io_uring: unify getting ctx from passed in file descriptor

io_uring_enter() and io_uring_register() end up having duplicated code
for getting a ctx from a passed in file descriptor, for either a
registered ring descriptor or a normal file descriptor. Move the
io_uring_register_get_file() into io_uring.c and name it a bit more
generically, and use it from both callsites rather than have that logic
and handling duplicated.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: axboe

io_uring/bpf-ops.c

@@ -181,7 +181,7 @@ static int bpf_io_reg(void *kdata, struct bpf_link *link)
 	struct file *file;
 	int ret = -EBUSY;
 
-	file = io_uring_register_get_file(ops->ring_fd, false);
+	file = io_uring_ctx_get_file(ops->ring_fd, false);
 	if (IS_ERR(file))
 		return PTR_ERR(file);
 	ctx = file->private_data;

io_uring/io_uring.c

@@ -2543,39 +2543,54 @@ static int io_get_ext_arg(struct io_ring_ctx *ctx, unsigned flags,
 #endif
 }
 
-SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
-		u32, min_complete, u32, flags, const void __user *, argp,
-		size_t, argsz)
+/*
+ * Given an 'fd' value, return the ctx associated with if. If 'registered' is
+ * true, then the registered index is used. Otherwise, the normal fd table.
+ * Caller must call fput() on the returned file if it isn't a registered file,
+ * unless it's an ERR_PTR.
+ */
+struct file *io_uring_ctx_get_file(unsigned int fd, bool registered)
 {
-	struct io_ring_ctx *ctx;
 	struct file *file;
-	long ret;
-
-	if (unlikely(flags & ~IORING_ENTER_FLAGS))
-		return -EINVAL;
 
-	/*
-	 * Ring fd has been registered via IORING_REGISTER_RING_FDS, we
-	 * need only dereference our task private array to find it.
-	 */
-	if (flags & IORING_ENTER_REGISTERED_RING) {
+	if (registered) {
+		/*
+		 * Ring fd has been registered via IORING_REGISTER_RING_FDS, we
+		 * need only dereference our task private array to find it.
+		 */
 		struct io_uring_task *tctx = current->io_uring;
 
 		if (unlikely(!tctx || fd >= IO_RINGFD_REG_MAX))
-			return -EINVAL;
+			return ERR_PTR(-EINVAL);
 		fd = array_index_nospec(fd, IO_RINGFD_REG_MAX);
 		file = tctx->registered_rings[fd];
-		if (unlikely(!file))
-			return -EBADF;
 	} else {
 		file = fget(fd);
-		if (unlikely(!file))
-			return -EBADF;
-		ret = -EOPNOTSUPP;
-		if (unlikely(!io_is_uring_fops(file)))
-			goto out;
 	}
 
+	if (unlikely(!file))
+		return ERR_PTR(-EBADF);
+	if (io_is_uring_fops(file))
+		return file;
+	fput(file);
+	return ERR_PTR(-EOPNOTSUPP);
+}
+
+
+SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
+		u32, min_complete, u32, flags, const void __user *, argp,
+		size_t, argsz)
+{
+	struct io_ring_ctx *ctx;
+	struct file *file;
+	long ret;
+
+	if (unlikely(flags & ~IORING_ENTER_FLAGS))
+		return -EINVAL;
+
+	file = io_uring_ctx_get_file(fd, flags & IORING_ENTER_REGISTERED_RING);
+	if (IS_ERR(file))
+		return PTR_ERR(file);
 	ctx = file->private_data;
 	ret = -EBADFD;
 	/*

io_uring/io_uring.h

@@ -173,6 +173,7 @@ void io_req_track_inflight(struct io_kiocb *req);
 struct file *io_file_get_normal(struct io_kiocb *req, int fd);
 struct file *io_file_get_fixed(struct io_kiocb *req, int fd,
 			       unsigned issue_flags);
+struct file *io_uring_ctx_get_file(unsigned int fd, bool registered);
 
 void io_req_task_queue(struct io_kiocb *req);
 void io_req_task_complete(struct io_tw_req tw_req, io_tw_token_t tw);

io_uring/register.c

@@ -938,39 +938,6 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
 	return ret;
 }
 
-/*
- * Given an 'fd' value, return the ctx associated with if. If 'registered' is
- * true, then the registered index is used. Otherwise, the normal fd table.
- * Caller must call fput() on the returned file if it isn't a registered file,
- * unless it's an ERR_PTR.
- */
-struct file *io_uring_register_get_file(unsigned int fd, bool registered)
-{
-	struct file *file;
-
-	if (registered) {
-		/*
-		 * Ring fd has been registered via IORING_REGISTER_RING_FDS, we
-		 * need only dereference our task private array to find it.
-		 */
-		struct io_uring_task *tctx = current->io_uring;
-
-		if (unlikely(!tctx || fd >= IO_RINGFD_REG_MAX))
-			return ERR_PTR(-EINVAL);
-		fd = array_index_nospec(fd, IO_RINGFD_REG_MAX);
-		file = tctx->registered_rings[fd];
-	} else {
-		file = fget(fd);
-	}
-
-	if (unlikely(!file))
-		return ERR_PTR(-EBADF);
-	if (io_is_uring_fops(file))
-		return file;
-	fput(file);
-	return ERR_PTR(-EOPNOTSUPP);
-}
-
 static int io_uring_register_send_msg_ring(void __user *arg, unsigned int nr_args)
 {
 	struct io_uring_sqe sqe;
@@ -1025,7 +992,7 @@ SYSCALL_DEFINE4(io_uring_register, unsigned int, fd, unsigned int, opcode,
 	if (fd == -1)
 		return io_uring_register_blind(opcode, arg, nr_args);
 
-	file = io_uring_register_get_file(fd, use_registered_ring);
+	file = io_uring_ctx_get_file(fd, use_registered_ring);
 	if (IS_ERR(file))
 		return PTR_ERR(file);
 	ctx = file->private_data;

io_uring/register.h

@@ -4,6 +4,5 @@
 
 int io_eventfd_unregister(struct io_ring_ctx *ctx);
 int io_unregister_personality(struct io_ring_ctx *ctx, unsigned id);
-struct file *io_uring_register_get_file(unsigned int fd, bool registered);
 
 #endif

io_uring/rsrc.c

@@ -1269,7 +1269,7 @@ int io_register_clone_buffers(struct io_ring_ctx *ctx, void __user *arg)
 		return -EINVAL;
 
 	registered_src = (buf.flags & IORING_REGISTER_SRC_REGISTERED) != 0;
-	file = io_uring_register_get_file(buf.src_fd, registered_src);
+	file = io_uring_ctx_get_file(buf.src_fd, registered_src);
 	if (IS_ERR(file))
 		return PTR_ERR(file);