6.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Joanne Koong <joannelkoong@gmail.com>

[ Upstream commit 8bbb2ad1f687633a991839bd3efae04ccfb29e19 ]

Replace magic indices 0 and 1 for the iovec array with named constants
FUSE_URING_IOV_HEADERS and FUSE_URING_IOV_PAYLOAD. This makes the usages
self-documenting and prepares for buffer ring support which will also
reference these iovec slots by index.

Reviewed-by: Bernd Schubert <bernd@bsbernd.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Baokun Li <libaokun@linux.alibaba.com>
Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Stable-dep-of: fd10f40af314 ("fuse: copy request headers via a stack buffer for io-uring")
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/fuse/dev_uring.c |   24 +++++++++++++-----------
 1 file changed, 13 insertions(+), 11 deletions(-)

--- a/fs/fuse/dev_uring.c
+++ b/fs/fuse/dev_uring.c
@@ -18,7 +18,8 @@ MODULE_PARM_DESC(enable_uring,
 		 "Enable userspace communication through io-uring");
 
 #define FUSE_URING_IOV_SEGS 2 /* header and payload */
-
+#define FUSE_URING_IOV_HEADERS 0
+#define FUSE_URING_IOV_PAYLOAD 1
 
 bool fuse_uring_enabled(void)
 {
@@ -1105,8 +1106,8 @@ static int fuse_uring_do_register(struct
 }
 
 /*
- * sqe->addr is a ptr to an iovec array, iov[0] has the headers, iov[1]
- * the payload
+ * sqe->addr is a ptr to an iovec array, iov[FUSE_URING_IOV_HEADERS] has the
+ * headers, iov[FUSE_URING_IOV_PAYLOAD] the payload
  */
 static int fuse_uring_get_iovec_from_sqe(const struct io_uring_sqe *sqe,
 					 struct iovec iov[FUSE_URING_IOV_SEGS])
@@ -1136,8 +1137,8 @@ fuse_uring_create_ring_ent(struct io_uri
 {
 	struct fuse_ring *ring = queue->ring;
 	struct fuse_ring_ent *ent;
-	size_t payload_size;
 	struct iovec iov[FUSE_URING_IOV_SEGS];
+	struct iovec *headers, *payload;
 	int err;
 
 	err = fuse_uring_get_iovec_from_sqe(cmd->sqe, iov);
@@ -1148,15 +1149,16 @@ fuse_uring_create_ring_ent(struct io_uri
 	}
 
 	err = -EINVAL;
-	if (iov[0].iov_len < sizeof(struct fuse_uring_req_header)) {
-		pr_info_ratelimited("Invalid header len %zu\n", iov[0].iov_len);
+	headers = &iov[FUSE_URING_IOV_HEADERS];
+	if (headers->iov_len < sizeof(struct fuse_uring_req_header)) {
+		pr_info_ratelimited("Invalid header len %zu\n", headers->iov_len);
 		return ERR_PTR(err);
 	}
 
-	payload_size = iov[1].iov_len;
-	if (payload_size < ring->max_payload_sz) {
+	payload = &iov[FUSE_URING_IOV_PAYLOAD];
+	if (payload->iov_len < ring->max_payload_sz) {
 		pr_info_ratelimited("Invalid req payload len %zu\n",
-				    payload_size);
+				    payload->iov_len);
 		return ERR_PTR(err);
 	}
 
@@ -1168,8 +1170,8 @@ fuse_uring_create_ring_ent(struct io_uri
 	INIT_LIST_HEAD(&ent->list);
 
 	ent->queue = queue;
-	ent->headers = iov[0].iov_base;
-	ent->payload = iov[1].iov_base;
+	ent->headers = headers->iov_base;
+	ent->payload = payload->iov_base;
 
 	atomic_inc(&ring->queue_refs);
 	return ent;