3 files changed, 621 insertions, 0 deletions

diff --git a/fs/Kconfig b/fs/Kconfig
index 9f7270f36b2a..525da2e8f73b 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -62,6 +62,16 @@ source "fs/autofs/Kconfig"
 source "fs/autofs4/Kconfig"
 source "fs/fuse/Kconfig"
 
+config CUSE
+        tristate "Character device in Userpace support"
+        depends on FUSE_FS
+        help
+          This FUSE extension allows character devices to be
+          implemented in userspace.
+
+          If you want to develop or use userspace character device
+          based on CUSE, answer Y or M.
+
 config GENERIC_ACL
         bool
         select FS_POSIX_ACL
diff --git a/fs/fuse/Makefile b/fs/fuse/Makefile
index 72437065f6ad..e95eeb445e58 100644
--- a/fs/fuse/Makefile
+++ b/fs/fuse/Makefile
@@ -3,5 +3,6 @@
 #
 
 obj-$(CONFIG_FUSE_FS) += fuse.o
+obj-$(CONFIG_CUSE) += cuse.o
 
 fuse-objs := dev.o dir.o file.o inode.o control.o
diff --git a/fs/fuse/cuse.c b/fs/fuse/cuse.c
new file mode 100644
index 000000000000..de792dcf3274
--- /dev/null
+++ b/fs/fuse/cuse.c
@@ -0,0 +1,610 @@
+/*
+ * CUSE: Character device in Userspace
+ *
+ * Copyright (C) 2008-2009  SUSE Linux Products GmbH
+ * Copyright (C) 2008-2009  Tejun Heo <tj@kernel.org>
+ *
+ * This file is released under the GPLv2.
+ *
+ * CUSE enables character devices to be implemented from userland much
+ * like FUSE allows filesystems.  On initialization /dev/cuse is
+ * created.  By opening the file and replying to the CUSE_INIT request
+ * userland CUSE server can create a character device.  After that the
+ * operation is very similar to FUSE.
+ *
+ * A CUSE instance involves the following objects.
+ *
+ * cuse_conn    : contains fuse_conn and serves as bonding structure
+ * channel      : file handle connected to the userland CUSE server
+ * cdev         : the implemented character device
+ * dev          : generic device for cdev
+ *
+ * Note that 'channel' is what 'dev' is in FUSE.  As CUSE deals with
+ * devices, it's called 'channel' to reduce confusion.
+ *
+ * channel determines when the character device dies.  When channel is
+ * closed, everything begins to destruct.  The cuse_conn is taken off
+ * the lookup table preventing further access from cdev, cdev and
+ * generic device are removed and the base reference of cuse_conn is
+ * put.
+ *
+ * On each open, the matching cuse_conn is looked up and if found an
+ * additional reference is taken which is released when the file is
+ * closed.
+ */
+
+#include <linux/fuse.h>
+#include <linux/cdev.h>
+#include <linux/device.h>
+#include <linux/file.h>
+#include <linux/fs.h>
+#include <linux/kdev_t.h>
+#include <linux/kthread.h>
+#include <linux/list.h>
+#include <linux/magic.h>
+#include <linux/miscdevice.h>
+#include <linux/mutex.h>
+#include <linux/spinlock.h>
+#include <linux/stat.h>
+
+#include "fuse_i.h"
+
+#define CUSE_CONNTBL_LEN        64
+
+struct cuse_conn {
+        struct list_head        list;   /* linked on cuse_conntbl */
+        struct fuse_conn        fc;     /* fuse connection */
+        struct cdev             *cdev;  /* associated character device */
+        struct device           *dev;   /* device representing @cdev */
+
+        /* init parameters, set once during initialization */
+        bool                    unrestricted_ioctl;
+};
+
+static DEFINE_SPINLOCK(cuse_lock);              /* protects cuse_conntbl */
+static struct list_head cuse_conntbl[CUSE_CONNTBL_LEN];
+static struct class *cuse_class;
+
+static struct cuse_conn *fc_to_cc(struct fuse_conn *fc)
+{
+        return container_of(fc, struct cuse_conn, fc);
+}
+
+static struct list_head *cuse_conntbl_head(dev_t devt)
+{
+        return &cuse_conntbl[(MAJOR(devt) + MINOR(devt)) % CUSE_CONNTBL_LEN];
+}
+
+
+/**************************************************************************
+ * CUSE frontend operations
+ *
+ * These are file operations for the character device.
