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

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Message-ID: <64a3f71f-11af-2ab3-c2b5-8e26e03b0ceb@virtuozzo.com>
Date:   Wed, 19 Apr 2017 18:15:43 +0300
From:   Andrey Ryabinin <aryabinin@...tuozzo.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
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>,
        <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 04/19/2017 01:46 AM, Andrew Morton wrote:
> 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.
> 

Yes, your assumption is correct. I'll fix the changelog.