[PATCH RFC -next v2 41/41] md/md-bitmap: make in memory structure internal

Yu Kuai
2024-08-14T07:15:45Z

Now that struct btimap_page and bitmap is not used external anymore,
move them from md-bitmap.h to md-bitmap.c.(expect that dm-raid is still
using define marco 'COUNTER_MAX').

Also fix some checkpatch warnings.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
---
drivers/md/md-bitmap.c | 247 ++++++++++++++++++++++++++++++++++++----
drivers/md/md-bitmap.h | 189 +-----------------------------
drivers/md/md-cluster.c | 4 +-
drivers/md/md.c | 2 +-
drivers/md/md.h | 2 +-
drivers/md/raid1.c | 6 +-
6 files changed, 237 insertions(+), 213 deletions(-)

diff --git a/drivers/md/md-bitmap.c b/drivers/md/md-bitmap.c
index 8b9f0560f02f..0aee595f5c79 100644
--- a/drivers/md/md-bitmap.c
+++ b/drivers/md/md-bitmap.c
@@ -32,6 +32,186 @@
#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 mddev *mddev, sector_t blocks, int chunksize,
bool init);

@@ -491,9 +671,10 @@ static void md_bitmap_wait_writes(struct bitmap *bitmap)

/* update the event counter and sync the superblock to disk */
-static void 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;
@@ -1844,10 +2025,11 @@ static void bitmap_flush(struct mddev *mddev)
bitmap_update_sb(bitmap);
}

-static 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;
@@ -2075,7 +2257,7 @@ static int bitmap_load(struct mddev *mddev)
}

/* caller need to free returned bitmap with md_bitmap_free() */
-static struct bitmap *bitmap_get_from_slot(struct mddev *mddev, int slot)
+static void *bitmap_get_from_slot(struct mddev *mddev, int slot)
{
int rv = 0;
struct bitmap *bitmap;
@@ -2142,15 +2324,18 @@ static int bitmap_copy_from_slot(struct mddev *mddev, int slot, sector_t *low,
return rv;
}

-static void bitmap_set_pages(struct bitmap *bitmap, unsigned long pages)
+static void bitmap_set_pages(void *data, unsigned long pages)
{
+ struct bitmap *bitmap = data;
+
bitmap->counts.pages = pages;
}

-static int bitmap_get_stats(struct bitmap *bitmap, struct md_bitmap_stats *stats)
+static int bitmap_get_stats(void *data, struct md_bitmap_stats *stats)
{
bitmap_super_t *sb;
struct bitmap_counts *counts;
+ struct bitmap *bitmap = data;

if (!bitmap)
return -ENOENT;
@@ -2499,6 +2684,7 @@ 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;

@@ -2509,8 +2695,8 @@ 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
@@ -2687,10 +2873,13 @@ __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);
@@ -2699,17 +2888,24 @@ 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 =
@@ -2719,21 +2915,26 @@ 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;
}

diff --git a/drivers/md/md-bitmap.h b/drivers/md/md-bitmap.h
index 364e00833aef..06c46b4e58f4 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 {
@@ -152,88 +58,6 @@ typedef struct bitmap_super_s {
* devices. For raid10 it is the size of the array.
*/

-#ifdef __KERNEL__
-
-/* 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;
- 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 md_bitmap_stats {
unsigned long pages;
unsigned long missing_pages;
@@ -271,17 +95,17 @@ struct bitmap_operations {
void (*cond_end_sync)(struct mddev *mddev, sector_t sector, bool force);
void (*close_sync)(struct mddev *mddev);

- void (*update_sb)(struct bitmap *bitmap);
- int (*get_stats)(struct bitmap *bitmap, struct md_bitmap_stats *stats);
+ 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);
- struct bitmap *(*get_from_slot)(struct mddev *mddev, int slot);
+ 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)(struct bitmap *bitmap, unsigned long pages);
- void (*free)(struct bitmap *bitmap);
+ void (*set_pages)(void *data, unsigned long pages);
+ void (*free)(void *data);
};

/* the bitmap API */
@@ -299,4 +123,3 @@ static inline u64 md_bitmap_events_cleared(struct mddev *mddev)
}

#endif
-#endif
diff --git a/drivers/md/md-cluster.c b/drivers/md/md-cluster.c
index da94f7251da7..eadefa24b8cc 100644
--- a/drivers/md/md-cluster.c
+++ b/drivers/md/md-cluster.c
@@ -1145,7 +1145,7 @@ 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 dlm_lock_resource *bm_lockres;
- struct bitmap *bitmap = mddev->bitmap;
+ void *bitmap = mddev->bitmap;
struct md_bitmap_stats stats;
unsigned long my_pages;
char str[64];
@@ -1219,7 +1219,7 @@ static int cluster_check_sync_size(struct mddev *mddev)
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;
+ void *bitmap = mddev->bitmap;
char str[64];
struct dlm_lock_resource *bm_lockres;
struct md_bitmap_stats stats;
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 6800888152d0..3ba45c41dc0e 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -2324,7 +2324,7 @@ 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 = rdev->mddev->bitmap;
+ void *bitmap = rdev->mddev->bitmap;
struct md_bitmap_stats stats;
int err;

diff --git a/drivers/md/md.h b/drivers/md/md.h
index e56193f71ab4..1c6a5f41adca 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -535,7 +535,7 @@ 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 */
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 17b1965fec56..6651d44d8605 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -1425,7 +1425,6 @@ 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;
@@ -1578,7 +1577,7 @@ 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)) {
@@ -1606,7 +1605,8 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio,

if (first_clone) {
struct md_bitmap_stats stats;
- int err = mddev->bitmap_ops->get_stats(bitmap, &stats);
+ int err = mddev->bitmap_ops->get_stats(mddev->bitmap,
+ &stats);

/* do behind I/O ?
* Not if there are too many, or cannot
--
2.39.2