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Commit c1a0bf34 authored by Ingo Molnar's avatar Ingo Molnar
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x86/mm/numa: Clean up numa_clear_kernel_node_hotplug() 



So we fixed an overflow bug in numa_clear_kernel_node_hotplug():

  2b54ab3c66d4 ("x86/mm/numa: Fix memory corruption on 32-bit NUMA kernels")

... and the bug was indirectly caused by poor coding style,
such as using start/end local variables unnecessarily, which
lost the physaddr_t type.

So make the code more readable and try to fully comment all
the thinking behind the logic.

No change in functionality.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Brad Spengler <spender@grsecurity.net>
Cc: Chen Tang <imtangchen@gmail.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: PaX Team <pageexec@freemail.hu>
Cc: Taku Izumi <izumi.taku@jp.fujitsu.com>
Cc: Tang Chen <tangchen@cn.fujitsu.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Wen Congyang <wency@cn.fujitsu.com>
Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Cc: y14sg1 <y14sg1@comcast.net>
Cc: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent b349e9a9

arch/x86/mm/numa.c

+42 −23
Original line number Diff line number Diff line
@@ -465,46 +465,65 @@ static bool __init numa_meminfo_cover_memory(const struct numa_meminfo *mi) 
	return true;

}



/*

 * Mark all currently memblock-reserved physical memory (which covers the

 * kernel's own memory ranges) as hot-unswappable.

 */

static void __init numa_clear_kernel_node_hotplug(void)

{

	int i, nid;

	nodemask_t numa_kernel_nodes = NODE_MASK_NONE;

	phys_addr_t start, end;

	struct memblock_region *r;

	nodemask_t reserved_nodemask = NODE_MASK_NONE;

	struct memblock_region *mb_region;

	int i;



	/*

	 * We have to do some preprocessing of memblock regions, to

	 * make them suitable for reservation.

	 *

	 * At this time, all memory regions reserved by memblock are

	 * used by the kernel. Set the nid in memblock.reserved will

	 * mark out all the nodes the kernel resides in.

	 * used by the kernel, but those regions are not split up

	 * along node boundaries yet, and don't necessarily have their

	 * node ID set yet either.

	 *

	 * So iterate over all memory known to the x86 architecture,

	 * and use those ranges to set the nid in memblock.reserved.

	 * This will split up the memblock regions along node

	 * boundaries and will set the node IDs as well.

	 */

	for (i = 0; i < numa_meminfo.nr_blks; i++) {

		struct numa_memblk *mb = &numa_meminfo.blk[i];

		struct numa_memblk *mb = numa_meminfo.blk + i;



		memblock_set_node(mb->start, mb->end - mb->start,

				  &memblock.reserved, mb->nid);

		memblock_set_node(mb->start, mb->end - mb->start, &memblock.reserved, mb->nid);

	}



	/*

	 * Mark all kernel nodes.

	 * Now go over all reserved memblock regions, to construct a

	 * node mask of all kernel reserved memory areas.

	 *

	 * When booting with mem=nn[kMG] or in a kdump kernel, numa_meminfo

	 * may not include all the memblock.reserved memory ranges because

	 * trim_snb_memory() reserves specific pages for Sandy Bridge graphics.

	 * [ Note, when booting with mem=nn[kMG] or in a kdump kernel,

	 *   numa_meminfo might not include all memblock.reserved

	 *   memory ranges, because quirks such as trim_snb_memory()

	 *   reserve specific pages for Sandy Bridge graphics. ]

	 */

	for_each_memblock(reserved, r)

		if (r->nid != MAX_NUMNODES)

			node_set(r->nid, numa_kernel_nodes);

	for_each_memblock(reserved, mb_region) {

		if (mb_region->nid != MAX_NUMNODES)

			node_set(mb_region->nid, reserved_nodemask);

	}



	/* Clear MEMBLOCK_HOTPLUG flag for memory in kernel nodes. */

	/*

	 * Finally, clear the MEMBLOCK_HOTPLUG flag for all memory

	 * belonging to the reserved node mask.

	 *

	 * Note that this will include memory regions that reside

	 * on nodes that contain kernel memory - entire nodes

	 * become hot-unpluggable:

	 */

	for (i = 0; i < numa_meminfo.nr_blks; i++) {

		nid = numa_meminfo.blk[i].nid;

		if (!node_isset(nid, numa_kernel_nodes))

			continue;

		struct numa_memblk *mb = numa_meminfo.blk + i;



		start = numa_meminfo.blk[i].start;

		end = numa_meminfo.blk[i].end;

		if (!node_isset(mb->nid, reserved_nodemask))

			continue;



		memblock_clear_hotplug(start, end - start);

		memblock_clear_hotplug(mb->start, mb->end - mb->start);

	}

}