2 files changed, 22 insertions, 1 deletions

diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index 11108165e264..059704fbb753 100644
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -1160,6 +1160,22 @@ int bitmap_startwrite(struct bitmap *bitmap, sector_t offset, unsigned long sect
                         return 0;
                 }
 
+                if (unlikely((*bmc & COUNTER_MAX) == COUNTER_MAX)) {
+                        DEFINE_WAIT(__wait);
+                        /* note that it is safe to do the prepare_to_wait
+                         * after the test as long as we do it before dropping
+                         * the spinlock.
+                         */
+                        prepare_to_wait(&bitmap->overflow_wait, &__wait,
+                                        TASK_UNINTERRUPTIBLE);
+                        spin_unlock_irq(&bitmap->lock);
+                        bitmap->mddev->queue
+                                ->unplug_fn(bitmap->mddev->queue);
+                        schedule();
+                        finish_wait(&bitmap->overflow_wait, &__wait);
+                        continue;
+                }
+
                 switch(*bmc) {
                 case 0:
                         bitmap_file_set_bit(bitmap, offset);
@@ -1169,7 +1185,7 @@ int bitmap_startwrite(struct bitmap *bitmap, sector_t offset, unsigned long sect
                 case 1:
                         *bmc = 2;
                 }
-                BUG_ON((*bmc & COUNTER_MAX) == COUNTER_MAX);
+
                 (*bmc)++;
 
                 spin_unlock_irq(&bitmap->lock);
@@ -1207,6 +1223,9 @@ void bitmap_endwrite(struct bitmap *bitmap, sector_t offset, unsigned long secto
                 if (!success && ! (*bmc & NEEDED_MASK))
                         *bmc |= NEEDED_MASK;
 
+                if ((*bmc & COUNTER_MAX) == COUNTER_MAX)
+                        wake_up(&bitmap->overflow_wait);
+
                 (*bmc)--;
                 if (*bmc <= 2) {
                         set_page_attr(bitmap,
@@ -1431,6 +1450,7 @@ int bitmap_create(mddev_t *mddev)
         spin_lock_init(&bitmap->lock);
         atomic_set(&bitmap->pending_writes, 0);
         init_waitqueue_head(&bitmap->write_wait);
+        init_waitqueue_head(&bitmap->overflow_wait);
 
         bitmap->mddev = mddev;
 
diff --git a/include/linux/raid/bitmap.h b/include/linux/raid/bitmap.h
index ebd42a3710b4..6db9a4c15355 100644
--- a/include/linux/raid/bitmap.h
+++ b/include/linux/raid/bitmap.h
@@ -247,6 +247,7 @@ struct bitmap {
 
         atomic_t pending_writes; /* pending writes to the bitmap file */
         wait_queue_head_t write_wait;
+        wait_queue_head_t overflow_wait;
 
 };