kernel/power/user.c - linux - Git at Google

 /*
  * linux/kernel/power/user.c
  *
  * This file provides the user space interface for software suspend/resume.
  *
  * Copyright (C) 2006 Rafael J. Wysocki <rjw@sisk.pl>
  *
  * This file is released under the GPLv2.
  *
  */

 #include <linux/suspend.h>
 #include <linux/syscalls.h>
 #include <linux/reboot.h>
 #include <linux/string.h>
 #include <linux/device.h>
 #include <linux/miscdevice.h>
 #include <linux/mm.h>
 #include <linux/swap.h>
 #include <linux/swapops.h>
 #include <linux/pm.h>
 #include <linux/fs.h>
 #include <linux/compat.h>
 #include <linux/console.h>
 #include <linux/cpu.h>
 #include <linux/freezer.h>

 #include <linux/uaccess.h>

 #include "power.h"


 #define SNAPSHOT_MINOR	231

 static struct snapshot_data {
 	struct snapshot_handle handle;
 	int swap;
 	int mode;
 	bool frozen;
 	bool ready;
 	bool platform_support;
 	bool free_bitmaps;
 } snapshot_state;

 atomic_t snapshot_device_available = ATOMIC_INIT(1);

 static int snapshot_open(struct inode *inode, struct file *filp)
 {
 	struct snapshot_data *data;
 	int error, nr_calls = 0;

 	if (!hibernation_available())
 		return -EPERM;

 	lock_system_sleep();

 	if (!atomic_add_unless(&snapshot_device_available, -1, 0)) {
 		error = -EBUSY;
 		goto Unlock;
 	}

 	if ((filp->f_flags & O_ACCMODE) == O_RDWR) {
 		atomic_inc(&snapshot_device_available);
 		error = -ENOSYS;
 		goto Unlock;
 	}
 	nonseekable_open(inode, filp);
 	data = &snapshot_state;
 	filp->private_data = data;
 	memset(&data->handle, 0, sizeof(struct snapshot_handle));
 	if ((filp->f_flags & O_ACCMODE) == O_RDONLY) {
 		/* Hibernating.  The image device should be accessible. */
 		data->swap = swsusp_resume_device ?
 			swap_type_of(swsusp_resume_device, 0, NULL) : -1;
 		data->mode = O_RDONLY;
 		data->free_bitmaps = false;
 		error = __pm_notifier_call_chain(PM_HIBERNATION_PREPARE, -1, &nr_calls);
 		if (error)
 			__pm_notifier_call_chain(PM_POST_HIBERNATION, --nr_calls, NULL);
 	} else {
 		/*
 		 * Resuming.  We may need to wait for the image device to
 		 * appear.
 		 */
 		wait_for_device_probe();

 		data->swap = -1;
 		data->mode = O_WRONLY;
 		error = __pm_notifier_call_chain(PM_RESTORE_PREPARE, -1, &nr_calls);
 		if (!error) {
 			error = create_basic_memory_bitmaps();
 			data->free_bitmaps = !error;
 		} else
 			nr_calls--;

 		if (error)
 			__pm_notifier_call_chain(PM_POST_RESTORE, nr_calls, NULL);
 	}
 	if (error)
 		atomic_inc(&snapshot_device_available);

 	data->frozen = false;
 	data->ready = false;
 	data->platform_support = false;

  Unlock:
 	unlock_system_sleep();

 	return error;
 }

 static int snapshot_release(struct inode *inode, struct file *filp)
 {
 	struct snapshot_data *data;

 	lock_system_sleep();

 	swsusp_free();
 	data = filp->private_data;
 	free_all_swap_pages(data->swap);
 	if (data->frozen) {
 		pm_restore_gfp_mask();
 		free_basic_memory_bitmaps();
 		thaw_processes();
 	} else if (data->free_bitmaps) {
 		free_basic_memory_bitmaps();
 	}
 	pm_notifier_call_chain(data->mode == O_RDONLY ?
 			PM_POST_HIBERNATION : PM_POST_RESTORE);
 	atomic_inc(&snapshot_device_available);

 	unlock_system_sleep();

 	return 0;
 }

 static ssize_t snapshot_read(struct file *filp, char __user *buf,
                              size_t count, loff_t *offp)
 {
 	struct snapshot_data *data;
 	ssize_t res;
 	loff_t pg_offp = *offp & ~PAGE_MASK;

 	lock_system_sleep();

 	data = filp->private_data;
 	if (!data->ready) {
 		res = -ENODATA;
 		goto Unlock;
 	}
 	if (!pg_offp) { /* on page boundary? */
 		res = snapshot_read_next(&data->handle);
 		if (res <= 0)
 			goto Unlock;
 	} else {
 		res = PAGE_SIZE - pg_offp;
 	}

 	res = simple_read_from_buffer(buf, count, &pg_offp,
 			data_of(data->handle), res);
 	if (res > 0)
 		*offp += res;

