mm: show node to memory section relationship with symlinks in sysfs

Show node to memory section relationship with symlinks in sysfs

Add /sys/devices/system/node/nodeX/memoryY symlinks for all
the memory sections located on nodeX.  For example:
/sys/devices/system/node/node1/memory135 -> ../../memory/memory135
indicates that memory section 135 resides on node1.

Also revises documentation to cover this change as well as updating
Documentation/ABI/testing/sysfs-devices-memory to include descriptions
of memory hotremove files 'phys_device', 'phys_index', and 'state'
that were previously not described there.

In addition to it always being a good policy to provide users with
the maximum possible amount of physical location information for
resources that can be hot-added and/or hot-removed, the following
are some (but likely not all) of the user benefits provided by
this change.
Immediate:
  - Provides information needed to determine the specific node
    on which a defective DIMM is located.  This will reduce system
    downtime when the node or defective DIMM is swapped out.
  - Prevents unintended onlining of a memory section that was
    previously offlined due to a defective DIMM.  This could happen
    during node hot-add when the user or node hot-add assist script
    onlines _all_ offlined sections due to user or script inability
    to identify the specific memory sections located on the hot-added
    node.  The consequences of reintroducing the defective memory
    could be ugly.
  - Provides information needed to vary the amount and distribution
    of memory on specific nodes for testing or debugging purposes.
Future:
  - Will provide information needed to identify the memory
    sections that need to be offlined prior to physical removal
    of a specific node.

Symlink creation during boot was tested on 2-node x86_64, 2-node
ppc64, and 2-node ia64 systems.  Symlink creation during physical
memory hot-add tested on a 2-node x86_64 system.

Signed-off-by: Gary Hade <garyhade@us.ibm.com>
Signed-off-by: Badari Pulavarty <pbadari@us.ibm.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 13 insertions, 6 deletions

diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index 5260e9e0df48..989429cfed88 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -347,8 +347,9 @@ static inline int memory_probe_init(void)
  * section belongs to...
  */
 
-static int add_memory_block(unsigned long node_id, struct mem_section *section,
-                     unsigned long state, int phys_device)
+static int add_memory_block(int nid, struct mem_section *section,
+                        unsigned long state, int phys_device,
+                        enum mem_add_context context)
 {
         struct memory_block *mem = kzalloc(sizeof(*mem), GFP_KERNEL);
         int ret = 0;
@@ -370,6 +371,10 @@ static int add_memory_block(unsigned long node_id, struct mem_section *section,
                 ret = mem_create_simple_file(mem, phys_device);
         if (!ret)
                 ret = mem_create_simple_file(mem, removable);
+        if (!ret) {
+                if (context == HOTPLUG)
+                        ret = register_mem_sect_under_node(mem, nid);
+        }
 
         return ret;
 }
@@ -382,7 +387,7 @@ static int add_memory_block(unsigned long node_id, struct mem_section *section,
  *
  * This could be made generic for all sysdev classes.
  */
-static struct memory_block *find_memory_block(struct mem_section *section)
+struct memory_block *find_memory_block(struct mem_section *section)
 {
         struct kobject *kobj;
         struct sys_device *sysdev;
@@ -411,6 +416,7 @@ int remove_memory_block(unsigned long node_id, struct mem_section *section,
         struct memory_block *mem;
 
         mem = find_memory_block(section);
+        unregister_mem_sect_under_nodes(mem);
         mem_remove_simple_file(mem, phys_index);
         mem_remove_simple_file(mem, state);
         mem_remove_simple_file(mem, phys_device);
@@ -424,9 +430,9 @@ int remove_memory_block(unsigned long node_id, struct mem_section *section,
  * need an interface for the VM to add new memory regions,
  * but without onlining it.
  */
-int register_new_memory(struct mem_section *section)
+int register_new_memory(int nid, struct mem_section *section)
 {
-        return add_memory_block(0, section, MEM_OFFLINE, 0);
+        return add_memory_block(nid, section, MEM_OFFLINE, 0, HOTPLUG);
 }
 
 int unregister_memory_section(struct mem_section *section)
@@ -458,7 +464,8 @@ int __init memory_dev_init(void)
         for (i = 0; i < NR_MEM_SECTIONS; i++) {
                 if (!present_section_nr(i))
                         continue;
-                err = add_memory_block(0, __nr_to_section(i), MEM_ONLINE, 0);
+                err = add_memory_block(0, __nr_to_section(i), MEM_ONLINE,
+                                        0, BOOT);
                 if (!ret)
                         ret = err;
         }