linux-kernel - Re: [patch 1/4] mempolicy: convert MPOL constants to enum

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Message-ID: <Pine.LNX.4.64.0802121702431.11628@schroedinger.engr.sgi.com>
Date:	Tue, 12 Feb 2008 17:04:24 -0800 (PST)
From:	Christoph Lameter <clameter@....com>
To:	Paul Jackson <pj@....com>
cc:	Lee Schermerhorn <Lee.Schermerhorn@...com>, rientjes@...gle.com,
	akpm@...ux-foundation.org, ak@...e.de, linux-kernel@...r.kernel.org
Subject: Re: [patch 1/4] mempolicy: convert MPOL constants to enum

On Tue, 12 Feb 2008, Paul Jackson wrote:

> I'm inclined toward the original types for the 'policy' field.

Good. And remove the enum.

> Specifically, I'd suggest adding the one line for 'mode_f_static_nodes'
> as below, and leaving the code involving the encoding of the policy
> field alone.
> 
> struct mempolicy {
>         atomic_t refcnt;
>         short policy;   /* See MPOL_* above */
> 	int mode_f_static_nodes:1;			/* <== Added line <== */

It would be better to add some sort of flags field?

> Single bit fields (The ":1" above) provide the simplest way to add
> boolean flags to structs.  Let the compiler do the work of packing
> and unpacking the field.

We usually do that with unsigned XXX and constants. You may want to check 
multiple flags at once or do other fancy things.

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