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 *xen_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 *xen_blkbk_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 xen_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(xen_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 static struct blkif_st *xen_blkif_alloc(domid_t domid)
 110 {
 111         struct blkif_st *blkif;
 112
 113         blkif = kmem_cache_alloc(xen_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 static int xen_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(blkif->domid, evtchn,
 206                                                     xen_blkif_be_int, 0,
 207                                                     "blkif-backend", blkif);
 208         if (err < 0) {
 209                 unmap_frontend_page(blkif);
 210                 free_vm_area(blkif->blk_ring_area);
 211                 blkif->blk_rings.common.sring = NULL;
 212                 return err;
 213         }
 214         blkif->irq = err;
 215
 216         return 0;
 217 }
 218
 219 static void xen_blkif_disconnect(struct blkif_st *blkif)
 220 {
 221         if (blkif->xenblkd) {
 222                 kthread_stop(blkif->xenblkd);
 223                 blkif->xenblkd = NULL;
 224         }
 225
 226         atomic_dec(&blkif->refcnt);
 227         wait_event(blkif->waiting_to_free, atomic_read(&blkif->refcnt) == 0);
 228         atomic_inc(&blkif->refcnt);
 229
 230         if (blkif->irq) {
 231                 unbind_from_irqhandler(blkif->irq, blkif);
 232                 blkif->irq = 0;
 233         }
 234
 235         if (blkif->blk_rings.common.sring) {
 236                 unmap_frontend_page(blkif);
 237                 free_vm_area(blkif->blk_ring_area);
 238                 blkif->blk_rings.common.sring = NULL;
 239         }
 240 }
 241
 242 void xen_blkif_free(struct blkif_st *blkif)
 243 {
 244         if (!atomic_dec_and_test(&blkif->refcnt))
 245                 BUG();
 246         kmem_cache_free(xen_blkif_cachep, blkif);
 247 }
 248
 249 int __init xen_blkif_interface_init(void)
 250 {
 251         xen_blkif_cachep = kmem_cache_create("blkif_cache",
 252                                              sizeof(struct blkif_st),
 253                                              0, 0, NULL);
 254         if (!xen_blkif_cachep)
 255                 return -ENOMEM;
 256
 257         return 0;
 258 }
 259
 260 /*
 261  *  sysfs interface for VBD I/O requests
 262  */
 263
 264 #define VBD_SHOW(name, format, args...)                                 \
 265         static ssize_t show_##name(struct device *_dev,                 \
 266                                    struct device_attribute *attr,       \
 267                                    char *buf)                           \
 268         {                                                               \
 269                 struct xenbus_device *dev = to_xenbus_device(_dev);     \
 270                 struct backend_info *be = dev_get_drvdata(&dev->dev);   \
 271                                                                         \
 272                 return sprintf(buf, format, ##args);                    \
 273         }                                                               \
 274         static DEVICE_ATTR(name, S_IRUGO, show_##name, NULL)
 275
 276 VBD_SHOW(oo_req,  "%d\n", be->blkif->st_oo_req);
 277 VBD_SHOW(rd_req,  "%d\n", be->blkif->st_rd_req);
 278 VBD_SHOW(wr_req,  "%d\n", be->blkif->st_wr_req);
 279 VBD_SHOW(f_req,  "%d\n", be->blkif->st_f_req);
 280 VBD_SHOW(rd_sect, "%d\n", be->blkif->st_rd_sect);
 281 VBD_SHOW(wr_sect, "%d\n", be->blkif->st_wr_sect);
 282
 283 static struct attribute *vbdstat_attrs[] = {
 284         &dev_attr_oo_req.attr,
 285         &dev_attr_rd_req.attr,
 286         &dev_attr_wr_req.attr,
 287         &dev_attr_f_req.attr,
 288         &dev_attr_rd_sect.attr,
 289         &dev_attr_wr_sect.attr,
 290         NULL
 291 };
 292
 293 static struct attribute_group vbdstat_group = {
 294         .name = "statistics",
 295         .attrs = vbdstat_attrs,
 296 };
 297
 298 VBD_SHOW(physical_device, "%x:%x\n", be->major, be->minor);
 299 VBD_SHOW(mode, "%s\n", be->mode);
 300
 301 int xenvbd_sysfs_addif(struct xenbus_device *dev)
 302 {
 303         int error;
 304
 305         error = device_create_file(&dev->dev, &dev_attr_physical_device);
 306         if (error)
 307                 goto fail1;
 308
 309         error = device_create_file(&dev->dev, &dev_attr_mode);
