[PATCH v2 4/5] mm: memory_hotplug: Add memory hotremove probe device

[Andrea Reale <ar@linux.vnet.ibm.com>]

Adding a "remove" sysfs handle that can be used to trigger
memory hotremove manually, exactly simmetrically with
what happens with the "probe" device for hot-add.

This is usueful for architecture that do not rely on
ACPI for memory hot-remove.

Signed-off-by: Andrea Reale <ar@linux.vnet.ibm.com>
Signed-off-by: Maciej Bielski <m.bielski@virtualopensystems.com>
---
 drivers/base/memory.c | 34 +++++++++++++++++++++++++++++++++-
 1 file changed, 33 insertions(+), 1 deletion(-)

diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index 1d60b58..8ccb67c 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -530,7 +530,36 @@ memory_probe_store(struct device *dev, struct device_attribute *attr,
 }
 
 static DEVICE_ATTR(probe, S_IWUSR, NULL, memory_probe_store);
-#endif
+
+#ifdef CONFIG_MEMORY_HOTREMOVE
+static ssize_t
+memory_remove_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t count)
+{
+	u64 phys_addr;
+	int nid, ret;
+	unsigned long pages_per_block = PAGES_PER_SECTION * sections_per_block;
+
+	ret = kstrtoull(buf, 0, &phys_addr);
+	if (ret)
+		return ret;
+
+	if (phys_addr & ((pages_per_block << PAGE_SHIFT) - 1))
+		return -EINVAL;
+
+	nid = memory_add_physaddr_to_nid(phys_addr);
+	ret = lock_device_hotplug_sysfs();
+	if (ret)
+		return ret;
+
+	remove_memory(nid, phys_addr,
+			 MIN_MEMORY_BLOCK_SIZE * sections_per_block);
+	unlock_device_hotplug();
+	return count;
+}
+static DEVICE_ATTR(remove, S_IWUSR, NULL, memory_remove_store);
+#endif /* CONFIG_MEMORY_HOTREMOVE */
+#endif /* CONFIG_ARCH_MEMORY_PROBE */
 
 #ifdef CONFIG_MEMORY_FAILURE
 /*
@@ -790,6 +819,9 @@ bool is_memblock_offlined(struct memory_block *mem)
 static struct attribute *memory_root_attrs[] = {
 #ifdef CONFIG_ARCH_MEMORY_PROBE
 	&dev_attr_probe.attr,
+#ifdef CONFIG_MEMORY_HOTREMOVE
+	&dev_attr_remove.attr,
+#endif
 #endif
 
 #ifdef CONFIG_MEMORY_FAILURE
-- 
2.7.4