mm, memory_hotplug: drop CONFIG_MOVABLE_NODE

Commit 20b2f52b73fe ("numa: add CONFIG_MOVABLE_NODE for
movable-dedicated node") has introduced CONFIG_MOVABLE_NODE without a
good explanation on why it is actually useful.

It makes a lot of sense to make movable node semantic opt in but we
already have that because the feature has to be explicitly enabled on
the kernel command line.  A config option on top only makes the
configuration space larger without a good reason.  It also adds an
additional ifdefery that pollutes the code.

Just drop the config option and make it de-facto always enabled.  This
shouldn't introduce any change to the semantic.

Link: http://lkml.kernel.org/r/20170529114141.536-3-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Reza Arbab <arbab@linux.vnet.ibm.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Yasuaki Ishimatsu <yasu.isimatu@gmail.com>
Cc: Xishi Qiu <qiuxishi@huawei.com>
Cc: Kani Toshimitsu <toshi.kani@hpe.com>
Cc: Chen Yucong <slaoub@gmail.com>
Cc: Joonsoo Kim <js1304@gmail.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Daniel Kiper <daniel.kiper@oracle.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

8 files changed, 5 insertions, 62 deletions

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 34ae9663aefd..dd7abbea8188 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2303,8 +2303,11 @@
                         that the amount of memory usable for all allocations
                         is not too small.
 
-        movable_node    [KNL] Boot-time switch to enable the effects
-                        of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
+        movable_node    [KNL] Boot-time switch to make hotplugable memory
+                        NUMA nodes to be movable. This means that the memory
+                        of such nodes will be usable only for movable
+                        allocations which rules out almost all kernel
+                        allocations. Use with caution!
 
         MTD_Partition=  [MTD]
                         Format: <name>,<region-number>,<size>,<offset>
diff --git a/drivers/base/node.c b/drivers/base/node.c
index 6b1ee371ee97..73d39bc58c42 100644
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -639,9 +639,7 @@ static struct node_attr node_state_attr[] = {
 #ifdef CONFIG_HIGHMEM
         [N_HIGH_MEMORY] = _NODE_ATTR(has_high_memory, N_HIGH_MEMORY),
 #endif
-#ifdef CONFIG_MOVABLE_NODE
         [N_MEMORY] = _NODE_ATTR(has_memory, N_MEMORY),
-#endif
         [N_CPU] = _NODE_ATTR(has_cpu, N_CPU),
 };
 
@@ -652,9 +650,7 @@ static struct attribute *node_state_attrs[] = {
 #ifdef CONFIG_HIGHMEM
         &node_state_attr[N_HIGH_MEMORY].attr.attr,
 #endif
-#ifdef CONFIG_MOVABLE_NODE
         &node_state_attr[N_MEMORY].attr.attr,
-#endif
         &node_state_attr[N_CPU].attr.attr,
         NULL
 };
diff --git a/include/linux/memblock.h b/include/linux/memblock.h
index 8098695e5d8d..1199e605d676 100644
--- a/include/linux/memblock.h
+++ b/include/linux/memblock.h
@@ -57,10 +57,8 @@ struct memblock {
 
 extern struct memblock memblock;
 extern int memblock_debug;
-#ifdef CONFIG_MOVABLE_NODE
 /* If movable_node boot option specified */
 extern bool movable_node_enabled;
-#endif /* CONFIG_MOVABLE_NODE */
 
 #ifdef CONFIG_ARCH_DISCARD_MEMBLOCK
 #define __init_memblock __meminit
@@ -169,7 +167,6 @@ void __next_reserved_mem_region(u64 *idx, phys_addr_t *out_start,
              i != (u64)ULLONG_MAX;                                      \
              __next_reserved_mem_region(&i, p_start, p_end))
 
-#ifdef CONFIG_MOVABLE_NODE
 static inline bool memblock_is_hotpluggable(struct memblock_region *m)
 {
         return m->flags & MEMBLOCK_HOTPLUG;
@@ -179,16 +176,6 @@ static inline bool __init_memblock movable_node_is_enabled(void)
 {
         return movable_node_enabled;
 }
-#else
-static inline bool memblock_is_hotpluggable(struct memblock_region *m)
-{
-        return false;
-}
-static inline bool movable_node_is_enabled(void)
-{
-        return false;
-}
-#endif
 
 static inline bool memblock_is_mirror(struct memblock_region *m)
 {
@@ -296,7 +283,6 @@ phys_addr_t memblock_alloc_try_nid(phys_addr_t size, phys_addr_t align, int nid)
 
 phys_addr_t memblock_alloc(phys_addr_t size, phys_addr_t align);
 
