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Date: Tue, 27 Apr 2010 14:17:45 +0800
From: Tao Ma <tao.ma@...cle.com>
To: linux-kernel@...r.kernel.org
Cc: Tao Ma <tao.ma@...cle.com>, xfs@....sgi.com,
Eric Sandeen <sandeen@...hat.com>,
Christoph Hellwig <hch@....de>, Alex Elder <aelder@....com>
Subject: [PATCH] XFS: Let the broken fiemap work in query mode.
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, we can't find a really suitable number to
set bmv_count now in xfs_vn_fiemap. Since we really have no idea of how
much extents the file has, a big number may cause ENOMEM, while a small
one will mask the real extent no.
So this patch try to resolve this problem by adding a temporary getbmapx
in xfs_getbmap. If the caller didn't give bmv_count, we don't allocate
the "out" either. Instead, every time we want to use 'out', use '&tmp'
instead.
I know this solution is a bit ugly, but I can't find a way to resolve
this issue while not changing the codes too much. So any good suggestion
is welcomed.
Cc: Eric Sandeen <sandeen@...hat.com>
Cc: Christoph Hellwig <hch@....de>
Cc: Alex Elder <aelder@....com>
Signed-off-by: Tao Ma <tao.ma@...cle.com>
---
fs/xfs/xfs_bmap.c | 47 +++++++++++++++++++++++++++++------------------
1 files changed, 29 insertions(+), 18 deletions(-)
diff --git a/fs/xfs/xfs_bmap.c b/fs/xfs/xfs_bmap.c
index 98251cd..654d9cf 100644
--- a/fs/xfs/xfs_bmap.c
+++ b/fs/xfs/xfs_bmap.c
@@ -5557,13 +5557,14 @@ xfs_getbmap(
int nexleft; /* # of user extents left */
int subnex; /* # of bmapi's can do */
int nmap; /* number of map entries */
- struct getbmapx *out; /* output structure */
+ struct getbmapx *out = NULL; /* output structure */
int whichfork; /* data or attr fork */
int prealloced; /* this is a file with
* preallocated data space */
int iflags; /* interface flags */
int bmapi_flags; /* flags for xfs_bmapi */
int cur_ext = 0;
+ struct getbmapx tmp, *bmap;
mp = ip->i_mount;
iflags = bmv->bmv_iflags;
@@ -5635,16 +5636,20 @@ xfs_getbmap(
}
nex = bmv->bmv_count - 1;
- if (nex <= 0)
+ if (nex < 0)
return XFS_ERROR(EINVAL);
bmvend = bmv->bmv_offset + bmv->bmv_length;
if (bmv->bmv_count > ULONG_MAX / sizeof(struct getbmapx))
return XFS_ERROR(ENOMEM);
- out = kmem_zalloc(bmv->bmv_count * sizeof(struct getbmapx), KM_MAYFAIL);
- if (!out)
- return XFS_ERROR(ENOMEM);
+ if (nex) {
+ out = kmem_zalloc(bmv->bmv_count * sizeof(struct getbmapx),
+ KM_MAYFAIL);
+ if (!out)
+ return XFS_ERROR(ENOMEM);
+ } else
+ nex = MAXEXTNUM;
xfs_ilock(ip, XFS_IOLOCK_SHARED);
if (whichfork == XFS_DATA_FORK && !(iflags & BMV_IF_DELALLOC)) {
@@ -5700,35 +5705,37 @@ xfs_getbmap(
ASSERT(nmap <= subnex);
for (i = 0; i < nmap && nexleft && bmv->bmv_length; i++) {
- out[cur_ext].bmv_oflags = 0;
+ if (out)
+ bmap = &out[cur_ext];
+ else
+ bmap = &tmp;
+ bmap->bmv_oflags = 0;
if (map[i].br_state == XFS_EXT_UNWRITTEN)
- out[cur_ext].bmv_oflags |= BMV_OF_PREALLOC;
+ bmap->bmv_oflags |= BMV_OF_PREALLOC;
else if (map[i].br_startblock == DELAYSTARTBLOCK)
- out[cur_ext].bmv_oflags |= BMV_OF_DELALLOC;
- out[cur_ext].bmv_offset =
+ bmap->bmv_oflags |= BMV_OF_DELALLOC;
+ bmap->bmv_offset =
XFS_FSB_TO_BB(mp, map[i].br_startoff);
- out[cur_ext].bmv_length =
+ bmap->bmv_length =
XFS_FSB_TO_BB(mp, map[i].br_blockcount);
- out[cur_ext].bmv_unused1 = 0;
- out[cur_ext].bmv_unused2 = 0;
+ bmap->bmv_unused1 = 0;
+ bmap->bmv_unused2 = 0;
ASSERT(((iflags & BMV_IF_DELALLOC) != 0) ||
(map[i].br_startblock != DELAYSTARTBLOCK));
if (map[i].br_startblock == HOLESTARTBLOCK &&
whichfork == XFS_ATTR_FORK) {
/* came to the end of attribute fork */
- out[cur_ext].bmv_oflags |= BMV_OF_LAST;
+ bmap->bmv_oflags |= BMV_OF_LAST;
goto out_free_map;
}
- if (!xfs_getbmapx_fix_eof_hole(ip, &out[cur_ext],
+ if (!xfs_getbmapx_fix_eof_hole(ip, bmap,
prealloced, bmvend,
map[i].br_startblock))
goto out_free_map;
nexleft--;
- bmv->bmv_offset =
- out[cur_ext].bmv_offset +
- out[cur_ext].bmv_length;
+ bmv->bmv_offset = bmap->bmv_offset + bmap->bmv_length;
bmv->bmv_length =
max_t(__int64_t, 0, bmvend - bmv->bmv_offset);
bmv->bmv_entries++;
@@ -5746,8 +5753,12 @@ xfs_getbmap(
for (i = 0; i < cur_ext; i++) {
int full = 0; /* user array is full */
+ if (out)
+ bmap = &out[i];
+ else
+ bmap = &tmp;
/* format results & advance arg */
- error = formatter(&arg, &out[i], &full);
+ error = formatter(&arg, bmap, &full);
if (error || full)
break;
}
--
1.6.3.3.334.g916e1.dirty
--
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