be reset after recovery */
+	if (c == BitCleanUnwritten)
+		return blocks;
+
+	/* For degraded array, don't skip */
+	if (mddev->degraded)
+		return 0;
+
+	/* For resync also skip clean/dirty blocks */
+	if ((c == BitClean || c == BitDirty) &&
+	    test_bit(MD_RECOVERY_SYNC, &mddev->recovery) &&
+	    !test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery))
+		return blocks;
+
+	return 0;
+}
+
+static bool llbitmap_start_sync(struct mddev *mddev, sector_t offset,
+				sector_t *blocks, bool degraded)
+{
+	struct llbitmap *llbitmap = mddev->bitmap;
+	unsigned long p = offset >> llbitmap->chunkshift;
+	enum llbitmap_state state;
+
+	/*
+	 * Before recovery starts, convert CleanUnwritten to Unwritten.
+	 * This ensures the new disk won't have stale parity data.
+	 */
+	if (offset == 0 && test_bit(MD_RECOVERY_RECOVER, &mddev->recovery) &&
+	    !test_bit(MD_RECOVERY_LAZY_RECOVER, &mddev->recovery))
+		llbitmap_state_machine(llbitmap, 0, llbitmap->chunks - 1,
+				       BitmapActionClearUnwritten);
+
+
+	/*
+	 * Handle one bit at a time, this is much simpler. And it doesn't matter
+	 * if md_do_sync() loop more times.
+	 */
+	*blocks = llbitmap->chunksize - (offset & (llbitmap->chunksize - 1));
+	if (p >= llbitmap->chunks)
+		return false;
+	state = llbitmap_state_machine(llbitmap, p, p, BitmapActionStartsync);
+	return state == BitSyncing || state == BitSyncingUnwritten;
+}
+
+/* Something is wrong, sync_thread stop at @offset */
+static void llbitmap_end_sync(struct mddev *mddev, sector_t offset,
+			      sector_t *blocks)
+{
+	struct llbitmap *llbitmap = mddev->bitmap;
+	unsigned long p = offset >> llbitmap->chunkshift;
+
+	*blocks = llbitmap->chunksize - (offset & (llbitmap->chunksize - 1));
+	llbitmap_state_machine(llbitmap, p, llbitmap->chunks - 1,
+			       BitmapActionAbortsync);
+}
+
+/* A full sync_thread is finished */
+static void llbitmap_close_sync(struct mddev *mddev)
+{
+	struct llbitmap *llbitmap = mddev->bitmap;
+	int i;
+
+	for (i = 0; i < llbitmap->nr_pages; i++) {
+		struct llbitmap_page_ctl *pctl = llbitmap->pctl[i];
+
+		/* let daemon_fn clear dirty bits immediately */
+		WRITE_ONCE(pctl->expire, jiffies);
+	}
+
+	llbitmap_state_machine(llbitmap, 0, llbitmap->chunks - 1,
+			       BitmapActionEndsync);
+}
+
+/*
+ * sync_thread have reached @sector, update metadata every daemon_sleep seconds,
+ * just in case sync_thread have to restart after power failure.
