[Patch v4 5/7] acpi_memhotplug.c: 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 to be panicked.

CC: David Rientjes <rientjes@google.com>
CC: Jiang Liu <liuj97@gmail.com>
CC: Len Brown <len.brown@intel.com>
CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
CC: Paul Mackerras <paulus@samba.org>
CC: Christoph Lameter <cl@linux.com>
Cc: Minchan Kim <minchan.kim@gmail.com>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
CC: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
CC: Rafael J. Wysocki <rjw@sisk.pl>
CC: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
---
 drivers/acpi/acpi_memhotplug.c | 46 +++++++++++++++++++++++++++++++++---------
 1 file changed, 36 insertions(+), 10 deletions(-)

diff --git a/drivers/acpi/acpi_memhotplug.c b/drivers/acpi/acpi_memhotplug.c
index 8914399..1fb1342 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 {
@@ -266,9 +267,23 @@ 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++;
 	}
 	mutex_unlock(&mem_device->list_lock);
@@ -324,25 +339,36 @@ static int acpi_memory_powerdown_device(struct acpi_memory_device *mem_device)
 
 static int acpi_memory_remove_memory(struct acpi_memory_device *mem_device)
 {
-	int result;
+	int result = 0;
 	struct acpi_memory_info *info, *n;
 
 	mutex_lock(&mem_device->list_lock);
 	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) {
-				mutex_unlock(&mem_device->list_lock);
-				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.
+			 */
+			result = -EBUSY;
+			goto out;
 		}
 
+		result = remove_memory(info->start_addr, info->length);
+		if (result)
+			goto out;
+
 		list_del(&info->list);
 		kfree(info);
 	}
+
+out:
 	mutex_unlock(&mem_device->list_lock);
 
-	return 0;
+	return result;
 }
 
 static int acpi_memory_disable_device(struct acpi_memory_device *mem_device)
-- 
1.8.0

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