Re: [PATCH v13 05/18] scsi: core: Introduce a mechanism for reordering requests in the error handler

[Bart Van Assche <bvanassche@acm.org>]

On 10/19/23 10:53, Bart Van Assche wrote:
> 
> On 10/18/23 17:24, Damien Le Moal wrote:
>> On 10/19/23 02:54, Bart Van Assche wrote:
>>> +void scsi_call_prepare_resubmit(struct list_head *done_q)
>>> +{
>>> +    struct scsi_cmnd *scmd, *next;
>>> +
>>> +    if (!scsi_needs_preparation(done_q))
>>> +        return;
>>
>> This function will always go through the list of commands in done_q. 
>> That could
>> hurt performance for scsi hosts that do not need this prepare 
>> resubmit, which I
>> think is UFS only for now. So can't we just add a flag or something to 
>> avoid that ?
>
> The SCSI error handler is only invoked after an RCU grace period has 
> expired. The time spent in scsi_needs_preparation() is negligible
> compared to an RCU grace period, especially if the
> .eh_needs_prepare_resubmit pointers are NULL.

(replying to my own e-mail)

Do you perhaps want me to drop the eh_needs_prepare_resubmit function
pointer and introduce a flag instead? That sounds good to me.

Thanks,

Bart.