From 04dd1a0d4b17a71220eae4fb313218f15a49bcdd Mon Sep 17 00:00:00 2001 From: Eric Sandeen Date: Thu, 2 Oct 2014 09:24:11 +1000 Subject: [PATCH] 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 Reviewed-by: Christoph Hellwig Signed-off-by: Dave Chinner --- fs/xfs/libxfs/xfs_sb.c | 5 +++++ 1 file changed, 5 insertions(+) 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);