--- drivers/md/bitmap.c

+++ drivers/md/bitmap.c

@@ -1317,7 +1317,8 @@ void bitmap_endwrite(struct bitmap *bitm

{

if (!bitmap) return;

if (behind) {

- atomic_dec(&bitmap->behind_writes);

+ if (atomic_dec_and_test(&bitmap->behind_writes))

+ wake_up(&bitmap->behind_wait);

PRINTK(KERN_DEBUG "dec write-behind count %d/%d\n",

atomic_read(&bitmap->behind_writes), bitmap->max_write_behind);

}

@@ -1629,6 +1630,7 @@ int bitmap_create(mddev_t *mddev)

atomic_set(&bitmap->pending_writes, 0);

init_waitqueue_head(&bitmap->write_wait);

init_waitqueue_head(&bitmap->overflow_wait);

+ init_waitqueue_head(&bitmap->behind_wait);

bitmap->mddev = mddev;