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 struct backend_info {
  25         struct xenbus_device    *dev;
  26         struct xen_blkif        *blkif;
  27         struct xenbus_watch     backend_watch;
  28         unsigned                major;
  29         unsigned                minor;
  30         char                    *mode;
  31 };
  32
  33 static struct kmem_cache *xen_blkif_cachep;
  34 static void connect(struct backend_info *);
  35 static int connect_ring(struct backend_info *);
  36 static void backend_changed(struct xenbus_watch *, const char **,
  37                             unsigned int);
  38
  39 struct xenbus_device *xen_blkbk_xenbus(struct backend_info *be)
  40 {
  41         return be->dev;
  42 }
  43
  44 static int blkback_name(struct xen_blkif *blkif, char *buf)
  45 {
  46         char *devpath, *devname;
  47         struct xenbus_device *dev = blkif->be->dev;
  48
  49         devpath = xenbus_read(XBT_NIL, dev->nodename, "dev", NULL);
  50         if (IS_ERR(devpath))
  51                 return PTR_ERR(devpath);
  52
  53         devname = strstr(devpath, "/dev/");
  54         if (devname != NULL)
  55                 devname += strlen("/dev/");
  56         else
  57                 devname  = devpath;
  58
  59         snprintf(buf, TASK_COMM_LEN, "blkback.%d.%s", blkif->domid, devname);
  60         kfree(devpath);
  61
  62         return 0;
  63 }
  64
  65 static void xen_update_blkif_status(struct xen_blkif *blkif)
  66 {
  67         int err;
  68         char name[TASK_COMM_LEN];
  69
  70         /* Not ready to connect? */
  71         if (!blkif->irq || !blkif->vbd.bdev)
  72                 return;
  73
  74         /* Already connected? */
  75         if (blkif->be->dev->state == XenbusStateConnected)
  76                 return;
  77
  78         /* Attempt to connect: exit if we fail to. */
  79         connect(blkif->be);
  80         if (blkif->be->dev->state != XenbusStateConnected)
  81                 return;
  82
  83         err = blkback_name(blkif, name);
  84         if (err) {
  85                 xenbus_dev_error(blkif->be->dev, err, "get blkback dev name");
  86                 return;
  87         }
  88
  89         err = filemap_write_and_wait(blkif->vbd.bdev->bd_inode->i_mapping);
  90         if (err) {
  91                 xenbus_dev_error(blkif->be->dev, err, "block flush");
  92                 return;
  93         }
  94         invalidate_inode_pages2(blkif->vbd.bdev->bd_inode->i_mapping);
  95
  96         blkif->xenblkd = kthread_run(xen_blkif_schedule, blkif, name);
  97         if (IS_ERR(blkif->xenblkd)) {
  98                 err = PTR_ERR(blkif->xenblkd);
  99                 blkif->xenblkd = NULL;
 100                 xenbus_dev_error(blkif->be->dev, err, "start xenblkd");
 101         }
 102 }
 103
 104 static struct xen_blkif *xen_blkif_alloc(domid_t domid)
 105 {
 106         struct xen_blkif *blkif;
 107
 108         blkif = kmem_cache_alloc(xen_blkif_cachep, GFP_KERNEL);
 109         if (!blkif)
 110                 return ERR_PTR(-ENOMEM);
 111
 112         memset(blkif, 0, sizeof(*blkif));
 113         blkif->domid = domid;
 114         spin_lock_init(&blkif->blk_ring_lock);
 115         atomic_set(&blkif->refcnt, 1);
 116         init_waitqueue_head(&blkif->wq);
 117         blkif->st_print = jiffies;
 118         init_waitqueue_head(&blkif->waiting_to_free);
 119
 120         return blkif;
 121 }
 122
 123 static int map_frontend_page(struct xen_blkif *blkif, unsigned long shared_page)
 124 {
 125         struct gnttab_map_grant_ref op;
 126
 127         gnttab_set_map_op(&op, (unsigned long)blkif->blk_ring_area->addr,
 128                           GNTMAP_host_map, shared_page, blkif->domid);
 129
 130         if (HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, &op, 1))
 131                 BUG();
 132
 133         if (op.status) {
 134                 DPRINTK("Grant table operation failure !\n");
