On Mon, Sep 04 2017, Xiao Ni wrote: > On 09/04/2017 10:45 AM, Xiao Ni wrote: >> >> >> On 09/04/2017 10:16 AM, NeilBrown wrote: >>> On Sat, Sep 02 2017, Xiao Ni wrote: >>> >>>> Hi Neil and Shaohua >>>> >>>> I'm trying to reproduce the problem the problem >>>> "raid5_finish_reshape is stuck at revalidate_disk". >>>> But there is a new stuck. I tried with 4.13.0-rc5 and latest mdadm. >>>> The steps are: >>>> >>>> #!/bin/bash >>>> num=0 >>>> while [ 1 ] >>>> do >>>> echo "*************************$num" >>>> mdadm -Ss >>>> mdadm --create --run /dev/md0 --level 5 --metadata 1.2 >>>> --raid-devices 5 /dev/loop0 /dev/loop1 /dev/loop2 /dev/loop3 >>>> /dev/loop4 --spare-devices 1 /dev/loop5 --chunk 512 >>>> mdadm --wait /dev/md0 >>>> mkfs -t ext4 /dev/md0 >>>> mount -t ext4 /dev/md0 /mnt/md_test >>>> dd if=/dev/urandom of=/mnt/md_test/testfile bs=1M count=100 >>>> mdadm --add /dev/md0 /dev/loop6 >>>> mdadm --grow --raid-devices 6 /dev/md0 >>>> dd if=/dev/urandom of=/mnt/md_test/testfile bs=1M count=1000 >>>> mdadm --wait /dev/md0 >>>> ((num++)) >>>> umount /dev/md0 >>>> done >>>> >>>> The calltrace messages are: >>>> Sep 1 13:57:25 localhost kernel: INFO: task kworker/u8:4:21401 >>>> blocked for more than 120 seconds. >>>> Sep 1 13:57:25 localhost kernel: Tainted: G OE 4.13.0-rc5 #2 >>>> Sep 1 13:57:25 localhost kernel: "echo 0 > >>>> /proc/sys/kernel/hung_task_timeout_secs" disables this message. >>>> Sep 1 13:57:25 localhost kernel: kworker/u8:4 D 0 21401 >>>> 2 0x00000080 >>>> Sep 1 13:57:25 localhost kernel: Workqueue: writeback wb_workfn >>>> (flush-9:0) >>>> Sep 1 13:57:25 localhost kernel: Call Trace: >>>> Sep 1 13:57:25 localhost kernel: __schedule+0x28d/0x890 >>>> Sep 1 13:57:25 localhost kernel: schedule+0x36/0x80 >>>> Sep 1 13:57:25 localhost kernel: md_write_start+0xf0/0x220 [md_mod] >>>> Sep 1 13:57:25 localhost kernel: ? remove_wait_queue+0x60/0x60 >>>> Sep 1 13:57:25 localhost kernel: raid5_make_request+0x89/0x8b0 >>>> [raid456] >>>> Sep 1 13:57:25 localhost kernel: ? bio_split+0x5d/0x90 >>>> Sep 1 13:57:25 localhost kernel: ? blk_queue_split+0xd2/0x630 >>>> Sep 1 13:57:25 localhost kernel: ? remove_wait_queue+0x60/0x60 >>>> Sep 1 13:57:25 localhost kernel: md_make_request+0xf5/0x260 [md_mod] >>>> .... >>>> >>>> All the processes send bio to md are stuck at md_write_start. >>>> wait_event(mddev->sb_wait, >>>> !test_bit(MD_SB_CHANGE_PENDING, >>>> &mddev->sb_flags) && !mddev->suspended); >>>> >>>> >>>> Sep 1 13:57:26 localhost kernel: INFO: task md0_reshape:23605 >>>> blocked for more than 120 seconds. >>>> Sep 1 13:57:26 localhost kernel: Tainted: G OE 4.13.0-rc5 #2 >>>> Sep 1 13:57:26 localhost kernel: "echo 0 > >>>> /proc/sys/kernel/hung_task_timeout_secs" disables this message. >>>> Sep 1 13:57:26 localhost kernel: md0_reshape D 0 23605 >>>> 2 0x00000080 >>>> Sep 1 13:57:26 localhost kernel: Call Trace: >>>> Sep 1 13:57:26 localhost kernel: __schedule+0x28d/0x890 >>>> Sep 1 13:57:26 localhost kernel: schedule+0x36/0x80 >>>> Sep 1 13:57:26 localhost kernel: raid5_sync_request+0x2cf/0x370 >>>> [raid456] >>>> Sep 1 13:57:26 localhost kernel: ? remove_wait_queue+0x60/0x60 >>>> Sep 1 13:57:26 localhost