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>

14 files changed, 209 insertions, 25 deletions

diff --git a/Documentation/ABI/testing/sysfs-devices-memory b/Documentation/ABI/testing/sysfs-devices-memory
index 7a16fe1e2270..9fe91c02ee40 100644
--- a/Documentation/ABI/testing/sysfs-devices-memory
+++ b/Documentation/ABI/testing/sysfs-devices-memory
@@ -6,7 +6,6 @@ Description:
                 internal state of the kernel memory blocks. Files could be
                 added or removed dynamically to represent hot-add/remove
                 operations.
-
 Users:          hotplug memory add/remove tools
                 https://w3.opensource.ibm.com/projects/powerpc-utils/
 
@@ -19,6 +18,56 @@ Description:
                 This is useful for a user-level agent to determine
                 identify removable sections of the memory before attempting
                 potentially expensive hot-remove memory operation
+Users:          hotplug memory remove tools
+                https://w3.opensource.ibm.com/projects/powerpc-utils/
+
+What:           /sys/devices/system/memory/memoryX/phys_device
+Date:           September 2008
+Contact:        Badari Pulavarty <pbadari@us.ibm.com>
+Description:
+                The file /sys/devices/system/memory/memoryX/phys_device
+                is read-only and is designed to show the name of physical
+                memory device.  Implementation is currently incomplete.
 
+What:           /sys/devices/system/memory/memoryX/phys_index
+Date:           September 2008
+Contact:        Badari Pulavarty <pbadari@us.ibm.com>
+Description:
+                The file /sys/devices/system/memory/memoryX/phys_index
+                is read-only and contains the section ID in hexadecimal
+                which is equivalent to decimal X contained in the
+                memory section directory name.
+
+What:           /sys/devices/system/memory/memoryX/state
+Date:           September 2008
+Contact:        Badari Pulavarty <pbadari@us.ibm.com>
+Description:
+                The file /sys/devices/system/memory/memoryX/state
+                is read-write.  When read, it's contents show the
+                online/offline state of the memory section.  When written,
+                root can toggle the the online/offline state of a removable
+                memory section (see removable file description above)
+                using the following commands.
+                # echo online > /sys/devices/system/memory/memoryX/state
+                # echo offline > /sys/devices/system/memory/memoryX/state
+
+                For example, if /sys/devices/system/memory/memory22/removable
+                contains a value of 1 and
+                /sys/devices/system/memory/memory22/state contains the
+                string "online" the following command can be executed by
+                by root to offline that section.
+                # echo offline > /sys/devices/system/memory/memory22/state
 Users:          hotplug memory remove tools
                 https://w3.opensource.ibm.com/projects/powerpc-utils/
+
+What:           /sys/devices/system/node/nodeX/memoryY
+Date:           September 2008
+Contact:        Gary Hade <garyhade@us.ibm.com>
+Description:
+                When CONFIG_NUMA is enabled
+                /sys/devices/system/node/nodeX/memoryY is a symbolic link that
+                points to the corresponding /sys/devices/system/memory/memoryY
+                memory section directory.  For example, the following symbolic
+                link is created for memory section 9 on node0.
+                /sys/devices/system/node/node0/memory9 -> ../../memory/memory9
+
diff --git a/Documentation/memory-hotplug.txt b/Documentation/memory-hotplug.txt
index 168117bd6ee8..4c2ecf537a4a 100644
--- a/Documentation/memory-hotplug.txt
+++ b/Documentation/memory-hotplug.txt
@@ -124,7 +124,7 @@ config options.
     This option can be kernel module too.
 
 --------------------------------
-3 sysfs files for memory hotplug
+4 sysfs files for memory hotplug
 --------------------------------
 All sections have their device information under /sys/devices/system/memory as
 
@@ -138,11 +138,12 @@ For example, assume 1GiB section size. A device for a memory starting at
 (0x100000000 / 1Gib = 4)
 This device covers address range [0x100000000 ... 0x140000000)
 
-Under each section, you can see 3 files.
+Under each section, you can see 4 files.
 
 /sys/devices/system/memory/memoryXXX/phys_index
 /sys/devices/system/memory/memoryXXX/phys_device
 /sys/devices/system/memory/memoryXXX/state
+/sys/devices/system/memory/memoryXXX/removable
 
 'phys_index' : read-only and contains section id, same as XXX.
 'state'      : read-write
@@ -150,10 +151,20 @@ Under each section, you can see 3 files.
                at write: user can specify "online", "offline" command
 'phys_device': read-only: designed to show the name of physical memory device.
                This is not well implemented now.
+'removable'  : read-only: contains an integer value indicating
+               whether the memory section is removable or not
+               removable.  A value of 1 indicates that the memory
+               section is removable and a value of 0 indicates that
+               it is not removable.
 
