From: Eric Sandeen <sandeen@sandeen.net>
Date: Wed, 1 Oct 2014 23:24:11 +0000 (+1000)
Subject: xfs: fix crc field handling in xfs_sb_to/from_disk
X-Git-Tag: fixes-against-v3.18-rc2~104^2^2~5
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=04dd1a0d4b17a71220eae4fb313218f15a49bcdd;p=pandora-kernel.git

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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