vfs: add helpers to get root and pwd

Add three helpers that retrieve a refcounted copy of the root and cwd
from the supplied fs_struct.

 get_fs_root()
 get_fs_pwd()
 get_fs_root_and_pwd()

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 1 insertions, 4 deletions

diff --git a/fs/namespace.c b/fs/namespace.c
index 66c4f7e781cb..7972e51ccc06 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2213,10 +2213,7 @@ SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
 		goto out1;
 	}
 
-	read_lock(&current->fs->lock);
-	root = current->fs->root;
-	path_get(&current->fs->root);
-	read_unlock(&current->fs->lock);
+	get_fs_root(current->fs, &root);
 	down_write(&namespace_sem);
 	mutex_lock(&old.dentry->d_inode->i_mutex);
 	error = -EINVAL;