[dm-devel] dm: snapshot: I/O error failure in xfstests generic/081

[Ming Lei]

On Thu, Mar 24, 2016 at 9:25 PM, Mike Snitzer <snitzer at redhat.com> wrote:
> On Thu, Mar 24 2016 at  8:23am -0400,
> Ming Lei <ming.lei at canonical.com> wrote:
>
>> Hi,
>>
>> When I run xfstests generic/081 over virtio-scsi, loop or virtio-blk,
>> the following snapshot error and IO failure is alwasy observed in
>> linus v4.5+.
>
> The only snapshot specific changes that went into 4.5+ are:
>
> 385277b dm snapshot: fix hung bios when copy error occurs
> 808e621 dm snapshot: disallow the COW and origin devices from being identical
>
> Neither of which should result in "Unable to allocate exception" due to
> -ENOMEM.
>
> But commit 385277b does touch relevant code-paths though so you might
> try reverting it and see if your problem goes away.
>
> If that doesn't help then you'll have to do a bisect.

I don't know where to start the bisect, and looks v4.0 has
the issue too.

Thanks,

>
> Mike
>
>> [1], dmesg log
>> [  374.794520] EXT4-fs (dm-3): mounted filesystem with ordered data
>> mode. Opts: (null)
>> [  392.894924] device-mapper: snapshots: Invalidating snapshot: Unable
>> to allocate exception.
>> [  392.904760] EXT4-fs warning (device dm-3): ext4_end_bio:314: I/O
>> error -5 writing to inode 12 (offset 4194304 size 1048576 starting
>> block 14337)
>> [  392.905336] EXT4-fs warning (device dm-3): ext4_end_bio:314: I/O
>> error -5 writing to inode 12 (offset 0 size 2097152 starting block
>> 10241)
>> [  392.905340] Buffer I/O error on device dm-3, logical block 10241
>> [  392.905342] Buffer I/O error on device dm-3, logical block 10242
>> [  392.905343] Buffer I/O error on device dm-3, logical block 10243
>> [  392.905345] Buffer I/O error on device dm-3, logical block 10244
>> [  392.905349] Buffer I/O error on device dm-3, logical block 10245
>> [  392.905351] Buffer I/O error on device dm-3, logical block 10246
>> [  392.905352] Buffer I/O error on device dm-3, logical block 10247
>> [  392.905353] Buffer I/O error on device dm-3, logical block 10248
>> [  392.905355] Buffer I/O error on device dm-3, logical block 10249
>> [  392.905357] Buffer I/O error on device dm-3, logical block 10250
>> [  392.906708] EXT4-fs warning (device dm-3): ext4_end_bio:314: I/O
>> error -5 writing to inode 12 (offset 0 size 2097152 starting block
>> 11265)
>> [  392.949341] EXT4-fs warning (device dm-3): ext4_end_bio:314: I/O
>> error -5 writing to inode 12 (offset 2097152 size 2097152 starting
>> block 12289)
>> [  392.956143] EXT4-fs warning (device dm-3): ext4_end_bio:314: I/O
>> error -5 writing to inode 12 (offset 2097152 size 2097152 starting
>> block 13313)