autofs4 - fix get_next_positive_dentry()

The initialization condition in fs/autofs4/expire.c:get_next_positive_dentry()
appears to be incorrect. If prev == NULL I believe that root should be
returned.

Further down, at the current dentry check for it being simple_positive()
it looks like the d_lock for dentry p should be dropped instead of dentry
ret, otherwise when p is assinged to ret we end up with no lock on p and
a lost lock on ret, which leads to a deadlock.

Signed-off-by: Ian Kent <raven@themaw.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 2 insertions, 2 deletions

diff --git a/fs/autofs4/expire.c b/fs/autofs4/expire.c
index 3ed79d76c233..f43100b9662b 100644
--- a/fs/autofs4/expire.c
+++ b/fs/autofs4/expire.c
@@ -96,7 +96,7 @@ static struct dentry *get_next_positive_dentry(struct dentry *prev,
         struct dentry *p, *ret;
 
         if (prev == NULL)
-                return dget(prev);
+                return dget(root);
 
         spin_lock(&autofs4_lock);
 relock:
@@ -133,7 +133,7 @@ again:
         spin_lock_nested(&ret->d_lock, DENTRY_D_LOCK_NESTED);
         /* Negative dentry - try next */
         if (!simple_positive(ret)) {
-                spin_unlock(&ret->d_lock);
+                spin_unlock(&p->d_lock);
                 p = ret;
                 goto again;
         }