From patchwork Tue Dec 27 12:55:01 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yu Kuai X-Patchwork-Id: 36888 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a5d:4e01:0:0:0:0:0 with SMTP id p1csp1369641wrt; Tue, 27 Dec 2022 04:38:56 -0800 (PST) X-Google-Smtp-Source: AMrXdXvlqJGpxldMqT77eXdksOAMPucfsiOYsbc5vm5RPoHqxFM+qMdo7BK19bxVbfmRQJgf8LkS X-Received: by 2002:a17:907:d50e:b0:81f:fc05:2ba0 with SMTP id wb14-20020a170907d50e00b0081ffc052ba0mr19135868ejc.2.1672144735771; Tue, 27 Dec 2022 04:38:55 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1672144735; cv=none; d=google.com; s=arc-20160816; b=GIkXRvy44x3R8+wBX7ndKDu64a5rmU8HfxCLzjeMmrL8rQRSBWRoscwxm9wjiaNr/D biX1CYMpyn+g1Iz4hsAn0qiQAjGPK4/y9g6nROJ9LoLnJStIbWzOnBa0kOFxXL6D/Or+ 3BDt+e+4/PsrnUuWXUzlhvFrx6rzHzdY0UU/9VViyJ0HLQo42IJ+wT2veDYmhzZJiS8W AWPMZvS2D6/B8W7mVqWOUxD/pxr5nryLz3q5721sEdFsE0ljH/oyZCO/wCriiUF1CX7d a7h2UReinZmAWGObUOURlGXO9pp3FnXp7J7dP2b7sYmM5pmXekcOOJwQqdzZ4NraVAS1 21/g== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-transfer-encoding:mime-version :references:in-reply-to:message-id:date:subject:cc:to:from; bh=RNn4u4ED5/lzklIwhbgMo2lHoXUsXIIm2iQmiqcRCVo=; b=ZG6DIDdhsW+G3usP9rbzBHmwGFCmAyiZ4BdWyJLKhKU2u1BbmN2+lZXSq8DC+w9QpJ BZiSIlrfYFo0sNwTcUzgxyGWlMrIAbTy5jvXrz3wULdk9pet4wzo3WN/fyDkNWyjBJ0T Ix85UnlO2bpyHEQCqJwfPvUVRoKhnvCoR66MJV4muqN9p8lex+Usny0c0QWfOzjWBvF6 WTAUm9K4xQOmAY28Yp099kpplOZJIT1FeNl+1R5wt8AFax3SXjZ+YVNT2EI2MSvdvck0 pBQpKU4GYVQ2o3WDOM7zE+CcU++pdeutp9bOlNMjdrhNFiQf9qgBG6OGOz7YA3wBYI+d +uKg== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: from out1.vger.email (out1.vger.email. [2620:137:e000::1:20]) by mx.google.com with ESMTP id xg11-20020a170907320b00b007c14e98e3a1si11088122ejb.752.2022.12.27.04.38.30; Tue, 27 Dec 2022 04:38:55 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230147AbiL0Mer (ORCPT + 99 others); Tue, 27 Dec 2022 07:34:47 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42026 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229635AbiL0Mek (ORCPT ); Tue, 27 Dec 2022 07:34:40 -0500 Received: from dggsgout12.his.huawei.com (unknown [45.249.212.56]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9F9132A3; Tue, 27 Dec 2022 04:34:39 -0800 (PST) Received: from mail02.huawei.com (unknown [172.30.67.153]) by dggsgout12.his.huawei.com (SkyGuard) with ESMTP id 4NhDcR4cLHz4f3jMg; Tue, 27 Dec 2022 20:34:31 +0800 (CST) Received: from huaweicloud.com (unknown [10.175.127.227]) by APP4 (Coremail) with SMTP id gCh0CgAHvbBZ5qpjAnByAg--.34791S5; Tue, 27 Dec 2022 20:34:34 +0800 (CST) From: Yu Kuai To: tj@kernel.org, hch@infradead.org, josef@toxicpanda.com, axboe@kernel.dk Cc: cgroups@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, yukuai3@huawei.com, yukuai1@huaweicloud.com, yi.zhang@huawei.com Subject: [PATCH v2 1/2] blk-iocost: add refcounting for iocg Date: Tue, 27 Dec 2022 20:55:01 +0800 Message-Id: <20221227125502.541931-2-yukuai1@huaweicloud.