| Message ID | 1484172122-18882-2-git-send-email-farman@linux.vnet.ibm.com (mailing list archive) |
|---|---|
| State | Changes Requested, archived |
| Headers | show |
On Wed, 01/11 17:02, Eric Farman wrote: > In the case of a graceful set of detaches, where the virtio-scsi-ccw > disk is removed from the guest prior to the controller, the guest > behaves quite normally. Specifically, the detach gets us into > sd_sync_cache to issue a Synchronize Cache(10) command, which > immediately fails (and is retried a couple of times) because the > device has been removed. Later, the removal of the controller > sees two CRWs presented, but there's no further indication of the > removal from the guest viewpoint. > > [ 17.217458] sd 0:0:0:0: [sda] Synchronizing SCSI cache > [ 17.219257] sd 0:0:0:0: [sda] Synchronize Cache(10) failed: Result: hostbyte=DID_BAD_TARGET driverbyte=DRIVER_OK > [ 21.449400] crw_info : CRW reports slct=0, oflw=0, chn=1, rsc=3, anc=0, erc=4, rsid=2 > [ 21.449406] crw_info : CRW reports slct=0, oflw=0, chn=0, rsc=3, anc=0, erc=4, rsid=0 > > However, on s390, the SCSI disks can be removed "by surprise" when > an entire controller (host) is removed and all associated disks > are removed via the loop in scsi_forget_host. The same call to > sd_sync_cache is made, but because the controller has already > been removed, the Synchronize Cache(10) command is neither issued > (and then failed) nor rejected. > > That the I/O isn't returned means the guest cannot have other devices > added nor removed, and other tasks (such as shutdown or reboot) issued > by the guest will not complete either. The virtio ring has already > been marked as broken (via virtio_break_device in virtio_ccw_remove), > but we still attempt to queue the command only to have it remain there. > The calling sequence provides a bit of distinction for us: > > virtscsi_queuecommand() > -> virtscsi_kick_cmd() > -> virtscsi_add_cmd() > -> virtqueue_add_sgs() > -> virtqueue_add() > if success > return 0 > elseif vq->broken or vring_mapping_error() > return -EIO > else > return -ENOSPC > > A return of ENOSPC is generally a temporary condition, so returning > "host busy" from virtscsi_queuecommand makes sense here, to have it > redriven in a moment or two. But the EIO return code is more of a > permanent error and so it would be wise to return the I/O itself and > allow the calling thread to finish gracefully. The result is these > four kernel messages in the guest (the fourth one does not occur > prior to this patch): > > [ 22.921562] crw_info : CRW reports slct=0, oflw=0, chn=1, rsc=3, anc=0, erc=4, rsid=2 > [ 22.921580] crw_info : CRW reports slct=0, oflw=0, chn=0, rsc=3, anc=0, erc=4, rsid=0 > [ 22.921978] sd 0:0:0:0: [sda] Synchronizing SCSI cache > [ 22.921993] sd 0:0:0:0: [sda] Synchronize Cache(10) failed: Result: hostbyte=DID_BAD_TARGET driverbyte=DRIVER_OK > > I opted to fill in the same response data that is returned from the > more graceful device detach, where the disk device is removed prior > to the controller device. > > Signed-off-by: Eric Farman <farman@linux.vnet.ibm.com> > --- > drivers/scsi/virtio_scsi.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c > index ec91bd0..78d50ca 100644 > --- a/drivers/scsi/virtio_scsi.c > +++ b/drivers/scsi/virtio_scsi.c > @@ -535,6 +535,7 @@ static int virtscsi_queuecommand(struct virtio_scsi *vscsi, > struct Scsi_Host *shost = virtio_scsi_host(vscsi->vdev); > struct virtio_scsi_cmd *cmd = scsi_cmd_priv(sc); > int req_size; > + int ret; > > BUG_ON(scsi_sg_count(sc) > shost->sg_tablesize); > > @@ -562,8 +563,13 @@ static int virtscsi_queuecommand(struct virtio_scsi *vscsi, > req_size = sizeof(cmd->req.cmd); > } > > - if (virtscsi_kick_cmd(req_vq, cmd, req_size, sizeof(cmd->resp.cmd)) != 0) > + ret = virtscsi_kick_cmd(req_vq, cmd, req_size, sizeof(cmd->resp.cmd)); > + if (ret == -EIO) { > + cmd->resp.cmd.response = VIRTIO_SCSI_S_BAD_TARGET; > + virtscsi_complete_cmd(vscsi, cmd); Is this safe? Calling virtscsi_complete_cmd requires vq_lock but we don't seem to have it here. Fam > + } else if (ret != 0) { > return SCSI_MLQUEUE_HOST_BUSY; > + } > return 0; > } -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 01/11/2017 10:11 PM, Fam Zheng wrote: > On Wed, 01/11 17:02, Eric Farman wrote: >> In the case of a graceful set of detaches, where the virtio-scsi-ccw >> disk is removed from the guest prior to the controller, the guest >> behaves quite normally. Specifically, the detach gets us into >> sd_sync_cache to issue a Synchronize Cache(10) command, which >> immediately fails (and is retried a couple of times) because the >> device has been removed. Later, the removal of the controller >> sees two CRWs presented, but there's no further indication of the >> removal from the guest viewpoint. >> >> [ 17.217458] sd 0:0:0:0: [sda] Synchronizing SCSI cache >> [ 17.219257] sd 0:0:0:0: [sda] Synchronize Cache(10) failed: Result: hostbyte=DID_BAD_TARGET driverbyte=DRIVER_OK >> [ 21.449400] crw_info : CRW reports slct=0, oflw=0, chn=1, rsc=3, anc=0, erc=4, rsid=2 >> [ 21.449406] crw_info : CRW reports slct=0, oflw=0, chn=0, rsc=3, anc=0, erc=4, rsid=0 >> >> However, on s390, the SCSI disks can be removed "by surprise" when >> an entire controller (host) is removed and all associated disks >> are removed via the loop in scsi_forget_host. The same call to >> sd_sync_cache is made, but because the controller has already >> been removed, the Synchronize Cache(10) command is neither issued >> (and then failed) nor rejected. >> >> That the I/O isn't returned means the guest cannot have other devices >> added nor removed, and other tasks (such as shutdown or reboot) issued >> by the guest will not complete either. The virtio ring has already >> been marked as broken (via virtio_break_device in virtio_ccw_remove), >> but we still attempt to queue the command only to have it remain there. >> The calling sequence provides a bit of distinction for us: >> >> virtscsi_queuecommand() >> -> virtscsi_kick_cmd() >> -> virtscsi_add_cmd() >> -> virtqueue_add_sgs() >> -> virtqueue_add() >> if success >> return 0 >> elseif vq->broken or vring_mapping_error() >> return -EIO >> else >> return -ENOSPC >> >> A return of ENOSPC is generally a temporary condition, so returning >> "host busy" from virtscsi_queuecommand makes sense here, to have it >> redriven in a moment or two. But the EIO return code is more of a >> permanent error and so it would be wise to return the I/O itself and >> allow the calling thread to finish gracefully. The result is these >> four kernel messages in the guest (the fourth one does not occur >> prior to this patch): >> >> [ 22.921562] crw_info : CRW reports slct=0, oflw=0, chn=1, rsc=3, anc=0, erc=4, rsid=2 >> [ 22.921580] crw_info : CRW reports slct=0, oflw=0, chn=0, rsc=3, anc=0, erc=4, rsid=0 >> [ 22.921978] sd 0:0:0:0: [sda] Synchronizing SCSI cache >> [ 22.921993] sd 0:0:0:0: [sda] Synchronize Cache(10) failed: Result: hostbyte=DID_BAD_TARGET driverbyte=DRIVER_OK >> >> I opted to fill in the same response data that is returned from the >> more graceful device detach, where the disk device is removed prior >> to the controller device. >> >> Signed-off-by: Eric Farman <farman@linux.vnet.ibm.com> >> --- >> drivers/scsi/virtio_scsi.c | 8 +++++++- >> 1 file changed, 7 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c >> index ec91bd0..78d50ca 100644 >> --- a/drivers/scsi/virtio_scsi.c >> +++ b/drivers/scsi/virtio_scsi.c >> @@ -535,6 +535,7 @@ static int virtscsi_queuecommand(struct virtio_scsi *vscsi, >> struct Scsi_Host *shost = virtio_scsi_host(vscsi->vdev); >> struct virtio_scsi_cmd *cmd = scsi_cmd_priv(sc); >> int req_size; >> + int ret; >> >> BUG_ON(scsi_sg_count(sc) > shost->sg_tablesize); >> >> @@ -562,8 +563,13 @@ static int virtscsi_queuecommand(struct virtio_scsi *vscsi, >> req_size = sizeof(cmd->req.cmd); >> } >> >> - if (virtscsi_kick_cmd(req_vq, cmd, req_size, sizeof(cmd->resp.cmd)) != 0) >> + ret = virtscsi_kick_cmd(req_vq, cmd, req_size, sizeof(cmd->resp.cmd)); >> + if (ret == -EIO) { >> + cmd->resp.cmd.response = VIRTIO_SCSI_S_BAD_TARGET; >> + virtscsi_complete_cmd(vscsi, cmd); > > Is this safe? Calling virtscsi_complete_cmd requires vq_lock but we don't seem > to have it here. Hrm... Didn't notice that, and can't speak to its safety. I had a bit of an I/O workload going to other disks, and things seemed okay, but it was by no means an exhaustive test. I can't use virtscsi_vq_done, which normally handles that acquire/release. It calls virtqueue_get_buf prior to calling virtscsi_complete_cmd, which returns NULL because the virtqueue is broken. Thus, no call to virtscsi_complete_cmd. Can I mock up a wrapping routine that only handles the lock and complete_cmd call, and ignore the virtqueue components that virtscsi_vq_done does? Or do I need to consider that somehow despite it all being broken? Eric > > Fam > >> + } else if (ret != 0) { >> return SCSI_MLQUEUE_HOST_BUSY; >> + } >> return 0; >> } > -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thu, 01/12 08:28, Eric Farman wrote: > > > - if (virtscsi_kick_cmd(req_vq, cmd, req_size, sizeof(cmd->resp.cmd)) != 0) > > > + ret = virtscsi_kick_cmd(req_vq, cmd, req_size, sizeof(cmd->resp.cmd)); > > > + if (ret == -EIO) { > > > + cmd->resp.cmd.response = VIRTIO_SCSI_S_BAD_TARGET; > > > + virtscsi_complete_cmd(vscsi, cmd); > > > > Is this safe? Calling virtscsi_complete_cmd requires vq_lock but we don't seem > > to have it here. > > Hrm... Didn't notice that, and can't speak to its safety. I had a bit of > an I/O workload going to other disks, and things seemed okay, but it was by > no means an exhaustive test. > > I can't use virtscsi_vq_done, which normally handles that acquire/release. > It calls virtqueue_get_buf prior to calling virtscsi_complete_cmd, which > returns NULL because the virtqueue is broken. Thus, no call to > virtscsi_complete_cmd. > > Can I mock up a wrapping routine that only handles the lock and complete_cmd > call, and ignore the virtqueue components that virtscsi_vq_done does? That sounds good to me, taking the vq_lock here around the call to virtscsi_complete_cmd, just like virtscsi_kick_cmd(). Fam > > Eric > > > > > Fam > > > > > + } else if (ret != 0) { > > > return SCSI_MLQUEUE_HOST_BUSY; > > > + } > > > return 0; > > > } > > > -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 01/12/2017 08:45 AM, Fam Zheng wrote: > On Thu, 01/12 08:28, Eric Farman wrote: >>>> - if (virtscsi_kick_cmd(req_vq, cmd, req_size, sizeof(cmd->resp.cmd)) != 0) >>>> + ret = virtscsi_kick_cmd(req_vq, cmd, req_size, sizeof(cmd->resp.cmd)); >>>> + if (ret == -EIO) { >>>> + cmd->resp.cmd.response = VIRTIO_SCSI_S_BAD_TARGET; >>>> + virtscsi_complete_cmd(vscsi, cmd); >>> >>> Is this safe? Calling virtscsi_complete_cmd requires vq_lock but we don't seem >>> to have it here. >> >> Hrm... Didn't notice that, and can't speak to its safety. I had a bit of >> an I/O workload going to other disks, and things seemed okay, but it was by >> no means an exhaustive test. >> >> I can't use virtscsi_vq_done, which normally handles that acquire/release. >> It calls virtqueue_get_buf prior to calling virtscsi_complete_cmd, which >> returns NULL because the virtqueue is broken. Thus, no call to >> virtscsi_complete_cmd. >> >> Can I mock up a wrapping routine that only handles the lock and complete_cmd >> call, and ignore the virtqueue components that virtscsi_vq_done does? > > That sounds good to me, taking the vq_lock here around the call to > virtscsi_complete_cmd, just like virtscsi_kick_cmd(). Okay, working up a v2 today. Thanks! Eric > > Fam > >> >> Eric >> >>> >>> Fam >>> >>>> + } else if (ret != 0) { >>>> return SCSI_MLQUEUE_HOST_BUSY; >>>> + } >>>> return 0; >>>> } >>> >> > -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c index ec91bd0..78d50ca 100644 --- a/drivers/scsi/virtio_scsi.c +++ b/drivers/scsi/virtio_scsi.c @@ -535,6 +535,7 @@ static int virtscsi_queuecommand(struct virtio_scsi *vscsi, struct Scsi_Host *shost = virtio_scsi_host(vscsi->vdev); struct virtio_scsi_cmd *cmd = scsi_cmd_priv(sc); int req_size; + int ret; BUG_ON(scsi_sg_count(sc) > shost->sg_tablesize); @@ -562,8 +563,13 @@ static int virtscsi_queuecommand(struct virtio_scsi *vscsi, req_size = sizeof(cmd->req.cmd); } - if (virtscsi_kick_cmd(req_vq, cmd, req_size, sizeof(cmd->resp.cmd)) != 0) + ret = virtscsi_kick_cmd(req_vq, cmd, req_size, sizeof(cmd->resp.cmd)); + if (ret == -EIO) { + cmd->resp.cmd.response = VIRTIO_SCSI_S_BAD_TARGET; + virtscsi_complete_cmd(vscsi, cmd); + } else if (ret != 0) { return SCSI_MLQUEUE_HOST_BUSY; + } return 0; }
In the case of a graceful set of detaches, where the virtio-scsi-ccw disk is removed from the guest prior to the controller, the guest behaves quite normally. Specifically, the detach gets us into sd_sync_cache to issue a Synchronize Cache(10) command, which immediately fails (and is retried a couple of times) because the device has been removed. Later, the removal of the controller sees two CRWs presented, but there's no further indication of the removal from the guest viewpoint. [ 17.217458] sd 0:0:0:0: [sda] Synchronizing SCSI cache [ 17.219257] sd 0:0:0:0: [sda] Synchronize Cache(10) failed: Result: hostbyte=DID_BAD_TARGET driverbyte=DRIVER_OK [ 21.449400] crw_info : CRW reports slct=0, oflw=0, chn=1, rsc=3, anc=0, erc=4, rsid=2 [ 21.449406] crw_info : CRW reports slct=0, oflw=0, chn=0, rsc=3, anc=0, erc=4, rsid=0 However, on s390, the SCSI disks can be removed "by surprise" when an entire controller (host) is removed and all associated disks are removed via the loop in scsi_forget_host. The same call to sd_sync_cache is made, but because the controller has already been removed, the Synchronize Cache(10) command is neither issued (and then failed) nor rejected. That the I/O isn't returned means the guest cannot have other devices added nor removed, and other tasks (such as shutdown or reboot) issued by the guest will not complete either. The virtio ring has already been marked as broken (via virtio_break_device in virtio_ccw_remove), but we still attempt to queue the command only to have it remain there. The calling sequence provides a bit of distinction for us: virtscsi_queuecommand() -> virtscsi_kick_cmd() -> virtscsi_add_cmd() -> virtqueue_add_sgs() -> virtqueue_add() if success return 0 elseif vq->broken or vring_mapping_error() return -EIO else return -ENOSPC A return of ENOSPC is generally a temporary condition, so returning "host busy" from virtscsi_queuecommand makes sense here, to have it redriven in a moment or two. But the EIO return code is more of a permanent error and so it would be wise to return the I/O itself and allow the calling thread to finish gracefully. The result is these four kernel messages in the guest (the fourth one does not occur prior to this patch): [ 22.921562] crw_info : CRW reports slct=0, oflw=0, chn=1, rsc=3, anc=0, erc=4, rsid=2 [ 22.921580] crw_info : CRW reports slct=0, oflw=0, chn=0, rsc=3, anc=0, erc=4, rsid=0 [ 22.921978] sd 0:0:0:0: [sda] Synchronizing SCSI cache [ 22.921993] sd 0:0:0:0: [sda] Synchronize Cache(10) failed: Result: hostbyte=DID_BAD_TARGET driverbyte=DRIVER_OK I opted to fill in the same response data that is returned from the more graceful device detach, where the disk device is removed prior to the controller device. Signed-off-by: Eric Farman <farman@linux.vnet.ibm.com> --- drivers/scsi/virtio_scsi.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)