From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <SRS0=Gsg2=76=lists.ozlabs.org=linux-erofs-bounces+linux-erofs=archiver.kernel.org@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=-0.5 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED,
	HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,
	URIBL_BLOCKED autolearn=no 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 31A81C433DF
	for <linux-erofs@archiver.kernel.org>; Wed, 17 Jun 2020 02:22:36 +0000 (UTC)
Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2])
	(using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits))
	(No client certificate requested)
	by mail.kernel.org (Postfix) with ESMTPS id D36CC20882
	for <linux-erofs@archiver.kernel.org>; Wed, 17 Jun 2020 02:22:35 +0000 (UTC)
Authentication-Results: mail.kernel.org;
	dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="Pw7h6Zur"
DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D36CC20882
Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org
Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linux-erofs-bounces+linux-erofs=archiver.kernel.org@lists.ozlabs.org
Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3])
	by lists.ozlabs.org (Postfix) with ESMTP id 49mpkL0ZbXzDqwm
	for <linux-erofs@archiver.kernel.org>; Wed, 17 Jun 2020 12:22:34 +1000 (AEST)
Authentication-Results: lists.ozlabs.org;
 spf=none (no SPF record) smtp.mailfrom=infradead.org
 (client-ip=2607:7c80:54:e::133; helo=bombadil.infradead.org;
 envelope-from=willy@infradead.org; receiver=<UNKNOWN>)
Authentication-Results: lists.ozlabs.org;
 dmarc=none (p=none dis=none) header.from=infradead.org
Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key;
 unprotected) header.d=infradead.org header.i=@infradead.org
 header.a=rsa-sha256 header.s=bombadil.20170209 header.b=Pw7h6Zur; 
 dkim-atps=neutral
Received: from bombadil.infradead.org (bombadil.infradead.org
 [IPv6:2607:7c80:54:e::133])
 (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)
 key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256)
 (No client certificate requested)
 by lists.ozlabs.org (Postfix) with ESMTPS id 49mpkC6QgbzDqmC
 for <linux-erofs@lists.ozlabs.org>; Wed, 17 Jun 2020 12:22:27 +1000 (AEST)
DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed;
 d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Transfer-Encoding
 :Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:
 Sender:Reply-To:Content-ID:Content-Description;
 bh=BEusnUbR+/cmrBB9bk/xdvHCANKyUH/aAcSZAMuW5OE=; b=Pw7h6Zurn3kEfvE1eYLcuqezpS
 6dv6YNzk6+f6NL9T5b1t5Q3S1oT5qqAMDEOxHE+1wGzAU1/UvkbHdNz07Ga1WaCWGzhKUCRSeZ6QZ
 o0I5/jAy2zGLAu1G4S3MZdS3qCqGws/6WiA4NRqQjbA9SmyY+Nnm0QKGoSQJFNIHsS2xUI0I9Udce
 qOHpLfYIPOR526dlzyvkD4gq0Xo6OO+YQA5h+uvfTaDDzfQbzfntE6t8KKL/bdGZugpf9j96kxyXi
 uqj9bm92o25yQodA2+9jXT7MN6tTeGOpuEujbqml8NcV0guvi1GGbOd5RpsedFvm4bLu4W95FUUfR
 YKCs+4uQ==;
Received: from willy by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red
 Hat Linux)) id 1jlNi9-0002wT-UP; Wed, 17 Jun 2020 02:21:57 +0000
Date: Tue, 16 Jun 2020 19:21:57 -0700
From: Matthew Wilcox <willy@infradead.org>
To: Andreas =?iso-8859-1?Q?Gr=FCnbacher?= <andreas.gruenbacher@gmail.com>
Subject: Re: [Cluster-devel] [PATCH v11 16/25] fs: Convert mpage_readpages to
 mpage_readahead
Message-ID: <20200617022157.GF8681@bombadil.infradead.org>
References: <20200414150233.24495-1-willy@infradead.org>
 <20200414150233.24495-17-willy@infradead.org>
 <CAHc6FU4m1M7Tv4scX0UxSiVBqkL=Vcw_z-R7SufL8k7Bw=qPOw@mail.gmail.com>
 <20200617003216.GC8681@bombadil.infradead.org>
 <CAHpGcMK6Yu0p-FO8CciiySqh+qcWLG-t3hEaUg-rqJnS=2uhqg@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <CAHpGcMK6Yu0p-FO8CciiySqh+qcWLG-t3hEaUg-rqJnS=2uhqg@mail.gmail.com>
X-BeenThere: linux-erofs@lists.ozlabs.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Development of Linux EROFS file system <linux-erofs.lists.ozlabs.org>
List-Unsubscribe: <https://lists.ozlabs.org/options/linux-erofs>,
 <mailto:linux-erofs-request@lists.ozlabs.org?subject=unsubscribe>
List-Archive: <http://lists.ozlabs.org/pipermail/linux-erofs/>
List-Post: <mailto:linux-erofs@lists.ozlabs.org>
List-Help: <mailto:linux-erofs-request@lists.ozlabs.org?subject=help>
List-Subscribe: <https://lists.ozlabs.org/listinfo/linux-erofs>,
 <mailto:linux-erofs-request@lists.ozlabs.org?subject=subscribe>
Cc: cluster-devel <cluster-devel@redhat.com>,
 linux-ext4 <linux-ext4@vger.kernel.org>,
 Andreas Gruenbacher <agruenba@redhat.com>,
 Joseph Qi <joseph.qi@linux.alibaba.com>, John Hubbard <jhubbard@nvidia.com>,
 Steven Whitehouse <swhiteho@redhat.com>, LKML <linux-kernel@vger.kernel.org>,
 Junxiao Bi <junxiao.bi@oracle.com>, linux-xfs <linux-xfs@vger.kernel.org>,
 William Kucharski <william.kucharski@oracle.com>,
 Christoph Hellwig <hch@lst.de>, linux-btrfs@vger.kernel.org,
 linux-fsdevel <linux-fsdevel@vger.kernel.org>,
 Andrew Morton <akpm@linux-foundation.org>,
 linux-f2fs-devel@lists.sourceforge.net, linux-erofs@lists.ozlabs.org,
 Linux-MM <linux-mm@kvack.org>, ocfs2-devel@oss.oracle.com,
 Bob Peterson <rpeterso@redhat.com>
Errors-To: linux-erofs-bounces+linux-erofs=archiver.kernel.org@lists.ozlabs.org
Sender: "Linux-erofs"
 <linux-erofs-bounces+linux-erofs=archiver.kernel.org@lists.ozlabs.org>

