On 26.08.20 09:48, Martin Kepplinger wrote: > On 24.08.20 22:13, Alan Stern wrote: >> On Mon, Aug 24, 2020 at 10:48:32AM -0700, Bart Van Assche wrote: >>> On 2020-08-23 07:57, Alan Stern wrote: >>>> The problem is fixed by checking that the queue's runtime-PM status >>>> isn't RPM_SUSPENDED before allowing a request to be issued, [ ... ] >>> >>> Reviewed-by: Bart Van Assche <bvanassche@xxxxxxx> >>> >>> Can, can you help with testing this patch? >>> >>> Thanks, >>> >>> Bart. >> >> Martin: >> >> (I forgot to ask this question several weeks ago, while you were running >> your tests. Better ask it now before I forget again...) >> >> I suspect the old runtime-PM code in the block layer would have worked >> okay in your SD cardreader test if the BLK_MQ_REQ_PREEMPT flag had not >> been set. Do you know why the flag was set, or what line of code caused >> it to be set? > > Correct. if not set, I could handle all I need in the scsi error path. this thread becomes a bit confusing. I thought about REQ_FAILFAST_DEV but you're talking about something different. the only place I see BLK_MQ_REQ_PREEMPT getting passed on is in __scsi_execute() which is the case when mounting/unmounting. At least that about the only place I can find. I remember *only* your block pm fix would let me mount/unmount, but not use files yet (REQ_FAILFAST_DEV and so on). When I revert your fix and remove BLK_MQ_REQ_PREEMPT from being passed on to blk_get_request() in __scsi_execute(), that line gets executed exactly once during startup and I'm missing the /dev/sda device from the cardreader then. Is this what you're asking? > >> >> As I recall, the request that failed was a read-ahead. It's not clear >> to me why such a request would need to have BLK_MQ_REQ_PREEMPT set. >> Although there may be other reasons for having that flag, at this point >> we're concerned with requests that are part of the runtime-resume >> procedure. A read-ahead does not fall into that category. >> >> Do you think you can find the answer? Perhaps we should add a separate >> BLK_MQ_REQ_PM flag.
