Linux Virtualization - Mar 2013 - [PATCH V2 0/3] tcm_vhost pending requests flush

Changes in v2:
- Increase/Decrease inflight requests in
  vhost_scsi_{allocate,free}_cmd and tcm_vhost_{allocate,free}_evt

Asias He (3):
  tcm_vhost: Wait for pending requests in vhost_scsi_flush()
  tcm_vhost: Wait for pending requests in vhost_scsi_clear_endpoint()
  tcm_vhost: Fix tv_cmd leak in vhost_scsi_handle_vq

 drivers/vhost/tcm_vhost.c | 131 ++++++++++++++++++++++++++++++++++++++--------
 drivers/vhost/tcm_vhost.h |   4 ++
 2 files changed, 112 insertions(+), 23 deletions(-)

-- 
1.8.1.4

This patch makes vhost_scsi_flush() wait for all the pending requests
issued before the flush operation to be finished.

Signed-off-by: Asias He <asias at redhat.com>
---
 drivers/vhost/tcm_vhost.c | 117 ++++++++++++++++++++++++++++++++++++++--------
 drivers/vhost/tcm_vhost.h |   4 ++
 2 files changed, 101 insertions(+), 20 deletions(-)

diff --git a/drivers/vhost/tcm_vhost.c b/drivers/vhost/tcm_vhost.c
index e734ead..dc0af52 100644
--- a/drivers/vhost/tcm_vhost.c
+++ b/drivers/vhost/tcm_vhost.c
@@ -82,6 +82,15 @@ struct vhost_scsi {
 
 	bool vs_events_dropped; /* any missed events, protected by dev.mutex */
 	u64 vs_events_nr; /* num of pending events, protected by dev.mutex */
+
+	/*
+	 * vs_inflight[0]/[1] are used to track requests issued
+	 * before/during the flush operation
+	 */
+	u64 vs_inflight[2];
+	wait_queue_head_t vs_flush_wait; /* wait queue for flush operation */
+	spinlock_t vs_flush_lock; /* lock to protect vs_during_flush */
+	int vs_during_flush; /* flag to indicate if we are in flush operation */
 };
 
 /* Local pointer to allocated TCM configfs fabric module */
@@ -99,6 +108,46 @@ static int iov_num_pages(struct iovec *iov)
 	       ((unsigned long)iov->iov_base & PAGE_MASK)) >> PAGE_SHIFT;
 }
 
+static int tcm_vhost_inc_inflight(struct vhost_scsi *vs)
+{
+	int during_flush;
+
+	spin_lock(&vs->vs_flush_lock);
+	during_flush = vs->vs_during_flush;
+	vs->vs_inflight[during_flush]++;
+	spin_unlock(&vs->vs_flush_lock);
+
+	return during_flush;
+}
+
+static void tcm_vhost_dec_inflight(struct vhost_scsi *vs, int during_flush)
+{
+	u64 inflight;
+
+	spin_lock(&vs->vs_flush_lock);
+	inflight = vs->vs_inflight[during_flush]--;
+	/*
+	 * Wakeup the waiter when all the requests issued before the flush
+	 * operation are finished and we are during the flush operation.
+	 */
+	if (!inflight && !during_flush && vs->vs_during_flush)
+		wake_up(&vs->vs_flush_wait);
+	spin_unlock(&vs->vs_flush_lock);
+}
+
+static bool tcm_vhost_done_inflight(struct vhost_scsi *vs)
+{
+	bool ret = false;
+
+	/* The requests issued before the flush operation are finished ? */
+	spin_lock(&vs->vs_flush_lock);
+	if (!vs->vs_inflight[0])
+		ret = true;
+	spin_unlock(&vs->vs_flush_lock);
+
+	return ret;
+}
+
 static bool tcm_vhost_check_feature(struct vhost_scsi *vs, int feature)
 {
 	bool ret = false;
@@ -391,6 +440,8 @@ static int tcm_vhost_queue_tm_rsp(struct se_cmd *se_cmd)
 
