Messages in this thread | | | From | Calvin Owens <> | Subject | Re: [PATCH v2] xfs: Honor FALLOC_FL_KEEP_SIZE when punching ends of files | Date | Tue, 21 Mar 2017 12:13:21 -0700 |
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On 03/21/2017 04:39 AM, Brian Foster wrote: > On Sun, Mar 19, 2017 at 09:54:51PM -0700, Calvin Owens wrote: >> When punching past EOF on XFS, fallocate(mode=PUNCH_HOLE|KEEP_SIZE) will >> round the file size up to the nearest multiple of PAGE_SIZE: >> >> calvinow@vm-disks/generic-xfs-1 ~$ dd if=/dev/urandom of=test bs=2048 count=1 >> calvinow@vm-disks/generic-xfs-1 ~$ stat test >> Size: 2048 Blocks: 8 IO Block: 4096 regular file >> calvinow@vm-disks/generic-xfs-1 ~$ fallocate -n -l 2048 -o 2048 -p test >> calvinow@vm-disks/generic-xfs-1 ~$ stat test >> Size: 4096 Blocks: 8 IO Block: 4096 regular file >> >> Commit 3c2bdc912a1cc050 ("xfs: kill xfs_zero_remaining_bytes") replaced >> xfs_zero_remaining_bytes() with calls to iomap helpers. The new helpers >> don't enforce that [pos,offset) lies strictly on [0,i_size) when being >> called from xfs_free_file_space(), so by "leaking" these ranges into >> xfs_zero_range() we get this buggy behavior. >> >> Fix this by reintroducing the checks xfs_zero_remaining_bytes() did >> against i_size at the bottom of xfs_free_file_space(). >> >> Reported-by: Aaron Gao <gzh@fb.com> >> Fixes: 3c2bdc912a1cc050 ("xfs: kill xfs_zero_remaining_bytes") >> Cc: Christoph Hellwig <hch@lst.de> >> Cc: <stable@vger.kernel.org> # 4.8+ >> Signed-off-by: Calvin Owens <calvinowens@fb.com> >> --- >> fs/xfs/xfs_bmap_util.c | 11 +++++++++++ >> 1 file changed, 11 insertions(+) >> >> diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c >> index 8b75dce..0796ebc 100644 >> --- a/fs/xfs/xfs_bmap_util.c >> +++ b/fs/xfs/xfs_bmap_util.c >> @@ -1309,6 +1309,17 @@ xfs_free_file_space( >> } >> >> /* >> + * Avoid doing I/O beyond eof - it's not necessary >> + * since nothing can read beyond eof. The space will >> + * be zeroed when the file is extended anyway. >> + */ > > I'd suggest to update the comment below with this information and move > the following bits down below it as well.
Will do.
>> + if (offset >= XFS_ISIZE(ip)) >> + return 0; >> + >> + if ((offset + len) >= XFS_ISIZE(ip)) >> + len = XFS_ISIZE(ip) - offset - 1; >> + > > This looks like an off-by-one. Do you mean the following? > > if (offset + len > XFS_ISIZE(ip)) > len = XFS_ISIZE(ip) - offset;
It's not an off-by-one (it's self-consistent), but your way makes more sense, I'll fix it ;)
Thanks, Calvin
> Brian > >> + /* >> * Now that we've unmap all full blocks we'll have to zero out any >> * partial block at the beginning and/or end. xfs_zero_range is >> * smart enough to skip any holes, including those we just created. >> -- >> 2.9.3 >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-xfs" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html
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