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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 EBEC5C43600 for ; Wed, 14 Apr 2021 13:39:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C81B2611AD for ; Wed, 14 Apr 2021 13:39:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1351420AbhDNNkB (ORCPT ); Wed, 14 Apr 2021 09:40:01 -0400 Received: from szxga06-in.huawei.com ([45.249.212.32]:16916 "EHLO szxga06-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1351401AbhDNNkA (ORCPT ); Wed, 14 Apr 2021 09:40:00 -0400 Received: from DGGEMS411-HUB.china.huawei.com (unknown [172.30.72.59]) by szxga06-in.huawei.com (SkyGuard) with ESMTP id 4FL3ST6xz1zjZBp; Wed, 14 Apr 2021 21:37:45 +0800 (CST) Received: from huawei.com (10.175.127.227) by DGGEMS411-HUB.china.huawei.com (10.3.19.211) with Microsoft SMTP Server id 14.3.498.0; Wed, 14 Apr 2021 21:39:29 +0800 From: Zhang Yi To: CC: , , , , , Subject: [RFC PATCH v2 6/7] fs: introduce a usage count into the superblock Date: Wed, 14 Apr 2021 21:47:36 +0800 Message-ID: <20210414134737.2366971-7-yi.zhang@huawei.com> X-Mailer: git-send-email 2.25.4 In-Reply-To: <20210414134737.2366971-1-yi.zhang@huawei.com> References: <20210414134737.2366971-1-yi.zhang@huawei.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7BIT Content-Type: text/plain; charset=US-ASCII X-Originating-IP: [10.175.127.227] X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org Commit <87d8fe1ee6b8> ("add releasepage hooks to block devices which can be used by file systems") introduce a hook that used by ext4 filesystem to release journal buffers, but it doesn't add corresponding concurrency protection that ->bdev_try_to_free_page() could be raced by umount filesystem concurrently. This patch add a usage count on superblock that filesystem can use it to prevent above race and make invoke ->bdev_try_to_free_page() safe. Signed-off-by: Zhang Yi --- include/linux/fs.h | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+) diff --git a/include/linux/fs.h b/include/linux/fs.h index ec8f3ddf4a6a..3c6a5c08c2df 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -41,6 +41,7 @@ #include #include #include +#include #include #include @@ -1547,6 +1548,13 @@ struct super_block { spinlock_t s_inode_wblist_lock; struct list_head s_inodes_wb; /* writeback inodes */ + + /* + * Count users who are using the super_block, used to protect + * umount filesystem concurrently with others. + */ + struct percpu_ref s_usage_counter; + wait_queue_head_t s_usage_waitq; } __randomize_layout; /* Helper functions so that in most cases filesystems will @@ -1765,6 +1773,27 @@ static inline bool sb_start_intwrite_trylock(struct super_block *sb) bool inode_owner_or_capable(struct user_namespace *mnt_userns, const struct inode *inode); +static inline void sb_usage_counter_release(struct percpu_ref *ref) +{ + struct super_block *sb; + + sb = container_of(ref, struct super_block, s_usage_counter); + wake_up(&sb->s_usage_waitq); +} + +static inline int sb_usage_counter_init(struct super_block *sb) +{ + init_waitqueue_head(&sb->s_usage_waitq); + return percpu_ref_init(&sb->s_usage_counter, sb_usage_counter_release, + 0, GFP_KERNEL); +} + +static inline void sb_usage_counter_wait(struct super_block *sb) +{ + percpu_ref_kill(&sb->s_usage_counter); + wait_event(sb->s_usage_waitq, percpu_ref_is_zero(&sb->s_usage_counter)); +} + /* * VFS helper functions.. */ -- 2.25.4