Messages in this thread | | | From | MasterPrenium <> | Subject | Re: PROBLEM: Kernel BUG with raid5 soft + Xen + DRBD - invalid opcode | Date | Tue, 17 Jan 2017 02:54:06 +0100 |
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Hi Shaohua,
I've made some new little tests, maybe it can help.
- I tried creating the RAID 5 stack with only 2 drives (mdadm --create /dev/md10 --raid-devices=3 --level=5 /dev/sdc1 /dev/sdd1 missing). The same issue is happening. - but one time (still with 2/3 drives), I was not able to crash the kernel, with exactly the same procedure as previous. Even with re-creating filesystems ect. In order to re-produce the BUG I had to re-create the array.
Can this be linked to this message ? : [ 155.667456] md10: Warning: Device sdc1 is misaligned
I don't know how to "align" a drive in a RAID stack... The partition is correctly align (as "parted" says).
- In another test (still 2/3 drives in the stack), I didn't got the kernel crash, but I had 100% io wait on cpu. Trying to reboot, finally give me this printk messages : http://pastebin.com/uzVHUUrC
If you have any patch to give me (maybe something to be more verbose about the issue), please tell me, I'll test it as it's a really blocking issue...
Best regards,
MasterPrenium
Le 09/01/2017 à 23:44, Shaohua Li a écrit : > On Sun, Jan 08, 2017 at 02:31:15PM +0100, MasterPrenium wrote: >> Hello, >> >> Replies below + : >> - I don't know if this can help but after the crash, when the system >> reboots, the Raid 5 stack is re-synchronizing >> [ 37.028239] md10: Warning: Device sdc1 is misaligned >> [ 37.028541] created bitmap (15 pages) for device md10 >> [ 37.030433] md10: bitmap initialized from disk: read 1 pages, set 59 of >> 29807 bits >> >> - Sometimes the kernel completely crash (lost serial + network connection), >> sometimes only got the "BUG" dump, but still have network access (but a >> reboot is impossible, need to reset the system). >> >> - You can find blktrace here (while running fio), I hope it's complete since >> the end of the file is when the kernel crashed : https://goo.gl/X9jZ50 > Looks most are normal full stripe writes. > >>> I'm trying to reproduce, but no success. So >>> ext4->btrfs->raid5, crash >>> btrfs->raid5, no crash >>> right? does subvolume matter? When you create the raid5 array, does adding >>> '--assume-clean' option change the behavior? I'd like to narrow down the issue. >>> If you can capture the blktrace to the raid5 array, it would be great to hint >>> us what kind of IO it is. >> Yes Correct. >> The subvolume doesn't matter. >> -- assume-clean doesn't change the behaviour. > so it's not a resync issue. > >> Don't forget that the system needs to be running on xen to crash, without >> (on native kernel) it doesn't crash (or at least, I was not able to make it >> crash). >>>> Regarding your patch, I can't find it. Is it the one sent by Konstantin >>>> Khlebnikov ? >>> Right. >> It doesn't help :(. Maybe the crash is happening a little bit later. > ok, the patch is unlikely helpful, since the IO size isn't very big. > > Don't have good idea yet. My best guess so far is virtual machine introduces > extra delay, which might trigger some race conditions which aren't seen in > native. I'll check if I could find something locally. > > Thanks, > Shaohua
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