drivers/block/xen-blkback/xenbus.c

   1 /*  Xenbus code for blkif backend
   2     Copyright (C) 2005 Rusty Russell <rusty@rustcorp.com.au>
   3     Copyright (C) 2005 XenSource Ltd
   4
   5     This program is free software; you can redistribute it and/or modify
   6     it under the terms of the GNU General Public License as published by
   7     the Free Software Foundation; either version 2 of the License, or
   8     (at your option) any later version.
   9
  10     This program is distributed in the hope that it will be useful,
  11     but WITHOUT ANY WARRANTY; without even the implied warranty of
  12     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13     GNU General Public License for more details.
  14
  15 */
  16
  17 #include <stdarg.h>
  18 #include <linux/module.h>
  19 #include <linux/kthread.h>
  20 #include <xen/events.h>
  21 #include <xen/grant_table.h>
  22 #include "common.h"
  23
  24 #undef DPRINTK
  25 #define DPRINTK(fmt, args...)                           \
  26         pr_debug("blkback/xenbus (%s:%d) " fmt ".\n",   \
  27                  __func__, __LINE__, ##args)
  28
  29 struct backend_info {
  30         struct xenbus_device *dev;
  31         struct blkif_st *blkif;
  32         struct xenbus_watch backend_watch;
  33         unsigned major;
  34         unsigned minor;
  35         char *mode;
  36 };
  37
  38 static struct kmem_cache *blkif_cachep;
  39 static void connect(struct backend_info *);
  40 static int connect_ring(struct backend_info *);
  41 static void backend_changed(struct xenbus_watch *, const char **,
  42                             unsigned int);
  43
  44 struct xenbus_device *blkback_xenbus(struct backend_info *be)
  45 {
  46         return be->dev;
  47 }
  48
  49 static int blkback_name(struct blkif_st *blkif, char *buf)
  50 {
  51         char *devpath, *devname;
  52         struct xenbus_device *dev = blkif->be->dev;
  53
  54         devpath = xenbus_read(XBT_NIL, dev->nodename, "dev", NULL);
  55         if (IS_ERR(devpath))
  56                 return PTR_ERR(devpath);
  57
  58         devname = strstr(devpath, "/dev/");
  59         if (devname != NULL)
  60                 devname += strlen("/dev/");
  61         else
  62                 devname  = devpath;
  63
  64         snprintf(buf, TASK_COMM_LEN, "blkback.%d.%s", blkif->domid, devname);
  65         kfree(devpath);
  66
  67         return 0;
  68 }
  69
  70 static void update_blkif_status(struct blkif_st *blkif)
  71 {
  72         int err;
  73         char name[TASK_COMM_LEN];
  74
  75         /* Not ready to connect? */
  76         if (!blkif->irq || !blkif->vbd.bdev)
  77                 return;
  78
  79         /* Already connected? */
  80         if (blkif->be->dev->state == XenbusStateConnected)
  81                 return;
  82
  83         /* Attempt to connect: exit if we fail to. */
  84         connect(blkif->be);
  85         if (blkif->be->dev->state != XenbusStateConnected)
  86                 return;
  87
  88         err = blkback_name(blkif, name);
  89         if (err) {
  90                 xenbus_dev_error(blkif->be->dev, err, "get blkback dev name");
  91                 return;
  92         }
  93
  94         err = filemap_write_and_wait(blkif->vbd.bdev->bd_inode->i_mapping);
  95         if (err) {
  96                 xenbus_dev_error(blkif->be->dev, err, "block flush");
  97                 return;
  98         }
  99         invalidate_inode_pages2(blkif->vbd.bdev->bd_inode->i_mapping);
 100
 101         blkif->xenblkd = kthread_run(blkif_schedule, blkif, name);
 102         if (IS_ERR(blkif->xenblkd)) {
 103                 err = PTR_ERR(blkif->xenblkd);
 104                 blkif->xenblkd = NULL;
 105                 xenbus_dev_error(blkif->be->dev, err, "start xenblkd");
 106         }
 107 }
 108
 109 struct blkif_st *blkif_alloc(domid_t domid)
 110 {
 111         struct blkif_st *blkif;
 112
 113         blkif = kmem_cache_alloc(blkif_cachep, GFP_KERNEL);
 114         if (!blkif)
 115                 return ERR_PTR(-ENOMEM);
 116
 117         memset(blkif, 0, sizeof(*blkif));
 118         blkif->domid = domid;
 119         spin_lock_init(&blkif->blk_ring_lock);
 120         atomic_set(&blkif->refcnt, 1);
 121         init_waitqueue_head(&blkif->wq);
 122         blkif->st_print = jiffies;
 123         init_waitqueue_head(&blkif->waiting_to_free);
 124
 125         return blkif;
 126 }
 127
 128 static int map_frontend_page(struct blkif_st *blkif, unsigned long shared_page)
 129 {
 130         struct gnttab_map_grant_ref op;
 131
 132         gnttab_set_map_op(&op, (unsigned long)blkif->blk_ring_area->addr,
 133                           GNTMAP_host_map, shared_page, blkif->domid);
 134
 135         if (HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, &op, 1))
 136                 BUG();
 137
 138         if (op.status) {
 139                 DPRINTK(" Grant table operation failure !\n");
 140                 return op.status;
 141         }
 142
 143         blkif->shmem_ref = shared_page;
 144         blkif->shmem_handle = op.handle;
 145
 146         return 0;
 147 }
 148
 149 static void unmap_frontend_page(struct blkif_st *blkif)
 150 {
 151         struct gnttab_unmap_grant_ref op;
 152
 153         gnttab_set_unmap_op(&op, (unsigned long)blkif->blk_ring_area->addr,
 154                             GNTMAP_host_map, blkif->shmem_handle);
 155
 156         if (HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, &op, 1))
 157                 BUG();
 158 }
 159
 160 int blkif_map(struct blkif_st *blkif, unsigned long shared_page,
 161               unsigned int evtchn)
 162 {
 163         int err;
 164
 165         /* Already connected through? */
 166         if (blkif->irq)
 167                 return 0;
 168
 169         blkif->blk_ring_area = alloc_vm_area(PAGE_SIZE);
 170         if (!blkif->blk_ring_area)
 171                 return -ENOMEM;
 172
 173         err = map_frontend_page(blkif, shared_page);
 174         if (err) {
 175                 free_vm_area(blkif->blk_ring_area);
 176                 return err;
 177         }
 178
 179         switch (blkif->blk_protocol) {
 180         case BLKIF_PROTOCOL_NATIVE:
 181         {
 182                 struct blkif_sring *sring;
 183                 sring = (struct blkif_sring *)blkif->blk_ring_area->addr;
 184                 BACK_RING_INIT(&blkif->blk_rings.native, sring, PAGE_SIZE);
 185                 break;
 186         }
 187         case BLKIF_PROTOCOL_X86_32:
 188         {
 189                 struct blkif_x86_32_sring *sring_x86_32;
 190                 sring_x86_32 = (struct blkif_x86_32_sring *)blkif->blk_ring_area->addr;
 191                 BACK_RING_INIT(&blkif->blk_rings.x86_32, sring_x86_32, PAGE_SIZE);
 192                 break;
 193         }
 194         case BLKIF_PROTOCOL_X86_64:
 195         {
 196                 struct blkif_x86_64_sring *sring_x86_64;
 197                 sring_x86_64 = (struct blkif_x86_64_sring *)blkif->blk_ring_area->addr;
 198                 BACK_RING_INIT(&blkif->blk_rings.x86_64, sring_x86_64, PAGE_SIZE);
 199                 break;
 200         }
 201         default:
 202                 BUG();
 203         }
 204
 205         err = bind_interdomain_evtchn_to_irqhandler(
 206                 blkif->domid, evtchn, blkif_be_int, 0, "blkif-backend", blkif);
 207         if (err < 0) {
 208                 unmap_frontend_page(blkif);
 209                 free_vm_area(blkif->blk_ring_area);
