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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C0C99C433FE for ; Thu, 14 Oct 2021 02:12:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A24FC6101A for ; Thu, 14 Oct 2021 02:12:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229878AbhJNCO0 (ORCPT ); Wed, 13 Oct 2021 22:14:26 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:38084 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229837AbhJNCOZ (ORCPT ); Wed, 13 Oct 2021 22:14:25 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1634177541; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=rKi/nC1vwY+bmICKgPE8kpfZB/d+Vx8FvEWoSRsnXMI=; b=AVD7qGDyCHvlgJZZKKDNX+zoUwszQylZbB/m6huaO8yNl5z/tcbGPXK4QeljMHKxhgSfVB D/ysHaRteemiI4c5cVVVFidtWWOBaJsqQK2ZAekhIa+uHDb0v+JEZy9a0V9/NyHzqTepfJ w9Y/UNsetRZ+a8Mx7Jg+OzNiDzZZkzc= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-497-aJwzUtPhPXmykCOmR_Jyfw-1; Wed, 13 Oct 2021 22:12:16 -0400 X-MC-Unique: aJwzUtPhPXmykCOmR_Jyfw-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 5163279EDD; Thu, 14 Oct 2021 02:12:13 +0000 (UTC) Received: from T590 (ovpn-8-18.pek2.redhat.com [10.72.8.18]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 47E042B0B2; Thu, 14 Oct 2021 02:11:50 +0000 (UTC) Date: Thu, 14 Oct 2021 10:11:46 +0800 From: Ming Lei To: Luis Chamberlain Cc: tj@kernel.org, gregkh@linuxfoundation.org, akpm@linux-foundation.org, minchan@kernel.org, jeyu@kernel.org, shuah@kernel.org, bvanassche@acm.org, dan.j.williams@intel.com, joe@perches.com, tglx@linutronix.de, keescook@chromium.org, rostedt@goodmis.org, linux-spdx@vger.kernel.org, linux-doc@vger.kernel.org, linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v8 11/12] zram: fix crashes with cpu hotplug multistate Message-ID: References: <20210927163805.808907-1-mcgrof@kernel.org> <20210927163805.808907-12-mcgrof@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Precedence: bulk List-ID: X-Mailing-List: linux-spdx@vger.kernel.org On Thu, Oct 14, 2021 at 09:55:48AM +0800, Ming Lei wrote: > On Mon, Sep 27, 2021 at 09:38:04AM -0700, Luis Chamberlain wrote: ... > > Hello Luis, > > Can you test the following patch and see if the issue can be addressed? > > Please see the idea from the inline comment. > > Also zram_index_mutex isn't needed in zram disk's store() compared with > your patch, then the deadlock issue you are addressing in this series can > be avoided. > > > diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c > index fcaf2750f68f..3c17927d23a7 100644 > --- a/drivers/block/zram/zram_drv.c > +++ b/drivers/block/zram/zram_drv.c > @@ -1985,11 +1985,17 @@ static int zram_remove(struct zram *zram) > > /* Make sure all the pending I/O are finished */ > fsync_bdev(bdev); > - zram_reset_device(zram); > > pr_info("Removed device: %s\n", zram->disk->disk_name); > > del_gendisk(zram->disk); > + > + /* > + * reset device after gendisk is removed, so any change from sysfs > + * store won't come in, then we can really reset device here > + */ > + zram_reset_device(zram); > + > blk_cleanup_disk(zram->disk); > kfree(zram); > return 0; > @@ -2073,7 +2079,12 @@ static int zram_remove_cb(int id, void *ptr, void *data) > static void destroy_devices(void) > { > class_unregister(&zram_control_class); > + > + /* hold the global lock so new device can't be added */ > + mutex_lock(&zram_index_mutex); > idr_for_each(&zram_index_idr, &zram_remove_cb, NULL); > + mutex_unlock(&zram_index_mutex); > + Actually zram_index_mutex isn't needed when calling zram_remove_cb() since the zram-control sysfs interface has been removed, so userspace can't add new device any more, then the issue is supposed to be fixed by the following one line change, please test it: diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index fcaf2750f68f..96dd641de233 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -1985,11 +1985,17 @@ static int zram_remove(struct zram *zram) /* Make sure all the pending I/O are finished */ fsync_bdev(bdev); - zram_reset_device(zram); pr_info("Removed device: %s\n", zram->disk->disk_name); del_gendisk(zram->disk); + + /* + * reset device after gendisk is removed, so any change from sysfs + * store won't come in, then we can really reset device here + */ + zram_reset_device(zram); + blk_cleanup_disk(zram->disk); kfree(zram); return 0; Thanks, Ming