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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 95FCFC54EBE for ; Fri, 13 Jan 2023 01:25:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240552AbjAMBZY (ORCPT ); Thu, 12 Jan 2023 20:25:24 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34484 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236952AbjAMBZU (ORCPT ); Thu, 12 Jan 2023 20:25:20 -0500 Received: from dggsgout12.his.huawei.com (dggsgout12.his.huawei.com [45.249.212.56]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C456B5D8B3; Thu, 12 Jan 2023 17:25:17 -0800 (PST) Received: from mail02.huawei.com (unknown [172.30.67.143]) by dggsgout12.his.huawei.com (SkyGuard) with ESMTP id 4NtNyG3g5Xz4f3nqD; Fri, 13 Jan 2023 09:25:10 +0800 (CST) Received: from [10.174.176.73] (unknown [10.174.176.73]) by APP3 (Coremail) with SMTP id _Ch0CgDX0R_3ssBjUrLoBQ--.19657S3; Fri, 13 Jan 2023 09:25:13 +0800 (CST) Subject: Re: [PATCH v2 1/2] blk-iocost: add refcounting for iocg To: Tejun Heo , Yu Kuai Cc: hch@infradead.org, josef@toxicpanda.com, axboe@kernel.dk, cgroups@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, yi.zhang@huawei.com, "yukuai (C)" References: <875eb43e-202d-5b81-0bff-ef0434358d99@huaweicloud.com> <53b30ac8-d608-ba0b-8b1b-7fe5cfed6d61@huaweicloud.com> <4aeef320-c6c8-d9b4-8826-d58f00ea6264@huaweicloud.com> From: Yu Kuai Message-ID: Date: Fri, 13 Jan 2023 09:25:11 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=gbk; format=flowed Content-Transfer-Encoding: 8bit X-CM-TRANSID: _Ch0CgDX0R_3ssBjUrLoBQ--.19657S3 X-Coremail-Antispam: 1UD129KBjvdXoW7XF4fCw17uF17tFWUXFWfGrg_yoWkJrX_u3 4093WUW348GrnxCas5KF45X397KryUGry8ur40gr97GF9aq3yqkFn7Cwn3CFyUA3ykXr9I vr95Zw18Gry7WjkaLaAFLSUrUUUUUb8apTn2vfkv8UJUUUU8Yxn0WfASr-VFAUDa7-sFnT 9fnUUIcSsGvfJTRUUUba8FF20E14v26r4j6ryUM7CY07I20VC2zVCF04k26cxKx2IYs7xG 6rWj6s0DM7CIcVAFz4kK6r1j6r18M28lY4IEw2IIxxk0rwA2F7IY1VAKz4vEj48ve4kI8w A2z4x0Y4vE2Ix0cI8IcVAFwI0_tr0E3s1l84ACjcxK6xIIjxv20xvEc7CjxVAFwI0_Gr1j 6F4UJwA2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xvwVC2z280aVCY1x0267AKxVW0oV Cq3wAS0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFcxC0VAKzVAqx4xG6I80ewAv7VC0 I7IYx2IY67AKxVWUGVWUXwAv7VC2z280aVAFwI0_Jr0_Gr1lOx8S6xCaFVCjc4AY6r1j6r 4UM4x0Y48IcVAKI48JM4x0x7Aq67IIx4CEVc8vx2IErcIFxwACI402YVCY1x02628vn2kI c2xKxwCYjI0SjxkI62AI1cAE67vIY487MxAIw28IcxkI7VAKI48JMxC20s026xCaFVCjc4 AY6r1j6r4UMI8I3I0E5I8CrVAFwI0_Jr0_Jr4lx2IqxVCjr7xvwVAFwI0_JrI_JrWlx4CE 17CEb7AF67AKxVWUtVW8ZwCIc40Y0x0EwIxGrwCI42IY6xIIjxv20xvE14v26r1j6r1xMI IF0xvE2Ix0cI8IcVCY1x0267AKxVW8JVWxJwCI42IY6xAIw20EY4v20xvaj40_Wr1j6rW3 Jr1lIxAIcVC2z280aVAFwI0_Jr0_Gr1lIxAIcVC2z280aVCY1x0267AKxVW8JVW8JrUvcS sGvfC2KfnxnUUI43ZEXa7VU1a9aPUUUUU== X-CM-SenderInfo: 51xn3trlr6x35dzhxuhorxvhhfrp/ X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, ÔÚ 2023/01/13 9:15, Tejun Heo дµÀ: > Hello, > > On Fri, Jan 13, 2023 at 09:10:25AM +0800, Yu Kuai wrote: >>> only activate the policy when the controller is actually enabled. So, idk. >>> What's wrong with synchronizing the two removal paths? blkcg policies are >>> combinations of cgroups and block device configurations, so having exit >>> paths from both sides is kinda natural. >> >> I still can't figure out how to synchronizing them will a mutex. Maybe >> I'm being foolish... > > Hmm... can't you just use e.g. per-bdev mutex which is grabbed by both > blkg_free_workfn() and blkcg_deactivate_policy()? > I think hold the lock in blkg_free_workfn() is too late, pd_free_fn() for parent from blkcg_deactivate_policy() can be called first. t1: remove cgroup t1/t2 blkcg_destroy_blkgs blkg_destroy percpu_ref_kill(&blkg->refcnt) blkg_release blkg_free schedule_work(&blkg->free_work) // t1 is done t2: handle t1 from removing device blkcg_deactivate_policy pd_free_fn // free parent t3: from t1 blkg_free_workfn pd_free_fn // free child Thanks, Kuai