Re: [PATCH v5 1/5] mm,page_alloc: Bail out earlier on -ENOMEM in alloc_contig_migrate_range

[Michal Hocko]

On Thu 18-03-21 12:04:00, Oscar Salvador wrote:
> On Wed, Mar 17, 2021 at 03:05:40PM +0100, Michal Hocko wrote:
> > That being said, bailing out early makes sense to me. But now that
> > you've made me look into the migrate_pages excellent error state reporting
> > I suspect we have a bug here. Note the 
> > "Returns the number of pages that were not migrated, or an error code."
> > 
> > but I do not see putback_movable_pages for ret > 0 so it seems we might
> > leak some pages.
> 
> I fell for the same thing when looking at that code.
> It took a while until I realized what was really going on.
> 
> > > Signed-off-by: Oscar Salvador <osalvador@xxxxxxx>
> > > Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
> > > Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
> > 
> > The patch itself looks reasonable but make sure to mention this is mere
> > cosmetic change unless there is a real problem fixed by this.
> > Acked-by: Michal Hocko <mhocko@xxxxxxxx>
> 
> What about appending the following in the changelog:
> 
> "Note that this is not fixing a real issue, just a cosmetic change. Although
>  we can save some cycles by backing off ealier."

Sounds good to me.

-- 
Michal Hocko
SUSE Labs