Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964930Ab2B2F1Z (ORCPT ); Wed, 29 Feb 2012 00:27:25 -0500 Received: from mail-pz0-f52.google.com ([209.85.210.52]:47513 "EHLO mail-pz0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751391Ab2B2F1Y (ORCPT ); Wed, 29 Feb 2012 00:27:24 -0500 Authentication-Results: mr.google.com; spf=pass (google.com: domain of hughd@google.com designates 10.68.73.225 as permitted sender) smtp.mail=hughd@google.com; dkim=pass header.i=hughd@google.com Date: Tue, 28 Feb 2012 21:26:56 -0800 (PST) From: Hugh Dickins X-X-Sender: hugh@eggly.anvils To: Andrew Morton cc: KAMEZAWA Hiroyuki , Johannes Weiner , Konstantin Khlebnikov , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH next] memcg: fix deadlock by avoiding stat lock when anon In-Reply-To: Message-ID: References: User-Agent: Alpine 2.00 (LSU 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 Content-Length: 2508 Lines: 70 Fix deadlock in "memcg: use new logic for page stat accounting". page_remove_rmap() first calls mem_cgroup_begin_update_page_stat(), which may take move_lock_mem_cgroup(), unlocked at the end of page_remove_rmap() by mem_cgroup_end_update_page_stat(). The PageAnon case never needs to mem_cgroup_dec_page_stat(page, MEMCG_NR_FILE_MAPPED); but it often needs to mem_cgroup_uncharge_page(), which does lock_page_cgroup(), while holding that move_lock_mem_cgroup(). Whereas mem_cgroup_move_account() calls move_lock_mem_cgroup() while holding lock_page_cgroup(). Since mem_cgroup_begin and end are unnecessary here for PageAnon, simply avoid the deadlock and wasted calls in that case. Signed-off-by: Hugh Dickins --- mm/rmap.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) --- 3.3-rc5-next/mm/rmap.c 2012-02-26 23:51:46.506050210 -0800 +++ linux/mm/rmap.c 2012-02-27 20:25:56.423324211 -0800 @@ -1166,10 +1166,12 @@ void page_add_file_rmap(struct page *pag */ void page_remove_rmap(struct page *page) { + bool anon = PageAnon(page); bool locked; unsigned long flags; - mem_cgroup_begin_update_page_stat(page, &locked, &flags); + if (!anon) + mem_cgroup_begin_update_page_stat(page, &locked, &flags); /* page still mapped by someone else? */ if (!atomic_add_negative(-1, &page->_mapcount)) goto out; @@ -1181,7 +1183,7 @@ void page_remove_rmap(struct page *page) * not if it's in swapcache - there might be another pte slot * containing the swap entry, but page not yet written to swap. */ - if ((!PageAnon(page) || PageSwapCache(page)) && + if ((!anon || PageSwapCache(page)) && page_test_and_clear_dirty(page_to_pfn(page), 1)) set_page_dirty(page); /* @@ -1190,7 +1192,7 @@ void page_remove_rmap(struct page *page) */ if (unlikely(PageHuge(page))) goto out; - if (PageAnon(page)) { + if (anon) { mem_cgroup_uncharge_page(page); if (!PageTransHuge(page)) __dec_zone_page_state(page, NR_ANON_PAGES); @@ -1211,7 +1213,8 @@ void page_remove_rmap(struct page *page) * faster for those pages still in swapcache. */ out: - mem_cgroup_end_update_page_stat(page, &locked, &flags); + if (!anon) + mem_cgroup_end_update_page_stat(page, &locked, &flags); } /* -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/