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=-11.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 0738EC00A89 for ; Mon, 2 Nov 2020 17:30:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9C86721D91 for ; Mon, 2 Nov 2020 17:30:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727524AbgKBRaz (ORCPT ); Mon, 2 Nov 2020 12:30:55 -0500 Received: from mx2.suse.de ([195.135.220.15]:52116 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726587AbgKBRaz (ORCPT ); Mon, 2 Nov 2020 12:30:55 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 5F8ACAC2E; Mon, 2 Nov 2020 17:30:53 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id DE7541E12FB; Mon, 2 Nov 2020 18:30:52 +0100 (CET) Date: Mon, 2 Nov 2020 18:30:52 +0100 From: Jan Kara To: Chengguang Xu Cc: miklos@szeredi.hu, amir73il@gmail.com, jack@suse.cz, linux-unionfs@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [RFC PATCH v2 5/8] ovl: mark overlayfs' inode dirty on shared writable mmap Message-ID: <20201102173052.GF23988@quack2.suse.cz> References: <20201025034117.4918-1-cgxu519@mykernel.net> <20201025034117.4918-6-cgxu519@mykernel.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201025034117.4918-6-cgxu519@mykernel.net> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-unionfs@vger.kernel.org On Sun 25-10-20 11:41:14, Chengguang Xu wrote: > Overlayfs cannot be notified when mmapped area gets dirty, > so we need to proactively mark inode dirty in ->mmap operation. > > Signed-off-by: Chengguang Xu > --- > fs/overlayfs/file.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c > index efccb7c1f9bc..cd6fcdfd81a9 100644 > --- a/fs/overlayfs/file.c > +++ b/fs/overlayfs/file.c > @@ -486,6 +486,10 @@ static int ovl_mmap(struct file *file, struct vm_area_struct *vma) > /* Drop reference count from new vm_file value */ > fput(realfile); > } else { > + if (vma->vm_flags & (VM_SHARED|VM_MAYSHARE) && > + vma->vm_flags & (VM_WRITE|VM_MAYWRITE)) > + ovl_mark_inode_dirty(file_inode(file)); > + But does this work reliably? I mean once writeback runs, your inode (as well as upper inode) is cleaned. Then a page fault comes so file has dirty pages again and would need flushing but overlayfs inode stays clean? Am I missing something? Honza -- Jan Kara SUSE Labs, CR