[PATCH v2 5/7] fuse: use locked req consistently in fuse_uring_next_fuse_req()

[Bernd Schubert <bschubert@xxxxxxx>]

This changes fuse_uring_next_fuse_req() and subfunctions
to use req obtained with a lock to avoid possible issues by
compiler induced re-ordering.

Also fix a function comment, that was missed during previous
code refactoring.

Fixes: a4bdb3d786c0 ("fuse: enable fuse-over-io-uring")
Signed-off-by: Bernd Schubert <bschubert@xxxxxxx>
---
 fs/fuse/dev_uring.c | 32 ++++++++++++--------------------
 1 file changed, 12 insertions(+), 20 deletions(-)

diff --git a/fs/fuse/dev_uring.c b/fs/fuse/dev_uring.c
index 80bb7396a8410022bbef1efa0522974bda77c81a..e90dd4ae5b2133e427855f1b0e60b73f008f7bc9 100644
--- a/fs/fuse/dev_uring.c
+++ b/fs/fuse/dev_uring.c
@@ -75,16 +75,15 @@ static void fuse_uring_flush_bg(struct fuse_ring_queue *queue)
 	}
 }
 
-static void fuse_uring_req_end(struct fuse_ring_ent *ent, int error)
+static void fuse_uring_req_end(struct fuse_ring_ent *ent, struct fuse_req *req,
+			       int error)
 {
 	struct fuse_ring_queue *queue = ent->queue;
-	struct fuse_req *req;
 	struct fuse_ring *ring = queue->ring;
 	struct fuse_conn *fc = ring->fc;
 
 	lockdep_assert_not_held(&queue->lock);
 	spin_lock(&queue->lock);
-	req = ent->fuse_req;
 	ent->fuse_req = NULL;
 	if (test_bit(FR_BACKGROUND, &req->flags)) {
 		queue->active_background--;
@@ -684,7 +683,7 @@ static int fuse_uring_prepare_send(struct fuse_ring_ent *ent,
 	if (!err)
 		set_bit(FR_SENT, &req->flags);
 	else
-		fuse_uring_req_end(ent, err);
+		fuse_uring_req_end(ent, req, err);
 
 	return err;
 }
@@ -768,12 +767,8 @@ static void fuse_uring_add_req_to_ring_ent(struct fuse_ring_ent *ent,
 	fuse_uring_add_to_pq(ent, req);
 }
 
-/*
- * Release the ring entry and fetch the next fuse request if available
- *
- * @return true if a new request has been fetched
- */
-static bool fuse_uring_ent_assign_req(struct fuse_ring_ent *ent)
+/* Fetch the next fuse request if available */
+static struct fuse_req *fuse_uring_ent_assign_req(struct fuse_ring_ent *ent)
 	__must_hold(&queue->lock)
 {
 	struct fuse_req *req;
@@ -784,12 +779,10 @@ static bool fuse_uring_ent_assign_req(struct fuse_ring_ent *ent)
 
 	/* get and assign the next entry while it is still holding the lock */
 	req = list_first_entry_or_null(req_queue, struct fuse_req, list);
-	if (req) {
+	if (req)
 		fuse_uring_add_req_to_ring_ent(ent, req);
-		return true;
-	}
 
-	return false;
+	return req;
 }
 
 /*
@@ -819,7 +812,7 @@ static void fuse_uring_commit(struct fuse_ring_ent *ent, struct fuse_req *req,
 
 	err = fuse_uring_copy_from_ring(ring, req, ent);
 out:
-	fuse_uring_req_end(ent, err);
+	fuse_uring_req_end(ent, req, err);
 }
 
 /*
@@ -830,17 +823,16 @@ static void fuse_uring_next_fuse_req(struct fuse_ring_ent *ent,
 				     unsigned int issue_flags)
 {
 	int err;
-	bool has_next;
+	struct fuse_req *req;
 
 retry:
 	spin_lock(&queue->lock);
 	fuse_uring_ent_avail(ent, queue);
-	has_next = fuse_uring_ent_assign_req(ent);
+	req = fuse_uring_ent_assign_req(ent);
 	spin_unlock(&queue->lock);
 
-	if (has_next) {
-		err = fuse_uring_send_next_to_ring(ent, ent->fuse_req,
-						   issue_flags);
+	if (req) {
+		err = fuse_uring_send_next_to_ring(ent, req, issue_flags);
 		if (err)
 			goto retry;
 	}

-- 
2.43.0