On Wed, Jun 17, 2020 at 02:57:14AM +0200, Andreas Grünbacher wrote:
> Am Mi., 17. Juni 2020 um 02:33 Uhr schrieb Matthew Wilcox <willy@infradead.org>:
> >
> > On Wed, Jun 17, 2020 at 12:36:13AM +0200, Andreas Gruenbacher wrote:
> > > Am Mi., 15. Apr. 2020 um 23:39 Uhr schrieb Matthew Wilcox <willy@infradead.org>:
> > > > From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
> > > >
> > > > Implement the new readahead aop and convert all callers (block_dev,
> > > > exfat, ext2, fat, gfs2, hpfs, isofs, jfs, nilfs2, ocfs2, omfs, qnx6,
> > > > reiserfs & udf).  The callers are all trivial except for GFS2 & OCFS2.
> > >
> > > This patch leads to an ABBA deadlock in xfstest generic/095 on gfs2.
> > >
> > > Our lock hierarchy is such that the inode cluster lock ("inode glock")
> > > for an inode needs to be taken before any page locks in that inode's
> > > address space.
> >
> > How does that work for ...
> >
> > writepage:              yes, unlocks (see below)
> > readpage:               yes, unlocks
> > invalidatepage:         yes
> > releasepage:            yes
> > freepage:               yes
> > isolate_page:           yes
> > migratepage:            yes (both)
> > putback_page:           yes
> > launder_page:           yes
> > is_partially_uptodate:  yes
> > error_remove_page:      yes
> >
> > Is there a reason that you don't take the glock in the higher level
> > ops which are called before readhead gets called?  I'm looking at XFS,
> > and it takes the xfs_ilock SHARED in xfs_file_buffered_aio_read()
> > (called from xfs_file_read_iter).
> 
> Right, the approach from the following thread might fix this:
> 
> https://lore.kernel.org/linux-fsdevel/20191122235324.17245-1-agruenba@redhat.com/T/#t

In general, I think this is a sound approach.

Specifically, I think FAULT_FLAG_CACHED can go away.  map_pages()
will bring in the pages which are in the page cache, so when we get to
gfs2_fault(), we know there's a reason to acquire the glock.