[PATCH v2 07/10] vhost-scsi: log I/O queue write descriptors

[Dongli Zhang <dongli.zhang@oracle.com>]

Log write descriptors for the I/O queue, leveraging vhost_scsi_get_desc()
and vhost_get_vq_desc() to retrieve the array of write descriptors to
obtain the log buffer.

In addition, introduce a vhost-scsi specific function to log vring
descriptors. In this function, the 'partial' argument is set to false, and
the 'len' argument is set to 0, because vhost-scsi always logs all pages
shared by a vring descriptor. Add WARN_ON_ONCE() since vhost-scsi doesn't
support VIRTIO_F_ACCESS_PLATFORM.

Store the log buffer during the submission path and log it in the
completion path. Logging is also required in the error handling path of the
submission process.

Suggested-by: Joao Martins <joao.m.martins@oracle.com>
Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com>
---
Changed since v1:
  - Re-order if staments in vhost_scsi_log_write().
  - Log after vhost_scsi_send_status() as well.

 drivers/vhost/scsi.c | 43 ++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 40 insertions(+), 3 deletions(-)

diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
index 1b7211a55562..8a1b0a19fe58 100644
--- a/drivers/vhost/scsi.c
+++ b/drivers/vhost/scsi.c
@@ -367,6 +367,24 @@ static int vhost_scsi_check_prot_fabric_only(struct se_portal_group *se_tpg)
 	return tpg->tv_fabric_prot_type;
 }
 
+static void vhost_scsi_log_write(struct vhost_virtqueue *vq,
+				 struct vhost_log *log,
+				 unsigned int log_num)
+{
+	if (likely(!vhost_has_feature(vq, VHOST_F_LOG_ALL)))
+		return;
+
+	if (likely(!log_num || !log))
+		return;
+
+	/*
+	 * vhost-scsi doesn't support VIRTIO_F_ACCESS_PLATFORM.
+	 * No requirement for vq->iotlb case.
+	 */
+	WARN_ON_ONCE(unlikely(vq->iotlb));
+	vhost_log_write(vq, log, log_num, 0, false, NULL, 0);
+}
+
 static void vhost_scsi_release_cmd_res(struct se_cmd *se_cmd)
 {
 	struct vhost_scsi_cmd *tv_cmd = container_of(se_cmd,
@@ -665,6 +683,9 @@ static void vhost_scsi_complete_cmd_work(struct vhost_work *work)
 		} else
 			pr_err("Faulted on virtio_scsi_cmd_resp\n");
 
+		vhost_scsi_log_write(cmd->tvc_vq, cmd->tvc_log,
+				     cmd->tvc_log_num);
+
 		vhost_scsi_release_cmd_res(se_cmd);
 	}
 
@@ -1233,6 +1254,8 @@ vhost_scsi_handle_vq(struct vhost_scsi *vs, struct vhost_virtqueue *vq)
 	u8 task_attr;
 	bool t10_pi = vhost_has_feature(vq, VIRTIO_SCSI_F_T10_PI);
 	u8 *cdb;
+	struct vhost_log *vq_log;
+	unsigned int log_num;
 
 	mutex_lock(&vq->mutex);
 	/*
@@ -1248,8 +1271,11 @@ vhost_scsi_handle_vq(struct vhost_scsi *vs, struct vhost_virtqueue *vq)
 
 	vhost_disable_notify(&vs->dev, vq);
 
+	vq_log = unlikely(vhost_has_feature(vq, VHOST_F_LOG_ALL)) ?
+		vq->log : NULL;
+
 	do {
-		ret = vhost_scsi_get_desc(vs, vq, &vc, NULL, NULL);
+		ret = vhost_scsi_get_desc(vs, vq, &vc, vq_log, &log_num);
 		if (ret)
 			goto err;
 
@@ -1398,6 +1424,14 @@ vhost_scsi_handle_vq(struct vhost_scsi *vs, struct vhost_virtqueue *vq)
 			goto err;
 		}
 
+		if (unlikely(vq_log && log_num)) {
+			/*
+			 * cmd->tvc_log depends on VHOST_F_LOG_ALL.
+			 */
+			memcpy(cmd->tvc_log, vq->log, sizeof(*cmd->tvc_log) * log_num);
+			cmd->tvc_log_num = log_num;
+		}
+
 		pr_debug("vhost_scsi got command opcode: %#02x, lun: %d\n",
 			 cdb[0], lun);
 		pr_debug("cmd: %p exp_data_len: %d, prot_bytes: %d data_direction:"
@@ -1433,11 +1467,14 @@ vhost_scsi_handle_vq(struct vhost_scsi *vs, struct vhost_virtqueue *vq)
 		 */
 		if (ret == -ENXIO)
 			break;
-		else if (ret == -EIO)
+		else if (ret == -EIO) {
 			vhost_scsi_send_bad_target(vs, vq, &vc, TYPE_IO_CMD);
-		else if (ret == -ENOMEM)
+			vhost_scsi_log_write(vq, vq_log, log_num);
+		} else if (ret == -ENOMEM) {
 			vhost_scsi_send_status(vs, vq, &vc,
 					       SAM_STAT_TASK_SET_FULL);
+			vhost_scsi_log_write(vq, vq_log, log_num);
+		}
 	} while (likely(!vhost_exceeds_weight(vq, ++c, 0)));
 out:
 	mutex_unlock(&vq->mutex);
-- 
2.39.3