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From: Vasily Averin <vvs@virtuozzo.com>
To: Andrew Morton <akpm@linux-foundation.org>,
	Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>,
	Konstantin Khorenko <khorenko@virtuozzo.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Mel Gorman <mgorman@techsingularity.net>, Jan Kara <jack@suse.cz>,
	Matthew Wilcox <willy@infradead.org>,
	Andi Kleen <ak@linux.intel.com>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm: cleancache: fix corruption on missed inode invalidation
Date: Fri, 16 Nov 2018 10:55:45 +0300	[thread overview]
Message-ID: <d2a7e3fe-67ca-12f3-d16b-c9de0646c063@virtuozzo.com> (raw)
In-Reply-To: <20181115143103.c6fa8fec343bb706b91f6c6c@linux-foundation.org>

On 11/16/18 1:31 AM, Andrew Morton wrote:
> On Mon, 12 Nov 2018 12:57:34 +0300 Pavel Tikhomirov <ptikhomirov@virtuozzo.com> wrote:
> 
>> If all pages are deleted from the mapping by memory reclaim and also
>> moved to the cleancache:
>>
>> __delete_from_page_cache
>>   (no shadow case)
>>   unaccount_page_cache_page
>>     cleancache_put_page
>>   page_cache_delete
>>     mapping->nrpages -= nr
>>     (nrpages becomes 0)
>>
>> We don't clean the cleancache for an inode after final file truncation
>> (removal).
>>
>> truncate_inode_pages_final
>>   check (nrpages || nrexceptional) is false
>>     no truncate_inode_pages
>>       no cleancache_invalidate_inode(mapping)
>>
>> These way when reading the new file created with same inode we may get
>> these trash leftover pages from cleancache and see wrong data instead of
>> the contents of the new file.
>>
>> Fix it by always doing truncate_inode_pages which is already ready for
>> nrpages == 0 && nrexceptional == 0 case and just invalidates inode.
>>
> 
> Data corruption sounds serious.  Shouldn't we backport this into
> -stable kernels?

Yes, it was broken in 4.14 kernel and it should affect all who uses cleancache
Fixes: commit 91b0abe36a7b ("mm + fs: store shadow entries in page cache")

      reply	other threads:[~2018-11-16  7:55 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-12  9:57 [PATCH] mm: cleancache: fix corruption on missed inode invalidation Pavel Tikhomirov
2018-11-12 11:31 ` Jan Kara
2018-11-12 11:40   ` Andrey Ryabinin
2018-11-12 11:54     ` Jan Kara
2018-11-12 12:00   ` [PATCH v2] " Pavel Tikhomirov
2018-11-15 22:29   ` [PATCH] " Andrew Morton
2018-11-15 22:31 ` Andrew Morton
2018-11-16  7:55   ` Vasily Averin [this message]

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