[PATCH RFC -next v2 07/41] md/md-bitmap: add 'behind_writes' and 'behind_wait' into struct md_bitmap_stats

[Yu Kuai]

From: Yu Kuai <yukuai3@xxxxxxxxxx>

There are no functional changes, avoid dereferencing bitmap directly to
prepare inventing a new bitmap.

Also fix following checkpatch warning by using wq_has_sleeper().

WARNING: waitqueue_active without comment

Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
---
 drivers/md/md-bitmap.c |  2 ++
 drivers/md/md-bitmap.h |  2 ++
 drivers/md/raid1.c     | 12 +++++++-----
 3 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/drivers/md/md-bitmap.c b/drivers/md/md-bitmap.c
index cd304240aaa6..7dcb025207b8 100644
--- a/drivers/md/md-bitmap.c
+++ b/drivers/md/md-bitmap.c
@@ -2113,6 +2113,8 @@ int md_bitmap_get_stats(struct bitmap *bitmap, struct md_bitmap_stats *stats)
 	stats->file = bitmap->storage.file;
 	stats->events_cleared = bitmap->events_cleared;
 
+	stats->behind_writes = atomic_read(&bitmap->behind_writes);
+	stats->behind_wait = wq_has_sleeper(&bitmap->behind_wait);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(md_bitmap_get_stats);
diff --git a/drivers/md/md-bitmap.h b/drivers/md/md-bitmap.h
index 52ef4dae8f3e..119644907f89 100644
--- a/drivers/md/md-bitmap.h
+++ b/drivers/md/md-bitmap.h
@@ -241,6 +241,8 @@ struct md_bitmap_stats {
 	unsigned long sync_size;
 	struct file *file;
 	u64 events_cleared;
+	int behind_writes;
+	bool behind_wait;
 };
 
 /* the bitmap API */
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 81fc100e7830..bfd2d63d1c59 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -1603,16 +1603,18 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio,
 			continue;
 
 		if (first_clone) {
+			struct md_bitmap_stats stats;
+			int err = md_bitmap_get_stats(bitmap, &stats);
+
 			/* do behind I/O ?
 			 * Not if there are too many, or cannot
 			 * allocate memory, or a reader on WriteMostly
 			 * is waiting for behind writes to flush */
-			if (bitmap && write_behind &&
-			    (atomic_read(&bitmap->behind_writes)
-			     < mddev->bitmap_info.max_write_behind) &&
-			    !waitqueue_active(&bitmap->behind_wait)) {
+			if (!err && write_behind &&
+			    stats.behind_writes <
+			    mddev->bitmap_info.max_write_behind &&
+			    !stats.behind_wait)
 				alloc_behind_master_bio(r1_bio, bio);
-			}
 
 			md_bitmap_startwrite(bitmap, r1_bio->sector, r1_bio->sectors,
 					     test_bit(R1BIO_BehindIO, &r1_bio->state));
-- 
2.39.2