Re: jbd2: don't wake kjournald unnecessarily

[Carlos Maiolino <cmaiolino@redhat.com>]

On Mon, Jan 21, 2013 at 11:47:33AM +0100, Jan Kara wrote:
> On Sun 20-01-13 01:06:40, Sedat Dilek wrote:
> > On Sun, Jan 20, 2013 at 12:44 AM, Sedat Dilek <sedat.dilek@gmail.com> wrote:
> > > Hi,
> > >
> > > I and some others hit a similiar problem in Linux-Next
> > > (next-20130118), please see [1] and [2].
> > >
> > > [3] has a interim analyze of my problems.
> > >
> > > After suspecting the problem was caused by TTY-NEXT, it turned out to
> > > be a JBD2 problem finally.
> > > The freezer/pm_test was helpful to hit the issue (Thanks Rafael for the hint!).
> > >
> > > So, the issue has two faces: TTY and JBD2.
> > > [4] gives a list and URLs of the patches I had to apply to have a
> > > clean system again.
> > >
> > > After applying the two TTY patches (without Eric's JBD2-fix!) the
> > > call-trace after freezer/pm_test looked like this;
> > >
> > > [  433.527986] PM: Syncing filesystems ... done.
> > > [  433.843761] PM: Preparing system for mem sleep
> > > [  436.306002] Freezing user space processes ...
> > > [  456.304956] Freezing of tasks failed after 20.01 seconds (1 tasks
> > > refusing to freeze, wq_busy=0):
> > > [  456.305060] Cache I/O       D ffffffff8180d780     0  2132      1 0x00000004
> > > [  456.305065]  ffff88007b9dfe18 0000000000000046 ffff88007b9dfdc8
> > > 0000000300000001
> > > [  456.305069]  ffff880097e21720 ffff88007b9dffd8 ffff88007b9dffd8
> > > ffff88007b9dffd8
> > > [  456.305072]  ffff880119b32e40 ffff880097e21720 ffff88007b9dfe28
> > > ffff880118077800
> > > [  456.305076] Call Trace:
> > > [  456.305085]  [<ffffffff816b7469>] schedule+0x29/0x70
> > > [  456.305089]  [<ffffffff8129067d>] jbd2_log_wait_commit+0xcd/0x1a0
> > > [  456.305094]  [<ffffffff8107eac0>] ? add_wait_queue+0x60/0x60
> > > [  456.305098]  [<ffffffff812307a5>] ext4_sync_file+0x205/0x380
> > > [  456.305103]  [<ffffffff811c43ad>] do_fsync+0x5d/0x90
> > > [  456.305108]  [<ffffffff8119442b>] ? sys_write+0x6b/0xa0
> > > [  456.305111]  [<ffffffff811c4790>] sys_fsync+0x10/0x20
> > > [  456.305114]  [<ffffffff816c0edd>] system_call_fastpath+0x1a/0x1f
> > > [  456.305122]
> > > [  456.305124] Restarting tasks ... done.
> > > [  456.315056] video LNXVIDEO:00: Restoring backlight state
> > >
> > > After applying Eric's patch [5], I could not hit the call-trace again.
> > > NOTE: The patch is from December 2012 and is not shipped in latest Linux-Next.
> > >
> > > The attached testcase script was helpful to force the call-trace.
> > > I have run 50 loops of it w/o an issue!
> > >
> > > Feel free to add a Reported-by/Tested-by.
> > > ( The issue kept me busy for the last days. )
> > >
> > > Regards,
> > > - Sedat -
> > >
> > > [1] http://marc.info/?t=135283664600002&r=1&w=2
> > > [2] http://marc.info/?t=135862023700004&r=1&w=2
> > > [3] http://marc.info/?l=linux-kernel&m=135862010419101&w=2
> > > [4] http://marc.info/?l=linux-next&m=135863550923093&w=2
> > > [5] http://patchwork.ozlabs.org/patch/207237/
> > 
> > Hi all,
> > 
> > this is really ugly... I could cry!
> > 
> > GRRR, I have hit the original issue again while running my testcase script!
> > 
> > [  363.831226] PM: Syncing filesystems ... done.
> > [  363.988855] PM: Preparing system for mem sleep
> > [  369.032965] Freezing user space processes ... (elapsed 0.11 seconds) done.