 NOTE:
   These directories/files appear after physical memory hotplug phase.
 
+If CONFIG_NUMA is enabled the
+/sys/devices/system/memory/memoryXXX memory section
+directories can also be accessed via symbolic links located in
+the /sys/devices/system/node/node* directories.  For example:
+/sys/devices/system/node/node0/memory9 -> ../../memory/memory9
 
 --------------------------------
 4. Physical memory hot-add phase
@@ -365,7 +376,6 @@ node if necessary.
   - allowing memory hot-add to ZONE_MOVABLE. maybe we need some switch like
     sysctl or new control file.
   - showing memory section and physical device relationship.
-  - showing memory section and node relationship (maybe good for NUMA)
   - showing memory section is under ZONE_MOVABLE or not
   - test and make it better memory offlining.
   - support HugeTLB page migration and offlining.
diff --git a/arch/ia64/mm/init.c b/arch/ia64/mm/init.c
index 054bcd9439aa..56e12903973c 100644
--- a/arch/ia64/mm/init.c
+++ b/arch/ia64/mm/init.c
@@ -692,7 +692,7 @@ int arch_add_memory(int nid, u64 start, u64 size)
         pgdat = NODE_DATA(nid);
 
         zone = pgdat->node_zones + ZONE_NORMAL;
-        ret = __add_pages(zone, start_pfn, nr_pages);
+        ret = __add_pages(nid, zone, start_pfn, nr_pages);
 
         if (ret)
                 printk("%s: Problem encountered in __add_pages() as ret=%d\n",
diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index 53b06ebb3f2f..f00f09a77f12 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -132,7 +132,7 @@ int arch_add_memory(int nid, u64 start, u64 size)
         /* this should work for most non-highmem platforms */
         zone = pgdata->node_zones;
 
-        return __add_pages(zone, start_pfn, nr_pages);
+        return __add_pages(nid, zone, start_pfn, nr_pages);
 }
 #endif /* CONFIG_MEMORY_HOTPLUG */
 
diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
index 158b0d6d7046..f0258ca3b17e 100644
--- a/arch/s390/mm/init.c
+++ b/arch/s390/mm/init.c
@@ -183,7 +183,7 @@ int arch_add_memory(int nid, u64 start, u64 size)
         rc = vmem_add_mapping(start, size);
         if (rc)
                 return rc;
-        rc = __add_pages(zone, PFN_DOWN(start), PFN_DOWN(size));
+        rc = __add_pages(nid, zone, PFN_DOWN(start), PFN_DOWN(size));
         if (rc)
                 vmem_remove_mapping(start, size);
         return rc;
diff --git a/arch/sh/mm/init.c b/arch/sh/mm/init.c
index 6cbef8caeb56..3edf297c829b 100644
--- a/arch/sh/mm/init.c
+++ b/arch/sh/mm/init.c
@@ -311,7 +311,8 @@ int arch_add_memory(int nid, u64 start, u64 size)
         pgdat = NODE_DATA(nid);
 
         /* We only have ZONE_NORMAL, so this is easy.. */
-        ret = __add_pages(pgdat->node_zones + ZONE_NORMAL, start_pfn, nr_pages);
+        ret = __add_pages(nid, pgdat->node_zones + ZONE_NORMAL,
+                                start_pfn, nr_pages);
         if (unlikely(ret))
                 printk("%s: Failed, __add_pages() == %d\n", __func__, ret);
 
diff --git a/arch/x86/mm/init_32.c b/arch/x86/mm/init_32.c
index f99a6c6c432e..544d724caeee 100644
--- a/arch/x86/mm/init_32.c
+++ b/arch/x86/mm/init_32.c
@@ -1079,7 +1079,7 @@ int arch_add_memory(int nid, u64 start, u64 size)
         unsigned long start_pfn = start >> PAGE_SHIFT;
         unsigned long nr_pages = size >> PAGE_SHIFT;
 
-        return __add_pages(zone, start_pfn, nr_pages);
+        return __add_pages(nid, zone, start_pfn, nr_pages);
 }
 #endif
 
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 9f7a0d24d42a..54c437e96541 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -857,7 +857,7 @@ int arch_add_memory(int nid, u64 start, u64 size)
         if (last_mapped_pfn > max_pfn_mapped)
                 max_pfn_mapped = last_mapped_pfn;
 
