From mboxrd@z Thu Jan 1 00:00:00 1970 From: Xiao Ni Subject: Re: Stuck in md_write_start because MD_SB_CHANGE_PENDING can't be cleared Date: Mon, 4 Sep 2017 11:52:40 +0800 Message-ID: References: <546311999.4473128.1504339295016.JavaMail.zimbra@redhat.com> <877exfdx7x.fsf@notabene.neil.brown.name> <22698eb3-35f7-04e5-96e8-26470d892655@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <22698eb3-35f7-04e5-96e8-26470d892655@redhat.com> Sender: linux-raid-owner@vger.kernel.org To: NeilBrown , linux-raid Cc: shli@kernel.org List-Id: linux-raid.ids 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: >>> >>> >>> 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: [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? Regards Xiao > > Regards > Xiao >> >> Thanks, >> NeilBrown > > -- > To unsubscribe from this list: send the line "unsubscribe linux-raid" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html