James Bottomley <jejb@xxxxxxxxxxxxxxxxxx> writes:
> On Thu, 2016-10-13 at 15:47 -0300, Gabriel Krisman Bertazi wrote:
>> @@ -210,6 +219,13 @@ int scsi_execute(struct scsi_device *sdev, const
>> unsigned char *cmd,
>> */
>> blk_execute_rq(req->q, NULL, req, 1);
>>
>> + if (scsi_sense_unit_attention(sense) && req->retries > 0) {
>> + memset(sense, 0, SCSI_SENSE_BUFFERSIZE);
>> + retries = req->retries - 1;
>> + blk_put_request(req);
>> + goto retry;
>> + }
>
> OK, so this is more theory, but I think you can actually reuse the same
> request to go around this loop without doing a get/put. I've cc'd Jens
> to confirm, since no other driver I can find does this, but if it's
> legal, it saves freeing and reallocating the request. You can then
> replace the goto with a do { } while (...) which makes the loop obvious
> to the next person looking at this.
Hi James,
I don't think the block layer currently has the machinery to reuse the
request. I think it would be easy to add for the MQ case but I
don't know about SQ. If we don't clean up or reinit the request before
re-sending, we'll hit the BUG_ON in blk_start_request:
BUG_ON(test_bit(REQ_ATOM_COMPLETE, &req->atomic_flags));
Do you wanna take a v3 of the patch and fix this on a future patch, or
should I be looking into patching the block layer interface? I'll be
looking into it, but I need to get familiar with the SQ code first.
--
Gabriel Krisman Bertazi
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