[PATCH v2] memory-hotplug: add sysfs zones_online_to attribute

[Zhang Zhen <zhenzhang.zhang@huawei.com>]

Currently memory-hotplug has two limits:
1. If the memory block is in ZONE_NORMAL, you can change it to
ZONE_MOVABLE, but this memory block must be adjacent to ZONE_MOVABLE.
2. If the memory block is in ZONE_MOVABLE, you can change it to
ZONE_NORMAL, but this memory block must be adjacent to ZONE_NORMAL.

With this patch, we can easy to know a memory block can be onlined to
which zone, and don't need to know the above two limits.

Updated the related Documentation.

Change v1 -> v2:
- optimize the implementation following Dave Hansen's suggestion

Signed-off-by: Zhang Zhen <zhenzhang.zhang@huawei.com>
---
 Documentation/ABI/testing/sysfs-devices-memory |  8 ++++
 Documentation/memory-hotplug.txt               |  4 +-
 drivers/base/memory.c                          | 62 ++++++++++++++++++++++++++
 include/linux/memory_hotplug.h                 |  1 +
 mm/memory_hotplug.c                            |  2 +-
 5 files changed, 75 insertions(+), 2 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-devices-memory b/Documentation/ABI/testing/sysfs-devices-memory
index 7405de2..2b2a1d7 100644
--- a/Documentation/ABI/testing/sysfs-devices-memory
+++ b/Documentation/ABI/testing/sysfs-devices-memory
@@ -61,6 +61,14 @@ Users:		hotplug memory remove tools
 		http://www.ibm.com/developerworks/wikis/display/LinuxP/powerpc-utils


+What:           /sys/devices/system/memory/memoryX/zones_online_to
+Date:           July 2014
+Contact:	Zhang Zhen <zhenzhang.zhang@huawei.com>
+Description:
+		The file /sys/devices/system/memory/memoryX/zones_online_to
+		is read-only and is designed to show which zone this memory block can
+		be onlined to.
+
 What:		/sys/devices/system/memoryX/nodeY
 Date:		October 2009
 Contact:	Linux Memory Management list <linux-mm@kvack.org>
diff --git a/Documentation/memory-hotplug.txt b/Documentation/memory-hotplug.txt
index 45134dc..5b34e33 100644
--- a/Documentation/memory-hotplug.txt
+++ b/Documentation/memory-hotplug.txt
@@ -155,6 +155,7 @@ Under each memory block, you can see 4 files:
 /sys/devices/system/memory/memoryXXX/phys_device
 /sys/devices/system/memory/memoryXXX/state
 /sys/devices/system/memory/memoryXXX/removable
+/sys/devices/system/memory/memoryXXX/zones_online_to

 'phys_index'      : read-only and contains memory block id, same as XXX.
 'state'           : read-write
@@ -170,6 +171,8 @@ Under each memory block, you can see 4 files:
                     block is removable and a value of 0 indicates that
                     it is not removable. A memory block is removable only if
                     every section in the block is removable.
+'zones_online_to' : read-only: designed to show which zone this memory block
+		    can be onlined to.

 NOTE:
   These directories/files appear after physical memory hotplug phase.
@@ -408,7 +411,6 @@ node if necessary.
   - allowing memory hot-add to ZONE_MOVABLE. maybe we need some switch like
     sysctl or new control file.
   - showing memory block and physical device relationship.
-  - showing memory block is under ZONE_MOVABLE or not
   - test and make it better memory offlining.
   - support HugeTLB page migration and offlining.
   - memmap removing at memory offline.
diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index a2e13e2..b5d693f 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -373,10 +373,71 @@ static ssize_t show_phys_device(struct device *dev,
 	return sprintf(buf, "%d\n", mem->phys_device);
 }

