Re: [PATCH 4/9] mm/rmap: make rmap_walk to get thermap_walk_control argument

From: Andrew Morton
Date: Mon Dec 02 2013 - 17:53:07 EST


On Thu, 28 Nov 2013 16:48:41 +0900 Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> wrote:

> In each rmap traverse case, there is some difference so that we need
> function pointers and arguments to them in order to handle these
> difference properly.
>
> For this purpose, struct rmap_walk_control is introduced in this patch,
> and will be extended in following patch. Introducing and extending are
> separate, because it clarify changes.
>
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -198,7 +198,12 @@ out:
> */
> static void remove_migration_ptes(struct page *old, struct page *new)
> {
> - rmap_walk(new, remove_migration_pte, old);
> + struct rmap_walk_control rwc;
> +
> + memset(&rwc, 0, sizeof(rwc));
> + rwc.main = remove_migration_pte;
> + rwc.arg = old;
> + rmap_walk(new, &rwc);
> }

It is much neater to do

struct rmap_walk_control rwc = {
.main = remove_migration_pte,
.arg = old,
};

which will zero out all remaining fields as well.
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