linux-kernel - Re: [PATCH v7 5/7] mm: Make alloc_contig

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Date:   Thu, 15 Apr 2021 10:28:23 +0200
From:   Oscar Salvador <osalvador@...e.de>
To:     David Hildenbrand <david@...hat.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Michal Hocko <mhocko@...nel.org>,
        Muchun Song <songmuchun@...edance.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 5/7] mm: Make alloc_contig_range handle free hugetlb
 pages

On Wed, Apr 14, 2021 at 02:26:21PM +0200, David Hildenbrand wrote:
> > +static inline int isolate_or_dissolve_huge_page(struct page *page)
> > +{
> > +	return -ENOMEM;
> 
> Without CONFIG_HUGETLB_PAGE, there is no way someone could possible pass in
> something valid. Although it doesn't matter too much, -EINVAL or similar
> sounds a bit better.

I guess we could, was just to make it consistent with the kind of error
we return when we have it enabled.

> > @@ -809,6 +809,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
> >   	bool skip_on_failure = false;
> >   	unsigned long next_skip_pfn = 0;
> >   	bool skip_updated = false;
> > +	bool fatal_error = false;
> 
> Can't we use "ret == -ENOMEM" instead of fatal_error?

Yes, we can, I will see how it looks.

[...]

> > +	/*
> > +	 * Fence off gigantic pages as there is a cyclic dependency between
> > +	 * alloc_contig_range and them. Return -ENOME as this has the effect
> 
> s/-ENOME/-ENOMEM/

thanks, I missed that one.

> 
> > +	 * of bailing out right away without further retrying.
> > +	 */
> > +	if (hstate_is_gigantic(h))
> > +		return -ENOMEM;
> > +
> > +	return alloc_and_dissolve_huge_page(h, head);
> > +}
> > +
> >   struct page *alloc_huge_page(struct vm_area_struct *vma,
> >   				    unsigned long addr, int avoid_reserve)
> >   {
> > 
> 
> Complicated stuff, but looks good to me.

Thanks for having a look!

-- 
Oscar Salvador
SUSE L3