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From:   David Howells <dhowells@redhat.com>
In-Reply-To: <20210715033704.692967-85-willy@infradead.org>
References: <20210715033704.692967-85-willy@infradead.org> <20210715033704.692967-1-willy@infradead.org>
To:     "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc:     dhowells@redhat.com, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
        Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH v14 084/138] mm/page_alloc: Add folio allocation functions
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Content-ID: <1814545.1628632283.1@warthog.procyon.org.uk>
Date:   Tue, 10 Aug 2021 22:51:23 +0100
Message-ID: <1814546.1628632283@warthog.procyon.org.uk>
Precedence: bulk

Matthew Wilcox (Oracle) <willy@infradead.org> wrote:

> +struct folio *folio_alloc(gfp_t gfp, unsigned order)
> +{
> +	struct page *page = alloc_pages(gfp | __GFP_COMP, order);
> +
> +	if (page && order > 1)
> +		prep_transhuge_page(page);

Ummm...  Shouldn't order==1 pages (two page folios) be prep'd also?

> +	return (struct folio *)page;
> +}

Would it be better to just jump to alloc_pages() if order <= 1?  E.g.:

struct folio *folio_alloc(gfp_t gfp, unsigned order)
{
	struct page *page;

	if (order <= 1)
		return (struct folio *)alloc_pages(gfp | __GFP_COMP, order);

	page = alloc_pages(gfp | __GFP_COMP, order);
	if (page)
		prep_transhuge_page(page);
	return (struct folio *)page;
}

David