+ *
+ * On open, CUSE opens a file from the FUSE mnt and stores it to
+ * private_data of the open file.  All other ops call FUSE ops on the
+ * FUSE file.
+ */
+
+static ssize_t cuse_read(struct file *file, char __user *buf, size_t count,
+                         loff_t *ppos)
+{
+        loff_t pos = 0;
+
+        return fuse_direct_io(file, buf, count, &pos, 0);
+}
+
+static ssize_t cuse_write(struct file *file, const char __user *buf,
+                          size_t count, loff_t *ppos)
+{
+        loff_t pos = 0;
+        /*
+         * No locking or generic_write_checks(), the server is
+         * responsible for locking and sanity checks.
+         */
+        return fuse_direct_io(file, buf, count, &pos, 1);
+}
+
+static int cuse_open(struct inode *inode, struct file *file)
+{
+        dev_t devt = inode->i_cdev->dev;
+        struct cuse_conn *cc = NULL, *pos;
+        int rc;
+
+        /* look up and get the connection */
+        spin_lock(&cuse_lock);
+        list_for_each_entry(pos, cuse_conntbl_head(devt), list)
+                if (pos->dev->devt == devt) {
+                        fuse_conn_get(&pos->fc);
+                        cc = pos;
+                        break;
+                }
+        spin_unlock(&cuse_lock);
+
+        /* dead? */
+        if (!cc)
+                return -ENODEV;
+
+        /*
+         * Generic permission check is already done against the chrdev
+         * file, proceed to open.
+         */
+        rc = fuse_do_open(&cc->fc, 0, file, 0);
+        if (rc)
+                fuse_conn_put(&cc->fc);
+        return rc;
+}
+
+static int cuse_release(struct inode *inode, struct file *file)
+{
+        struct fuse_file *ff = file->private_data;
+        struct fuse_conn *fc = ff->fc;
+
+        fuse_sync_release(ff, file->f_flags);
+        fuse_conn_put(fc);
+
+        return 0;
+}
+
+static long cuse_file_ioctl(struct file *file, unsigned int cmd,
+                            unsigned long arg)
+{
+        struct fuse_file *ff = file->private_data;
+        struct cuse_conn *cc = fc_to_cc(ff->fc);
+        unsigned int flags = 0;
+
+        if (cc->unrestricted_ioctl)
+                flags |= FUSE_IOCTL_UNRESTRICTED;
+
+        return fuse_do_ioctl(file, cmd, arg, flags);
+}
+
+static long cuse_file_compat_ioctl(struct file *file, unsigned int cmd,
+                                   unsigned long arg)
+{
+        struct fuse_file *ff = file->private_data;
+        struct cuse_conn *cc = fc_to_cc(ff->fc);
+        unsigned int flags = FUSE_IOCTL_COMPAT;
+
+        if (cc->unrestricted_ioctl)
+                flags |= FUSE_IOCTL_UNRESTRICTED;
+
+        return fuse_do_ioctl(file, cmd, arg, flags);
+}
+
+static const struct file_operations cuse_frontend_fops = {
+        .owner                  = THIS_MODULE,
+        .read                   = cuse_read,
+        .write                  = cuse_write,
+        .open                   = cuse_open,
+        .release                = cuse_release,
+        .unlocked_ioctl         = cuse_file_ioctl,
+        .compat_ioctl           = cuse_file_compat_ioctl,
+        .poll                   = fuse_file_poll,
+};
+
+
+/**************************************************************************
+ * CUSE channel initialization and destruction
+ */
+
+struct cuse_devinfo {
+        const char              *name;
+};
+
+/**
+ * cuse_parse_one - parse one key=value pair
+ * @pp: i/o parameter for the current position
+ * @end: points to one past the end of the packed string
+ * @keyp: out parameter for key
+ * @valp: out parameter for value
+ *
+ * *@pp points to packed strings - "key0=val0\0key1=val1\0" which ends
+ * at @end - 1.  This function parses one pair and set *@keyp to the
+ * start of the key and *@valp to the start of the value.  Note that
+ * the original string is modified such that the key string is
+ * terminated with '\0'.  *@pp is updated to point to the next string.
