Re: [PATCH v3 4/4] mm: change to return bool for isolate_movable_page()

[Baolin Wang]

On 2/15/2023 11:44 PM, Matthew Wilcox wrote:
> On Wed, Feb 15, 2023 at 06:39:37PM +0800, Baolin Wang wrote:
> > Now the isolate_movable_page() can only return 0 or -EBUSY, and no users
> > will care about the negative return value, thus we can convert the
> > isolate_movable_page() to return a boolean value to make the code more
> > clear when checking the movable page isolation state.
> >
> > No functional changes intended.
> >
> > Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
> > Acked-by: David Hildenbrand <david@xxxxxxxxxx>
>
> Reviewed-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
>
> A couple of nits below, not worth respinning the patch series for:
>
> > diff --git a/include/linux/migrate.h b/include/linux/migrate.h
> > index c88b96b48be7..6b252f519c86 100644
> > --- a/include/linux/migrate.h
> > +++ b/include/linux/migrate.h
> > @@ -71,7 +71,7 @@ extern int migrate_pages(struct list_head *l, new_page_t new, free_page_t free,
> >   		unsigned long private, enum migrate_mode mode, int reason,
> >   		unsigned int *ret_succeeded);
> >   extern struct page *alloc_migration_target(struct page *page, unsigned long private);
> > -extern int isolate_movable_page(struct page *page, isolate_mode_t mode);
> > +extern bool isolate_movable_page(struct page *page, isolate_mode_t mode);
>
> You can drop the 'extern' here.
>
> > +++ b/mm/memory_hotplug.c
> > @@ -1668,18 +1668,18 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
> >   		 * We can skip free pages. And we can deal with pages on
> >   		 * LRU and non-lru movable pages.
> >   		 */
> > -		if (PageLRU(page)) {
> > +		if (PageLRU(page))
> >   			isolated = isolate_lru_page(page);
> > -			ret = isolated ? 0 : -EBUSY;
> > -		} else
> > -			ret = isolate_movable_page(page, ISOLATE_UNEVICTABLE);
> > -		if (!ret) { /* Success */
> > +		else
> > +			isolated = isolate_movable_page(page, ISOLATE_UNEVICTABLE);
> > +		if (isolated) { /* Success */
>
> I would have dropped the "/* Success */" here.  Before, commenting
> "!ret" is quite sensible, but "isolated" seems obviously success to me.

Right. Hope Andrew can help to drop this unnecessary comment:)

Thanks for reviewing.