+ */
+static void llbitmap_cond_end_sync(struct mddev *mddev, sector_t sector,
+				   bool force)
+{
+	struct llbitmap *llbitmap = mddev->bitmap;
+	sector_t complete;
+
+	if (sector == 0) {
+		llbitmap->last_end_sync = jiffies;
+		return;
+	}
+
+	if (!force && time_before(jiffies, llbitmap->last_end_sync +
+				  HZ * mddev->bitmap_info.daemon_sleep))
+		return;
+
+	wait_event(mddev->recovery_wait, !atomic_read(&mddev->recovery_active));
+
+	mddev->curr_resync_completed = sector;
+	set_bit(MD_SB_CHANGE_CLEAN, &mddev->sb_flags);
+
+	complete = round_down(sector, llbitmap->chunksize);
+	if (complete)
+		llbitmap_state_machine(llbitmap, 0,
+				       (complete >> llbitmap->chunkshift) - 1,
+				       BitmapActionEndsync);
+	__llbitmap_flush(mddev);
+
+	llbitmap->last_end_sync = jiffies;
+	sysfs_notify_dirent_safe(mddev->sysfs_completed);
+}
+
+static bool llbitmap_enabled(void *data, bool flush)
+{
+	struct llbitmap *llbitmap = data;
+
+	return llbitmap && !test_bit(BITMAP_WRITE_ERROR, &llbitmap->flags);
+}
+
+static void llbitmap_dirty_bits(struct mddev *mddev, unsigned long s,
+				unsigned long e)
+{
+	llbitmap_state_machine(mddev->bitmap, s, e, BitmapActionStartwrite);
+}
+
+static int llbitmap_reshape_can_start(struct mddev *mddev)
+{
+	struct llbitmap *llbitmap = mddev->bitmap;
+	unsigned long chunk;
+	int ret = 0;
+
+	if (!llbitmap)
+		return 0;
+
+	mutex_lock(&mddev->bitmap_info.mutex);
+	for (chunk = 0; chunk < llbitmap->chunks; chunk++) {
+		enum llbitmap_state state = llbitmap_read(llbitmap, chunk);
+
+		if (state == BitNeedSync || state == BitSyncing) {
+			ret = -EBUSY;
+			break;
+		}
+	}
+	mutex_unlock(&mddev->bitmap_info.mutex);
+
+	return ret;
+}
+
+struct llbitmap_reshape_range {
+	sector_t offset;
+	unsigned long sectors;
+	sector_t start;
+	sector_t end;
+};
+
+static enum llbitmap_state
+llbitmap_reshape_init_dst(struct llbitmap *llbitmap, unsigned long dst,
+			  const struct llbitmap_reshape_range *new)
+{
+	u64 bit_start = (u64)dst * llbitmap->reshape_chunksize;
+	u64 bit_end = bit_start + llbitmap->reshape_chunksize;
+
+	if (!llbitmap->mddev->reshape_backwards)
+		return bit_start < new->offset ? llbitmap_read(llbitmap, dst) :
+		       BitUnwritten;
+	return bit_end > new->end ? llbitmap_read(llbitmap, dst) : BitUnwritten;
+}
+
+static void llbitmap_reshape_dst_range(struct llbitmap *llbitmap,
+				       unsigned long dst,
+				       const struct llbitmap_reshape_range *new,
+				       struct llbitmap_reshape_range *dst_range)
+{
+	sector_t dst_bit_start = (sector_t)dst * llbitmap->reshape_chunksize;
+
+	dst_range->start = max(dst_bit_start, new->offset);
+	dst_range->end = min(dst_bit_start + llbitmap->reshape_chunksize,
+			     new->end);
+	dst_range->offset = dst_range->start;
+	dst_range->sectors = dst_range->end - dst_range->start;
+}
+
+static void llbitmap_reshape_map_range(struct llbitmap *llbitmap,
+				       sector_t lo, sector_t hi,
+				       bool previous,
+				       struct llbitmap_reshape_range *range)
+{
+	range->offset = lo;
+	range->sectors = hi - lo;
+	llbitmap_map_layout(llbitmap, &range->offset, &range->sectors, previous);
+	range->start = range->offset;
+	range->end = range->offset + range->sectors;
