linux-kernel - Re: [PATCH 1/4] fs: fix data invalidation in the cleancache during direct IO

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Message-Id: <20170418154647.9583bfa06705c614a2640a15@linux-foundation.org>
Date:   Tue, 18 Apr 2017 15:46:47 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Andrey Ryabinin <aryabinin@...tuozzo.com>
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        <linux-fsdevel@...r.kernel.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Eric Van Hensbergen <ericvh@...il.com>,
        Ron Minnich <rminnich@...dia.gov>,
        Latchesar Ionkov <lucho@...kov.net>,
        Steve French <sfrench@...ba.org>,
        Matthew Wilcox <mawilcox@...rosoft.com>,
        Ross Zwisler <ross.zwisler@...ux.intel.com>,
        Trond Myklebust <trond.myklebust@...marydata.com>,
        Anna Schumaker <anna.schumaker@...app.com>,
        Jan Kara <jack@...e.cz>, Jens Axboe <axboe@...nel.dk>,
        Johannes Weiner <hannes@...xchg.org>,
        Alexey Kuznetsov <kuznet@...tuozzo.com>,
        Christoph Hellwig <hch@....de>,
        <v9fs-developer@...ts.sourceforge.net>,
        <linux-kernel@...r.kernel.org>, <linux-cifs@...r.kernel.org>,
        <samba-technical@...ts.samba.org>, <linux-nfs@...r.kernel.org>,
        <linux-mm@...ck.org>
Subject: Re: [PATCH 1/4] fs: fix data invalidation in the cleancache during
 direct IO

On Fri, 14 Apr 2017 17:07:50 +0300 Andrey Ryabinin <aryabinin@...tuozzo.com> wrote:

> Some direct write fs hooks call invalidate_inode_pages2[_range]()
> conditionally iff mapping->nrpages is not zero. If page cache is empty,
> buffered read following after direct IO write would get stale data from
> the cleancache.
> 
> Also it doesn't feel right to check only for ->nrpages because
> invalidate_inode_pages2[_range] invalidates exceptional entries as well.
> 
> Fix this by calling invalidate_inode_pages2[_range]() regardless of nrpages
> state.

I'm not understanding this.  I can buy the argument about
nrexceptional, but why does cleancache require the
invalidate_inode_pages2_range) call even when ->nrpages is zero?

I *assume* it's because invalidate_inode_pages2_range() calls
cleancache_invalidate_inode(), yes?  If so, can we please add this to
the changelog?  If not then please explain further.