libxfs: pack the agfl header structure so XFS_AGFL_SIZE is correct
authorDarrick J. Wong <darrick.wong@oracle.com>
Mon, 4 Jan 2016 05:13:21 +0000 (16:13 +1100)
committerDave Chinner <david@fromorbit.com>
Mon, 4 Jan 2016 05:13:21 +0000 (16:13 +1100)
commit96f859d52bcb1c6ea6f3388d39862bf7143e2f30
tree0f70d2c8cd62cd3a2d947a4ee002aa4cac9414fe
parent6d3eb1eca0e35cc1c0c80eacb7e7fe23c0dbfb07
libxfs: pack the agfl header structure so XFS_AGFL_SIZE is correct

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.

cc: <stable@vger.kernel.org> # 3.10 - 4.4
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>
fs/xfs/libxfs/xfs_format.h