 210                 blkif->blk_rings.common.sring = NULL;
 211                 return err;
 212         }
 213         blkif->irq = err;
 214
 215         return 0;
 216 }
 217
 218 void blkif_disconnect(struct blkif_st *blkif)
 219 {
 220         if (blkif->xenblkd) {
 221                 kthread_stop(blkif->xenblkd);
 222                 blkif->xenblkd = NULL;
 223         }
 224
 225         atomic_dec(&blkif->refcnt);
 226         wait_event(blkif->waiting_to_free, atomic_read(&blkif->refcnt) == 0);
 227         atomic_inc(&blkif->refcnt);
 228
 229         if (blkif->irq) {
 230                 unbind_from_irqhandler(blkif->irq, blkif);
 231                 blkif->irq = 0;
 232         }
 233
 234         if (blkif->blk_rings.common.sring) {
 235                 unmap_frontend_page(blkif);
 236                 free_vm_area(blkif->blk_ring_area);
 237                 blkif->blk_rings.common.sring = NULL;
 238         }
 239 }
 240
 241 void blkif_free(struct blkif_st *blkif)
 242 {
 243         if (!atomic_dec_and_test(&blkif->refcnt))
 244                 BUG();
 245         kmem_cache_free(blkif_cachep, blkif);
 246 }
 247
 248 int __init blkif_interface_init(void)
 249 {
 250         blkif_cachep = kmem_cache_create("blkif_cache", sizeof(struct blkif_st),
 251                                          0, 0, NULL);
 252         if (!blkif_cachep)
 253                 return -ENOMEM;
 254
 255         return 0;
 256 }
 257
 258 /*
 259  *  sysfs interface for VBD I/O requests
 260  */
 261
 262 #define VBD_SHOW(name, format, args...)                                 \
 263         static ssize_t show_##name(struct device *_dev,                 \
 264                                    struct device_attribute *attr,       \
 265                                    char *buf)                           \
 266         {                                                               \
 267                 struct xenbus_device *dev = to_xenbus_device(_dev);     \
 268                 struct backend_info *be = dev_get_drvdata(&dev->dev);   \
 269                                                                         \
 270                 return sprintf(buf, format, ##args);                    \
 271         }                                                               \
 272         static DEVICE_ATTR(name, S_IRUGO, show_##name, NULL)
 273
 274 VBD_SHOW(oo_req,  "%d\n", be->blkif->st_oo_req);
 275 VBD_SHOW(rd_req,  "%d\n", be->blkif->st_rd_req);
 276 VBD_SHOW(wr_req,  "%d\n", be->blkif->st_wr_req);
 277 VBD_SHOW(br_req,  "%d\n", be->blkif->st_br_req);
 278 VBD_SHOW(rd_sect, "%d\n", be->blkif->st_rd_sect);
 279 VBD_SHOW(wr_sect, "%d\n", be->blkif->st_wr_sect);
 280
 281 static struct attribute *vbdstat_attrs[] = {
 282         &dev_attr_oo_req.attr,
 283         &dev_attr_rd_req.attr,
 284         &dev_attr_wr_req.attr,
 285         &dev_attr_br_req.attr,
 286         &dev_attr_rd_sect.attr,
 287         &dev_attr_wr_sect.attr,
 288         NULL
 289 };
 290
 291 static struct attribute_group vbdstat_group = {
 292         .name = "statistics",
 293         .attrs = vbdstat_attrs,
 294 };
 295
 296 VBD_SHOW(physical_device, "%x:%x\n", be->major, be->minor);
 297 VBD_SHOW(mode, "%s\n", be->mode);
 298
 299 int xenvbd_sysfs_addif(struct xenbus_device *dev)
 300 {
 301         int error;
 302
 303         error = device_create_file(&dev->dev, &dev_attr_physical_device);
 304         if (error)
 305                 goto fail1;
 306
 307         error = device_create_file(&dev->dev, &dev_attr_mode);
 308         if (error)
 309                 goto fail2;
 310
 311         error = sysfs_create_group(&dev->dev.kobj, &vbdstat_group);
 312         if (error)
 313                 goto fail3;
 314
 315         return 0;
 316
