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=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 CDE64C4742C for ; Mon, 2 Nov 2020 17:17:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8E0FC21D91 for ; Mon, 2 Nov 2020 17:17:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727672AbgKBRRo (ORCPT ); Mon, 2 Nov 2020 12:17:44 -0500 Received: from mx2.suse.de ([195.135.220.15]:36778 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727484AbgKBRRn (ORCPT ); Mon, 2 Nov 2020 12:17:43 -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 0AD00B2AF; Mon, 2 Nov 2020 17:17:42 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id 40B2A1E12FB; Mon, 2 Nov 2020 18:17:41 +0100 (CET) Date: Mon, 2 Nov 2020 18:17:41 +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 2/8] ovl: implement ->writepages operation Message-ID: <20201102171741.GE23988@quack2.suse.cz> References: <20201025034117.4918-1-cgxu519@mykernel.net> <20201025034117.4918-3-cgxu519@mykernel.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201025034117.4918-3-cgxu519@mykernel.net> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Archived-At: List-Archive: List-Post: On Sun 25-10-20 11:41:11, Chengguang Xu wrote: > Implement overlayfs' ->writepages operation so that > we can sync dirty data/metadata to upper filesystem. > > Signed-off-by: Chengguang Xu > --- > fs/overlayfs/inode.c | 26 ++++++++++++++++++++++++++ > 1 file changed, 26 insertions(+) > > diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c > index b584dca845ba..f27fc5be34df 100644 > --- a/fs/overlayfs/inode.c > +++ b/fs/overlayfs/inode.c > @@ -11,6 +11,7 @@ > #include > #include > #include > +#include > #include "overlayfs.h" > > > @@ -516,7 +517,32 @@ static const struct inode_operations ovl_special_inode_operations = { > .update_time = ovl_update_time, > }; > > +static int ovl_writepages(struct address_space *mapping, > + struct writeback_control *wbc) > +{ > + struct inode *upper_inode = ovl_inode_upper(mapping->host); > + struct ovl_fs *ofs = mapping->host->i_sb->s_fs_info; > + struct writeback_control tmp_wbc = *wbc; > + > + if (!ovl_should_sync(ofs)) > + return 0; > + > + /* > + * for sync(2) writeback, it has a separate external IO > + * completion path by checking PAGECACHE_TAG_WRITEBACK > + * in pagecache, we have to set for_sync to 0 in thie case, > + * let writeback waits completion after syncing individual > + * dirty inode, because we haven't implemented overlayfs' > + * own pagecache yet. > + */ > + if (wbc->for_sync && (wbc->sync_mode == WB_SYNC_ALL)) > + tmp_wbc.for_sync = 0; This looks really hacky as it closely depends on the internal details of writeback implementation. I'd be more open to say export wait_sb_inodes() for overlayfs use... Because that's what I gather you need in your overlayfs ->syncfs() implementation. Honza > + > + return sync_inode(upper_inode, &tmp_wbc); > +} > + > static const struct address_space_operations ovl_aops = { > + .writepages = ovl_writepages, > /* For O_DIRECT dentry_open() checks f_mapping->a_ops->direct_IO */ > .direct_IO = noop_direct_IO, > }; > -- > 2.26.2 > > -- Jan Kara SUSE Labs, CR