memory-hotplug: add automatic onlining policy for the newly added memory

Currently, all newly added memory blocks remain in 'offline' state
unless someone onlines them, some linux distributions carry special udev
rules like:

  SUBSYSTEM=="memory", ACTION=="add", ATTR{state}=="offline", ATTR{state}="online"

to make this happen automatically.  This is not a great solution for
virtual machines where memory hotplug is being used to address high
memory pressure situations as such onlining is slow and a userspace
process doing this (udev) has a chance of being killed by the OOM killer
as it will probably require to allocate some memory.

Introduce default policy for the newly added memory blocks in
/sys/devices/system/memory/auto_online_blocks file with two possible
values: "offline" which preserves the current behavior and "online"
which causes all newly added memory blocks to go online as soon as
they're added.  The default is "offline".

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Daniel Kiper <daniel.kiper@oracle.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Tang Chen <tangchen@cn.fujitsu.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Xishi Qiu <qiuxishi@huawei.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Kay Sievers <kay@vrfy.org>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/Documentation/memory-hotplug.txt b/Documentation/memory-hotplug.txt
index ce2cfcf35c27a0d0972547e82f61fbc38c85b5ab..443f4b44ad97cddc2d8b645c29a55ff88573f864 100644 (file)
--- a/Documentation/memory-hotplug.txt
+++ b/Documentation/memory-hotplug.txt
@@ -256,10 +256,27 @@ If the memory block is offline, you'll read "offline".
 
 5.2. How to online memory
 ------------
-Even if the memory is hot-added, it is not at ready-to-use state.
-For using newly added memory, you have to "online" the memory block.
+When the memory is hot-added, the kernel decides whether or not to "online"
+it according to the policy which can be read from "auto_online_blocks" file:
 
-For onlining, you have to write "online" to the memory block's state file as:
+% cat /sys/devices/system/memory/auto_online_blocks
+
+The default is "offline" which means the newly added memory is not in a
+ready-to-use state and you have to "online" the newly added memory blocks
+manually. Automatic onlining can be requested by writing "online" to
+"auto_online_blocks" file:
+
+% echo online > /sys/devices/system/memory/auto_online_blocks
+
+This sets a global policy and impacts all memory blocks that will subsequently
+be hotplugged. Currently offline blocks keep their state. It is possible, under
+certain circumstances, that some memory blocks will be added but will fail to
+online. User space tools can check their "state" files
+(/sys/devices/system/memory/memoryXXX/state) and try to online them manually.
+
+If the automatic onlining wasn't requested, failed, or some memory block was
+offlined it is possible to change the individual block's state by writing to the
+"state" file:
 
 % echo online > /sys/devices/system/memory/memoryXXX/state
 

diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index 213456c2b1236a6eb4949155f087a8d139c5aa4e..f46dba8b7092e305ca6e7b404bbf7a2ef8ce2a12 100644 (file)
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -251,7 +251,7 @@ memory_block_action(unsigned long phys_index, unsigned long action, int online_t
        return ret;
 }
 
-static int memory_block_change_state(struct memory_block *mem,
+int memory_block_change_state(struct memory_block *mem,
                unsigned long to_state, unsigned long from_state_req)
 {
        int ret = 0;
@@ -438,6 +438,37 @@ print_block_size(struct device *dev, struct device_attribute *attr,
 
 static DEVICE_ATTR(block_size_bytes, 0444, print_block_size, NULL);
 
+/*
+ * Memory auto online policy.
+ */
+
+static ssize_t
+show_auto_online_blocks(struct device *dev, struct device_attribute *attr,
+                       char *buf)
+{
+       if (memhp_auto_online)
+               return sprintf(buf, "online\n");
+       else
+               return sprintf(buf, "offline\n");
+}
+
+static ssize_t
+store_auto_online_blocks(struct device *dev, struct device_attribute *attr,
+                        const char *buf, size_t count)
+{
+       if (sysfs_streq(buf, "online"))
+               memhp_auto_online = true;
+       else if (sysfs_streq(buf, "offline"))
+               memhp_auto_online = false;
+       else
+               return -EINVAL;
+
+       return count;
+}
+
+static DEVICE_ATTR(auto_online_blocks, 0644, show_auto_online_blocks,
+                  store_auto_online_blocks);
+
 /*
  * Some architectures will have custom drivers to do this, and
  * will not need to do it from userspace.  The fake hot-add code
@@ -746,6 +777,7 @@ static struct attribute *memory_root_attrs[] = {
 #endif
 
