linux-kernel - Re: [PATCH v2 1/5] hugetlb: use page.private for hugetlb specific page flags

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Message-ID: <20210120093015.GA4194@localhost.localdomain>
Date:   Wed, 20 Jan 2021 10:30:15 +0100
From:   Oscar Salvador <osalvador@...e.de>
To:     Mike Kravetz <mike.kravetz@...cle.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Michal Hocko <mhocko@...nel.org>,
        Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
        Muchun Song <songmuchun@...edance.com>,
        David Hildenbrand <david@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v2 1/5] hugetlb: use page.private for hugetlb specific
 page flags

On Tue, Jan 19, 2021 at 05:30:45PM -0800, Mike Kravetz wrote:
> + * Macros to create test, set and clear function definitions for
> + * hugetlb specific page flags.
> + */
> +#ifdef CONFIG_HUGETLB_PAGE
> +#define TESTHPAGEFLAG(uname, flname)				\
> +static inline int HPage##uname(struct page *page)		\
> +	{ BUILD_BUG_ON(sizeof_field(struct page, private) *	\
> +			BITS_PER_BYTE < __NR_HPAGEFLAGS);	\
> +	return test_bit(HPG_##flname, &(page->private)); }
> +
> +#define SETHPAGEFLAG(uname, flname)				\
> +static inline void SetHPage##uname(struct page *page)		\
> +	{ set_bit(HPG_##flname, &(page->private)); }
> +
> +#define CLEARHPAGEFLAG(uname, flname)				\
> +static inline void ClearHPage##uname(struct page *page)		\
> +	{ clear_bit(HPG_##flname, &(page->private)); }
> +#else
> +#define TESTHPAGEFLAG(uname, flname)				\
> +static inline int HPage##uname(struct page *page)		\
> +	{ BUILD_BUG_ON(sizeof_field(struct page, private) *	\
> +			BITS_PER_BYTE < __NR_HPAGEFLAGS);	\
> +	return 0 }

You missed a ";" right there.

I might be missing something, but I do not think we need a BUILD_BUG_ON there
when CONFIG_HUGETLB_PAGE is not set?
Actually, would make more sense to move the BUILD_BUG_ON from above to
hugetlb_init?

Other than that, looks good to me, and I think it is a great improvment
towards readability and maintability.

-- 
Oscar Salvador
SUSE L3