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Date: Fri, 09 Dec 2011 10:56:18 +0900
From: Masayoshi MIZUMA <m.mizuma@...fujitsu.com>
To: Jan Kara <jack@...e.cz>, Andreas Dilger <adilger.kernel@...ger.ca>,
"Theodore Ts'o" <tytso@....edu>
Cc: linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org,
Christoph Hellwig <hch@...radead.org>,
Toshiyuki Okajima <toshi.okajima@...fujitsu.com>
Subject: Re: [BUG] ext4: cannot unfreeze a filesystem due to a deadlock
(2011/02/07 20:53), Masayoshi MIZUMA wrote:
> Hi,
>
> When I checked the freeze feature for ext4 filesystem using fsfreeze command
> at 2.6.38-rc3, I got the following messeges:
Hi,
I checked freeze function with using below test program at 3.2.0-rc4,
then, I got following messeages and the test program hanged up.
I think this bug is still in 3.2.0-rc4...
The test program:
-----------------------------------------------------------
#!/bin/bash
DEV_1=/dev/sda5
MNT_1=/tmp/sda5
LOOP=500
if [[ ! -d $MNT_1 ]]
then
mkdir -p $MNT_1
fi
mkfs -t ext4 $DEV_1
mount $DEV_1 $MNT_1
./fsstress -d $MNT_1/tmp -n 10000 -p 100 > /dev/null 2>&1 &
PID=$!
for ((i=0; i<LOOP; i++))
do
echo LOOP: $i
fsfreeze -f $MNT_1
fsfreeze -u $MNT_1
done
kill $PID
-----------------------------------------------------------
The messages I got when I ran the test program is below.
-------------------------------------------------------------
INFO: task flush-8:0:720 blocked for more than 120 seconds.
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
flush-8:0 D 0000000100521461 0 720 2 0x00000000
ffff8800b4c41a40 0000000000000046 0000000000000000 0000000000000000
0000000000013440 ffff8800b4c41fd8 ffff8800b4c40010 0000000000013440
ffff8800b4c41fd8 0000000000013440 ffffffff81a0d020 ffff8800b464d4e0
Call Trace:
[<ffffffff81086b4e>] ? prepare_to_wait+0x5e/0x90
[<ffffffff814ee3ff>] schedule+0x3f/0x60
[<ffffffffa041e485>] ext4_journal_start_sb+0x145/0x1b0 [ext4]
[<ffffffff81086820>] ? wake_up_bit+0x40/0x40
[<ffffffffa0401bc5>] ? ext4_meta_trans_blocks+0xb5/0xc0 [ext4]
[<ffffffffa0406c9d>] ext4_da_writepages+0x29d/0x620 [ext4]
[<ffffffff81227a18>] ? blk_finish_plug+0x18/0x50
[<ffffffff81112bb1>] do_writepages+0x21/0x40
[<ffffffff8118e380>] writeback_single_inode+0x180/0x3b0
[<ffffffff8118e971>] writeback_sb_inodes+0x1a1/0x260
[<ffffffff8118ec6e>] wb_writeback+0xde/0x2b0
[<ffffffff810739c6>] ? try_to_del_timer_sync+0x86/0xe0
[<ffffffff8118eee6>] wb_do_writeback+0xa6/0x260
[<ffffffff81072ef0>] ? lock_timer_base+0x70/0x70
[<ffffffff8118f14a>] bdi_writeback_thread+0xaa/0x270
[<ffffffff8118f0a0>] ? wb_do_writeback+0x260/0x260
[<ffffffff8118f0a0>] ? wb_do_writeback+0x260/0x260
[<ffffffff810861a6>] kthread+0x96/0xa0
[<ffffffff814fa5b4>] kernel_thread_helper+0x4/0x10
[<ffffffff81086110>] ? kthread_worker_fn+0x1a0/0x1a0
[<ffffffff814fa5b0>] ? gs_change+0x13/0x13
INFO: task fsstress:4376 blocked for more than 120 seconds.
