From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Farman Subject: [PATCH v2] virtio_scsi: Reject commands when virtqueue is broken Date: Fri, 13 Jan 2017 12:48:06 -0500 Message-ID: <1484329686-21553-2-git-send-email-farman@linux.vnet.ibm.com> References: <1484329686-21553-1-git-send-email-farman@linux.vnet.ibm.com> Return-path: Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:46450 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750795AbdANA1x (ORCPT ); Fri, 13 Jan 2017 19:27:53 -0500 Received: from pps.filterd (m0098413.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.17/8.16.0.17) with SMTP id v0DHhtdi069429 for ; Fri, 13 Jan 2017 12:48:14 -0500 Received: from e18.ny.us.ibm.com (e18.ny.us.ibm.com [129.33.205.208]) by mx0b-001b2d01.pphosted.com with ESMTP id 27y318hb19-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Fri, 13 Jan 2017 12:48:13 -0500 Received: from localhost by e18.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 13 Jan 2017 12:48:13 -0500 In-Reply-To: <1484329686-21553-1-git-send-email-farman@linux.vnet.ibm.com> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: linux-scsi@vger.kernel.org Cc: jejb@linux.vnet.ibm.com, martin.petersen@oracle.com, famz@redhat.com, Eric Farman 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 --- drivers/scsi/virtio_scsi.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c index ec91bd0..c680d76 100644 --- a/drivers/scsi/virtio_scsi.c +++ b/drivers/scsi/virtio_scsi.c @@ -534,7 +534,9 @@ 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); + unsigned long flags; int req_size; + int ret; BUG_ON(scsi_sg_count(sc) > shost->sg_tablesize); @@ -562,8 +564,15 @@ 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; + spin_lock_irqsave(&req_vq->vq_lock, flags); + virtscsi_complete_cmd(vscsi, cmd); + spin_unlock_irqrestore(&req_vq->vq_lock, flags); + } else if (ret != 0) { return SCSI_MLQUEUE_HOST_BUSY; + } return 0; } -- 1.9.1