On Tue, Feb 26, 2019 at 8:23 PM Hannes Reinecke <hare@xxxxxxx> wrote: > > On 2/26/19 3:33 PM, Christoph Hellwig wrote: > > On Tue, Feb 26, 2019 at 02:49:30PM +0100, Hannes Reinecke wrote: > >> Attached is a patch to demonstrate my approach. > >> I am aware that it'll only be useful for latest upstream where the legacy > >> I/O path has been dropped completely, so we wouldn't need to worry about it. > >> For older releases indeed you would need to with something like your > >> proposed patch, but for upstream I really would like to switch to > >> blk_mq_tagset_busy() iter. > > > > While this is better than the driver private tracking we really should > > not have to iterate all outstanding command, because if we have any > > there is a bug we need to fix in the higher layers instead of working > > around it in the drivers. Hi Chris, Looking at other driver's code, I think similar issue is impacted to many scsi hbas (like fnic, qla4xxx, snic etc..). They also need similar logic to traverse outstanding scsi commands. One of the example is - At the time of HBA reset driver would like to release scsi command back to SML to retry and for that driver requires to loop all possible smid to figure out outstanding scsi command @Firmware/SML level. > > > Ah-ha. > > But what else should we be doing here? > The driver needs to abort all outstanding commands; I somewhat fail to > see how we could be doing it otherwise ... Hannes, Primary drawback of using "blk_mq_tagset_busy_iter" is API is only for blk-mq and it is not available for all the kernel with blk-mq support. We have seen multiple failures from customer and those kernels does not support blk_mq_tagset_busy_iter. In fact, blk-mq and non-mq stack is alive in many Linux distribution and customer is using those. If we just scope to fix current kernel 5.x (which does not have non-mq support), we can opt blk_mq_tagset_busy_iter(). Earlier I requested upstream to accept driver changes without blk_mq_tagset_busy_iter() because it is hitting many customers so we are looking for generic fix which can server both blk-mq as well as non-mq. We will certainly enhance and optimize working this area (driver trying to find outstanding scsi command) with scsi mailing list as incremental approach. Kashyap > > Cheers, > > Hannes >