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
fsstress D ffff88009b52dda8 0 4376 4364 0x00000080
ffff88009b52dcb8 0000000000000082 ffffffff810d7e09 ffff88009b52dcc0
0000000000013440 ffff88009b52dfd8 ffff88009b52c010 0000000000013440
ffff88009b52dfd8 0000000000013440 ffff88009b4d54e0 ffff8800a1481560
Call Trace:
[<ffffffff810d7e09>] ? trace_clock_local+0x9/0x10
[<ffffffff814ee3ff>] schedule+0x3f/0x60
[<ffffffff814ee89d>] schedule_timeout+0x1fd/0x2e0
[<ffffffff810e5e43>] ? trace_nowake_buffer_unlock_commit+0x43/0x60
[<ffffffff810127e4>] ? __switch_to+0x194/0x320
[<ffffffff8104d623>] ? ftrace_raw_event_sched_switch+0x103/0x110
[<ffffffff814ee26d>] wait_for_common+0x11d/0x190
[<ffffffff8105a970>] ? try_to_wake_up+0x2b0/0x2b0
[<ffffffff814ee3bd>] wait_for_completion+0x1d/0x20
[<ffffffff8118daef>] writeback_inodes_sb_nr+0x7f/0xa0
[<ffffffff8118dbdf>] writeback_inodes_sb+0x5f/0x80
[<ffffffff811938d0>] ? __sync_filesystem+0x90/0x90
[<ffffffff8119388e>] __sync_filesystem+0x4e/0x90
[<ffffffff811938ef>] sync_one_sb+0x1f/0x30
[<ffffffff811695da>] iterate_supers+0x7a/0xd0
[<ffffffff81193934>] sys_sync+0x34/0x70
[<ffffffff814f8442>] system_call_fastpath+0x16/0x1b
-------------------------------------------------------------
The test program for xfstests is below.
-------------------------------------------------------------
#! /bin/bash
# FSQA Test No. 277
#
# Run fsstress and freeze/unfreeze in parallel
#
#-----------------------------------------------------------------------
# Copyright (c) 2006 Silicon Graphics, Inc. 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
#
#-----------------------------------------------------------------------
#
# creator
owner=m.mizuma@...fujitsu.com
seq=`basename $0`
echo "QA output created by $seq"
here=`pwd`
tmp=/tmp/$$
status=0 # success is the default!
trap "rm -f $tmp.*; exit \$status" 0 1 2 3 15
# get standard environment, filters and checks
. ./common.rc
. ./common.filter
_workout()
{
echo ""
echo "Run fsstress"
echo ""
num_iterations=500
out=$SCRATCH_MNT/fsstress.$$
args="-p100 -n10000 -d $out"
echo "fsstress $args" >> $here/$seq.full
$FSSTRESS_PROG $args > /dev/null 2>&1 &
pid=$!
echo "Run xfs_freeze in parallel"
for ((i=0; i < num_iterations; i++))
do
xfs_freeze -f $SCRATCH_MNT | tee -a $seq.full
xfs_freeze -u $SCRATCH_MNT | tee -a $seq.full
done
kill $pid 2> /dev/null
wait $pid
}
# real QA test starts here
_supported_fs generic
_supported_os Linux
_need_to_be_root
_require_scratch
_scratch_mkfs >> $seq.full 2>&1
_scratch_mount
if ! _workout; then
umount $SCRATCH_DEV 2>/dev/null
exit
fi
if ! _scratch_unmount; then
echo "failed to umount"
status=1
exit
fi
_check_scratch_fs
status=$?
exit
-------------------------------------------------------------
Thanks,
Masayoshi Mizuma
>
> ---------------------------------------------------------------------
> Feb 7 15:05:09 RX300S6 kernel: INFO: task fsfreeze:2104 blocked for more than 120 seconds.
> Feb 7 15:05:09 RX300S6 kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> Feb 7 15:05:09 RX300S6 kernel: fsfreeze D ffff880076d5f040 0 2104 2018 0x00000000
> Feb 7 15:05:09 RX300S6 kernel: ffff88005a9f3d98 0000000000000086 ffff88005a9f3d38 ffffffff00000000
> Feb 7 15:05:09 RX300S6 kernel: 0000000000014d40 ffff880076d5eab0 ffff880076d5f040 ffff88005a9f3fd8
> Feb 7 15:05:09 RX300S6 kernel: ffff880076d5f048 0000000000014d40 ffff88005a9f2010 0000000000014d40
> Feb 7 15:05:09 RX300S6 kernel: Call Trace:
> Feb 7 15:05:09 RX300S6 kernel: [<ffffffff814aa5f5>] rwsem_down_failed_common+0xb5/0x140
> Feb 7 15:05:09 RX300S6 kernel: [<ffffffff814aa693>] rwsem_down_write_failed+0x13/0x20
> Feb 7 15:05:09 RX300S6 kernel: [<ffffffff8122f1a3>] call_rwsem_down_write_failed+0x13/0x20
> Feb 7 15:05:09 RX300S6 kernel: [<ffffffff814a9c12>] ? down_write+0x32/0x40
> Feb 7 15:05:09 RX300S6 kernel: [<ffffffff81155b48>] thaw_super+0x28/0xd0
> Feb 7 15:05:09 RX300S6 kernel: [<ffffffff81164338>] do_vfs_ioctl+0x368/0x560
> Feb 7 15:05:09 RX300S6 kernel: [<ffffffff81157c73>] ? sys_newfstat+0x33/0x40
> Feb 7 15:05:09 RX300S6 kernel: [<ffffffff811645d1>] sys_ioctl+0xa1/0xb0
> Feb 7 15:05:09 RX300S6 kernel: [<ffffffff8100bf82>] system_call_fastpath+0x16/0x1b
> ...
