[PATCH v2 01/14] fuse: separate next request fetching from sending logic

[Joanne Koong <joannelkoong@gmail.com>]

Simplify the logic for fetching + sending off the next request.

This gets rid of fuse_uring_send_next_to_ring() which contained
duplicated logic from fuse_uring_send(). This decouples request fetching
from the send operation, which makes the control flow clearer and
reduces unnecessary parameter passing.

Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Reviewed-by: Bernd Schubert <bschubert@ddn.com>
---
 fs/fuse/dev_uring.c | 78 ++++++++++++++++-----------------------------
 1 file changed, 28 insertions(+), 50 deletions(-)

diff --git a/fs/fuse/dev_uring.c b/fs/fuse/dev_uring.c
index 3a38b61aac26..54436d3fda4d 100644
--- a/fs/fuse/dev_uring.c
+++ b/fs/fuse/dev_uring.c
@@ -714,34 +714,6 @@ static int fuse_uring_prepare_send(struct fuse_ring_ent *ent,
 	return err;
 }
 
-/*
- * Write data to the ring buffer and send the request to userspace,
- * userspace will read it
- * This is comparable with classical read(/dev/fuse)
- */
-static int fuse_uring_send_next_to_ring(struct fuse_ring_ent *ent,
-					struct fuse_req *req,
-					unsigned int issue_flags)
-{
-	struct fuse_ring_queue *queue = ent->queue;
-	int err;
-	struct io_uring_cmd *cmd;
-
-	err = fuse_uring_prepare_send(ent, req);
-	if (err)
-		return err;
-
-	spin_lock(&queue->lock);
-	cmd = ent->cmd;
-	ent->cmd = NULL;
-	ent->state = FRRS_USERSPACE;
-	list_move_tail(&ent->list, &queue->ent_in_userspace);
-	spin_unlock(&queue->lock);
-
-	io_uring_cmd_done(cmd, 0, issue_flags);
-	return 0;
-}
-
 /*
  * Make a ring entry available for fuse_req assignment
  */
@@ -838,11 +810,13 @@ static void fuse_uring_commit(struct fuse_ring_ent *ent, struct fuse_req *req,
 }
 
 /*
- * Get the next fuse req and send it
+ * Get the next fuse req.
+ *
+ * Returns true if the next fuse request has been assigned to the ent.
+ * Else, there is no next fuse request and this returns false.
  */
-static void fuse_uring_next_fuse_req(struct fuse_ring_ent *ent,
-				     struct fuse_ring_queue *queue,
-				     unsigned int issue_flags)
+static bool fuse_uring_get_next_fuse_req(struct fuse_ring_ent *ent,
+					 struct fuse_ring_queue *queue)
 {
 	int err;
 	struct fuse_req *req;
@@ -854,10 +828,12 @@ static void fuse_uring_next_fuse_req(struct fuse_ring_ent *ent,
 	spin_unlock(&queue->lock);
 
 	if (req) {
-		err = fuse_uring_send_next_to_ring(ent, req, issue_flags);
+		err = fuse_uring_prepare_send(ent, req);
 		if (err)
 			goto retry;
 	}
+
+	return req != NULL;
 }
 
 static int fuse_ring_ent_set_commit(struct fuse_ring_ent *ent)
@@ -875,6 +851,20 @@ static int fuse_ring_ent_set_commit(struct fuse_ring_ent *ent)
 	return 0;
 }
 
+static void fuse_uring_send(struct fuse_ring_ent *ent, struct io_uring_cmd *cmd,
+			    ssize_t ret, unsigned int issue_flags)
+{
+	struct fuse_ring_queue *queue = ent->queue;
+
+	spin_lock(&queue->lock);
+	ent->state = FRRS_USERSPACE;
+	list_move_tail(&ent->list, &queue->ent_in_userspace);
+	ent->cmd = NULL;
+	spin_unlock(&queue->lock);
+
+	io_uring_cmd_done(cmd, ret, issue_flags);
+}
+
 /* FUSE_URING_CMD_COMMIT_AND_FETCH handler */
 static int fuse_uring_commit_fetch(struct io_uring_cmd *cmd, int issue_flags,
 				   struct fuse_conn *fc)
@@ -947,7 +937,8 @@ static int fuse_uring_commit_fetch(struct io_uring_cmd *cmd, int issue_flags,
 	 * and fetching is done in one step vs legacy fuse, which has separated
 	 * read (fetch request) and write (commit result).
 	 */
-	fuse_uring_next_fuse_req(ent, queue, issue_flags);
+	if (fuse_uring_get_next_fuse_req(ent, queue))
+		fuse_uring_send(ent, cmd, 0, issue_flags);
 	return 0;
 }
 
@@ -1196,20 +1187,6 @@ int fuse_uring_cmd(struct io_uring_cmd *cmd, unsigned int issue_flags)
 	return -EIOCBQUEUED;
 }
 
-static void fuse_uring_send(struct fuse_ring_ent *ent, struct io_uring_cmd *cmd,
-			    ssize_t ret, unsigned int issue_flags)
-{
-	struct fuse_ring_queue *queue = ent->queue;
-
-	spin_lock(&queue->lock);
-	ent->state = FRRS_USERSPACE;
-	list_move_tail(&ent->list, &queue->ent_in_userspace);
-	ent->cmd = NULL;
-	spin_unlock(&queue->lock);
-
-	io_uring_cmd_done(cmd, ret, issue_flags);
-}
-
 /*
  * This prepares and sends the ring request in fuse-uring task context.
  * User buffers are not mapped yet - the application does not have permission
@@ -1226,8 +1203,9 @@ static void fuse_uring_send_in_task(struct io_tw_req tw_req, io_tw_token_t tw)
 	if (!tw.cancel) {
 		err = fuse_uring_prepare_send(ent, ent->fuse_req);
 		if (err) {
-			fuse_uring_next_fuse_req(ent, queue, issue_flags);
-			return;
+			if (!fuse_uring_get_next_fuse_req(ent, queue))
+				return;
+			err = 0;
 		}
 	} else {
 		err = -ECANCELED;
-- 
2.52.0