From: Tejun Heo <tj@kernel.org>
To: Jan Kara <jack@suse.cz>
Cc: Wei Fang <fangwei1@huawei.com>,
akpm@linux-foundation.org, hannes@cmpxchg.org, hch@infradead.org,
linux-mm@kvack.org, stable@vger.kernel.org,
Jens Axboe <axboe@kernel.dk>
Subject: Re: [PATCH] mm: Fix a NULL dereference crash while accessing bdev->bd_disk
Date: Mon, 28 Nov 2016 10:57:18 -0500 [thread overview]
Message-ID: <20161128155718.GB7806@htj.duckdns.org> (raw)
In-Reply-To: <20161128100718.GD2590@quack2.suse.cz>
Hello, Jan.
On Mon, Nov 28, 2016 at 11:07:18AM +0100, Jan Kara wrote:
> As I'm looking into the code, we need a serialization between bdev writeback
> and blkdev_put(). That should be doable if we use writeback_single_inode()
> for writing bdev inode instead of simple filemap_fdatawrite() and then use
> inode_wait_for_writeback() in blkdev_put() but it needs some careful
> thought.
It's kinda weird that sync() is ends up accessing bdev's without any
synchronization. Can't we just make iterate_bdevs() grab bd_mutex and
verify bd_disk isn't NULL before calling into the callback?
> Frankly that whole idea of tearing block devices down on last close is a
> major headache and keeps biting us. I'm wondering whether it is still worth
> it these days...
Yeah, it'd be great if we can follow a more conventional lifetime
pattern here.
Thanks.
--
tejun
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next prev parent reply other threads:[~2016-11-28 15:57 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-26 2:06 Wei Fang
2016-11-28 10:07 ` Jan Kara
2016-11-28 15:57 ` Tejun Heo [this message]
2016-11-29 9:30 ` Jan Kara
2016-11-29 16:43 ` Tejun Heo
2016-11-30 9:50 ` Jan Kara
2016-11-29 1:58 ` Wei Fang
2016-11-30 9:51 ` Jan Kara
2016-12-01 2:30 ` Wei Fang
2016-12-01 8:18 ` Jan Kara
2016-11-29 23:08 ` Andrew Morton
2016-11-30 7:30 ` Jan Kara
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