mm/memory_hotplug: make unregister_memory_block_under_nodes() never fail

We really don't want anything during memory hotunplug to fail.  We
always pass a valid memory block device, that check can go.  Avoid
allocating memory and eventually failing.  As we are always called under
lock, we can use a static piece of memory.  This avoids having to put
the structure onto the stack, having to guess about the stack size of
callers.

Patch inspired by a patch from Oscar Salvador.

In the future, there might be no need to iterate over nodes at all.
mem->nid should tell us exactly what to remove.  Memory block devices
with mixed nodes (added during boot) should properly fenced off and
never removed.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: David Hildenbrand <[email protected]>
Reviewed-by: Wei Yang <[email protected]>
Reviewed-by: Oscar Salvador <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: "Rafael J. Wysocki" <[email protected]>
Cc: Alex Deucher <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: Mark Brown <[email protected]>
Cc: Chris Wilson <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Jonathan Cameron <[email protected]>
Cc: Andrew Banman <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Anshuman Khandual <[email protected]>
Cc: Ard Biesheuvel <[email protected]>
Cc: Arun KS <[email protected]>
Cc: Baoquan He <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Chintan Pandya <[email protected]>
Cc: Christophe Leroy <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Fenghua Yu <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Joonsoo Kim <[email protected]>
Cc: Jun Yao <[email protected]>
Cc: "Kirill A. Shutemov" <[email protected]>
Cc: Logan Gunthorpe <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Masahiro Yamada <[email protected]>
Cc: Mathieu Malaterre <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: "[email protected]" <[email protected]>
Cc: Nicholas Piggin <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Pavel Tatashin <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Qian Cai <[email protected]>
Cc: Rich Felker <[email protected]>
Cc: Rob Herring <[email protected]>
Cc: Robin Murphy <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Tony Luck <[email protected]>
Cc: Vasily Gorbik <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Yoshinori Sato <[email protected]>
Cc: Yu Zhao <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

2 files changed, 7 insertions, 16 deletions

diff --git a/drivers/base/node.c b/drivers/base/node.c
index 0b0f38c2c7cd..beec80649b33 100644
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -804,20 +804,14 @@ int register_mem_sect_under_node(struct memory_block *mem_blk, void *arg)
 
 /*
  * Unregister memory block device under all nodes that it spans.
+ * Has to be called with mem_sysfs_mutex held (due to unlinked_nodes).
  */
-int unregister_memory_block_under_nodes(struct memory_block *mem_blk)
+void unregister_memory_block_under_nodes(struct memory_block *mem_blk)
 {
-	NODEMASK_ALLOC(nodemask_t, unlinked_nodes, GFP_KERNEL);
 	unsigned long pfn, sect_start_pfn, sect_end_pfn;
+	static nodemask_t unlinked_nodes;
 
-	if (!mem_blk) {
-		NODEMASK_FREE(unlinked_nodes);
-		return -EFAULT;
-	}
-	if (!unlinked_nodes)
-		return -ENOMEM;
-	nodes_clear(*unlinked_nodes);
-
+	nodes_clear(unlinked_nodes);
 	sect_start_pfn = section_nr_to_pfn(mem_blk->start_section_nr);
 	sect_end_pfn = section_nr_to_pfn(mem_blk->end_section_nr);
 	for (pfn = sect_start_pfn; pfn <= sect_end_pfn; pfn++) {
@@ -828,15 +822,13 @@ int unregister_memory_block_under_nodes(struct memory_block *mem_blk)
 			continue;
 		if (!node_online(nid))
 			continue;
-		if (node_test_and_set(nid, *unlinked_nodes))
+		if (node_test_and_set(nid, unlinked_nodes))
 			continue;
 		sysfs_remove_link(&node_devices[nid]->dev.kobj,
 			 kobject_name(&mem_blk->dev.kobj));
 		sysfs_remove_link(&mem_blk->dev.kobj,
 			 kobject_name(&node_devices[nid]->dev.kobj));
 	}
-	NODEMASK_FREE(unlinked_nodes);
-	return 0;
 }
 
 int link_mem_sections(int nid, unsigned long start_pfn, unsigned long end_pfn)
diff --git a/include/linux/node.h b/include/linux/node.h
index 02a29e71b175..548c226966a2 100644
--- a/include/linux/node.h
+++ b/include/linux/node.h
@@ -139,7 +139,7 @@ extern int register_cpu_under_node(unsigned int cpu, unsigned int nid);
 extern int unregister_cpu_under_node(unsigned int cpu, unsigned int nid);
 extern int register_mem_sect_under_node(struct memory_block *mem_blk,
 						void *arg);
-extern int unregister_memory_block_under_nodes(struct memory_block *mem_blk);
+extern void unregister_memory_block_under_nodes(struct memory_block *mem_blk);
 
 extern int register_memory_node_under_compute_node(unsigned int mem_nid,
 						   unsigned int cpu_nid,
@@ -175,9 +175,8 @@ static inline int register_mem_sect_under_node(struct memory_block *mem_blk,
 {
 	return 0;
 }
-static inline int unregister_memory_block_under_nodes(struct memory_block *mem_blk)
+static inline void unregister_memory_block_under_nodes(struct memory_block *mem_blk)
 {
-	return 0;
 }
 
 static inline void register_hugetlbfs_with_node(node_registration_func_t reg,