From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E94C9C433B4 for ; Sat, 17 Apr 2021 09:41:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C7F3E61208 for ; Sat, 17 Apr 2021 09:41:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235968AbhDQJmO (ORCPT ); Sat, 17 Apr 2021 05:42:14 -0400 Received: from szxga06-in.huawei.com ([45.249.212.32]:17370 "EHLO szxga06-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229972AbhDQJmN (ORCPT ); Sat, 17 Apr 2021 05:42:13 -0400 Received: from DGGEMS410-HUB.china.huawei.com (unknown [172.30.72.58]) by szxga06-in.huawei.com (SkyGuard) with ESMTP id 4FMp2b23DGzlYHb; Sat, 17 Apr 2021 17:39:51 +0800 (CST) Received: from huawei.com (10.175.104.175) by DGGEMS410-HUB.china.huawei.com (10.3.19.210) with Microsoft SMTP Server id 14.3.498.0; Sat, 17 Apr 2021 17:41:37 +0800 From: Miaohe Lin To: CC: , , , , , , , , , , , , , Subject: [PATCH v2 1/5] mm/swapfile: add percpu_ref support for swap Date: Sat, 17 Apr 2021 05:40:35 -0400 Message-ID: <20210417094039.51711-2-linmiaohe@huawei.com> X-Mailer: git-send-email 2.19.1 In-Reply-To: <20210417094039.51711-1-linmiaohe@huawei.com> References: <20210417094039.51711-1-linmiaohe@huawei.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7BIT Content-Type: text/plain; charset=US-ASCII X-Originating-IP: [10.175.104.175] X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org We will use percpu-refcount to serialize against concurrent swapoff. This patch adds the percpu_ref support for swap. Signed-off-by: Miaohe Lin --- include/linux/swap.h | 3 +++ mm/swapfile.c | 33 +++++++++++++++++++++++++++++---- 2 files changed, 32 insertions(+), 4 deletions(-) diff --git a/include/linux/swap.h b/include/linux/swap.h index 144727041e78..8be36eb58b7a 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -240,6 +240,7 @@ struct swap_cluster_list { * The in-memory structure used to track swap areas. */ struct swap_info_struct { + struct percpu_ref users; /* serialization against concurrent swapoff */ unsigned long flags; /* SWP_USED etc: see above */ signed short prio; /* swap priority of this type */ struct plist_node list; /* entry in swap_active_head */ @@ -260,6 +261,8 @@ struct swap_info_struct { struct block_device *bdev; /* swap device or bdev of swap file */ struct file *swap_file; /* seldom referenced */ unsigned int old_block_size; /* seldom referenced */ + bool ref_initialized; /* seldom referenced */ + struct completion comp; /* seldom referenced */ #ifdef CONFIG_FRONTSWAP unsigned long *frontswap_map; /* frontswap in-use, one bit per page */ atomic_t frontswap_pages; /* frontswap pages in-use counter */ diff --git a/mm/swapfile.c b/mm/swapfile.c index 149e77454e3c..66515a3a2824 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -39,6 +39,7 @@ #include #include #include +#include #include #include @@ -511,6 +512,14 @@ static void swap_discard_work(struct work_struct *work) spin_unlock(&si->lock); } +static void swap_users_ref_free(struct percpu_ref *ref) +{ + struct swap_info_struct *si; + + si = container_of(ref, struct swap_info_struct, users); + complete(&si->comp); +} + static void alloc_cluster(struct swap_info_struct *si, unsigned long idx) { struct swap_cluster_info *ci = si->cluster_info; @@ -2500,7 +2509,7 @@ static void enable_swap_info(struct swap_info_struct *p, int prio, * Guarantee swap_map, cluster_info, etc. fields are valid * between get/put_swap_device() if SWP_VALID bit is set */ - synchronize_rcu(); + percpu_ref_resurrect(&p->users); spin_lock(&swap_lock); spin_lock(&p->lock); _enable_swap_info(p); @@ -2621,11 +2630,18 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile) p->flags &= ~SWP_VALID; /* mark swap device as invalid */ spin_unlock(&p->lock); spin_unlock(&swap_lock); + + percpu_ref_kill(&p->users); /* - * wait for swap operations protected by get/put_swap_device() - * to complete + * We need synchronize_rcu() here to protect the accessing + * to the swap cache data structure. */ synchronize_rcu(); + /* + * Wait for swap operations protected by get/put_swap_device() + * to complete. + */ + wait_for_completion(&p->comp); flush_work(&p->discard_work); @@ -3132,7 +3148,7 @@ static bool swap_discardable(struct swap_info_struct *si) SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) { struct swap_info_struct *p; - struct filename *name; + struct filename *name = NULL; struct file *swap_file = NULL; struct address_space *mapping; int prio; @@ -3163,6 +3179,15 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) INIT_WORK(&p->discard_work, swap_discard_work); + if (!p->ref_initialized) { + error = percpu_ref_init(&p->users, swap_users_ref_free, + PERCPU_REF_INIT_DEAD, GFP_KERNEL); + if (unlikely(error)) + goto bad_swap; + init_completion(&p->comp); + p->ref_initialized = true; + } + name = getname(specialfile); if (IS_ERR(name)) { error = PTR_ERR(name); -- 2.19.1