Re: [PATCH 1/4] mm/migrate: correct return value ofmigrate_pages()

[Christoph Lameter]

On Fri, 6 Dec 2013, Joonsoo Kim wrote:

> migrate_pages() should return number of pages not migrated or error code.
> When unmap_and_move return -EAGAIN, outer loop is re-execution without
> initialising nr_failed. This makes nr_failed over-counted.
>
> So this patch correct it by initialising nr_failed in outer loop.

Well nr_retry is the total number of attempts that got EGAIN. nr_failed is
the total number of failed attempts. You are making nr_failed the number
of pages of the list that have failed to migrated. That syncs with the
description.

> diff --git a/mm/migrate.c b/mm/migrate.c
> index 3747fcd..1f59ccc 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -1102,6 +1102,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
>
>  	for(pass = 0; pass < 10 && retry; pass++) {
>  		retry = 0;
> +		nr_failed = 0;

The initialization of nr_failed and retry earlier is then useless.

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