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>
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@ -445,6 +445,8 @@ __xfs_sb_from_disk(
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to->sb_features_incompat = be32_to_cpu(from->sb_features_incompat);
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to->sb_features_log_incompat =
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be32_to_cpu(from->sb_features_log_incompat);
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/* crc is only used on disk, not in memory; just init to 0 here. */
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to->sb_crc = 0;
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to->sb_pad = 0;
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to->sb_pquotino = be64_to_cpu(from->sb_pquotino);
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to->sb_lsn = be64_to_cpu(from->sb_lsn);
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@ -550,6 +552,9 @@ xfs_sb_to_disk(
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if (!fields)
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return;
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/* We should never write the crc here, it's updated in the IO path */
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fields &= ~XFS_SB_CRC;
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xfs_sb_quota_to_disk(to, from, &fields);
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while (fields) {
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f = (xfs_sb_field_t)xfs_lowbit64((__uint64_t)fields);
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