[3.13.y.z extended stable] Patch "mm: page_alloc: fix CMA area initialisation when pageblock > MAX_ORDER" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

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

to the linux-3.13.y-queue branch of the 3.13.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11.6.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

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>From dd08f6b074bf6141d88b5abe810468c0bbb7d148 Mon Sep 17 00:00:00 2001
From: Michal Nazarewicz <mina86 at mina86.com>
Date: Wed, 2 Jul 2014 15:22:35 -0700
Subject: mm: page_alloc: fix CMA area initialisation when pageblock >
 MAX_ORDER
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

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
“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 <mina86 at mina86.com>
Reported-by: Mark Salter <msalter at redhat.com>
Tested-by: Mark Salter <msalter at redhat.com>
Tested-by: Christopher Covington <cov at codeaurora.org>
Cc: Mel Gorman <mgorman at suse.de>
Cc: David Rientjes <rientjes at google.com>
Cc: Marek Szyprowski <m.szyprowski at samsung.com>
Cc: Catalin Marinas <catalin.marinas at arm.com>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Signed-off-by: Kamal Mostafa <kamal at canonical.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 856d95c..c4133b4 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -785,9 +785,21 @@ 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