Re: [PATCH 1/5] Swap Migration V5: LRU operations

[Magnus Damm <magnus.damm@gmail.com>]

On 11/1/05, Christoph Lameter <clameter@sgi.com> wrote:
[snip]
> +static inline int
> +__isolate_lru_page(struct zone *zone, struct page *page)
> +{
> +       if (TestClearPageLRU(page)) {
> +               if (get_page_testone(page)) {
> +                       /*
> +                        * It is being freed elsewhere
> +                        */
> +                       __put_page(page);
> +                       SetPageLRU(page);
> +                       return -ENOENT;

Ok, -ENOENT..

> -static int isolate_lru_pages(int nr_to_scan, struct list_head *src,
> -                            struct list_head *dst, int *scanned)
> +static int isolate_lru_pages(struct zone *zone, int nr_to_scan,
> +                            struct list_head *src, struct list_head *dst)
[snip]
> +               switch (__isolate_lru_page(zone, page)) {
> +               case 1:
> +                       /* Succeeded to isolate page */
>                         list_add(&page->lru, dst);
> -                       nr_taken++;
> +                       break;
> +               case -1:
> +                       /* Not possible to isolate */
> +                       list_move(&page->lru, src);
> +                       break;
> +               default:
> +                       BUG();

Huh, -1?

It looks like the V4 to V5 upgrade added -ENOENT as return value to
__isolate_lru_page(), but did not change the code in
isolate_lru_pages().

The fix for this is simple, but maybe something else needs to be
changed too or I'm misunderstanding what is happening here.

Andrew, this looks like a showstopper for 2.6.14-mm1.

/ magnus