[RFC PATCH v2 3/3] acpi_memhotplug: Add prepare_remove operation

[Vasilis Liaskovitis <vasilis.liaskovitis@xxxxxxxxxxxxxxxx>]

Offlining and removal of memory is now done in the prepare_remove callback,
not in the remove callback.

The prepare_remove callback will be called when trying to remove a memory device
with the following ways:

1. send eject request by SCI
2. echo 1 >/sys/bus/pci/devices/PNP0C80:XX/eject
3. echo "PNP0C80:00" > /sys/bus/acpi/drivers/acpi_memhotplug/unbind

Signed-off-by: Vasilis Liaskovitis <vasilis.liaskovitis@xxxxxxxxxxxxxxxx>
---
 drivers/acpi/acpi_memhotplug.c |   22 ++++++++++++++++++++--
 1 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/drivers/acpi/acpi_memhotplug.c b/drivers/acpi/acpi_memhotplug.c
index 92c973a..8615ff3 100644
--- a/drivers/acpi/acpi_memhotplug.c
+++ b/drivers/acpi/acpi_memhotplug.c
@@ -54,6 +54,7 @@ MODULE_LICENSE("GPL");
 
 static int acpi_memory_device_add(struct acpi_device *device);
 static int acpi_memory_device_remove(struct acpi_device *device, int type);
+static int acpi_memory_device_prepare_remove(struct acpi_device *device);
 
 static const struct acpi_device_id memory_device_ids[] = {
 	{ACPI_MEMORY_DEVICE_HID, 0},
@@ -68,6 +69,7 @@ static struct acpi_driver acpi_memory_device_driver = {
 	.ops = {
 		.add = acpi_memory_device_add,
 		.remove = acpi_memory_device_remove,
+		.prepare_remove = acpi_memory_device_prepare_remove,
 		},
 };
 
@@ -499,6 +501,20 @@ static int acpi_memory_device_add(struct acpi_device *device)
 static int acpi_memory_device_remove(struct acpi_device *device, int type)
 {
 	struct acpi_memory_device *mem_device = NULL;
+
+	if (!device || !acpi_driver_data(device))
+		return -EINVAL;
+
+	mem_device = acpi_driver_data(device);
+
+	kfree(mem_device);
+
+	return 0;
+}
+
+static int acpi_memory_device_prepare_remove(struct acpi_device *device)
+{
+	struct acpi_memory_device *mem_device = NULL;
 	int result;
 
 	if (!device || !acpi_driver_data(device))
@@ -506,12 +522,14 @@ static int acpi_memory_device_remove(struct acpi_device *device, int type)
 
 	mem_device = acpi_driver_data(device);
 
+	/*
+	 * offline and remove memory only when the memory device is
+	 * ejected.
+	 */
 	result = acpi_memory_remove_memory(mem_device);
 	if (result)
 		return result;
 
-	kfree(mem_device);
-
 	return 0;
 }
 
-- 
1.7.9

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