From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@kernel.org>
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=-8.8 required=3.0 tests=BAYES_00,
	HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,
	SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 99BBFC433E1
	for <linux-kernel@archiver.kernel.org>; Tue, 30 Mar 2021 18:39:34 +0000 (UTC)
Received: from vger.kernel.org (vger.kernel.org [23.128.96.18])
	by mail.kernel.org (Postfix) with ESMTP id 45B9861968
	for <linux-kernel@archiver.kernel.org>; Tue, 30 Mar 2021 18:39:34 +0000 (UTC)
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S232862AbhC3SjU (ORCPT <rfc822;linux-kernel@archiver.kernel.org>);
        Tue, 30 Mar 2021 14:39:20 -0400
Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43500 "EHLO
        lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S232785AbhC3Sit (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Tue, 30 Mar 2021 14:38:49 -0400
Received: from zeniv-ca.linux.org.uk (zeniv-ca.linux.org.uk [IPv6:2607:5300:60:148a::1])
        by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7B2FBC061574
        for <linux-kernel@vger.kernel.org>; Tue, 30 Mar 2021 11:38:49 -0700 (PDT)
Received: from viro by zeniv-ca.linux.org.uk with local (Exim 4.94 #2 (Red Hat Linux))
        id 1lRJG8-00162v-S7; Tue, 30 Mar 2021 18:38:36 +0000
Date:   Tue, 30 Mar 2021 18:38:36 +0000
From:   Al Viro <viro@zeniv.linux.org.uk>
To:     Christoph Hellwig <hch@lst.de>
Cc:     Joel Stanley <joel@jms.id.au>,
        David Woodhouse <dwmw2@infradead.org>,
        Richard Weinberger <richard@nod.at>,
        Kees Cook <keescook@chromium.org>,
        "William A . Kennington III" <wak@google.com>,
        Lei YU <mine260309@gmail.com>, linux-mtd@lists.infradead.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] jffs2: Hook up splice_write callback
Message-ID: <YGNwLM7c1qvRye2c@zeniv-ca.linux.org.uk>
References: <20210330134537.423447-1-joel@jms.id.au>
 <20210330161715.GA12783@lst.de>
 <YGNuZMUkzH0tkce6@zeniv-ca.linux.org.uk>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <YGNuZMUkzH0tkce6@zeniv-ca.linux.org.uk>
Sender: Al Viro <viro@ftp.linux.org.uk>
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Tue, Mar 30, 2021 at 06:31:00PM +0000, Al Viro wrote:
> On Tue, Mar 30, 2021 at 06:17:15PM +0200, Christoph Hellwig wrote:
> > On Wed, Mar 31, 2021 at 12:15:37AM +1030, Joel Stanley wrote:
> > > overlayfs using jffs2 as the upper filesystem would fail in some cases
> > > since moving to v5.10. The test case used was to run 'touch' on a file
> > > that exists in the lower fs, causing the modification time to be
> > > updated. It returns EINVAL when the bug is triggered.
> > > 
> > > A bisection showed this was introduced in v5.9-rc1, with commit
> > > 36e2c7421f02 ("fs: don't allow splice read/write without explicit ops").
> > > Reverting that commit restores the expected behaviour.
> > > 
> > > Some digging showed that this was due to jffs2 lacking an implementation
> > > of splice_write. (For unknown reasons the warn_unsupported that should
> > > trigger was not displaying any output).
> > > 
> > > Adding this patch resolved the issue and the test now passes.
> > 
> > Looks good:
> > 
> > Reviewed-by: Christoph Hellwig <hch@lst.de>
> 
> The same goes for quite a few other filesystems, actually - at least
> adfs, affs, bfs, hfs, hfsplus, hostfs, hpfs, minix, omfs, sysv, ufs 
> and vboxsf are in the same boat, and I suspect that ecryptfs and ntfs
> might be too.
> 
> Christoph, do you see any problems with doing the same thing for that
> bunch as well?

coda and udf as well, by the look of it...