Re: [PATCH] fstests: btrfs/150 regression test for reading compressed data

Dave Chinner
2017-09-21T04:40:35Z

On Wed, Sep 20, 2017 at 05:52:43PM -0600, Liu Bo wrote:
> We had a bug in btrfs compression code which could end up with a
> kernel panic.
>
> This is adding a regression test for the bug and I've also sent a
> kernel patch to fix the bug.
>
> The patch is "Btrfs: fix kernel oops while reading compressed data".
>
> Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
> ---
> tests/btrfs/150 | 102 ++++++++++++++++++++++++++++++++++++++++++++++++++++
> tests/btrfs/150.out | 3 ++
> tests/btrfs/group | 1 +
> 3 files changed, 106 insertions(+)
> create mode 100755 tests/btrfs/150
> create mode 100644 tests/btrfs/150.out
>
> diff --git a/tests/btrfs/150 b/tests/btrfs/150
> new file mode 100755
> index 0000000..834be51
> --- /dev/null
> +++ b/tests/btrfs/150
> @@ -0,0 +1,102 @@
> +#! /bin/bash
> +# FS QA Test btrfs/150
> +#
> +# This is a regression test which ends up with a kernel oops in btrfs.

group += dangerous

> +# It occurs when btrfs's read repair happens while reading a compressed
> +# extent.
> +# The patch for this is
> +# xxxxx

Incomplete?

> +#
> +#-----------------------------------------------------------------------
> +# Copyright (c) 2017 Liu Bo. All Rights Reserved.

You're signing off this patch an Oracle employee, but claiming
personal copyright. Please clarify who owns the copyright - if it's
your personal copyright then please sign off with a personal email
address, not your employer's...

Also, I note that these recently added tests from you:

tests/btrfs/140:# Copyright (c) 2017 Liu Bo. All Rights Reserved.
tests/btrfs/141:# Copyright (c) 2017 Liu Bo. All Rights Reserved.
tests/btrfs/142:# Copyright (c) 2017 Liu Bo. All Rights Reserved.
tests/btrfs/143:# Copyright (c) 2017 Liu Bo. All Rights Reserved.
tests/generic/406:# Copyright (c) 2017 Liu Bo. All Rights Reserved.

all have this same ambiguity - personal copyright with employer
signoff in the commit. This definitely needs clarification and
fixing if it is wrong....

> +disable_io_failure()
> +{
> + echo 0 > $SYSFS_BDEV/make-it-fail
> + echo 0 > $DEBUGFS_MNT/fail_make_request/probability
> + echo 0 > $DEBUGFS_MNT/fail_make_request/times
> +}
> +
> +_scratch_pool_mkfs "-d raid1 -b 1G" >> $seqres.full 2>&1
> +
> +# It doesn't matter which compression algorithm we use.
> +_scratch_mount -ocompress
> +
> +# Create a file with all data being compressed
> +$XFS_IO_PROG -f -c "pwrite -W 0 8K" $SCRATCH_MNT/foobar | _filter_xfs_io

needs an fsync to reach disk.

> +# Raid1 consists of two copies and btrfs decides which copy to read by reader's
> +# %pid. Now we inject errors to copy #1 and copy #0 is good. We want to read
> +# the bad copy to trigger read-repair.
> +while true; do
> + disable_io_failure
> + # invalidate the page cache
> + $XFS_IO_PROG -f -c "fadvise -d 0 128K" $SCRATCH_MNT/foobar | _filter_xfs_io
> +
> + enable_io_failure
> + od -x $SCRATCH_MNT/foobar > /dev/null &

why are you using od to read the data when the output is piped to
dev/null? why not just xfs_io -c "pread 0 8k" ?

Cheers,

Dave.
--
Dave Chinner
david@fromorbit.com