Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757582Ab3ENN6y (ORCPT ); Tue, 14 May 2013 09:58:54 -0400 Received: from kanga.kvack.org ([205.233.56.17]:39957 "EHLO kanga.kvack.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753439Ab3ENN6x (ORCPT ); Tue, 14 May 2013 09:58:53 -0400 Date: Tue, 14 May 2013 09:58:50 -0400 From: Benjamin LaHaise To: Tang Chen Cc: Jeff Moyer , Mel Gorman , Minchan Kim , Lin Feng , akpm@linux-foundation.org, viro@zeniv.linux.org.uk, khlebnikov@openvz.org, walken@google.com, kamezawa.hiroyu@jp.fujitsu.com, riel@redhat.com, rientjes@google.com, isimatu.yasuaki@jp.fujitsu.com, wency@cn.fujitsu.com, laijs@cn.fujitsu.com, jiang.liu@huawei.com, zab@redhat.com, linux-mm@kvack.org, linux-aio@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Marek Szyprowski Subject: Re: [PATCH V2 1/2] mm: hotplug: implement non-movable version of get_user_pages() called get_user_pages_non_movable() Message-ID: <20130514135850.GG13845@kvack.org> References: <1360056113-14294-2-git-send-email-linfeng@cn.fujitsu.com> <20130205120137.GG21389@suse.de> <20130206004234.GD11197@blaptop> <20130206095617.GN21389@suse.de> <5190AE4F.4000103@cn.fujitsu.com> <20130513091902.GP11497@suse.de> <20130513143757.GP31899@kvack.org> <20130513150147.GQ31899@kvack.org> <5191926A.2090608@cn.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5191926A.2090608@cn.fujitsu.com> User-Agent: Mutt/1.4.2.2i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1892 Lines: 50 On Tue, May 14, 2013 at 09:24:58AM +0800, Tang Chen wrote: > Hi Mel, Benjamin, Jeff, > > On 05/13/2013 11:01 PM, Benjamin LaHaise wrote: > >On Mon, May 13, 2013 at 10:54:03AM -0400, Jeff Moyer wrote: > >>How do you propose to move the ring pages? > > > >It's the same problem as doing a TLB shootdown: flush the old pages from > >userspace's mapping, copy any existing data to the new pages, then > >repopulate the page tables. It will likely require the addition of > >address_space_operations for the mapping, but that's not too hard to do. > > > > I think we add migrate_unpin() callback to decrease page->count if > necessary, > and migrate the page to a new page, and add migrate_pin() callback to pin > the new page again. You can't just decrease the page count for this to work. The pages are pinned because aio_complete() can occur at any time and needs to have a place to write the completion events. When changing pages, aio has to take the appropriate lock when changing one page for another. > The migrate procedure will work just as before. We use callbacks to > decrease > the page->count before migration starts, and increase it when the migration > is done. > > And migrate_pin() and migrate_unpin() callbacks will be added to > struct address_space_operations. I think the existing migratepage operation in address_space_operations can be used. Does it get called when hot unplug occurs? That is: is testing with the migrate_pages syscall similar enough to the memory removal case? -ben > Is that right ? > > If so, I'll be working on it. > > Thanks. :) -- "Thought is the essence of where you are now." -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/