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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 89E1EC2D0CA for ; Wed, 11 Dec 2019 15:44:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6010522B48 for ; Wed, 11 Dec 2019 15:44:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1576079049; bh=U84ZNHixRNIXDS9D0nb/oECrd87iSqTnflwQv0O7Tb0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=IpIizwVzfLFijuxmkw6sBn76Fb4J4FWjra5pqgduEO1i60jKzeZqwz7LdZsJ3pjBA tYyooCB9Ma1C7PxszKjbVRAHZ51fI8C2yXjZT4h31BguApJC21QzK3jPxe6dhXqxzK AFBAIpFH3ota2eeUkDo1pIefXVYPDZP0J3srKImI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732461AbfLKPnv (ORCPT ); Wed, 11 Dec 2019 10:43:51 -0500 Received: from mail.kernel.org ([198.145.29.99]:33288 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732851AbfLKP1e (ORCPT ); Wed, 11 Dec 2019 10:27:34 -0500 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id B756422527; Wed, 11 Dec 2019 15:27:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1576078053; bh=U84ZNHixRNIXDS9D0nb/oECrd87iSqTnflwQv0O7Tb0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=GrTeXSFQRc+OTom7wiBkp3ARvYS9V3LJVf7kgDyBLiirOxxPPUprIrN2Pkuq9uRQE SsL4bFhIZFryF7M+YPliVFdKHSCUO7aSZLjvypQ5AN5AfDXYFGJDB0XOF6rrD2vTu9 ZlU1SQIC57rmP543l1cDtIs1xy4REo18DuPUerKE= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Coly Li , Jens Axboe , Sasha Levin , linux-bcache@vger.kernel.org, linux-raid@vger.kernel.org Subject: [PATCH AUTOSEL 4.19 46/79] bcache: at least try to shrink 1 node in bch_mca_scan() Date: Wed, 11 Dec 2019 10:26:10 -0500 Message-Id: <20191211152643.23056-46-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20191211152643.23056-1-sashal@kernel.org> References: <20191211152643.23056-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore 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 45f684689c357..bb40bd66a10e4 100644 --- a/drivers/md/bcache/btree.c +++ b/drivers/md/bcache/btree.c @@ -713,6 +713,8 @@ 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