xfs: reinitialize rm_flags when unpacking an offset into an rmap irec

In xfs_rmap_irec_offset_unpack, we should always clear the contents of
rm_flags before we begin unpacking the encoded (ondisk) offset into the
incore rm_offset and incore rm_flags fields.  Remove the open-coded
field zeroing as this encourages api misuse.
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

fs/xfs/libxfs/xfs_rmap.c

@@ -168,7 +168,6 @@ xfs_rmap_btrec_to_irec(
 	union xfs_btree_rec	*rec,
 	struct xfs_rmap_irec	*irec)
 {
-	irec->rm_flags = 0;
 	irec->rm_startblock = be32_to_cpu(rec->rmap.rm_startblock);
 	irec->rm_blockcount = be32_to_cpu(rec->rmap.rm_blockcount);
 	irec->rm_owner = be64_to_cpu(rec->rmap.rm_owner);

fs/xfs/libxfs/xfs_rmap.h

@@ -68,6 +68,7 @@ xfs_rmap_irec_offset_unpack(
 	if (offset & ~(XFS_RMAP_OFF_MASK | XFS_RMAP_OFF_FLAGS))
 		return -EFSCORRUPTED;
 	irec->rm_offset = XFS_RMAP_OFF(offset);
+	irec->rm_flags = 0;
 	if (offset & XFS_RMAP_OFF_ATTR_FORK)
 		irec->rm_flags |= XFS_RMAP_ATTR_FORK;
 	if (offset & XFS_RMAP_OFF_BMBT_BLOCK)