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=-8.0 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no 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 27CABC07E96 for ; Thu, 8 Jul 2021 14:41:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1152B61625 for ; Thu, 8 Jul 2021 14:41:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231781AbhGHOoV (ORCPT ); Thu, 8 Jul 2021 10:44:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52092 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229738AbhGHOoU (ORCPT ); Thu, 8 Jul 2021 10:44:20 -0400 Received: from mail-qv1-xf2e.google.com (mail-qv1-xf2e.google.com [IPv6:2607:f8b0:4864:20::f2e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2E34FC061574 for ; Thu, 8 Jul 2021 07:41:38 -0700 (PDT) Received: by mail-qv1-xf2e.google.com with SMTP id v17so2890423qvw.12 for ; Thu, 08 Jul 2021 07:41:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=9OuGskVqA2qusAP0EWtWMxQD5LYCBw1WUf1Elc9qMZ0=; b=q9yEr1XkfLFq2WNWb//fqgYRseHjthIob6iCW5BLrBihWVxihn4suavcPiju0NvtcR BBvXE4CMvobC/U4bgkY47QW5odld6P9cjVncRWcO6+sonTGnDjrbMKxJXnTuvDBaIQJE SINXMexhzXc6KbzKLoi4iKmAoKgSxMDXYSImX47jlU0u/qTrbZ0kCyPuoi9zaavSE7nf xXdDbHXWbdJzRAETQkSceLj6W7e+oj94ZM5KhPpWDnCW6mvzlp2tBLFp0fDJ0cGdkvyo m4cCcfCLHLUXI1GISeSv8WqdRsuEofNYXeyyWAH9Zv1ZlqSOwa+1AwmaiFFtpvqE9LEj pXew== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=9OuGskVqA2qusAP0EWtWMxQD5LYCBw1WUf1Elc9qMZ0=; b=FH/RIAKtfYskjurIXZi7oHtTvdoNeCcK1uy7vNaMStI/uDkcRfS4E5B75kVdxKGZEz n7n9mLAhyBqcfwSMGx2uFZg/x64g6YZNaF4/eGDfy/asjDDcZI5/Jpmi/t2sEyFGrT8f Rd0dG6PztaskxKfT7IXwVk13b+rilDQvMfEw3ICbzoJDagCax9BVnaRvqJCX08+OeKs1 KMEnaJDdnf/uT/i7pwRDmVMCNxwqGTMsYQFLFV5oCRbziTRBZI0e7hsolpm/1INemBDF 2iWUQUyYkRJYOEnXO01PIerPNseUhZjgyR9+trz9NRYcOcSAlMufY85O6+a26NrDl2P1 d+rg== X-Gm-Message-State: AOAM532UrpEytQoH9X01ribCDtnoicJONfUOloT1dZp2r5jLSq+1mw9V wQSOgO0V9gkNJazgRWIxp3DICct06V0= X-Google-Smtp-Source: ABdhPJxImlYJbXtn1Gzxkylzgpwmg1UUFdqldqJfPhVGKQJXOwnCEUun503NriWSZaNhl9LcGdJhYQ== X-Received: by 2002:a0c:cb8f:: with SMTP id p15mr30828096qvk.13.1625755297290; Thu, 08 Jul 2021 07:41:37 -0700 (PDT) Received: from dschatzberg-fedora-PC0Y6AEN ([2620:10d:c091:480::1:ee15]) by smtp.gmail.com with ESMTPSA id p64sm1078876qka.114.2021.07.08.07.41.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 08 Jul 2021 07:41:36 -0700 (PDT) Date: Thu, 8 Jul 2021 10:41:34 -0400 From: Dan Schatzberg To: Ming Lei Cc: Jens Axboe , linux-block@vger.kernel.org, Christoph Hellwig , Michal =?iso-8859-1?Q?Koutn=FD?= Subject: Re: [PATCH 6/6] loop: don't add worker into idle list Message-ID: References: <20210705102607.127810-1-ming.lei@redhat.com> <20210705102607.127810-7-ming.lei@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Thu, Jul 08, 2021 at 02:58:36PM +0800, Ming Lei wrote: > diff --git a/drivers/block/loop.c b/drivers/block/loop.c > index 146eaa03629b..3cd51bddfec9 100644 > --- a/drivers/block/loop.c > +++ b/drivers/block/loop.c > @@ -980,7 +980,6 @@ static struct loop_worker *loop_alloc_or_get_worker(struct loop_device *lo, > > static void loop_release_worker(struct loop_worker *worker) > { > - xa_erase(&worker->lo->workers, worker->blkcg_css->id); > css_put(worker->blkcg_css); > kfree(worker); Another thought - do you need to change the kfree here to kfree_rcu? I'm concerned about the scenario where loop_queue_work's xa_load finds the worker and subsequently __loop_free_idle_workers erases and calls loop_release_worker. If the worker is freed then the subsequent refcount_inc_not_zero in loop_queue_work would be a use after free.