linux-kernel - Re: [PATCH] [10/16] POISON: Use bitmask/action code for try_to

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Message-ID: <alpine.DEB.1.10.0904071714450.12192@qirst.com>
Date:	Tue, 7 Apr 2009 17:19:19 -0400 (EDT)
From:	Christoph Lameter <cl@...ux.com>
To:	Andi Kleen <andi@...stfloor.org>
cc:	Lee.Schermerhorn@...com, npiggin@...e.de,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org, x86@...nel.org
Subject: Re: [PATCH] [10/16] POISON: Use bitmask/action code for try_to_unmap
 behaviour

On Tue, 7 Apr 2009, Andi Kleen wrote:

> +
> +enum ttu_flags {
> +	TTU_UNMAP = 0,			/* unmap mode */
> +	TTU_MIGRATION = 1,		/* migration mode */
> +	TTU_MUNLOCK = 2,		/* munlock mode */
> +	TTU_ACTION_MASK = 0xff,
> +
> +	TTU_IGNORE_MLOCK = (1 << 8),	/* ignore mlock */


Ignoring MLOCK? This means we are violating POSIX which says that an
MLOCKed page cannot be unmapped from a process? Note that page migration
does this under special pte entries so that the page will never appear to
be unmapped to user space.

How does that work for the poisoning case? We substitute a fresh page?

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