Hibernation: Introduce SNAPSHOT_GET_IMAGE_SIZE ioctl

Add a new ioctl, SNAPSHOT_GET_IMAGE_SIZE, returning the size of the (just
created) hibernation image, to the hibernation userland interface.

This ioctl is necessary so that the userland utilities using the interface need
not access the hibernation image header, owned by the kernel, in order to obtain
the size of the image.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Len Brown <len.brown@intel.com>

3 files changed, 23 insertions, 6 deletions

diff --git a/kernel/power/power.h b/kernel/power/power.h
index 2093c3a9a994..23c17031ed21 100644
--- a/kernel/power/power.h
+++ b/kernel/power/power.h
@@ -128,6 +128,7 @@ struct snapshot_handle {
 #define data_of(handle) ((handle).buffer + (handle).buf_offset)
 
 extern unsigned int snapshot_additional_pages(struct zone *zone);
+extern unsigned long snapshot_get_image_size(void);
 extern int snapshot_read_next(struct snapshot_handle *handle, size_t count);
 extern int snapshot_write_next(struct snapshot_handle *handle, size_t count);
 extern void snapshot_write_finalize(struct snapshot_handle *handle);
@@ -158,7 +159,8 @@ struct resume_swap_area {
 #define SNAPSHOT_PMOPS                  _IOW(SNAPSHOT_IOC_MAGIC, 12, unsigned int)
 #define SNAPSHOT_SET_SWAP_AREA          _IOW(SNAPSHOT_IOC_MAGIC, 13, \
                                                         struct resume_swap_area)
-#define SNAPSHOT_IOC_MAXNR      13
+#define SNAPSHOT_GET_IMAGE_SIZE         _IOR(SNAPSHOT_IOC_MAGIC, 14, loff_t)
+#define SNAPSHOT_IOC_MAXNR      14
 
 #define PMOPS_PREPARE   1
 #define PMOPS_ENTER     2
diff --git a/kernel/power/snapshot.c b/kernel/power/snapshot.c
index 78039b477d2b..c5ce0f34a5d4 100644
--- a/kernel/power/snapshot.c
+++ b/kernel/power/snapshot.c
@@ -1264,12 +1264,17 @@ static char *check_image_kernel(struct swsusp_info *info)
 }
 #endif /* CONFIG_ARCH_HIBERNATION_HEADER */
 
+unsigned long snapshot_get_image_size(void)
+{
+        return nr_copy_pages + nr_meta_pages + 1;
+}
+
 static int init_header(struct swsusp_info *info)
 {
         memset(info, 0, sizeof(struct swsusp_info));
         info->num_physpages = num_physpages;
         info->image_pages = nr_copy_pages;
-        info->pages = nr_copy_pages + nr_meta_pages + 1;
+        info->pages = snapshot_get_image_size();
         info->size = info->pages;
         info->size <<= PAGE_SHIFT;
         return init_header_complete(info);
diff --git a/kernel/power/user.c b/kernel/power/user.c
index 5bd321bcbb75..88aac26e598a 100644
--- a/kernel/power/user.c
+++ b/kernel/power/user.c
@@ -133,7 +133,7 @@ static int snapshot_ioctl(struct inode *inode, struct file *filp,
 {
         int error = 0;
         struct snapshot_data *data;
-        loff_t avail;
+        loff_t size;
         sector_t offset;
 
         if (_IOC_TYPE(cmd) != SNAPSHOT_IOC_MAGIC)
@@ -210,10 +210,20 @@ static int snapshot_ioctl(struct inode *inode, struct file *filp,
                 image_size = arg;
                 break;
 
+        case SNAPSHOT_GET_IMAGE_SIZE:
+                if (!data->ready) {
+                        error = -ENODATA;
+                        break;
+                }
+                size = snapshot_get_image_size();
+                size <<= PAGE_SHIFT;
+                error = put_user(size, (loff_t __user *)arg);
+                break;
+
         case SNAPSHOT_AVAIL_SWAP:
-                avail = count_swap_pages(data->swap, 1);
-                avail <<= PAGE_SHIFT;
-                error = put_user(avail, (loff_t __user *)arg);
+                size = count_swap_pages(data->swap, 1);
+                size <<= PAGE_SHIFT;
+                error = put_user(size, (loff_t __user *)arg);
                 break;
 
         case SNAPSHOT_GET_SWAP_PAGE: