We unhash the dentry (in a subsequent patch) in ->d_revalidate() in order

to send mount requests to ->lookup().  But then we can not rely on
d_unhased() to give reliable results because it may be called at any time
by any code path.  The d_unhashed() function is used by __simple_empty()
in the path walking callbacks but autofs mount point dentrys should have
no directories at all so a list_empty() on d_subdirs should be (and is)
sufficient.
Signed-off-by: Ian Kent <raven@themaw.net>
Cc: Sage Weil <sage@newdream.net>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Andreas Dilger <adilger@sun.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Yehuda Saheh <yehuda@newdream.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

fs/autofs4/root.c

@@ -133,7 +133,7 @@ static int autofs4_dir_open(struct inode *inode, struct file *file)
 	 * it.
 	 */
 	spin_lock(&dcache_lock);
-	if (!d_mountpoint(dentry) && __simple_empty(dentry)) {
+	if (!d_mountpoint(dentry) && list_empty(&dentry->d_subdirs)) {
 		spin_unlock(&dcache_lock);
 		return -ENOENT;
 	}
@@ -257,7 +257,7 @@ static void *autofs4_follow_link(struct dentry *dentry, struct nameidata *nd)
 	 * mount it again.
 	 */
 	if (ino->flags & AUTOFS_INF_PENDING ||
-	    (!d_mountpoint(dentry) && __simple_empty(dentry))) {
+	    (!d_mountpoint(dentry) && list_empty(&dentry->d_subdirs))) {
 		spin_unlock(&dcache_lock);
 		spin_unlock(&sbi->fs_lock);
 
@@ -340,8 +340,7 @@ static int autofs4_revalidate(struct dentry *dentry, struct nameidata *nd)
 	/* Check for a non-mountpoint directory with no contents */
 	spin_lock(&dcache_lock);
 	if (S_ISDIR(dentry->d_inode->i_mode) &&
-	    !d_mountpoint(dentry) && 
-	    __simple_empty(dentry)) {
+	    !d_mountpoint(dentry) && list_empty(&dentry->d_subdirs)) {
 		DPRINTK("dentry=%p %.*s, emptydir",
 			 dentry, dentry->d_name.len, dentry->d_name.name);
 		spin_unlock(&dcache_lock);