1 files changed, 28 insertions, 17 deletions

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 0864da7d9adc..5599dcbd2991 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -1366,7 +1366,8 @@ static void raid1_read_request(struct mddev *mddev, struct bio *bio,
 				    (unsigned long long)r1_bio->sector,
 				    mirror->rdev->bdev);
 
-	if (test_bit(WriteMostly, &mirror->rdev->flags)) {
+	if (test_bit(WriteMostly, &mirror->rdev->flags) &&
+	    md_bitmap_enabled(mddev, false)) {
 		/*
 		 * Reading from a write-mostly device must take care not to
 		 * over-take any writes that are 'behind'
@@ -1452,6 +1453,30 @@ retry:
 	return true;
 }
 
+static void raid1_start_write_behind(struct mddev *mddev, struct r1bio *r1_bio,
+				     struct bio *bio)
+{
+	unsigned long max_write_behind = mddev->bitmap_info.max_write_behind;
+	struct md_bitmap_stats stats;
+	int err;
+
+	/* behind write rely on bitmap, see bitmap_operations */
+	if (!md_bitmap_enabled(mddev, false))
+		return;
+
+	err = mddev->bitmap_ops->get_stats(mddev->bitmap, &stats);
+	if (err)
+		return;
+
+	/* Don't do behind IO if reader is waiting, or there are too many. */
+	if (!stats.behind_wait && stats.behind_writes < max_write_behind)
+		alloc_behind_master_bio(r1_bio, bio);
+
+	if (test_bit(R1BIO_BehindIO, &r1_bio->state))
+		mddev->bitmap_ops->start_behind_write(mddev);
+
+}
+
 static void raid1_write_request(struct mddev *mddev, struct bio *bio,
 				int max_write_sectors)
 {
@@ -1612,22 +1637,8 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio,
 			continue;
 
 		if (first_clone) {
-			unsigned long max_write_behind =
-				mddev->bitmap_info.max_write_behind;
-			struct md_bitmap_stats stats;
-			int err;
-
-			/* do behind I/O ?
-			 * Not if there are too many, or cannot
-			 * allocate memory, or a reader on WriteMostly
-			 * is waiting for behind writes to flush */
-			err = mddev->bitmap_ops->get_stats(mddev->bitmap, &stats);
-			if (!err && write_behind && !stats.behind_wait &&
-			    stats.behind_writes < max_write_behind)
-				alloc_behind_master_bio(r1_bio, bio);
-
-			if (test_bit(R1BIO_BehindIO, &r1_bio->state))
-				mddev->bitmap_ops->start_behind_write(mddev);
+			if (write_behind)
+				raid1_start_write_behind(mddev, r1_bio, bio);
 			first_clone = 0;
 		}