re: mm: memory-hotplug: enable memory hotplug to handle hugepage

[Dan Carpenter <dan.carpenter@oracle.com>]

Hello Naoya Horiguchi,

The patch c8721bbbdd36: "mm: memory-hotplug: enable memory hotplug to
handle hugepage" from Sep 11, 2013, leads to the following static
checker warning:

	mm/hugetlb.c:1203 dissolve_free_huge_pages()
	warn: potential right shift more than type allows '9,18,64'

mm/hugetlb.c
  1189  void dissolve_free_huge_pages(unsigned long start_pfn, unsigned long end_pfn)
  1190  {
  1191          unsigned int order = 8 * sizeof(void *);
                                     ^^^^^^^^^^^^^^^^^^
Let's say order is 64.

  1192          unsigned long pfn;
  1193          struct hstate *h;
  1194  
  1195          if (!hugepages_supported())
  1196                  return;
  1197  
  1198          /* Set scan step to minimum hugepage size */
  1199          for_each_hstate(h)
  1200                  if (order > huge_page_order(h))
  1201                          order = huge_page_order(h);
  1202          VM_BUG_ON(!IS_ALIGNED(start_pfn, 1 << order));
  1203          for (pfn = start_pfn; pfn < end_pfn; pfn += 1 << order)
                                                            ^^^^^^^^^^
1 << 64 is undefined but let's say it's zero because that's normal for
GCC.  This is an endless loop.

  1204                  dissolve_free_huge_page(pfn_to_page(pfn));
  1205  }

regards,
dan carpenter

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