fs: fix iomap_bmap position calculation
authorEric Sandeen <sandeen@redhat.com>
Thu, 2 Aug 2018 20:09:27 +0000 (13:09 -0700)
committerDarrick J. Wong <darrick.wong@oracle.com>
Thu, 2 Aug 2018 20:09:27 +0000 (13:09 -0700)
commit79b3dbe4adb3420e74cf755b4beb5d2b43d5928d
treed49aae11f8919138e3a43ef830e6bd68fd4e89bf
parentd4a34e16555708bab5b67e679a95f055d8ef9882
fs: fix iomap_bmap position calculation

The position calculation in iomap_bmap() shifts bno the wrong way,
so we don't progress properly and end up re-mapping block zero
over and over, yielding an unchanging physical block range as the
logical block advances:

# filefrag -Be file
 ext:   logical_offset:     physical_offset: length:   expected: flags:
   0:      0..       0:      21..        21:      1:             merged
   1:      1..       1:      21..        21:      1:         22: merged
Discontinuity: Block 1 is at 21 (was 22)
   2:      2..       2:      21..        21:      1:         22: merged
Discontinuity: Block 2 is at 21 (was 22)
   3:      3..       3:      21..        21:      1:         22: merged

This breaks the FIBMAP interface for anyone using it (XFS), which
in turn breaks LILO, zipl, etc.

Bug-actually-spotted-by: Darrick J. Wong <darrick.wong@oracle.com>
Fixes: 89eb1906a953 ("iomap: add an iomap-based bmap implementation")
Cc: stable@vger.kernel.org
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
fs/iomap.c