[PATCH] sanitize the interface of graft_tree().

Old semantics: graft_tree() grabs a reference on the vfsmount before
returning success.

New one: graft_tree() leaves that to caller.

All the callers of graft_tree() immediately dropped that reference
anyway.  Changing the interface takes care of this unnecessary overhead.

Idea proposed by Al Viro.

Signed-off-by: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/fs/namespace.c b/fs/namespace.c
index 685687d..dfeeab9 100644 (file)
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -650,7 +650,6 @@ static int graft_tree(struct vfsmount *mnt, struct nameidata *nd)
                attach_mnt(mnt, nd);
                list_add_tail(&head, &mnt->mnt_list);
                list_splice(&head, current->namespace->list.prev);
-               mntget(mnt);
                err = 0;
                touch_namespace(current->namespace);
        }
@@ -702,8 +701,7 @@ static int do_loopback(struct nameidata *nd, char *old_name, int recurse)
                spin_lock(&vfsmount_lock);
                umount_tree(mnt);
                spin_unlock(&vfsmount_lock);
-       } else
-               mntput(mnt);
+       }
 
 out:
        up_write(&current->namespace->sem);
@@ -857,15 +855,17 @@ int do_add_mount(struct vfsmount *newmnt, struct nameidata *nd,
                goto unlock;
 
        newmnt->mnt_flags = mnt_flags;
-       newmnt->mnt_namespace = current->namespace;
-       err = graft_tree(newmnt, nd);
+       if ((err = graft_tree(newmnt, nd)))
+               goto unlock;
 
-       if (err == 0 && fslist) {
+       if (fslist) {
                /* add to the specified expiration list */
                spin_lock(&vfsmount_lock);
                list_add_tail(&newmnt->mnt_expire, fslist);
                spin_unlock(&vfsmount_lock);
        }
+       up_write(&current->namespace->sem);
+       return 0;
 
 unlock:
        up_write(&current->namespace->sem);