[XFS] Ensure "both" features2 slots are consistent

[sfrench/cifs-2.6.git] / fs / xfs / xfs_mount.c

diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index 4e93c02faf24bb2e960b4c8a0395fa660d1ac347..8ed164eb9544e4dcd5618eff7d3c9807f659ca26 100644 (file)
--- 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(