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| author | Eric Sandeen <sandeen@sandeen.net> | 2014-10-02 09:24:11 +1000 |
|---|---|---|
| committer | Dave Chinner <david@fromorbit.com> | 2014-10-02 09:24:11 +1000 |
| commit | 04dd1a0d4b17a71220eae4fb313218f15a49bcdd (patch) | |
| tree | b1947cec8a738c5d711b3c6416399080ec145443 /fs/xfs | |
| parent | 6ee49a20c13b4b4e79a3bba406df8106cff284a1 (diff) | |
| download | lwn-04dd1a0d4b17a71220eae4fb313218f15a49bcdd.tar.gz lwn-04dd1a0d4b17a71220eae4fb313218f15a49bcdd.zip | |
xfs: fix crc field handling in xfs_sb_to/from_disk
I discovered this in userspace, but the same change applies
to the kernel.
If we xfs_mdrestore an image from a non-crc filesystem, lo
and behold the restored image has gained a CRC:
# db/xfs_metadump.sh -o /dev/sdc1 - | xfs_mdrestore - test.img
# xfs_db -c "sb 0" -c "p crc" /dev/sdc1
crc = 0 (correct)
# xfs_db -c "sb 0" -c "p crc" test.img
crc = 0xb6f8d6a0 (correct)
This is because xfs_sb_from_disk doesn't fill in sb_crc,
but xfs_sb_to_disk(XFS_SB_ALL_BITS) does write the in-memory
CRC to disk - so we get uninitialized memory on disk.
Fix this by always initializing sb_crc to 0 when we read
the superblock, and masking out the CRC bit from ALL_BITS
when we write it.
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <david@fromorbit.com>
Diffstat (limited to 'fs/xfs')
| -rw-r--r-- | fs/xfs/libxfs/xfs_sb.c | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/fs/xfs/libxfs/xfs_sb.c b/fs/xfs/libxfs/xfs_sb.c index 8426e5e2682e..5f902fa7913f 100644 --- a/fs/xfs/libxfs/xfs_sb.c +++ b/fs/xfs/libxfs/xfs_sb.c @@ -445,6 +445,8 @@ __xfs_sb_from_disk( to->sb_features_incompat = be32_to_cpu(from->sb_features_incompat); to->sb_features_log_incompat = be32_to_cpu(from->sb_features_log_incompat); + /* crc is only used on disk, not in memory; just init to 0 here. */ + to->sb_crc = 0; to->sb_pad = 0; to->sb_pquotino = be64_to_cpu(from->sb_pquotino); to->sb_lsn = be64_to_cpu(from->sb_lsn); @@ -550,6 +552,9 @@ xfs_sb_to_disk( if (!fields) return; + /* We should never write the crc here, it's updated in the IO path */ + fields &= ~XFS_SB_CRC; + xfs_sb_quota_to_disk(to, from, &fields); while (fields) { f = (xfs_sb_field_t)xfs_lowbit64((__uint64_t)fields); |