Re: raid5 crash on system which PAGE_SIZE is 64KB

[Xiao Ni <xni@redhat.com>]

On 03/23/2021 01:28 AM, Song Liu wrote:
> On Tue, Mar 16, 2021 at 2:20 AM Yufen Yu <yuyufen@huawei.com> wrote:
>>
>>
>> On 2021/3/15 21:44, Xiao Ni wrote:
>>> Hi all
>>>
>>> We encounter one raid5 crash problem on POWER system which PAGE_SIZE is 64KB.
>>> I can reproduce this problem 100%.  This problem can be reproduced with latest upstream kernel.
>>>
>>> The steps are:
>>> mdadm -CR /dev/md0 -l5 -n3 /dev/sda1 /dev/sdc1 /dev/sdd1
>>> mkfs.xfs /dev/md0 -f
>>> mount /dev/md0 /mnt/test
>>>
>>> The error message is:
>>> mount: /mnt/test: mount(2) system call failed: Structure needs cleaning.
>>>
>>> We can see error message in dmesg:
>>> [ 6455.761545] XFS (md0): Metadata CRC error detected at xfs_agf_read_verify+0x118/0x160 [xfs], xfs_agf block 0x2105c008
>>> [ 6455.761570] XFS (md0): Unmount and run xfs_repair
>>> [ 6455.761575] XFS (md0): First 128 bytes of corrupted metadata buffer:
>>> [ 6455.761581] 00000000: fe ed ba be 00 00 00 00 00 00 00 02 00 00 00 00  ................
>>> [ 6455.761586] 00000010: 00 00 00 00 00 00 03 c0 00 00 00 01 00 00 00 00  ................
>>> [ 6455.761590] 00000020: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>>> [ 6455.761594] 00000030: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>>> [ 6455.761598] 00000040: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>>> [ 6455.761601] 00000050: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>>> [ 6455.761605] 00000060: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>>> [ 6455.761609] 00000070: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>>> [ 6455.761662] XFS (md0): metadata I/O error in "xfs_read_agf+0xb4/0x1a0 [xfs]" at daddr 0x2105c008 len 8 error 74
>>> [ 6455.761673] XFS (md0): Error -117 recovering leftover CoW allocations.
>>> [ 6455.761685] XFS (md0): Corruption of in-memory data detected. Shutting down filesystem
>>> [ 6455.761690] XFS (md0): Please unmount the filesystem and rectify the problem(s)
>>>
>>> This problem doesn't happen when creating raid device with --assume-clean. So the crash only happens when sync and normal
>>> I/O write at the same time.
>>>
>>> I tried to revert the patch set "Save memory for stripe_head buffer" and the problem can be fixed. I'm looking at this problem,
>>> but I haven't found the root cause. Could you have a look?
>> Thanks for reporting this bug. Please give me some times to debug it,
>> recently time is very limited for me.
>>
>> Thanks,
>> Yufen
> Hi Yufen,
>
> Have you got time to look into this?
>
>>> By the way, there is a place that I can't understand. Is it a bug? Should we do in this way:
>>> diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
>>> index 5d57a5b..4a5e8ae 100644
>>> --- a/drivers/md/raid5.c
>>> +++ b/drivers/md/raid5.c
>>> @@ -1479,7 +1479,7 @@ static struct page **to_addr_page(struct raid5_percpu *percpu, int i)
>>>    static addr_conv_t *to_addr_conv(struct stripe_head *sh,
>>>                                    struct raid5_percpu *percpu, int i)
>>>    {
>>> -       return (void *) (to_addr_page(percpu, i) + sh->disks + 2);
>>> +       return (void *) (to_addr_page(percpu, i) + sizeof(struct page*)*(sh->disks + 2));
> I guess we don't need this change. to_add_page() returns "struct page **", which
> should have same size of "struct page*", no?

You are right. We don't need to change this. And I'm looking at this 
problem too.
I'll report once I find new hints.

Regards
Xiao