On Fri, Jul 23, 2010 at 12:49:38PM +1000, Dave Chinner wrote:
> On Thu, Jul 22, 2010 at 02:05:26PM -0500, Eric Sandeen wrote:
> > This replicates file corruption we've seen with qemu-kvm when
> > we use if=virtio,cache=none,aio=native for IO to a sparse
> > ext4- or xfs-hosted file, and the partitions/filesystems
> > within that file image are not block-aligned. (think sector
> > 63 here...) This results in AIO IOs not aligned to the
> > filesystem blocks.
> >
> > This test modifies aiodio_sparse2.c to add an option to start
> > the file IO at an offset.
> >
> > When we do 4k writes to a 16k file in 2 threads, starting
> > at offset 512, we get 0s interspersed in the file where they
> > should not be:
> >
> > 00000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
> > *
> > 00000200 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 |................|
> > *
> > 00001000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
> > *
> > 00001200 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 |................|
> > ....
> >
> > Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxxx>
>
> looks good - it needs to remove the $TEST_DIR/aiodio_sparse file
> before the test starts, though, so that repeated tests fail
> correctly. Otherwise:
>
> Reviewed-by: Dave Chinner <dchinner@xxxxxxxxxx>
>
> Also, Eric, can you run this proof-of-concept test branch (on top of
> the current XFS for-2.6.36 branch) and see if QEMU is happy with it?
> It passes this test on my machine....
>
> The following changes since commit d2ec2c790b3994bf0c4381cacc489b514705887c:
>
> xfs: clean up xfs_bmap_get_bp (2010-07-22 12:52:08 +1000)
>
> are available in the git repository at:
> git://git.kernel.org/pub/scm/linux/kernel/git/dgc/xfsdev aio-unaligned
I just pushed another patch onto this series that will makes test
240 pass reliably here rather than hanging. It's all a bit messy,
but it does serve to illustrate the problem and a potential avenue
to prevent it....
Dave Chinner (5):
Merge branch 'master' into working
Merge branch 'for-2.6.36' into working
fs: get_blocks needs an unaligned mapping flag
xfs: serialise unaligned direct IO into unwritten extents
xfs: wait on IO completion inside an IO context
fs/buffer.c | 17 ++++----
fs/direct-io.c | 25 ++++++++++-
fs/ioctl.c | 2 +-
fs/mpage.c | 6 ++-
fs/xfs/linux-2.6/xfs_aops.c | 95 ++++++++++++++++++++++++++++++++++++++-----
fs/xfs/xfs_inode.h | 13 +++---
include/linux/fs.h | 10 ++++-
7 files changed, 136 insertions(+), 32 deletions(-)
--
Dave Chinner
david@xxxxxxxxxxxxx
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