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SubjectRe: [PATCH 05/10] migrate: add hugepage migration code to migrate_pages()
On Tue 26-03-13 01:13:10, Naoya Horiguchi wrote:
> On Mon, Mar 25, 2013 at 02:04:16PM +0100, Michal Hocko wrote:
> > On Fri 22-03-13 16:23:50, Naoya Horiguchi wrote:
[...]
> > > @@ -1012,14 +1040,8 @@ static int migrate_to_node(struct mm_struct *mm, int source, int dest,
> > > check_range(mm, mm->mmap->vm_start, mm->task_size, &nmask,
> > > flags | MPOL_MF_DISCONTIG_OK, &pagelist);
> > >
> > > - if (!list_empty(&pagelist)) {
> > > - err = migrate_pages(&pagelist, new_node_page, dest,
> > > + return migrate_movable_pages(&pagelist, new_node_page, dest,
> > > MIGRATE_SYNC, MR_SYSCALL);
> > > - if (err)
> > > - putback_lru_pages(&pagelist);
> > > - }
> > > -
> > > - return err;
> >
> > This is really confusing. Why migrate_pages doesn't do putback cleanup
> > on its own but migrate_movable_pages does?
>
> I consider migrate_movable_pages() as a wrapper of migrate_pages(),
> not the variant of migrate_pages().

The naming suggests that this is the same functionality for a "different"
type of pages.

> We can find the same pattern in the callers like
>
> if (!list_empty(&pagelist)) {
> err = migrate_pages(...);
> if (err)
> putback_lru_pages(&pagelist);
> }
>
> , so it can be simplified by migrate_movable_pages().

I would rather see the same pattern for both. It could be error prone if

--
Michal Hocko
SUSE Labs


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