 static void tcm_vhost_free_evt(struct vhost_scsi *vs, struct tcm_vhost_evt
*evt)
 {
+
+	tcm_vhost_dec_inflight(vs, evt->during_flush);
 	mutex_lock(&vs->dev.mutex);
 	vs->vs_events_nr--;
 	kfree(evt);
@@ -412,6 +463,7 @@ static struct tcm_vhost_evt *tcm_vhost_allocate_evt(struct
vhost_scsi *vs,
 	if (evt) {
 		evt->event.event = event;
 		evt->event.reason = reason;
+		evt->during_flush = tcm_vhost_inc_inflight(vs);
 		vs->vs_events_nr++;
 	}
 	mutex_unlock(&vs->dev.mutex);
@@ -422,6 +474,7 @@ static struct tcm_vhost_evt *tcm_vhost_allocate_evt(struct
vhost_scsi *vs,
 static void vhost_scsi_free_cmd(struct tcm_vhost_cmd *tv_cmd)
 {
 	struct se_cmd *se_cmd = &tv_cmd->tvc_se_cmd;
+	struct vhost_scsi *vs = tv_cmd->tvc_vhost;
 
 	/* TODO locking against target/backend threads? */
 	transport_generic_free_cmd(se_cmd, 1);
@@ -434,13 +487,16 @@ static void vhost_scsi_free_cmd(struct tcm_vhost_cmd
*tv_cmd)
 		kfree(tv_cmd->tvc_sgl);
 	}
 
+	tcm_vhost_dec_inflight(vs, tv_cmd->during_flush);
+
 	kfree(tv_cmd);
 }
 
 static void tcm_vhost_do_evt_work(struct vhost_scsi *vs,
-	struct virtio_scsi_event *event)
+	struct tcm_vhost_evt *evt)
 {
 	struct vhost_virtqueue *vq = &vs->vqs[VHOST_SCSI_VQ_EVT];
+	struct virtio_scsi_event *event = &evt->event;
 	struct virtio_scsi_event __user *eventp;
 	unsigned out, in;
 	int head, ret;
@@ -503,7 +559,7 @@ static void tcm_vhost_evt_work(struct vhost_work *work)
 	while (llnode) {
 		evt = llist_entry(llnode, struct tcm_vhost_evt, list);
 		llnode = llist_next(llnode);
-		tcm_vhost_do_evt_work(vs, &evt->event);
+		tcm_vhost_do_evt_work(vs, evt);
 		tcm_vhost_free_evt(vs, evt);
 	}
 }
@@ -521,8 +577,8 @@ static void vhost_scsi_complete_cmd_work(struct vhost_work
*work)
 	struct virtio_scsi_cmd_resp v_rsp;
 	struct tcm_vhost_cmd *tv_cmd;
 	struct llist_node *llnode;
-	struct se_cmd *se_cmd;
 	int ret, vq;
+	struct se_cmd *se_cmd;
 
 	bitmap_zero(signal, VHOST_SCSI_MAX_VQ);
 	llnode = llist_del_all(&vs->vs_completion_list);
@@ -560,6 +616,7 @@ static void vhost_scsi_complete_cmd_work(struct vhost_work
*work)
 }
 
 static struct tcm_vhost_cmd *vhost_scsi_allocate_cmd(
+	struct vhost_scsi *vs,
 	struct tcm_vhost_tpg *tv_tpg,
 	struct virtio_scsi_cmd_req *v_req,
 	u32 exp_data_len,
@@ -584,6 +641,8 @@ static struct tcm_vhost_cmd *vhost_scsi_allocate_cmd(
 	tv_cmd->tvc_exp_data_len = exp_data_len;
 	tv_cmd->tvc_data_direction = data_direction;
 	tv_cmd->tvc_nexus = tv_nexus;
+	tv_cmd->tvc_vhost = vs;
+	tv_cmd->during_flush = tcm_vhost_inc_inflight(vs);
 
 	return tv_cmd;
 }
@@ -824,7 +883,7 @@ static void vhost_scsi_handle_vq(struct vhost_scsi *vs,
 		for (i = 0; i < data_num; i++)
 			exp_data_len += vq->iov[data_first + i].iov_len;
 
-		tv_cmd = vhost_scsi_allocate_cmd(tv_tpg, &v_req,
+		tv_cmd = vhost_scsi_allocate_cmd(vs, tv_tpg, &v_req,
 					exp_data_len, data_direction);
 		if (IS_ERR(tv_cmd)) {
 			vq_err(vq, "vhost_scsi_allocate_cmd failed %ld\n",
@@ -834,7 +893,6 @@ static void vhost_scsi_handle_vq(struct vhost_scsi *vs,
 		pr_debug("Allocated tv_cmd: %p exp_data_len: %d, data_direction"
 			": %d\n", tv_cmd, exp_data_len, data_direction);
 