 135                 return op.status;
 136         }
 137
 138         blkif->shmem_ref = shared_page;
 139         blkif->shmem_handle = op.handle;
 140
 141         return 0;
 142 }
 143
 144 static void unmap_frontend_page(struct xen_blkif *blkif)
 145 {
 146         struct gnttab_unmap_grant_ref op;
 147
 148         gnttab_set_unmap_op(&op, (unsigned long)blkif->blk_ring_area->addr,
 149                             GNTMAP_host_map, blkif->shmem_handle);
 150
 151         if (HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, &op, 1))
 152                 BUG();
 153 }
 154
 155 static int xen_blkif_map(struct xen_blkif *blkif, unsigned long shared_page,
 156                          unsigned int evtchn)
 157 {
 158         int err;
 159
 160         /* Already connected through? */
 161         if (blkif->irq)
 162                 return 0;
 163
 164         blkif->blk_ring_area = alloc_vm_area(PAGE_SIZE);
 165         if (!blkif->blk_ring_area)
 166                 return -ENOMEM;
 167
 168         err = map_frontend_page(blkif, shared_page);
 169         if (err) {
 170                 free_vm_area(blkif->blk_ring_area);
 171                 return err;
 172         }
 173
 174         switch (blkif->blk_protocol) {
 175         case BLKIF_PROTOCOL_NATIVE:
 176         {
 177                 struct blkif_sring *sring;
 178                 sring = (struct blkif_sring *)blkif->blk_ring_area->addr;
 179                 BACK_RING_INIT(&blkif->blk_rings.native, sring, PAGE_SIZE);
 180                 break;
 181         }
 182         case BLKIF_PROTOCOL_X86_32:
 183         {
 184                 struct blkif_x86_32_sring *sring_x86_32;
 185                 sring_x86_32 = (struct blkif_x86_32_sring *)blkif->blk_ring_area->addr;
 186                 BACK_RING_INIT(&blkif->blk_rings.x86_32, sring_x86_32, PAGE_SIZE);
 187                 break;
 188         }
 189         case BLKIF_PROTOCOL_X86_64:
 190         {
 191                 struct blkif_x86_64_sring *sring_x86_64;
 192                 sring_x86_64 = (struct blkif_x86_64_sring *)blkif->blk_ring_area->addr;
 193                 BACK_RING_INIT(&blkif->blk_rings.x86_64, sring_x86_64, PAGE_SIZE);
 194                 break;
 195         }
 196         default:
 197                 BUG();
 198         }
 199
 200         err = bind_interdomain_evtchn_to_irqhandler(blkif->domid, evtchn,
 201                                                     xen_blkif_be_int, 0,
 202                                                     "blkif-backend", blkif);
 203         if (err < 0) {
 204                 unmap_frontend_page(blkif);
 205                 free_vm_area(blkif->blk_ring_area);
 206                 blkif->blk_rings.common.sring = NULL;
 207                 return err;
 208         }
 209         blkif->irq = err;
 210
 211         return 0;
 212 }
 213
 214 static void xen_blkif_disconnect(struct xen_blkif *blkif)
 215 {
 216         if (blkif->xenblkd) {
 217                 kthread_stop(blkif->xenblkd);
 218                 blkif->xenblkd = NULL;
 219         }
 220
 221         atomic_dec(&blkif->refcnt);
 222         wait_event(blkif->waiting_to_free, atomic_read(&blkif->refcnt) == 0);
 223         atomic_inc(&blkif->refcnt);
 224
 225         if (blkif->irq) {
 226                 unbind_from_irqhandler(blkif->irq, blkif);
 227                 blkif->irq = 0;
 228         }
 229
 230         if (blkif->blk_rings.common.sring) {
 231                 unmap_frontend_page(blkif);
 232                 free_vm_area(blkif->blk_ring_area);
 233                 blkif->blk_rings.common.sring = NULL;
 234         }
 235 }
 236
 237 void xen_blkif_free(struct xen_blkif *blkif)
 238 {
 239         if (!atomic_dec_and_test(&blkif->refcnt))
 240                 BUG();
 241         kmem_cache_free(xen_blkif_cachep, blkif);
 242 }
 243
 244 int __init xen_blkif_interface_init(void)
 245 {
