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

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Date:	Tue, 10 May 2011 13:43:53 +0530
From:	Amit Shah <amit.shah@...hat.com>
To:	Jens Axboe <axboe@...nel.dk>
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 (Tue) 10 May 2011 [09:44:28], Jens Axboe wrote:
> 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.

OK, Thanks.

		Amit
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