[PATCH] fix races and leaks in vfs_quota_on() users

[PATCH] fix races and leaks in vfs_quota_on() users

* new helper: vfs_quota_on_path(); equivalent of vfs_quota_on() sans the
  pathname resolution.
* callers of vfs_quota_on() that do their own pathname resolution and
  checks based on it are switched to vfs_quota_on_path(); that way we
  avoid the races.
* reiserfs leaked dentry/vfsmount references on several failure exits.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>