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x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=gmail.com header.result=pass header_is_org_domain=yes Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750877AbeBHLW5 (ORCPT ); Thu, 8 Feb 2018 06:22:57 -0500 Received: from mail-pf0-f196.google.com ([209.85.192.196]:37904 "EHLO mail-pf0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750806AbeBHLW4 (ORCPT ); Thu, 8 Feb 2018 06:22:56 -0500 X-Google-Smtp-Source: AH8x226IPqh4X94nS4HfsveYUMm8drLhrIkwuaBEINpwkEHzjf4o++PxFx8GX75UWSnsH5p5hwbckg== Date: Thu, 8 Feb 2018 20:22:51 +0900 From: Sergey Senozhatsky To: Minchan Kim Cc: Sergey Senozhatsky , Andrew Morton , "Huang, Ying" , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Huang Ying , Konrad Rzeszutek Wilk , Dan Streetman , Seth Jennings , Tetsuo Handa , Shaohua Li , Michal Hocko , Johannes Weiner , Mel Gorman , Shakeel Butt , stable@vger.kernel.org, Sergey Senozhatsky Subject: Re: [PATCH -mm -v2] mm, swap, frontswap: Fix THP swap if frontswap enabled Message-ID: <20180208112251.GA710@jagdpanzerIV> References: <20180207070035.30302-1-ying.huang@intel.com> <20180207130534.259cd71a595c6275b2da38d3@linux-foundation.org> <20180208013635.GA596@jagdpanzerIV> <20180208102521.GB74192@eng-minchan1.roam.corp.google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180208102521.GB74192@eng-minchan1.roam.corp.google.com> User-Agent: Mutt/1.9.3 (2018-01-21) Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On (02/08/18 02:25), Minchan Kim wrote: [..] > > > if (PageTransHuge(page)) { > > > - if (IS_ENABLED(CONFIG_THP_SWAP)) > > > - get_swap_pages(1, true, &entry); > > > + /* Frontswap doesn't support THP */ > > > + if (!frontswap_enabled()) { > > > + if (IS_ENABLED(CONFIG_THP_SWAP)) > > > + get_swap_pages(1, true, &entry); > > > + } > > > return entry; > > > } > > > > I have proposed exactly the same thing [1], Minchan commented that > > it would introduce frontswap dependency to swap_slots.c [2]. Which > > is true, but I'd still probably prefer to handle it all in > > get_swap_page. Minchan, any objections? > > I didn't want to spread out frontswap stuff unless it has good value > because most of frontswap functions are located in mm/swapfile.c > at this moment. Sure, your points are perfectly valid. At the same time it might be the case that we already kind of expose that THP dependency thing to vmscan. The whole if (!add_to_swap()) { if (!PageTransHuge(page)) goto activate_locked; split_huge_page_to_list(page); add_to_swap(page); } looks a bit suspicious - if add_to_swap() fails and the page is THP then split it and add_to_swap() again. -ss