On Wed, May 06 2015 at 3:45am -0400, Bart Van Assche <bart.vanassche@xxxxxxxxxxx> wrote: > On 05/06/15 04:23, Mike Snitzer wrote: > > On Tue, May 05 2015 at 10:04am -0400, > > Bart Van Assche <bart.vanassche@xxxxxxxxxxx> wrote: > >> While retesting my SRP initiator patches on top of kernel v4.1-rc2 > >> with DM_MQ_DEFAULT=y I ran into the kernel warning below. Does this > >> mean that I'm missing any device mapper related patches ? This > >> warning was reported shortly after scsi_remove_host() had been > >> invoked. > > > > I put the warning in place because, to me, if it triggers it speaks to > > unsafe teardown occuring (request is still completing but the queue it > > was issued from no longer exists). > > > > Like I said before I'm open to removing the WARN_ON_ONCE() if this > > scenario is perfectly valid. But I just haven't had time to revisit > > what appears to be a potentially serious problem with the underlying > > paths' teardown vs upper level mpath IO. > > > > I'll try to revisit this week. But I welcome input from others too. > > > > (Just thinking about it further now, it could be that the way the clone > > request is allocated in the case of blk-mq DM is as part of the original > > request's pdu... meaning there isn't a proper get_request() call against > > the underlying queue.. so the expected refcounting likely isn't > > happening. And given the request won't be free'd from that underlying > > request_queue there really isn't a need to artificially link these > > cloned requests with the underlying request_queue... so I'm now leaning > > toward just removing the WARN_ON_ONCE.. but I'll look closer tomorrow) > > Hello Mike, > > With CONFIG_SCSI_MQ_DEFAULT=y and CONFIG_DM_MQ_DEFAULT=n I just ran into > the bug report below. I will continue my v4.1-rc2 tests with SCSI_MQ=n. What were you doing when this happened? Quite a strange place to get a NULL pointer (it should be noted that for 4.2 hch's patch does away with cloning the request's bios). Is there an easy reproducer (unlikely considering I've tested CONFIG_SCSI_MQ_DEFAULT=y and CONFIG_DM_MQ_DEFAULT=n a fair amount). BTW, my "Just thinking about it further now" above was relative to CONFIG_DM_MQ_DEFAULT=y and CONFIG_SCSI_MQ_DEFAULT=n. Mike -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
