source: trunk/packages/xen-3.1/xen-3.1/linux-2.6-xen-sparse/drivers/xen/blktap/xenbus.c @ 34

/* drivers/xen/blktap/xenbus.c
 *
 * Xenbus code for blktap
 *
 * Copyright (c) 2004-2005, Andrew Warfield and Julian Chesterfield
 *
 * Based on the blkback xenbus code:
 *
 * Copyright (C) 2005 Rusty Russell <rusty@rustcorp.com.au>
 * Copyright (C) 2005 XenSource Ltd
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License version 2
 * as published by the Free Software Foundation; or, when distributed
 * separately from the Linux kernel or incorporated into other
 * software packages, subject to the following license:
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this source file (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use, copy, modify,
 * merge, publish, distribute, sublicense, and/or sell copies of the Software,
 * and to permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

#include <stdarg.h>
#include <linux/module.h>
#include <linux/kthread.h>
#include <xen/xenbus.h>
#include "common.h"


struct backend_info
{
        struct xenbus_device *dev;
        blkif_t *blkif;
        struct xenbus_watch backend_watch;
        int xenbus_id;
        int group_added;
};


static void connect(struct backend_info *);
static int connect_ring(struct backend_info *);
static int blktap_remove(struct xenbus_device *dev);
static int blktap_probe(struct xenbus_device *dev,
                         const struct xenbus_device_id *id);
static void tap_backend_changed(struct xenbus_watch *, const char **,
                            unsigned int);
static void tap_frontend_changed(struct xenbus_device *dev,
                             enum xenbus_state frontend_state);

static int strsep_len(const char *str, char c, unsigned int len)
{
        unsigned int i;

        for (i = 0; str[i]; i++)
                if (str[i] == c) {
                        if (len == 0)
                                return i;
                        len--;
                }
        return (len == 0) ? i : -ERANGE;
}

static long get_id(const char *str)
{
        int len,end;
        const char *ptr;
        char *tptr, num[10];
        
        len = strsep_len(str, '/', 2);
        end = strlen(str);
        if ( (len < 0) || (end < 0) ) return -1;
        
        ptr = str + len + 1;
        strncpy(num,ptr,end - len);
        tptr = num + (end - (len + 1));
        *tptr = '\0';
        DPRINTK("Get_id called for %s (%s)\n",str,num);
        
        return simple_strtol(num, NULL, 10);
}                               

static int blktap_name(blkif_t *blkif, char *buf)
{
        char *devpath, *devname;
        struct xenbus_device *dev = blkif->be->dev;

        devpath = xenbus_read(XBT_NIL, dev->nodename, "dev", NULL);
        if (IS_ERR(devpath)) 
                return PTR_ERR(devpath);
        
        if ((devname = strstr(devpath, "/dev/")) != NULL)
                devname += strlen("/dev/");
        else
                devname  = devpath;

        snprintf(buf, TASK_COMM_LEN, "blktap.%d.%s", blkif->domid, devname);
        kfree(devpath);
        
        return 0;
}

/****************************************************************
 *  sysfs interface for VBD I/O requests
 */

#define VBD_SHOW(name, format, args...)                                 \
        static ssize_t show_##name(struct device *_dev,                 \
                                   struct device_attribute *attr,       \
                                   char *buf)                           \
        {                                                               \
                struct xenbus_device *dev = to_xenbus_device(_dev);     \
                struct backend_info *be = dev->dev.driver_data;         \
                                                                        \
                return sprintf(buf, format, ##args);                    \
        }                                                               \
        DEVICE_ATTR(name, S_IRUGO, show_##name, NULL)

VBD_SHOW(tap_oo_req,  "%d\n", be->blkif->st_oo_req);
VBD_SHOW(tap_rd_req,  "%d\n", be->blkif->st_rd_req);
VBD_SHOW(tap_wr_req,  "%d\n", be->blkif->st_wr_req);
VBD_SHOW(tap_rd_sect, "%d\n", be->blkif->st_rd_sect);
VBD_SHOW(tap_wr_sect, "%d\n", be->blkif->st_wr_sect);

static struct attribute *tapstat_attrs[] = {
        &dev_attr_tap_oo_req.attr,
        &dev_attr_tap_rd_req.attr,
        &dev_attr_tap_wr_req.attr,
        &dev_attr_tap_rd_sect.attr,
        &dev_attr_tap_wr_sect.attr,
        NULL
};

static struct attribute_group tapstat_group = {
        .name = "statistics",
        .attrs = tapstat_attrs,
};