        &dev_attr_block_size_bytes.attr,
+       &dev_attr_auto_online_blocks.attr,
        NULL
 };
 

diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index dc4305b407bf6756791ec9b31e7929c1fe5c3ca8..e6058debd01bbfd7924e75a88b197164a03ce290 100644 (file)
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -338,7 +338,7 @@ static enum bp_state reserve_additional_memory(void)
        }
 #endif
 
-       rc = add_memory_resource(nid, resource);
+       rc = add_memory_resource(nid, resource, false);
        if (rc) {
                pr_warn("Cannot add additional memory (%i)\n", rc);
                goto err;

diff --git a/include/linux/memory.h b/include/linux/memory.h
index 8b8d8d12348e59219dbbce03c22a749a49368deb..82730adba950ed196bb7006fa953704393f6578e 100644 (file)
--- a/include/linux/memory.h
+++ b/include/linux/memory.h
@@ -109,6 +109,9 @@ extern void unregister_memory_notifier(struct notifier_block *nb);
 extern int register_memory_isolate_notifier(struct notifier_block *nb);
 extern void unregister_memory_isolate_notifier(struct notifier_block *nb);
 extern int register_new_memory(int, struct mem_section *);
+extern int memory_block_change_state(struct memory_block *mem,
+                                    unsigned long to_state,
+                                    unsigned long from_state_req);
 #ifdef CONFIG_MEMORY_HOTREMOVE
 extern int unregister_memory_section(struct mem_section *);
 #endif

diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index 43405992d0277367eb55afeb847745acc09ed968..769d768705509b285f69cc968a9a1606fbcce1b5 100644 (file)
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -99,6 +99,8 @@ extern void __online_page_free(struct page *page);
 
 extern int try_online_node(int nid);
 
+extern bool memhp_auto_online;
+
 #ifdef CONFIG_MEMORY_HOTREMOVE
 extern bool is_pageblock_removable_nolock(struct page *page);
 extern int arch_remove_memory(u64 start, u64 size);
@@ -267,7 +269,7 @@ static inline void remove_memory(int nid, u64 start, u64 size) {}
 extern int walk_memory_range(unsigned long start_pfn, unsigned long end_pfn,
                void *arg, int (*func)(struct memory_block *, void *));
 extern int add_memory(int nid, u64 start, u64 size);
-extern int add_memory_resource(int nid, struct resource *resource);
+extern int add_memory_resource(int nid, struct resource *resource, bool online);
 extern int zone_for_memory(int nid, u64 start, u64 size, int zone_default,
                bool for_device);
 extern int arch_add_memory(int nid, u64 start, u64 size, bool for_device);

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 979b18cbd343e3422d5b4ccb86d1fab2bb1090e2..484e86761b3e79dba76de62ba2a3ae5c7386e631 100644 (file)
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -77,6 +77,9 @@ static struct {
 #define memhp_lock_acquire()      lock_map_acquire(&mem_hotplug.dep_map)
 #define memhp_lock_release()      lock_map_release(&mem_hotplug.dep_map)
 
+bool memhp_auto_online;
+EXPORT_SYMBOL_GPL(memhp_auto_online);
+
 void get_online_mems(void)
 {
        might_sleep();
@@ -1261,8 +1264,13 @@ int zone_for_memory(int nid, u64 start, u64 size, int zone_default,
        return zone_default;
 }
 
+static int online_memory_block(struct memory_block *mem, void *arg)
+{
+       return memory_block_change_state(mem, MEM_ONLINE, MEM_OFFLINE);
+}
+
 /* we are OK calling __meminit stuff here - we have CONFIG_MEMORY_HOTPLUG */
-int __ref add_memory_resource(int nid, struct resource *res)
+int __ref add_memory_resource(int nid, struct resource *res, bool online)
 {
        u64 start, size;
        pg_data_t *pgdat = NULL;
@@ -1322,6 +1330,11 @@ int __ref add_memory_resource(int nid, struct resource *res)
        /* create new memmap entry */
        firmware_map_add_hotplug(start, start + size, "System RAM");
 
+       /* online pages if requested */
+       if (online)
+               walk_memory_range(PFN_DOWN(start), PFN_UP(start + size - 1),
+                                 NULL, online_memory_block);
+
        goto out;
 
 error:
@@ -1345,7 +1358,7 @@ int __ref add_memory(int nid, u64 start, u64 size)
        if (IS_ERR(res))
                return PTR_ERR(res);
 
-       ret = add_memory_resource(nid, res);
+       ret = add_memory_resource(nid, res, memhp_auto_online);
        if (ret < 0)
                release_memory_resource(res);
        return ret;