Merge: nbd: fix partial sending

MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-10/-/merge_requests/204

JIRA: https://issues.redhat.com/browse/RHEL-74229

Upstream Status: for-6.14/block

Signed-off-by: Ming Lei <ming.lei@redhat.com>

Approved-by: Ewan D. Milne <emilne@redhat.com>
Approved-by: Chris Leech <cleech@redhat.com>
Approved-by: CKI KWF Bot <cki-ci-bot+kwf-gitlab-com@redhat.com>

Merged-by: Jan Stancek <jstancek@redhat.com>

Author: jstancek

drivers/block/nbd.c

@@ -62,6 +62,7 @@ struct nbd_sock {
 	bool dead;
 	int fallback_index;
 	int cookie;
+	struct work_struct work;
 };
 
 struct recv_thread_args {
@@ -141,6 +142,9 @@ struct nbd_device {
  */
 #define NBD_CMD_INFLIGHT	2
 
+/* Just part of request header or data payload is sent successfully */
+#define NBD_CMD_PARTIAL_SEND	3
+
 struct nbd_cmd {
 	struct nbd_device *nbd;
 	struct mutex lock;
@@ -466,6 +470,12 @@ static enum blk_eh_timer_return nbd_xmit_timeout(struct request *req)
 	if (!mutex_trylock(&cmd->lock))
 		return BLK_EH_RESET_TIMER;
 
+	/* partial send is handled in nbd_sock's work function */
+	if (test_bit(NBD_CMD_PARTIAL_SEND, &cmd->flags)) {
+		mutex_unlock(&cmd->lock);
+		return BLK_EH_RESET_TIMER;
+	}
+
 	if (!test_bit(NBD_CMD_INFLIGHT, &cmd->flags)) {
 		mutex_unlock(&cmd->lock);
 		return BLK_EH_DONE;
@@ -614,6 +624,30 @@ static inline int was_interrupted(int result)
 	return result == -ERESTARTSYS || result == -EINTR;
 }
 
+/*
+ * We've already sent header or part of data payload, have no choice but
+ * to set pending and schedule it in work.
+ *
+ * And we have to return BLK_STS_OK to block core, otherwise this same
+ * request may be re-dispatched with different tag, but our header has
+ * been sent out with old tag, and this way does confuse reply handling.
+ */
+static void nbd_sched_pending_work(struct nbd_device *nbd,
+				   struct nbd_sock *nsock,
+				   struct nbd_cmd *cmd, int sent)
+{
+	struct request *req = blk_mq_rq_from_pdu(cmd);
+
+	/* pending work should be scheduled only once */
+	WARN_ON_ONCE(test_bit(NBD_CMD_PARTIAL_SEND, &cmd->flags));
+
+	nsock->pending = req;
+	nsock->sent = sent;
+	set_bit(NBD_CMD_PARTIAL_SEND, &cmd->flags);
+	refcount_inc(&nbd->config_refs);
+	schedule_work(&nsock->work);
+}
+
 /*
  * Returns BLK_STS_RESOURCE if the caller should retry after a delay.
  * Returns BLK_STS_IOERR if sending failed.
@@ -699,8 +733,8 @@ static blk_status_t nbd_send_cmd(struct nbd_device *nbd, struct nbd_cmd *cmd,
 			 * completely done.
 			 */
 			if (sent) {
-				nsock->pending = req;
-				nsock->sent = sent;
+				nbd_sched_pending_work(nbd, nsock, cmd, sent);
+				return BLK_STS_OK;
 			}
 			set_bit(NBD_CMD_REQUEUED, &cmd->flags);
 			return BLK_STS_RESOURCE;
@@ -737,14 +771,8 @@ static blk_status_t nbd_send_cmd(struct nbd_device *nbd, struct nbd_cmd *cmd,
 			result = sock_xmit(nbd, index, 1, &from, flags, &sent);
 			if (result < 0) {
 				if (was_interrupted(result)) {
-					/* We've already sent the header, we
-					 * have no choice but to set pending and
-					 * return BUSY.
-					 */
-					nsock->pending = req;
-					nsock->sent = sent;
-					set_bit(NBD_CMD_REQUEUED, &cmd->flags);
-					return BLK_STS_RESOURCE;
+					nbd_sched_pending_work(nbd, nsock, cmd, sent);
+					return BLK_STS_OK;
 				}
 				dev_err(disk_to_dev(nbd->disk),
 					"Send data failed (result %d)\n",
@@ -770,6 +798,14 @@ static blk_status_t nbd_send_cmd(struct nbd_device *nbd, struct nbd_cmd *cmd,
 	return BLK_STS_OK;
 
 requeue:
+	/*
+	 * Can't requeue in case we are dealing with partial send
+	 *
+	 * We must run from pending work function.
+	 * */
+	if (test_bit(NBD_CMD_PARTIAL_SEND, &cmd->flags))
+		return BLK_STS_OK;
+
 	/* retry on a different socket */
 	dev_err_ratelimited(disk_to_dev(nbd->disk),
 			    "Request send failed, requeueing\n");
@@ -778,6 +814,44 @@ static blk_status_t nbd_send_cmd(struct nbd_device *nbd, struct nbd_cmd *cmd,
 	return BLK_STS_OK;
 }
 
+/* handle partial sending */
+static void nbd_pending_cmd_work(struct work_struct *work)
+{
+	struct nbd_sock *nsock = container_of(work, struct nbd_sock, work);
+	struct request *req = nsock->pending;
+	struct nbd_cmd *cmd = blk_mq_rq_to_pdu(req);
+	struct nbd_device *nbd = cmd->nbd;
+	unsigned long deadline = READ_ONCE(req->deadline);
+	unsigned int wait_ms = 2;
+
+	mutex_lock(&cmd->lock);
+
+	WARN_ON_ONCE(test_bit(NBD_CMD_REQUEUED, &cmd->flags));
+	if (WARN_ON_ONCE(!test_bit(NBD_CMD_PARTIAL_SEND, &cmd->flags)))
+		goto out;
+
+	mutex_lock(&nsock->tx_lock);
+	while (true) {
+		nbd_send_cmd(nbd, cmd, cmd->index);
+		if (!nsock->pending)
+			break;
+
+		/* don't bother timeout handler for partial sending */
+		if (READ_ONCE(jiffies) + msecs_to_jiffies(wait_ms) >= deadline) {
+			cmd->status = BLK_STS_IOERR;
+			blk_mq_complete_request(req);
+			break;
+		}
+		msleep(wait_ms);
+		wait_ms *= 2;
+	}
+	mutex_unlock(&nsock->tx_lock);
+	clear_bit(NBD_CMD_PARTIAL_SEND, &cmd->flags);
+out:
+	mutex_unlock(&cmd->lock);
+	nbd_config_put(nbd);
+}
+
 static int nbd_read_reply(struct nbd_device *nbd, struct socket *sock,
 			  struct nbd_reply *reply)
 {
@@ -1224,6 +1298,7 @@ static int nbd_add_socket(struct nbd_device *nbd, unsigned long arg,
 	nsock->pending = NULL;
 	nsock->sent = 0;
 	nsock->cookie = 0;
+	INIT_WORK(&nsock->work, nbd_pending_cmd_work);
 	socks[config->num_connections++] = nsock;
 	atomic_inc(&config->live_connections);
 	blk_mq_unfreeze_queue(nbd->disk->queue);