linux-kernel - [PATCH 3.11 078/128] mm: page_alloc: fix CMA area initialisation when pageblock > MAX

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Date:	Thu, 24 Jul 2014 10:45:27 +0100
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Michal Nazarewicz <mina86@...a86.com>,
	Mel Gorman <mgorman@...e.de>,
	David Rientjes <rientjes@...gle.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.11 078/128] mm: page_alloc: fix CMA area initialisation when pageblock > MAX_ORDER

3.11.10.14 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Michal Nazarewicz <mina86@...a86.com>

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:
    __list_add+0x10/0xd4
    free_one_page+0x26c/0x638
    __free_pages_ok.part.52+0x84/0xbc
    __free_pages+0x74/0xbc
    init_cma_reserved_pageblock+0xe8/0x104
    cma_init_reserved_areas+0x190/0x1e4
    do_one_initcall+0xc4/0x154
    kernel_init_freeable+0x204/0x2a8
    kernel_init+0xc/0xd4

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
âpageblock_order > MAX_ORDERâ 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 <mina86@...a86.com>
Reported-by: Mark Salter <msalter@...hat.com>
Tested-by: Mark Salter <msalter@...hat.com>
Tested-by: Christopher Covington <cov@...eaurora.org>
Cc: Mel Gorman <mgorman@...e.de>
Cc: David Rientjes <rientjes@...gle.com>
Cc: Marek Szyprowski <m.szyprowski@...sung.com>
Cc: Catalin Marinas <catalin.marinas@....com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 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);
+			p += MAX_ORDER_NR_PAGES;
+		} while (i -= MAX_ORDER_NR_PAGES);
+	} else {
+		set_page_refcounted(page);
+		__free_pages(page, pageblock_order);
+	}
+
 	adjust_managed_page_count(page, pageblock_nr_pages);
 }
 #endif
-- 
1.9.1

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