 246         xen_blkif_cachep = kmem_cache_create("blkif_cache",
 247                                              sizeof(struct xen_blkif),
 248                                              0, 0, NULL);
 249         if (!xen_blkif_cachep)
 250                 return -ENOMEM;
 251
 252         return 0;
 253 }
 254
 255 /*
 256  *  sysfs interface for VBD I/O requests
 257  */
 258
 259 #define VBD_SHOW(name, format, args...)                                 \
 260         static ssize_t show_##name(struct device *_dev,                 \
 261                                    struct device_attribute *attr,       \
 262                                    char *buf)                           \
 263         {                                                               \
 264                 struct xenbus_device *dev = to_xenbus_device(_dev);     \
 265                 struct backend_info *be = dev_get_drvdata(&dev->dev);   \
 266                                                                         \
 267                 return sprintf(buf, format, ##args);                    \
 268         }                                                               \
 269         static DEVICE_ATTR(name, S_IRUGO, show_##name, NULL)
 270
 271 VBD_SHOW(oo_req,  "%d\n", be->blkif->st_oo_req);
 272 VBD_SHOW(rd_req,  "%d\n", be->blkif->st_rd_req);
 273 VBD_SHOW(wr_req,  "%d\n", be->blkif->st_wr_req);
 274 VBD_SHOW(f_req,  "%d\n", be->blkif->st_f_req);
 275 VBD_SHOW(rd_sect, "%d\n", be->blkif->st_rd_sect);
 276 VBD_SHOW(wr_sect, "%d\n", be->blkif->st_wr_sect);
 277
 278 static struct attribute *xen_vbdstat_attrs[] = {
 279         &dev_attr_oo_req.attr,
 280         &dev_attr_rd_req.attr,
 281         &dev_attr_wr_req.attr,
 282         &dev_attr_f_req.attr,
 283         &dev_attr_rd_sect.attr,
 284         &dev_attr_wr_sect.attr,
 285         NULL
 286 };
 287
 288 static struct attribute_group xen_vbdstat_group = {
 289         .name = "statistics",
 290         .attrs = xen_vbdstat_attrs,
 291 };
 292
 293 VBD_SHOW(physical_device, "%x:%x\n", be->major, be->minor);
 294 VBD_SHOW(mode, "%s\n", be->mode);
 295
 296 int xenvbd_sysfs_addif(struct xenbus_device *dev)
 297 {
 298         int error;
 299
 300         error = device_create_file(&dev->dev, &dev_attr_physical_device);
 301         if (error)
 302                 goto fail1;
 303
 304         error = device_create_file(&dev->dev, &dev_attr_mode);
 305         if (error)
 306                 goto fail2;
 307
 308         error = sysfs_create_group(&dev->dev.kobj, &xen_vbdstat_group);
 309         if (error)
 310                 goto fail3;
 311
 312         return 0;
 313
 314 fail3:  sysfs_remove_group(&dev->dev.kobj, &xen_vbdstat_group);
 315 fail2:  device_remove_file(&dev->dev, &dev_attr_mode);
 316 fail1:  device_remove_file(&dev->dev, &dev_attr_physical_device);
 317         return error;
 318 }
 319
 320 void xenvbd_sysfs_delif(struct xenbus_device *dev)
 321 {
 322         sysfs_remove_group(&dev->dev.kobj, &xen_vbdstat_group);
 323         device_remove_file(&dev->dev, &dev_attr_mode);
 324         device_remove_file(&dev->dev, &dev_attr_physical_device);
 325 }
 326
 327
 328 static void xen_vbd_free(struct xen_vbd *vbd)
 329 {
 330         if (vbd->bdev)
 331                 blkdev_put(vbd->bdev, vbd->readonly ? FMODE_READ : FMODE_WRITE);
 332         vbd->bdev = NULL;
 333 }
 334
 335 static int xen_vbd_create(struct xen_blkif *blkif, blkif_vdev_t handle,
 336                           unsigned major, unsigned minor, int readonly,
 337                           int cdrom)
 338 {
 339         struct xen_vbd *vbd;
 340         struct block_device *bdev;
 341         struct request_queue *q;
 342
 343         vbd = &blkif->vbd;
 344         vbd->handle   = handle;
 345         vbd->readonly = readonly;
 346         vbd->type     = 0;
 347
 348         vbd->pdevice  = MKDEV(major, minor);
 349
 350         bdev = blkdev_get_by_dev(vbd->pdevice, vbd->readonly ?
