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mm: fix potential infinite loop in dissolve_free_huge_pages() 

It is possible for some platforms, such as powerpc to set HPAGE_SHIFT to
0 to indicate huge pages not supported.

When this is the case, hugetlbfs could be disabled during boot time:
hugetlbfs: disabling because there are no supported hugepage sizes

Then in dissolve_free_huge_pages(), order is kept maximum (64 for
64bits), and the for loop below won't end: for (pfn = start_pfn; pfn <
end_pfn; pfn += 1 << order)

As suggested by Naoya, below fix checks hugepages_supported() before
calling dissolve_free_huge_pages().

[rientjes@google.com: no legitimate reason to call dissolve_free_huge_pages() when !hugepages_supported()]
Signed-off-by: Li Zhong <zhong@linux.vnet.ibm.com>
Acked-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: David Rientjes <rientjes@google.com>
Cc: <stable@vger.kernel.org>	[3.12+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Li Zhong 2014-08-06 16:07:56 -07:00 committed by Linus Torvalds
parent 8fe780484d
commit d017763931
1 changed files with 3 additions and 0 deletions
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3
mm/hugetlb.c
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@ -1088,6 +1088,9 @@ void dissolve_free_huge_pages(unsigned long start_pfn, unsigned long end_pfn)
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))