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20221227125502.541931-1-yukuai1@huaweicloud.com> References: <20221227125502.541931-1-yukuai1@huaweicloud.com> MIME-Version: 1.0 X-CM-TRANSID: gCh0CgAHvbBZ5qpjAnByAg--.34791S5 X-Coremail-Antispam: 1UD129KBjvJXoWxAw1kKFW8ZFW7CryxXr45GFg_yoW5Kr43pF 13W345Cay5JF4xuws8t3ZrXw1rAw4fWr4kKrWfWwnYyr17Ar10q3WkA348Ga4rCFZxZr43 XF18KFWUGr4jvF7anT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUBE14x267AKxVW5JVWrJwAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2048vs2IY020E87I2jVAFwI0_Jr4l82xGYIkIc2 x26xkF7I0E14v26r1I6r4UM28lY4IEw2IIxxk0rwA2F7IY1VAKz4vEj48ve4kI8wA2z4x0 Y4vE2Ix0cI8IcVAFwI0_tr0E3s1l84ACjcxK6xIIjxv20xvEc7CjxVAFwI0_Gr1j6F4UJw A2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xvwVC2z280aVCY1x0267AKxVW0oVCq3wAS 0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFcxC0VAKzVAqx4xG6I80ewAv7VC0I7IYx2 IY67AKxVWUGVWUXwAv7VC2z280aVAFwI0_Jr0_Gr1lOx8S6xCaFVCjc4AY6r1j6r4UM4x0 Y48IcxkI7VAKI48JM4x0x7Aq67IIx4CEVc8vx2IErcIFxwACI402YVCY1x02628vn2kIc2 xKxwCF04k20xvY0x0EwIxGrwCFx2IqxVCFs4IE7xkEbVWUJVW8JwC20s026c02F40E14v2 6r1j6r18MI8I3I0E7480Y4vE14v26r106r1rMI8E67AF67kF1VAFwI0_Jw0_GFylIxkGc2 Ij64vIr41lIxAIcVC0I7IYx2IY67AKxVWUJVWUCwCI42IY6xIIjxv20xvEc7CjxVAFwI0_ Gr0_Cr1lIxAIcVCF04k26cxKx2IYs7xG6r1j6r1xMIIF0xvEx4A2jsIE14v26r1j6r4UMI IF0xvEx4A2jsIEc7CjxVAFwI0_Gr0_Gr1UYxBIdaVFxhVjvjDU0xZFpf9x0JUHyIUUUUUU = X-CM-SenderInfo: 51xn3trlr6x35dzhxuhorxvhhfrp/ X-CFilter-Loop: Reflected X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,SPF_HELO_NONE, SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1753370838813828650?= X-GMAIL-MSGID: =?utf-8?q?1753370838813828650?= From: Yu Kuai iocost requires that child iocg must exit before parent iocg, otherwise kernel might crash in ioc_timer_fn(). However, currently iocg is exited in pd_free_fn(), which can't guarantee such order: 1) remove cgroup can concurrent with deactivate policy; 2) blkg_free() triggered by remove cgroup is asynchronously, remove child cgroup can concurrent with remove parent cgroup; Fix the problem by add refcounting for iocg, and child iocg will grab reference of parent iocg, so that parent iocg will wait for all child iocg to be exited. Signed-off-by: Yu Kuai --- block/blk-iocost.c | 74 +++++++++++++++++++++++++++++++--------------- 1 file changed, 50 insertions(+), 24 deletions(-) diff --git a/block/blk-iocost.c b/block/blk-iocost.c index 7a0d754b9eb2..525e93e1175a 100644 --- a/block/blk-iocost.c +++ b/block/blk-iocost.c @@ -461,6 +461,8 @@ struct ioc_gq { struct blkg_policy_data pd; struct ioc *ioc; + refcount_t ref; + /* * A iocg can get its weight from two sources - an explicit * per-device-cgroup configuration or the default weight of the @@ -2943,9 +2945,53 @@ static struct blkg_policy_data *ioc_pd_alloc(gfp_t gfp, struct request_queue *q, return NULL; } + refcount_set(&iocg->ref, 1); return &iocg->pd; } +static void iocg_get(struct ioc_gq *iocg) +{ + refcount_inc(&iocg->ref); +} + +static void iocg_put(struct ioc_gq *iocg) +{ + struct ioc *ioc = iocg->ioc; + unsigned long flags; + struct ioc_gq *parent = NULL; + + if (!refcount_dec_and_test(&iocg->ref)) + return; + + if (iocg->level > 0) + parent = iocg->ancestors[iocg->level - 1]; + + if (ioc) { + spin_lock_irqsave(&ioc->lock, flags); + + if (!list_empty(&iocg->active_list)) { + struct ioc_now now; + + ioc_now(ioc, &now); + propagate_weights(iocg, 0, 0, false, &now); + list_del_init(&iocg->active_list); + } + + WARN_ON_ONCE(!list_empty(&iocg->walk_list)); + WARN_ON_ONCE(!list_empty(&iocg->surplus_list)); + + spin_unlock_irqrestore(&ioc->lock, flags); + + hrtimer_cancel(&iocg->waitq_timer); + } + + free_percpu(iocg->pcpu_stat); + kfree(iocg); + + if (parent) + iocg_put(parent); +} + static void ioc_pd_init(struct blkg_policy_data *pd) { struct ioc_gq *iocg = pd_to_iocg(pd); @@ -2973,6 +3019,9 @@ static void ioc_pd_init(struct blkg_policy_data *pd) iocg->level = blkg->blkcg->css.cgroup->level; + if (blkg->parent) + iocg_get(blkg_to_iocg(blkg->parent)); + for (tblkg = blkg; tblkg; tblkg = tblkg->parent) { struct ioc_gq *tiocg = blkg_to_iocg(tblkg); iocg->ancestors[tiocg->level] = tiocg; @@ -2985,30 +3034,7 @@ static void ioc_pd_init(struct blkg_policy_data *pd) static void ioc_pd_free(struct blkg_policy_data *pd) { - struct ioc_gq *iocg = pd_to_iocg(pd); - struct ioc *ioc = iocg->ioc; - unsigned long flags; - - if (ioc) { - spin_lock_irqsave(&ioc->lock, flags); - - if (!list_empty(&iocg->active_list)) { - struct ioc_now now; - - ioc_now(ioc, &now); - propagate_weights(iocg, 0, 0, false, &now); - list_del_init(&iocg->active_list); - } - - WARN_ON_ONCE(!list_empty(&iocg->walk_list)); - WARN_ON_ONCE(!list_empty(&iocg->surplus_list)); - - spin_unlock_irqrestore(&ioc->lock, flags); - - hrtimer_cancel(&iocg->waitq_timer); - } - free_percpu(iocg->pcpu_stat); - kfree(iocg); + iocg_put(pd_to_iocg(pd)); } static void ioc_pd_stat(struct blkg_policy_data *pd, struct seq_file *s) From patchwork Tue Dec 27 12:55:02 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yu Kuai X-Patchwork-Id: 36886 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a5d:4e01:0:0:0:0:0 with SMTP id p1csp1369640wrt; Tue, 