> -----Original Message----- > From: James Bottomley [mailto:James.Bottomley@xxxxxxxxxxxxxxxxxxxxx] > Sent: Friday, January 8, 2016 11:21 AM > To: KY Srinivasan <kys@xxxxxxxxxxxxx>; gregkh@xxxxxxxxxxxxxxxxxxx; linux- > kernel@xxxxxxxxxxxxxxx; devel@xxxxxxxxxxxxxxxxxxxxxx; ohering@xxxxxxxx; > jbottomley@xxxxxxxxxxxxx; hch@xxxxxxxxxxxxx; linux-scsi@xxxxxxxxxxxxxxx; > apw@xxxxxxxxxxxxx; vkuznets@xxxxxxxxxx; jasowang@xxxxxxxxxx; > martin.petersen@xxxxxxxxxx; hare@xxxxxxx > Cc: stable@xxxxxxxxxxxxxxx > Subject: Re: [PATCH 1/1] scsi: scsi_transport_fc: Fix a bug in the error > handling function > > On Fri, 2016-01-08 at 18:58 +0000, KY Srinivasan wrote: > > > > > -----Original Message----- > > > From: James Bottomley > [mailto:James.Bottomley@xxxxxxxxxxxxxxxxxxxxx > > > ] > > > Sent: Thursday, January 7, 2016 3:49 PM > > > To: KY Srinivasan <kys@xxxxxxxxxxxxx>; gregkh@xxxxxxxxxxxxxxxxxxx; > > > linux- > > > kernel@xxxxxxxxxxxxxxx; devel@xxxxxxxxxxxxxxxxxxxxxx; > > > ohering@xxxxxxxx; > > > jbottomley@xxxxxxxxxxxxx; hch@xxxxxxxxxxxxx; > > > linux-scsi@xxxxxxxxxxxxxxx; > > > apw@xxxxxxxxxxxxx; vkuznets@xxxxxxxxxx; jasowang@xxxxxxxxxx; > > > martin.petersen@xxxxxxxxxx; hare@xxxxxxx > > > Cc: stable@xxxxxxxxxxxxxxx > > > Subject: Re: [PATCH 1/1] scsi: scsi_transport_fc: Fix a bug in the > > > error > > > handling function > > > > > > On Thu, 2016-01-07 at 16:40 -0800, K. Y. Srinivasan wrote: > > > > The macro startget_to_rport() can return NULL; handle that case > > > > properly. > > > > > > OK, can we unwind why you think you could possibly need this? It > > > would > > > mean that fc_timed_out was called for a non-FC device, which was > > > thought to be an impossibility when the fc transport class was > > > designed. > > > > As you know, on Hyper-V, FC devices are handled exactly like normal > > scsi devices and the only additional information that is provided for > > FC devices is the WWN for port and node. Till recently, I was not > > publishing the WWN in the guest and so I was not even using the FC > > transport. Recently, I implemented support for publishing the WWN in > > the guest and for that I am using the FC transport for FC hosts. When > > an FC LUN is dynamically removed, sometimes I see the timeout occurri > > ng and since there is no rport associated with these devices I am > > hitting the issue this patch is addressing. I could have addressed > > this problem by establishing a storvsc specific time out function > > even for FC devices - the same timeout function that I currently use > > for scsi devices - storvsc_eh_timed_out(). I chose to instead fix > > the fc_timed_out() function since the code was not handling a > > possible condition. > > OK, so the specific problem is that the device is partly torn down when > the timeout fires? I'm having a hard time seeing how we get a null > rport in that case. The starget_to_rport() can only return NULL if the > parent isn't an rport ... that shouldn't depend on the state of the FC > device because the parent is torn down after the child. In our case, the parent is not an rport since I don't invoke fc_remote_port_add() and so I do get a NULL value from the starget_to_rport(). > > In any case, returning BLK_EH_RESET_TIMER will cause all sorts of > problems because it resets the timer to fire again for the device. > What you want is something to return BLK_EH_HANDLED which will just > complete the request ... probably at a generic level, since this > doesn't sound to be specific to FC. On Hyper-V, the host implements a variety of recovery strategies and for that reason, the eh_timed_out handler for standard scsi devices will effectively have infinite timeout value: storvsc_eh_timed_out() just resets the timer. This is the behavior I wanted for the FC devices as well. K. Y > > Something like the below ... assuming the teardown issue is the real > problem. > > James > > --- > > diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c > index 984ddcb..3c514c6 100644 > --- a/drivers/scsi/scsi_error.c > +++ b/drivers/scsi/scsi_error.c > @@ -273,6 +273,10 @@ enum blk_eh_timer_return scsi_times_out(struct > request *req) > enum blk_eh_timer_return rtn = BLK_EH_NOT_HANDLED; > struct Scsi_Host *host = scmd->device->host; > > + /* timeout for an already dead device, just kill the request */ > + if (scmd->device->sdev_state == SDEV_DEL) > + return BLK_EH_HANDLED; > + > trace_scsi_dispatch_cmd_timeout(scmd); > scsi_log_completion(scmd, TIMEOUT_ERROR); > _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