 317 fail3:  sysfs_remove_group(&dev->dev.kobj, &vbdstat_group);
 318 fail2:  device_remove_file(&dev->dev, &dev_attr_mode);
 319 fail1:  device_remove_file(&dev->dev, &dev_attr_physical_device);
 320         return error;
 321 }
 322
 323 void xenvbd_sysfs_delif(struct xenbus_device *dev)
 324 {
 325         sysfs_remove_group(&dev->dev.kobj, &vbdstat_group);
 326         device_remove_file(&dev->dev, &dev_attr_mode);
 327         device_remove_file(&dev->dev, &dev_attr_physical_device);
 328 }
 329
 330
 331 static void vbd_free(struct vbd *vbd)
 332 {
 333         if (vbd->bdev)
 334                 blkdev_put(vbd->bdev, vbd->readonly ? FMODE_READ : FMODE_WRITE);
 335         vbd->bdev = NULL;
 336 }
 337
 338 static int vbd_create(struct blkif_st *blkif, blkif_vdev_t handle,
 339                       unsigned major, unsigned minor, int readonly,
 340                       int cdrom)
 341 {
 342         struct vbd *vbd;
 343         struct block_device *bdev;
 344
 345         vbd = &blkif->vbd;
 346         vbd->handle   = handle;
 347         vbd->readonly = readonly;
 348         vbd->type     = 0;
 349
 350         vbd->pdevice  = MKDEV(major, minor);
 351
 352         bdev = blkdev_get_by_dev(vbd->pdevice, vbd->readonly ?
 353                                  FMODE_READ : FMODE_WRITE, NULL);
 354
 355         if (IS_ERR(bdev)) {
 356                 DPRINTK("vbd_creat: device %08x could not be opened.\n",
 357                         vbd->pdevice);
 358                 return -ENOENT;
 359         }
 360
 361         vbd->bdev = bdev;
 362         vbd->size = vbd_sz(vbd);
 363
 364         if (vbd->bdev->bd_disk == NULL) {
 365                 DPRINTK("vbd_creat: device %08x doesn't exist.\n",
 366                         vbd->pdevice);
 367                 vbd_free(vbd);
 368                 return -ENOENT;
 369         }
 370
 371         if (vbd->bdev->bd_disk->flags & GENHD_FL_CD || cdrom)
 372                 vbd->type |= VDISK_CDROM;
 373         if (vbd->bdev->bd_disk->flags & GENHD_FL_REMOVABLE)
 374                 vbd->type |= VDISK_REMOVABLE;
 375
 376         DPRINTK("Successful creation of handle=%04x (dom=%u)\n",
 377                 handle, blkif->domid);
 378         return 0;
 379 }
 380 static int blkback_remove(struct xenbus_device *dev)
 381 {
 382         struct backend_info *be = dev_get_drvdata(&dev->dev);
 383
 384         DPRINTK("");
 385
 386         if (be->major || be->minor)
 387                 xenvbd_sysfs_delif(dev);
 388
 389         if (be->backend_watch.node) {
 390                 unregister_xenbus_watch(&be->backend_watch);
 391                 kfree(be->backend_watch.node);
 392                 be->backend_watch.node = NULL;
 393         }
 394
 395         if (be->blkif) {
 396                 blkif_disconnect(be->blkif);
 397                 vbd_free(&be->blkif->vbd);
 398                 blkif_free(be->blkif);
 399                 be->blkif = NULL;
 400         }
 401
 402         kfree(be);
 403         dev_set_drvdata(&dev->dev, NULL);
 404         return 0;
 405 }
 406
 407 int blkback_barrier(struct xenbus_transaction xbt,
 408                     struct backend_info *be, int state)
 409 {
 410         struct xenbus_device *dev = be->dev;
 411         int err;
 412
 413         err = xenbus_printf(xbt, dev->nodename, "feature-barrier",
 414                             "%d", state);
 415         if (err)
 416                 xenbus_dev_fatal(dev, err, "writing feature-barrier");
 417
 418         return err;
 419 }
 420
 421 /**
 422  * Entry point to this code when a new device is created.  Allocate the basic
 423  * structures, and watch the store waiting for the hotplug scripts to tell us
 424  * the device's physical major and minor numbers.  Switch to InitWait.
