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=-8.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 A1A41C43465 for ; Fri, 18 Sep 2020 05:59:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5E9C220789 for ; Fri, 18 Sep 2020 05:59:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726637AbgIRF7j (ORCPT ); Fri, 18 Sep 2020 01:59:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33408 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725886AbgIRF7i (ORCPT ); Fri, 18 Sep 2020 01:59:38 -0400 Received: from nautica.notk.org (ipv6.notk.org [IPv6:2001:41d0:1:7a93::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 91853C06174A; Thu, 17 Sep 2020 22:59:38 -0700 (PDT) Received: by nautica.notk.org (Postfix, from userid 1001) id 5EAEFC01B; Fri, 18 Sep 2020 07:59:34 +0200 (CEST) Date: Fri, 18 Sep 2020 07:59:19 +0200 From: Dominique Martinet To: "Matthew Wilcox (Oracle)" Cc: linux-fsdevel@vger.kernel.org, linux-cifs@vger.kernel.org, Richard Weinberger , ecryptfs@vger.kernel.org, linux-um@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-mtd@lists.infradead.org, v9fs-developer@lists.sourceforge.net, ceph-devel@vger.kernel.org, linux-afs@lists.infradead.org Subject: Re: [V9fs-developer] [PATCH 02/13] 9p: Tell the VFS that readpage was synchronous Message-ID: <20200918055919.GA30929@nautica> References: <20200917151050.5363-1-willy@infradead.org> <20200917151050.5363-3-willy@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200917151050.5363-3-willy@infradead.org> User-Agent: Mutt/1.5.21 (2010-09-15) Precedence: bulk List-ID: X-Mailing-List: ceph-devel@vger.kernel.org Matthew Wilcox (Oracle) wrote on Thu, Sep 17, 2020: > diff --git a/fs/9p/vfs_addr.c b/fs/9p/vfs_addr.c > index cce9ace651a2..506ca0ba2ec7 100644 > --- a/fs/9p/vfs_addr.c > +++ b/fs/9p/vfs_addr.c > @@ -280,6 +280,10 @@ static int v9fs_write_begin(struct file *filp, struct address_space *mapping, > goto out; > > retval = v9fs_fid_readpage(v9inode->writeback_fid, page); > + if (retval == AOP_UPDATED_PAGE) { > + retval = 0; > + goto out; > + } FWIW this is a change of behaviour; for some reason the code used to loop back to grab_cache_page_write_begin() and bail out on PageUptodate() I suppose; some sort of race check? The whole pattern is a bit weird to me and 9p has no guarantee on concurrent writes to a file with cache enabled (except that it will corrupt something), so this part is fine with me. What I'm curious about is the page used to be both unlocked and put, but now isn't either and the return value hasn't changed for the caller to make a difference on write_begin / I don't see any code change in the vfs to handle that. What did I miss? (FWIW at least cifs in the series has the same pattern change; didn't check all of them) Thanks, -- Dominique