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xfs: Make fiemap work in query mode.

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According to Documentation/filesystems/fiemap.txt, If fm_extent_count
is zero, then the fm_extents[] array is ignored (no extents will be
returned), and the fm_mapped_extents count will hold the number of
extents needed.

But as the commit 97db39a1f6 has changed
bmv_count to the caller's input buffer, this number query function can't
work any more. As this commit is written to change bmv_count from
MAXEXTNUM because of ENOMEM.

This patch just try to  set bm.bmv_count to something sane.
Thanks to Dave Chinner <david@fromorbit.com> for the suggestion.

Cc: Eric Sandeen <sandeen@redhat.com>
Cc: Alex Elder <aelder@sgi.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Tao Ma <tao.ma@oracle.com>
This commit is contained in:
Tao Ma 2010-04-29 15:13:56 +10:00 committed by Alex Elder
parent 48389ef175
commit 2d1ff3c75a
1 changed files with 4 additions and 1 deletions
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5
fs/xfs/linux-2.6/xfs_iops.c
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@ -673,7 +673,10 @@ xfs_vn_fiemap(
bm.bmv_length = BTOBB(length);
/* We add one because in getbmap world count includes the header */
bm.bmv_count = fieinfo->fi_extents_max + 1;
bm.bmv_count = !fieinfo->fi_extents_max ? MAXEXTNUM :
fieinfo->fi_extents_max + 1;
bm.bmv_count = min_t(__s32, bm.bmv_count,
(PAGE_SIZE * 16 / sizeof(struct getbmapx)));
bm.bmv_iflags = BMV_IF_PREALLOC;
if (fieinfo->fi_flags & FIEMAP_FLAG_XATTR)
bm.bmv_iflags |= BMV_IF_ATTRFORK;