 425  */
 426 static int blkback_probe(struct xenbus_device *dev,
 427                          const struct xenbus_device_id *id)
 428 {
 429         int err;
 430         struct backend_info *be = kzalloc(sizeof(struct backend_info),
 431                                           GFP_KERNEL);
 432         if (!be) {
 433                 xenbus_dev_fatal(dev, -ENOMEM,
 434                                  "allocating backend structure");
 435                 return -ENOMEM;
 436         }
 437         be->dev = dev;
 438         dev_set_drvdata(&dev->dev, be);
 439
 440         be->blkif = blkif_alloc(dev->otherend_id);
 441         if (IS_ERR(be->blkif)) {
 442                 err = PTR_ERR(be->blkif);
 443                 be->blkif = NULL;
 444                 xenbus_dev_fatal(dev, err, "creating block interface");
 445                 goto fail;
 446         }
 447
 448         /* setup back pointer */
 449         be->blkif->be = be;
 450
 451         err = xenbus_watch_pathfmt(dev, &be->backend_watch, backend_changed,
 452                                    "%s/%s", dev->nodename, "physical-device");
 453         if (err)
 454                 goto fail;
 455
 456         err = xenbus_switch_state(dev, XenbusStateInitWait);
 457         if (err)
 458                 goto fail;
 459
 460         return 0;
 461
 462 fail:
 463         DPRINTK("failed");
 464         blkback_remove(dev);
 465         return err;
 466 }
 467
 468
 469 /**
 470  * Callback received when the hotplug scripts have placed the physical-device
 471  * node.  Read it and the mode node, and create a vbd.  If the frontend is
 472  * ready, connect.
 473  */
 474 static void backend_changed(struct xenbus_watch *watch,
 475                             const char **vec, unsigned int len)
 476 {
 477         int err;
 478         unsigned major;
 479         unsigned minor;
 480         struct backend_info *be
 481                 = container_of(watch, struct backend_info, backend_watch);
 482         struct xenbus_device *dev = be->dev;
 483         int cdrom = 0;
 484         char *device_type;
 485
 486         DPRINTK("");
 487
 488         err = xenbus_scanf(XBT_NIL, dev->nodename, "physical-device", "%x:%x",
 489                            &major, &minor);
 490         if (XENBUS_EXIST_ERR(err)) {
 491                 /* Since this watch will fire once immediately after it is
 492                    registered, we expect this.  Ignore it, and wait for the
 493                    hotplug scripts. */
 494                 return;
 495         }
 496         if (err != 2) {
 497                 xenbus_dev_fatal(dev, err, "reading physical-device");
 498                 return;
 499         }
 500
 501         if ((be->major || be->minor) &&
 502             ((be->major != major) || (be->minor != minor))) {
 503                 printk(KERN_WARNING
 504                        "blkback: changing physical device (from %x:%x to "
 505                        "%x:%x) not supported.\n", be->major, be->minor,
 506                        major, minor);
 507                 return;
 508         }
 509
 510         be->mode = xenbus_read(XBT_NIL, dev->nodename, "mode", NULL);
 511         if (IS_ERR(be->mode)) {
 512                 err = PTR_ERR(be->mode);
 513                 be->mode = NULL;
 514                 xenbus_dev_fatal(dev, err, "reading mode");
 515                 return;
 516         }
 517
 518         device_type = xenbus_read(XBT_NIL, dev->otherend, "device-type", NULL);
 519         if (!IS_ERR(device_type)) {
 520                 cdrom = strcmp(device_type, "cdrom") == 0;
 521                 kfree(device_type);
 522         }
 523
 524         if (be->major == 0 && be->minor == 0) {
 525                 /* Front end dir is a number, which is used as the handle. */
 526
 527                 char *p = strrchr(dev->otherend, '/') + 1;
 528                 long handle;
 529                 err = strict_strtoul(p, 0, &handle);
 530                 if (err)
 531                         return;
 532
 533                 be->major = major;
 534                 be->minor = minor;
 535
 536                 err = vbd_create(be->blkif, handle, major, minor,
 537                                  (NULL == strchr(be->mode, 'w')), cdrom);
 538                 if (err) {
 539                         be->major = be->minor = 0;
 540                         xenbus_dev_fatal(dev, err, "creating vbd structure");
 541                         return;
 542                 }
 543
 544                 err = xenvbd_sysfs_addif(dev);
 545                 if (err) {
 546                         vbd_free(&be->blkif->vbd);
 547                         be->major = be->minor = 0;
 548                         xenbus_dev_fatal(dev, err, "creating sysfs entries");
 549                         return;
 550                 }
 551
 552                 /* We're potentially connected now */
 553                 update_blkif_status(be->blkif);
 554         }
 555 }
 556
 557
 558 /**
 559  * Callback received when the frontend's state changes.
