On Tue, Feb 2, 2010 at 6:47 AM, Mike Christie <micha...@cs.wisc.edu> wrote:
> On 02/01/2010 01:21 PM, Mike Christie wrote:
>> On 02/01/2010 11:52 AM, Mike Christie wrote:
>>> On 02/01/2010 05:14 AM, Erez Zilber wrote:
>>>> When iscsi_eh_cmd_timed_out gets called, we can ask scsi-ml to give us
>>>> more time if the cmd is making progress (i.e. if there was some data
>>>> transfer since the last timeout).
>>>> The problem is that task->last_xfer& task->last_timeout are set to
>>>> the value of 'jiffies' when allocating the task. If the target machine
>>>> is already dead when we send the cmd, no progress will be made. Still,
>>>> when iscsi_eh_cmd_timed_out will be called, it will think that data
>>>> was sent since the last timeout and reset the timer (and waste time).
>>>> In order to solve that, iscsi_eh_cmd_timed_out should also check if
>>>> there was any data transfer after the task was allocated.
>>> I agree it is a problem with the code.
>>> The problem is that the check also handled the case where we are so
>>> backed up that we cannot even send a cmd/data within the cmd timeout.
>>> For that case, the check was giving it a extra cmd timeout seconds to
>>> get it off. That code is not really good though. It should probably just
>>> loop over all the cmds there and see if any cmds have made progress. If
>>> so give the cmd more time, if not then fail.
>>> I was not sure though if I should check if any cmds to the target made
>>> progress or if any cmds to the same disk. It could be that just one disk
>>> went bad, so we might want to check per disk. However, this could be the
>>> first IO to the disk and it just got stuck behind a bunch of other IO to
>>> other disks, so in that case we want to check per target.
>> Give me until tomorrow. I think I can cook up patch. Before when
>> deciding when to check for dev vs target, I was mixed up with some
>> reordering stuff, but I think I have a patch that should work for both
>> of us.
> I think the attached patch should do what we both want.
> Instead of always waiting an extra cmd timeout seconds, we will only get
> extra time if:
> 1. The command has made progress. (changed test to time_after)
> 2. Commands queued before the timed out one have made transfers since we
> started the task or since it last timedout.
> Patch was made over scsi-misc.

Looks okay to me.


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