linux-kernel - Re: [PATCH 1/X] uprobes: write_opcode: the new page needs PG

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Date:	Mon, 17 Oct 2011 16:29:54 +0530
From:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...e.hu>,
	Steven Rostedt <rostedt@...dmis.org>,
	Linux-mm <linux-mm@...ck.org>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jonathan Corbet <corbet@....net>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Hugh Dickins <hughd@...gle.com>,
	Christoph Hellwig <hch@...radead.org>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andi Kleen <andi@...stfloor.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jim Keniston <jkenisto@...ux.vnet.ibm.com>,
	Roland McGrath <roland@...k.frob.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/X] uprobes: write_opcode: the new page needs
 PG_uptodate

* Oleg Nesterov <oleg@...hat.com> [2011-10-15 21:00:37]:

> write_opcode()->__replace_page() installs the new anonymous page,
> this new_page is PageSwapBacked() and it can be swapped out.
> 
> However it forgets to do SetPageUptodate(), fix write_opcode().
> 
> For example, this is needed if do_swap_page() finds that orginial
> page in the the swap cache (and doesn't try to read it back), in
> this case it returns VM_FAULT_SIGBUS.
> ---
>  kernel/uprobes.c |    2 ++
>  1 files changed, 2 insertions(+), 0 deletions(-)
> 
> diff --git a/kernel/uprobes.c b/kernel/uprobes.c
> index 3928bcc..52b20c8 100644
> --- a/kernel/uprobes.c
> +++ b/kernel/uprobes.c
> @@ -200,6 +200,8 @@ static int write_opcode(struct task_struct *tsk, struct uprobe * uprobe,
>  		goto put_out;
>  	}
> 
> +	__SetPageUptodate(new_page);
> +

Agree. 

>  	/*
>  	 * lock page will serialize against do_wp_page()'s
>  	 * PageAnon() handling

-- 
Thanks and Regards
Srikar

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