kernel: md_do_sync+0xafe/0xee0 [md_mod] >>>> Sep 1 13:57:26 localhost kernel: ? remove_wait_queue+0x60/0x60 >>>> Sep 1 13:57:26 localhost kernel: md_thread+0x132/0x180 [md_mod] >>>> Sep 1 13:57:26 localhost kernel: kthread+0x109/0x140 >>>> Sep 1 13:57:26 localhost kernel: ? find_pers+0x70/0x70 [md_mod] >>>> Sep 1 13:57:26 localhost kernel: ? kthread_park+0x60/0x60 >>>> Sep 1 13:57:26 localhost kernel: ? do_syscall_64+0x67/0x150 >>>> Sep 1 13:57:26 localhost kernel: ret_from_fork+0x25/0x30 >>>> >>>> It stucks at: >>>> /* Allow raid5_quiesce to complete */ >>>> wait_event(conf->wait_for_overlap, conf->quiesce != 2); >>>> >>>> Sep 1 13:57:26 localhost kernel: INFO: task mdadm:23613 blocked for >>>> more than 120 seconds. >>>> Sep 1 13:57:26 localhost kernel: Tainted: G OE 4.13.0-rc5 #2 >>>> Sep 1 13:57:26 localhost kernel: "echo 0 > >>>> /proc/sys/kernel/hung_task_timeout_secs" disables this message. >>>> Sep 1 13:57:26 localhost kernel: mdadm D 0 23613 >>>> 1 0x00000080 >>>> Sep 1 13:57:26 localhost kernel: Call Trace: >>>> Sep 1 13:57:26 localhost kernel: __schedule+0x28d/0x890 >>>> Sep 1 13:57:26 localhost kernel: schedule+0x36/0x80 >>>> Sep 1 13:57:26 localhost kernel: raid5_quiesce+0x274/0x2b0 [raid456] >>>> Sep 1 13:57:26 localhost kernel: ? remove_wait_queue+0x60/0x60 >>>> Sep 1 13:57:26 localhost kernel: suspend_lo_store+0x82/0xe0 [md_mod] >>>> Sep 1 13:57:26 localhost kernel: md_attr_store+0x80/0xc0 [md_mod] >>>> Sep 1 13:57:26 localhost kernel: sysfs_kf_write+0x3a/0x50 >>>> Sep 1 13:57:26 localhost kernel: kernfs_fop_write+0xff/0x180 >>>> Sep 1 13:57:26 localhost kernel: __vfs_write+0x37/0x170 >>>> Sep 1 13:57:26 localhost kernel: ? selinux_file_permission+0xe5/0x120 >>>> Sep 1 13:57:26 localhost kernel: ? security_file_permission+0x3b/0xc0 >>>> Sep 1 13:57:26 localhost kernel: vfs_write+0xb2/0x1b0 >>>> Sep 1 13:57:26 localhost kernel: ? syscall_trace_enter+0x1d0/0x2b0 >>>> Sep 1 13:57:26 localhost kernel: SyS_write+0x55/0xc0 >>>> Sep 1 13:57:26 localhost kernel: do_syscall_64+0x67/0x150 >>>> >>>> It's stuck at: >>>> conf->quiesce = 2; >>>> wait_event_cmd(conf->wait_for_quiescent, >>>> atomic_read(&conf->active_stripes) == 0 && >>>> atomic_read(&conf->active_aligned_reads) == 0, >>>> unlock_all_device_hash_locks_irq(conf), >>>> lock_all_device_hash_locks_irq(conf)); >>>> conf->quiesce = 1; >>>> >>>> [root@dell-pr1700-02 ~]# cat /proc/mdstat >>>> Personalities : [raid6] [raid5] [raid4] >>>> md0 : active raid5 loop6[7] loop4[6] loop5[5](S) loop3[3] loop2[2] >>>> loop1[1] loop0[0] >>>> 2039808 blocks super 1.2 level 5, 512k chunk, algorithm 2 >>>> [6/6] [UUUUUU] >>>> [>....................] reshape = 0.5% (2560/509952) >>>> finish=162985.0min speed=0K/sec >>>> unused devices: <none> >>>> >>>> >>>> I can reproduce this. So I add some logs by printk to check >>>> MD_SB_CHANGE_PENDING of mddev->flags >>>> and mddev->suspended. >>>> mddev->suspend : 0 >>>> mddev->flags : SP CHANGE PENDING is set >>>> conf->quiesce : 2 >>>> >>>> The I echo active > /sys/block/md0/md/array_state, reshape can start >>>> and finish successfully. >>>> >>>> I notice there are some fixes for raid5 stuck problem. Not sure >>>> whether