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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 D4492C3B186 for ; Tue, 11 Feb 2020 12:23:30 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 952BF2082F for ; Tue, 11 Feb 2020 12:23:30 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="K5QSdqCI" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 952BF2082F Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 259236B02C2; Tue, 11 Feb 2020 07:23:30 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 2097B6B02C3; Tue, 11 Feb 2020 07:23:30 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 11EF56B02C4; Tue, 11 Feb 2020 07:23:30 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0191.hostedemail.com [216.40.44.191]) by kanga.kvack.org (Postfix) with ESMTP id EACEE6B02C2 for ; Tue, 11 Feb 2020 07:23:29 -0500 (EST) Received: from smtpin04.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 84E7B40D0 for ; Tue, 11 Feb 2020 12:23:29 +0000 (UTC) X-FDA: 76477761738.04.rail56_75bee1597e43a X-HE-Tag: rail56_75bee1597e43a X-Filterd-Recvd-Size: 4228 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) by imf12.hostedemail.com (Postfix) with ESMTP for ; Tue, 11 Feb 2020 12:23:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=Rju0YMUliA+K5t2+7HZEye0ub0QWZvZnf/MHQT2LoNY=; b=K5QSdqCIgc+e9Hb2+rNsp40BvP aokArzKbETkw17m3M38rq1DB4eL2mvo7aF9TSt/vcbNIce7g9jWAOQGyfwJ0r/8Ec5mateJ6+XUXU 2YnhpGl5EVMBeqR2Qw9ZvS1dNTP2FcDp9drpoN+3y/HbiBawT51JZMA7ynDN4e5G4eOiTGfsZ+RGe jl/iGjqKRmbWu7vp2PFvaqesoLXCO3nrNrnKRf64ebQR35LzAjuQKrd/oq0J3YXJ1NqiLJI6bBBap XTSwZhF6Y1JgAX6FEXAkE5E2zOayLSsIioZohrxOBLdhdaqrx5Pz6YUwncWkB/lldUiXrTTC11jvu g2I/jAvg==; Received: from willy by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1j1UZX-0001WR-Ib; Tue, 11 Feb 2020 12:23:23 +0000 Date: Tue, 11 Feb 2020 04:23:23 -0800 From: Matthew Wilcox To: Minchan Kim Cc: Andrew Morton , linux-mm , Josef Bacik , Johannes Weiner , Jan Kara , LKML Subject: Re: [PATCH] mm: fix long time stall from mm_populate Message-ID: <20200211122323.GS8731@bombadil.infradead.org> References: <20200211001958.170261-1-minchan@kernel.org> <20200211011021.GP8731@bombadil.infradead.org> <20200211035004.GA242563@google.com> <20200211035412.GR8731@bombadil.infradead.org> <20200211042536.GB242563@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200211042536.GB242563@google.com> 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 Mon, Feb 10, 2020 at 08:25:36PM -0800, Minchan Kim wrote: > On Mon, Feb 10, 2020 at 07:54:12PM -0800, Matthew Wilcox wrote: > > On Mon, Feb 10, 2020 at 07:50:04PM -0800, Minchan Kim wrote: > > > On Mon, Feb 10, 2020 at 05:10:21PM -0800, Matthew Wilcox wrote: > > > > On Mon, Feb 10, 2020 at 04:19:58PM -0800, Minchan Kim wrote: > > > > > filemap_fault > > > > > find a page form page(PG_uptodate|PG_readahead|PG_writeback) > > > > > > > > Uh ... That shouldn't be possible. > > > > > > Please see shrink_page_list. Vmscan uses PG_reclaim to accelerate > > > page reclaim when the writeback is done so the page will have both > > > flags at the same time and the PG reclaim could be regarded as > > > PG_readahead in fault conext. > > > > What part of fault context can make that mistake? The snippet I quoted > > below is from page_cache_async_readahead() where it will clearly not > > make that mistake. There's a lot of code here; please don't presume I > > know all the areas you're talking about. > > Sorry about being not clear. I am saying filemap_fault -> > do_async_mmap_readahead > > Let's assume the page is hit in page cache and vmf->flags is !FAULT_FLAG > TRIED so it calls do_async_mmap_readahead. Since the page has PG_reclaim > and PG_writeback by shrink_page_list, it goes to > > do_async_mmap_readahead > if (PageReadahead(page)) > fpin = maybe_unlock_mmap_for_io(); > page_cache_async_readahead > if (PageWriteback(page)) > return; > ClearPageReadahead(page); <- doesn't reach here until the writeback is clear > > So, mm_populate will repeat the loop until the writeback is done. > It's my just theory but didn't comfirm it by the testing. > If I miss something clear, let me know it. Ah! Surely the right way to fix this is ... +++ b/mm/filemap.c @@ -2420,7 +2420,7 @@ static struct file *do_async_mmap_readahead(struct vm_fault *vmf, return fpin; if (ra->mmap_miss > 0) ra->mmap_miss--; - if (PageReadahead(page)) { + if (!PageWriteback(page) && PageReadahead(page)) { fpin = maybe_unlock_mmap_for_io(vmf, fpin); page_cache_async_readahead(mapping, ra, file, page, offset, ra->ra_pages);