From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail191.messagelabs.com (mail191.messagelabs.com [216.82.242.19]) by kanga.kvack.org (Postfix) with SMTP id 556888D0039 for ; Thu, 27 Jan 2011 00:07:40 -0500 (EST) Received: from m2.gw.fujitsu.co.jp (unknown [10.0.50.72]) by fgwmail5.fujitsu.co.jp (Postfix) with ESMTP id EF65B3EE0C1 for ; Thu, 27 Jan 2011 14:07:37 +0900 (JST) Received: from smail (m2 [127.0.0.1]) by outgoing.m2.gw.fujitsu.co.jp (Postfix) with ESMTP id D613145DE61 for ; Thu, 27 Jan 2011 14:07:37 +0900 (JST) Received: from s2.gw.fujitsu.co.jp (s2.gw.fujitsu.co.jp [10.0.50.92]) by m2.gw.fujitsu.co.jp (Postfix) with ESMTP id B647C45DE4D for ; Thu, 27 Jan 2011 14:07:37 +0900 (JST) Received: from s2.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s2.gw.fujitsu.co.jp (Postfix) with ESMTP id A9FDB1DB8038 for ; Thu, 27 Jan 2011 14:07:37 +0900 (JST) Received: from ml14.s.css.fujitsu.com (ml14.s.css.fujitsu.com [10.249.87.104]) by s2.gw.fujitsu.co.jp (Postfix) with ESMTP id 6524F1DB803C for ; Thu, 27 Jan 2011 14:07:37 +0900 (JST) Date: Thu, 27 Jan 2011 14:01:32 +0900 From: KAMEZAWA Hiroyuki Subject: [PATCH] memcg: fix ugly initialization of return value is in caller Message-Id: <20110127140132.35f4285e.kamezawa.hiroyu@jp.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: "linux-mm@kvack.org" Cc: "linux-kernel@vger.kernel.org" , "akpm@linux-foundation.org" , "nishimura@mxp.nes.nec.co.jp" , "hannes@cmpxchg.org" , "balbir@linux.vnet.ibm.com" List-ID: Based on mm-of-the-moment snapshot 2011-01-25-15-47 == From: KAMEZAWA Hiroyuki This patch is for removing initialization of vaiable in caller of memory cgroup function. Actually, it's return value of memcg function but it's initialized in caller. Some memory cgroup uses following style to bring the result of start function to the end function for avoiding races. mem_cgroup_start_A(&(*ptr)) /* Something very complicated can happen here. */ mem_cgroup_end_A(*ptr) In some calls, *ptr should be initialized to NULL be caller. But it's ugly. This patch fixes that *ptr is initialized by _start function. Changelog: - removed unnecessary comments. Acked-by: Johannes Weiner Acked-by: Daisuke Nishimura Signed-off-by: KAMEZAWA Hiroyuki --- mm/memcontrol.c | 8 ++++++-- mm/memory.c | 2 +- mm/migrate.c | 2 +- mm/swapfile.c | 2 +- 4 files changed, 9 insertions(+), 5 deletions(-) Index: mmotm-0125/mm/memcontrol.c =================================================================== --- mmotm-0125.orig/mm/memcontrol.c +++ mmotm-0125/mm/memcontrol.c @@ -2413,7 +2413,7 @@ int mem_cgroup_cache_charge(struct page /* shmem */ if (PageSwapCache(page)) { - struct mem_cgroup *mem = NULL; + struct mem_cgroup *mem; ret = mem_cgroup_try_charge_swapin(mm, page, gfp_mask, &mem); if (!ret) @@ -2439,6 +2439,8 @@ int mem_cgroup_try_charge_swapin(struct struct mem_cgroup *mem; int ret; + *ptr = NULL; + if (mem_cgroup_disabled()) return 0; @@ -2854,6 +2856,8 @@ int mem_cgroup_prepare_migration(struct enum charge_type ctype; int ret = 0; + *ptr = NULL; + VM_BUG_ON(PageTransHuge(page)); if (mem_cgroup_disabled()) return 0; @@ -2996,7 +3000,7 @@ int mem_cgroup_shmem_charge_fallback(str struct mm_struct *mm, gfp_t gfp_mask) { - struct mem_cgroup *mem = NULL; + struct mem_cgroup *mem; int ret; if (mem_cgroup_disabled()) Index: mmotm-0125/mm/migrate.c =================================================================== --- mmotm-0125.orig/mm/migrate.c +++ mmotm-0125/mm/migrate.c @@ -623,7 +623,7 @@ static int unmap_and_move(new_page_t get struct page *newpage = get_new_page(page, private, &result); int remap_swapcache = 1; int charge = 0; - struct mem_cgroup *mem = NULL; + struct mem_cgroup *mem; struct anon_vma *anon_vma = NULL; if (!newpage) Index: mmotm-0125/mm/memory.c =================================================================== --- mmotm-0125.orig/mm/memory.c +++ mmotm-0125/mm/memory.c @@ -2707,7 +2707,7 @@ static int do_swap_page(struct mm_struct swp_entry_t entry; pte_t pte; int locked; - struct mem_cgroup *ptr = NULL; + struct mem_cgroup *ptr; int exclusive = 0; int ret = 0; Index: mmotm-0125/mm/swapfile.c =================================================================== --- mmotm-0125.orig/mm/swapfile.c +++ mmotm-0125/mm/swapfile.c @@ -880,7 +880,7 @@ 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 mem_cgroup *ptr = NULL; + struct mem_cgroup *ptr; spinlock_t *ptl; pte_t *pte; int ret = 1; -- 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/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: email@kvack.org