[PATCH v2]mm: fix potential infinite loop in dissolve_free_huge_pages()

[Li Zhong <zhong@linux.vnet.ibm.com>]

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().

Signed-off-by: Li Zhong <zhong@linux.vnet.ibm.com>
---
 mm/memory_hotplug.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 469bbf5..f642701 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1695,7 +1695,8 @@ repeat:
 	 * dissolve free hugepages in the memory block before doing offlining
 	 * actually in order to make hugetlbfs's object counting consistent.
 	 */
-	dissolve_free_huge_pages(start_pfn, end_pfn);
+	if (hugepages_supported())
+		dissolve_free_huge_pages(start_pfn, end_pfn);
 	/* check again */
 	offlined_pages = check_pages_isolated(start_pfn, end_pfn);
 	if (offlined_pages < 0) {


--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>