-        ret = __add_pages(zone, start_pfn, nr_pages);
+        ret = __add_pages(nid, zone, start_pfn, nr_pages);
         WARN_ON_ONCE(ret);
 
         return ret;
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;
         }
diff --git a/drivers/base/node.c b/drivers/base/node.c
index 91636cd8b6c9..43fa90b837ee 100644
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -6,6 +6,7 @@
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/mm.h>
+#include <linux/memory.h>
 #include <linux/node.h>
 #include <linux/hugetlb.h>
 #include <linux/cpumask.h>
@@ -248,6 +249,105 @@ int unregister_cpu_under_node(unsigned int cpu, unsigned int nid)
         return 0;
 }
 
+#ifdef CONFIG_MEMORY_HOTPLUG_SPARSE
+#define page_initialized(page)  (page->lru.next)
+
+static int get_nid_for_pfn(unsigned long pfn)
+{
+        struct page *page;
+
+        if (!pfn_valid_within(pfn))
+                return -1;
+        page = pfn_to_page(pfn);
+        if (!page_initialized(page))
+                return -1;
+        return pfn_to_nid(pfn);
+}
+
+/* register memory section under specified node if it spans that node */
+int register_mem_sect_under_node(struct memory_block *mem_blk, int nid)
+{
+        unsigned long pfn, sect_start_pfn, sect_end_pfn;
+
+        if (!mem_blk)
+                return -EFAULT;
+        if (!node_online(nid))
+                return 0;
+        sect_start_pfn = section_nr_to_pfn(mem_blk->phys_index);
+        sect_end_pfn = sect_start_pfn + PAGES_PER_SECTION - 1;
+        for (pfn = sect_start_pfn; pfn <= sect_end_pfn; pfn++) {
+                int page_nid;
+
+                page_nid = get_nid_for_pfn(pfn);
+                if (page_nid < 0)
+                        continue;
+                if (page_nid != nid)
+                        continue;
+                return sysfs_create_link_nowarn(&node_devices[nid].sysdev.kobj,
+                                        &mem_blk->sysdev.kobj,
+                                        kobject_name(&mem_blk->sysdev.kobj));
+        }
+        /* mem section does not span the specified node */
+        return 0;
+}
+
+/* unregister memory section under all nodes that it spans */
+int unregister_mem_sect_under_nodes(struct memory_block *mem_blk)
+{
+        nodemask_t unlinked_nodes;
+        unsigned long pfn, sect_start_pfn, sect_end_pfn;
+
+        if (!mem_blk)
+                return -EFAULT;
+        nodes_clear(unlinked_nodes);
+        sect_start_pfn = section_nr_to_pfn(mem_blk->phys_index);
+        sect_end_pfn = sect_start_pfn + PAGES_PER_SECTION - 1;
+        for (pfn = sect_start_pfn; pfn <= sect_end_pfn; pfn++) {
+                unsigned int nid;
+
+                nid = get_nid_for_pfn(pfn);
+                if (nid < 0)
+                        continue;
+                if (!node_online(nid))
+                        continue;
+                if (node_test_and_set(nid, unlinked_nodes))
+                        continue;
+                sysfs_remove_link(&node_devices[nid].sysdev.kobj,
+                         kobject_name(&mem_blk->sysdev.kobj));
+        }
+        return 0;
+}
+
+static int link_mem_sections(int nid)
+{
+        unsigned long start_pfn = NODE_DATA(nid)->node_start_pfn;
+        unsigned long end_pfn = start_pfn + NODE_DATA(nid)->node_spanned_pages;
+        unsigned long pfn;
+        int err = 0;
+
+        for (pfn = start_pfn; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
+                unsigned long section_nr = pfn_to_section_nr(pfn);
+                struct mem_section *mem_sect;
+                struct memory_block *mem_blk;
+                int ret;
+
+                if (!present_section_nr(section_nr))
+                        continue;
+                mem_sect = __nr_to_section(section_nr);
+                mem_blk = find_memory_block(mem_sect);
+                ret = register_mem_sect_under_node(mem_blk, nid);
+                if (!err)
+                        err = ret;
+
+                /* discard ref obtained in find_memory_block() */
+                kobject_put(&mem_blk->sysdev.kobj);
+        }
+        return err;
+}
+#else
+static int link_mem_sections(int nid) { return 0; }
+#endif /* CONFIG_MEMORY_HOTPLUG_SPARSE */
+
 int register_one_node(int nid)
 {
         int error = 0;
@@ -267,6 +367,9 @@ int register_one_node(int nid)
                         if (cpu_to_node(cpu) == nid)
                                 register_cpu_under_node(cpu, nid);
                 }
+
+                /* link memory sections under this node */
+                error = link_mem_sections(nid);
         }
 
