[PATCH] Fix dcache deadlock introduced by previous fix

So the fix for our problems is:

 a) in fs/namei.c replace d_unhash() with a safe version.
 b) in fs/nfs/dir.c replace d_drop(dentry) in beginning of nfs_unlink()
 with list_del_init(&dentry->d_hash);

fs/namei.c

@@ -1496,14 +1496,18 @@ asmlinkage long sys_mkdir(const char * pathname, int mode)
 static void d_unhash(struct dentry *dentry)
 {
 	dget(dentry);
+	spin_lock(&dcache_lock);
 	switch (atomic_read(&dentry->d_count)) {
 	default:
+		spin_unlock(&dcache_lock);
 		shrink_dcache_parent(dentry);
+		spin_lock(&dcache_lock);
 		if (atomic_read(&dentry->d_count) != 2)
 			break;
 	case 2:
-		d_drop(dentry);
+		list_del_init(&dentry->d_hash);
 	}
+	spin_unlock(&dcache_lock);
 }
 
 int vfs_rmdir(struct inode *dir, struct dentry *dentry)

fs/nfs/dir.c

@@ -878,7 +878,7 @@ static int nfs_unlink(struct inode *dir, struct dentry *dentry)
 		return error;
 	}
 	if (!d_unhashed(dentry)) {
-		d_drop(dentry);
+		list_del_init(&dentry->d_hash);
 		need_rehash = 1;
 	}
 	spin_unlock(&dcache_lock);