mm/hugetlb: introduce minimum hugepage order (641844f5) · Commits · 戴 / test

Currently the initial value of order in dissolve_free_huge_page is 64 or 32, which leads to the following warning in static checker: mm/hugetlb.c:1203 dissolve_free_huge_pages() warn: potential right shift more than type allows '9,18,64' This is a potential risk of infinite loop, because 1 << order (== 0) is used in for-loop like this: for (pfn =3D start_pfn; pfn < end_pfn; pfn +=3D 1 << order) ... So this patch fixes it by using global minimum_order calculated at boot time. text data bss dec hex filename 28313 469 84236 113018 1b97a mm/hugetlb.o 28256 473 84236 112965 1b945 mm/hugetlb.o (patched) Fixes: ("mm: memory-hotplug: enable memory hotplug to handle hugepage") Reported-by:

Dan Carpenter <dan.carpenter@oracle.com> Signed-off-by:

Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

mm/hugetlb.c

+11 −8

Original line number	Diff line number	Diff line
		@@ -40,6 +40,11 @@ int hugepages_treat_as_movable;
		int hugetlb_max_hstate __read_mostly;
		unsigned int default_hstate_idx;
		struct hstate hstates[HUGE_MAX_HSTATE];
		/*
		* Minimum page order among possible hugepage sizes, set to a proper value
		* at boot time.
		*/
		static unsigned int minimum_order __read_mostly = UINT_MAX;

		__initdata LIST_HEAD(huge_boot_pages);

		@@ -1188,19 +1193,13 @@ static void dissolve_free_huge_page(struct page *page)
		*/
		void dissolve_free_huge_pages(unsigned long start_pfn, unsigned long end_pfn)
		{
		unsigned int order = 8 * sizeof(void *);
		unsigned long pfn;
		struct hstate *h;

		if (!hugepages_supported())
		return;

		/* Set scan step to minimum hugepage size */
		for_each_hstate(h)
		if (order > huge_page_order(h))
		order = huge_page_order(h);
		VM_BUG_ON(!IS_ALIGNED(start_pfn, 1 << order));
		for (pfn = start_pfn; pfn < end_pfn; pfn += 1 << order)
		VM_BUG_ON(!IS_ALIGNED(start_pfn, 1 << minimum_order));
		for (pfn = start_pfn; pfn < end_pfn; pfn += 1 << minimum_order)
		dissolve_free_huge_page(pfn_to_page(pfn));
		}

		@@ -1627,10 +1626,14 @@ static void __init hugetlb_init_hstates(void)
		struct hstate *h;

		for_each_hstate(h) {
		if (minimum_order > huge_page_order(h))
		minimum_order = huge_page_order(h);

		/* oversize hugepages were init'ed in early boot */
		if (!hstate_is_gigantic(h))
		hugetlb_hstate_alloc_pages(h);
		}
		VM_BUG_ON(minimum_order == UINT_MAX);
		}

		static char * __init memfmt(char *buf, unsigned long n)

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