nsfs: convert ns_ioctl() to FD_PREPARE()

Link: https://patch.msgid.link/20251123-work-fd-prepare-v4-10-b6efa1706cfd@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>

1 files changed, 12 insertions, 23 deletions

diff --git a/fs/nsfs.c b/fs/nsfs.c
index 339497b1c267..375390bf810d 100644
--- a/fs/nsfs.c
+++ b/fs/nsfs.c
@@ -301,7 +301,6 @@ static long ns_ioctl(struct file *filp, unsigned int ioctl,
 		struct mnt_ns_info kinfo = {};
 		struct mnt_ns_info __user *uinfo = (struct mnt_ns_info __user *)arg;
 		struct path path __free(path_put) = {};
-		struct file *f __free(fput) = NULL;
 		size_t usize = _IOC_SIZE(ioctl);
 
 		if (ns->ns_type != CLONE_NEWNS)
@@ -320,28 +319,18 @@ static long ns_ioctl(struct file *filp, unsigned int ioctl,
 		if (ret)
 			return ret;
 
-		CLASS(get_unused_fd, fd)(O_CLOEXEC);
-		if (fd < 0)
-			return fd;
-
-		f = dentry_open(&path, O_RDONLY, current_cred());
-		if (IS_ERR(f))
-			return PTR_ERR(f);
-
-		if (uinfo) {
-			/*
-			 * If @uinfo is passed return all information about the
-			 * mount namespace as well.
-			 */
-			ret = copy_ns_info_to_user(to_mnt_ns(ns), uinfo, usize, &kinfo);
-			if (ret)
-				return ret;
-		}
-
-		/* Transfer reference of @f to caller's fdtable. */
-		fd_install(fd, no_free_ptr(f));
-		/* File descriptor is live so hand it off to the caller. */
-		return take_fd(fd);
+		FD_PREPARE(fdf, O_CLOEXEC, dentry_open(&path, O_RDONLY, current_cred()));
+		if (fdf.err)
+			return fdf.err;
+		/*
+		 * If @uinfo is passed return all information about the
+		 * mount namespace as well.
+		 */
+		ret = copy_ns_info_to_user(to_mnt_ns(ns), uinfo, usize, &kinfo);
+		if (ret)
+			return ret;
+		ret = fd_publish(fdf);
+		break;
 	}
 	default:
 		ret = -ENOTTY;