md/bitmap: clean up plugging calls.

1/ use md_unplug in bitmap.c as we will soon be using bitmaps under
  arrays with no queue attached.

2/ Don't bother plugging the queue when we set a bit in the bitmap.
   The reason for this was to encourage as many bits as possible to
   get set before we unplug and write stuff out.
   However every personality already plugs the queue after
   bitmap_startwrite either directly (raid1/raid10) or be setting
   STRIPE_BIT_DELAY which causes the queue to be plugged later
   (raid5).

Signed-off-by: NeilBrown <neilb@suse.de>

1 files changed, 1 insertions, 0 deletions

diff --git a/drivers/md/md.h b/drivers/md/md.h
index 209993207a55..0a850780b5d1 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -509,6 +509,7 @@ extern int md_integrity_register(mddev_t *mddev);
 extern void md_integrity_add_rdev(mdk_rdev_t *rdev, mddev_t *mddev);
 extern int strict_strtoul_scaled(const char *cp, unsigned long *res, int scale);
 extern void restore_bitmap_write_access(struct file *file);
+extern void md_unplug(mddev_t *mddev);
 
 extern void mddev_init(mddev_t *mddev);
 extern int md_run(mddev_t *mddev);