27 Dec 2022 04:38:55 -0800 (PST) X-Google-Smtp-Source: AMrXdXvsrmHWsD6zjYJ2BaiWCsz+X9Tedlhe5EQ7hXXhVNrCmBeuGNqey4O61PnOFTlrvZ9JJkal X-Received: by 2002:a17:907:d48e:b0:7ae:b2e4:7b3f with SMTP id vj14-20020a170907d48e00b007aeb2e47b3fmr18918898ejc.8.1672144735813; Tue, 27 Dec 2022 04:38:55 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1672144735; cv=none; d=google.com; s=arc-20160816; b=wOjBxmEqYhCEkmA3wlp/AOlrQ7y5A7QRN5Nztfu13aplw0MjFSRtTZwoBznBFVM3Mg ibZd4P8BYHRsKAX5eWktc10hcW4OwAqPUzdRPri1a06T9bRAkxW+1YVwVKuz7G7zCrnC VHS6iG7plMIVck1Vv4mg00JtstX++Ay0KIy3ypbZR7/NPU7I8Malcmcj3sKf1hcGzoBq AC1kmTcJoN0NnhlREk6iO5/wwVZSBsakfsZ2JpTPViBU7sCYJzoQ1z5jA+RwFMeNecVx NFmy04+fRXRDHbZFKRWQDNbyuaGBSTGnZ9r9WMNSAOZr3o93bJwSjWG4yQIDAp4MoW7x WC6g== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-transfer-encoding:mime-version :references:in-reply-to:message-id:date:subject:cc:to:from; bh=zN10YoBmdyn9xQvL7aOxQFMRVcKcxvXRfHk7+REMr58=; b=LVpNvNHA//W1A12ZI0zBIBkKxOq3BLqRuWU8bbs2KQm9N7AfbaLUy7oExXt+UMcdrk 7X3XseOOIVpfBWjLzwTA5sjblV7YgLgnAO0akflaTBk++jnyhOvm60EMubeDfdYU0C0V FHedzz0ta2R126IaJj4OTm9/4NZol/zIforisUdr2dFJIx6+q+6v07vLEr582+3Vx4qS 4Sj2kalcb0sNG3hTRWTYgSmLk+UIykqUTQNdupi1nXOcNwIn4/9WeFMQRt+GGvOYFCZY ZOvglmu9r5PQU5Mg+ZvPTCX0T9isXm/nqNas7Bua7ZlimDZpRVtGNLW0Ddwp6AsHlhYS GBSw== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: from out1.vger.email (out1.vger.email. [2620:137:e000::1:20]) by mx.google.com with ESMTP id un2-20020a170907cb8200b007c1745249a1si9456251ejc.944.2022.12.27.04.38.24; Tue, 27 Dec 2022 04:38:55 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230092AbiL0Mep (ORCPT + 99 others); Tue, 27 Dec 2022 07:34:45 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42028 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229682AbiL0Mek (ORCPT ); Tue, 27 Dec 2022 07:34:40 -0500 Received: from dggsgout12.his.huawei.com (unknown [45.249.212.56]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9FECEB2C; Tue, 27 Dec 2022 04:34:39 -0800 (PST) Received: from mail02.huawei.com (unknown [172.30.67.153]) by dggsgout12.his.huawei.com (SkyGuard) with ESMTP id 4NhDcS0VQDz4f3kpQ; Tue, 27 Dec 2022 20:34:32 +0800 (CST) Received: from huaweicloud.com (unknown [10.175.127.227]) by APP4 (Coremail) with SMTP id gCh0CgAHvbBZ5qpjAnByAg--.34791S6; Tue, 27 Dec 2022 20:34:34 +0800 (CST) From: Yu Kuai To: tj@kernel.org, hch@infradead.org, josef@toxicpanda.com, axboe@kernel.dk Cc: cgroups@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, yukuai3@huawei.com, yukuai1@huaweicloud.com, yi.zhang@huawei.com Subject: [PATCH v2 2/2] blk-iocost: add refcounting for ioc Date: Tue, 27 Dec 2022 20:55:02 +0800 Message-Id: <20221227125502.541931-3-yukuai1@huaweicloud.