[ 13/75] md/bitmap: prevent bitmap_daemon_work running while initialising bitmap

3.3-stable review patch.  If anyone has any objections, please let me know.

------------------

From: NeilBrown <redacted>

commit afbaa90b80b1ec66e5137cc3824746bfdf559b18 upstream.

If a bitmap is added while the array is active, it is possible
for bitmap_daemon_work to run while the bitmap is being
initialised.
This is particularly a problem if bitmap_daemon_work sees
bitmap->filemap as non-NULL before it has been filled in properly.
So hold bitmap_info.mutex while filling in ->filemap
to prevent problems.

This patch is suitable for any -stable kernel, though it might not
apply cleanly before about 3.1.

Signed-off-by: NeilBrown <redacted>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/md/bitmap.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c

@@ -1819,7 +1819,9 @@ int bitmap_load(struct mddev *mddev)
 		 * re-add of a missing device */
 		start = mddev->recovery_cp;
 
+	mutex_lock(&mddev->bitmap_info.mutex);
 	err = bitmap_init_from_disk(bitmap, start);
+	mutex_unlock(&mddev->bitmap_info.mutex);
 
 	if (err)
 		goto out;