[PATCH 7/7,v10] NUMA Hotplug Emulator: Implement per-node add_memory debugfs interface

["Zhang, Yang Z" <yang.z.zhang@intel.com>]

Add add_memory interface to support to memory hotplug emulation for each online
node under debugfs. The reserved memory can be added into desired node with
this interface.

The layout on debugfs:
        node_hotplug/node0/add_memory
        node_hotplug/node1/add_memory
        node_hotplug/node2/add_memory
        ...

Add a memory section(128M) to node 3(boots with mem=1024m)

        echo 0x40000000 > node_hotplug/node3/add_memory

CC: David Rientjes <rientjes@google.com>
CC: Dave Hansen <dave@linux.vnet.ibm.com>
Signed-off-by: Haicheng Li <haicheng.li@intel.com>
Signed-off-by: Shaohui Zheng <shaohui.zheng@intel.com>
Signed-off-by: Yang Zhang <yang.z.zhang@Intel.com>
---
 Documentation/memory-hotplug.txt |   24 ++++++++++++
 mm/memory_hotplug.c              |   77 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 101 insertions(+), 0 deletions(-)

diff --git a/Documentation/memory-hotplug.txt linux-hpe4/Documentation/memory-hotplug.txt
index bc8c99e..9fa8fc7 100644
--- a/Documentation/memory-hotplug.txt
+++ linux-hpe4/Documentation/memory-hotplug.txt
@@ -19,6 +19,7 @@ be changed often.
   4.1 Hardware(Firmware) Support
   4.2 Notify memory hot-add event by hand
   4.3 Node hotplug emulation
+  4.4 Memory hotplug emulation
 5. Logical Memory hot-add phase
   5.1. State of memory
   5.2. How to online memory
@@ -254,6 +255,29 @@ Where "size" can be represented in megabytes or gigabytes (for example,
 Once the new node has been added, it is possible to online the memory by
 toggling the "state" of its memory section(s) as described in section 5.1.

+4.4 Memory hotplug emulation
+------------
+With debugfs, it is possible to test memory hotplug with software method, we
+can add memory section to desired node with add_memory interface. It is a much
+more powerful interface than "probe" described in section 4.2.
+
+There is an add_memory interface for each online node at the debugfs mount
+point.
+       mem_hotplug/node0/add_memory
+       mem_hotplug/node1/add_memory
+       mem_hotplug/node2/add_memory
+       ...
+
+Add a memory section(128M) to node 3(boots with mem=1024m)
+
+       echo 0x40000000 > mem_hotplug/node3/add_memory
+
+And more we make it friendly, it is possible to add memory to do
+
+       echo 1024m > mem_hotplug/node3/add_memory
+
+Once the new memory section has been added, it is possible to online the memory
+by toggling the "state" described in section 5.1.

 ------------------------------
 5. Logical Memory hot-add phase
diff --git a/mm/memory_hotplug.c linux-hpe4/mm/memory_hotplug.c
index f0be4b4..0193e96 100644
--- a/mm/memory_hotplug.c
+++ linux-hpe4/mm/memory_hotplug.c
@@ -942,6 +942,81 @@ static struct dentry *node_hp_debug_root;
 extern char *emu_cmdline;
 extern int emu_nid_to_phys[MAX_NUMNODES];

+#ifdef CONFIG_ARCH_MEMORY_PROBE
+
+static ssize_t add_memory_store(struct file *file, const char __user *buf,
+                               size_t count, loff_t *ppos)
+{
+       u64 phys_addr = 0;
+       int nid = file->private_data - NULL;
+       int ret;
+
+       printk(KERN_INFO "Add a memory section to node: %d.\n", nid);
+       phys_addr = simple_strtoull(buf, NULL, 0);
+
+       ret = add_memory(nid, phys_addr, PAGES_PER_SECTION << PAGE_SHIFT);
+       if (ret)
+               count = ret;
+
+       return count;
+}
+
+static int add_memory_open(struct inode *inode, struct file *file)
+{
+       file->private_data = inode->i_private;
+       return 0;
+}
+
+static const struct file_operations add_memory_file_ops = {
+       .open           = add_memory_open,
+       .write          = add_memory_store,
+       .llseek         = generic_file_llseek,
+};
+
+/*
+ * Create add_memory debugfs entry under specified node
+ */
+static int debugfs_create_add_memory_entry(int nid)
+{
+       char buf[32];
+       static struct dentry *node_debug_root;
+
+       snprintf(buf, sizeof(buf), "node%d", nid);
+       node_debug_root = debugfs_create_dir(buf, memhp_debug_root);
+       if (!node_debug_root)
+               return -ENOMEM;
+
+       /* the nid information was represented by the offset of pointer(NULL+nid) */
+       if (!debugfs_create_file("add_memory", S_IWUSR, node_debug_root,
+                       NULL + nid, &add_memory_file_ops))
+               return -ENOMEM;
+
+       return 0;
+}
+
+static int __init memory_debug_init(void)
+{
+       int nid;
+
+       if (!memhp_debug_root)
+               memhp_debug_root = debugfs_create_dir("mem_hotplug", NULL);
+       if (!memhp_debug_root)
+               return -ENOMEM;
+
+       for_each_online_node(nid)
+                debugfs_create_add_memory_entry(nid);
+
+       return 0;
+}
+
+module_init(memory_debug_init);
+#else
+static debugfs_create_add_memory_entry(int nid)
+{
+       return 0;
+}
+#endif /* CONFIG_ARCH_MEMORY_PROBE */
+
 static ssize_t add_node_store(struct file *file, const char __user *buf,
                                size_t count, loff_t *ppos)
 {
@@ -973,6 +1048,8 @@ static ssize_t add_node_store(struct file *file, const char __user *buf,
        emu_nid_to_phys[nid] = nid;

        ret = add_memory(nid, start, size);
+
+       debugfs_create_add_memory_entry(nid);
        return ret ? ret : count;
 }

--
1.7.1.1
--
best regards
yang


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