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20221227125502.541931-1-yukuai1@huaweicloud.com> References: <20221227125502.541931-1-yukuai1@huaweicloud.com> MIME-Version: 1.0 X-CM-TRANSID: gCh0CgAHvbBZ5qpjAnByAg--.34791S6 X-Coremail-Antispam: 1UD129KBjvJXoWxGF1fWrW5KFWUuFW3GF1xKrg_yoWrAw48pF 43W3s8C3ykWrnruwsxJF4xtryrAayY9w1xurs3Grna9F13X3s0q3WkAryjgFy5WFZxXrW3 ZF1vgrW5JF4j9w7anT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUBE14x267AKxVWrJVCq3wAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2048vs2IY020E87I2jVAFwI0_Jryl82xGYIkIc2 x26xkF7I0E14v26r4j6ryUM28lY4IEw2IIxxk0rwA2F7IY1VAKz4vEj48ve4kI8wA2z4x0 Y4vE2Ix0cI8IcVAFwI0_tr0E3s1l84ACjcxK6xIIjxv20xvEc7CjxVAFwI0_Gr1j6F4UJw A2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xvwVC2z280aVCY1x0267AKxVW0oVCq3wAS 0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFcxC0VAKzVAqx4xG6I80ewAv7VC0I7IYx2 IY67AKxVWUGVWUXwAv7VC2z280aVAFwI0_Jr0_Gr1lOx8S6xCaFVCjc4AY6r1j6r4UM4x0 Y48IcxkI7VAKI48JM4x0x7Aq67IIx4CEVc8vx2IErcIFxwACI402YVCY1x02628vn2kIc2 xKxwCF04k20xvY0x0EwIxGrwCFx2IqxVCFs4IE7xkEbVWUJVW8JwC20s026c02F40E14v2 6r1j6r18MI8I3I0E7480Y4vE14v26r106r1rMI8E67AF67kF1VAFwI0_Jw0_GFylIxkGc2 Ij64vIr41lIxAIcVC0I7IYx2IY67AKxVWUJVWUCwCI42IY6xIIjxv20xvEc7CjxVAFwI0_ Gr0_Cr1lIxAIcVCF04k26cxKx2IYs7xG6r1j6r1xMIIF0xvEx4A2jsIE14v26r1j6r4UMI IF0xvEx4A2jsIEc7CjxVAFwI0_Gr0_Gr1UYxBIdaVFxhVjvjDU0xZFpf9x0JUfwIDUUUUU = X-CM-SenderInfo: 51xn3trlr6x35dzhxuhorxvhhfrp/ X-CFilter-Loop: Reflected X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,SPF_HELO_NONE, SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1753370838682942174?= X-GMAIL-MSGID: =?utf-8?q?1753370838682942174?= From: Yu Kuai Our test found the following problem in kernel 5.10, and the same problem should exist in mainline: BUG: KASAN: use-after-free in _raw_spin_lock_irqsave+0x71/0xe0 Write of size 4 at addr ffff8881432000e0 by task swapper/4/0 ... Call Trace: dump_stack+0x9c/0xd3 print_address_description.constprop.0+0x19/0x170 __kasan_report.cold+0x6c/0x84 kasan_report+0x3a/0x50 check_memory_region+0xfd/0x1f0 _raw_spin_lock_irqsave+0x71/0xe0 ioc_pd_free+0x9d/0x250 blkg_free.part.0+0x80/0x100 __blkg_release+0xf3/0x1c0 rcu_do_batch+0x292/0x700 rcu_core+0x270/0x2d0 __do_softirq+0xfd/0x402 asm_call_irq_on_stack+0x12/0x20 do_softirq_own_stack+0x37/0x50 irq_exit_rcu+0x134/0x1a0 sysvec_apic_timer_interrupt+0x36/0x80 asm_sysvec_apic_timer_interrupt+0x12/0x20 Freed by task 57: kfree+0xba/0x680 rq_qos_exit+0x5a/0x80 blk_cleanup_queue+0xce/0x1a0 virtblk_remove+0x77/0x130 [virtio_blk] virtio_dev_remove+0x56/0xe0 __device_release_driver+0x2ba/0x450 device_release_driver+0x29/0x40 bus_remove_device+0x1d8/0x2c0 device_del+0x333/0x7e0 