vfs: Add BUG_ON for delayed and unwritten flags in submit_bh()

The BH_Delay and BH_Unwritten flags should never leak out to
submit_bh().  So add some BUG_ON() checks to submit_bh so we can get a
stack trace and determine how and why this might have happened.

(Note that only XFS and ext4 use these buffer head flags, and XFS does
not use submit_bh().  So this patch should only modify behavior for
ext4.)

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: linux-fsdevel@vger.kernel.org

diff --git a/fs/buffer.c b/fs/buffer.c
index aed2977..ad01129 100644 (file)
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -2933,6 +2933,8 @@ int submit_bh(int rw, struct buffer_head * bh)
        BUG_ON(!buffer_locked(bh));
        BUG_ON(!buffer_mapped(bh));
        BUG_ON(!bh->b_end_io);
+       BUG_ON(buffer_delay(bh));
+       BUG_ON(buffer_unwritten(bh));
 
        /*
         * Mask in barrier bit for a write (could be either a WRITE or a