[PATCH RFC v2 07/48] namespace: convert fsmount() to FD_PREPARE()

[Christian Brauner <brauner@kernel.org>]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 fs/namespace.c | 60 +++++++++++++++++++++++-----------------------------------
 1 file changed, 24 insertions(+), 36 deletions(-)

diff --git a/fs/namespace.c b/fs/namespace.c
index 2be135c8de05..03e991df1603 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -4278,8 +4278,7 @@ SYSCALL_DEFINE3(fsmount, int, fs_fd, unsigned int, flags,
 {
 	struct mnt_namespace *ns;
 	struct fs_context *fc;
-	struct file *file;
-	struct path newmount;
+	struct path newmount __free(path_put) = {};
 	struct mount *mnt;
 	unsigned int mnt_flags = 0;
 	long ret;
@@ -4317,33 +4316,32 @@ SYSCALL_DEFINE3(fsmount, int, fs_fd, unsigned int, flags,
 
 	fc = fd_file(f)->private_data;
 
-	ret = mutex_lock_interruptible(&fc->uapi_mutex);
-	if (ret < 0)
+	ACQUIRE(mutex_intr, uapi_mutex)(&fc->uapi_mutex);
+	ret = ACQUIRE_ERR(mutex_intr, &uapi_mutex);
+	if (ret)
 		return ret;
 
 	/* There must be a valid superblock or we can't mount it */
 	ret = -EINVAL;
 	if (!fc->root)
-		goto err_unlock;
+		return ret;
 
 	ret = -EPERM;
 	if (mount_too_revealing(fc->root->d_sb, &mnt_flags)) {
 		errorfcp(fc, "VFS", "Mount too revealing");
-		goto err_unlock;
+		return ret;
 	}
 
 	ret = -EBUSY;
 	if (fc->phase != FS_CONTEXT_AWAITING_MOUNT)
-		goto err_unlock;
+		return ret;
 
 	if (fc->sb_flags & SB_MANDLOCK)
 		warn_mandlock();
 
 	newmount.mnt = vfs_create_mount(fc);
-	if (IS_ERR(newmount.mnt)) {
-		ret = PTR_ERR(newmount.mnt);
-		goto err_unlock;
-	}
+	if (IS_ERR(newmount.mnt))
+		return PTR_ERR(newmount.mnt);
 	newmount.dentry = dget(fc->root);
 	newmount.mnt->mnt_flags = mnt_flags;
 
@@ -4355,38 +4353,28 @@ SYSCALL_DEFINE3(fsmount, int, fs_fd, unsigned int, flags,
 	vfs_clean_context(fc);
 
 	ns = alloc_mnt_ns(current->nsproxy->mnt_ns->user_ns, true);
-	if (IS_ERR(ns)) {
-		ret = PTR_ERR(ns);
-		goto err_path;
-	}
+	if (IS_ERR(ns))
+		return PTR_ERR(ns);
 	mnt = real_mount(newmount.mnt);
 	ns->root = mnt;
 	ns->nr_mounts = 1;
 	mnt_add_to_ns(ns, mnt);
 	mntget(newmount.mnt);
 
-	/* Attach to an apparent O_PATH fd with a note that we need to unmount
-	 * it, not just simply put it.
-	 */
-	file = dentry_open(&newmount, O_PATH, fc->cred);
-	if (IS_ERR(file)) {
-		dissolve_on_fput(newmount.mnt);
-		ret = PTR_ERR(file);
-		goto err_path;
-	}
-	file->f_mode |= FMODE_NEED_UNMOUNT;
-
-	ret = get_unused_fd_flags((flags & FSMOUNT_CLOEXEC) ? O_CLOEXEC : 0);
-	if (ret >= 0)
-		fd_install(ret, file);
-	else
-		fput(file);
+	FD_PREPARE(fdf, (flags & FSMOUNT_CLOEXEC) ? O_CLOEXEC : 0,
+		   dentry_open(&newmount, O_PATH, fc->cred)) {
+		if (fd_prepare_failed(fdf)) {
+			dissolve_on_fput(newmount.mnt);
+			return fd_prepare_error(fdf);
+		}
 
-err_path:
-	path_put(&newmount);
-err_unlock:
-	mutex_unlock(&fc->uapi_mutex);
-	return ret;
+		/*
+		 * Attach to an apparent O_PATH fd with a note that we
+		 * need to unmount it, not just simply put it.
+		 */
+		fd_prepare_file(fdf)->f_mode |= FMODE_NEED_UNMOUNT;
+		return fd_publish(fdf);
+	}
 }
 
 static inline int vfs_move_mount(const struct path *from_path,

-- 
2.47.3