 351                                  FMODE_READ : FMODE_WRITE, NULL);
 352
 353         if (IS_ERR(bdev)) {
 354                 DPRINTK("xen_vbd_create: device %08x could not be opened.\n",
 355                         vbd->pdevice);
 356                 return -ENOENT;
 357         }
 358
 359         vbd->bdev = bdev;
 360         vbd->size = vbd_sz(vbd);
 361
 362         if (vbd->bdev->bd_disk == NULL) {
 363                 DPRINTK("xen_vbd_create: device %08x doesn't exist.\n",
 364                         vbd->pdevice);
 365                 xen_vbd_free(vbd);
 366                 return -ENOENT;
 367         }
 368
 369         if (vbd->bdev->bd_disk->flags & GENHD_FL_CD || cdrom)
 370                 vbd->type |= VDISK_CDROM;
 371         if (vbd->bdev->bd_disk->flags & GENHD_FL_REMOVABLE)
 372                 vbd->type |= VDISK_REMOVABLE;
 373
 374         q = bdev_get_queue(bdev);
 375         if (q && q->flush_flags)
 376                 vbd->flush_support = true;
 377
 378         DPRINTK("Successful creation of handle=%04x (dom=%u)\n",
 379                 handle, blkif->domid);
 380         return 0;
 381 }
 382 static int xen_blkbk_remove(struct xenbus_device *dev)
 383 {
 384         struct backend_info *be = dev_get_drvdata(&dev->dev);
 385
 386         DPRINTK("");
 387
 388         if (be->major || be->minor)
 389                 xenvbd_sysfs_delif(dev);
 390
 391         if (be->backend_watch.node) {
 392                 unregister_xenbus_watch(&be->backend_watch);
 393                 kfree(be->backend_watch.node);
 394                 be->backend_watch.node = NULL;
 395         }
 396
 397         if (be->blkif) {
 398                 xen_blkif_disconnect(be->blkif);
 399                 xen_vbd_free(&be->blkif->vbd);
 400                 xen_blkif_free(be->blkif);
 401                 be->blkif = NULL;
 402         }
 403
 404         kfree(be);
 405         dev_set_drvdata(&dev->dev, NULL);
 406         return 0;
 407 }
 408
 409 int xen_blkbk_flush_diskcache(struct xenbus_transaction xbt,
 410                               struct backend_info *be, int state)
 411 {
 412         struct xenbus_device *dev = be->dev;
 413         int err;
 414
 415         err = xenbus_printf(xbt, dev->nodename, "feature-flush-cache",
 416                             "%d", state);
 417         if (err)
 418                 xenbus_dev_fatal(dev, err, "writing feature-flush-cache");
 419
 420         return err;
 421 }
 422
 423 /*
 424  * Entry point to this code when a new device is created.  Allocate the basic
 425  * structures, and watch the store waiting for the hotplug scripts to tell us
 426  * the device's physical major and minor numbers.  Switch to InitWait.
