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Date:   Thu, 23 Apr 2020 13:07:38 +0200
From:   Michal =?iso-8859-1?Q?Koutn=FD?= <mkoutny@suse.com>
To:     Christoph Hellwig <hch@lst.de>
Cc:     Qian Cai <cai@lca.pw>, Jens Axboe <axboe@kernel.dk>,
        Heiko Carstens <heiko.carstens@de.ibm.com>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Christian Borntraeger <borntraeger@de.ibm.com>,
        linux-block@vger.kernel.org, linux-s390@vger.kernel.org,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: s390 boot woe due to "block: fix busy device checking in
 blk_drop_partitions"
Message-ID: <20200423110738.GA102241@blackbook>
References: <AD16A450-794F-4EEA-A7BF-42452F18294A@lca.pw>
 <20200410054544.GA17923@lst.de>
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Hi.

On Fri, Apr 10, 2020 at 07:45:44AM +0200, Christoph Hellwig <hch@lst.de> wrote:
> @@ -496,7 +496,7 @@ int blk_drop_partitions(struct gendisk *disk, struct block_device *bdev)
> -	if (bdev->bd_part_count || bdev->bd_openers)
> +	if (bdev->bd_part_count || bdev->bd_openers > 1)
>  		return -EBUSY;
I noticed this (and the previous patch) change unmasks race between
ioctl(LOOP_SET_STATUS64, ... lo_flags=LO_FLAGS_PARTSCAN ...) and udev
processing loop device uevents. See [1] for details.

Should the condition be changed in the case of newly setup loop devices?
(Or shouldn't the ioctl propagate EBUSY in its return value?)

Thanks,
Michal

[1] https://bugzilla.opensuse.org/show_bug.cgi?id=1169932

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