From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f70.google.com (mail-ed1-f70.google.com [209.85.208.70]) by kanga.kvack.org (Postfix) with ESMTP id B227A8E0002 for ; Mon, 14 Jan 2019 03:53:49 -0500 (EST) Received: by mail-ed1-f70.google.com with SMTP id t7so8661839edr.21 for ; Mon, 14 Jan 2019 00:53:49 -0800 (PST) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id e19-v6si623031ejd.292.2019.01.14.00.53.47 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 14 Jan 2019 00:53:47 -0800 (PST) From: Jan Kara Subject: [PATCH] vfs: Avoid softlockups in drop_pagecache_sb() Date: Mon, 14 Jan 2019 09:53:43 +0100 Message-Id: <20190114085343.15011-1-jack@suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Al Viro , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Jan Kara When superblock has lots of inodes without any pagecache (like is the case for /proc), drop_pagecache_sb() will iterate through all of them without dropping sb->s_inode_list_lock which can lead to softlockups (one of our customers hit this). Fix the problem by going to the slow path and doing cond_resched() in case the process needs rescheduling. Acked-by: Michal Hocko Signed-off-by: Jan Kara --- fs/drop_caches.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) Andrew, can you please merge this patch? Thanks! diff --git a/fs/drop_caches.c b/fs/drop_caches.c index 82377017130f..d31b6c72b476 100644 --- a/fs/drop_caches.c +++ b/fs/drop_caches.c @@ -21,8 +21,13 @@ static void drop_pagecache_sb(struct super_block *sb, void *unused) spin_lock(&sb->s_inode_list_lock); list_for_each_entry(inode, &sb->s_inodes, i_sb_list) { spin_lock(&inode->i_lock); + /* + * We must skip inodes in unusual state. We may also skip + * inodes without pages but we deliberately won't in case + * we need to reschedule to avoid softlockups. + */ if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) || - (inode->i_mapping->nrpages == 0)) { + (inode->i_mapping->nrpages == 0 && !need_resched())) { spin_unlock(&inode->i_lock); continue; } @@ -30,6 +35,7 @@ static void drop_pagecache_sb(struct super_block *sb, void *unused) spin_unlock(&inode->i_lock); spin_unlock(&sb->s_inode_list_lock); + cond_resched(); invalidate_mapping_pages(inode->i_mapping, 0, -1); iput(toput_inode); toput_inode = inode; -- 2.16.4 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=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 C5D80C43387 for ; Mon, 14 Jan 2019 08:53:50 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 8F04420659 for ; Mon, 14 Jan 2019 08:53:50 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8F04420659 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 169BF8E0003; Mon, 14 Jan 2019 03:53:50 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 117058E0002; Mon, 14 Jan 2019 03:53:50 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id F21F68E0003; Mon, 14 Jan 2019 03:53:49 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from mail-ed1-f70.google.com (mail-ed1-f70.google.com [209.85.208.70]) by kanga.kvack.org (Postfix) with ESMTP id B227A8E0002 for ; Mon, 14 Jan 2019 03:53:49 -0500 (EST) Received: by mail-ed1-f70.google.com with SMTP id t7so8661839edr.21 for ; Mon, 14 Jan 2019 00:53:49 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-original-authentication-results:x-gm-message-state:from:to:cc :subject:date:message-id; bh=8PXnpI1n+nt7o+3stMAN9ou5aftK8y+l8P9Y1mAnsr4=; b=K7mD5YiOhrFzc/8Ao1FP2R8eUTxQTj8apdrRMGl74HXP9TZ+OPPUsnYO/kdkv5YmOB 9hb9HIeVLcsqwV1BJenPeuFLPMDVzwdrNl3t6JzaLppUe6UsBpb+IvAt1+VBJuV09KZR i5Nup/ZV79cJsgd+q4wjWlrZluxYD0TMiZav8qzQroeL3NgaLaBxUmU6Hv1suhUvu5Og ziRUzrNlmwNVRAtw5M+Ukly5s7buPjcFNh7I4dKIt0ftNC2cEWJIOff4jTlzHpw1gbV2 +pBBeX47mzpVcXS+ZTRgEcHsxdM8mpFYQbPDt1ACArsOkzN3iMZlKIk8IX+Da+nwCjUe FKlA== X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of jack@suse.cz designates 195.135.220.15 as permitted sender) smtp.mailfrom=jack@suse.cz X-Gm-Message-State: AJcUukdoXXLxG4hgeDBPO3aVlH+RaRaT3pcuax71nMxHkZT0lW5xU1MY l4vGH5dnic9Q7dZqNYsiSti0cQ0JjVD906V/G6ntJsk9jZJkaH82YkZceTVkQP/WlhtrY/xqr3L