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=-11.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 E3B70C43460 for ; Wed, 12 May 2021 07:23:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BE5076162B for ; Wed, 12 May 2021 07:23:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230109AbhELHYd (ORCPT ); Wed, 12 May 2021 03:24:33 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:32532 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229627AbhELHYc (ORCPT ); Wed, 12 May 2021 03:24:32 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1620804204; 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=vg/cll4jMfmP1m7tM5YSccYAw8vElQEoOqiM7v+Lw54=; b=gV1qTN5zBhJItWDz/uKryN2+6nh7Pwul7vRVlsSYzlH7U6Z3cFCoTDrg4bnKidFWHg5xfW ppZgh95wrdoms3JvmWeuGNN58S4bV22dH7MiJpxGL2q2h+srlYtAHB5R7ZK1IsrQpmBDzf 3PQpOZuZ+SJ3oMgNdScCmORsZnmPJXE= 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-593-FrlSMN87OIaCe4JumnKwJw-1; Wed, 12 May 2021 03:23:23 -0400 X-MC-Unique: FrlSMN87OIaCe4JumnKwJw-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 A38411854E26; Wed, 12 May 2021 07:23:21 +0000 (UTC) Received: from T590 (ovpn-13-214.pek2.redhat.com [10.72.13.214]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 1800114103; Wed, 12 May 2021 07:23:14 +0000 (UTC) Date: Wed, 12 May 2021 15:23:10 +0800 From: Ming Lei To: Christoph Hellwig Cc: Gulam Mohamed , viro@zeniv.linux.org.uk, axboe@kernel.dk, linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, martin.petersen@oracle.com, junxiao.bi@oracle.com Subject: Re: [PATCH V1 1/1] Fix race between iscsi logout and systemd-udevd Message-ID: References: <20210511181558.380764-1-gulam.mohamed@oracle.com> <20210512063505.GA18367@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210512063505.GA18367@lst.de> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Wed, May 12, 2021 at 08:35:05AM +0200, Christoph Hellwig wrote: > On Wed, May 12, 2021 at 11:23:59AM +0800, Ming Lei wrote: > > > > 1) code path BLKRRPART: > > mutex_lock(bdev->bd_mutex) > > down_read(&bdev_lookup_sem); > > > > 2) del_gendisk(): > > down_write(&bdev_lookup_sem); > > mutex_lock(&disk->part0->bd_mutex); > > > > Given GENHD_FL_UP is only checked when opening one bdev, and > > fsync_bdev() and __invalidate_device() needn't to open bdev, so > > the following way may work for your issue: > > If we move the clearing of GENHD_FL_UP earlier we can do away with > bdev_lookup_sem entirely I think. Something like this untested patch: > > diff --git a/block/genhd.c b/block/genhd.c > index a5847560719c..ef717084b343 100644 > --- a/block/genhd.c > +++ b/block/genhd.c > @@ -29,8 +29,6 @@ > > static struct kobject *block_depr; > > -DECLARE_RWSEM(bdev_lookup_sem); > - > /* for extended dynamic devt allocation, currently only one major is used */ > #define NR_EXT_DEVT (1 << MINORBITS) > static DEFINE_IDA(ext_devt_ida); > @@ -609,13 +607,8 @@ void del_gendisk(struct gendisk *disk) > blk_integrity_del(disk); > disk_del_events(disk); > > - /* > - * Block lookups of the disk until all bdevs are unhashed and the > - * disk is marked as dead (GENHD_FL_UP cleared). > - */ > - down_write(&bdev_lookup_sem); > - > mutex_lock(&disk->open_mutex); > + disk->flags &= ~GENHD_FL_UP; > blk_drop_partitions(disk); > mutex_unlock(&disk->open_mutex); > > @@ -627,10 +620,7 @@ void del_gendisk(struct gendisk *disk) > * up any more even if openers still hold references to it. > */ > remove_inode_hash(disk->part0->bd_inode); > - > set_capacity(disk, 0); > - disk->flags &= ~GENHD_FL_UP; > - up_write(&bdev_lookup_sem); > > if (!(disk->flags & GENHD_FL_HIDDEN)) { > sysfs_remove_link(&disk_to_dev(disk)->kobj, "bdi"); > diff --git a/fs/block_dev.c b/fs/block_dev.c > index 8dd8e2fd1401..bde23940190f 100644 > --- a/fs/block_dev.c > +++ b/fs/block_dev.c > @@ -1377,33 +1377,24 @@ struct block_device *blkdev_get_no_open(dev_t dev) > struct block_device *bdev; > struct gendisk *disk; > > - down_read(&bdev_lookup_sem); > bdev = bdget(dev); > if (!bdev) { > - up_read(&bdev_lookup_sem); > blk_request_module(dev); > - down_read(&bdev_lookup_sem); > - > bdev = bdget(dev); > if (!bdev) > - goto unlock; > + return NULL; > } > > disk = bdev->bd_disk; > if (!kobject_get_unless_zero(&disk_to_dev(disk)->kobj)) > goto bdput; > - if ((disk->flags & (GENHD_FL_UP | GENHD_FL_HIDDEN)) != GENHD_FL_UP) > - goto put_disk; > if (!try_module_get(bdev->bd_disk->fops->owner)) > goto put_disk; > - up_read(&bdev_lookup_sem); > return bdev; > put_disk: > put_disk(disk); > bdput: > bdput(bdev); > -unlock: > - up_read(&bdev_lookup_sem); > return NULL; > } > > @@ -1462,7 +1453,10 @@ struct block_device *blkdev_get_by_dev(dev_t dev, fmode_t mode, void *holder) > > disk_block_events(disk); > > + ret = -ENXIO; > mutex_lock(&disk->open_mutex); > + if ((disk->flags & (GENHD_FL_UP | GENHD_FL_HIDDEN)) != GENHD_FL_UP) > + goto abort_claiming; > if (bdev_is_partition(bdev)) > ret = blkdev_get_part(bdev, mode); > else This patch looks fine, and new openers can be prevented really with help of ->open_mutex. Thanks, Ming