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

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Message-ID: <4DC8ECDC.5080106@kernel.dk>
Date:	Tue, 10 May 2011 09:44:28 +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 2011-05-10 08:42, Amit Shah wrote:
> On (Fri) 29 Apr 2011 [10:15:50], Jens Axboe wrote:
>> 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.
> 
> Ping again.  Don't see this yet in Linus's git tree.

It was added for 2.6.40 and marked for stable.

-- 
Jens Axboe

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