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xfs: sanitise sb_bad_features2 handling

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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>
This commit is contained in:
Dave Chinner
2015-01-22 09:10:33 +11:00
committed by Dave Chinner
parent 61e63ecb57
commit 074e427ba7
3 changed files with 25 additions and 20 deletions
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23
fs/xfs/xfs_mount.c
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@@ -640,25 +640,24 @@ xfs_mountfs(
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;
/*