[PATCH 4/7 v2] don't allow to eject the memory device if it is being used

[Wen Congyang <wency@cn.fujitsu.com>]

We eject the memory device even if it is in use. It is very dangerous,
and it will cause the kernel panicked.

Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
---
 drivers/acpi/acpi_memhotplug.c |   38 +++++++++++++++++++++++++++++++-------
 1 files changed, 31 insertions(+), 7 deletions(-)

diff --git a/drivers/acpi/acpi_memhotplug.c b/drivers/acpi/acpi_memhotplug.c
index 1f6196a..1597348 100644
--- a/drivers/acpi/acpi_memhotplug.c
+++ b/drivers/acpi/acpi_memhotplug.c
@@ -78,6 +78,7 @@ struct acpi_memory_info {
 	unsigned short caching;	/* memory cache attribute */
 	unsigned short write_protect;	/* memory read/write attribute */
 	unsigned int enabled:1;
+	unsigned int failed:1;
 };
 
 struct acpi_memory_device {
@@ -257,9 +258,23 @@ static int acpi_memory_enable_device(struct acpi_memory_device *mem_device)
 			node = memory_add_physaddr_to_nid(info->start_addr);
 
 		result = add_memory(node, info->start_addr, info->length);
-		if (result)
+
+		/*
+		 * If the memory block has been used by the kernel, add_memory()
+		 * returns -EEXIST. If add_memory() returns the other error, it
+		 * means that this memory block is not used by the kernel.
+		 */
+		if (result && result != -EEXIST) {
+			info->failed = 1;
 			continue;
-		info->enabled = 1;
+		}
+
+		if (!result)
+			info->enabled = 1;
+		/*
+		 * Add num_enable even if add_memory() returns -EEXIST, so the
+		 * device is bound to this driver.
+		 */
 		num_enabled++;
 	}
 	if (!num_enabled) {
@@ -323,11 +338,20 @@ static int acpi_memory_disable_device(struct acpi_memory_device *mem_device)
 	 * Note: Assume that this function returns zero on success
 	 */
 	list_for_each_entry_safe(info, n, &mem_device->res_list, list) {
-		if (info->enabled) {
-			result = remove_memory(info->start_addr, info->length);
-			if (result)
-				return result;
-		}
+		if (info->failed)
+			/* The kernel does not use this memory block */
+			continue;
+
+		if (!info->enabled)
+			/*
+			 * The kernel uses this memory block, but it may be not
+			 * managed by us.
+			 */
+			return -EBUSY;
+
+		result = remove_memory(info->start_addr, info->length);
+		if (result)
+			return result;
 		list_del(&info->list);
 		kfree(info);
 	}
-- 
1.7.1