On Thu, Mar 25, 2021 at 12:12:17PM +0000, Matthew Wilcox wrote: > On Thu, Mar 25, 2021 at 11:42:23AM +0000, Mel Gorman wrote: > > > > - if (WARN_ON_ONCE(nr_pages <= 0)) > > + if (unlikely(nr_pages <= 0)) > > return 0; > > If we made nr_pages unsigned, we wouldn't need this check at all (ok, > we'd still need to figure out what to do with 0). But then, if a user > inadvertently passes in -ENOMEM, we'll try to allocate 4 billion pages.
This is exactly why nr_pages is signed. An error in accounting by the caller potentially puts the system under severe memory pressure. This *should* only be a problem when a new caller of the API is being implemented. The warning goes away in a later patch for reasons explained in the changelog. > So maybe we should check it. Gah, API design is hard. Yep. -- Mel Gorman SUSE Labs
