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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 5B8EBC433DB for ; Thu, 4 Mar 2021 00:21:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1A05A64E60 for ; Thu, 4 Mar 2021 00:21:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1355156AbhCDAUn (ORCPT ); Wed, 3 Mar 2021 19:20:43 -0500 Received: from mail.kernel.org ([198.145.29.99]:56968 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1387991AbhCCUNf (ORCPT ); Wed, 3 Mar 2021 15:13:35 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 55FA364EE7; Wed, 3 Mar 2021 20:12:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1614802374; bh=Xr/eJPdOmWhLdpnQyVVA+xkU185rLwaj41waSYr6VAs=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=V/eX1k7WlMR9lAcOp/w4yS8wqhnK3VY5Z3ZfAOr3g2LhlNIGbbMr/fzo5oVkdmyqt ZyvnYZmGXZ8RBBa5oxrRG8d7cUV5PfloPM0pJASQU4NxdtFLy7aL+yqh+tW6oDjm5R vazbDg7Ip6MThebfdhPuK3QzZEXqg7Khb618h4Wo= Date: Wed, 3 Mar 2021 12:12:53 -0800 From: Andrew Morton To: Matthew Wilcox Cc: linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, Kent Overstreet , Christoph Hellwig Subject: Re: [PATCH] mm/filemap: Use filemap_read_page in filemap_fault Message-Id: <20210303121253.9f44d8129f148b1e2e78cc81@linux-foundation.org> In-Reply-To: <20210303132640.GB2723601@casper.infradead.org> References: <20210226140011.2883498-1-willy@infradead.org> <20210302173039.4625f403846abd20413f6dad@linux-foundation.org> <20210303013313.GZ2723601@casper.infradead.org> <20210302220735.1f150f28323f676d2955ab49@linux-foundation.org> <20210303132640.GB2723601@casper.infradead.org> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Wed, 3 Mar 2021 13:26:40 +0000 Matthew Wilcox wrote: > But here's the thing ... invalidate_mapping_pages() doesn't > ClearPageUptodate. The only places where we ClearPageUptodate is on an > I/O error. yup. > So ... as far as I can tell, the only way to hit this is: > > - Get an I/O error during the wait > - Have another thread cause the page to be removed from the page cache > (eg do direct I/O to the file) before this thread is run. > > and the consequence to this change is that we have another attempt to > read the page instead of returning an error immediately. I'm OK with > that unintentional change, although I think the previous behaviour was > also perfectly acceptable (after all, there was an I/O error while trying > to read this page). > > Delving into the linux-fullhistory tree, this code was introduced by ... > > commit 56f0d5fe6851037214a041a5cb4fc66199256544 > Author: Andrew Morton > Date: Fri Jan 7 22:03:01 2005 -0800 > > [PATCH] readpage-vs-invalidate fix > > A while ago we merged a patch which tried to solve a problem wherein a > concurrent read() and invalidate_inode_pages() would cause the read() to > return -EIO because invalidate cleared PageUptodate() at the wrong time. > > We no longer clear PageUptodate, so I think this is stale code? Perhaps > you could check with the original author ... Which code do you think might be stale? We need the !PageUptodate check to catch IO errors and we need the !page->mapping check to catch invalidates. Am a bit confused.