int xentap_sysfs_addif(struct xenbus_device *dev)
{
        int err;
        struct backend_info *be = dev->dev.driver_data;
        err = sysfs_create_group(&dev->dev.kobj, &tapstat_group);
        if (!err)
                be->group_added = 1;
        return err;
}

void xentap_sysfs_delif(struct xenbus_device *dev)
{
        sysfs_remove_group(&dev->dev.kobj, &tapstat_group);
}

static int blktap_remove(struct xenbus_device *dev)
{
        struct backend_info *be = dev->dev.driver_data;

        if (be->backend_watch.node) {
                unregister_xenbus_watch(&be->backend_watch);
                kfree(be->backend_watch.node);
                be->backend_watch.node = NULL;
        }
        if (be->blkif) {
                if (be->blkif->xenblkd)
                        kthread_stop(be->blkif->xenblkd);
                signal_tapdisk(be->blkif->dev_num);
                tap_blkif_free(be->blkif);
                be->blkif = NULL;
        }
        if (be->group_added)
                xentap_sysfs_delif(be->dev);
        kfree(be);
        dev->dev.driver_data = NULL;
        return 0;
}

static void tap_update_blkif_status(blkif_t *blkif)
{ 
        int err;
        char name[TASK_COMM_LEN];

        /* Not ready to connect? */
        if(!blkif->irq || !blkif->sectors) {
                return;
        } 

        /* Already connected? */
        if (blkif->be->dev->state == XenbusStateConnected)
                return;

        /* Attempt to connect: exit if we fail to. */
        connect(blkif->be);
        if (blkif->be->dev->state != XenbusStateConnected)
                return;

        err = blktap_name(blkif, name);
        if (err) {
                xenbus_dev_error(blkif->be->dev, err, "get blktap dev name");
                return;
        }

        err = xentap_sysfs_addif(blkif->be->dev);
        if (err) {
                xenbus_dev_fatal(blkif->be->dev, err, 
                                 "creating sysfs entries");
                return;
        }

        blkif->xenblkd = kthread_run(tap_blkif_schedule, blkif, name);
        if (IS_ERR(blkif->xenblkd)) {
                err = PTR_ERR(blkif->xenblkd);
                blkif->xenblkd = NULL;
                xenbus_dev_fatal(blkif->be->dev, err, "start xenblkd");
                WPRINTK("Error starting thread\n");
        }
}

/**
 * Entry point to this code when a new device is created.  Allocate
 * the basic structures, and watch the store waiting for the
 * user-space program to tell us the physical device info.  Switch to
 * InitWait.
 */
static int blktap_probe(struct xenbus_device *dev,
                         const struct xenbus_device_id *id)
{
        int err;
        struct backend_info *be = kzalloc(sizeof(struct backend_info),
                                          GFP_KERNEL);
        if (!be) {
                xenbus_dev_fatal(dev, -ENOMEM,
                                 "allocating backend structure");
                return -ENOMEM;
        }

        be->dev = dev;
        dev->dev.driver_data = be;
        be->xenbus_id = get_id(dev->nodename);

        be->blkif = tap_alloc_blkif(dev->otherend_id);
        if (IS_ERR(be->blkif)) {
                err = PTR_ERR(be->blkif);
                be->blkif = NULL;
                xenbus_dev_fatal(dev, err, "creating block interface");
                goto fail;
        }

        /* setup back pointer */
        be->blkif->be = be;
        be->blkif->sectors = 0;

        /* set a watch on disk info, waiting for userspace to update details*/
        err = xenbus_watch_path2(dev, dev->nodename, "info",
                                 &be->backend_watch, tap_backend_changed);
        if (err)
                goto fail;
        
        err = xenbus_switch_state(dev, XenbusStateInitWait);
        if (err)
                goto fail;
        return 0;

fail:
        DPRINTK("blktap probe failed\n");
        blktap_remove(dev);
        return err;
}


/**
 * Callback received when the user space code has placed the device
 * information in xenstore. 
 */
static void tap_backend_changed(struct xenbus_watch *watch,
                            const char **vec, unsigned int len)
{
        int err;
        unsigned long info;
        struct backend_info *be
                = container_of(watch, struct backend_info, backend_watch);
        struct xenbus_device *dev = be->dev;
        
        /** 
         * Check to see whether userspace code has opened the image 
         * and written sector
         * and disk info to xenstore
         */
        err = xenbus_gather(XBT_NIL, dev->nodename, "info", "%lu", &info, 
                            NULL);
        if (XENBUS_EXIST_ERR(err))
                return;
        if (err) {
                xenbus_dev_error(dev, err, "getting info");
                return;
        }

