From: "Rafael J. Wysocki" <rjw@sisk.pl>

To be able to use swap files as suspend storage from the userland suspend
tools we need an additional ioctl() that will allow us to provide the kernel
with both the swap header's offset and the identification of the resume
partition.

The new ioctl() should be regarded as a replacement for the
SNAPSHOT_SET_SWAP_FILE ioctl() that from now on will be considered as
obsolete, but has to stay for backwards compatibility of the interface.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---

 kernel/power/power.h |   13 ++++++++++++-
 kernel/power/user.c  |   31 +++++++++++++++++++++++++++++++
 2 files changed, 43 insertions(+), 1 deletion(-)

diff -puN kernel/power/power.h~swsusp-add-ioctl-for-swap-files-support kernel/power/power.h
--- a/kernel/power/power.h~swsusp-add-ioctl-for-swap-files-support
+++ a/kernel/power/power.h
@@ -119,7 +119,18 @@ extern void snapshot_free_unused_memory(
 #define SNAPSHOT_SET_SWAP_FILE		_IOW(SNAPSHOT_IOC_MAGIC, 10, unsigned int)
 #define SNAPSHOT_S2RAM			_IO(SNAPSHOT_IOC_MAGIC, 11)
 #define SNAPSHOT_PMOPS			_IOW(SNAPSHOT_IOC_MAGIC, 12, unsigned int)
-#define SNAPSHOT_IOC_MAXNR	12
+#define SNAPSHOT_SET_SWAP_AREA		_IOW(SNAPSHOT_IOC_MAGIC, 13, void *)
+#define SNAPSHOT_IOC_MAXNR	13
+
+/*
+ * This structure is used to pass the values needed for the identification
+ * of the resume swap area from a user space to the kernel via the
+ * SNAPSHOT_SET_SWAP_AREA ioctl
+ */
+struct resume_swap_area {
+	loff_t offset;
+	u_int32_t dev;
+} __attribute__((packed));
 
 #define PMOPS_PREPARE	1
 #define PMOPS_ENTER	2
diff -puN kernel/power/user.c~swsusp-add-ioctl-for-swap-files-support kernel/power/user.c
--- a/kernel/power/user.c~swsusp-add-ioctl-for-swap-files-support
+++ a/kernel/power/user.c
@@ -343,6 +343,37 @@ OutS3:
 		}
 		break;
 
+	case SNAPSHOT_SET_SWAP_AREA:
+		if (data->bitmap) {
+			error = -EPERM;
+		} else {
+			struct resume_swap_area swap_area;
+			dev_t swdev;
+
+			error = copy_from_user(&swap_area, (void __user *)arg,
+					sizeof(struct resume_swap_area));
+			if (error) {
+				error = -EFAULT;
+				break;
+			}
+
+			/*
+			 * User space encodes device types as two-byte values,
+			 * so we need to recode them
+			 */
+			swdev = old_decode_dev(swap_area.dev);
+			if (swdev) {
+				offset = swap_area.offset;
+				data->swap = swap_type_of(swdev, offset);
+				if (data->swap < 0)
+					error = -ENODEV;
+			} else {
+				data->swap = -1;
+				error = -EINVAL;
+			}
+		}
+		break;
+
 	default:
 		error = -ENOTTY;
 
_