linux-kernel - Re: [PATCH] sr: Ensure disk is revalidated when media changes

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Message-ID: <20110408162041.GB3871@mtj.dyndns.org>
Date:	Fri, 8 Apr 2011 09:20:41 -0700
From:	Tejun Heo <tj@...nel.org>
To:	Stefan Hajnoczi <stefanha@...il.com>
Cc:	Amit Shah <amit.shah@...hat.com>, linux-kernel@...r.kernel.org,
	Jens Axboe <axboe@...nel.dk>,
	"James E.J. Bottomley" <James.Bottomley@...e.de>,
	linux-scsi@...r.kernel.org, Markus Armbruster <armbru@...hat.com>
Subject: Re: [PATCH] sr: Ensure disk is revalidated when media changes

Hello,

On Fri, Apr 08, 2011 at 12:37:56PM +0100, Stefan Hajnoczi wrote:
> There is a related issue I have been discussing with Amit:
> https://lkml.org/lkml/2011/3/23/156
> 
> On media change the inode size is not updated by the sr driver or the
> universal cdrom driver.  A userspace process that holds a /dev/sr0
> file descriptor open across media change causes all processes on the
> system to see the old medium size when they do lseek(fd, 0, SEEK_END).
> 
> I think it would make sense to refresh the inode size on media change
> so that even open file descriptors see the new size and a single
> process cannot force a stale value for all other userspace processes
> on the system.

Hmmm... I don't know.  Maybe we can but I'm not sure whether there's a
good reason for it.  cdrom is locked while opened after all.  Are
there actual problems?

Thanks.

-- 
tejun
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