From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752395Ab3BUI0W (ORCPT ); Thu, 21 Feb 2013 03:26:22 -0500 Received: from mail-pb0-f46.google.com ([209.85.160.46]:46415 "EHLO mail-pb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752047Ab3BUI0V (ORCPT ); Thu, 21 Feb 2013 03:26:21 -0500 Date: Thu, 21 Feb 2013 00:25:40 -0800 (PST) From: Hugh Dickins X-X-Sender: hugh@eggly.anvils To: Andrew Morton cc: Johannes Weiner , Mel Gorman , Petr Holasek , Andrea Arcangeli , Izik Eidus , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH 5/7] mm,ksm: swapoff might need to copy In-Reply-To: Message-ID: References: User-Agent: Alpine 2.00 (LNX 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Before establishing that KSM page migration was the cause of my WARN_ON_ONCE(page_mapped(page))s, I suspected that they came from the lack of a ksm_might_need_to_copy() in swapoff's unuse_pte() - which in many respects is equivalent to faulting in a page. In fact I've never caught that as the cause: but in theory it does at least need the KSM_RUN_UNMERGE check in ksm_might_need_to_copy(), to avoid bringing a KSM page back in when it's not supposed to be. I intended to copy how it's done in do_swap_page(), but have a strong aversion to how "swapcache" ends up being used there: rework it with "page != swapcache". Signed-off-by: Hugh Dickins --- mm/swapfile.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) --- mmotm.orig/mm/swapfile.c 2013-02-20 22:28:09.076001048 -0800 +++ mmotm/mm/swapfile.c 2013-02-20 23:20:50.872076192 -0800 @@ -874,11 +874,17 @@ unsigned int count_swap_pages(int type, static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd, unsigned long addr, swp_entry_t entry, struct page *page) { + struct page *swapcache; struct mem_cgroup *memcg; spinlock_t *ptl; pte_t *pte; int ret = 1; + swapcache = page; + page = ksm_might_need_to_copy(page, vma, addr); + if (unlikely(!page)) + return -ENOMEM; + if (mem_cgroup_try_charge_swapin(vma->vm_mm, page, GFP_KERNEL, &memcg)) { ret = -ENOMEM; @@ -897,7 +903,10 @@ static int unuse_pte(struct vm_area_stru get_page(page); set_pte_at(vma->vm_mm, addr, pte, pte_mkold(mk_pte(page, vma->vm_page_prot))); - page_add_anon_rmap(page, vma, addr); + if (page == swapcache) + page_add_anon_rmap(page, vma, addr); + else /* ksm created a completely new copy */ + page_add_new_anon_rmap(page, vma, addr); mem_cgroup_commit_charge_swapin(page, memcg); swap_free(entry); /* @@ -908,6 +917,10 @@ static int unuse_pte(struct vm_area_stru out: pte_unmap_unlock(pte, ptl); out_nolock: + if (page != swapcache) { + unlock_page(page); + put_page(page); + } return ret; }