linux-kernel - Re: [PATCH 1/2] cdrom: always check_disk

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Message-ID: <4DBA73B6.6040603@kernel.dk>
Date:	Fri, 29 Apr 2011 10:15:50 +0200
From:	Jens Axboe <axboe@...nel.dk>
To:	Amit Shah <amit.shah@...hat.com>
CC:	Tejun Heo <tj@...nel.org>, David Zeuthen <zeuthen@...il.com>,
	Martin Pitt <martin.pitt@...ntu.com>,
	Kay Sievers <kay.sievers@...y.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] cdrom: always check_disk_change() on open

On 2011-04-29 08:57, Amit Shah wrote:
> On (Wed) 06 Apr 2011 [05:20:09], Tejun Heo wrote:
>> cdrom_open() called check_disk_change() after the rest of open path
>> succeeded which leads to the following bizarre behavior.
>>
>> * After media change, if the device opened without O_NONBLOCK,
>>   open_for_data() naturally fails with -ENOMEDIA and
>>   check_disk_change() is never called.  The media is known to be gone
>>   and the open failure makes it obvious to the userland but device
>>   invalidation never happens.
>>
>> * But if the device is opened with O_NONBLOCK, all the checks are
>>   bypassed and cdrom_open() doesn't notice that the media is not there
>>   and check_disk_change() is called and invalidation happens.
>>
>> There's nothing to be gained by avoiding calling check_disk_change()
>> on open failure.  Common cases end up calling check_disk_change()
>> anyway.  All we get is inconsistent behavior.
>>
>> Fix it by moving check_disk_change() invocation to the top of
>> cdrom_open() so that it always gets called regardless of how the rest
>> of open proceeds.
>>
>> Signed-off-by: Tejun Heo <tj@...nel.org>
>> Reported-by: Amit Shah <amit.shah@...hat.com>
>> Tested-by: Amit Shah <amit.shah@...hat.com>
> 
> Ping?
> 
> Also, please mark this for stable-2.6.38.

Done, added for 2.6.39 and marked stable for 2.6.38.

-- 
Jens Axboe

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