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Message-ID: <20090602115339.GG11363@kernel.dk> Date: Tue, 2 Jun 2009 13:53:39 +0200 From: Jens Axboe <jens.axboe@...cle.com> To: "Zhang, Yanmin" <yanmin_zhang@...ux.intel.com> Cc: linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org, chris.mason@...cle.com, david@...morbit.com, hch@...radead.org, akpm@...ux-foundation.org, jack@...e.cz, richard@....demon.co.uk Subject: Re: [PATCH 0/12] Per-bdi writeback flusher threads v7 On Tue, Jun 02 2009, Zhang, Yanmin wrote: > On Wed, 2009-05-27 at 08:17 +0200, Jens Axboe wrote: > > On Wed, May 27 2009, Zhang, Yanmin wrote: > > > On Tue, 2009-05-26 at 11:33 +0200, Jens Axboe wrote: > > > > Hi, > > > > > > > > Here's the 7th version of the writeback patches. Changes since > > > > v5/v6: > > > > > > > > - Move the sync_supers() to the global bdi_forker_task() thread, so we > > > > don't writeback the supers from all the bdi kupdated() tasks. > > > > - Make bdi_start_writeback() and bdi_writeback_all() be sync when called > > > > with WB_SYNC_ALL only. > > > > - Shuffle some more things around to make a cleaner series. The sync vs > > > > async nature of bdi_writeback_all() and bdi_start_writeback() isn't > > > > consistent through the series, but otherwise things should be sane. > > > > > > > > I'd appreciate if Richard and Yanmin could re-run testing with this, > > > > just to make sure that things are sane. For ease of patching, I've > > > > put the full diff here: > > > > > > > > http://kernel.dk/writeback-v7.patch > > > I ported it to 2.6.30-rc6 with some change in file mm/page-write.c, so I > > > could compare with old data. > > > > > > See the attachment. > > > > > > The new testing hits the hang issue again. It seems there is still a race. > > > > It's actually not a race, it's a deadlock on the bdi_lock. If you find > > the bdi-default task, it should be stuck in the mutex slow path. I > > posted this quickie [1] yesterday but didn't test it, I'll test it today and > > post a v8. > > > > > > [1] http://lkml.org/lkml/2009/5/26/401 > Jens, > > I checked V9 and found it includes the fix. However, the issue appears again on another > machine when doing 'umount -f /dev/sda3'. > > INFO: task umount:17110 blocked for more than 120 seconds. > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > umount D ffffc20000011300 6128 17110 16225 > ffffffff8093e350 0000000000000086 0000000000000000 0000000000000000 > ffffe200006482e8 0000000000004000 0000000000011300 000000000000c868 > ffff8801be07dd48 0000000000000000 ffff8801be5f8000 ffff8801be5f8388 > Call Trace: > [<ffffffff802c316c>] ? bdi_sched_wait+0x0/0xd > [<ffffffff8071e53f>] ? schedule+0x9/0x1e > [<ffffffff802c3175>] ? bdi_sched_wait+0x9/0xd > [<ffffffff8071eb06>] ? __wait_on_bit+0x41/0x71 > [<ffffffff802c316c>] ? bdi_sched_wait+0x0/0xd > [<ffffffff8071eba1>] ? out_of_line_wait_on_bit+0x6b/0x77 > [<ffffffff8024cbf0>] ? wake_bit_function+0x0/0x23 > [<ffffffff802c2e1f>] ? bdi_writeback_all+0x117/0x14e > [<ffffffff802c2f8f>] ? generic_sync_sb_inodes+0x31/0xdc > [<ffffffff802c30bd>] ? sync_inodes_sb+0x83/0x88 > [<ffffffff802ab4f3>] ? fsync_super+0x9/0x16 > [<ffffffff802ab7a8>] ? generic_shutdown_super+0x25/0xde > [<ffffffff802ab883>] ? kill_block_super+0x22/0x3a > [<ffffffff802abec9>] ? deactivate_super+0x5f/0x76 > [<ffffffff802bdf5f>] ? sys_umount+0x2cd/0x2fc > [<ffffffff8020ba2b>] ? system_call_fastpath+0x16/0x1b > > > > Then, I run command sync and hit a panic: > > [root@...-ne02 ~]# BUG: unable to handle kernel paging request at 0000000561887e50 > IP: [<ffffffff8022d121>] task_rq_lock+0x28/0x6b > PGD bc551067 PUD 0 > Oops: 0000 [#1] SMP > last sysfs file: /sys/class/net/eth1/ifindex > CPU 9 > Modules linked in: > Pid: 27470, comm: sync Not tainted 2.6.30-rc7-bdiflusherv9 #1 X8DTN > RIP: 0010:[<ffffffff8022d121>] [<ffffffff8022d121>] task_rq_lock+0x28/0x6b > RSP: 0018:ffff8800bccd9e48 EFLAGS: 00010096 > RAX: 00000000bc1d0420 RBX: 0000000000011300 RCX: 0000000000000000 > RDX: 00000000000110fd RSI: ffff8800bccd9e88 RDI: ffff8800bd703090 > RBP: 0000000000011300 R08: fefefefefefefeff R09: 0000000000000000 > R10: 00000034cbd6da70 R11: 00000034cbacab70 R12: ffff8800bccd9e88 > R13: ffff8800bd703090 R14: 000000000000000f R15: 0000000000000000 > FS: 00007f04696dd6f0(0000) GS:ffffc20001200000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 0000000561887e50 CR3: 00000000bc0d6000 CR4: 00000000000006e0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 > Process sync (pid: 27470, threadinfo ffff8800bccd8000, task ffff8800bc4ee810) > Stack: > 00000034cbaca000 000000000000000f ffff8800bd703090 ffff8800bccd9f18 > ffff8800bd780138 ffffffff80233889 0000000000000000 ffffffff802c2be6 > 0000000000000296 ffff8800bcd6f900 ffff8800bd5a9d10 ffff8800bccd9f18 > Call Trace: > [<ffffffff80233889>] ? try_to_wake_up+0x8f/0x2d0 > [<ffffffff802c2be6>] ? bdi_alloc_work+0x28/0xa6 > [<ffffffff802c2e45>] ? bdi_writeback_all+0x13d/0x14e > [<ffffffff8027f151>] ? wakeup_flusher_threads+0x4c/0x51 > [<ffffffff802c5c39>] ? do_sync+0xb/0x5a > [<ffffffff802c5caa>] ? sys_sync+0xe/0x14 > [<ffffffff8020ba2b>] ? system_call_fastpath+0x16/0x1b > Code: 41 59 c3 41 55 49 89 fd 41 54 49 89 f4 55 48 c7 c5 00 13 01 00 53 48 83 ec 08 9c 58 fa 49 89 04 24 49 8b 45 08 48 89 e > RIP [<ffffffff8022d121>] task_rq_lock+0x28/0x6b > RSP <ffff8800bccd9e48> > CR2: 0000000561887e50 > > > > Another machine hangs twice with 2.6.30-rc7+bdiflusherV9 > after it's idle for hours without testing. Serial console > didn't capture any useful info. I'm looking into the issue that Jan Kara pointed out, we do appear still to have a race with umount and super block referencing. > As for perforamnce testing result, there is no big variation from > previous vesions. That's good, at least :-) -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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