From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 03024C3276C for ; Thu, 2 Jan 2020 22:39:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CA471217F4 for ; Thu, 2 Jan 2020 22:39:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1578004758; bh=0Uf6/eakuHv0RxJRP5QLczbHPxCFOinkZd+1IggRG1o=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=CfyKpdrHc1JyUvYwrQNtoqb5EbwcTsWIWuhIb3sCnLhQnENqcAsGHQtooawRbiHQh 2XRxcRQObvCs70O6GBvYNZvKkTIsCmBuTgSAne10+hSe3/erHhGNeFxOxuHR6OxczB 4znqdMlWOcI87uFB4Yt0Ty0LU5YxOY39zhYGlWIQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731444AbgABWjR (ORCPT ); Thu, 2 Jan 2020 17:39:17 -0500 Received: from mail.kernel.org ([198.145.29.99]:54930 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731075AbgABWjQ (ORCPT ); Thu, 2 Jan 2020 17:39:16 -0500 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id E6421217F4; Thu, 2 Jan 2020 22:39:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1578004755; bh=0Uf6/eakuHv0RxJRP5QLczbHPxCFOinkZd+1IggRG1o=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=q3I7NqlDUHxrhGBGt/YFutU/QVfipgzKlOnbr+yzkpvE4Z/2FIKGPsZrmWl22WK6E tHSXRzsxtDslY1vnR+w5+GaQP3yoIqhs6qC+vzzM1auU2BgQqBN0m990uCuXEOLhwB LsANSmVDhghmVnsUMtcAVZmm5hsGbifLEhWGBSZs= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Coly Li , Jens Axboe , Sasha Levin Subject: [PATCH 4.4 114/137] bcache: at least try to shrink 1 node in bch_mca_scan() Date: Thu, 2 Jan 2020 23:08:07 +0100 Message-Id: <20200102220602.500489232@linuxfoundation.org> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20200102220546.618583146@linuxfoundation.org> References: <20200102220546.618583146@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Coly Li [ Upstream commit 9fcc34b1a6dd4b8e5337e2b6ef45e428897eca6b ] In bch_mca_scan(), the number of shrinking btree node is calculated by code like this, unsigned long nr = sc->nr_to_scan; nr /= c->btree_pages; nr = min_t(unsigned long, nr, mca_can_free(c)); variable sc->nr_to_scan is number of objects (here is bcache B+tree nodes' number) to shrink, and pointer variable sc is sent from memory management code as parametr of a callback. If sc->nr_to_scan is smaller than c->btree_pages, after the above calculation, variable 'nr' will be 0 and nothing will be shrunk. It is frequeently observed that only 1 or 2 is set to sc->nr_to_scan and make nr to be zero. Then bch_mca_scan() will do nothing more then acquiring and releasing mutex c->bucket_lock. This patch checkes whether nr is 0 after the above calculation, if 0 is the result then set 1 to variable 'n'. Then at least bch_mca_scan() will try to shrink a single B+tree node. Signed-off-by: Coly Li Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- drivers/md/bcache/btree.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c index 05aa3ac1381b..5c93582c71cc 100644 --- a/drivers/md/bcache/btree.c +++ b/drivers/md/bcache/btree.c @@ -686,6 +686,8 @@ static unsigned long bch_mca_scan(struct shrinker *shrink, * IO can always make forward progress: */ nr /= c->btree_pages; + if (nr == 0) + nr = 1; nr = min_t(unsigned long, nr, mca_can_free(c)); i = 0; -- 2.20.1