  Unlock:
 	unlock_system_sleep();

 	return res;
 }

 static ssize_t snapshot_write(struct file *filp, const char __user *buf,
                               size_t count, loff_t *offp)
 {
 	struct snapshot_data *data;
 	ssize_t res;
 	loff_t pg_offp = *offp & ~PAGE_MASK;

 	lock_system_sleep();

 	data = filp->private_data;

 	if (!pg_offp) {
 		res = snapshot_write_next(&data->handle);
 		if (res <= 0)
 			goto unlock;
 	} else {
 		res = PAGE_SIZE - pg_offp;
 	}

 	if (!data_of(data->handle)) {
 		res = -EINVAL;
 		goto unlock;
 	}

 	res = simple_write_to_buffer(data_of(data->handle), res, &pg_offp,
 			buf, count);
 	if (res > 0)
 		*offp += res;
 unlock:
 	unlock_system_sleep();

 	return res;
 }

 static long snapshot_ioctl(struct file *filp, unsigned int cmd,
 							unsigned long arg)
 {
 	int error = 0;
 	struct snapshot_data *data;
 	loff_t size;
 	sector_t offset;

 	if (_IOC_TYPE(cmd) != SNAPSHOT_IOC_MAGIC)
 		return -ENOTTY;
 	if (_IOC_NR(cmd) > SNAPSHOT_IOC_MAXNR)
 		return -ENOTTY;
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;

 	if (!mutex_trylock(&system_transition_mutex))
 		return -EBUSY;

 	lock_device_hotplug();
 	data = filp->private_data;

 	switch (cmd) {

 	case SNAPSHOT_FREEZE:
 		if (data->frozen)
 			break;

 		printk("Syncing filesystems ... ");
 		ksys_sync();
 		printk("done.\n");

 		error = freeze_processes();
 		if (error)
 			break;

 		error = create_basic_memory_bitmaps();
 		if (error)
 			thaw_processes();
 		else
 			data->frozen = true;

 		break;

 	case SNAPSHOT_UNFREEZE:
 		if (!data->frozen || data->ready)
 			break;
 		pm_restore_gfp_mask();
 		free_basic_memory_bitmaps();
 		data->free_bitmaps = false;
 		thaw_processes();
 		data->frozen = false;
 		break;

 	case SNAPSHOT_CREATE_IMAGE:
 		if (data->mode != O_RDONLY || !data->frozen  || data->ready) {
 			error = -EPERM;
 			break;
 		}
 		pm_restore_gfp_mask();
 		error = hibernation_snapshot(data->platform_support);
 		if (!error) {
 			error = put_user(in_suspend, (int __user *)arg);
 			data->ready = !freezer_test_done && !error;
 			freezer_test_done = false;
 		}
 		break;

 	case SNAPSHOT_ATOMIC_RESTORE:
 		snapshot_write_finalize(&data->handle);
 		if (data->mode != O_WRONLY || !data->frozen ||
 		    !snapshot_image_loaded(&data->handle)) {
 			error = -EPERM;
 			break;
 		}
 		error = hibernation_restore(data->platform_support);
 		break;

 	case SNAPSHOT_FREE:
 		swsusp_free();
 		memset(&data->handle, 0, sizeof(struct snapshot_handle));
 		data->ready = false;
 		/*
 		 * It is necessary to thaw kernel threads here, because
 		 * SNAPSHOT_CREATE_IMAGE may be invoked directly after
 		 * SNAPSHOT_FREE.  In that case, if kernel threads were not
 		 * thawed, the preallocation of memory carried out by
 		 * hibernation_snapshot() might run into problems (i.e. it
 		 * might fail or even deadlock).
 		 */
 		thaw_kernel_threads();
 		break;

 	case SNAPSHOT_PREF_IMAGE_SIZE:
 		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_SIZE:
 		size = count_swap_pages(data->swap, 1);
 		size <<= PAGE_SHIFT;
 		error = put_user(size, (loff_t __user *)arg);
 		break;

