[3.16.y-ckt stable] Patch "mm: check if section present during memory block registering" has been added to staging queue

Luis Henriques luis.henriques at canonical.com
Mon Sep 28 17:21:34 UTC 2015


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

    mm: check if section present during memory block registering

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt18.

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

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From c1f1561a8fbd828bb7758f560ff346908b16c633 Mon Sep 17 00:00:00 2001
From: Yinghai Lu <yinghai at kernel.org>
Date: Fri, 4 Sep 2015 15:42:39 -0700
Subject: mm: check if section present during memory block registering

commit 04697858d89e4bf2650364f8d6956e2554e8ef88 upstream.

Tony Luck found on his setup, if memory block size 512M will cause crash
during booting.

  BUG: unable to handle kernel paging request at ffffea0074000020
  IP: get_nid_for_pfn+0x17/0x40
  PGD 128ffcb067 PUD 128ffc9067 PMD 0
  Oops: 0000 [#1] SMP
  Modules linked in:
  CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.2.0-rc8 #1
  ...
  Call Trace:
     ? register_mem_sect_under_node+0x66/0xe0
     register_one_node+0x17b/0x240
     ? pci_iommu_alloc+0x6e/0x6e
     topology_init+0x3c/0x95
     do_one_initcall+0xcd/0x1f0

The system has non continuous RAM address:
 BIOS-e820: [mem 0x0000001300000000-0x0000001cffffffff] usable
 BIOS-e820: [mem 0x0000001d70000000-0x0000001ec7ffefff] usable
 BIOS-e820: [mem 0x0000001f00000000-0x0000002bffffffff] usable
 BIOS-e820: [mem 0x0000002c18000000-0x0000002d6fffefff] usable
 BIOS-e820: [mem 0x0000002e00000000-0x00000039ffffffff] usable

So there are start sections in memory block not present.  For example:

    memory block : [0x2c18000000, 0x2c20000000) 512M

first three sections are not present.

The current register_mem_sect_under_node() assume first section is
present, but memory block section number range [start_section_nr,
end_section_nr] would include not present section.

For arch that support vmemmap, we don't setup memmap for struct page
area within not present sections area.

So skip the pfn range that belong to absent section.

[akpm at linux-foundation.org: simplification]
[rientjes at google.com: more simplification]
Fixes: bdee237c0343 ("x86: mm: Use 2GB memory block size on large memory x86-64 systems")
Fixes: 982792c782ef ("x86, mm: probe memory block size for generic x86 64bit")
Signed-off-by: Yinghai Lu <yinghai at kernel.org>
Signed-off-by: David Rientjes <rientjes at google.com>
Reported-by: Tony Luck <tony.luck at intel.com>
Tested-by: Tony Luck <tony.luck at intel.com>
Cc: Greg KH <greg at kroah.com>
Cc: Ingo Molnar <mingo at elte.hu>
Tested-by: David Rientjes <rientjes at google.com>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/base/node.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/base/node.c b/drivers/base/node.c
index 40e4585f110a..5777d10d1e25 100644
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -399,6 +399,16 @@ int register_mem_sect_under_node(struct memory_block *mem_blk, int nid)
 	for (pfn = sect_start_pfn; pfn <= sect_end_pfn; pfn++) {
 		int page_nid;

+		/*
+		 * memory block could have several absent sections from start.
+		 * skip pfn range from absent section
+		 */
+		if (!pfn_present(pfn)) {
+			pfn = round_down(pfn + PAGES_PER_SECTION,
+					 PAGES_PER_SECTION) - 1;
+			continue;
+		}
+
 		page_nid = get_nid_for_pfn(pfn);
 		if (page_nid < 0)
 			continue;




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