linux-kernel - Re: [PATCH v8 5/7] mm: Make alloc_contig

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Date:   Thu, 15 Apr 2021 14:45:11 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Oscar Salvador <osalvador@...e.de>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     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, Michal Hocko <mhocko@...e.com>
Subject: Re: [PATCH v8 5/7] mm: Make alloc_contig_range handle free hugetlb
 pages

> +		if (PageHuge(page) && cc->alloc_contig) {
> +			ret = isolate_or_dissolve_huge_page(page);
> +
> +			/*
> +			 * Fail isolation in case isolate_or_dissolve_huge_page()
> +			 * reports an error. In case of -ENOMEM, abort right away.
> +			 */
> +			if (ret < 0) {
> +				/*
> +				 * Do not report -EBUSY down the chain.
> +				 */

Nit: can fit this into a single line.

> +				if (ret != -ENOMEM)
> +					ret = 0;

Nit: I wonder if ret == -EBUSY would be clearer.

> +				low_pfn += (1UL << compound_order(page)) - 1;
> +				goto isolate_fail;
> +			}
> +
> +			/*
> +			 * Ok, the hugepage was dissolved. Now these pages are
> +			 * Buddy and cannot be re-allocated because they are
> +			 * isolated. Fall-through as the check below handles
> +			 * Buddy pages.
> +			 */
> +		}
> +

[...]

> +/*
> + * alloc_and_dissolve_huge_page - Allocate a new page and dissolve the old one
> + * @h: struct hstate old page belongs to
> + * @old_page: Old page to dissolve
> + * Returns 0 on success, otherwise negated error.
> + */
> +

nit: remove that line

Acked-by: David Hildenbrand <david@...hat.com>

-- 
Thanks,

David / dhildenb