 	case SNAPSHOT_ALLOC_SWAP_PAGE:
 		if (data->swap < 0 || data->swap >= MAX_SWAPFILES) {
 			error = -ENODEV;
 			break;
 		}
 		offset = alloc_swapdev_block(data->swap);
 		if (offset) {
 			offset <<= PAGE_SHIFT;
 			error = put_user(offset, (loff_t __user *)arg);
 		} else {
 			error = -ENOSPC;
 		}
 		break;

 	case SNAPSHOT_FREE_SWAP_PAGES:
 		if (data->swap < 0 || data->swap >= MAX_SWAPFILES) {
 			error = -ENODEV;
 			break;
 		}
 		free_all_swap_pages(data->swap);
 		break;

 	case SNAPSHOT_S2RAM:
 		if (!data->frozen) {
 			error = -EPERM;
 			break;
 		}
 		/*
 		 * Tasks are frozen and the notifiers have been called with
 		 * PM_HIBERNATION_PREPARE
 		 */
 		error = suspend_devices_and_enter(PM_SUSPEND_MEM);
 		data->ready = false;
 		break;

 	case SNAPSHOT_PLATFORM_SUPPORT:
 		data->platform_support = !!arg;
 		break;

 	case SNAPSHOT_POWER_OFF:
 		if (data->platform_support)
 			error = hibernation_platform_enter();
 		break;

 	case SNAPSHOT_SET_SWAP_AREA:
 		if (swsusp_swap_in_use()) {
 			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 = new_decode_dev(swap_area.dev);
 			if (swdev) {
 				offset = swap_area.offset;
 				data->swap = swap_type_of(swdev, offset, NULL);
 				if (data->swap < 0)
 					error = -ENODEV;
 			} else {
 				data->swap = -1;
 				error = -EINVAL;
 			}
 		}
 		break;

 	default:
 		error = -ENOTTY;

 	}

 	unlock_device_hotplug();
 	mutex_unlock(&system_transition_mutex);

 	return error;
 }

 #ifdef CONFIG_COMPAT

 struct compat_resume_swap_area {
 	compat_loff_t offset;
 	u32 dev;
 } __packed;

 static long
 snapshot_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 {
 	BUILD_BUG_ON(sizeof(loff_t) != sizeof(compat_loff_t));

 	switch (cmd) {
 	case SNAPSHOT_GET_IMAGE_SIZE:
 	case SNAPSHOT_AVAIL_SWAP_SIZE:
 	case SNAPSHOT_ALLOC_SWAP_PAGE: {
 		compat_loff_t __user *uoffset = compat_ptr(arg);
 		loff_t offset;
 		mm_segment_t old_fs;
 		int err;

 		old_fs = get_fs();
 		set_fs(KERNEL_DS);
 		err = snapshot_ioctl(file, cmd, (unsigned long) &offset);
 		set_fs(old_fs);
 		if (!err && put_user(offset, uoffset))
 			err = -EFAULT;
 		return err;
 	}

 	case SNAPSHOT_CREATE_IMAGE:
 		return snapshot_ioctl(file, cmd,
 				      (unsigned long) compat_ptr(arg));

 	case SNAPSHOT_SET_SWAP_AREA: {
 		struct compat_resume_swap_area __user *u_swap_area =
 			compat_ptr(arg);
 		struct resume_swap_area swap_area;
 		mm_segment_t old_fs;
 		int err;

 		err = get_user(swap_area.offset, &u_swap_area->offset);
 		err |= get_user(swap_area.dev, &u_swap_area->dev);
 		if (err)
 			return -EFAULT;
 		old_fs = get_fs();
 		set_fs(KERNEL_DS);
 		err = snapshot_ioctl(file, SNAPSHOT_SET_SWAP_AREA,
 				     (unsigned long) &swap_area);
 		set_fs(old_fs);
 		return err;
 	}

 	default:
 		return snapshot_ioctl(file, cmd, arg);
 	}
 }

 #endif /* CONFIG_COMPAT */

 static const struct file_operations snapshot_fops = {
 	.open = snapshot_open,
 	.release = snapshot_release,
 	.read = snapshot_read,
 	.write = snapshot_write,
 	.llseek = no_llseek,
 	.unlocked_ioctl = snapshot_ioctl,
 #ifdef CONFIG_COMPAT
 	.compat_ioctl = snapshot_compat_ioctl,
 #endif
 };

 static struct miscdevice snapshot_device = {
 	.minor = SNAPSHOT_MINOR,
 	.name = "snapshot",
 	.fops = &snapshot_fops,
 };

 static int __init snapshot_device_init(void)
 {
 	return misc_register(&snapshot_device);
 };

 device_initcall(snapshot_device_init);
	/*
	* linux/kernel/power/user.c
	*
	* This file provides the user space interface for software suspend/resume.
	*
	* Copyright (C) 2006 Rafael J. Wysocki <rjw@sisk.pl>
	*
	* This file is released under the GPLv2.
	*
	*/

