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[23.128.96.18]) by mx.google.com with ESMTP id lk24si12052998ejb.40.2021.04.08.06.10.42; Thu, 08 Apr 2021 06:11:07 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=huawei.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231645AbhDHNJe (ORCPT + 99 others); Thu, 8 Apr 2021 09:09:34 -0400 Received: from szxga06-in.huawei.com ([45.249.212.32]:16417 "EHLO szxga06-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231520AbhDHNJa (ORCPT ); Thu, 8 Apr 2021 09:09:30 -0400 Received: from DGGEMS413-HUB.china.huawei.com (unknown [172.30.72.59]) by szxga06-in.huawei.com (SkyGuard) with ESMTP id 4FGM4K72mrzkjcw; Thu, 8 Apr 2021 21:07:29 +0800 (CST) Received: from huawei.com (10.175.104.175) by DGGEMS413-HUB.china.huawei.com (10.3.19.213) with Microsoft SMTP Server id 14.3.498.0; Thu, 8 Apr 2021 21:09:08 +0800 From: Miaohe Lin To: CC: , , , , , , , , , , , , , Subject: [PATCH 1/5] mm/swapfile: add percpu_ref support for swap Date: Thu, 8 Apr 2021 09:08:16 -0400 Message-ID: <20210408130820.48233-2-linmiaohe@huawei.com> X-Mailer: git-send-email 2.19.1 In-Reply-To: <20210408130820.48233-1-linmiaohe@huawei.com> References: <20210408130820.48233-1-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 later fixup. Signed-off-by: Miaohe Lin --- include/linux/swap.h | 2 ++ mm/swapfile.c | 25 ++++++++++++++++++++++--- 2 files changed, 24 insertions(+), 3 deletions(-) diff --git a/include/linux/swap.h b/include/linux/swap.h index 144727041e78..849ba5265c11 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 +261,7 @@ 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 */ + 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..724173cd7d0c 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -39,6 +39,7 @@ #include #include #include +#include #include #include @@ -511,6 +512,15 @@ 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); + percpu_ref_exit(&si->users); +} + static void alloc_cluster(struct swap_info_struct *si, unsigned long idx) { struct swap_cluster_info *ci = si->cluster_info; @@ -2500,7 +2510,7 @@ 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_reinit(&p->users); spin_lock(&swap_lock); spin_lock(&p->lock); _enable_swap_info(p); @@ -2621,11 +2631,13 @@ 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 */ - synchronize_rcu(); + wait_for_completion(&p->comp); flush_work(&p->discard_work); @@ -3132,7 +3144,7 @@ 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 +3175,12 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) INIT_WORK(&p->discard_work, swap_discard_work); + init_completion(&p->comp); + error = percpu_ref_init(&p->users, swap_users_ref_free, + PERCPU_REF_INIT_DEAD, GFP_KERNEL); + if (unlikely(error)) + goto bad_swap; + name = getname(specialfile); if (IS_ERR(name)) { error = PTR_ERR(name); @@ -3356,6 +3374,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) bad_swap_unlock_inode: inode_unlock(inode); bad_swap: + percpu_ref_exit(&p->users); free_percpu(p->percpu_cluster); p->percpu_cluster = NULL; free_percpu(p->cluster_next_cpu); -- 2.19.1