xen/acpi: xen memory hotplug minor updates

Dan Carpenter found current xen memory hotplug logic
has potential issue: at func acpi_memory_get_device()
*mem_device = acpi_driver_data(device);
while the device may be NULL and then dereference.

At native side, Rafael recently updated acpi_memory_get_device(),
dropping acpi_bus_add, adding lock, and avoiding above issue.

This patch updates xen memory hotplug logic accordingly, removing
redundant logic, adding lock, and avoiding dereference.

Signed-off-by: Liu Jinsong <jinsong.liu@intel.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

1 files changed, 26 insertions, 26 deletions

diff --git a/drivers/xen/xen-acpi-memhotplug.c b/drivers/xen/xen-acpi-memhotplug.c
index 853b12dba5bb..faef5b396051 100644
--- a/drivers/xen/xen-acpi-memhotplug.c
+++ b/drivers/xen/xen-acpi-memhotplug.c
@@ -158,31 +158,17 @@ acpi_memory_get_device_resources(struct acpi_memory_device *mem_device)
         return 0;
 }
 
-static int
-acpi_memory_get_device(acpi_handle handle,
-                       struct acpi_memory_device **mem_device)
+static int acpi_memory_get_device(acpi_handle handle,
+                                  struct acpi_memory_device **mem_device)
 {
-        acpi_status status;
-        acpi_handle phandle;
         struct acpi_device *device = NULL;
-        struct acpi_device *pdevice = NULL;
-        int result;
+        int result = 0;
 
-        if (!acpi_bus_get_device(handle, &device) && device)
-                goto end;
+        acpi_scan_lock_acquire();
 
-        status = acpi_get_parent(handle, &phandle);
-        if (ACPI_FAILURE(status)) {
-                pr_warn(PREFIX "Cannot find acpi parent\n");
-                return -EINVAL;
-        }
-
-        /* Get the parent device */
-        result = acpi_bus_get_device(phandle, &pdevice);
-        if (result) {
-                pr_warn(PREFIX "Cannot get acpi bus device\n");
-                return -EINVAL;
-        }
+        acpi_bus_get_device(handle, &device);
+        if (device)
+                goto end;
 
         /*
          * Now add the notified device.  This creates the acpi_device
@@ -190,18 +176,28 @@ acpi_memory_get_device(acpi_handle handle,
          */
         result = acpi_bus_scan(handle);
         if (result) {
-                pr_warn(PREFIX "Cannot add acpi bus\n");
-                return -EINVAL;
+                pr_warn(PREFIX "ACPI namespace scan failed\n");
+                result = -EINVAL;
+                goto out;
+        }
+        result = acpi_bus_get_device(handle, &device);
+        if (result) {
+                pr_warn(PREFIX "Missing device object\n");
+                result = -EINVAL;
+                goto out;
         }
 
 end:
         *mem_device = acpi_driver_data(device);
         if (!(*mem_device)) {
-                pr_err(PREFIX "Driver data not found\n");
-                return -ENODEV;
+                pr_err(PREFIX "driver data not found\n");
+                result = -ENODEV;
+                goto out;
         }
 
-        return 0;
+out:
+        acpi_scan_lock_release();
+        return result;
 }
 
 static int acpi_memory_check_device(struct acpi_memory_device *mem_device)
@@ -259,12 +255,15 @@ static void acpi_memory_device_notify(acpi_handle handle, u32 event, void *data)
                 ACPI_DEBUG_PRINT((ACPI_DB_INFO,
                         "\nReceived EJECT REQUEST notification for device\n"));
 
+                acpi_scan_lock_acquire();
                 if (acpi_bus_get_device(handle, &device)) {
+                        acpi_scan_lock_release();
                         pr_err(PREFIX "Device doesn't exist\n");
                         break;
                 }
                 mem_device = acpi_driver_data(device);
                 if (!mem_device) {
+                        acpi_scan_lock_release();
                         pr_err(PREFIX "Driver Data is NULL\n");
                         break;
                 }
@@ -274,6 +273,7 @@ static void acpi_memory_device_notify(acpi_handle handle, u32 event, void *data)
                  * acpi_bus_remove if Xen support hotremove in the future
                  */
                 acpi_memory_disable_device(mem_device);
+                acpi_scan_lock_release();
                 break;
 
         default: