Commit dc78327c authored by Michal Nazarewicz's avatar Michal Nazarewicz Committed by Linus Torvalds
Browse files

mm: page_alloc: fix CMA area initialisation when pageblock > MAX_ORDER

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: default avatarMichal Nazarewicz <>
Reported-by: default avatarMark Salter <>
Tested-by: default avatarMark Salter <>
Tested-by: default avatarChristopher Covington <>
Cc: Mel Gorman <>
Cc: David Rientjes <>
Cc: Marek Szyprowski <>
Cc: Catalin Marinas <>
Cc: <>	[3.5+]
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent d92a333a
......@@ -816,9 +816,21 @@ void __init init_cma_reserved_pageblock(struct page *page)
set_page_count(p, 0);
} while (++p, --i);
set_pageblock_migratetype(page, MIGRATE_CMA);
__free_pages(page, pageblock_order);
if (pageblock_order >= MAX_ORDER) {
i = pageblock_nr_pages;
p = page;
do {
__free_pages(p, MAX_ORDER - 1);
} while (i -= MAX_ORDER_NR_PAGES);
} else {
__free_pages(page, pageblock_order);
adjust_managed_page_count(page, pageblock_nr_pages);
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