[stgt] help tgt segfault

[Tomasz Chmielewski]

Tomasz Chmielewski schrieb:
> FUJITA Tomonori schrieb:
>> On Wed, 17 Dec 2008 18:51:41 +0100
>> Tomasz Chmielewski <mangoo at wpkg.org> wrote:
>>
>>> FUJITA Tomonori schrieb:
>>>
>>>> Can you try one more time with this patch (including the previous
>>>> patch so please do git-reset --hard first).
>>> Here you are:
>>>
>>> Dec 17 18:46:27 megathecus tgtd: Target daemon logger with pid=21048 
>>> started!
>>
>> Thanks a lot! This is very useful.
>>
>> Can you try this again? Even if tgtd doesn't crash, please send the
>> log.
> 
> I couldn't crash it any more.
> 
> Here is a lengthy log for 25 minutes - with several device 
> suspends/resumes.
> I'll give it 2 more hours testing...

Not 2 hours, but some observations - is it possible that tgtd serves 
wrong data to the initiator when the access to the media is slow?

During the suspend/resume cycle on the target and dd if=/dev/iscsi_disk 
on the initiator, I got some errors:

# dd if=/dev/sdb of=/dev/null
dd: reading `/dev/sdb': Input/output error
1506128+0 records in
1506128+0 records out
771137536 bytes (771 MB) copied, 555.773 seconds, 1.4 MB/s

# dmesg
<lots of connection errors / host resets>
  connection1:0: iscsi: detected conn error (1011)
iscsi: host reset succeeded
  connection2:0: iscsi: detected conn error (1011)
iscsi: host reset succeeded
sd 3:0:0:1: [sdb] Result: hostbyte=0x02 driverbyte=0x00
end_request: I/O error, dev sdb, sector 1506384
Buffer I/O error on device sdb, logical block 188298
Buffer I/O error on device sdb, logical block 188299
Buffer I/O error on device sdb, logical block 188300
Buffer I/O error on device sdb, logical block 188301
Buffer I/O error on device sdb, logical block 188302
Buffer I/O error on device sdb, logical block 188303
Buffer I/O error on device sdb, logical block 188304
Buffer I/O error on device sdb, logical block 188305
Buffer I/O error on device sdb, logical block 188306
Buffer I/O error on device sdb, logical block 188307
sd 3:0:0:1: [sdb] Result: hostbyte=0x02 driverbyte=0x00
end_request: I/O error, dev sdb, sector 1506136
sd 3:0:0:1: [sdb] Result: hostbyte=0x02 driverbyte=0x00
end_request: I/O error, dev sdb, sector 1506128
  connection2:0: iscsi: detected conn error (1011)
iscsi: host reset succeeded



I had the exactly same issue (I/O errors) when tgtd:
- is accessing a DRBD device (a device replicated over network)
- DRBD device is being synchronized (over a slow, 2 Mbit internet link), 
using the whole bandwidth
- any writes (needing replication over network) done by the initiator 
will be very slow, because of the ongoing sync and slow link


-- 
Tomasz Chmielewski
http://wpkg.org
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