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SubjectRe: [RFC] mm: support MIGRATE_DISCARD
Hi Rik,

On Fri, Aug 24, 2012 at 11:04:16AM -0400, Rik van Riel wrote:
> On 08/24/2012 12:25 AM, Minchan Kim wrote:
> >This patch introudes MIGRATE_DISCARD mode in migration.
> >It drops *unmapped clean cache pages* instead of migration so that
>
> Am I confused, or does the code not match the changelog?
>
> It looks like it is still trying to discard mapped page cache pages:

Embarrassing typo :( "clean cache page" is right.
That includes both mapped/unmapped clean cache pages.

>
> >+ file = page_is_file_cache(page);
> >+ ttu_flags = TTU_IGNORE_ACCESS;
> >+retry:
> >+ if (!(mode & MIGRATE_DISCARD) || !file || PageDirty(page))
> >+ ttu_flags |= (TTU_MIGRATION | TTU_IGNORE_MLOCK);
> >+ else
> >+ discard_mode = true;
> >+
> > /* Establish migration ptes or remove ptes */
> >- try_to_unmap(page, TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
> >+ rc = try_to_unmap(page, ttu_flags);
> >
> > skip_unmap:
> >- if (!page_mapped(page))
> >- rc = move_to_new_page(newpage, page, remap_swapcache, mode);
> >+ if (rc == SWAP_SUCCESS) {
> >+ if (!discard_mode)
> >+ rc = move_to_new_page(newpage, page,
> >+ remap_swapcache, mode);
> >+ else {
> >+
> >+ rc = discard_page(page);
> >+ goto uncharge;
> >+ }
>
>
>
> --
> All rights reversed


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