libublksrv: ABI change: allow target/backend to request extra io slot…

… allocation target/backend may need extra io slot for handling specific io, such as meta background io. And this slots will be managed by target/backend code, and libublksrv won't touch them at all. This change breaks ABI of libublksrv, so please update libublksrv. It is planned to stabilize libublksrv ABI in v1.0 release, and hope it can be done soon. Signed-off-by: Ming Lei <[email protected]>
ublk-org · Sep 11, 2022 · 29de3e4 · 29de3e4
1 parent cca1033
commit 29de3e4
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Showing 5 changed files with 23 additions and 7 deletions.
diff --git a/demo_event.c b/demo_event.c
@@ -314,7 +314,7 @@ static void *demo_event_io_handler_fn(void *data)
 			q_id, gettid());
 	pthread_mutex_unlock(&jbuf_lock);
 
-	q = ublksrv_queue_init(dev, q_id, info);
+	q = ublksrv_queue_init(dev, q_id, 0, info);
 	if (!q) {
 		fprintf(stderr, "ublk dev %d queue %d init queue failed\n",
 				dev->ctrl_dev->dev_info.dev_id, q_id);

diff --git a/demo_null.c b/demo_null.c
@@ -47,7 +47,7 @@ static void *demo_null_io_handler_fn(void *data)
 	ublksrv_json_write_queue_info(dev->ctrl_dev, jbuf, sizeof jbuf,
 			q_id, gettid());
 	pthread_mutex_unlock(&jbuf_lock);
-	q = ublksrv_queue_init(dev, q_id, NULL);
+	q = ublksrv_queue_init(dev, q_id, 0, NULL);
 	if (!q) {
 		fprintf(stderr, "ublk dev %d queue %d init queue failed\n",
 				dev->ctrl_dev->dev_info.dev_id, q_id);

diff --git a/include/ublksrv.h b/include/ublksrv.h
@@ -205,6 +205,8 @@ struct ublksrv_tgt_type {
 	int  type;
 	unsigned ublk_flags;	//flags required for ublk driver
 	unsigned ublksrv_flags;	//flags required for ublksrv
+	int extra_ios;		//extra io slots allocated for handling
+				//target specific IOs, such as meta io
 	const char *name;
 
 	/*
@@ -372,7 +374,8 @@ static inline void *ublksrv_queue_get_data(const struct ublksrv_queue *q)
 }
 
 extern struct ublksrv_queue *ublksrv_queue_init(struct ublksrv_dev *dev,
-		unsigned short q_id, void *queue_data);
+		unsigned short q_id, unsigned short nr_extra_ios,
+		void *queue_data);
 extern void ublksrv_queue_deinit(struct ublksrv_queue *q);
 extern int ublksrv_queue_handled_event(struct ublksrv_queue *q);
 extern int ublksrv_queue_send_event(struct ublksrv_queue *q);

diff --git a/lib/ublksrv.c b/lib/ublksrv.c
@@ -508,8 +508,17 @@ static int ublksrv_setup_eventfd(struct ublksrv_queue *q)
 	return 0;
 }
 
+/*
+ * target/backend may need some extra io slots for handling something
+ * like meta data flushing in background, so allow target to pass
+ * this info via 'nr_extra_ios' which can't be > queue_depth.
+ *
+ * And it is target code's responsibility for managing these extra
+ * slots, and libublksrv won't touch these slots at all.
+ */
 struct ublksrv_queue *ublksrv_queue_init(struct ublksrv_dev *dev,
-		unsigned short q_id, void *queue_data)
+		unsigned short q_id, unsigned short nr_extra_ios,
+		void *queue_data)
 {
 	struct ublksrv_queue *q;
 	const struct ublksrv_ctrl_dev *ctrl_dev = dev->ctrl_dev;
@@ -518,9 +527,13 @@ struct ublksrv_queue *ublksrv_queue_init(struct ublksrv_dev *dev,
 	int cmd_buf_size, io_buf_size;
 	unsigned long off;
 	int ring_depth = depth + dev->tgt.tgt_ring_depth;
+	int nr_ios = depth + nr_extra_ios;
+
+	if (nr_extra_ios > depth)
+		return NULL;
 
-	q = (struct ublksrv_queue *)malloc(sizeof(struct ublksrv_queue) + sizeof(struct ublk_io) *
-		ctrl_dev->dev_info.queue_depth);
+	q = (struct ublksrv_queue *)malloc(sizeof(struct ublksrv_queue) +
+			sizeof(struct ublk_io) * nr_ios);
 	dev->__queues[q_id] = q;
 
 	q->dev = dev;

diff --git a/ublksrv_tgt.cpp b/ublksrv_tgt.cpp
@@ -197,7 +197,7 @@ static void *ublksrv_io_handler_fn(void *data)
 		ublksrv_tgt_store_dev_data(dev, buf);
 	pthread_mutex_unlock(&jbuf_lock);
 
-	q = ublksrv_queue_init(dev, q_id, NULL);
+	q = ublksrv_queue_init(dev, q_id, dev->tgt.ops->extra_ios, NULL);
 	if (!q) {
 		syslog(LOG_INFO, "ublk dev %d queue %d init queue failed",
 				dev->ctrl_dev->dev_info.dev_id, q_id);