device_unregister+0x27/0x90 unregister_virtio_device+0x22/0x40 virtio_pci_remove+0x53/0xb0 pci_device_remove+0x7a/0x130 __device_release_driver+0x2ba/0x450 device_release_driver+0x29/0x40 pci_stop_bus_device+0xcf/0x100 pci_stop_and_remove_bus_device+0x16/0x20 disable_slot+0xa1/0x110 acpiphp_disable_and_eject_slot+0x35/0xe0 hotplug_event+0x1b8/0x3c0 acpiphp_hotplug_notify+0x37/0x70 acpi_device_hotplug+0xee/0x320 acpi_hotplug_work_fn+0x69/0x80 process_one_work+0x3c5/0x730 worker_thread+0x93/0x650 kthread+0x1ba/0x210 ret_from_fork+0x22/0x30 Root cause is that blkg_free() can be asynchronously, and it can race with delete device: T1 T2 T3 //delete device del_gendisk bdi_unregister bdi_remove_from_list synchronize_rcu_expedited //rmdir cgroup blkcg_destroy_blkgs blkg_destroy percpu_ref_kill blkg_release call_rcu rq_qos_exit ioc_rqos_exit kfree(ioc) __blkg_release blkg_free blkg_free_workfn pd_free_fn ioc_pd_free spin_lock_irqsave Fix the problem by add refcounting for ioc, and iocg will grab reference of ioc, so that ioc won't be freed until all the iocg is exited. Signed-off-by: Yu Kuai --- block/blk-iocost.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/block/blk-iocost.c b/block/blk-iocost.c index 525e93e1175a..d168d3f5f78e 100644 --- a/block/blk-iocost.c +++ b/block/blk-iocost.c @@ -404,6 +404,7 @@ struct ioc_pcpu_stat { struct ioc { struct rq_qos rqos; + refcount_t ref; bool enabled; struct ioc_params params; @@ -2816,6 +2817,12 @@ static void ioc_rqos_queue_depth_changed(struct rq_qos *rqos) spin_unlock_irq(&ioc->lock); } +static void ioc_put(struct ioc *ioc) +{ + if (refcount_dec_and_test(&ioc->ref)) + kfree(ioc); +} + static void ioc_rqos_exit(struct rq_qos *rqos) { struct ioc *ioc = rqos_to_ioc(rqos); @@ -2828,7 +2835,7 @@ static void ioc_rqos_exit(struct rq_qos *rqos) del_timer_sync(&ioc->timer); free_percpu(ioc->pcpu_stat); - kfree(ioc); + ioc_put(ioc); } static struct rq_qos_ops ioc_rqos_ops = { @@ -2883,6 +2890,7 @@ static int blk_iocost_init(struct gendisk *disk) ioc->period_at = ktime_to_us(ktime_get()); atomic64_set(&ioc->cur_period, 0); atomic_set(&ioc->hweight_gen, 0); + refcount_set(&ioc->ref, 1); spin_lock_irq(&ioc->lock); ioc->autop_idx = AUTOP_INVALID; @@ -2983,6 +2991,7 @@ static void iocg_put(struct ioc_gq *iocg) spin_unlock_irqrestore(&ioc->lock, flags); hrtimer_cancel(&iocg->waitq_timer); + ioc_put(ioc); } free_percpu(iocg->pcpu_stat); @@ -3004,6 +3013,7 @@ static void ioc_pd_init(struct blkg_policy_data *pd) ioc_now(ioc, &now); iocg->ioc = ioc; + refcount_inc(&ioc->ref); atomic64_set(&iocg->vtime, now.vnow); atomic64_set(&iocg->done_vtime, now.vnow); atomic64_set(&iocg->active_period, atomic64_read(&ioc->cur_period));