xfs: flush dirty data and drain directios before scrubbing cow fork

When we're scrubbing the COW fork, we need to take MMAPLOCK_EXCL to
prevent page_mkwrite from modifying any inode state.  The ILOCK should
suffice to avoid confusing online fsck, but let's take the same locks
that we do everywhere else.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

fs/xfs/scrub/bmap.c

@@ -42,12 +42,12 @@ xchk_setup_inode_bmap(
 	xfs_ilock(sc->ip, XFS_IOLOCK_EXCL);
 
 	/*
-	 * We don't want any ephemeral data fork updates sitting around
+	 * We don't want any ephemeral data/cow fork updates sitting around
 	 * while we inspect block mappings, so wait for directio to finish
 	 * and flush dirty data if we have delalloc reservations.
 	 */
 	if (S_ISREG(VFS_I(sc->ip)->i_mode) &&
-	    sc->sm->sm_type == XFS_SCRUB_TYPE_BMBTD) {
+	    sc->sm->sm_type != XFS_SCRUB_TYPE_BMBTA) {
 		struct address_space	*mapping = VFS_I(sc->ip)->i_mapping;
 
 		sc->ilock_flags |= XFS_MMAPLOCK_EXCL;