linux-kernel - Re: [PATCH v2 4/5] uprobes: cleanup and document write_opcode()->lock_page(old

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Date:	Mon, 9 Jul 2012 15:59:22 +0530
From:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Peter Zijlstra <peterz@...radead.org>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Anton Arapov <anton@...hat.com>,
	Hugh Dickins <hughd@...gle.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 4/5] uprobes: cleanup and document
 write_opcode()->lock_page(old_page)

* Oleg Nesterov <oleg@...hat.com> [2012-06-24 17:00:53]:

> The comment above write_opcode()->lock_page(old_page) tells about
> the race with do_wp_page(). I don't really understand which exactly
> race it means, but afaics this lock_page() was not enough to close
> all races with do_wp_page().
> 
> Anyway, since 77fc4af1 this code is always called with ->mmap_sem
> hold for writing so we can forget about do_wp_page().
> 
> However, we can't simply remove this lock_page(), and the only
> (afaics) reason is __replace_page()->try_to_free_swap().
> 
> Nothing in write_opcode() needs it, move it into __replace_page()
> and fix the comment.
> 
> Signed-off-by: Oleg Nesterov <oleg@...hat.com>

Acked-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>

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