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Date: Fri, 16 Oct 2015 16:00:50 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Hugh Dickins <hughd@google.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Stephen Rothwell <sfr@canb.auug.org.au>, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org
Subject: Re: [PATCH mmotm] mm: use unsigned int for page order fix 2
Message-Id: <20151016160050.621082b8b1080c28487e764f@linux-foundation.org>
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On Fri, 16 Oct 2015 15:51:34 -0700 (PDT) Hugh Dickins <hughd@google.com> wrote:

> Some configs now end up with MAX_ORDER and pageblock_order having
> different types: silence compiler warning in __free_one_page().
> 
> ...
>
> @@ -679,7 +679,7 @@ static inline void __free_one_page(struc
>  		 * pageblock. Without this, pageblock isolation
>  		 * could cause incorrect freepage accounting.
>  		 */
> -		max_order = min(MAX_ORDER, pageblock_order + 1);
> +		max_order = min_t(unsigned int, MAX_ORDER, pageblock_order + 1);
>  	} else {
>  		__mod_zone_freepage_state(zone, 1 << order, migratetype);
>  	}

Well.  If we're ordaining that "page order has type uint" then can we
do that more consistently?  Something like

--- a/include/linux/mmzone.h~a
+++ a/include/linux/mmzone.h
@@ -21,9 +21,9 @@
 
 /* Free memory management - zoned buddy allocator.  */
 #ifndef CONFIG_FORCE_MAX_ZONEORDER
-#define MAX_ORDER 11
+#define MAX_ORDER 11U
 #else
-#define MAX_ORDER CONFIG_FORCE_MAX_ZONEORDER
+#define MAX_ORDER ((unsigned int)CONFIG_FORCE_MAX_ZONEORDER)
 #endif
 #define MAX_ORDER_NR_PAGES (1 << (MAX_ORDER - 1))
 
diff -puN include/linux/pageblock-flags.h~a include/linux/pageblock-flags.h
--- a/include/linux/pageblock-flags.h~a
+++ a/include/linux/pageblock-flags.h
@@ -49,7 +49,7 @@ extern unsigned int pageblock_order;
 #else /* CONFIG_HUGETLB_PAGE_SIZE_VARIABLE */
 
 /* Huge pages are a constant size */
-#define pageblock_order		HUGETLB_PAGE_ORDER
+#define pageblock_order		((unsigned int)HUGETLB_PAGE_ORDER)
 
 #endif /* CONFIG_HUGETLB_PAGE_SIZE_VARIABLE */
 
_