vfs: fix out-of-date dentry_unhash() comment

64252c75a2196a0cf1e0d3777143ecfe0e3ae650 "vfs: remove dget() from
dentry_unhash()" changed the implementation but not the comment.

Cc: Sage Weil <sage@newdream.net>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/namei.c

@@ -2710,7 +2710,7 @@ SYSCALL_DEFINE2(mkdir, const char __user *, pathname, umode_t, mode)
 
 /*
  * The dentry_unhash() helper will try to drop the dentry early: we
- * should have a usage count of 2 if we're the only user of this
+ * should have a usage count of 1 if we're the only user of this
  * dentry, and if that is true (possibly after pruning the dcache),
  * then we drop the dentry now.
  *