	#include <linux/suspend.h>
	#include <linux/syscalls.h>
	#include <linux/reboot.h>
	#include <linux/string.h>
	#include <linux/device.h>
	#include <linux/miscdevice.h>
	#include <linux/mm.h>
	#include <linux/swap.h>
	#include <linux/swapops.h>
	#include <linux/pm.h>
	#include <linux/fs.h>
	#include <linux/compat.h>
	#include <linux/console.h>
	#include <linux/cpu.h>
	#include <linux/freezer.h>

	#include <linux/uaccess.h>

	#include "power.h"


	#define SNAPSHOT_MINOR 231

	static struct snapshot_data {
	struct snapshot_handle handle;
	int swap;
	int mode;
	bool frozen;
	bool ready;
	bool platform_support;
	bool free_bitmaps;
	} snapshot_state;

	atomic_t snapshot_device_available = ATOMIC_INIT(1);

	static int snapshot_open(struct inode inode, struct file filp)
	{
	struct snapshot_data *data;
	int error, nr_calls = 0;

	if (!hibernation_available())
	return -EPERM;

	lock_system_sleep();

	if (!atomic_add_unless(&snapshot_device_available, -1, 0)) {
	error = -EBUSY;
	goto Unlock;
	}

	if ((filp->f_flags & O_ACCMODE) == O_RDWR) {
	atomic_inc(&snapshot_device_available);
	error = -ENOSYS;
	goto Unlock;
	}
	nonseekable_open(inode, filp);
	data = &snapshot_state;
	filp->private_data = data;
	memset(&data->handle, 0, sizeof(struct snapshot_handle));
	if ((filp->f_flags & O_ACCMODE) == O_RDONLY) {
	/* Hibernating. The image device should be accessible. */
	data->swap = swsusp_resume_device ?
	swap_type_of(swsusp_resume_device, 0, NULL) : -1;
	data->mode = O_RDONLY;
	data->free_bitmaps = false;
	error = __pm_notifier_call_chain(PM_HIBERNATION_PREPARE, -1, &nr_calls);
	if (error)
	__pm_notifier_call_chain(PM_POST_HIBERNATION, --nr_calls, NULL);
	} else {
	/*
	* Resuming. We may need to wait for the image device to
	* appear.
	*/
	wait_for_device_probe();

	data->swap = -1;
	data->mode = O_WRONLY;
	error = __pm_notifier_call_chain(PM_RESTORE_PREPARE, -1, &nr_calls);
	if (!error) {
	error = create_basic_memory_bitmaps();
	data->free_bitmaps = !error;
	} else
	nr_calls--;

	if (error)
	__pm_notifier_call_chain(PM_POST_RESTORE, nr_calls, NULL);
	}
	if (error)
	atomic_inc(&snapshot_device_available);

	data->frozen = false;
	data->ready = false;
	data->platform_support = false;

	Unlock:
	unlock_system_sleep();

	return error;
	}

	static int snapshot_release(struct inode inode, struct file filp)
	{
	struct snapshot_data *data;

	lock_system_sleep();

	swsusp_free();
	data = filp->private_data;
	free_all_swap_pages(data->swap);
	if (data->frozen) {
	pm_restore_gfp_mask();
	free_basic_memory_bitmaps();
	thaw_processes();
	} else if (data->free_bitmaps) {
	free_basic_memory_bitmaps();
	}
	pm_notifier_call_chain(data->mode == O_RDONLY ?
	PM_POST_HIBERNATION : PM_POST_RESTORE);
	atomic_inc(&snapshot_device_available);

	unlock_system_sleep();

	return 0;
	}

	static ssize_t snapshot_read(struct file filp, char __user buf,
	size_t count, loff_t *offp)
	{
	struct snapshot_data *data;
	ssize_t res;
	loff_t pg_offp = *offp & ~PAGE_MASK;

	lock_system_sleep();

	data = filp->private_data;
	if (!data->ready) {
	res = -ENODATA;
	goto Unlock;
	}
	if (!pg_offp) { /* on page boundary? */
	res = snapshot_read_next(&data->handle);
	if (res <= 0)
	goto Unlock;
	} else {
	res = PAGE_SIZE - pg_offp;
	}

	res = simple_read_from_buffer(buf, count, &pg_offp,
	data_of(data->handle), res);
	if (res > 0)
	*offp += res;

