Re: [PATCH v2 2/4] mm: change to return bool for isolate_lru_page()

[Baolin Wang]

On 2/15/2023 3:32 AM, SeongJae Park wrote:
> On Tue, 14 Feb 2023 21:59:30 +0800 Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx> wrote:
>
> > The isolate_lru_page() can only return 0 or -EBUSY, and most users did
> > not care about the negative error of isolate_lru_page(), except one user
> > in add_page_for_migration(). So we can convert the isolate_lru_page() to
> > return a boolean value, which can help to make the code more clear when
> > checking the return value of isolate_lru_page().
> >
> > Also convert all users' logic of checking the isolation state.
> >
> > No functional changes intended.
> >
> > Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
> > ---
> >   mm/folio-compat.c   | 12 +++---------
> >   mm/internal.h       |  2 +-
> >   mm/khugepaged.c     |  2 +-
> >   mm/memcontrol.c     |  4 ++--
> >   mm/memory-failure.c |  4 ++--
> >   mm/memory_hotplug.c |  2 +-
> >   mm/migrate.c        |  9 ++++++---
> >   mm/migrate_device.c |  2 +-
> >   8 files changed, 17 insertions(+), 20 deletions(-)
> [...]
> > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> > index a1e8c3e9ab08..17ed80707518 100644
> > --- a/mm/memory_hotplug.c
> > +++ b/mm/memory_hotplug.c
> > @@ -1668,7 +1668,7 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
> >   		 * LRU and non-lru movable pages.
> >   		 */
> >   		if (PageLRU(page))
> > -			ret = isolate_lru_page(page);
> > +			ret = !isolate_lru_page(page);
>
> This may change return value of this function.  That is, this function will
> return 1 instead of -EBUSY after this change.  It's not a real issue as no
> caller of this function takes care of the return value, though.

Yes, I've also thought about this. OK, I can keep the original logic 
here by adding a new variable. Thanks.

isolated = isolate_lru_page(page);
ret = isolated ? 0 : -EBUSY;