+ *
+ * RETURNS:
+ * 1 on successful parse, 0 on EOF, -errno on failure.
+ */
+static int cuse_parse_one(char **pp, char *end, char **keyp, char **valp)
+{
+        char *p = *pp;
+        char *key, *val;
+
+        while (p < end && *p == '\0')
+                p++;
+        if (p == end)
+                return 0;
+
+        if (end[-1] != '\0') {
+                printk(KERN_ERR "CUSE: info not properly terminated\n");
+                return -EINVAL;
+        }
+
+        key = val = p;
+        p += strlen(p);
+
+        if (valp) {
+                strsep(&val, "=");
+                if (!val)
+                        val = key + strlen(key);
+                key = strstrip(key);
+                val = strstrip(val);
+        } else
+                key = strstrip(key);
+
+        if (!strlen(key)) {
+                printk(KERN_ERR "CUSE: zero length info key specified\n");
+                return -EINVAL;
+        }
+
+        *pp = p;
+        *keyp = key;
+        if (valp)
+                *valp = val;
+
+        return 1;
+}
+
+/**
+ * cuse_parse_dev_info - parse device info
+ * @p: device info string
+ * @len: length of device info string
+ * @devinfo: out parameter for parsed device info
+ *
+ * Parse @p to extract device info and store it into @devinfo.  String
+ * pointed to by @p is modified by parsing and @devinfo points into
+ * them, so @p shouldn't be freed while @devinfo is in use.
+ *
+ * RETURNS:
+ * 0 on success, -errno on failure.
+ */
+static int cuse_parse_devinfo(char *p, size_t len, struct cuse_devinfo *devinfo)
+{
+        char *end = p + len;
+        char *key, *val;
+        int rc;
+
+        while (true) {
+                rc = cuse_parse_one(&p, end, &key, &val);
+                if (rc < 0)
+                        return rc;
+                if (!rc)
+                        break;
+                if (strcmp(key, "DEVNAME") == 0)
+                        devinfo->name = val;
+                else
+                        printk(KERN_WARNING "CUSE: unknown device info \"%s\"\n",
+                               key);
+        }
+
+        if (!devinfo->name || !strlen(devinfo->name)) {
+                printk(KERN_ERR "CUSE: DEVNAME unspecified\n");
+                return -EINVAL;
+        }
+
+        return 0;
+}
+
+static void cuse_gendev_release(struct device *dev)
+{
+        kfree(dev);
+}
+
+/**
+ * cuse_process_init_reply - finish initializing CUSE channel
+ *
+ * This function creates the character device and sets up all the
+ * required data structures for it.  Please read the comment at the
+ * top of this file for high level overview.
+ */
+static void cuse_process_init_reply(struct fuse_conn *fc, struct fuse_req *req)
+{
+        struct cuse_conn *cc = fc_to_cc(fc);
+        struct cuse_init_out *arg = &req->misc.cuse_init_out;
+        struct page *page = req->pages[0];
+        struct cuse_devinfo devinfo = { };
+        struct device *dev;
+        struct cdev *cdev;
+        dev_t devt;
+        int rc;
+
+        if (req->out.h.error ||
+            arg->major != FUSE_KERNEL_VERSION || arg->minor < 11) {
+                goto err;
+        }
+
+        fc->minor = arg->minor;
+        fc->max_read = max_t(unsigned, arg->max_read, 4096);
+        fc->max_write = max_t(unsigned, arg->max_write, 4096);
+
+        /* parse init reply */
+        cc->unrestricted_ioctl = arg->flags & CUSE_UNRESTRICTED_IOCTL;
+
+        rc = cuse_parse_devinfo(page_address(page), req->out.args[1].size,
+                                &devinfo);
+        if (rc)
+                goto err;
+
+        /* determine and reserve devt */
+        devt = MKDEV(arg->dev_major, arg->dev_minor);
+        if (!MAJOR(devt))
+                rc = alloc_chrdev_region(&devt, MINOR(devt), 1, devinfo.name);
