Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751166AbdCQGt4 (ORCPT ); Fri, 17 Mar 2017 02:49:56 -0400 Received: from mga07.intel.com ([134.134.136.100]:39872 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751108AbdCQGtz (ORCPT ); Fri, 17 Mar 2017 02:49:55 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.36,175,1486454400"; d="scan'208";a="945346676" From: "Huang, Ying" To: Andrew Morton Cc: Andi Kleen , Dave Hansen , Shaohua Li , Rik van Riel , Huang Ying , Tim Chen , Michal Hocko , "Kirill A. Shutemov" , Ingo Molnar , Vegard Nossum , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH 3/5] mm, swap: Avoid lock swap_avail_lock when held cluster lock Date: Fri, 17 Mar 2017 14:46:21 +0800 Message-Id: <20170317064635.12792-3-ying.huang@intel.com> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20170317064635.12792-1-ying.huang@intel.com> References: <20170317064635.12792-1-ying.huang@intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1510 Lines: 43 From: Huang Ying Cluster lock is used to protect the swap_cluster_info and corresponding elements in swap_info_struct->swap_map[]. But it is found that now in scan_swap_map_slots(), swap_avail_lock may be acquired when cluster lock is held. This does no good except making the locking more complex and improving the potential locking contention, because the swap_info_struct->lock is used to protect the data structure operated in the code already. Fix this via moving the corresponding operations in scan_swap_map_slots() out of cluster lock. Signed-off-by: "Huang, Ying" Acked-by: Tim Chen --- mm/swapfile.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/mm/swapfile.c b/mm/swapfile.c index 42fd620dcf4c..53b5881ee0d6 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -672,6 +672,9 @@ static int scan_swap_map_slots(struct swap_info_struct *si, else goto done; } + si->swap_map[offset] = usage; + inc_cluster_info_page(si, si->cluster_info, offset); + unlock_cluster(ci); if (offset == si->lowest_bit) si->lowest_bit++; @@ -685,9 +688,6 @@ static int scan_swap_map_slots(struct swap_info_struct *si, plist_del(&si->avail_list, &swap_avail_head); spin_unlock(&swap_avail_lock); } - si->swap_map[offset] = usage; - inc_cluster_info_page(si, si->cluster_info, offset); - unlock_cluster(ci); si->cluster_next = offset + 1; slots[n_ret++] = swp_entry(si->type, offset); -- 2.11.0