Re: [PATCH 3/6] fstests: regression test for btrfs dio read repair

[Liu Bo <bo.li.liu@oracle.com>]

On Wed, May 10, 2017 at 06:53:26PM +0800, Eryu Guan wrote:
> On Tue, May 09, 2017 at 11:56:08AM -0600, Liu Bo wrote:
> > This case tests whether dio read can repair the bad copy if we have
> > a good copy.
> > 
> > Commit 2dabb3248453 ("Btrfs: Direct I/O read: Work on sectorsized blocks")
> > introduced the regression.
> > 
> > The upstream fix is
> > 	Btrfs: fix invalid dereference in btrfs_retry_endio
> 
> I noticed this is in upstream now, you can refer to it along with hash
> tag too.
> 
> > 
> > Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
> > ---
> >  tests/btrfs/140     | 115 ++++++++++++++++++++++++++++++++++++++++++++++++++++
> >  tests/btrfs/140.out |  39 ++++++++++++++++++
> >  tests/btrfs/group   |   1 +
> >  3 files changed, 155 insertions(+)
> >  create mode 100755 tests/btrfs/140
> >  create mode 100644 tests/btrfs/140.out
> > 
> > diff --git a/tests/btrfs/140 b/tests/btrfs/140
> > new file mode 100755
> > index 0000000..09a9939
> > --- /dev/null
> > +++ b/tests/btrfs/140
> > @@ -0,0 +1,115 @@
> > +#! /bin/bash
> > +# FS QA Test 140
> > +#
> > +# Regression test for btrfs DIO read's repair during read.
> > +#
> > +# Commit 2dabb3248453 ("Btrfs: Direct I/O read: Work on sectorsized blocks")
> > +# introduced the regression.
> > +# The upstream fix is
> > +# 	Btrfs: fix invalid dereference in btrfs_retry_endio
> > +#
> > +#-----------------------------------------------------------------------
> > +# Copyright (c) 2017 Liu Bo.  All Rights Reserved.
> > +#
> > +# This program is free software; you can redistribute it and/or
> > +# modify it under the terms of the GNU General Public License as
> > +# published by the Free Software Foundation.
> > +#
> > +# This program is distributed in the hope that it would be useful,
> > +# but WITHOUT ANY WARRANTY; without even the implied warranty of
> > +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> > +# GNU General Public License for more details.
> > +#
> > +# You should have received a copy of the GNU General Public License
> > +# along with this program; if not, write the Free Software Foundation,
> > +# Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
> > +#-----------------------------------------------------------------------
> > +#
> > +
> > +seq=`basename $0`
> > +seqres=$RESULT_DIR/$seq
> > +echo "QA output created by $seq"
> > +
> > +here=`pwd`
> > +tmp=/tmp/$$
> > +status=1	# failure is the default!
> > +trap "_cleanup; exit \$status" 0 1 2 3 15
> > +
> > +_cleanup()
> > +{
> > +	cd /
> > +	rm -f $tmp.*
> > +}
> > +
> > +# get standard environment, filters and checks
> > +. ./common/rc
> > +. ./common/filter
> > +
> > +# remove previous $seqres.full before test
> > +rm -f $seqres.full
> > +
> > +# real QA test starts here
> > +
> > +# Modify as appropriate.
> > +_supported_fs btrfs
> > +_supported_os Linux
> > +_require_scratch_dev_pool 2
> > +
> > +_require_btrfs_command inspect-internal dump-tree
> > +_require_command "$FILEFRAG_PROG" filefrag
> > +_require_odirect
> > +
> > +get_physical()
> > +{
> > +	# $1 is logical address
> > +	# print chunk tree and find devid 2 which is $SCRATCH_DEV
> > +	$BTRFS_UTIL_PROG inspect-internal dump-tree -t 3 $SCRATCH_DEV | \
> > +	grep $1 -A 6 | awk '($1 ~ /stripe/ && $3 ~ /devid/ && $4 ~ /1/) { print $6 }'
> > +}
> > +
> > +_scratch_dev_pool_get 2
> > +# step 1, create a raid1 btrfs which contains one 128k file.
> > +echo "step 1......mkfs.btrfs" >>$seqres.full
> > +
> > +mkfs_opts="-d raid1 -b 1G"
> > +_scratch_pool_mkfs $mkfs_opts >>$seqres.full 2>&1
> > +
> > +# -o nospace_cache makes sure data is written to the start position of the data
> > +# chunk
> > +_scratch_mount -o nospace_cache
> > +
> > +$XFS_IO_PROG -f -d -c "pwrite -S 0xaa -b 128K 0 128K" "$SCRATCH_MNT/foobar" | _filter_xfs_io
> > +
> > +# step 2, corrupt the first 64k of one copy (on SCRATCH_DEV which is the first
> > +# one in $SCRATCH_DEV_POOL
> > +echo "step 2......corrupt file extent" >>$seqres.full
> > +
> > +${FILEFRAG_PROG} -v $SCRATCH_MNT/foobar >> $seqres.full
> > +logical_in_btrfs=`${FILEFRAG_PROG} -v $SCRATCH_MNT/foobar | _filter_filefrag | cut -d '#' -f 1`
> > +physical_on_scratch=`get_physical ${logical_in_btrfs}`
> > +
> > +_scratch_unmount
> > +$XFS_IO_PROG -d -c "pwrite -S 0xbb -b 64K $physical_on_scratch 64K" $SCRATCH_DEV | _filter_xfs_io
> > +
> > +_scratch_mount
> > +
> > +# step 3, 128k dio read (this read can repair bad copy)
> > +echo "step 3......repair the bad copy" >>$seqres.full
> > +
> > +# since raid1 consists of two copies, and the following read may read the good
> > +# copy directly, so lets loop 10 times here and discard output that dio reads
> > +# give
> > +for i in `seq 1 10`; do
> > +	$XFS_IO_PROG -d -c "pread -b 128K 0 128K" "$SCRATCH_MNT/foobar" > /dev/null
> > +	_get_current_dmesg | grep -q -e "csum failed" && break
> > +done
> 
> Half of the time I got test failure because pread from SCRATCH_DEV read
> 0xbb instead of 0xaa on v4.11 kernel (bug should be fixed there), tested
> on two different hosts and could hit failure on both hosts.
> 
> Similar failure happened to all the 4 tests randomly. I thought it was
> because "csum failed" was never hit, so I tried a "while true; do" loop,
> and that did fix the btrfs/140 failure for me, but then btrfs/141 would
> loop forever sometimes.
> 
> On the other hand, the tests from your last post always passed on the
> same test host, but I didn't see anything particular would make this
> difference..
> 
> Can you please take a look? Thanks!
> 

