Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753764AbbKBLFl (ORCPT ); Mon, 2 Nov 2015 06:05:41 -0500 Received: from mail-wm0-f42.google.com ([74.125.82.42]:35496 "EHLO mail-wm0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753720AbbKBLFg (ORCPT ); Mon, 2 Nov 2015 06:05:36 -0500 Message-ID: <5637437C.4070306@electrozaur.com> Date: Mon, 02 Nov 2015 13:05:32 +0200 From: Boaz Harrosh User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 MIME-Version: 1.0 To: Hugh Dickins CC: Andrew Morton , Trond Myklebust , Christoph Lameter , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nfs@vger.kernel.org, linux-mm@kvack.org, osd-dev@open-osd.org Subject: Re: [PATCH] osd fs: __r4w_get_page rely on PageUptodate for uptodate References: <5635E2B4.5070308@electrozaur.com> In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1350 Lines: 44 On 11/02/2015 01:39 AM, Hugh Dickins wrote: <> >> This patch is not correct! > > I think you have actually confirmed that the patch is correct: > why bother to test PageDirty or PageWriteback when PageUptodate > already tells you what you need? > > Or do these filesystems do something unusual with PageUptodate > when PageDirty is set? I didn't find it. > This is kind of delicate stuff. It took me a while to get it right when I did it. I don't remember all the details. But consider this option: exofs_write_begin on a full PAGE_CACHE_SIZE, the page is instantiated new in page-cache is that PageUptodate(page) then? I thought not. (exofs does not set that) Now that page I do not want to read in. The latest data is in memory. (Same when this page is in writeback, dirty-bit is cleared) So for sure if page is dirty or writeback then we surly do not need a read. only if not then we need to consider the PageUptodate(page) state. Do you think the code is actually wrong as is? BTW: Very similar code is in fs/nfs/objlayout/objio_osd.c::__r4w_get_page > Thanks, > Hugh > <> Thanks Boaz -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/