[PATCH v2 16/25] fuse: use enum types for header copying

[Joanne Koong <joannelkoong@gmail.com>]

Use enum types to identify which part of the header needs to be copied.
This improves the interface and will simplify both kernel-space and
user-space header addresses when kernel-managed buffer rings are added.

Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Reviewed-by: Bernd Schubert <bschubert@ddn.com>
---
 fs/fuse/dev_uring.c | 57 +++++++++++++++++++++++++++++++++++++--------
 1 file changed, 47 insertions(+), 10 deletions(-)

diff --git a/fs/fuse/dev_uring.c b/fs/fuse/dev_uring.c
index e8ee51bfa5fc..d16f6b3489c1 100644
--- a/fs/fuse/dev_uring.c
+++ b/fs/fuse/dev_uring.c
@@ -31,6 +31,15 @@ struct fuse_uring_pdu {
 
 static const struct fuse_iqueue_ops fuse_io_uring_ops;
 
+enum fuse_uring_header_type {
+	/* struct fuse_in_header / struct fuse_out_header */
+	FUSE_URING_HEADER_IN_OUT,
+	/* per op code header */
+	FUSE_URING_HEADER_OP,
+	/* struct fuse_uring_ent_in_out header */
+	FUSE_URING_HEADER_RING_ENT,
+};
+
 static void uring_cmd_set_ring_ent(struct io_uring_cmd *cmd,
 				   struct fuse_ring_ent *ring_ent)
 {
@@ -575,10 +584,32 @@ static int fuse_uring_out_header_has_err(struct fuse_out_header *oh,
 	return err;
 }
 
-static __always_inline int copy_header_to_ring(void __user *ring,
+static void __user *get_user_ring_header(struct fuse_ring_ent *ent,
+					 enum fuse_uring_header_type type)
+{
+	switch (type) {
+	case FUSE_URING_HEADER_IN_OUT:
+		return &ent->headers->in_out;
+	case FUSE_URING_HEADER_OP:
+		return &ent->headers->op_in;
+	case FUSE_URING_HEADER_RING_ENT:
+		return &ent->headers->ring_ent_in_out;
+	}
+
+	WARN_ON_ONCE(1);
+	return NULL;
+}
+
+static __always_inline int copy_header_to_ring(struct fuse_ring_ent *ent,
+					       enum fuse_uring_header_type type,
 					       const void *header,
 					       size_t header_size)
 {
+	void __user *ring = get_user_ring_header(ent, type);
+
+	if (!ring)
+		return -EINVAL;
+
 	if (copy_to_user(ring, header, header_size)) {
 		pr_info_ratelimited("Copying header to ring failed.\n");
 		return -EFAULT;
@@ -587,10 +618,16 @@ static __always_inline int copy_header_to_ring(void __user *ring,
 	return 0;
 }
 
-static __always_inline int copy_header_from_ring(void *header,
-						 const void __user *ring,
+static __always_inline int copy_header_from_ring(struct fuse_ring_ent *ent,
+						 enum fuse_uring_header_type type,
+						 void *header,
 						 size_t header_size)
 {
+	const void __user *ring = get_user_ring_header(ent, type);
+
+	if (!ring)
+		return -EINVAL;
+
 	if (copy_from_user(header, ring, header_size)) {
 		pr_info_ratelimited("Copying header from ring failed.\n");
 		return -EFAULT;
@@ -609,8 +646,8 @@ static int fuse_uring_copy_from_ring(struct fuse_ring *ring,
 	int err;
 	struct fuse_uring_ent_in_out ring_in_out;
 
-	err = copy_header_from_ring(&ring_in_out, &ent->headers->ring_ent_in_out,
-				    sizeof(ring_in_out));
+	err = copy_header_from_ring(ent, FUSE_URING_HEADER_RING_ENT,
+				    &ring_in_out, sizeof(ring_in_out));
 	if (err)
 		return err;
 
@@ -661,7 +698,7 @@ static int fuse_uring_args_to_ring(struct fuse_ring *ring, struct fuse_req *req,
 		 * Some op code have that as zero size.
 		 */
 		if (args->in_args[0].size > 0) {
-			err = copy_header_to_ring(&ent->headers->op_in,
+			err = copy_header_to_ring(ent, FUSE_URING_HEADER_OP,
 						  in_args->value,
 						  in_args->size);
 			if (err)
@@ -681,8 +718,8 @@ static int fuse_uring_args_to_ring(struct fuse_ring *ring, struct fuse_req *req,
 	}
 
 	ent_in_out.payload_sz = cs.ring.copied_sz;
-	return copy_header_to_ring(&ent->headers->ring_ent_in_out, &ent_in_out,
-				   sizeof(ent_in_out));
+	return copy_header_to_ring(ent, FUSE_URING_HEADER_RING_ENT,
+				   &ent_in_out, sizeof(ent_in_out));
 }
 
 static int fuse_uring_copy_to_ring(struct fuse_ring_ent *ent,
@@ -711,7 +748,7 @@ static int fuse_uring_copy_to_ring(struct fuse_ring_ent *ent,
 	}
 
 	/* copy fuse_in_header */
-	return copy_header_to_ring(&ent->headers->in_out, &req->in.h,
+	return copy_header_to_ring(ent, FUSE_URING_HEADER_IN_OUT, &req->in.h,
 				   sizeof(req->in.h));
 }
 
@@ -806,7 +843,7 @@ static void fuse_uring_commit(struct fuse_ring_ent *ent, struct fuse_req *req,
 	struct fuse_conn *fc = ring->fc;
 	ssize_t err = 0;
 
-	err = copy_header_from_ring(&req->out.h, &ent->headers->in_out,
+	err = copy_header_from_ring(ent, FUSE_URING_HEADER_IN_OUT, &req->out.h,
 				    sizeof(req->out.h));
 	if (err) {
 		req->out.h.error = err;
-- 
2.47.3