+}
+
+static bool llbitmap_reshape_src_range(const struct llbitmap_reshape_range *old,
+				       const struct llbitmap_reshape_range *new,
+				       const struct llbitmap_reshape_range *dst,
+				       struct llbitmap_reshape_range *src)
+{
+	if (!old->sectors)
+		return false;
+
+	src->start = old->offset +
+		mul_u64_u64_div_u64(dst->start - new->offset,
+				    old->sectors, new->sectors);
+	src->end = old->offset +
+		mul_u64_u64_div_u64_roundup(dst->end - new->offset,
+					    old->sectors, new->sectors);
+	if (src->end > old->end)
+		src->end = old->end;
+	src->offset = src->start;
+	src->sectors = src->end - src->start;
+
+	return src->sectors;
+}
+
+static enum llbitmap_state llbitmap_rmerge_src(struct llbitmap *llbitmap,
+					       enum llbitmap_state state,
+					       const struct llbitmap_reshape_range *src)
+{
+	unsigned long bit = div64_u64(src->start, llbitmap->chunksize);
+	unsigned long end = div64_u64(src->end - 1, llbitmap->chunksize);
+
+	while (bit <= end) {
+		enum llbitmap_state src_state = llbitmap_read(llbitmap, bit);
+
+		state = llbitmap_rmerge_state(llbitmap, state, src_state);
+		bit++;
+	}
+
+	return state;
+}
+
+static void llbitmap_reshape_merge(struct llbitmap *llbitmap,
+				   const struct llbitmap_reshape_range *old,
+				   const struct llbitmap_reshape_range *new)
+{
+	unsigned long dst_start;
+	unsigned long dst_end;
+	unsigned long dst;
+	bool backwards = false;
+
+	if (!new->sectors)
+		return;
+
+	dst_start = div64_u64(new->offset, llbitmap->reshape_chunksize);
+	dst_end = div64_u64(new->end - 1, llbitmap->reshape_chunksize);
+	if (old->sectors) {
+		unsigned long src_start = div64_u64(old->offset,
+						    llbitmap->chunksize);
+		unsigned long src_end = div64_u64(old->end - 1,
+						  llbitmap->chunksize);
+
+		backwards = src_start < dst_start && src_end >= dst_start;
+	}
+
+	dst = backwards ? dst_end : dst_start;
+	while (true) {
+		struct llbitmap_reshape_range dst_range;
+		struct llbitmap_reshape_range src;
+		enum llbitmap_state state;
+
+		llbitmap_reshape_dst_range(llbitmap, dst, new, &dst_range);
+		state = llbitmap_reshape_init_dst(llbitmap, dst, new);
+		if (llbitmap_reshape_src_range(old, new, &dst_range, &src))
+			state = llbitmap_rmerge_src(llbitmap, state, &src);
+		else
+			state = llbitmap_rmerge_state(llbitmap, state, BitUnwritten);
+		llbitmap_write(llbitmap, state, dst);
+		if (dst == (backwards ? dst_start : dst_end))
+			break;
+		if (backwards)
+			dst--;
+		else
+			dst++;
+	}
+}
+
+static void llbitmap_reshape_finish(struct mddev *mddev)
+{
+	struct llbitmap *llbitmap = mddev->bitmap;
+
+	if (mddev->pers->quiesce)
+		mddev->pers->quiesce(mddev, 1);
+
+	mutex_lock(&mddev->bitmap_info.mutex);
+	llbitmap_flush(mddev);
+
+	llbitmap->chunksize = llbitmap->reshape_chunksize;
+	llbitmap->chunkshift = ffz(~llbitmap->chunksize);
+	llbitmap->chunks = llbitmap->reshape_chunks;
+	llbitmap->sync_size = llbitmap->reshape_sync_size;
+	llbitmap_refresh_reshape(llbitmap);
+	mddev->bitmap_info.chunksize = llbitmap->chunksize;
+	llbitmap_update_sb(llbitmap);
+	__llbitmap_flush(mddev);
+	mutex_unlock(&mddev->bitmap_info.mutex);
+
+	if (mddev->pers->quiesce)
