Messages in this thread | | | Subject | Re: md_raid: mdX_raid6 looping after sync_action "check" to "idle" transition | From | Donald Buczek <> | Date | Tue, 1 Dec 2020 10:29:18 +0100 |
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Am 30.11.20 um 03:06 schrieb Guoqing Jiang: > > > On 11/28/20 13:25, Donald Buczek wrote: >> Dear Linux mdraid people, >> >> we are using raid6 on several servers. Occasionally we had failures, where a mdX_raid6 process seems to go into a busy loop and all I/O to the md device blocks. We've seen this on various kernel versions. >> >> The last time this happened (in this case with Linux 5.10.0-rc4), I took some data. >> >> The triggering event seems to be the md_check cron job trying to pause the ongoing check operation in the morning with >> >> echo idle > /sys/devices/virtual/block/md1/md/sync_action >> >> This doesn't complete. Here's /proc/stack of this process: >> >> root@done:~/linux_problems/mdX_raid6_looping/2020-11-27# ps -fp 23333 >> UID PID PPID C STIME TTY TIME CMD >> root 23333 23331 0 02:00 ? 00:00:00 /bin/bash /usr/bin/mdcheck --continue --duration 06:00 >> root@done:~/linux_problems/mdX_raid6_looping/2020-11-27# cat /proc/23333/stack >> [<0>] kthread_stop+0x6e/0x150 >> [<0>] md_unregister_thread+0x3e/0x70 >> [<0>] md_reap_sync_thread+0x1f/0x1e0 >> [<0>] action_store+0x141/0x2b0 >> [<0>] md_attr_store+0x71/0xb0 >> [<0>] kernfs_fop_write+0x113/0x1a0 >> [<0>] vfs_write+0xbc/0x250 >> [<0>] ksys_write+0xa1/0xe0 >> [<0>] do_syscall_64+0x33/0x40 >> [<0>] entry_SYSCALL_64_after_hwframe+0x44/0xa9 >> >> Note, that md0 has been paused successfully just before. > > What is the personality of md0? Is it also raid6?
Yes.
> >> >> 2020-11-27T02:00:01+01:00 done CROND[23333]: (root) CMD (/usr/bin/mdcheck --continue --duration "06:00") >> 2020-11-27T02:00:01+01:00 done root: mdcheck continue checking /dev/md0 from 10623180920 >> 2020-11-27T02:00:01.382994+01:00 done kernel: [378596.606381] md: data-check of RAID array md0 >> 2020-11-27T02:00:01+01:00 done root: mdcheck continue checking /dev/md1 from 11582849320 >> 2020-11-27T02:00:01.437999+01:00 done kernel: [378596.661559] md: data-check of RAID array md1 >> 2020-11-27T06:00:01.842003+01:00 done kernel: [392996.625147] md: md0: data-check interrupted. >> 2020-11-27T06:00:02+01:00 done root: pause checking /dev/md0 at 13351127680 >> 2020-11-27T06:00:02.338989+01:00 done kernel: [392997.122520] md: md1: data-check interrupted. >> [ nothing related following.... ] >> >> After that, we see md1_raid6 in a busy loop: >> >> PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND >> 2376 root 20 0 0 0 0 R 100.0 0.0 1387:38 md1_raid6 > > Seems the reap sync thread was trying to stop md1_raid6 while md1_raid6 was triggered again and again. > >> >> Also, all processes doing I/O do the md device block. >> >> This is /proc/mdstat: >> >> Personalities : [linear] [raid0] [raid1] [raid6] [raid5] [raid4] [multipath] >> md1 : active raid6 sdk[0] sdj[15] sdi[14] sdh[13] sdg[12] sdf[11] sde[10] sdd[9] sdc[8] sdr[7] sdq[6] sdp[5] sdo[4] sdn[3] sdm[2] sdl[1] >> 109394518016 blocks super 1.2 level 6, 512k chunk, algorithm 2 [16/16] [UUUUUUUUUUUUUUUU] >> [==================>..] check = 94.0% (7350290348/7813894144) finish=57189.3min speed=135K/sec >> bitmap: 0/59 pages [0KB], 65536KB chunk >> md0 : active raid6 sds[0] sdah[15] sdag[16] sdaf[13] sdae[12] sdad[11] sdac[10] sdab[9] sdaa[8] sdz[7] sdy[6] sdx[17] sdw[4] sdv[3] sdu[2] sdt[1] >> 109394518016 blocks super 1.2 level 6, 512k chunk, algorithm 2 [16/16] [UUUUUUUUUUUUUUUU] >> bitmap: 0/59 pages [0KB], 65536KB chunk >> > > So the RECOVERY_CHECK flag should be set, not sure if the simple changes > helps, but you may give it a try.
Thanks. I've copied the original condition block to execute before the modified one and added some logging to it to see, if the change actually triggers. I will pause and unpause the check frequently on a busy machine to get this code executed more often.
Best Donald
> > diff --git a/drivers/md/md.c b/drivers/md/md.c > index 98bac4f..e2697d0 100644 > --- a/drivers/md/md.c > +++ b/drivers/md/md.c > @@ -9300,7 +9300,8 @@ void md_check_recovery(struct mddev *mddev) > md_update_sb(mddev, 0); > > if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery) && > - !test_bit(MD_RECOVERY_DONE, &mddev->recovery)) { > + (!test_bit(MD_RECOVERY_DONE, &mddev->recovery) || > + test_bit(MD_RECOVERY_CHECK, &mddev->recovery))) { > /* resync/recovery still happening */ > clear_bit(MD_RECOVERY_NEEDED, &mddev->recovery); > goto unlock; > > Thanks, > Guoqing
-- Donald Buczek buczek@molgen.mpg.de Tel: +49 30 8413 1433
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