[PATCH] x86_64: Handle empty PXMs that only contain hotplug memory

The node setup code would try to allocate the node metadata in the node
itself, but that fails if there is no memory in there.

This can happen with memory hotplug when the hotplug area defines an so
far empty node.

Now use bootmem to try to allocate the mem_map in other nodes.

And if it fails don't panic, but just ignore the node.

To make this work I added a new __alloc_bootmem_nopanic function that
does what its name implies.

TBD should try to use nearby nodes here.  Currently we just use any.
It's hard to do it better because bootmem doesn't have proper fallback
lists yet.

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/x86_64/mm/numa.c

@@ -100,11 +100,30 @@ int early_pfn_to_nid(unsigned long pfn)
 }
 #endif
 
+static void * __init
+early_node_mem(int nodeid, unsigned long start, unsigned long end,
+	      unsigned long size)
+{
+	unsigned long mem = find_e820_area(start, end, size);
+	void *ptr;
+	if (mem != -1L)
+		return __va(mem);
+	ptr = __alloc_bootmem_nopanic(size,
+				SMP_CACHE_BYTES, __pa(MAX_DMA_ADDRESS));
+	if (ptr == 0) {
+		printk(KERN_ERR "Cannot find %lu bytes in node %d\n",
+			size, nodeid);
+		return NULL;
+	}
+	return ptr;
+}
+
 /* Initialize bootmem allocator for a node */
 void __init setup_node_bootmem(int nodeid, unsigned long start, unsigned long end)
 { 
 	unsigned long start_pfn, end_pfn, bootmap_pages, bootmap_size, bootmap_start; 
 	unsigned long nodedata_phys;
+	void *bootmap;
 	const int pgdat_size = round_up(sizeof(pg_data_t), PAGE_SIZE);
 
 	start = round_up(start, ZONE_ALIGN); 
@@ -114,13 +133,11 @@ void __init setup_node_bootmem(int nodeid, unsigned long start, unsigned long en
 	start_pfn = start >> PAGE_SHIFT;
 	end_pfn = end >> PAGE_SHIFT;
 
-	nodedata_phys = find_e820_area(start, end, pgdat_size); 
-	if (nodedata_phys == -1L) 
-		panic("Cannot find memory pgdat in node %d\n", nodeid);
-
-	Dprintk("nodedata_phys %lx\n", nodedata_phys); 
+	node_data[nodeid] = early_node_mem(nodeid, start, end, pgdat_size);
+	if (node_data[nodeid] == NULL)
+		return;
+	nodedata_phys = __pa(node_data[nodeid]);
 
-	node_data[nodeid] = phys_to_virt(nodedata_phys);
 	memset(NODE_DATA(nodeid), 0, sizeof(pg_data_t));
 	NODE_DATA(nodeid)->bdata = &plat_node_bdata[nodeid];
 	NODE_DATA(nodeid)->node_start_pfn = start_pfn;
@@ -129,9 +146,15 @@ void __init setup_node_bootmem(int nodeid, unsigned long start, unsigned long en
 	/* Find a place for the bootmem map */
 	bootmap_pages = bootmem_bootmap_pages(end_pfn - start_pfn); 
 	bootmap_start = round_up(nodedata_phys + pgdat_size, PAGE_SIZE);
-	bootmap_start = find_e820_area(bootmap_start, end, bootmap_pages<<PAGE_SHIFT);
-	if (bootmap_start == -1L) 
-		panic("Not enough continuous space for bootmap on node %d", nodeid); 
+	bootmap = early_node_mem(nodeid, bootmap_start, end,
+					bootmap_pages<<PAGE_SHIFT);
+	if (bootmap == NULL)  {
+		if (nodedata_phys < start || nodedata_phys >= end)
+			free_bootmem((unsigned long)node_data[nodeid],pgdat_size);
+		node_data[nodeid] = NULL;
+		return;
+	}
+	bootmap_start = __pa(bootmap);
 	Dprintk("bootmap start %lu pages %lu\n", bootmap_start, bootmap_pages); 
 
 	bootmap_size = init_bootmem_node(NODE_DATA(nodeid),

arch/x86_64/mm/srat.c

@@ -415,6 +415,12 @@ int __init acpi_scan_nodes(unsigned long start, unsigned long end)
 	/* Finally register nodes */
 	for_each_node_mask(i, nodes_parsed)
 		setup_node_bootmem(i, nodes[i].start, nodes[i].end);
+	/* Try again in case setup_node_bootmem missed one due
+	   to missing bootmem */
+	for_each_node_mask(i, nodes_parsed)
+		if (!node_online(i))
+			setup_node_bootmem(i, nodes[i].start, nodes[i].end);
+
 	for (i = 0; i < NR_CPUS; i++) { 
 		if (cpu_to_node[i] == NUMA_NO_NODE)
 			continue;

include/linux/bootmem.h

@@ -45,6 +45,7 @@ extern unsigned long __init bootmem_bootmap_pages (unsigned long);
 extern unsigned long __init init_bootmem (unsigned long addr, unsigned long memend);
 extern void __init free_bootmem (unsigned long addr, unsigned long size);
 extern void * __init __alloc_bootmem (unsigned long size, unsigned long align, unsigned long goal);
+extern void * __init __alloc_bootmem_nopanic (unsigned long size, unsigned long align, unsigned long goal);
 extern void * __init __alloc_bootmem_low(unsigned long size,
 					 unsigned long align,
 					 unsigned long goal);

mm/bootmem.c

@@ -401,15 +401,22 @@ unsigned long __init free_all_bootmem (void)
 	return(free_all_bootmem_core(NODE_DATA(0)));
 }
 
-void * __init __alloc_bootmem(unsigned long size, unsigned long align, unsigned long goal)
+void * __init __alloc_bootmem_nopanic(unsigned long size, unsigned long align, unsigned long goal)
 {
 	bootmem_data_t *bdata;
 	void *ptr;
 
 	list_for_each_entry(bdata, &bdata_list, list)
 		if ((ptr = __alloc_bootmem_core(bdata, size, align, goal, 0)))
 			return(ptr);
+	return NULL;
+}
 
+void * __init __alloc_bootmem(unsigned long size, unsigned long align, unsigned long goal)
+{
+	void *mem = __alloc_bootmem_nopanic(size,align,goal);
+	if (mem)
+		return mem;
 	/*
 	 * Whoops, we cannot satisfy the allocation request.
 	 */