xfs: kill unnecessary firstused overflow check on attr3 leaf removal

xfs_attr3_leaf_remove() removes an attribute from an attr leaf block. If
the attribute nameval data happens to be at the start of the nameval
region, a new start offset (firstused) for the region is calculated
(since the region grows from the tail of the block to the start). Once
the new firstused is calculated, it is checked for zero in an apparent
overflow check.

Now that the in-core firstused is 32-bit, overflow is not possible and
this check can be removed. Since the purpose for this check is not
documented and appears to exist since the port to Linux, be conservative
and replace it with an assert.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

diff --git a/fs/xfs/libxfs/xfs_attr_leaf.c b/fs/xfs/libxfs/xfs_attr_leaf.c
index 149ef3f6673519f12c2f1d4333aa972a61aa5c87..04e79d57bca600b4a21cd0a2a936639d9556e6c8 100644 (file)
--- a/fs/xfs/libxfs/xfs_attr_leaf.c
+++ b/fs/xfs/libxfs/xfs_attr_leaf.c
@@ -1996,8 +1996,7 @@ xfs_attr3_leaf_remove(
                                tmp = be16_to_cpu(entry->nameidx);
                }
                ichdr.firstused = tmp;
-               if (!ichdr.firstused)
-                       ichdr.firstused = tmp - XFS_ATTR_LEAF_NAME_ALIGN;
+               ASSERT(ichdr.firstused != 0);
        } else {
                ichdr.holes = 1;        /* mark as needing compaction */
        }