> Feb 7 15:07:09 RX300S6 kernel: INFO: task flush-8:0:1409 blocked for more than 120 seconds.
> Feb 7 15:07:09 RX300S6 kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> Feb 7 15:07:09 RX300S6 kernel: flush-8:0 D ffff880037777a30 0 1409 2 0x00000000
> Feb 7 15:07:09 RX300S6 kernel: ffff880037c95a80 0000000000000046 ffff88007c8037a0 0000000000000000
> Feb 7 15:07:09 RX300S6 kernel: 0000000000014d40 ffff8800377774a0 ffff880037777a30 ffff880037c95fd8
> Feb 7 15:07:09 RX300S6 kernel: ffff880037777a38 0000000000014d40 ffff880037c94010 0000000000014d40
> Feb 7 15:07:09 RX300S6 kernel: Call Trace:
> Feb 7 15:07:09 RX300S6 kernel: [<ffffffffa00abb85>] ext4_journal_start_sb+0x75/0x130 [ext4]
> Feb 7 15:07:09 RX300S6 kernel: [<ffffffff81082fc0>] ? autoremove_wake_function+0x0/0x40
> Feb 7 15:07:09 RX300S6 kernel: [<ffffffffa0097f0a>] ext4_da_writepages+0x27a/0x640 [ext4]
> Feb 7 15:07:09 RX300S6 kernel: [<ffffffff81102c91>] do_writepages+0x21/0x40
> Feb 7 15:07:09 RX300S6 kernel: [<ffffffff811776b8>] writeback_single_inode+0x98/0x240
> Feb 7 15:07:09 RX300S6 kernel: [<ffffffff81177cfe>] writeback_sb_inodes+0xce/0x170
> Feb 7 15:07:09 RX300S6 kernel: [<ffffffff81178709>] writeback_inodes_wb+0x99/0x160
> Feb 7 15:07:09 RX300S6 kernel: [<ffffffff81178a8b>] wb_writeback+0x2bb/0x430
> Feb 7 15:07:09 RX300S6 kernel: [<ffffffff81178e2c>] wb_do_writeback+0x22c/0x280
> Feb 7 15:07:09 RX300S6 kernel: [<ffffffff81178f32>] bdi_writeback_thread+0xb2/0x260
> Feb 7 15:07:09 RX300S6 kernel: [<ffffffff81178e80>] ? bdi_writeback_thread+0x0/0x260
> Feb 7 15:07:09 RX300S6 kernel: [<ffffffff81178e80>] ? bdi_writeback_thread+0x0/0x260
> Feb 7 15:07:09 RX300S6 kernel: [<ffffffff81082936>] kthread+0x96/0xa0
> Feb 7 15:07:09 RX300S6 kernel: [<ffffffff8100cdc4>] kernel_thread_helper+0x4/0x10
> Feb 7 15:07:09 RX300S6 kernel: [<ffffffff810828a0>] ? kthread+0x0/0xa0
> Feb 7 15:07:09 RX300S6 kernel: [<ffffffff8100cdc0>] ? kernel_thread_helper+0x0/0x10
> ---------------------------------------------------------------------
>
> I think the following deadlock problem happened:
>
> [flush-8:0:1409] | [fsfreeze:2104]
> --------------------------------------------+--------------------------------
> writeback_inodes_wb |
> pin_sb_for_writeback |
> down_read_trylock(&sb->s_umount) |
> writeback_sb_inodes |thaw_super
> writeback_single_inode | down_write(&sb->s_umount)
> do_writepages | # stop until flush-8:0 releases
> ext4_da_writepages | # read lock of sb->s_umount...
> ext4_journal_start_sb |
> vfs_check_frozen |
> wait_event((sb)->s_wait_unfrozen, |
> ((sb)->s_frozen < (level))) |
> # stop until being waked up by |
> # fsfreeze... |
> --------------------------------------------+--------------------------------
>
> Could anyone check this problem?
>
> Thanks,
> Masayoshi Mizuma
>
>
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