Commit 7568fb63 authored Aug 25, 2015 by Yinghai Lu Committed by Greg Kroah-Hartman Oct 05, 2015

mm: Check if section present during memory block (un)registering



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

 BUG: unable to handle kernel paging request at ffffea0074000020
 IP: [<ffffffff81670527>] 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:
  [<ffffffff81453b56>] ? register_mem_sect_under_node+0x66/0xe0
  [<ffffffff81453eeb>] register_one_node+0x17b/0x240
  [<ffffffff81b1f1ed>] ? pci_iommu_alloc+0x6e/0x6e
  [<ffffffff81b1f229>] topology_init+0x3c/0x95
  [<ffffffff8100213d>] 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.

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.

Also fixes unregister_mem_sect_under_nodes() that assume one section per
memory block.

Reported-by: Tony Luck <tony.luck@intel.com>
Tested-by: Tony Luck <tony.luck@intel.com>
Fixes: bdee237c ("x86: mm: Use 2GB memory block size on large memory x86-64 systems")
Fixes: 982792c7 ("x86, mm: probe memory block size for generic x86 64bit")
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Cc: stable@vger.kernel.org #v3.15
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 1f35d04a

drivers/base/node.c

+27 −4

Original line number	Diff line number	Diff line
		@@ -390,7 +390,18 @@ int register_mem_sect_under_node(struct memory_block *mem_blk, int nid)
		sect_end_pfn = section_nr_to_pfn(mem_blk->end_section_nr);
		sect_end_pfn += PAGES_PER_SECTION - 1;
		for (pfn = sect_start_pfn; pfn <= sect_end_pfn; pfn++) {
		int page_nid;
		int page_nid, scn_nr;

		/*
		* memory block could have several absent sections from start.
		* skip pfn range from absent section
		*/
		scn_nr = pfn_to_section_nr(pfn);
		if (!present_section_nr(scn_nr)) {
		pfn = round_down(pfn + PAGES_PER_SECTION,
		PAGES_PER_SECTION) - 1;
		continue;
		}

		/*
		* memory block could have several absent sections from start.
		@@ -436,10 +447,22 @@ int unregister_mem_sect_under_nodes(struct memory_block *mem_blk,
		return -ENOMEM;
		nodes_clear(*unlinked_nodes);

		sect_start_pfn = section_nr_to_pfn(phys_index);
		sect_end_pfn = sect_start_pfn + PAGES_PER_SECTION - 1;
		sect_start_pfn = section_nr_to_pfn(mem_blk->start_section_nr);
		sect_end_pfn = section_nr_to_pfn(mem_blk->end_section_nr);
		sect_end_pfn += PAGES_PER_SECTION - 1;
		for (pfn = sect_start_pfn; pfn <= sect_end_pfn; pfn++) {
		int nid;
		int nid, scn_nr;

		/*
		* memory block could have several absent sections from start.
		* skip pfn range from absent section
		*/
		scn_nr = pfn_to_section_nr(pfn);
		if (!present_section_nr(scn_nr)) {
		pfn = round_down(pfn + PAGES_PER_SECTION,
		PAGES_PER_SECTION) - 1;
		continue;
		}

		nid = get_nid_for_pfn(pfn);
		if (nid < 0)

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