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From: Rabin Vincent <rabin@rab.in>
To: Jan Kara <jack@suse.cz>
Cc: Rabin Vincent <rabin.vincent@axis.com>,
	viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org,
	linux-kernel@vger.kernel.org, axboe@kernel.dk, hch@lst.de
Subject: Re: [PATCH] block: protect iterate_bdevs() against concurrent close
Date: Mon, 14 Mar 2016 18:42:58 +0100	[thread overview]
Message-ID: <20160314174258.GA16571@debian> (raw)
In-Reply-To: <20160310173727.GA19795@quack.suse.cz>

(fixed Jens' address)

On Thu, Mar 10, 2016 at 06:37:27PM +0100, Jan Kara wrote:
> On Thu 10-03-16 13:26:03, Rabin Vincent wrote:
> > If a block device is closed while iterate_bdevs() is handling it, the
> > following NULL pointer dereference occurs because bdev->b_disk is NULL
> > in bdev_get_queue(), which is called from blk_get_backing_dev_info() (in
> > turn called by the mapping_cap_writeback_dirty() call in
> > __filemap_fdatawrite_range()):
> 
> Thanks for spotting the problem. The patch will fix the problem you
> found.  But what prevents e.g. flusher thread from trying to writeback
> the block device inode while that gets invalidated at the same moment?

Don't the sync_block_dev() / bdev_write_inode() calls in __blkdev_put()
prevent this?

  reply	other threads:[~2016-03-14 17:43 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-03-10 12:26 [PATCH] block: protect iterate_bdevs() against concurrent close Rabin Vincent
2016-03-10 17:37 ` Jan Kara
2016-03-14 17:42   ` Rabin Vincent [this message]
2016-03-15  8:23     ` Jan Kara
2016-03-15  7:51   ` Christoph Hellwig

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