From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx146.postini.com [74.125.245.146]) by kanga.kvack.org (Postfix) with SMTP id ADDA26B0026 for ; Thu, 21 Feb 2013 03:28:20 -0500 (EST) Received: by mail-da0-f48.google.com with SMTP id w4so491931dam.7 for ; Thu, 21 Feb 2013 00:28:19 -0800 (PST) Date: Thu, 21 Feb 2013 00:27:39 -0800 (PST) From: Hugh Dickins Subject: [PATCH 6/7] mm: cleanup "swapcache" in do_swap_page In-Reply-To: Message-ID: References: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Johannes Weiner , Mel Gorman , Petr Holasek , Andrea Arcangeli , Izik Eidus , linux-kernel@vger.kernel.org, linux-mm@kvack.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); } -- 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