[PATCH 3.16.y-ckt 072/133] mm: check if section present during memory block registering

From: Luis Henriques
Date: Wed Sep 30 2015 - 05:53:26 EST

3.16.7-ckt18 -stable review patch. If anyone has any objections, please let me know.


From: Yinghai Lu <yinghai@xxxxxxxxxx>

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
? pci_iommu_alloc+0x6e/0x6e

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@xxxxxxxxxxxxxxxxxxxx: simplification]
[rientjes@xxxxxxxxxx: 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@xxxxxxxxxx>
Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
Reported-by: Tony Luck <tony.luck@xxxxxxxxx>
Tested-by: Tony Luck <tony.luck@xxxxxxxxx>
Cc: Greg KH <greg@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Tested-by: David Rientjes <rientjes@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Luis Henriques <luis.henriques@xxxxxxxxxxxxx>
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,
+ continue;
+ }
page_nid = get_nid_for_pfn(pfn);
if (page_nid < 0)
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