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

[Oscar Salvador]

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."


-- 
Oscar Salvador
SUSE L3