Oh, sorry for the trouble, it's all due to the same reason, that
is, the stripe read balance in btrfs simply looks at
(current->pid % num_stripes) and picks up a stripe to read from.

Since I put the bad data on stripe 1 in raid1 profile, we need an
odd $pid to trigger the checksum failures, but I have no idea how
to certainly get a task with odd pid number in one shot, so I'll
just use "while true; do" for now, and update it later if I find
a solution.

Thanks,

-liubo
> Eryu
> 
> > +
> > +_scratch_unmount
> > +
> > +# check if the repair works
> > +$XFS_IO_PROG -d -c "pread -v -b 512 $physical_on_scratch 512" $SCRATCH_DEV | _filter_xfs_io
> > +
> > +_scratch_dev_pool_put
> > +# success, all done
> > +status=0
> > +exit
> > diff --git a/tests/btrfs/140.out b/tests/btrfs/140.out
> > new file mode 100644
> > index 0000000..c8565f5
> > --- /dev/null
> > +++ b/tests/btrfs/140.out
> > @@ -0,0 +1,39 @@
> > +QA output created by 140
> > +wrote 131072/131072 bytes at offset 0
> > +XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
> > +wrote 65536/65536 bytes at offset 136708096
> > +XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
> > +08260000:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
> > +08260010:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
> > +08260020:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
> > +08260030:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
> > +08260040:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
> > +08260050:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
> > +08260060:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
> > +08260070:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
> > +08260080:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
> > +08260090:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
> > +082600a0:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
> > +082600b0:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
> > +082600c0:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
> > +082600d0:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
> > +082600e0:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
> > +082600f0:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
> > +08260100:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
> > +08260110:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
> > +08260120:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
> > +08260130:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
> > +08260140:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
> > +08260150:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
> > +08260160:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
> > +08260170:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
> > +08260180:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
> > +08260190:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
> > +082601a0:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
> > +082601b0:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
> > +082601c0:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
> > +082601d0:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
> > +082601e0:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
> > +082601f0:  aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa  ................
> > +read 512/512 bytes at offset 136708096
> > +XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
> > diff --git a/tests/btrfs/group b/tests/btrfs/group
> > index 9d4b80b..1cb9c98 100644
> > --- a/tests/btrfs/group
> > +++ b/tests/btrfs/group
> > @@ -141,3 +141,4 @@
> >  137 auto quick send
> >  138 auto compress
> >  139 auto qgroup
> > +140 auto quick
> > -- 
> > 2.5.0
> >