it's introduced by those >>>> patches. >>>> >>>> Best Regards >>>> Xiao >>> Thanks for the detailed report. >>> All the processes that you have mentioned are waiting for >>> raid5_quiesce() to complete. >>> raid5_quiesce() must be waiting for either active_stripes or >>> active_aligned_reads to reach zero. Most likely active_stripes. >>> >>> That suggests that either there is a stripe that is active and isn't >>> being handled for some reason, or the accounting of active stripes has >>> problems. >>> >>> The fact that setting the array to 'active' removes the hang is >>> interesting. That would cause the threads blocked in md_write_start to >>> continue, but I cannot see how that would affect active_stripes as >>> threads waiting for md_write_start() never hold a stripe. Doing that >>> could cause a stripe to be used, then released, which might trigger a >>> wakeup that had been lost. >> At first I doubt there are some active strips that haven't been >> handled yet. >> But the process raid5d doesn't appear in calltrace. It wasn't stuck. >>> >>> It would be useful to see if ->active_stripes is 0 when the deadlock >>> happens. >>> One way to do that is to add a printk into raid5_status(). Then >>> whenever you "cat /proc/mdstat" the printk will trigger and tell you the >>> value of ->active_stripes. >>> >>> I haven't managed to reproduce this yet, or I would track it down my >>> self. >> >> Sure the testing is running again. I'll give the information later. > > Hi Neil > > I have reproduced this. > > [root@dell-pr1700-02 ~]# cat /proc/mdstat > Personalities : [raid6] [raid5] [raid4] > md0 : active raid5 loop6[7] loop4[6] loop5[5](S) loop3[3] loop2[2] > loop1[1] loop0[0] > 2039808 blocks super 1.2 level 5, 512k chunk, algorithm 2 [6/6] > [UUUUUU] > [>....................] reshape = 0.5% (2560/509952) > finish=2498.2min speed=3K/sec > > unused devices: <none> > [root@dell-pr1700-02 ~]# dmesg > [ 3072.826251] suspend : 0 > [ 3072.828683] SP CHANGE PENDING is set > [ 3072.832243] conf quiesce 2 > [ 3072.834932] active stripes : 251 > [ 3072.838139] active aligned reads : 0 > > [root@dell-pr1700-02 ~]# ps auxf | grep md > ... > root 1682 0.0 0.0 0 0 ? S< 23:02 0:00 \_ [md] > root 3103 97.2 0.0 0 0 ? R 23:34 14:06 \_ > [md0_raid5] > root 3123 0.0 0.0 0 0 ? D 23:34 0:00 \_ > [jbd2/md0-8] > root 3134 0.0 0.0 0 0 ? D 23:34 0:00 \_ > [md0_reshape] > .... > root 3142 0.5 0.0 108996 2728 pts/1 D+ 23:34 0:04 > | \_ dd if=/dev/urandom of=/mnt/md_test/testfile bs=1M count=1000 > root 3223 0.0 0.0 112672 2300 pts/0 S+ 23:48 0:00 > \_ grep --color=auto md > root 3141 0.0 0.0 10132 5288 ? DLs 23:34 0:00 > /usr/sbin/mdadm --grow --continue /dev/md0 > > It's strange, raid5d is running but it don't handle active stripes. > Do you need more information? It would help a lot to know waht md0_raid5 is doing. It appears to be spinning and that is presumably the cause of the problem. You could try echo file raid5.c +p > /sys/kernel/debug/dynamic_debug/control or see if /proc/3103/stack contains anything useful. Maybe perf could be used to see where it is spending its time. NeilBrown
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