From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752848Ab3BUI2V (ORCPT ); Thu, 21 Feb 2013 03:28:21 -0500 Received: from mail-pa0-f53.google.com ([209.85.220.53]:38378 "EHLO mail-pa0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752183Ab3BUI2U (ORCPT ); Thu, 21 Feb 2013 03:28:20 -0500 Date: Thu, 21 Feb 2013 00:27:39 -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 6/7] mm: cleanup "swapcache" in do_swap_page 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 I dislike the way in which "swapcache" gets used in do_swap_page(): there is always a page from swapcache there (even if maybe uncached by the time we lock it), but tests are made according to "swapcache". Rework that with "page != swapcache", as has been done in unuse_pte(). Signed-off-by: Hugh Dickins --- mm/memory.c | 18 ++++++++---------- 1 file changed, 8 insertions(+), 10 deletions(-) --- mmotm.orig/mm/memory.c 2013-02-20 22:43:47.228023344 -0800 +++ mmotm/mm/memory.c 2013-02-20 23:21:00.304076416 -0800 @@ -2954,7 +2954,7 @@ static int do_swap_page(struct mm_struct unsigned int flags, pte_t orig_pte) { spinlock_t *ptl; - struct page *page, *swapcache = NULL; + struct page *page, *swapcache; swp_entry_t entry; pte_t pte; int locked; @@ -3005,9 +3005,11 @@ static int do_swap_page(struct mm_struct */ ret = VM_FAULT_HWPOISON; delayacct_clear_flag(DELAYACCT_PF_SWAPIN); + swapcache = page; goto out_release; } + swapcache = page; locked = lock_page_or_retry(page, mm, flags); delayacct_clear_flag(DELAYACCT_PF_SWAPIN); @@ -3025,16 +3027,12 @@ static int do_swap_page(struct mm_struct if (unlikely(!PageSwapCache(page) || page_private(page) != entry.val)) goto out_page; - swapcache = page; page = ksm_might_need_to_copy(page, vma, address); if (unlikely(!page)) { ret = VM_FAULT_OOM; page = swapcache; - swapcache = NULL; goto out_page; } - if (page == swapcache) - swapcache = NULL; if (mem_cgroup_try_charge_swapin(mm, page, GFP_KERNEL, &ptr)) { ret = VM_FAULT_OOM; @@ -3078,10 +3076,10 @@ static int do_swap_page(struct mm_struct } flush_icache_page(vma, page); set_pte_at(mm, address, page_table, pte); - if (swapcache) /* ksm created a completely new copy */ - page_add_new_anon_rmap(page, vma, address); - else + if (page == swapcache) do_page_add_anon_rmap(page, vma, address, exclusive); + else /* ksm created a completely new copy */ + page_add_new_anon_rmap(page, vma, address); /* It's better to call commit-charge after rmap is established */ mem_cgroup_commit_charge_swapin(page, ptr); @@ -3089,7 +3087,7 @@ static int do_swap_page(struct mm_struct if (vm_swap_full() || (vma->vm_flags & VM_LOCKED) || PageMlocked(page)) try_to_free_swap(page); unlock_page(page); - if (swapcache) { + if (page != swapcache) { /* * Hold the lock to avoid the swap entry to be reused * until we take the PT lock for the pte_same() check @@ -3122,7 +3120,7 @@ out_page: unlock_page(page); out_release: page_cache_release(page); - if (swapcache) { + if (page != swapcache) { unlock_page(swapcache); page_cache_release(swapcache); }