-		tv_cmd->tvc_vhost = vs;
 		tv_cmd->tvc_vq = vq;
 
 		if (unlikely(vq->iov[out].iov_len !@@ -887,6 +945,7 @@ static void
vhost_scsi_handle_vq(struct vhost_scsi *vs,
 		 * tcm_vhost_queue_data_in() and tcm_vhost_queue_status()
 		 */
 		tv_cmd->tvc_vq_desc = head;
+
 		/*
 		 * Dispatch tv_cmd descriptor for cmwq execution in process
 		 * context provided by tcm_vhost_workqueue.  This also ensures
@@ -956,6 +1015,34 @@ static void vhost_scsi_handle_kick(struct vhost_work
*work)
 	vhost_scsi_handle_vq(vs, vq);
 }
 
+static void vhost_scsi_flush_vq(struct vhost_scsi *vs, int index)
+{
+	vhost_poll_flush(&vs->dev.vqs[index].poll);
+}
+
+static void vhost_scsi_flush(struct vhost_scsi *vs)
+{
+	int i;
+
+	/* Flush operation is started */
+	spin_lock(&vs->vs_flush_lock);
+	vs->vs_during_flush = 1;
+	spin_unlock(&vs->vs_flush_lock);
+
+	for (i = 0; i < VHOST_SCSI_MAX_VQ; i++)
+		vhost_scsi_flush_vq(vs, i);
+	vhost_work_flush(&vs->dev, &vs->vs_completion_work);
+	vhost_work_flush(&vs->dev, &vs->vs_event_work);
+
+	/* Wait until all requests issued before the flush to be finished */
+	wait_event(vs->vs_flush_wait, tcm_vhost_done_inflight(vs));
+
+	/* Flush operation is finished */
+	spin_lock(&vs->vs_flush_lock);
+	vs->vs_during_flush = 0;
+	spin_unlock(&vs->vs_flush_lock);
+}
+
 /*
  * Called from vhost_scsi_ioctl() context to walk the list of available
  * tcm_vhost_tpg with an active struct tcm_vhost_nexus
@@ -1042,6 +1129,7 @@ static int vhost_scsi_clear_endpoint(
 	u8 target;
 
 	mutex_lock(&vs->dev.mutex);
+
 	/* Verify that ring has been setup correctly. */
 	for (index = 0; index < vs->dev.nvqs; ++index) {
 		if (!vhost_vq_access_ok(&vs->vqs[index])) {
@@ -1109,6 +1197,10 @@ static int vhost_scsi_open(struct inode *inode, struct
file *f)
 	vhost_work_init(&s->vs_event_work, tcm_vhost_evt_work);
 
 	s->vs_events_nr = 0;
+	s->vs_inflight[0] = 0;
+	s->vs_inflight[1] = 0;
+	spin_lock_init(&s->vs_flush_lock);
+	init_waitqueue_head(&s->vs_flush_wait);
 
 	s->vqs[VHOST_SCSI_VQ_CTL].handle_kick = vhost_scsi_ctl_handle_kick;
 	s->vqs[VHOST_SCSI_VQ_EVT].handle_kick = vhost_scsi_evt_handle_kick;
@@ -1139,21 +1231,6 @@ static int vhost_scsi_release(struct inode *inode, struct
file *f)
 	return 0;
 }
 
-static void vhost_scsi_flush_vq(struct vhost_scsi *vs, int index)
-{
-	vhost_poll_flush(&vs->dev.vqs[index].poll);
-}
-
-static void vhost_scsi_flush(struct vhost_scsi *vs)
-{
-	int i;
-
-	for (i = 0; i < VHOST_SCSI_MAX_VQ; i++)
-		vhost_scsi_flush_vq(vs, i);
-	vhost_work_flush(&vs->dev, &vs->vs_completion_work);
-	vhost_work_flush(&vs->dev, &vs->vs_event_work);
-}
-
 static int vhost_scsi_set_features(struct vhost_scsi *vs, u64 features)
 {
 	if (features & ~VHOST_SCSI_FEATURES)
diff --git a/drivers/vhost/tcm_vhost.h b/drivers/vhost/tcm_vhost.h
index 94e9ee53..dd84622 100644
--- a/drivers/vhost/tcm_vhost.h
+++ b/drivers/vhost/tcm_vhost.h
@@ -37,6 +37,8 @@ struct tcm_vhost_cmd {
 	unsigned char tvc_sense_buf[TRANSPORT_SENSE_BUFFER];
 	/* Completed commands list, serviced from vhost worker thread */
 	struct llist_node tvc_completion_list;
+	/* Indicate this command is issued during the flush operaton */
+	int during_flush;
 };
 
 struct tcm_vhost_nexus {
@@ -91,6 +93,8 @@ struct tcm_vhost_evt {
 	struct virtio_scsi_event event;
 	/* virtio_scsi event list, serviced from vhost worker thread */
 	struct llist_node list;
+	/* Indicate this event is issued during the flush operaton */
+	int during_flush;
 };
 
 /*
-- 
1.8.1.4

Wait for termination of all pending requests in clear endpoint
operation, otherwise you cannot reset virtio devices safely.

