Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751881AbdF2Djh (ORCPT ); Wed, 28 Jun 2017 23:39:37 -0400 Received: from smtp.codeaurora.org ([198.145.29.96]:45592 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751545AbdF2Dj3 (ORCPT ); Wed, 28 Jun 2017 23:39:29 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org B02DF60996 Authentication-Results: pdx-caf-mail.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: pdx-caf-mail.web.codeaurora.org; spf=none smtp.mailfrom=stummala@codeaurora.org From: Sahitya Tummala To: Alexander Polakov , Andrew Morton , Vladimir Davydov , Jan Kara , viro@zeniv.linux.org.uk, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Cc: Sahitya Tummala Subject: [PATCH v4 1/2] mm/list_lru.c: fix list_lru_count_node() to be race free Date: Thu, 29 Jun 2017 09:09:15 +0530 Message-Id: <1498707555-30525-1-git-send-email-stummala@codeaurora.org> X-Mailer: git-send-email 1.9.1 In-Reply-To: <20170628171854.t4sjyjv55j673qzv@esperanza> References: <20170628171854.t4sjyjv55j673qzv@esperanza> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2530 Lines: 77 list_lru_count_node() iterates over all memcgs to get the total number of entries on the node but it can race with memcg_drain_all_list_lrus(), which migrates the entries from a dead cgroup to another. This can return incorrect number of entries from list_lru_count_node(). Fix this by keeping track of entries per node and simply return it in list_lru_count_node(). Signed-off-by: Sahitya Tummala --- include/linux/list_lru.h | 1 + mm/list_lru.c | 14 ++++++-------- 2 files changed, 7 insertions(+), 8 deletions(-) diff --git a/include/linux/list_lru.h b/include/linux/list_lru.h index cb0ba9f..fa7fd03 100644 --- a/include/linux/list_lru.h +++ b/include/linux/list_lru.h @@ -44,6 +44,7 @@ struct list_lru_node { /* for cgroup aware lrus points to per cgroup lists, otherwise NULL */ struct list_lru_memcg *memcg_lrus; #endif + long nr_items; } ____cacheline_aligned_in_smp; struct list_lru { diff --git a/mm/list_lru.c b/mm/list_lru.c index 234676e..7a40fa2 100644 --- a/mm/list_lru.c +++ b/mm/list_lru.c @@ -117,6 +117,7 @@ bool list_lru_add(struct list_lru *lru, struct list_head *item) l = list_lru_from_kmem(nlru, item); list_add_tail(item, &l->list); l->nr_items++; + nlru->nr_items++; spin_unlock(&nlru->lock); return true; } @@ -136,6 +137,7 @@ bool list_lru_del(struct list_lru *lru, struct list_head *item) l = list_lru_from_kmem(nlru, item); list_del_init(item); l->nr_items--; + nlru->nr_items--; spin_unlock(&nlru->lock); return true; } @@ -183,15 +185,10 @@ unsigned long list_lru_count_one(struct list_lru *lru, unsigned long list_lru_count_node(struct list_lru *lru, int nid) { - long count = 0; - int memcg_idx; + struct list_lru_node *nlru; - count += __list_lru_count_one(lru, nid, -1); - if (list_lru_memcg_aware(lru)) { - for_each_memcg_cache_index(memcg_idx) - count += __list_lru_count_one(lru, nid, memcg_idx); - } - return count; + nlru = &lru->node[nid]; + return nlru->nr_items; } EXPORT_SYMBOL_GPL(list_lru_count_node); @@ -226,6 +223,7 @@ unsigned long list_lru_count_node(struct list_lru *lru, int nid) assert_spin_locked(&nlru->lock); case LRU_REMOVED: isolated++; + nlru->nr_items--; /* * If the lru lock has been dropped, our list * traversal is now invalid and so we have to -- Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center, Inc. Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project.