xfs: sanitise sb_bad_features2 handling
We currently have to ensure that every time we update sb_features2
that we update sb_bad_features2. Now that we log and format the
superblock in it's entirety we actually don't have to care because
we can simply update the sb_bad_features2 when we format it into the
buffer. This removes the need for anything but the mount and
superblock formatting code to care about sb_bad_features2, and
hence removes the possibility that we forget to update bad_features2
when necessary in the future.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index 5ef9aa2..4fa80e6 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -640,25 +640,24 @@
xfs_sb_mount_common(mp, sbp);
/*
- * 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.
+ * 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.
*
* 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 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. The
+ * superblock writeback code ensures the new sb_features2 is copied to
+ * sb_bad_features2 before it is logged or written to disk.
*/
if (xfs_sb_has_mismatched_features2(sbp)) {
xfs_warn(mp, "correcting sb_features alignment problem");
sbp->sb_features2 |= sbp->sb_bad_features2;
- sbp->sb_bad_features2 = sbp->sb_features2;
mp->m_update_sb = true;
/*