[PATCH v2] XFS: Let the broken fiemap work in query mode.

From: Tao Ma
Date: Tue Apr 27 2010 - 22:25:33 EST


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 97db39a1f6f69e906e98118392400de5217aa33a 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@xxxxxxxxxxxxx> for the suggestion.

Cc: Dave Chinner <david@xxxxxxxxxxxxx>
Cc: Eric Sandeen <sandeen@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Alex Elder <aelder@xxxxxxx>
Signed-off-by: Tao Ma <tao.ma@xxxxxxxxxx>
---
fs/xfs/linux-2.6/xfs_iops.c | 5 ++++-
1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/fs/xfs/linux-2.6/xfs_iops.c b/fs/xfs/linux-2.6/xfs_iops.c
index 2259460..24ccad9 100644
--- a/fs/xfs/linux-2.6/xfs_iops.c
+++ b/fs/xfs/linux-2.6/xfs_iops.c
@@ -662,7 +662,10 @@ 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(bm.bmv_count,
+ (__s32)(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;
--
1.6.3.3.334.g916e1.dirty

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