> > [  369.145792] Freezing remaining freezable tasks ...
> > [  389.137643] Freezing of tasks failed after 20.01 seconds (1 tasks
> > refusing to freeze, wq_busy=0):
> > [  389.137760] jbd2/loop0-8    D ffffffff8180d780     0   295      2 0x00000000
> > [  389.137769]  ffff8801181dfb68 0000000000000046 ffff880117de5c80
> > 0000000000000001
> > [  389.137778]  ffff880117de5c80 ffff8801181dffd8 ffff8801181dffd8
> > ffff8801181dffd8
> > [  389.137784]  ffffffff81c15440 ffff880117de5c80 ffff8801181dfb68
> > ffff88011fa14738
> > [  389.137791] Call Trace:
> > [  389.137810]  [<ffffffff811c6830>] ? __wait_on_buffer+0x30/0x30
> > [  389.137819]  [<ffffffff816b7479>] schedule+0x29/0x70
> > [  389.137825]  [<ffffffff816b754f>] io_schedule+0x8f/0xd0
> > [  389.137832]  [<ffffffff811c683e>] sleep_on_buffer+0xe/0x20
> > [  389.137842]  [<ffffffff816b5d4f>] __wait_on_bit+0x5f/0x90
> > [  389.137849]  [<ffffffff811c5ef1>] ? submit_bh+0x121/0x1e0
> > [  389.137856]  [<ffffffff811c6830>] ? __wait_on_buffer+0x30/0x30
> > [  389.137864]  [<ffffffff816b5dfc>] out_of_line_wait_on_bit+0x7c/0x90
> > [  389.137873]  [<ffffffff8107eb00>] ? autoremove_wake_function+0x40/0x40
> > [  389.137879]  [<ffffffff811c682e>] __wait_on_buffer+0x2e/0x30
> > [  389.137891]  [<ffffffff8128c02c>]
> > jbd2_journal_commit_transaction+0x18cc/0x1d60
> > [  389.137899]  [<ffffffff816b860e>] ? _raw_spin_lock_irqsave+0x2e/0x40
> > [  389.137908]  [<ffffffff81069fbf>] ? try_to_del_timer_sync+0x4f/0x70
> > [  389.137915]  [<ffffffff81290836>] kjournald2+0xd6/0x3e0
> > [  389.137921]  [<ffffffff8107eac0>] ? add_wait_queue+0x60/0x60
> > [  389.137926]  [<ffffffff81290760>] ? commit_timeout+0x10/0x10
> > [  389.137932]  [<ffffffff8107ded0>] kthread+0xc0/0xd0
> > [  389.137939]  [<ffffffff8107de10>] ? flush_kthread_worker+0xb0/0xb0
> > [  389.137946]  [<ffffffff816c0e2c>] ret_from_fork+0x7c/0xb0
> > [  389.137951]  [<ffffffff8107de10>] ? flush_kthread_worker+0xb0/0xb0
> > [  389.138017]
> > [  389.138021] Restarting kernel threads ... done.
> > [  389.138173] Restarting tasks ... done.
> > [  389.147980] video LNXVIDEO:00: Restoring backlight state
> > 
> > I suspect there are still issues in JBD2 (BTW I run here EXT4FS).
> > 
> > [  389.137643] Freezing of tasks failed after 20.01 seconds (1 tasks
> > refusing to freeze, wq_busy=0):
> > [  389.137760] jbd2/loop0-8    D ffffffff8180d780     0   295      2 0x00000000
> > 
> > Have a good night, /me -> watching TV!
>   The traces don't suggest an ext4/jbd2 problem. What is happening is that
> jbd2 is waiting for IO to finish and that never happens. Seeing that you
> loop device I'd think it's some interaction of the loop device and
> freezing. Can you reproduce the issue without the loop device (i.e. with
> the filesystem directly on e.g. scsi disk)? I suspect the reason is
> something like that the backing filesystem is already frozen so filesystem
> on top of it cannot write all the data and hangs waiting for IO -> suspend
> doesn't happen. Contents of /proc/mounts and losetup -l would help us
> understand what's going on.
						^^^ Shouldn't be `losetup -a`?
> 
> 								Honza
> -- 
> Jan Kara <jack@suse.cz>
> SUSE Labs, CR
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-- 
Carlos