        DPRINTK("Userspace update on disk info, %lu\n",info);

        err = xenbus_gather(XBT_NIL, dev->nodename, "sectors", "%llu", 
                            &be->blkif->sectors, NULL);

        /* Associate tap dev with domid*/
        be->blkif->dev_num = dom_to_devid(be->blkif->domid, be->xenbus_id, 
                                          be->blkif);
        DPRINTK("Thread started for domid [%d], connecting disk\n", 
                be->blkif->dev_num);

        tap_update_blkif_status(be->blkif);
}

/**
 * Callback received when the frontend's state changes.
 */
static void tap_frontend_changed(struct xenbus_device *dev,
                             enum xenbus_state frontend_state)
{
        struct backend_info *be = dev->dev.driver_data;
        int err;

        DPRINTK("\n");

        switch (frontend_state) {
        case XenbusStateInitialising:
                if (dev->state == XenbusStateClosed) {
                        printk(KERN_INFO "%s: %s: prepare for reconnect\n",
                               __FUNCTION__, dev->nodename);
                        xenbus_switch_state(dev, XenbusStateInitWait);
                }
                break;

        case XenbusStateInitialised:
        case XenbusStateConnected:
                /* Ensure we connect even when two watches fire in 
                   close successsion and we miss the intermediate value 
                   of frontend_state. */
                if (dev->state == XenbusStateConnected)
                        break;

                err = connect_ring(be);
                if (err)
                        break;
                tap_update_blkif_status(be->blkif);
                break;

        case XenbusStateClosing:
                if (be->blkif->xenblkd) {
                        kthread_stop(be->blkif->xenblkd);
                        be->blkif->xenblkd = NULL;
                }
                xenbus_switch_state(dev, XenbusStateClosing);
                break;

        case XenbusStateClosed:
                xenbus_switch_state(dev, XenbusStateClosed);
                if (xenbus_dev_is_online(dev))
                        break;
                /* fall through if not online */
        case XenbusStateUnknown:
                device_unregister(&dev->dev);
                break;

        default:
                xenbus_dev_fatal(dev, -EINVAL, "saw state %d at frontend",
                                 frontend_state);
                break;
        }
}


/**
 * Switch to Connected state.
 */
static void connect(struct backend_info *be)
{
        int err;

        struct xenbus_device *dev = be->dev;

        err = xenbus_switch_state(dev, XenbusStateConnected);
        if (err)
                xenbus_dev_fatal(dev, err, "switching to Connected state",
                                 dev->nodename);

        return;
}


static int connect_ring(struct backend_info *be)
{
        struct xenbus_device *dev = be->dev;
        unsigned long ring_ref;
        unsigned int evtchn;
        char protocol[64];
        int err;

        DPRINTK("%s\n", dev->otherend);

        err = xenbus_gather(XBT_NIL, dev->otherend, "ring-ref", "%lu", 
                            &ring_ref, "event-channel", "%u", &evtchn, NULL);
        if (err) {
                xenbus_dev_fatal(dev, err,
                                 "reading %s/ring-ref and event-channel",
                                 dev->otherend);
                return err;
        }

        be->blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
        err = xenbus_gather(XBT_NIL, dev->otherend, "protocol",
                            "%63s", protocol, NULL);
        if (err)
                strcpy(protocol, "unspecified, assuming native");
        else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_NATIVE))
                be->blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
        else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_32))
                be->blkif->blk_protocol = BLKIF_PROTOCOL_X86_32;
        else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_64))
                be->blkif->blk_protocol = BLKIF_PROTOCOL_X86_64;
        else {
                xenbus_dev_fatal(dev, err, "unknown fe protocol %s", protocol);
                return -1;
        }
        printk(KERN_INFO
               "blktap: ring-ref %ld, event-channel %d, protocol %d (%s)\n",
               ring_ref, evtchn, be->blkif->blk_protocol, protocol);

        /* Map the shared frame, irq etc. */
        err = tap_blkif_map(be->blkif, ring_ref, evtchn);
        if (err) {
                xenbus_dev_fatal(dev, err, "mapping ring-ref %lu port %u",
                                 ring_ref, evtchn);
                return err;
        } 

        return 0;
}


/* ** Driver Registration ** */


static struct xenbus_device_id blktap_ids[] = {
        { "tap" },
        { "" }
};


static struct xenbus_driver blktap = {
        .name = "tap",
        .owner = THIS_MODULE,
        .ids = blktap_ids,
        .probe = blktap_probe,
        .remove = blktap_remove,
        .otherend_changed = tap_frontend_changed
};


void tap_blkif_xenbus_init(void)
{
        xenbus_register_backend(&blktap);
}