+        else
+                rc = register_chrdev_region(devt, 1, devinfo.name);
+        if (rc) {
+                printk(KERN_ERR "CUSE: failed to register chrdev region\n");
+                goto err;
+        }
+
+        /* devt determined, create device */
+        rc = -ENOMEM;
+        dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+        if (!dev)
+                goto err_region;
+
+        device_initialize(dev);
+        dev_set_uevent_suppress(dev, 1);
+        dev->class = cuse_class;
+        dev->devt = devt;
+        dev->release = cuse_gendev_release;
+        dev_set_drvdata(dev, cc);
+        dev_set_name(dev, "%s", devinfo.name);
+
+        rc = device_add(dev);
+        if (rc)
+                goto err_device;
+
+        /* register cdev */
+        rc = -ENOMEM;
+        cdev = cdev_alloc();
+        if (!cdev)
+                goto err_device;
+
+        cdev->owner = THIS_MODULE;
+        cdev->ops = &cuse_frontend_fops;
+
+        rc = cdev_add(cdev, devt, 1);
+        if (rc)
+                goto err_cdev;
+
+        cc->dev = dev;
+        cc->cdev = cdev;
+
+        /* make the device available */
+        spin_lock(&cuse_lock);
+        list_add(&cc->list, cuse_conntbl_head(devt));
+        spin_unlock(&cuse_lock);
+
+        /* announce device availability */
+        dev_set_uevent_suppress(dev, 0);
+        kobject_uevent(&dev->kobj, KOBJ_ADD);
+out:
+        __free_page(page);
+        return;
+
+err_cdev:
+        cdev_del(cdev);
+err_device:
+        put_device(dev);
+err_region:
+        unregister_chrdev_region(devt, 1);
+err:
+        fc->conn_error = 1;
+        goto out;
+}
+
+static int cuse_send_init(struct cuse_conn *cc)
+{
+        int rc;
+        struct fuse_req *req;
+        struct page *page;
+        struct fuse_conn *fc = &cc->fc;
+        struct cuse_init_in *arg;
+
+        BUILD_BUG_ON(CUSE_INIT_INFO_MAX > PAGE_SIZE);
+
+        req = fuse_get_req(fc);
+        if (IS_ERR(req)) {
+                rc = PTR_ERR(req);
+                goto err;
+        }
+
+        rc = -ENOMEM;
+        page = alloc_page(GFP_KERNEL | __GFP_ZERO);
+        if (!page)
+                goto err_put_req;
+
+        arg = &req->misc.cuse_init_in;
+        arg->major = FUSE_KERNEL_VERSION;
+        arg->minor = FUSE_KERNEL_MINOR_VERSION;
+        arg->flags |= CUSE_UNRESTRICTED_IOCTL;
+        req->in.h.opcode = CUSE_INIT;
+        req->in.numargs = 1;
+        req->in.args[0].size = sizeof(struct cuse_init_in);
+        req->in.args[0].value = arg;
+        req->out.numargs = 2;
+        req->out.args[0].size = sizeof(struct cuse_init_out);
+        req->out.args[0].value = &req->misc.cuse_init_out;
+        req->out.args[1].size = CUSE_INIT_INFO_MAX;
+        req->out.argvar = 1;
+        req->out.argpages = 1;
+        req->pages[0] = page;
+        req->num_pages = 1;
+        req->end = cuse_process_init_reply;
+        fuse_request_send_background(fc, req);
+
+        return 0;
+
+err_put_req:
+        fuse_put_request(fc, req);
+err:
+        return rc;
+}
+
+static void cuse_fc_release(struct fuse_conn *fc)
+{
+        struct cuse_conn *cc = fc_to_cc(fc);
+        kfree(cc);
+}
+
+/**
+ * cuse_channel_open - open method for /dev/cuse
+ * @inode: inode for /dev/cuse
+ * @file: file struct being opened
+ *
+ * Userland CUSE server can create a CUSE device by opening /dev/cuse
+ * and replying to the initilaization request kernel sends.  This
+ * function is responsible for handling CUSE device initialization.
+ * Because the fd opened by this function is used during
+ * initialization, this function only creates cuse_conn and sends
+ * init.  The rest is delegated to a kthread.
+ *
+ * RETURNS:
+ * 0 on success, -errno on failure.
