autofs4: don't release directory mutex if called in oz_mode

Since we now delay hashing of dentrys until the ->mkdir() call, droping
and re-taking the directory mutex within the ->lookup() function when we
are being called by user space is not needed.  This can lead to a race
when other processes are attempting to access the same directory during
mount point directory creation.

In this case we need to hang onto the mutex to ensure we don't get user
processes trying to create a mount request for a newly created dentry
after the mount point entry has already been created.  This ensures that
when we need to check a dentry passed to autofs4_wait(), if it is hashed,
it is always the mount point dentry and not a new dentry created by
another lookup during directory creation.

Signed-off-by: Ian Kent <raven@themaw.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c
index 324290c682752cc87d98d01ea6cba7067e2fe999..1e901e5ea0139630091024b4a203ae1a7261a3c0 100644 (file)
--- a/fs/autofs4/root.c
+++ b/fs/autofs4/root.c
@@ -686,12 +686,11 @@ static struct dentry *autofs4_lookup(struct inode *dir, struct dentry *dentry, s
                spin_lock(&dentry->d_lock);
                dentry->d_flags |= DCACHE_AUTOFS_PENDING;
                spin_unlock(&dentry->d_lock);
-       }
-
-       if (dentry->d_op && dentry->d_op->d_revalidate) {
-               mutex_unlock(&dir->i_mutex);
-               (dentry->d_op->d_revalidate)(dentry, nd);
-               mutex_lock(&dir->i_mutex);
+               if (dentry->d_op && dentry->d_op->d_revalidate) {
+                       mutex_unlock(&dir->i_mutex);
+                       (dentry->d_op->d_revalidate)(dentry, nd);
+                       mutex_lock(&dir->i_mutex);
+               }
        }
 
        /*