On Tue 26-03-13 00:34:40, Naoya Horiguchi wrote:
> On Mon, Mar 25, 2013 at 01:31:28PM +0100, Michal Hocko wrote:
> > On Fri 22-03-13 16:23:48, Naoya Horiguchi wrote:
[...]
> > > @@ -1482,12 +1483,20 @@ static int soft_offline_huge_page(struct page *page, int flags)
> > > unlock_page(hpage);
> > >
> > > /* Keep page count to indicate a given hugepage is isolated. */
> > > - ret = migrate_huge_page(hpage, new_page, MPOL_MF_MOVE_ALL,
> > > - MIGRATE_SYNC);
> > > - put_page(hpage);
> > > + list_move(&hpage->lru, &pagelist);
> > > + ret = migrate_pages(&pagelist, new_page, MPOL_MF_MOVE_ALL,
> > > + MIGRATE_SYNC, MR_MEMORY_FAILURE);
> > > if (ret) {
> > > pr_info("soft offline: %#lx: migration failed %d, type %lx\n",
> > > pfn, ret, page->flags);
> > > + /*
> > > + * We know that soft_offline_huge_page() tries to migrate
> > > + * only one hugepage pointed to by hpage, so we need not
> > > + * run through the pagelist here.
> > > + */
> > > + putback_active_hugepage(hpage);
> >
> > Maybe I am missing something but why we didn't need to call this before
> > when using migrate_huge_page?
>
> migrate_huge_page() does not need list handling before/after the call,
> because it's defined to migrate only one hugepage, and it has a page as
> an argument, not list_head.
I do not understand this reasoning. migrate_huge_page calls
unmap_and_move_huge_page and migrate_pages does the same + accounting.
So what is the difference here? I suspect that putback_active_hugepage
was simply missing in this code path.
> > > + if (ret > 0)
> > > + ret = -EIO;
> > > } else {
> > > set_page_hwpoison_huge_page(hpage);
> > > dequeue_hwpoisoned_huge_page(hpage);
> > > diff --git v3.9-rc3.orig/mm/migrate.c v3.9-rc3/mm/migrate.c
> > > index f69f354..66030b6 100644
> > > --- v3.9-rc3.orig/mm/migrate.c
> > > +++ v3.9-rc3/mm/migrate.c
> > > @@ -981,6 +981,8 @@ static int unmap_and_move_huge_page(new_page_t get_new_page,
> > >
> > > unlock_page(hpage);
> > > out:
> > > + if (rc != -EAGAIN)
> > > + putback_active_hugepage(hpage);
> >
> > And why do you put it here? If it is called from migrate_pages then the
> > caller already does the clean-up (putback_lru_pages).
>
> What the caller of migrate_pages() cleans up is the (huge)pages which failed
> to be migrated. And what the above code cleans up is the source hugepage
> after the migration succeeds.
Why should you want to add successfully migrated page? /me confused.
--
Michal Hocko
SUSE Labs
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