+ */
+static int cuse_channel_open(struct inode *inode, struct file *file)
+{
+        struct cuse_conn *cc;
+        int rc;
+
+        /* set up cuse_conn */
+        cc = kzalloc(sizeof(*cc), GFP_KERNEL);
+        if (!cc)
+                return -ENOMEM;
+
+        fuse_conn_init(&cc->fc);
+
+        INIT_LIST_HEAD(&cc->list);
+        cc->fc.release = cuse_fc_release;
+
+        cc->fc.connected = 1;
+        cc->fc.blocked = 0;
+        rc = cuse_send_init(cc);
+        if (rc) {
+                fuse_conn_put(&cc->fc);
+                return rc;
+        }
+        file->private_data = &cc->fc;   /* channel owns base reference to cc */
+
+        return 0;
+}
+
+/**
+ * cuse_channel_release - release method for /dev/cuse
+ * @inode: inode for /dev/cuse
+ * @file: file struct being closed
+ *
+ * Disconnect the channel, deregister CUSE device and initiate
+ * destruction by putting the default reference.
+ *
+ * RETURNS:
+ * 0 on success, -errno on failure.
+ */
+static int cuse_channel_release(struct inode *inode, struct file *file)
+{
+        struct cuse_conn *cc = fc_to_cc(file->private_data);
+        int rc;
+
+        /* remove from the conntbl, no more access from this point on */
+        spin_lock(&cuse_lock);
+        list_del_init(&cc->list);
+        spin_unlock(&cuse_lock);
+
+        /* remove device */
+        if (cc->dev)
+                device_unregister(cc->dev);
+        if (cc->cdev) {
+                unregister_chrdev_region(cc->cdev->dev, 1);
+                cdev_del(cc->cdev);
+        }
+
+        /* kill connection and shutdown channel */
+        fuse_conn_kill(&cc->fc);
+        rc = fuse_dev_release(inode, file);     /* puts the base reference */
+
+        return rc;
+}
+
+static struct file_operations cuse_channel_fops; /* initialized during init */
+
+
+/**************************************************************************
+ * Misc stuff and module initializatiion
+ *
+ * CUSE exports the same set of attributes to sysfs as fusectl.
+ */
+
+static ssize_t cuse_class_waiting_show(struct device *dev,
+                                       struct device_attribute *attr, char *buf)
+{
+        struct cuse_conn *cc = dev_get_drvdata(dev);
+
+        return sprintf(buf, "%d\n", atomic_read(&cc->fc.num_waiting));
+}
+
+static ssize_t cuse_class_abort_store(struct device *dev,
+                                      struct device_attribute *attr,
+                                      const char *buf, size_t count)
+{
+        struct cuse_conn *cc = dev_get_drvdata(dev);
+
+        fuse_abort_conn(&cc->fc);
+        return count;
+}
+
+static struct device_attribute cuse_class_dev_attrs[] = {
+        __ATTR(waiting, S_IFREG | 0400, cuse_class_waiting_show, NULL),
+        __ATTR(abort, S_IFREG | 0200, NULL, cuse_class_abort_store),
+        { }
+};
+
+static struct miscdevice cuse_miscdev = {
+        .minor          = MISC_DYNAMIC_MINOR,
+        .name           = "cuse",
+        .fops           = &cuse_channel_fops,
+};
+
+static int __init cuse_init(void)
+{
+        int i, rc;
+
+        /* init conntbl */
+        for (i = 0; i < CUSE_CONNTBL_LEN; i++)
+                INIT_LIST_HEAD(&cuse_conntbl[i]);
+
+        /* inherit and extend fuse_dev_operations */
+        cuse_channel_fops               = fuse_dev_operations;
+        cuse_channel_fops.owner         = THIS_MODULE;
+        cuse_channel_fops.open          = cuse_channel_open;
+        cuse_channel_fops.release       = cuse_channel_release;
+
+        cuse_class = class_create(THIS_MODULE, "cuse");
+        if (IS_ERR(cuse_class))
+                return PTR_ERR(cuse_class);
+
+        cuse_class->dev_attrs = cuse_class_dev_attrs;
+
+        rc = misc_register(&cuse_miscdev);
+        if (rc) {
+                class_destroy(cuse_class);
+                return rc;
+        }
+
+        return 0;
+}
+
+static void __exit cuse_exit(void)
+{
+        misc_deregister(&cuse_miscdev);
+        class_destroy(cuse_class);
+}
+
+module_init(cuse_init);
+module_exit(cuse_exit);
+
+MODULE_AUTHOR("Tejun Heo <tj@kernel.org>");
+MODULE_DESCRIPTION("Character device in Userspace");
+MODULE_LICENSE("GPL");