+		mddev->pers->quiesce(mddev, 0);
+}
+
+static void llbitmap_reshape_mark(struct mddev *mddev, sector_t old_pos,
+				  sector_t new_pos)
+{
+	struct llbitmap *llbitmap = mddev->bitmap;
+	sector_t lo;
+	sector_t hi;
+	struct llbitmap_reshape_range old;
+	struct llbitmap_reshape_range new;
+
+	if (!llbitmap || old_pos == new_pos)
+		return;
+
+	lo = min(old_pos, new_pos);
+	hi = max(old_pos, new_pos);
+	if (!hi)
+		return;
+
+	llbitmap_reshape_map_range(llbitmap, lo, hi, true, &old);
+	llbitmap_reshape_map_range(llbitmap, lo, hi, false, &new);
+	if (!new.sectors)
+		return;
+
+	write_lock(&llbitmap->reshape_lock);
+	llbitmap_reshape_merge(llbitmap, &old, &new);
+	write_unlock(&llbitmap->reshape_lock);
+}
+
+static void llbitmap_write_sb(struct llbitmap *llbitmap)
+{
+	int nr_blocks = DIV_ROUND_UP(BITMAP_DATA_OFFSET, llbitmap->io_size);
+
+	bitmap_fill(llbitmap->pctl[0]->dirty, nr_blocks);
+	llbitmap_write_page(llbitmap, 0);
+	md_super_wait(llbitmap->mddev);
+}
+
+static void llbitmap_update_sb(void *data)
+{
+	struct llbitmap *llbitmap = data;
+	struct mddev *mddev = llbitmap->mddev;
+	struct page *sb_page;
+	bitmap_super_t *sb;
+
+	if (test_bit(BITMAP_WRITE_ERROR, &llbitmap->flags))
+		return;
+
+	sb_page = llbitmap_read_page(llbitmap, 0);
+	if (IS_ERR(sb_page)) {
+		pr_err("%s: %s: read super block failed", __func__,
+		       mdname(mddev));
+		set_bit(BITMAP_WRITE_ERROR, &llbitmap->flags);
+		return;
+	}
+
+	if (mddev->events < llbitmap->events_cleared)
+		llbitmap->events_cleared = mddev->events;
+
+	sb = kmap_local_page(sb_page);
+	sb->events = cpu_to_le64(mddev->events);
+	sb->state = cpu_to_le32(llbitmap->flags & ~BIT(BITMAP_SHUTDOWN));
+	sb->chunksize = cpu_to_le32(llbitmap->chunksize);
+	sb->sync_size = cpu_to_le64(llbitmap->sync_size);
+	sb->events_cleared = cpu_to_le64(llbitmap->events_cleared);
+	sb->sectors_reserved = cpu_to_le32(mddev->bitmap_info.space);
+	sb->daemon_sleep = cpu_to_le32(mddev->bitmap_info.daemon_sleep);
+
+	kunmap_local(sb);
+	llbitmap_write_sb(llbitmap);
+}
+
+static int llbitmap_get_stats(void *data, struct md_bitmap_stats *stats)
+{
+	struct llbitmap *llbitmap = data;
+
+	memset(stats, 0, sizeof(*stats));
+
+	stats->missing_pages = 0;
+	stats->pages = llbitmap->nr_pages;
+	stats->file_pages = llbitmap->nr_pages;
+	stats->sync_size = llbitmap->sync_size;
+
+	stats->behind_writes = atomic_read(&llbitmap->behind_writes);
+	stats->behind_wait = wq_has_sleeper(&llbitmap->behind_wait);
+	stats->events_cleared = llbitmap->events_cleared;
+
+	return 0;
+}
+
+/* just flag all pages as needing to be written */
+static void llbitmap_write_all(struct mddev *mddev)
+{
+	int i;
+	struct llbitmap *llbitmap = mddev->bitmap;
+
+	for (i = 0; i < llbitmap->nr_pages; i++) {
+		struct llbitmap_page_ctl *pctl = llbitmap->pctl[i];
+
+		set_bit(LLPageDirty, &pctl->flags);
+		bitmap_fill(pctl->dirty, llbitmap->blocks_per_page);
+	}
+}
+
+static void llbitmap_start_behind_write(struct mddev *mddev)
+{
+	struct llbitmap *llbitmap = mddev->bitmap;
+
+	atomic_inc(&llbitmap->behind_writes);
+}
+
+static void llbitmap_end_behind_write(struct mddev *mddev)
+{
+	struct llbitmap *llbitmap = mddev->bitmap;
+
+	if (atomic_dec_and_test(&llbitmap->behind_writes))