oNvNlEBr5GHwv4nl6G/xE2CW++pQJxtRAXOJfWO8ASgWW5zlHN/Zyomt4JzWauSQzUg== X-Received: by 2002:a50:903c:: with SMTP id b57mr22876839eda.161.1547456029204; Mon, 14 Jan 2019 00:53:49 -0800 (PST) X-Google-Smtp-Source: ALg8bN4kXKyfqSbgvRkCxYR9Z15zznv5uZ5+3enCuPfw/wFrbcSNu2COL10Ry6S0cRAZHbCSMu7Q X-Received: by 2002:a50:903c:: with SMTP id b57mr22876786eda.161.1547456027952; Mon, 14 Jan 2019 00:53:47 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1547456027; cv=none; d=google.com; s=arc-20160816; b=WIc/ju0H2KRax1Bm9qhW/H5oDS+crFKcj/rjFKb7MmOLaC/00QEAtcCsGreEct5xsY yhC7afBXdLu4mAe09R2knU8VcPkpbkdEzrMSv4nxj3W+fhwD2/NqgsxIynWFqBzc+JoT pgFF5pvk/4DqnSpNEZ4mDhr9DkpoJoHrsvouOId82dq1kC2yEWDW6dWKZCRkebxUF/Ad yR1/jSTUYVAHW+e6hBAF1NIBWJkHr62romAjOyr7e/ufYHTs9DBX2SxUDEfYwpeKp1Eb bDkGlSgz/ftNcnlBCCCo/j52R7vwSl72gfheviXLqAzivKsHcQga7KrLUz8d3tEIw5/U rWRw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=message-id:date:subject:cc:to:from; bh=8PXnpI1n+nt7o+3stMAN9ou5aftK8y+l8P9Y1mAnsr4=; b=M41FCqNzbBPwnV/Y5aYgM2jeoof6pG4zbJBlDDxNpPVFhpBCQA4dkM0vbOV1WLFnn/ YWJlrqOA0xmhzU/Hbrd8S/zbcKWnd8giS4473sZUSbT+PMaCLQzlDT66hHT/PtESGvh5 msrNireTkIbY+OYAMHfxxhonHFGz/tyhmGcH2Euy6D9cJgSnbYIq1E9OXib4rUZ4X1VX rWFfCmm4ZpYvUF1A8nht2G1e2fyJ+40pTCXqiBSj+XiRb/QpWWUUCs7p/7sR9a38W/lC wKqpA8e7dB2fC9bPZ9dkH4Ygjd6wxUMep/pSgdkIx/lur+lyYS7wljXIo+QKtA90wI+m damQ== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of jack@suse.cz designates 195.135.220.15 as permitted sender) smtp.mailfrom=jack@suse.cz Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id e19-v6si623031ejd.292.2019.01.14.00.53.47 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 14 Jan 2019 00:53:47 -0800 (PST) Received-SPF: pass (google.com: domain of jack@suse.cz designates 195.135.220.15 as permitted sender) client-ip=195.135.220.15; Authentication-Results: mx.google.com; spf=pass (google.com: domain of jack@suse.cz designates 195.135.220.15 as permitted sender) smtp.mailfrom=jack@suse.cz X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 278D1AC24; Mon, 14 Jan 2019 08:53:47 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id E0E7E1E157A; Mon, 14 Jan 2019 09:53:46 +0100 (CET) From: Jan Kara To: Andrew Morton Cc: Al Viro , , , Jan Kara Subject: [PATCH] vfs: Avoid softlockups in drop_pagecache_sb() Date: Mon, 14 Jan 2019 09:53:43 +0100 Message-Id: <20190114085343.15011-1-jack@suse.cz> X-Mailer: git-send-email 2.16.4 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Content-Type: text/plain; charset="UTF-8" Message-ID: <20190114085343.yadRcp5VZa2RXgdRFw-QphE-Uu6_GYE2asK52Fo1m4A@z> When superblock has lots of inodes without any pagecache (like is the case for /proc), drop_pagecache_sb() will iterate through all of them without dropping sb->s_inode_list_lock which can lead to softlockups (one of our customers hit this). Fix the problem by going to the slow path and doing cond_resched() in case the process needs rescheduling. Acked-by: Michal Hocko Signed-off-by: Jan Kara --- fs/drop_caches.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) Andrew, can you please merge this patch? Thanks! diff --git a/fs/drop_caches.c b/fs/drop_caches.c index 82377017130f..d31b6c72b476 100644 --- a/fs/drop_caches.c +++ b/fs/drop_caches.c @@ -21,8 +21,13 @@ static void drop_pagecache_sb(struct super_block *sb, void *unused) spin_lock(&sb->s_inode_list_lock); list_for_each_entry(inode, &sb->s_inodes, i_sb_list) { spin_lock(&inode->i_lock); + /* + * We must skip inodes in unusual state. We may also skip + * inodes without pages but we deliberately won't in case + * we need to reschedule to avoid softlockups. + */ if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) || - (inode->i_mapping->nrpages == 0)) { + (inode->i_mapping->nrpages == 0 && !need_resched())) { spin_unlock(&inode->i_lock); continue; } @@ -30,6 +35,7 @@ static void drop_pagecache_sb(struct super_block *sb, void *unused) spin_unlock(&inode->i_lock); spin_unlock(&sb->s_inode_list_lock); + cond_resched(); invalidate_mapping_pages(inode->i_mapping, 0, -1); iput(toput_inode); toput_inode = inode; -- 2.16.4