linux-kernel - Re: [PATCH] fbdefio: add set_page

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Date:	Wed, 20 Aug 2008 01:37:36 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Ian Campbell <ijc@...lion.org.uk>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	stable@...r.kernel.org, Jaya Kumar <jayakumar.lkml@...il.com>,
	Nick Piggin <npiggin@...e.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Hugh Dickins <hugh@...itas.com>,
	Johannes Weiner <hannes@...urebad.de>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Kel Modderman <kel@...ku42.de>,
	Markus Armbruster <armbru@...hat.com>
Subject: Re: [PATCH] fbdefio: add set_page_dirty handler to deferred IO FB

On Wed, 20 Aug 2008 09:13:23 +0100 Ian Campbell <ijc@...lion.org.uk> wrote:

> Perhaps applying the band-aid at open time instead would be preferred?

That would be less racy, I expect.  Implement fb_ops.fb_open() within
drivers/video/fb_defio.c and do the address_space_operations overwrite
there.  Hopefully that will ensure that the address_space_operations
instance is stable before anyone uses it for anything serious.

It'd be better to hook in at inode creation time but afaict that's not
available for the /dev/fb0 node.

<tries to write a patch>

OK, seems that fb_ops.fb_open() has no way of getting at the `struct
file *' which is being opened (wtf?).  Screwed.  Need to change
fb_ops.fb_open(), or add a new fb_ops.fb_open_sane().

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