Date: Tue, 18 Apr 2017 15:46:47 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>,
        <linux-fsdevel@vger.kernel.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        Eric Van Hensbergen <ericvh@gmail.com>,
        Ron Minnich <rminnich@sandia.gov>,
        Latchesar Ionkov <lucho@ionkov.net>,
        Steve French <sfrench@samba.org>,
        Matthew Wilcox <mawilcox@microsoft.com>,
        Ross Zwisler <ross.zwisler@linux.intel.com>,
        Trond Myklebust <trond.myklebust@primarydata.com>,
        Anna Schumaker <anna.schumaker@netapp.com>,
        Jan Kara <jack@suse.cz>, Jens Axboe <axboe@kernel.dk>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Alexey Kuznetsov <kuznet@virtuozzo.com>,
        Christoph Hellwig <hch@lst.de>,
        <v9fs-developer@lists.sourceforge.net>,
        <linux-kernel@vger.kernel.org>, <linux-cifs@vger.kernel.org>,
        <samba-technical@lists.samba.org>, <linux-nfs@vger.kernel.org>,
        <linux-mm@kvack.org>
Subject: Re: [PATCH 1/4] fs: fix data invalidation in the cleancache during
 direct IO
Message-Id: <20170418154647.9583bfa06705c614a2640a15@linux-foundation.org>
In-Reply-To: <20170414140753.16108-2-aryabinin@virtuozzo.com>
References: <20170414140753.16108-1-aryabinin@virtuozzo.com>
        <20170414140753.16108-2-aryabinin@virtuozzo.com>
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Sender: linux-nfs-owner@vger.kernel.org

On Fri, 14 Apr 2017 17:07:50 +0300 Andrey Ryabinin <aryabinin@virtuozzo.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.