 560  */
 561 static void frontend_changed(struct xenbus_device *dev,
 562                              enum xenbus_state frontend_state)
 563 {
 564         struct backend_info *be = dev_get_drvdata(&dev->dev);
 565         int err;
 566
 567         DPRINTK("%s", xenbus_strstate(frontend_state));
 568
 569         switch (frontend_state) {
 570         case XenbusStateInitialising:
 571                 if (dev->state == XenbusStateClosed) {
 572                         printk(KERN_INFO "%s: %s: prepare for reconnect\n",
 573                                __func__, dev->nodename);
 574                         xenbus_switch_state(dev, XenbusStateInitWait);
 575                 }
 576                 break;
 577
 578         case XenbusStateInitialised:
 579         case XenbusStateConnected:
 580                 /* Ensure we connect even when two watches fire in
 581                    close successsion and we miss the intermediate value
 582                    of frontend_state. */
 583                 if (dev->state == XenbusStateConnected)
 584                         break;
 585
 586                 /* Enforce precondition before potential leak point.
 587                  * blkif_disconnect() is idempotent.
 588                  */
 589                 blkif_disconnect(be->blkif);
 590
 591                 err = connect_ring(be);
 592                 if (err)
 593                         break;
 594                 update_blkif_status(be->blkif);
 595                 break;
 596
 597         case XenbusStateClosing:
 598                 blkif_disconnect(be->blkif);
 599                 xenbus_switch_state(dev, XenbusStateClosing);
 600                 break;
 601
 602         case XenbusStateClosed:
 603                 xenbus_switch_state(dev, XenbusStateClosed);
 604                 if (xenbus_dev_is_online(dev))
 605                         break;
 606                 /* fall through if not online */
 607         case XenbusStateUnknown:
 608                 /* implies blkif_disconnect() via blkback_remove() */
 609                 device_unregister(&dev->dev);
 610                 break;
 611
 612         default:
 613                 xenbus_dev_fatal(dev, -EINVAL, "saw state %d at frontend",
 614                                  frontend_state);
 615                 break;
 616         }
 617 }
 618
 619
 620 /* ** Connection ** */
 621
 622
 623 /**
 624  * Write the physical details regarding the block device to the store, and
 625  * switch to Connected state.
