on 2020/02/18 16:24, Jan Kara wrote: > On Tue 18-02-20 11:25:37, Yang Xu wrote: >> on 2020/02/14 23:00, Jan Kara wrote: >>> On Fri 14-02-20 18:24:50, Yang Xu wrote: >>>> on 2020/02/14 5:10, Jan Kara wrote: >>>>> On Thu 13-02-20 16:49:21, Yang Xu wrote: >>>>>>>> When I test generic/269(ext4) on 5.6.0-rc1 kernel, it hangs. >>>>>>>> ---------------------------------------------- >>>>>>>> dmesg as below: >>>>>>>> 76.506753] run fstests generic/269 at 2020-02-11 05:53:44 >>>>>>>> [ 76.955667] EXT4-fs (sdc): mounted filesystem with ordered data mode. >>>>>>>> Opts: acl, user_xattr >>>>>>>> [ 100.912511] device virbr0-nic left promiscuous mode >>>>>>>> [ 100.912520] virbr0: port 1(virbr0-nic) entered disabled state >>>>>>>> [ 246.801561] INFO: task dd:17284 blocked for more than 122 seconds. >>>>>>>> [ 246.801564] Not tainted 5.6.0-rc1 #41 >>>>>>>> [ 246.801565] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables >>>>>>>> this mes sage. >>>>>>>> [ 246.801566] dd D 0 17284 16931 0x00000080 >>>>>>>> [ 246.801568] Call Trace: >>>>>>>> [ 246.801584] ? __schedule+0x251/0x690 >>>>>>>> [ 246.801586] schedule+0x40/0xb0 >>>>>>>> [ 246.801588] wb_wait_for_completion+0x52/0x80 >>>>>>>> [ 246.801591] ? finish_wait+0x80/0x80 >>>>>>>> [ 246.801592] __writeback_inodes_sb_nr+0xaa/0xd0 >>>>>>>> [ 246.801593] try_to_writeback_inodes_sb+0x3c/0x50 >>>>>>> >>>>>>> Interesting. Does the hang resolve eventually or the machine is hung >>>>>>> permanently? If the hang is permanent, can you do: >>>>>>> >>>>>>> echo w >/proc/sysrq-trigger >>>>>>> >>>>>>> and send us the stacktraces from dmesg? Thanks! >>>>>> Yes. the hang is permanent, log as below: >>>> full dmesg as attach >>> ... >>> >>> Thanks! So the culprit seems to be: >>> >>>> [ 388.087799] kworker/u12:0 D 0 32 2 0x80004000 >>>> [ 388.087803] Workqueue: writeback wb_workfn (flush-8:32) >>>> [ 388.087805] Call Trace: >>>> [ 388.087810] ? __schedule+0x251/0x690 >>>> [ 388.087811] ? __switch_to_asm+0x34/0x70 >>>> [ 388.087812] ? __switch_to_asm+0x34/0x70 >>>> [ 388.087814] schedule+0x40/0xb0 >>>> [ 388.087816] schedule_timeout+0x20d/0x310 >>>> [ 388.087818] io_schedule_timeout+0x19/0x40 >>>> [ 388.087819] wait_for_completion_io+0x113/0x180 >>>> [ 388.087822] ? wake_up_q+0xa0/0xa0 >>>> [ 388.087824] submit_bio_wait+0x5b/0x80 >>>> [ 388.087827] blkdev_issue_flush+0x81/0xb0 >>>> [ 388.087834] jbd2_cleanup_journal_tail+0x80/0xa0 [jbd2] >>>> [ 388.087837] jbd2_log_do_checkpoint+0xf4/0x3f0 [jbd2] >>>> [ 388.087840] __jbd2_log_wait_for_space+0x66/0x190 [jbd2] >>>> [ 388.087843] ? finish_wait+0x80/0x80 >>>> [ 388.087845] add_transaction_credits+0x27d/0x290 [jbd2] >>>> [ 388.087847] ? blk_mq_make_request+0x289/0x5d0 >>>> [ 388.087849] start_this_handle+0x10a/0x510 [jbd2] >>>> [ 388.087851] ? _cond_resched+0x15/0x30 >>>> [ 388.087853] jbd2__journal_start+0xea/0x1f0 [jbd2] >>>> [ 388.087869] ? ext4_writepages+0x518/0xd90 [ext4] >>>> [ 388.087875] __ext4_journal_start_sb+0x6e/0x130 [ext4] >>>> [ 388.087883] ext4_writepages+0x518/0xd90 [ext4] >>>> [ 388.087886] ? do_writepages+0x41/0xd0 >>>> [ 388.087893] ? ext4_mark_inode_dirty+0x1f0/0x1f0 [ext4] >>>> [ 388.087894] do_writepages+0x41/0xd0 >>>> [ 388.087896] ? snprintf+0x49/0x60 >>>> [ 388.087898] __writeback_single_inode+0x3d/0x340 >>>> [ 388.087899] writeback_sb_inodes+0x1e5/0x480 >>>> [ 388.087901] wb_writeback+0xfb/0x2f0 >>>> [ 388.087902] wb_workfn+0xf0/0x430 >>>> [ 388.087903] ? __switch_to_asm+0x34/0x70 >>>> [ 388.087905] ? finish_task_switch+0x75/0x250 >>>> [ 388.087907] process_one_work+0x1a7/0x370 >>>> [ 388.087909] worker_thread+0x30/0x380 >>>> [ 388.087911] ? process_one_work+0x370/0x370 >>>> [ 388.087912] kthread+0x10c/0x130 >>>> [ 388.087913] ? kthread_park+0x80/0x80 >>>> [ 388.087914] ret_from_fork+0x35/0x40 >>> >>> This process is actually waiting for IO to complete while holding >>> checkpoint_mutex which holds up everybody else. The question is why the IO >>> doesn't complete - that's definitely outside of filesystem. Maybe a bug in >>> the block layer, storage driver, or something like that... What does >>> 'cat /sys/block//inflight' show? >> Sorry for the late reply. >> This value is 0, it represent it doesn't have inflight data(but it may be >> counted bug or storage driver bug, is it right?). >> Also, it doesn't hang on my physical machine, but only hang on vm. > > Hum, curious. Just do make sure, did you check sdc (because that appears to > be the stuck device)? Yes, I check sdc, its value is 0. # cat /sys/block/sdc/inflight 0 0 > >> So what should I do in next step(change storge disk format)? > > I'd try couple of things: > > 1) If you mount ext4 with barrier=0 mount option, does the problem go away? Yes. Use barrier=0, this case doesn't hang, > > 2) Can you run the test and at the same time run 'blktrace -d /dev/sdc' to > gather traces? Once the machine is stuck, abort blktrace, process the > resulting files with 'blkparse -i sdc' and send here compressed blkparse > output. We should be able to see what was happening with the stuck request > in the trace and maybe that will tell us something. The log size is too big(58M) and our emali limit is 5M. > > Honza >