[XFS] Ensure "both" features2 slots are consistent

Since older kernels may look in the sb_bad_features2 slot for flags,
rather than zeroing it out on fixup, we should make it equal to the
sb_features2 value.

Also, if the ATTR2 flag was not found prior to features2 fixup, it was not
set in the mount flags, so re-check after the fixup so that the current
session will use the feature.

Also fix up the comments to reflect these changes.

SGI-PV: 980085
SGI-Modid: xfs-linux-melb:xfs-kern:30778a

Signed-off-by: Eric Sandeen <sandeen@sandeen.net>
Signed-off-by: David Chinner <dgc@sgi.com>
Signed-off-by: Lachlan McIlroy <lachlan@sgi.com>

1 files changed, 4 insertions, 3 deletions

diff --git a/fs/xfs/xfs_sb.h b/fs/xfs/xfs_sb.h
index b1a83f8ec044..d904efe7f871 100644
--- a/fs/xfs/xfs_sb.h
+++ b/fs/xfs/xfs_sb.h
@@ -320,11 +320,12 @@ static inline int xfs_sb_good_version(xfs_sb_t *sbp)
 #endif /* __KERNEL__ */
 
 /*
- * Detect a bad features2 field
+ * Detect a mismatched features2 field.  Older kernels read/wrote
+ * this into the wrong slot, so to be safe we keep them in sync.
  */
-static inline int xfs_sb_has_bad_features2(xfs_sb_t *sbp)
+static inline int xfs_sb_has_mismatched_features2(xfs_sb_t *sbp)
 {
-        return (sbp->sb_bad_features2 != 0);
+        return (sbp->sb_bad_features2 != sbp->sb_features2);
 }
 
 static inline unsigned xfs_sb_version_tonew(unsigned v)