vfat: simplify checks in vfat_lookup()

vfat_d_anon_disconn() is called only if alias->d_parent is equal to
dentry->d_parent *and* it returns false unless alias->d_parent == alias.
But in that case alias is the directory we are doing lookup in, and
d_splice_alias() would've done the right thing.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/fat/namei_vfat.c

@@ -697,15 +697,6 @@ static int vfat_find(struct inode *dir, const struct qstr *qname,
 	return fat_search_long(dir, qname->name, len, sinfo);
 }
 
-/*
- * (nfsd's) anonymous disconnected dentry?
- * NOTE: !IS_ROOT() is not anonymous (I.e. d_splice_alias() did the job).
- */
-static int vfat_d_anon_disconn(struct dentry *dentry)
-{
-	return IS_ROOT(dentry) && (dentry->d_flags & DCACHE_DISCONNECTED);
-}
-
 static struct dentry *vfat_lookup(struct inode *dir, struct dentry *dentry,
 				  unsigned int flags)
 {
@@ -738,8 +729,7 @@ static struct dentry *vfat_lookup(struct inode *dir, struct dentry *dentry,
 	 * Checking "alias->d_parent == dentry->d_parent" to make sure
 	 * FS is not corrupted (especially double linked dir).
 	 */
-	if (alias && alias->d_parent == dentry->d_parent &&
-	    !vfat_d_anon_disconn(alias)) {
+	if (alias && alias->d_parent == dentry->d_parent) {
 		/*
 		 * This inode has non anonymous-DCACHE_DISCONNECTED
 		 * dentry. This means, the user did ->lookup() by an
@@ -747,7 +737,6 @@ static struct dentry *vfat_lookup(struct inode *dir, struct dentry *dentry,
 		 *
 		 * Switch to new one for reason of locality if possible.
 		 */
-		BUG_ON(d_unhashed(alias));
 		if (!S_ISDIR(inode->i_mode))
 			d_move(alias, dentry);
 		iput(inode);