	Unlock:
	unlock_system_sleep();

	return res;
	}

	static ssize_t snapshot_write(struct file filp, const char __user buf,
	size_t count, loff_t *offp)
	{
	struct snapshot_data *data;
	ssize_t res;
	loff_t pg_offp = *offp & ~PAGE_MASK;

	lock_system_sleep();

	data = filp->private_data;

	if (!pg_offp) {
	res = snapshot_write_next(&data->handle);
	if (res <= 0)
	goto unlock;
	} else {
	res = PAGE_SIZE - pg_offp;
	}

	if (!data_of(data->handle)) {
	res = -EINVAL;
	goto unlock;
	}

	res = simple_write_to_buffer(data_of(data->handle), res, &pg_offp,
	buf, count);
	if (res > 0)
	*offp += res;
	unlock:
	unlock_system_sleep();

	return res;
	}

	static long snapshot_ioctl(struct file *filp, unsigned int cmd,
	unsigned long arg)
	{
	int error = 0;
	struct snapshot_data *data;
	loff_t size;
	sector_t offset;

	if (_IOC_TYPE(cmd) != SNAPSHOT_IOC_MAGIC)
	return -ENOTTY;
	if (_IOC_NR(cmd) > SNAPSHOT_IOC_MAXNR)
	return -ENOTTY;
	if (!capable(CAP_SYS_ADMIN))
	return -EPERM;

	if (!mutex_trylock(&system_transition_mutex))
	return -EBUSY;

	lock_device_hotplug();
	data = filp->private_data;

	switch (cmd) {

	case SNAPSHOT_FREEZE:
	if (data->frozen)
	break;

	printk("Syncing filesystems ... ");
	ksys_sync();
	printk("done.\n");

	error = freeze_processes();
	if (error)
	break;

	error = create_basic_memory_bitmaps();
	if (error)
	thaw_processes();
	else
	data->frozen = true;

	break;

	case SNAPSHOT_UNFREEZE:
	if (!data->frozen \|\| data->ready)
	break;
	pm_restore_gfp_mask();
	free_basic_memory_bitmaps();
	data->free_bitmaps = false;
	thaw_processes();
	data->frozen = false;
	break;

	case SNAPSHOT_CREATE_IMAGE:
	if (data->mode != O_RDONLY \|\| !data->frozen \|\| data->ready) {
	error = -EPERM;
	break;
	}
	pm_restore_gfp_mask();
	error = hibernation_snapshot(data->platform_support);
	if (!error) {
	error = put_user(in_suspend, (int __user *)arg);
	data->ready = !freezer_test_done && !error;
	freezer_test_done = false;
	}
	break;

	case SNAPSHOT_ATOMIC_RESTORE:
	snapshot_write_finalize(&data->handle);
	if (data->mode != O_WRONLY \|\| !data->frozen \|\|
	!snapshot_image_loaded(&data->handle)) {
	error = -EPERM;
	break;
	}
	error = hibernation_restore(data->platform_support);
	break;

	case SNAPSHOT_FREE:
	swsusp_free();
	memset(&data->handle, 0, sizeof(struct snapshot_handle));
	data->ready = false;
	/*
	* It is necessary to thaw kernel threads here, because
	* SNAPSHOT_CREATE_IMAGE may be invoked directly after
	* SNAPSHOT_FREE. In that case, if kernel threads were not
	* thawed, the preallocation of memory carried out by
	* hibernation_snapshot() might run into problems (i.e. it
	* might fail or even deadlock).
	*/
	thaw_kernel_threads();
	break;

	case SNAPSHOT_PREF_IMAGE_SIZE:
	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_SIZE:
	size = count_swap_pages(data->swap, 1);
	size <<= PAGE_SHIFT;
	error = put_user(size, (loff_t __user *)arg);
	break;