Signed-off-by: Asias He <asias at redhat.com>
---
 drivers/vhost/tcm_vhost.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/vhost/tcm_vhost.c b/drivers/vhost/tcm_vhost.c
index dc0af52..f57e5ba 100644
--- a/drivers/vhost/tcm_vhost.c
+++ b/drivers/vhost/tcm_vhost.c
@@ -1174,6 +1174,9 @@ static int vhost_scsi_clear_endpoint(
 			mutex_unlock(&vq->mutex);
 		}
 	}
+	/* Flush the pending requests and wait for them to finish */
+	vhost_scsi_flush(vs);
+
 	mutex_unlock(&vs->dev.mutex);
 	return 0;
 
-- 
1.8.1.4

If we fail to submit the allocated tv_vmd to tcm_vhost_submission_work,
we will leak the tv_vmd. Free tv_vmd on fail path.

Signed-off-by: Asias He <asias at redhat.com>
---
 drivers/vhost/tcm_vhost.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/vhost/tcm_vhost.c b/drivers/vhost/tcm_vhost.c
index f57e5ba..16022d3 100644
--- a/drivers/vhost/tcm_vhost.c
+++ b/drivers/vhost/tcm_vhost.c
@@ -900,7 +900,7 @@ static void vhost_scsi_handle_vq(struct vhost_scsi *vs,
 			vq_err(vq, "Expecting virtio_scsi_cmd_resp, got %zu"
 				" bytes, out: %d, in: %d\n",
 				vq->iov[out].iov_len, out, in);
-			break;
+			goto err;
 		}
 
 		tv_cmd->tvc_resp = vq->iov[out].iov_base;
@@ -922,7 +922,7 @@ static void vhost_scsi_handle_vq(struct vhost_scsi *vs,
 				" exceeds SCSI_MAX_VARLEN_CDB_SIZE: %d\n",
 				scsi_command_size(tv_cmd->tvc_cdb),
 				TCM_VHOST_MAX_CDB_SIZE);
-			break; /* TODO */
+			goto err;
 		}
 		tv_cmd->tvc_lun = ((v_req.lun[2] << 8) | v_req.lun[3]) & 0x3FFF;
 
@@ -935,7 +935,7 @@ static void vhost_scsi_handle_vq(struct vhost_scsi *vs,
 					data_direction == DMA_TO_DEVICE);
 			if (unlikely(ret)) {
 				vq_err(vq, "Failed to map iov to sgl\n");
-				break; /* TODO */
+				goto err;
 			}
 		}
 
@@ -957,6 +957,11 @@ static void vhost_scsi_handle_vq(struct vhost_scsi *vs,
 	}
 
 	mutex_unlock(&vq->mutex);
+	return;
+
+err:
+	vhost_scsi_free_cmd(tv_cmd);
+	mutex_unlock(&vq->mutex);
 }
 
 static void vhost_scsi_ctl_handle_kick(struct vhost_work *work)
-- 
1.8.1.4

On Fri, 2013-03-22 at 14:55 +0800, Asias He wrote:
> Changes in v2:
> - Increase/Decrease inflight requests in
>   vhost_scsi_{allocate,free}_cmd and tcm_vhost_{allocate,free}_evt
> 
> Asias He (3):
>   tcm_vhost: Wait for pending requests in vhost_scsi_flush()
>   tcm_vhost: Wait for pending requests in vhost_scsi_clear_endpoint()
>   tcm_vhost: Fix tv_cmd leak in vhost_scsi_handle_vq
> 
>  drivers/vhost/tcm_vhost.c | 131
++++++++++++++++++++++++++++++++++++++--------
>  drivers/vhost/tcm_vhost.h |   4 ++
>  2 files changed, 112 insertions(+), 23 deletions(-)
> 
Ditto on this one as v3.10 material.  There is 2 weeks left before the
window opens, which should be enough time to settle on this..

MST, please review.

--nab