+		wake_up(&llbitmap->behind_wait);
+}
+
+static void llbitmap_wait_behind_writes(struct mddev *mddev)
+{
+	struct llbitmap *llbitmap = mddev->bitmap;
+
+	if (llbitmap && atomic_read(&llbitmap->behind_writes) > 0)
+		wait_event(llbitmap->behind_wait,
+			   atomic_read(&llbitmap->behind_writes) == 0);
+}
+
+static ssize_t bits_show(struct mddev *mddev, char *page)
+{
+	struct llbitmap *llbitmap;
+	int bits[BitStateCount] = {0};
+	loff_t start = 0;
+
+	mutex_lock(&mddev->bitmap_info.mutex);
+	llbitmap = mddev->bitmap;
+	if (!llbitmap || !llbitmap->pctl) {
+		mutex_unlock(&mddev->bitmap_info.mutex);
+		return sprintf(page, "no bitmap\n");
+	}
+
+	if (test_bit(BITMAP_WRITE_ERROR, &llbitmap->flags)) {
+		mutex_unlock(&mddev->bitmap_info.mutex);
+		return sprintf(page, "bitmap io error\n");
+	}
+
+	while (start < llbitmap->chunks) {
+		enum llbitmap_state c = llbitmap_read(llbitmap, start);
+
+		if (c < 0 || c >= BitStateCount)
+			pr_err("%s: invalid bit %llu state %d\n",
+			       __func__, start, c);
+		else
+			bits[c]++;
+		start++;
+	}
+
+	mutex_unlock(&mddev->bitmap_info.mutex);
+	return sprintf(page,
+		       "unwritten %d\nclean %d\ndirty %d\n"
+		       "need sync %d\nsyncing %d\n"
+		       "need sync unwritten %d\nsyncing unwritten %d\n"
+		       "clean unwritten %d\n",
+		       bits[BitUnwritten], bits[BitClean], bits[BitDirty],
+		       bits[BitNeedSync], bits[BitSyncing],
+		       bits[BitNeedSyncUnwritten], bits[BitSyncingUnwritten],
+		       bits[BitCleanUnwritten]);
+}
+
+static struct md_sysfs_entry llbitmap_bits = __ATTR_RO(bits);
+
+static ssize_t metadata_show(struct mddev *mddev, char *page)
+{
+	struct llbitmap *llbitmap;
+	ssize_t ret;
+
+	mutex_lock(&mddev->bitmap_info.mutex);
+	llbitmap = mddev->bitmap;
+	if (!llbitmap) {
+		mutex_unlock(&mddev->bitmap_info.mutex);
+		return sprintf(page, "no bitmap\n");
+	}
+
+	ret =  sprintf(page, "chunksize %lu\nchunkshift %lu\nchunks %lu\noffset %llu\ndaemon_sleep %lu\n",
+		       llbitmap->chunksize, llbitmap->chunkshift,
+		       llbitmap->chunks, mddev->bitmap_info.offset,
+		       llbitmap->mddev->bitmap_info.daemon_sleep);
+	mutex_unlock(&mddev->bitmap_info.mutex);
+
+	return ret;
+}
+
+static struct md_sysfs_entry llbitmap_metadata = __ATTR_RO(metadata);
+
+static ssize_t
+daemon_sleep_show(struct mddev *mddev, char *page)
+{
+	return sprintf(page, "%lu\n", mddev->bitmap_info.daemon_sleep);
+}
+
+static ssize_t
+daemon_sleep_store(struct mddev *mddev, const char *buf, size_t len)
+{
+	unsigned long timeout;
+	int rv = kstrtoul(buf, 10, &timeout);
+
+	if (rv)
+		return rv;
+
+	mddev->bitmap_info.daemon_sleep = timeout;
+	return len;
+}
+
+static struct md_sysfs_entry llbitmap_daemon_sleep = __ATTR_RW(daemon_sleep);
+
+static ssize_t
+barrier_idle_show(struct mddev *mddev, char *page)
+{
+	struct llbitmap *llbitmap = mddev->bitmap;
+
+	return sprintf(page, "%lu\n", llbitmap->barrier_idle);
+}
+
+static ssize_t
+barrier_idle_store(struct mddev *mddev, const char *buf, size_t len)
+{
+	struct llbitmap *llbitmap = mddev->bitmap;
+	unsigned long timeout;
+	int rv = kstrtoul(buf, 10, &timeout);
+
+	if (rv)
+		return rv;
+
+	llbitmap->barrier_idle = timeout;
