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=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 A6D87C433ED for ; Mon, 12 Apr 2021 03:31:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7A69961246 for ; Mon, 12 Apr 2021 03:31:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236430AbhDLDbj (ORCPT ); Sun, 11 Apr 2021 23:31:39 -0400 Received: from mga09.intel.com ([134.134.136.24]:53566 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235366AbhDLDbh (ORCPT ); Sun, 11 Apr 2021 23:31:37 -0400 IronPort-SDR: 0ukDDaNAh/+Y0Hy07hI2q/KgUptjSWq/Y2JE/YXwh4fkiLm0EXnUVcONI1VvIIt0k57/V4kd5B vOoosKpolrig== X-IronPort-AV: E=McAfee;i="6000,8403,9951"; a="194214130" X-IronPort-AV: E=Sophos;i="5.82,214,1613462400"; d="scan'208";a="194214130" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Apr 2021 20:30:59 -0700 IronPort-SDR: Q8HjgPHaqEtlpMrqQfI0O8jMEibBYK91zautCNPZK5d813piMOSSX4qc52aBx/fODeBBs7F4Ye mfNIg232OR6w== X-IronPort-AV: E=Sophos;i="5.82,214,1613462400"; d="scan'208";a="423611895" Received: from yhuang6-desk1.sh.intel.com (HELO yhuang6-desk1.ccr.corp.intel.com) ([10.239.13.1]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Apr 2021 20:30:56 -0700 From: "Huang, Ying" To: Miaohe Lin Cc: , , , , , , , , , , , , Subject: Re: [PATCH 1/5] mm/swapfile: add percpu_ref support for swap References: <20210408130820.48233-1-linmiaohe@huawei.com> <20210408130820.48233-2-linmiaohe@huawei.com> Date: Mon, 12 Apr 2021 11:30:54 +0800 In-Reply-To: <20210408130820.48233-2-linmiaohe@huawei.com> (Miaohe Lin's message of "Thu, 8 Apr 2021 09:08:16 -0400") Message-ID: <87fszww55d.fsf@yhuang6-desk1.ccr.corp.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=ascii Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Miaohe Lin writes: > 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); Because percpu_ref_exit() is used, we cannot use percpu_ref_tryget() in get_swap_device(), better to add comments there. > +} > + > 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); Although the effect is same, I think it's better to use percpu_ref_resurrect() here to improve code readability. > 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); Better to move percpu_ref_kill() after the comments. And maybe revise the comments. > > 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); Usually the resource freeing order matches their allocating order reversely. So, if there's no special reason, please follow that rule. Best Regards, Huang, Ying > free_percpu(p->percpu_cluster); > p->percpu_cluster = NULL; > free_percpu(p->cluster_next_cpu); 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=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 06707C433ED for ; Mon, 12 Apr 2021 03:31:04 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 85335610CA for ; Mon, 12 Apr 2021 03:31:03 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 85335610CA Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 110946B006E; Sun, 11 Apr 2021 23:31:03 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 09A136B0070; Sun, 11 Apr 2021 23:31:03 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E2E1E6B0071; Sun, 11 Apr 2021 23:31:02 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0021.hostedemail.com [216.40.44.21]) by kanga.kvack.org (Postfix) with ESMTP id C17DD6B006E for ; Sun, 11 Apr 2021 23:31:02 -0400 (EDT) Received: from smtpin34.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 79CF218015CBB for ; Mon, 12 Apr 2021 03:31:02 +0000 (UTC) X-FDA: 78022288764.34.229F0B5 Received: from mga07.intel.com (mga07.intel.com [134.134.136.100]) by imf07.hostedemail.com (Postfix) with ESMTP id 25A66A0000FF for ; Mon, 12 Apr 2021 03:31:00 +0000 (UTC) IronPort-SDR: xwCa28BM81Jjeq0wejRo97Tg2xr38nURP3+IQWxmJ70T9DH99d3YvegmchBHW6CtAQy8sNtKYc yCMTeT2JgL7Q== X-IronPort-AV: E=McAfee;i="6000,8403,9951"; a="258078742" X-IronPort-AV: E=Sophos;i="5.82,214,1613462400"; d="scan'208";a="258078742" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Apr 2021 20:30:59 -0700 IronPort-SDR: Q8HjgPHaqEtlpMrqQfI0O8jMEibBYK91zautCNPZK5d813piMOSSX4qc52aBx/fODeBBs7F4Ye mfNIg232OR6w== X-IronPort-AV: E=Sophos;i="5.82,214,1613462400"; d="scan'208";a="423611895" Received: from yhuang6-desk1.sh.intel.com (HELO yhuang6-desk1.ccr.corp.intel.com) ([10.239.13.1]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Apr 2021 20:30:56 -0700 From: "Huang, Ying" To: Miaohe Lin Cc: , , , , , , , , , , , , Subject: Re: [PATCH 1/5] mm/swapfile: add percpu_ref support for swap References: <20210408130820.48233-1-linmiaohe@huawei.com> <20210408130820.48233-2-linmiaohe@huawei.com> Date: Mon, 12 Apr 2021 11:30:54 +0800 In-Reply-To: <20210408130820.48233-2-linmiaohe@huawei.com> (Miaohe Lin's message of "Thu, 8 Apr 2021 09:08:16 -0400") Message-ID: <87fszww55d.fsf@yhuang6-desk1.ccr.corp.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=ascii X-Stat-Signature: itobpcdooi6z97exjh6hekbx83g66qto X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 25A66A0000FF Received-SPF: none (intel.com>: No applicable sender policy available) receiver=imf07; identity=mailfrom; envelope-from=""; helo=mga07.intel.com; client-ip=134.134.136.100 X-HE-DKIM-Result: none/none X-HE-Tag: 1618198260-695821 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Miaohe Lin writes: > 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); Because percpu_ref_exit() is used, we cannot use percpu_ref_tryget() in get_swap_device(), better to add comments there. > +} > + > 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); Although the effect is same, I think it's better to use percpu_ref_resurrect() here to improve code readability. > 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); Better to move percpu_ref_kill() after the comments. And maybe revise the comments. > > 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); Usually the resource freeing order matches their allocating order reversely. So, if there's no special reason, please follow that rule. Best Regards, Huang, Ying > free_percpu(p->percpu_cluster); > p->percpu_cluster = NULL; > free_percpu(p->cluster_next_cpu);