+static int __zones_online_to(unsigned long end_pfn,
+				struct page *first_page, unsigned long nr_pages)
+{
+	struct zone *zone_next;
+
+	/*The mem block is the last block of memory.*/
+	if (!pfn_valid(end_pfn + 1))
+		return 1;
+	zone_next = page_zone(first_page + nr_pages);
+	if (zone_idx(zone_next) == ZONE_MOVABLE)
+		return 1;
+	return 0;
+}
+
+static ssize_t show_zones_online_to(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	struct memory_block *mem = to_memory_block(dev);
+	unsigned long start_pfn, end_pfn;
+	unsigned long nr_pages = PAGES_PER_SECTION * sections_per_block;
+	struct page *first_page;
+	struct zone *zone, *zone_prev;
+
+	start_pfn = section_nr_to_pfn(mem->start_section_nr);
+	end_pfn = start_pfn + nr_pages;
+	first_page = pfn_to_page(start_pfn);
+
+	/*The block contains more than one zone can not be offlined.*/
+	if (!test_pages_in_a_zone(start_pfn, end_pfn))
+		return sprintf(buf, "none\n");
+
+	zone = page_zone(first_page);
+
+#ifdef CONFIG_HIGHMEM
+	if (zone_idx(zone) == ZONE_HIGHMEM) {
+		if (__zones_online_to(end_pfn, first_page, nr_pages))
+			return sprintf(buf, "%s %s\n",
+					zone->name, (zone + 1)->name);
+	}
+#else
+	if (zone_idx(zone) == ZONE_NORMAL) {
+		if (__zones_online_to(end_pfn, first_page, nr_pages))
+			return sprintf(buf, "%s %s\n",
+					zone->name, (zone + 1)->name);
+	}
+#endif
+
+	if (zone_idx(zone) == ZONE_MOVABLE) {
+		if (!pfn_valid(start_pfn - nr_pages))
+			return sprintf(buf, "%s %s\n",
+						zone->name, (zone - 1)->name);
+		zone_prev = page_zone(first_page - nr_pages);
+		if (zone_idx(zone_prev) != ZONE_MOVABLE)
+			return sprintf(buf, "%s %s\n",
+						zone->name, (zone - 1)->name);
+	}
+
+	return sprintf(buf, "%s\n", zone->name);
+}
+
 static DEVICE_ATTR(phys_index, 0444, show_mem_start_phys_index, NULL);
 static DEVICE_ATTR(state, 0644, show_mem_state, store_mem_state);
 static DEVICE_ATTR(phys_device, 0444, show_phys_device, NULL);
 static DEVICE_ATTR(removable, 0444, show_mem_removable, NULL);
+static DEVICE_ATTR(zones_online_to, 0444, show_zones_online_to, NULL);

 /*
  * Block size attribute stuff
@@ -523,6 +584,7 @@ static struct attribute *memory_memblk_attrs[] = {
 	&dev_attr_state.attr,
 	&dev_attr_phys_device.attr,
 	&dev_attr_removable.attr,
+	&dev_attr_zones_online_to.attr,
 	NULL
 };

diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index d9524c4..8f1a419 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -84,6 +84,7 @@ extern int zone_grow_waitqueues(struct zone *zone, unsigned long nr_pages);
 extern int add_one_highpage(struct page *page, int pfn, int bad_ppro);
 /* VM interface that may be used by firmware interface */
 extern int online_pages(unsigned long, unsigned long, int);
+extern int test_pages_in_a_zone(unsigned long, unsigned long);
 extern void __offline_isolated_pages(unsigned long, unsigned long);

 typedef void (*online_page_callback_t)(struct page *page);
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 2ff8c23..29d8693 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1307,7 +1307,7 @@ int is_mem_section_removable(unsigned long start_pfn, unsigned long nr_pages)
 /*
  * Confirm all pages in a range [start, end) is belongs to the same zone.
  */
-static int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn)
+int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn)
 {
 	unsigned long pfn;
 	struct zone *zone = NULL;
-- 
1.8.1.2


.




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