Re: [linux-pm] [RFC/RFT][PATCH -mm 2/5] swsusp: userland interface (rev. 2)

Rafael J. Wysocki
2006-01-05T23:32:53Z

Hi,

On Thursday, 5 January 2006 01:26, Greg KH wrote:
> On Thu, Jan 05, 2006 at 01:18:37AM +0100, Pavel Machek wrote:
> > > > +static int __init snapshot_dev_init(void)
> > > > +{
> > > > + int error;
> > > > +
> > > > + error = alloc_chrdev_region(&interface.devno, 0, 1, interface.name);
> > > > + if (error)
> > > > + return error;
> > > > + cdev_init(&interface.cdev, &snapshot_fops);
> > > > + interface.cdev.ops = &snapshot_fops;
> > > > + error = cdev_add(&interface.cdev, interface.devno, 1);
> > > > + if (error)
> > > > + goto Unregister;
> > > > + error = sysfs_create_file(&power_subsys.kset.kobj, &snapshot_attr.attr);
> > >
> > > Heh, that's a neat hack, register a sysfs file that contains the
> > > major:minor (there is a function that will print that the correct way,
> > > if you really want to do that), in sysfs. It's better to just register
> > > a misc character device with the name "snapshot", and then udev will
> > > create your userspace node with the proper major:minor all automatically
> > > for you.
> > >
> > > Unless you want to turn these into syscalls :)
> >
> > Well, I think we simply want to get static major/minor allocated for
> > this device. It really uses read/write, IIRC, so no, I do not think we
> > want to make it a syscall.
>
> Ok, then I'd recommend using the misc device, dynamic for now, and
> reserve one when you get a bit closer to merging into mainline.

Do you mean something like in the appended patch?

