From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ig0-f178.google.com (mail-ig0-f178.google.com [209.85.213.178]) by kanga.kvack.org (Postfix) with ESMTP id 470D46B006E for ; Tue, 18 Nov 2014 16:41:13 -0500 (EST) Received: by mail-ig0-f178.google.com with SMTP id hl2so5024688igb.17 for ; Tue, 18 Nov 2014 13:41:13 -0800 (PST) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTPS id i11si23000icc.36.2014.11.18.13.41.11 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 18 Nov 2014 13:41:12 -0800 (PST) Date: Tue, 18 Nov 2014 13:41:10 -0800 From: Andrew Morton Subject: Re: [PATCH] mm: frontswap: invalidate expired data on a dup-store failure Message-Id: <20141118134110.d5e17eec0ff90ff8c957fffd@linux-foundation.org> In-Reply-To: <000001d0030d$0505aaa0$0f10ffe0$%yang@samsung.com> References: <000001d0030d$0505aaa0$0f10ffe0$%yang@samsung.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Weijie Yang Cc: konrad.wilk@oracle.com, 'Seth Jennings' , 'Dan Streetman' , 'Minchan Kim' , 'Bob Liu' , xfishcoder@gmail.com, 'Weijie Yang' , linux-mm@kvack.org, linux-kernel@vger.kernel.org On Tue, 18 Nov 2014 16:51:36 +0800 Weijie Yang wrote: > If a frontswap dup-store failed, it should invalidate the expired page > in the backend, or it could trigger some data corruption issue. > Such as: > 1. use zswap as the frontswap backend with writeback feature > 2. store a swap page(version_1) to entry A, success > 3. dup-store a newer page(version_2) to the same entry A, fail > 4. use __swap_writepage() write version_2 page to swapfile, success > 5. zswap do shrink, writeback version_1 page to swapfile > 6. version_2 page is overwrited by version_1, data corrupt. > > This patch fixes this issue by invalidating expired data immediately > when meet a dup-store failure. > > ... > > --- a/mm/frontswap.c > +++ b/mm/frontswap.c > @@ -244,8 +244,10 @@ int __frontswap_store(struct page *page) > the (older) page from frontswap > */ > inc_frontswap_failed_stores(); > - if (dup) > + if (dup) { > __frontswap_clear(sis, offset); > + frontswap_ops->invalidate_page(type, offset); > + } > } > if (frontswap_writethrough_enabled) > /* report failure so swap also writes to swap device */ I tagged this for backporting into -stable kernels. Please shout at me if you think that was inappropriate. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org