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authorEric Sandeen <sandeen@sandeen.net>2008-04-10 12:19:34 +1000
committerLachlan McIlroy <lachlan@redback.melbourne.sgi.com>2008-04-10 16:25:26 +1000
commite6957ea48429aeda4f5d51af4238231d44b0dc4a (patch)
tree860c95c0e9446191262bb44ad436d38afb8cb7d6
parentee1c090825bf2f1cb9712489c234eabf69a9a78f (diff)
[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>
-rw-r--r--fs/xfs/xfs_mount.c37
-rw-r--r--fs/xfs/xfs_sb.h7
2 files changed, 29 insertions, 15 deletions
diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index 4e93c02faf2..8ed164eb954 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -972,23 +972,35 @@ xfs_mountfs(
xfs_mount_common(mp, sbp);
/*
- * Check for a bad features2 field alignment. This happened on
- * some platforms due to xfs_sb_t not being 64bit size aligned
- * when sb_features was added and hence the compiler put it in
- * the wrong place.
+ * Check for a mismatched features2 values. Older kernels
+ * read & wrote into the wrong sb offset for sb_features2
+ * on some platforms due to xfs_sb_t not being 64bit size aligned
+ * when sb_features2 was added, which made older superblock
+ * reading/writing routines swap it as a 64-bit value.
*
- * If we detect a bad field, we or the set bits into the existing
- * features2 field in case it has already been modified and we
- * don't want to lose any features. Zero the bad one and mark
- * the two fields as needing updates once the transaction subsystem
- * is online.
+ * For backwards compatibility, we make both slots equal.
+ *
+ * If we detect a mismatched field, we OR the set bits into the
+ * existing features2 field in case it has already been modified; we
+ * don't want to lose any features. We then update the bad location
+ * with the ORed value so that older kernels will see any features2
+ * flags, and mark the two fields as needing updates once the
+ * transaction subsystem is online.
*/
- if (xfs_sb_has_bad_features2(sbp)) {
+ if (xfs_sb_has_mismatched_features2(sbp)) {
cmn_err(CE_WARN,
"XFS: correcting sb_features alignment problem");
sbp->sb_features2 |= sbp->sb_bad_features2;
- sbp->sb_bad_features2 = 0;
+ sbp->sb_bad_features2 = sbp->sb_features2;
update_flags |= XFS_SB_FEATURES2 | XFS_SB_BAD_FEATURES2;
+
+ /*
+ * Re-check for ATTR2 in case it was found in bad_features2
+ * slot.
+ */
+ if (xfs_sb_version_hasattr2(&mp->m_sb))
+ mp->m_flags |= XFS_MOUNT_ATTR2;
+
}
/*
@@ -1896,7 +1908,8 @@ xfs_uuid_unmount(
/*
* Used to log changes to the superblock unit and width fields which could
- * be altered by the mount options. Only the first superblock is updated.
+ * be altered by the mount options, as well as any potential sb_features2
+ * fixup. Only the first superblock is updated.
*/
STATIC void
xfs_mount_log_sb(
diff --git a/fs/xfs/xfs_sb.h b/fs/xfs/xfs_sb.h
index b1a83f8ec04..d904efe7f87 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)