Rafael

Index: linux-2.6.15-mm1/kernel/power/user.c
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6.15-mm1/kernel/power/user.c 2006-01-06 00:22:52.000000000 +0100
@@ -0,0 +1,294 @@
+/*
+ * linux/kernel/power/user.c
+ *
+ * This file provides the user space interface for software suspend/resume.
+ *
+ * Copyright (C) 2005 Rafael J. Wysocki <rjw@sisk.pl>
+ *
+ * This file is released under the GPLv2.
+ *
+ */
+
+#include <linux/suspend.h>
+#include <linux/syscalls.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/uaccess.h>
+#include <linux/fs.h>
+
+#include "power.h"
+
+static struct snapshot_data {
+ struct snapshot_handle handle;
+ int swap;
+ struct bitmap_page *bitmap;
+ int mode;
+ char frozen;
+ char ready;
+} snapshot_state;
+
+static atomic_t device_available = ATOMIC_INIT(1);
+
+int snapshot_open(struct inode *inode, struct file *filp)
+{
+ struct snapshot_data *data;
+
+ if (!atomic_dec_and_test(&device_available)) {
+ atomic_inc(&device_available);
+ return -EBUSY;
+ }
+
+ if ((filp->f_flags & O_ACCMODE) == O_RDWR)
+ return -ENOSYS;
+
+ 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) {
+ data->swap = swsusp_get_swap_index();
+ data->mode = O_RDONLY;
+ } else {
+ data->swap = -1;
+ data->mode = O_WRONLY;
+ }
+ data->bitmap = NULL;
+ data->frozen = 0;
+ data->ready = 0;
+
+ return 0;
+}
+
+int snapshot_release(struct inode *inode, struct file *filp)
+{
+ struct snapshot_data *data;
+
+ swsusp_free();
+ data = filp->private_data;
+ free_all_swap_pages(data->swap, data->bitmap);
+ free_bitmap(data->bitmap);
+ if (data->frozen) {
+ down(&pm_sem);
+ thaw_processes();
+ enable_nonboot_cpus();
+ up(&pm_sem);
+ }
+ atomic_inc(&device_available);
+ 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;
+
+ data = filp->private_data;
+ res = snapshot_read_next(&data->handle, count);
+ if (res > 0) {
+ if (copy_to_user(buf, data_of(data->handle), res))
+ res = -EFAULT;
+ else
+ *offp = data->handle.offset;
+ }
+ 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;
+
+ data = filp->private_data;
+ res = snapshot_write_next(&data->handle, count);
+ if (res > 0) {
+ if (copy_from_user(data_of(data->handle), buf, res))
+ res = -EFAULT;
+ else
+ *offp = data->handle.offset;
+ }
+ return res;
+}
+
+static int snapshot_ioctl(struct inode *inode, struct file *filp,
+ unsigned int cmd, unsigned long arg)
+{
+ int error = 0;
+ struct snapshot_data *data;
+ unsigned long offset;
+ unsigned int n;
+
+ 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;
+
+ data = filp->private_data;
+
+ switch (cmd) {
+
+ case SNAPSHOT_IOCFREEZE:
+ if (data->frozen)
+ break;
+ sys_sync();
+ down(&pm_sem);
+ disable_nonboot_cpus();
+ if (freeze_processes())
+ error = -EBUSY;
+ up(&pm_sem);
+ if (!error)
+ data->frozen = 1;
+ break;
+
+ case SNAPSHOT_IOCUNFREEZE:
+ if (!data->frozen)
+ break;
+ down(&pm_sem);
+ thaw_processes();
+ enable_nonboot_cpus();
+ up(&pm_sem);
+ data->frozen = 0;
+ break;
+
+ case SNAPSHOT_IOCATOMIC_SNAPSHOT:
+ if (data->mode != O_RDONLY || !data->frozen || data->ready) {
+ error = -EPERM;
+ break;
+ }
+ down(&pm_sem);
+ pm_prepare_console();
+ /* Free memory before shutting down devices. */
+ error = swsusp_shrink_memory();
+ if (!error) {
+ error = device_suspend(PMSG_FREEZE);
+ if (!error) {
+ in_suspend = 1;
+ error = swsusp_suspend();
+ device_resume();
+ }
+ }
+ pm_restore_console();
+ up(&pm_sem);
+ if (!error)
+ error = put_user(in_suspend, (unsigned int __user *)arg);
+ if (!error)
+ data->ready = 1;
+ break;
+
+ case SNAPSHOT_IOCATOMIC_RESTORE:
+ if (data->mode != O_WRONLY || !data->frozen ||
+ !snapshot_image_loaded(&data->handle)) {
+ error = -EPERM;
+ break;
+ }
+ down(&pm_sem);
+ pm_prepare_console();
+ error = device_suspend(PMSG_FREEZE);
+ if (!error) {
+ mb();
+ error = swsusp_resume();
+ device_resume();
+ }
+ pm_restore_console();
+ up(&pm_sem);
+ break;
+
+ case SNAPSHOT_IOCFREE:
+ swsusp_free();
+ memset(&data->handle, 0, sizeof(struct snapshot_handle));
+ data->ready = 0;
+ break;
+
+ case SNAPSHOT_IOCSET_IMAGE_SIZE:
+ image_size = arg;
+ break;
+
+ case SNAPSHOT_IOCAVAIL_SWAP:
+ n = swsusp_available_swap(data->swap);
+ error = put_user(n, (unsigned int __user *)arg);
+ break;
+
+ case SNAPSHOT_IOCGET_SWAP_PAGE:
+ if (!access_ok(VERIFY_WRITE, (unsigned long __user *)arg, _IOC_SIZE(cmd))) {
+ error = -EINVAL;
+ break;
+ }
+ if (data->swap < 0 || data->swap >= MAX_SWAPFILES) {
+ error = -ENODEV;
+ break;
+ }
+ if (!data->bitmap) {
+ data->bitmap = alloc_bitmap(swsusp_total_swap(data->swap));
+ if (!data->bitmap) {
+ error = -ENOMEM;
+ break;
+ }
+ }
+ offset = alloc_swap_page(data->swap, data->bitmap);
+ if (offset)
+ __put_user(offset, (unsigned long __user *)arg);
+ else
+ error = -ENOSPC;
+ break;
+
+ case SNAPSHOT_IOCFREE_SWAP_PAGES:
+ if (data->swap >= 0 && data->swap < MAX_SWAPFILES) {
+ error = -ENODEV;
+ break;
+ }
+ free_all_swap_pages(data->swap, data->bitmap);
+ free_bitmap(data->bitmap);
+ data->bitmap = NULL;
+ break;
+
+ case SNAPSHOT_IOCSET_SWAP_FILE:
+ if (!data->bitmap) {
+ /*
+ * User space encodes device types as two-byte values,
+ * so we need to recode them
+ */
+ data->swap = swsusp_get_swap_index_of(old_decode_dev(arg));
+ if (data->swap < 0)
+ error = -ENODEV;
+ } else {
+ error = -EPERM;
+ }
+ break;
+
+ default:
+ error = -ENOTTY;
+
+ }
+
+ return error;
+}
+
+static struct file_operations snapshot_fops = {
+ .open = snapshot_open,
+ .release = snapshot_release,
+ .read = snapshot_read,
+ .write = snapshot_write,
+ .llseek = no_llseek,
+ .ioctl = snapshot_ioctl,
+};
+
+static struct miscdevice snapshot_device = {
+ .minor = MISC_DYNAMIC_MINOR,
+ .name = "snapshot",
+ .fops = &snapshot_fops,
+};
+
+static int __init snapshot_device_init(void)
+{
+ return misc_register(&snapshot_device);
+};
+
+device_initcall(snapshot_device_init);