 626  */
 627 static void connect(struct backend_info *be)
 628 {
 629         struct xenbus_transaction xbt;
 630         int err;
 631         struct xenbus_device *dev = be->dev;
 632
 633         DPRINTK("%s", dev->otherend);
 634
 635         /* Supply the information about the device the frontend needs */
 636 again:
 637         err = xenbus_transaction_start(&xbt);
 638         if (err) {
 639                 xenbus_dev_fatal(dev, err, "starting transaction");
 640                 return;
 641         }
 642
 643         err = blkback_barrier(xbt, be, 1);
 644         if (err)
 645                 goto abort;
 646
 647         err = xenbus_printf(xbt, dev->nodename, "sectors", "%llu",
 648                             (unsigned long long)vbd_sz(&be->blkif->vbd));
 649         if (err) {
 650                 xenbus_dev_fatal(dev, err, "writing %s/sectors",
 651                                  dev->nodename);
 652                 goto abort;
 653         }
 654
 655         /* FIXME: use a typename instead */
 656         err = xenbus_printf(xbt, dev->nodename, "info", "%u",
 657                             be->blkif->vbd.type |
 658                             (be->blkif->vbd.readonly ? VDISK_READONLY : 0));
 659         if (err) {
 660                 xenbus_dev_fatal(dev, err, "writing %s/info",
 661                                  dev->nodename);
 662                 goto abort;
 663         }
 664         err = xenbus_printf(xbt, dev->nodename, "sector-size", "%lu",
 665                             (unsigned long)
 666                             bdev_logical_block_size(be->blkif->vbd.bdev));
 667         if (err) {
 668                 xenbus_dev_fatal(dev, err, "writing %s/sector-size",
 669                                  dev->nodename);
 670                 goto abort;
 671         }
 672
 673         err = xenbus_transaction_end(xbt, 0);
 674         if (err == -EAGAIN)
 675                 goto again;
 676         if (err)
 677                 xenbus_dev_fatal(dev, err, "ending transaction");
 678
 679         err = xenbus_switch_state(dev, XenbusStateConnected);
 680         if (err)
 681                 xenbus_dev_fatal(dev, err, "switching to Connected state",
 682                                  dev->nodename);
 683
 684         return;
 685  abort:
 686         xenbus_transaction_end(xbt, 1);
 687 }
 688
 689
 690 static int connect_ring(struct backend_info *be)
 691 {
 692         struct xenbus_device *dev = be->dev;
 693         unsigned long ring_ref;
 694         unsigned int evtchn;
 695         char protocol[64] = "";
 696         int err;
 697
 698         DPRINTK("%s", dev->otherend);
 699
 700         err = xenbus_gather(XBT_NIL, dev->otherend, "ring-ref", "%lu",
 701                             &ring_ref, "event-channel", "%u", &evtchn, NULL);
 702         if (err) {
 703                 xenbus_dev_fatal(dev, err,
 704                                  "reading %s/ring-ref and event-channel",
 705                                  dev->otherend);
 706                 return err;
 707         }
 708
 709         be->blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
 710         err = xenbus_gather(XBT_NIL, dev->otherend, "protocol",
 711                             "%63s", protocol, NULL);
 712         if (err)
 713                 strcpy(protocol, "unspecified, assuming native");
 714         else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_NATIVE))
 715                 be->blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
 716         else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_32))
 717                 be->blkif->blk_protocol = BLKIF_PROTOCOL_X86_32;
 718         else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_64))
 719                 be->blkif->blk_protocol = BLKIF_PROTOCOL_X86_64;
 720         else {
 721                 xenbus_dev_fatal(dev, err, "unknown fe protocol %s", protocol);
 722                 return -1;
 723         }
 724         printk(KERN_INFO
 725                "blkback: ring-ref %ld, event-channel %d, protocol %d (%s)\n",
 726                ring_ref, evtchn, be->blkif->blk_protocol, protocol);
 727
 728         /* Map the shared frame, irq etc. */
 729         err = blkif_map(be->blkif, ring_ref, evtchn);
 730         if (err) {
 731                 xenbus_dev_fatal(dev, err, "mapping ring-ref %lu port %u",
 732                                  ring_ref, evtchn);
 733                 return err;
 734         }
 735
 736         return 0;
 737 }
 738
 739
 740 /* ** Driver Registration ** */
 741
 742
 743 static const struct xenbus_device_id blkback_ids[] = {
 744         { "vbd" },
 745         { "" }
 746 };
 747
 748
 749 static struct xenbus_driver blkback = {
 750         .name = "vbd",
 751         .owner = THIS_MODULE,
 752         .ids = blkback_ids,
 753         .probe = blkback_probe,
 754         .remove = blkback_remove,
 755         .otherend_changed = frontend_changed
 756 };
 757
 758
 759 int blkif_xenbus_init(void)
 760 {
 761         return xenbus_register_backend(&blkback);
 762 }