From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with SMTP id 306DE6B01EE for ; Wed, 31 Mar 2010 01:30:26 -0400 (EDT) Received: from m4.gw.fujitsu.co.jp ([10.0.50.74]) by fgwmail6.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id o2V5UNHH012310 for (envelope-from kamezawa.hiroyu@jp.fujitsu.com); Wed, 31 Mar 2010 14:30:23 +0900 Received: from smail (m4 [127.0.0.1]) by outgoing.m4.gw.fujitsu.co.jp (Postfix) with ESMTP id 3F68845DE81 for ; Wed, 31 Mar 2010 14:30:22 +0900 (JST) Received: from s4.gw.fujitsu.co.jp (s4.gw.fujitsu.co.jp [10.0.50.94]) by m4.gw.fujitsu.co.jp (Postfix) with ESMTP id 5100A45DE85 for ; Wed, 31 Mar 2010 14:30:18 +0900 (JST) Received: from s4.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s4.gw.fujitsu.co.jp (Postfix) with ESMTP id 5440CE18012 for ; Wed, 31 Mar 2010 14:30:17 +0900 (JST) Received: from m107.s.css.fujitsu.com (m107.s.css.fujitsu.com [10.249.87.107]) by s4.gw.fujitsu.co.jp (Postfix) with ESMTP id 825401DB804D for ; Wed, 31 Mar 2010 14:30:13 +0900 (JST) Date: Wed, 31 Mar 2010 14:26:23 +0900 From: KAMEZAWA Hiroyuki Subject: Re: [PATCH 14/14] mm,migration: Allow the migration of PageSwapCache pages Message-Id: <20100331142623.62ac9175.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <1269940489-5776-15-git-send-email-mel@csn.ul.ie> References: <1269940489-5776-1-git-send-email-mel@csn.ul.ie> <1269940489-5776-15-git-send-email-mel@csn.ul.ie> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Mel Gorman Cc: Andrew Morton , Andrea Arcangeli , Christoph Lameter , Adam Litke , Avi Kivity , David Rientjes , Minchan Kim , KOSAKI Motohiro , Rik van Riel , linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: On Tue, 30 Mar 2010 10:14:49 +0100 Mel Gorman wrote: > PageAnon pages that are unmapped may or may not have an anon_vma so > are not currently migrated. However, a swap cache page can be migrated > and fits this description. This patch identifies page swap caches and > allows them to be migrated. > Some comments. > Signed-off-by: Mel Gorman > --- > mm/migrate.c | 15 ++++++++++----- > mm/rmap.c | 6 ++++-- > 2 files changed, 14 insertions(+), 7 deletions(-) > > diff --git a/mm/migrate.c b/mm/migrate.c > index 35aad2a..f9bf37e 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -203,6 +203,9 @@ static int migrate_page_move_mapping(struct address_space *mapping, > void **pslot; > > if (!mapping) { > + if (PageSwapCache(page)) > + SetPageSwapCache(newpage); > + Migration of SwapCache requires radix-tree replacement, IOW, mapping == NULL && PageSwapCache is BUG. So, this never happens. > /* Anonymous page without mapping */ > if (page_count(page) != 1) > return -EAGAIN; > @@ -607,11 +610,13 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private, > * the page was isolated and when we reached here while > * the RCU lock was not held > */ > - if (!page_mapped(page)) > - goto rcu_unlock; > - > - anon_vma = page_anon_vma(page); > - atomic_inc(&anon_vma->external_refcount); > + if (!page_mapped(page)) { > + if (!PageSwapCache(page)) > + goto rcu_unlock; > + } else { > + anon_vma = page_anon_vma(page); > + atomic_inc(&anon_vma->external_refcount); > + } > } > > /* > diff --git a/mm/rmap.c b/mm/rmap.c > index af35b75..d5ea1f2 100644 > --- a/mm/rmap.c > +++ b/mm/rmap.c > @@ -1394,9 +1394,11 @@ int rmap_walk(struct page *page, int (*rmap_one)(struct page *, > > if (unlikely(PageKsm(page))) > return rmap_walk_ksm(page, rmap_one, arg); > - else if (PageAnon(page)) > + else if (PageAnon(page)) { > + if (PageSwapCache(page)) > + return SWAP_AGAIN; > return rmap_walk_anon(page, rmap_one, arg); SwapCache has a condition as (PageSwapCache(page) && page_mapped(page) == true. Please see do_swap_page(), PageSwapCache bit is cleared only when do_swap_page()... swap_free(entry); if (vm_swap_full() || (vma->vm_flags & VM_LOCKED) || PageMlocked(page)) try_to_free_swap(page); Then, PageSwapCache is cleared only when swap is freeable even if mapped. rmap_walk_anon() should be called and the check is not necessary. Thanks, -Kame -- 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