file: remove pointless wrapper

Only io_uring uses __close_fd_get_file(). All it does is hide
current->files but io_uring accesses files_struct directly right now
anyway so it's a bit pointless. Just rename pick_file() to
file_close_fd_locked() and let io_uring use it. Add a lockdep assert in
there that we expect the caller to hold file_lock while we're at it.

Link: https://lore.kernel.org/r/20231130-vfs-files-fixes-v1-2-e73ca6f4ea83@kernel.orgReviewed-by: Jens Axboe <axboe@kernel.dk>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>

fs/file.c

@@ -629,19 +629,23 @@ void fd_install(unsigned int fd, struct file *file)
 EXPORT_SYMBOL(fd_install);
 
 /**
- * pick_file - return file associatd with fd
+ * file_close_fd_locked - return file associated with fd
  * @files: file struct to retrieve file from
  * @fd: file descriptor to retrieve file for
  *
+ * Doesn't take a separate reference count.
+ *
  * Context: files_lock must be held.
  *
  * Returns: The file associated with @fd (NULL if @fd is not open)
  */
-static struct file *pick_file(struct files_struct *files, unsigned fd)
+struct file *file_close_fd_locked(struct files_struct *files, unsigned fd)
 {
 	struct fdtable *fdt = files_fdtable(files);
 	struct file *file;
 
+	lockdep_assert_held(&files->file_lock);
+
 	if (fd >= fdt->max_fds)
 		return NULL;
 
@@ -660,7 +664,7 @@ int close_fd(unsigned fd)
 	struct file *file;
 
 	spin_lock(&files->file_lock);
-	file = pick_file(files, fd);
+	file = file_close_fd_locked(files, fd);
 	spin_unlock(&files->file_lock);
 	if (!file)
 		return -EBADF;
@@ -707,7 +711,7 @@ static inline void __range_close(struct files_struct *files, unsigned int fd,
 	max_fd = min(max_fd, n);
 
 	for (; fd <= max_fd; fd++) {
-		file = pick_file(files, fd);
+		file = file_close_fd_locked(files, fd);
 		if (file) {
 			spin_unlock(&files->file_lock);
 			filp_close(file, files);
@@ -795,15 +799,6 @@ int __close_range(unsigned fd, unsigned max_fd, unsigned int flags)
 	return 0;
 }
 
-/*
- * See file_close_fd() below, this variant assumes current->files->file_lock
- * is held.
- */
-struct file *__close_fd_get_file(unsigned int fd)
-{
-	return pick_file(current->files, fd);
-}
-
 /**
  * file_close_fd - return file associated with fd
  * @fd: file descriptor to retrieve file for
@@ -818,7 +813,7 @@ struct file *file_close_fd(unsigned int fd)
 	struct file *file;
 
 	spin_lock(&files->file_lock);
-	file = pick_file(files, fd);
+	file = file_close_fd_locked(files, fd);
 	spin_unlock(&files->file_lock);
 
 	return file;

fs/internal.h

@@ -179,7 +179,7 @@ extern struct file *do_file_open_root(const struct path *,
 		const char *, const struct open_flags *);
 extern struct open_how build_open_how(int flags, umode_t mode);
 extern int build_open_flags(const struct open_how *how, struct open_flags *op);
-extern struct file *__close_fd_get_file(unsigned int fd);
+struct file *file_close_fd_locked(struct files_struct *files, unsigned fd);
 
 long do_sys_ftruncate(unsigned int fd, loff_t length, int small);
 int chmod_common(const struct path *path, umode_t mode);

io_uring/openclose.c

@@ -241,7 +241,7 @@ int io_close(struct io_kiocb *req, unsigned int issue_flags)
 		return -EAGAIN;
 	}
 
-	file = __close_fd_get_file(close->fd);
+	file = file_close_fd_locked(files, close->fd);
 	spin_unlock(&files->file_lock);
 	if (!file)
 		goto err;