         return error;
diff --git a/include/linux/memory.h b/include/linux/memory.h
index 36c82c9e6ea7..3fdc10806d31 100644
--- a/include/linux/memory.h
+++ b/include/linux/memory.h
@@ -79,14 +79,14 @@ static inline int memory_notify(unsigned long val, void *v)
 #else
 extern int register_memory_notifier(struct notifier_block *nb);
 extern void unregister_memory_notifier(struct notifier_block *nb);
-extern int register_new_memory(struct mem_section *);
+extern int register_new_memory(int, struct mem_section *);
 extern int unregister_memory_section(struct mem_section *);
 extern int memory_dev_init(void);
 extern int remove_memory_block(unsigned long, struct mem_section *, int);
 extern int memory_notify(unsigned long val, void *v);
+extern struct memory_block *find_memory_block(struct mem_section *);
 #define CONFIG_MEM_BLOCK_SIZE   (PAGES_PER_SECTION<<PAGE_SHIFT)
-
-
+enum mem_add_context { BOOT, HOTPLUG };
 #endif /* CONFIG_MEMORY_HOTPLUG_SPARSE */
 
 #ifdef CONFIG_MEMORY_HOTPLUG
diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index 763ba81fc0f0..d95f72e79b82 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -72,7 +72,7 @@ extern void __offline_isolated_pages(unsigned long, unsigned long);
 extern int offline_pages(unsigned long, unsigned long, unsigned long);
 
 /* reasonably generic interface to expand the physical pages in a zone  */
-extern int __add_pages(struct zone *zone, unsigned long start_pfn,
+extern int __add_pages(int nid, struct zone *zone, unsigned long start_pfn,
         unsigned long nr_pages);
 extern int __remove_pages(struct zone *zone, unsigned long start_pfn,
         unsigned long nr_pages);
diff --git a/include/linux/node.h b/include/linux/node.h
index bc001bc225c3..681a697b9a86 100644
--- a/include/linux/node.h
+++ b/include/linux/node.h
@@ -26,6 +26,7 @@ struct node {
         struct sys_device       sysdev;
 };
 
+struct memory_block;
 extern struct node node_devices[];
 
 extern int register_node(struct node *, int, struct node *);
@@ -35,6 +36,9 @@ extern int register_one_node(int nid);
 extern void unregister_one_node(int nid);
 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,
+                                                int nid);
+extern int unregister_mem_sect_under_nodes(struct memory_block *mem_blk);
 #else
 static inline int register_one_node(int nid)
 {
@@ -52,6 +56,15 @@ static inline int unregister_cpu_under_node(unsigned int cpu, unsigned int nid)
 {
         return 0;
 }
+static inline int register_mem_sect_under_node(struct memory_block *mem_blk,
+                                                        int nid)
+{
+        return 0;
+}
+static inline int unregister_mem_sect_under_nodes(struct memory_block *mem_blk)
+{
+        return 0;
+}
 #endif
 
 #define to_node(sys_device) container_of(sys_device, struct node, sysdev)
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index b17371185468..2ba38bc07b47 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -216,7 +216,8 @@ static int __meminit __add_zone(struct zone *zone, unsigned long phys_start_pfn)
         return 0;
 }
 
-static int __meminit __add_section(struct zone *zone, unsigned long phys_start_pfn)
+static int __meminit __add_section(int nid, struct zone *zone,
+                                        unsigned long phys_start_pfn)
 {
         int nr_pages = PAGES_PER_SECTION;
         int ret;
@@ -234,7 +235,7 @@ static int __meminit __add_section(struct zone *zone, unsigned long phys_start_p
         if (ret < 0)
                 return ret;
 
-        return register_new_memory(__pfn_to_section(phys_start_pfn));
+        return register_new_memory(nid, __pfn_to_section(phys_start_pfn));
 }
 
 #ifdef CONFIG_SPARSEMEM_VMEMMAP
@@ -273,8 +274,8 @@ static int __remove_section(struct zone *zone, struct mem_section *ms)
  * call this function after deciding the zone to which to
  * add the new pages.
  */
-int __ref __add_pages(struct zone *zone, unsigned long phys_start_pfn,
-                 unsigned long nr_pages)
+int __ref __add_pages(int nid, struct zone *zone, unsigned long phys_start_pfn,
+                        unsigned long nr_pages)
 {
         unsigned long i;
         int err = 0;
@@ -284,7 +285,7 @@ int __ref __add_pages(struct zone *zone, unsigned long phys_start_pfn,
         end_sec = pfn_to_section_nr(phys_start_pfn + nr_pages - 1);
 
         for (i = start_sec; i <= end_sec; i++) {
-                err = __add_section(zone, i << PFN_SECTION_SHIFT);
+                err = __add_section(nid, zone, i << PFN_SECTION_SHIFT);
 
                 /*
                  * EEXIST is finally dealt with by ioresource collision