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xfs: fix rounding error of fiemap length parameter

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The offset and length parameters are converted from bytes to basic
blocks by xfs_vn_fiemap(). The BTOBB() converter rounds the value up to
the nearest basic block. This leads to unexpected behavior when
unaligned offsets are provided to FIEMAP.

Fix the conversions of byte values to block values to cover the provided
offsets. Round down the start offset to the nearest basic block.
Calculate the end offset based on the provided values, round up and
calculate length based on the start block offset.

Reported-by: Chandan Rajendra <chandan@linux.vnet.ibm.com>
Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
This commit is contained in:
Brian Foster 2014-08-04 11:35:35 +10:00 committed by Dave Chinner
parent 2451337dd0
commit eedf32bfca
1 changed files with 2 additions and 2 deletions
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4
fs/xfs/xfs_iops.c
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@ -1055,12 +1055,12 @@ xfs_vn_fiemap(
return error;
/* Set up bmap header for xfs internal routine */
bm.bmv_offset = BTOBB(start);
bm.bmv_offset = BTOBBT(start);
/* Special case for whole file */
if (length == FIEMAP_MAX_OFFSET)
bm.bmv_length = -1LL;
else
bm.bmv_length = BTOBB(length);
bm.bmv_length = BTOBB(start + length) - bm.bmv_offset;
/* We add one because in getbmap world count includes the header */
bm.bmv_count = !fieinfo->fi_extents_max ? MAXEXTNUM :