 427  */
 428 static int xen_blkbk_probe(struct xenbus_device *dev,
 429                            const struct xenbus_device_id *id)
 430 {
 431         int err;
 432         struct backend_info *be = kzalloc(sizeof(struct backend_info),
 433                                           GFP_KERNEL);
 434         if (!be) {
 435                 xenbus_dev_fatal(dev, -ENOMEM,
 436                                  "allocating backend structure");
 437                 return -ENOMEM;
 438         }
 439         be->dev = dev;
 440         dev_set_drvdata(&dev->dev, be);
 441
 442         be->blkif = xen_blkif_alloc(dev->otherend_id);
 443         if (IS_ERR(be->blkif)) {
 444                 err = PTR_ERR(be->blkif);
 445                 be->blkif = NULL;
 446                 xenbus_dev_fatal(dev, err, "creating block interface");
 447                 goto fail;
 448         }
 449
 450         /* setup back pointer */
 451         be->blkif->be = be;
 452
 453         err = xenbus_watch_pathfmt(dev, &be->backend_watch, backend_changed,
 454                                    "%s/%s", dev->nodename, "physical-device");
 455         if (err)
 456                 goto fail;
 457
 458         err = xenbus_switch_state(dev, XenbusStateInitWait);
 459         if (err)
 460                 goto fail;
 461
 462         return 0;
 463
 464 fail:
 465         DPRINTK("failed");
 466         xen_blkbk_remove(dev);
 467         return err;
 468 }
 469
 470
 471 /*
 472  * Callback received when the hotplug scripts have placed the physical-device
 473  * node.  Read it and the mode node, and create a vbd.  If the frontend is
 474  * ready, connect.
 475  */
 476 static void backend_changed(struct xenbus_watch *watch,
 477                             const char **vec, unsigned int len)
 478 {
 479         int err;
 480         unsigned major;
 481         unsigned minor;
 482         struct backend_info *be
 483                 = container_of(watch, struct backend_info, backend_watch);
 484         struct xenbus_device *dev = be->dev;
 485         int cdrom = 0;
 486         char *device_type;
 487
 488         DPRINTK("");
 489
 490         err = xenbus_scanf(XBT_NIL, dev->nodename, "physical-device", "%x:%x",
 491                            &major, &minor);
 492         if (XENBUS_EXIST_ERR(err)) {
 493                 /*
 494                  * Since this watch will fire once immediately after it is
 495                  * registered, we expect this.  Ignore it, and wait for the
 496                  * hotplug scripts.
 497                  */
 498                 return;
 499         }
 500         if (err != 2) {
 501                 xenbus_dev_fatal(dev, err, "reading physical-device");
 502                 return;
 503         }
 504
 505         if ((be->major || be->minor) &&
 506             ((be->major != major) || (be->minor != minor))) {
 507                 pr_warn(DRV_PFX "changing physical device (from %x:%x to %x:%x) not supported.\n",
 508                         be->major, be->minor, major, minor);
 509                 return;
 510         }
 511
 512         be->mode = xenbus_read(XBT_NIL, dev->nodename, "mode", NULL);
 513         if (IS_ERR(be->mode)) {
 514                 err = PTR_ERR(be->mode);
 515                 be->mode = NULL;
 516                 xenbus_dev_fatal(dev, err, "reading mode");
 517                 return;
 518         }
 519
 520         device_type = xenbus_read(XBT_NIL, dev->otherend, "device-type", NULL);
 521         if (!IS_ERR(device_type)) {
 522                 cdrom = strcmp(device_type, "cdrom") == 0;
 523                 kfree(device_type);
 524         }
 525
 526         if (be->major == 0 && be->minor == 0) {
 527                 /* Front end dir is a number, which is used as the handle. */
 528
 529                 char *p = strrchr(dev->otherend, '/') + 1;
 530                 long handle;
 531                 err = strict_strtoul(p, 0, &handle);
 532                 if (err)
 533                         return;
 534
 535                 be->major = major;
 536                 be->minor = minor;
 537
 538                 err = xen_vbd_create(be->blkif, handle, major, minor,
 539                                  (NULL == strchr(be->mode, 'w')), cdrom);
 540                 if (err) {
 541                         be->major = 0;
 542                         be->minor = 0;
 543                         xenbus_dev_fatal(dev, err, "creating vbd structure");
 544                         return;
 545                 }
 546
 547                 err = xenvbd_sysfs_addif(dev);
 548                 if (err) {
 549                         xen_vbd_free(&be->blkif->vbd);
 550                         be->major = 0;
 551                         be->minor = 0;
 552                         xenbus_dev_fatal(dev, err, "creating sysfs entries");
 553                         return;
 554                 }
 555
 556                 /* We're potentially connected now */
 557                 xen_update_blkif_status(be->blkif);
 558         }
 559 }
 560
 561
 562 /*
 563  * Callback received when the frontend's state changes.
