btrfs: use correct compare function of dirty_metadata_bytes

commit d814a49 upstream.

We use customized, nodesize batch value to update dirty_metadata_bytes.
We should also use batch version of compare function or we will easily
goto fast path and get false result from percpu_counter_compare().

Fixes: e2d8452 ("Btrfs: use percpu counter for dirty metadata count")
CC: stable@vger.kernel.org # 4.4+
Signed-off-by: Ethan Lien <ethanlien@synology.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
nb: Rebased on 4.4.y ]
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Ethan Lien

fs/btrfs/disk-io.c

@@ -1096,8 +1096,9 @@ static int btree_writepages(struct address_space *mapping,
 
 		fs_info = BTRFS_I(mapping->host)->root->fs_info;
 		/* this is a bit racy, but that's ok */
-		ret = percpu_counter_compare(&fs_info->dirty_metadata_bytes,
-					     BTRFS_DIRTY_METADATA_THRESH);
+		ret = __percpu_counter_compare(&fs_info->dirty_metadata_bytes,
+					     BTRFS_DIRTY_METADATA_THRESH,
+					     fs_info->dirty_metadata_batch);
 		if (ret < 0)
 			return 0;
 	}
@@ -4107,8 +4108,9 @@ static void __btrfs_btree_balance_dirty(struct btrfs_root *root,
 	if (flush_delayed)
 		btrfs_balance_delayed_items(root);
 
-	ret = percpu_counter_compare(&root->fs_info->dirty_metadata_bytes,
-				     BTRFS_DIRTY_METADATA_THRESH);
+	ret = __percpu_counter_compare(&root->fs_info->dirty_metadata_bytes,
+				     BTRFS_DIRTY_METADATA_THRESH,
+				     root->fs_info->dirty_metadata_batch);
 	if (ret > 0) {
 		balance_dirty_pages_ratelimited(
 				   root->fs_info->btree_inode->i_mapping);