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Subject[PATCH 3.11 078/128] mm: page_alloc: fix CMA area initialisation when pageblock > MAX_ORDER
Date -stable review patch.  If anyone has any objections, please let me know.


From: Michal Nazarewicz <>

commit dc78327c0ea7da5186d8cbc1647bd6088c5c9fa5 upstream.

With a kernel configured with ARM64_64K_PAGES && !TRANSPARENT_HUGEPAGE,
the following is triggered at early boot:

SMP: Total of 8 processors activated.
devtmpfs: initialized
Unable to handle kernel NULL pointer dereference at virtual address 00000008
pgd = fffffe0000050000
[00000008] *pgd=00000043fba00003, *pmd=00000043fba00003, *pte=00e0000078010407
Internal error: Oops: 96000006 [#1] SMP
Modules linked in:
CPU: 0 PID: 1 Comm: swapper/0 Not tainted 3.15.0-rc864k+ #44
task: fffffe03bc040000 ti: fffffe03bc080000 task.ti: fffffe03bc080000
PC is at __list_add+0x10/0xd4
LR is at free_one_page+0x270/0x638
Call trace:

This happens because init_cma_reserved_pageblock() calls
__free_one_page() with pageblock_order as page order but it is bigger
than MAX_ORDER. This in turn causes accesses past zone->free_list[].

Fix the problem by changing init_cma_reserved_pageblock() such that it
splits pageblock into individual MAX_ORDER pages if pageblock is bigger
than a MAX_ORDER page.

In cases where !CONFIG_HUGETLB_PAGE_SIZE_VARIABLE, which is all
architectures expect for ia64, powerpc and tile at the moment, the
“pageblock_order > MAX_ORDER” condition will be optimised out since both
sides of the operator are constants. In cases where pageblock size is
variable, the performance degradation should not be significant anyway
since init_cma_reserved_pageblock() is called only at boot time at most
MAX_CMA_AREAS times which by default is eight.

Signed-off-by: Michal Nazarewicz <>
Reported-by: Mark Salter <>
Tested-by: Mark Salter <>
Tested-by: Christopher Covington <>
Cc: Mel Gorman <>
Cc: David Rientjes <>
Cc: Marek Szyprowski <>
Cc: Catalin Marinas <>
Signed-off-by: Andrew Morton <>
Signed-off-by: Linus Torvalds <>
Signed-off-by: Luis Henriques <>
mm/page_alloc.c | 16 ++++++++++++++--
1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 6a2b267a521f..1b5e9fb49ed4 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -780,9 +780,21 @@ void __init init_cma_reserved_pageblock(struct page *page)
set_page_count(p, 0);
} while (++p, --i);

- set_page_refcounted(page);
set_pageblock_migratetype(page, MIGRATE_CMA);
- __free_pages(page, pageblock_order);
+ if (pageblock_order >= MAX_ORDER) {
+ i = pageblock_nr_pages;
+ p = page;
+ do {
+ set_page_refcounted(p);
+ __free_pages(p, MAX_ORDER - 1);
+ } while (i -= MAX_ORDER_NR_PAGES);
+ } else {
+ set_page_refcounted(page);
+ __free_pages(page, pageblock_order);
+ }
adjust_managed_page_count(page, pageblock_nr_pages);
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