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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_MUTT 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 C7B19C48BD6 for ; Wed, 26 Jun 2019 06:17:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AC26D2085A for ; Wed, 26 Jun 2019 06:17:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726723AbfFZGRa (ORCPT ); Wed, 26 Jun 2019 02:17:30 -0400 Received: from verein.lst.de ([213.95.11.211]:40423 "EHLO newverein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725379AbfFZGRa (ORCPT ); Wed, 26 Jun 2019 02:17:30 -0400 Received: by newverein.lst.de (Postfix, from userid 2407) id BD02868B05; Wed, 26 Jun 2019 08:16:58 +0200 (CEST) Date: Wed, 26 Jun 2019 08:16:58 +0200 From: Christoph Hellwig To: Goldwyn Rodrigues Cc: Christoph Hellwig , linux-btrfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, darrick.wong@oracle.com, david@fromorbit.com Subject: Re: [PATCH 3/6] iomap: Check iblocksize before transforming page->private Message-ID: <20190626061658.GA23972@lst.de> References: <20190621192828.28900-1-rgoldwyn@suse.de> <20190621192828.28900-4-rgoldwyn@suse.de> <20190624070536.GA3675@lst.de> <20190625185659.tqaikm27onz6g3jt@fiona> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190625185659.tqaikm27onz6g3jt@fiona> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Tue, Jun 25, 2019 at 01:56:59PM -0500, Goldwyn Rodrigues wrote: > Btrfs uses page->private to identify which extent_buffer it belongs to. > So, if you read, it fills the page->private. Then you try to write to > it, iomap will assume it to be iomap_page pointer. Yes, and that is going to run into problems sooner or later, that is if you want to support sub-page size block sizes in btrfs, which I though is work in progress, or if you ever want to write through iomap. > I don't think we can move extent_buffer out of page->private for btrfs. > Any other ideas? I think you'll have to. That being said I don't see why you'd need data in page->private for pages potentially being read in a setup where blocksize == PAGESIZE anyway.