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libxfs: pack the agfl header structure so XFS_AGFL_SIZE is correct

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commit 96f859d52bcb1c6ea6f3388d39862bf7143e2f30 upstream.

Because struct xfs_agfl is 36 bytes long and has a 64-bit integer
inside it, gcc will quietly round the structure size up to the nearest
64 bits -- in this case, 40 bytes.  This results in the XFS_AGFL_SIZE
macro returning incorrect results for v5 filesystems on 64-bit
machines (118 items instead of 119).  As a result, a 32-bit xfs_repair
will see garbage in AGFL item 119 and complain.

Therefore, tell gcc not to pad the structure so that the AGFL size
calculation is correct.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Darrick J. Wong 2016-01-04 16:13:21 +11:00 • committed by Greg Kroah-Hartman
parent 8373f6590f
commit 888959f2fd
1 changed files with 1 additions and 1 deletions
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2
fs/xfs/libxfs/xfs_format.h
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@ -786,7 +786,7 @@ typedef struct xfs_agfl {
__be64 agfl_lsn;
__be32 agfl_crc;
__be32 agfl_bno[]; /* actually XFS_AGFL_SIZE(mp) */
} xfs_agfl_t;
} __attribute__((packed)) xfs_agfl_t;
#define XFS_AGFL_CRC_OFF offsetof(struct xfs_agfl, agfl_crc)