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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 177C5C2BB85 for ; Thu, 16 Apr 2020 08:37:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F01A32063A for ; Thu, 16 Apr 2020 08:37:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2441436AbgDPIhX (ORCPT ); Thu, 16 Apr 2020 04:37:23 -0400 Received: from szxga04-in.huawei.com ([45.249.212.190]:2381 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2502445AbgDPIe2 (ORCPT ); Thu, 16 Apr 2020 04:34:28 -0400 Received: from DGGEMS404-HUB.china.huawei.com (unknown [172.30.72.58]) by Forcepoint Email with ESMTP id D4369D718DC70E64E64B; Thu, 16 Apr 2020 16:34:17 +0800 (CST) Received: from [10.166.215.172] (10.166.215.172) by DGGEMS404-HUB.china.huawei.com (10.3.19.204) with Microsoft SMTP Server id 14.3.487.0; Thu, 16 Apr 2020 16:34:14 +0800 Subject: Re: [PATCH 3/8] bdi: add a ->dev_name field to struct backing_dev_info To: Christoph Hellwig , CC: , , , , , , References: <20200416071519.807660-1-hch@lst.de> <20200416071519.807660-4-hch@lst.de> From: Yufen Yu Message-ID: <5bfcd35a-2463-3769-be93-911c4e3c38bb@huawei.com> Date: Thu, 16 Apr 2020 16:34:13 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:68.0) Gecko/20100101 Thunderbird/68.3.1 MIME-Version: 1.0 In-Reply-To: <20200416071519.807660-4-hch@lst.de> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.166.215.172] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 2020/4/16 15:15, Christoph Hellwig wrote: > Cache a copy of the name for the life time of the backing_dev_info > structure so that we can reference it even after unregistering. > > Fixes: 68f23b89067f ("memcg: fix a crash in wb_workfn when a device disappears") > Reported-by: Yufen Yu > Signed-off-by: Christoph Hellwig > --- > include/linux/backing-dev-defs.h | 1 + > mm/backing-dev.c | 13 ++++++++++--- > 2 files changed, 11 insertions(+), 3 deletions(-) > > diff --git a/include/linux/backing-dev-defs.h b/include/linux/backing-dev-defs.h > index 4fc87dee005a..249590bcccf7 100644 > --- a/include/linux/backing-dev-defs.h > +++ b/include/linux/backing-dev-defs.h > @@ -220,6 +220,7 @@ struct backing_dev_info { > wait_queue_head_t wb_waitq; > > struct device *dev; > + const char *dev_name; > struct device *owner; > > struct timer_list laptop_mode_wb_timer; > diff --git a/mm/backing-dev.c b/mm/backing-dev.c > index c2c44c89ee5d..4f6c05df72f9 100644 > --- a/mm/backing-dev.c > +++ b/mm/backing-dev.c > @@ -938,9 +938,15 @@ int bdi_register_va(struct backing_dev_info *bdi, const char *fmt, va_list args) > if (bdi->dev) /* The driver needs to use separate queues per device */ > return 0; > > - dev = device_create_vargs(bdi_class, NULL, MKDEV(0, 0), bdi, fmt, args); > - if (IS_ERR(dev)) > + bdi->dev_name = kvasprintf(GFP_KERNEL, fmt, args); > + if (!bdi->dev_name) > + return -ENOMEM; > + > + dev = device_create(bdi_class, NULL, MKDEV(0, 0), bdi, bdi->dev_name); > + if (IS_ERR(dev)) { > + kfree(bdi->dev_name); > return PTR_ERR(dev); > + } > > cgwb_bdi_register(bdi); > bdi->dev = dev; > @@ -1034,6 +1040,7 @@ static void release_bdi(struct kref *ref) > WARN_ON_ONCE(bdi->dev); > wb_exit(&bdi->wb); > cgwb_bdi_exit(bdi); > + kfree(bdi->dev_name); > kfree(bdi); > } When driver try to to re-register bdi but without release_bdi(), the old dev_name will be cover directly by the newer in bdi_register_va(). So, I am not sure whether it can cause memory leak for bdi->dev_name. Thanks, Yufen > > @@ -1047,7 +1054,7 @@ const char *bdi_dev_name(struct backing_dev_info *bdi) > { > if (!bdi || !bdi->dev) > return bdi_unknown_name; > - return dev_name(bdi->dev); > + return bdi->dev_name; > } > EXPORT_SYMBOL_GPL(bdi_dev_name);