Re: [PATCH] mm: return -ENOMEM for page-table allocation failure in insert_pages()

[Lorenzo Stoakes (ARM)]

On Thu, Jul 30, 2026 at 09:15:58AM -0700, Andrew Morton wrote:
> On Thu, 30 Jul 2026 08:42:49 +0100 "Lorenzo Stoakes (ARM)" <ljs@xxxxxxxxxx> wrote:
>
> > 	pages_to_write_in_pmd = min_t(unsigned long,
> > 		remaining_pages_total, PTRS_PER_PTE - pte_index(addr));
> >
> > 	/* Allocate the PTE if necessary; takes PMD lock once only. */
> > 	ret = -ENOMEM; <------------------------------ set it again?
> > 	if (pte_alloc(mm, pmd))
> > 		goto out;
> >
> > The way this function is written is horrible in general, I hate 'preset default
> > return value' as a pattern.
>
> It used to be the preferred way because
>
> 	ret = -ENOMEM;
> 	if (expr)
> 		goto out;
>
> generated slightly better code than
>
> 	if (expr) {
> 		ret = -ENOMEM;
> 		goto out;
> 	}
>
> Whether that is the case with current compilers I don't know.

Thanks for the background on that!

I'd put money on there being no difference now :) but in any case that kind of
micro-optimisation isn't really a concern here even if it was the case.

--
Cheers, Lorenzo