 564  */
 565 static void frontend_changed(struct xenbus_device *dev,
 566                              enum xenbus_state frontend_state)
 567 {
 568         struct backend_info *be = dev_get_drvdata(&dev->dev);
 569         int err;
 570
 571         DPRINTK("%s", xenbus_strstate(frontend_state));
 572
 573         switch (frontend_state) {
 574         case XenbusStateInitialising:
 575                 if (dev->state == XenbusStateClosed) {
 576                         pr_info(DRV_PFX "%s: prepare for reconnect\n",
 577                                 dev->nodename);
 578                         xenbus_switch_state(dev, XenbusStateInitWait);
 579                 }
 580                 break;
 581
 582         case XenbusStateInitialised:
 583         case XenbusStateConnected:
 584                 /*
 585                  * Ensure we connect even when two watches fire in
 586                  * close successsion and we miss the intermediate value
 587                  * of frontend_state.
 588                  */
 589                 if (dev->state == XenbusStateConnected)
 590                         break;
 591
 592                 /*
 593                  * Enforce precondition before potential leak point.
 594                  * blkif_disconnect() is idempotent.
 595                  */
 596                 xen_blkif_disconnect(be->blkif);
 597
 598                 err = connect_ring(be);
 599                 if (err)
 600                         break;
 601                 xen_update_blkif_status(be->blkif);
 602                 break;
 603
 604         case XenbusStateClosing:
 605                 xen_blkif_disconnect(be->blkif);
 606                 xenbus_switch_state(dev, XenbusStateClosing);
 607                 break;
 608
 609         case XenbusStateClosed:
 610                 xenbus_switch_state(dev, XenbusStateClosed);
 611                 if (xenbus_dev_is_online(dev))
 612                         break;
 613                 /* fall through if not online */
 614         case XenbusStateUnknown:
 615                 /* implies blkif_disconnect() via blkback_remove() */
 616                 device_unregister(&dev->dev);
 617                 break;
 618
 619         default:
 620                 xenbus_dev_fatal(dev, -EINVAL, "saw state %d at frontend",
 621                                  frontend_state);
 622                 break;
 623         }
 624 }
 625
 626
 627 /* ** Connection ** */
 628
 629
 630 /*
 631  * Write the physical details regarding the block device to the store, and
 632  * switch to Connected state.