+	return len;
+}
+
+static struct md_sysfs_entry llbitmap_barrier_idle = __ATTR_RW(barrier_idle);
+
+static ssize_t
+proactive_sync_store(struct mddev *mddev, const char *buf, size_t len)
+{
+	struct llbitmap *llbitmap;
+
+	/* Only for RAID-456 */
+	if (!raid_is_456(mddev))
+		return -EINVAL;
+
+	mutex_lock(&mddev->bitmap_info.mutex);
+	llbitmap = mddev->bitmap;
+	if (!llbitmap || !llbitmap->pctl) {
+		mutex_unlock(&mddev->bitmap_info.mutex);
+		return -ENODEV;
+	}
+
+	/* Trigger proactive sync on all Unwritten regions */
+	llbitmap_state_machine(llbitmap, 0, llbitmap->chunks - 1,
+			       BitmapActionProactiveSync);
+
+	mutex_unlock(&mddev->bitmap_info.mutex);
+	return len;
+}
+
+static struct md_sysfs_entry llbitmap_proactive_sync =
+	__ATTR(proactive_sync, 0200, NULL, proactive_sync_store);
+
+static struct attribute *md_llbitmap_attrs[] = {
+	&llbitmap_bits.attr,
+	&llbitmap_metadata.attr,
+	&llbitmap_daemon_sleep.attr,
+	&llbitmap_barrier_idle.attr,
+	&llbitmap_proactive_sync.attr,
+	NULL
+};
+
+static struct attribute_group md_llbitmap_group = {
+	.name = "llbitmap",
+	.attrs = md_llbitmap_attrs,
+};
+
+static const struct attribute_group *md_llbitmap_groups[] = {
+	&md_llbitmap_group,
+	NULL,
+};
+
+static struct bitmap_operations llbitmap_ops = {
+	.head = {
+		.type	= MD_BITMAP,
+		.id	= ID_LLBITMAP,
+		.name	= "llbitmap",
+	},
+
+	.enabled		= llbitmap_enabled,
+	.create			= llbitmap_create,
+	.resize			= llbitmap_resize,
+	.load			= llbitmap_load,
+	.destroy		= llbitmap_destroy,
+
+	.start_write		= llbitmap_start_write,
+	.end_write		= llbitmap_end_write,
+	.start_discard		= llbitmap_start_discard,
+	.end_discard		= llbitmap_end_discard,
+	.unplug			= llbitmap_unplug,
+	.flush			= llbitmap_flush,
+
+	.start_behind_write	= llbitmap_start_behind_write,
+	.end_behind_write	= llbitmap_end_behind_write,
+	.wait_behind_writes	= llbitmap_wait_behind_writes,
+
+	.blocks_synced		= llbitmap_blocks_synced,
+	.skip_sync_blocks	= llbitmap_skip_sync_blocks,
+	.start_sync		= llbitmap_start_sync,
+	.end_sync		= llbitmap_end_sync,
+	.close_sync		= llbitmap_close_sync,
+	.cond_end_sync		= llbitmap_cond_end_sync,
+
+	.update_sb		= llbitmap_update_sb,
+	.get_stats		= llbitmap_get_stats,
+	.dirty_bits		= llbitmap_dirty_bits,
+	.prepare_range		= llbitmap_prepare_range,
+	.reshape_finish		= llbitmap_reshape_finish,
+	.reshape_can_start	= llbitmap_reshape_can_start,
+	.reshape_mark		= llbitmap_reshape_mark,
+	.write_all		= llbitmap_write_all,
+
+	.groups			= md_llbitmap_groups,
+};
+
+int md_llbitmap_init(void)
+{
+	md_llbitmap_io_wq = alloc_workqueue("md_llbitmap_io",
+					 WQ_MEM_RECLAIM | WQ_UNBOUND, 0);
+	if (!md_llbitmap_io_wq)
+		return -ENOMEM;
+
+	md_llbitmap_unplug_wq = alloc_workqueue("md_llbitmap_unplug",
+					 WQ_MEM_RECLAIM | WQ_UNBOUND, 0);
+	if (!md_llbitmap_unplug_wq) {
+		destroy_workqueue(md_llbitmap_io_wq);
+		md_llbitmap_io_wq = NULL;
+		return -ENOMEM;
+	}
+
+	return register_md_submodule(&llbitmap_ops.head);
+}
+
+void md_llbitmap_exit(void)
+{
+	destroy_workqueue(md_llbitmap_io_wq);
+	md_llbitmap_io_wq = NULL;
+	destroy_workqueue(md_llbitmap_unplug_wq);
+	md_llbitmap_unplug_wq = NULL;
+	unregister_md_submodule(&llbitmap_ops.head);
+}