| Message ID | 19504ff40a16efff2e51d85388fce5be578edbc3.1489985397.git.calvinowens@fb.com (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
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. > + 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; 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 -- 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
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 -- 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
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. + */ + if (offset >= XFS_ISIZE(ip)) + return 0; + + if ((offset + len) >= XFS_ISIZE(ip)) + len = XFS_ISIZE(ip) - offset - 1; + + /* * 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.
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(+)