 633  */
 634 static void connect(struct backend_info *be)
 635 {
 636         struct xenbus_transaction xbt;
 637         int err;
 638         struct xenbus_device *dev = be->dev;
 639
 640         DPRINTK("%s", dev->otherend);
 641
 642         /* Supply the information about the device the frontend needs */
 643 again:
 644         err = xenbus_transaction_start(&xbt);
 645         if (err) {
 646                 xenbus_dev_fatal(dev, err, "starting transaction");
 647                 return;
 648         }
 649
 650         err = xen_blkbk_flush_diskcache(xbt, be, be->blkif->vbd.flush_support);
 651         if (err)
 652                 goto abort;
 653
 654         err = xenbus_printf(xbt, dev->nodename, "sectors", "%llu",
 655                             (unsigned long long)vbd_sz(&be->blkif->vbd));
 656         if (err) {
 657                 xenbus_dev_fatal(dev, err, "writing %s/sectors",
 658                                  dev->nodename);
 659                 goto abort;
 660         }
 661
 662         /* FIXME: use a typename instead */
 663         err = xenbus_printf(xbt, dev->nodename, "info", "%u",
 664                             be->blkif->vbd.type |
 665                             (be->blkif->vbd.readonly ? VDISK_READONLY : 0));
 666         if (err) {
 667                 xenbus_dev_fatal(dev, err, "writing %s/info",
 668                                  dev->nodename);
 669                 goto abort;
 670         }
 671         err = xenbus_printf(xbt, dev->nodename, "sector-size", "%lu",
 672                             (unsigned long)
 673                             bdev_logical_block_size(be->blkif->vbd.bdev));
 674         if (err) {
 675                 xenbus_dev_fatal(dev, err, "writing %s/sector-size",
 676                                  dev->nodename);
 677                 goto abort;
 678         }
 679
 680         err = xenbus_transaction_end(xbt, 0);
 681         if (err == -EAGAIN)
 682                 goto again;
 683         if (err)
 684                 xenbus_dev_fatal(dev, err, "ending transaction");
 685
 686         err = xenbus_switch_state(dev, XenbusStateConnected);
 687         if (err)
 688                 xenbus_dev_fatal(dev, err, "switching to Connected state",
 689                                  dev->nodename);
 690
 691         return;
 692  abort:
 693         xenbus_transaction_end(xbt, 1);
 694 }
 695
 696
 697 static int connect_ring(struct backend_info *be)
 698 {
 699         struct xenbus_device *dev = be->dev;
 700         unsigned long ring_ref;
 701         unsigned int evtchn;
 702         char protocol[64] = "";
 703         int err;
 704
 705         DPRINTK("%s", dev->otherend);
 706
 707         err = xenbus_gather(XBT_NIL, dev->otherend, "ring-ref", "%lu",
 708                             &ring_ref, "event-channel", "%u", &evtchn, NULL);
 709         if (err) {
 710                 xenbus_dev_fatal(dev, err,
 711                                  "reading %s/ring-ref and event-channel",
 712                                  dev->otherend);
 713                 return err;
 714         }
 715
 716         be->blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
 717         err = xenbus_gather(XBT_NIL, dev->otherend, "protocol",
 718                             "%63s", protocol, NULL);
 719         if (err)
 720                 strcpy(protocol, "unspecified, assuming native");
 721         else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_NATIVE))
 722                 be->blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
 723         else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_32))
 724                 be->blkif->blk_protocol = BLKIF_PROTOCOL_X86_32;
 725         else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_64))
 726                 be->blkif->blk_protocol = BLKIF_PROTOCOL_X86_64;
 727         else {
 728                 xenbus_dev_fatal(dev, err, "unknown fe protocol %s", protocol);
 729                 return -1;
 730         }
 731         pr_info(DRV_PFX "ring-ref %ld, event-channel %d, protocol %d (%s)\n",
 732                 ring_ref, evtchn, be->blkif->blk_protocol, protocol);
 733
 734         /* Map the shared frame, irq etc. */
 735         err = xen_blkif_map(be->blkif, ring_ref, evtchn);
 736         if (err) {
 737                 xenbus_dev_fatal(dev, err, "mapping ring-ref %lu port %u",
 738                                  ring_ref, evtchn);
 739                 return err;
 740         }
 741
 742         return 0;
 743 }
 744
 745
 746 /* ** Driver Registration ** */
 747
 748
 749 static const struct xenbus_device_id xen_blkbk_ids[] = {
 750         { "vbd" },
 751         { "" }
 752 };
 753
 754
 755 static struct xenbus_driver xen_blkbk = {
 756         .name = "vbd",
 757         .owner = THIS_MODULE,
 758         .ids = xen_blkbk_ids,
 759         .probe = xen_blkbk_probe,
 760         .remove = xen_blkbk_remove,
 761         .otherend_changed = frontend_changed
 762 };
 763
 764
 765 int xen_blkif_xenbus_init(void)
 766 {
 767         return xenbus_register_backend(&xen_blkbk);
 768 }