	case SNAPSHOT_ALLOC_SWAP_PAGE:
	if (data->swap < 0 \|\| data->swap >= MAX_SWAPFILES) {
	error = -ENODEV;
	break;
	}
	offset = alloc_swapdev_block(data->swap);
	if (offset) {
	offset <<= PAGE_SHIFT;
	error = put_user(offset, (loff_t __user *)arg);
	} else {
	error = -ENOSPC;
	}
	break;

	case SNAPSHOT_FREE_SWAP_PAGES:
	if (data->swap < 0 \|\| data->swap >= MAX_SWAPFILES) {
	error = -ENODEV;
	break;
	}
	free_all_swap_pages(data->swap);
	break;

	case SNAPSHOT_S2RAM:
	if (!data->frozen) {
	error = -EPERM;
	break;
	}
	/*
	* Tasks are frozen and the notifiers have been called with
	* PM_HIBERNATION_PREPARE
	*/
	error = suspend_devices_and_enter(PM_SUSPEND_MEM);
	data->ready = false;
	break;

	case SNAPSHOT_PLATFORM_SUPPORT:
	data->platform_support = !!arg;
	break;

	case SNAPSHOT_POWER_OFF:
	if (data->platform_support)
	error = hibernation_platform_enter();
	break;

	case SNAPSHOT_SET_SWAP_AREA:
	if (swsusp_swap_in_use()) {
	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 = new_decode_dev(swap_area.dev);
	if (swdev) {
	offset = swap_area.offset;
	data->swap = swap_type_of(swdev, offset, NULL);
	if (data->swap < 0)
	error = -ENODEV;
	} else {
	data->swap = -1;
	error = -EINVAL;
	}
	}
	break;

	default:
	error = -ENOTTY;

	}

	unlock_device_hotplug();
	mutex_unlock(&system_transition_mutex);

	return error;
	}

	#ifdef CONFIG_COMPAT

	struct compat_resume_swap_area {
	compat_loff_t offset;
	u32 dev;
	} __packed;

	static long
	snapshot_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
	{
	BUILD_BUG_ON(sizeof(loff_t) != sizeof(compat_loff_t));

	switch (cmd) {
	case SNAPSHOT_GET_IMAGE_SIZE:
	case SNAPSHOT_AVAIL_SWAP_SIZE:
	case SNAPSHOT_ALLOC_SWAP_PAGE: {
	compat_loff_t __user *uoffset = compat_ptr(arg);
	loff_t offset;
	mm_segment_t old_fs;
	int err;

	old_fs = get_fs();
	set_fs(KERNEL_DS);
	err = snapshot_ioctl(file, cmd, (unsigned long) &offset);
	set_fs(old_fs);
	if (!err && put_user(offset, uoffset))
	err = -EFAULT;
	return err;
	}

	case SNAPSHOT_CREATE_IMAGE:
	return snapshot_ioctl(file, cmd,
	(unsigned long) compat_ptr(arg));

	case SNAPSHOT_SET_SWAP_AREA: {
	struct compat_resume_swap_area __user *u_swap_area =
	compat_ptr(arg);
	struct resume_swap_area swap_area;
	mm_segment_t old_fs;
	int err;

	err = get_user(swap_area.offset, &u_swap_area->offset);
	err \|= get_user(swap_area.dev, &u_swap_area->dev);
	if (err)
	return -EFAULT;
	old_fs = get_fs();
	set_fs(KERNEL_DS);
	err = snapshot_ioctl(file, SNAPSHOT_SET_SWAP_AREA,
	(unsigned long) &swap_area);
	set_fs(old_fs);
	return err;
	}

	default:
	return snapshot_ioctl(file, cmd, arg);
	}
	}

	#endif /* CONFIG_COMPAT */

	static const struct file_operations snapshot_fops = {
	.open = snapshot_open,
	.release = snapshot_release,
	.read = snapshot_read,
	.write = snapshot_write,
	.llseek = no_llseek,
	.unlocked_ioctl = snapshot_ioctl,
	#ifdef CONFIG_COMPAT
	.compat_ioctl = snapshot_compat_ioctl,
	#endif
	};

	static struct miscdevice snapshot_device = {
	.minor = SNAPSHOT_MINOR,
	.name = "snapshot",
	.fops = &snapshot_fops,
	};

	static int __init snapshot_device_init(void)
	{
	return misc_register(&snapshot_device);
	};

	device_initcall(snapshot_device_init);