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=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 62850C55191 for ; Thu, 23 Apr 2020 15:58:57 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 25BCE2073A for ; Thu, 23 Apr 2020 15:58:57 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 25BCE2073A 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 AEAE48E0005; Thu, 23 Apr 2020 11:58:56 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A9ABD8E0003; Thu, 23 Apr 2020 11:58:56 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9D74B8E0005; Thu, 23 Apr 2020 11:58:56 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0110.hostedemail.com [216.40.44.110]) by kanga.kvack.org (Postfix) with ESMTP id 861618E0003 for ; Thu, 23 Apr 2020 11:58:56 -0400 (EDT) Received: from smtpin25.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 44424180AD81F for ; Thu, 23 Apr 2020 15:58:56 +0000 (UTC) X-FDA: 76739578272.25.snail84_4dfba1a877206 X-HE-Tag: snail84_4dfba1a877206 X-Filterd-Recvd-Size: 2671 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf28.hostedemail.com (Postfix) with ESMTP for ; Thu, 23 Apr 2020 15:58:55 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 7C3EBAD0E; Thu, 23 Apr 2020 15:58:53 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id ABCA71E0E52; Thu, 23 Apr 2020 17:58:53 +0200 (CEST) Date: Thu, 23 Apr 2020 17:58:53 +0200 From: Jan Kara To: Matthew Wilcox Cc: linux-mm@kvack.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH v3 09/11] mm: Convert writeback BUG to WARN_ON Message-ID: <20200423155853.GC28707@quack2.suse.cz> References: <20200416220130.13343-1-willy@infradead.org> <20200416220130.13343-10-willy@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200416220130.13343-10-willy@infradead.org> User-Agent: Mutt/1.10.1 (2018-07-13) 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: On Thu 16-04-20 15:01:28, Matthew Wilcox wrote: > From: "Matthew Wilcox (Oracle)" > > If this BUG() ever triggers, we'll have a dead system with no particular > information. Dumping the page will give us a fighting chance of debugging > the problem, and I think it's safe for us to just continue if we try > to clear the writeback bit on a page which already has the writeback > bit clear. > > Signed-off-by: Matthew Wilcox (Oracle) > --- > mm/filemap.c | 4 +--- > mm/page-writeback.c | 5 +++++ > 2 files changed, 6 insertions(+), 3 deletions(-) > > diff --git a/mm/filemap.c b/mm/filemap.c > index b7c5d2402370..401b24d980ba 100644 > --- a/mm/filemap.c > +++ b/mm/filemap.c > @@ -1293,9 +1293,7 @@ void end_page_writeback(struct page *page) > rotate_reclaimable_page(page); > } > > - if (!test_clear_page_writeback(page)) > - BUG(); > - > + test_clear_page_writeback(page); > smp_mb__after_atomic(); > wake_up_page(page, PG_writeback); > } > diff --git a/mm/page-writeback.c b/mm/page-writeback.c > index 7326b54ab728..ebaf0d8263a6 100644 > --- a/mm/page-writeback.c > +++ b/mm/page-writeback.c > @@ -2718,6 +2718,11 @@ int test_clear_page_writeback(struct page *page) > struct lruvec *lruvec; > int ret; > > + if (WARN_ON(!PageWriteback(page))) { > + dump_page(page, "!writeback"); > + return false; > + } > + WARN_ON_ONCE() here perhaps? I don't think dumping more pages will bring that much value... Honza -- Jan Kara SUSE Labs, CR