-#ifdef CONFIG_MOVABLE_NODE
 /*
  * Set the allocation direction to bottom-up or top-down.
  */
@@ -314,10 +300,6 @@ static inline bool memblock_bottom_up(void)
 {
         return memblock.bottom_up;
 }
-#else
-static inline void __init memblock_set_bottom_up(bool enable) {}
-static inline bool memblock_bottom_up(void) { return false; }
-#endif
 
 /* Flags for memblock_alloc_base() amd __memblock_alloc_base() */
 #define MEMBLOCK_ALLOC_ANYWHERE (~(phys_addr_t)0)
diff --git a/include/linux/nodemask.h b/include/linux/nodemask.h
index f746e44d4046..cf0b91c3ec12 100644
--- a/include/linux/nodemask.h
+++ b/include/linux/nodemask.h
@@ -387,11 +387,7 @@ enum node_states {
 #else
         N_HIGH_MEMORY = N_NORMAL_MEMORY,
 #endif
-#ifdef CONFIG_MOVABLE_NODE
         N_MEMORY,               /* The node has memory(regular, high, movable) */
-#else
-        N_MEMORY = N_HIGH_MEMORY,
-#endif
         N_CPU,          /* The node has one or more cpus */
         NR_NODE_STATES
 };
diff --git a/mm/Kconfig b/mm/Kconfig
index 9870baafb096..857f6ef368d4 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -149,32 +149,6 @@ config NO_BOOTMEM
 config MEMORY_ISOLATION
         bool
 
-config MOVABLE_NODE
-        bool "Enable to assign a node which has only movable memory"
-        depends on HAVE_MEMBLOCK
-        depends on NO_BOOTMEM
-        depends on X86_64 || OF_EARLY_FLATTREE || MEMORY_HOTPLUG
-        depends on NUMA
-        default n
-        help
-          Allow a node to have only movable memory.  Pages used by the kernel,
-          such as direct mapping pages cannot be migrated.  So the corresponding
-          memory device cannot be hotplugged.  This option allows the following
-          two things:
-          - When the system is booting, node full of hotpluggable memory can
-          be arranged to have only movable memory so that the whole node can
-          be hot-removed. (need movable_node boot option specified).
-          - After the system is up, the option allows users to online all the
-          memory of a node as movable memory so that the whole node can be
-          hot-removed.
-
-          Users who don't use the memory hotplug feature are fine with this
-          option on since they don't specify movable_node boot option or they
-          don't online memory as movable.
-
-          Say Y here if you want to hotplug a whole node.
-          Say N here if you want kernel to use memory on all nodes evenly.
-
 #
 # Only be set on architectures that have completely implemented memory hotplug
 # feature. If you are not sure, don't touch it.
diff --git a/mm/memblock.c b/mm/memblock.c
index 7b8a5db76a2f..41eaeebb03dc 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -54,9 +54,7 @@ struct memblock memblock __initdata_memblock = {
 };
 
 int memblock_debug __initdata_memblock;
-#ifdef CONFIG_MOVABLE_NODE
 bool movable_node_enabled __initdata_memblock = false;
-#endif
 static bool system_has_some_mirror __initdata_memblock = false;
 static int memblock_can_resize __initdata_memblock;
 static int memblock_memory_in_slab __initdata_memblock = 0;
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 937319899e61..0dc8cf0a59d7 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1572,11 +1572,7 @@ check_pages_isolated(unsigned long start_pfn, unsigned long end_pfn)
 
 static int __init cmdline_parse_movable_node(char *p)
 {
-#ifdef CONFIG_MOVABLE_NODE
         movable_node_enabled = true;
-#else
-        pr_warn("movable_node option not supported\n");
-#endif
         return 0;
 }
 early_param("movable_node", cmdline_parse_movable_node);
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index a35add8d7c0b..bd65b60939b6 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -113,9 +113,7 @@ nodemask_t node_states[NR_NODE_STATES] __read_mostly = {
 #ifdef CONFIG_HIGHMEM
         [N_HIGH_MEMORY] = { { [0] = 1UL } },
 #endif
-#ifdef CONFIG_MOVABLE_NODE
         [N_MEMORY] = { { [0] = 1UL } },
-#endif
         [N_CPU] = { { [0] = 1UL } },
 #endif  /* NUMA */
 };