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Subject: Re: [PATCH 2/3] block: fix locking for struct block_device size
 updates
To:     Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>
Cc:     Justin Sanders <justin@coraid.com>,
        Josef Bacik <josef@toxicpanda.com>,
        Xianting Tian <xianting_tian@126.com>,
        linux-block@vger.kernel.org, dm-devel@redhat.com,
        Stefan Haberland <sth@linux.ibm.com>,
        Jan Hoeppner <hoeppner@linux.ibm.com>,
        linux-kernel@vger.kernel.org, nbd@other.debian.org,
        linux-nvme@lists.infradead.org, linux-s390@vger.kernel.org
References: <20200823091043.2600261-1-hch@lst.de>
 <20200823091043.2600261-3-hch@lst.de>
From:   Hannes Reinecke <hare@suse.de>
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Message-ID: <73653f9e-2d39-48fb-9842-3a1851fb5bed@suse.de>
Date:   Mon, 24 Aug 2020 09:36:38 +0200
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On 8/23/20 11:10 AM, Christoph Hellwig wrote:
> Two different callers use two different mutexes for updating the
> block device size, which obviously doesn't help to actually protect
> against concurrent updates from the different callers.  In addition
> one of the locks, bd_mutex is rather prone to deadlocks with other
> parts of the block stack that use it for high level synchronization.
> 
> Switch to using a new spinlock protecting just the size updates, as
> that is all we need, and make sure everyone does the update through
> the proper helper.
> 
> This fixes a bug reported with the nvme revalidating disks during a
> hot removal operation, which can currently deadlock on bd_mutex.
> 
> Reported-by: Xianting Tian <xianting_tian@126.com>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  block/partitions/core.c         |  4 ++--
>  drivers/block/aoe/aoecmd.c      |  4 +---
>  drivers/md/dm.c                 | 15 ++-------------
>  drivers/s390/block/dasd_ioctl.c |  9 ++-------
>  fs/block_dev.c                  | 25 ++++++++++++++-----------
>  include/linux/blk_types.h       |  1 +
>  6 files changed, 22 insertions(+), 36 deletions(-)
> Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		           Kernel Storage Architect
hare@suse.de			                  +49 911 74053 688
SUSE Software Solutions Germany GmbH, Maxfeldstr. 5, 90409 Nürnberg
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