[PATCH 2/2] MM: check limit while deallocating bootmem node

[Gavin Shan <shangw@linux.vnet.ibm.com>]

For the particular bootmem node, the minimal and maximal PFN (
Page Frame Number) have been traced in the instance of "struct
bootmem_data_t". On current implementation, the maximal PFN isn't
checked while deallocating a bunch (BITS_PER_LONG) of page frames.
So the current implementation won't work if the maximal PFN isn't
aligned with BITS_PER_LONG.

The patch will check the maximal PFN of the given bootmem node.
Also, we needn't check all the bits map when the starting PFN isn't
BITS_PER_LONG aligned. Actually, we should start from the offset
of the bits map, which indicated by the starting PFN.

Signed-off-by: Gavin Shan <shangw@linux.vnet.ibm.com>
---
 mm/bootmem.c |   11 ++++++++---
 1 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/mm/bootmem.c b/mm/bootmem.c
index 5a04536..ebac3ba 100644
--- a/mm/bootmem.c
+++ b/mm/bootmem.c
@@ -194,16 +194,20 @@ static unsigned long __init free_all_bootmem_core(bootmem_data_t *bdata)
 		 * BITS_PER_LONG block of pages in front of us, free
 		 * it in one go.
 		 */
-		if (IS_ALIGNED(start, BITS_PER_LONG) && vec == ~0UL) {
+		if (end - start >= BITS_PER_LONG &&
+		    IS_ALIGNED(start, BITS_PER_LONG) &&
+		    vec == ~0UL) {
 			int order = ilog2(BITS_PER_LONG);
 
 			__free_pages_bootmem(pfn_to_page(start), order);
 			count += BITS_PER_LONG;
 			start += BITS_PER_LONG;
 		} else {
-			unsigned long off = 0;
+			unsigned long cursor = start;
+			unsigned long off = cursor & (BITS_PER_LONG - 1);
 
-			while (vec && off < BITS_PER_LONG) {
+			vec >>= off;
+			while (vec && off < BITS_PER_LONG && cursor < end) {
 				if (vec & 1) {
 					page = pfn_to_page(start + off);
 					__free_pages_bootmem(page, 0);
@@ -211,6 +215,7 @@ static unsigned long __init free_all_bootmem_core(bootmem_data_t *bdata)
 				}
 				vec >>= 1;
 				off++;
+				cursor++;
 			}
 			start = ALIGN(start + 1, BITS_PER_LONG);
 		}
-- 
1.7.5.4

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