 310         if (error)
 311                 goto fail2;
 312
 313         error = sysfs_create_group(&dev->dev.kobj, &vbdstat_group);
 314         if (error)
 315                 goto fail3;
 316
 317         return 0;
 318
 319 fail3:  sysfs_remove_group(&dev->dev.kobj, &vbdstat_group);
 320 fail2:  device_remove_file(&dev->dev, &dev_attr_mode);
 321 fail1:  device_remove_file(&dev->dev, &dev_attr_physical_device);
 322         return error;
 323 }
 324
 325 void xenvbd_sysfs_delif(struct xenbus_device *dev)
 326 {
 327         sysfs_remove_group(&dev->dev.kobj, &vbdstat_group);
 328         device_remove_file(&dev->dev, &dev_attr_mode);
 329         device_remove_file(&dev->dev, &dev_attr_physical_device);
 330 }
 331
 332
 333 static void vbd_free(struct vbd *vbd)
 334 {
 335         if (vbd->bdev)
 336                 blkdev_put(vbd->bdev, vbd->readonly ? FMODE_READ : FMODE_WRITE);
 337         vbd->bdev = NULL;
 338 }
 339
 340 static int vbd_create(struct blkif_st *blkif, blkif_vdev_t handle,
 341                       unsigned major, unsigned minor, int readonly,
 342                       int cdrom)
 343 {
 344         struct vbd *vbd;
 345         struct block_device *bdev;
 346         struct request_queue *q;
 347
 348         vbd = &blkif->vbd;
 349         vbd->handle   = handle;
 350         vbd->readonly = readonly;
 351         vbd->type     = 0;
 352
 353         vbd->pdevice  = MKDEV(major, minor);
 354
 355         bdev = blkdev_get_by_dev(vbd->pdevice, vbd->readonly ?
 356                                  FMODE_READ : FMODE_WRITE, NULL);
 357
 358         if (IS_ERR(bdev)) {
 359                 DPRINTK("vbd_creat: device %08x could not be opened.\n",
 360                         vbd->pdevice);
 361                 return -ENOENT;
 362         }
 363
 364         vbd->bdev = bdev;
 365         vbd->size = vbd_sz(vbd);
 366
 367         if (vbd->bdev->bd_disk == NULL) {
 368                 DPRINTK("vbd_creat: device %08x doesn't exist.\n",
 369                         vbd->pdevice);
 370                 vbd_free(vbd);
 371                 return -ENOENT;
 372         }
 373
 374         if (vbd->bdev->bd_disk->flags & GENHD_FL_CD || cdrom)
 375                 vbd->type |= VDISK_CDROM;
 376         if (vbd->bdev->bd_disk->flags & GENHD_FL_REMOVABLE)
 377                 vbd->type |= VDISK_REMOVABLE;
 378
 379         q = bdev_get_queue(bdev);
 380         if (q && q->flush_flags)
 381                 vbd->flush_support = true;
 382
 383         DPRINTK("Successful creation of handle=%04x (dom=%u)\n",
 384                 handle, blkif->domid);
 385         return 0;
 386 }
 387 static int xen_blkbk_remove(struct xenbus_device *dev)
 388 {
 389         struct backend_info *be = dev_get_drvdata(&dev->dev);
 390
 391         DPRINTK("");
 392
 393         if (be->major || be->minor)
 394                 xenvbd_sysfs_delif(dev);
 395
 396         if (be->backend_watch.node) {
 397                 unregister_xenbus_watch(&be->backend_watch);
 398                 kfree(be->backend_watch.node);
 399                 be->backend_watch.node = NULL;
 400         }
 401
 402         if (be->blkif) {
 403                 xen_blkif_disconnect(be->blkif);
 404                 vbd_free(&be->blkif->vbd);
 405                 xen_blkif_free(be->blkif);
 406                 be->blkif = NULL;
 407         }
 408
 409         kfree(be);
 410         dev_set_drvdata(&dev->dev, NULL);
 411         return 0;
 412 }
 413
 414 int xen_blkbk_flush_diskcache(struct xenbus_transaction xbt,
 415                               struct backend_info *be, int state)
 416 {
 417         struct xenbus_device *dev = be->dev;
 418         int err;
 419
 420         err = xenbus_printf(xbt, dev->nodename, "feature-flush-cache",
 421                             "%d", state);
 422         if (err)
 423                 xenbus_dev_fatal(dev, err, "writing feature-flush-cache");
 424
 425         return err;
 426 }
 427
 428 /**
 429  * Entry point to this code when a new device is created.  Allocate the basic
 430  * structures, and watch the store waiting for the hotplug scripts to tell us
 431  * the device's physical major and minor numbers.  Switch to InitWait.
 432  */
 433 static int xen_blkbk_probe(struct xenbus_device *dev,
 434                            const struct xenbus_device_id *id)
 435 {
 436         int err;
 437         struct backend_info *be = kzalloc(sizeof(struct backend_info),
 438                                           GFP_KERNEL);
 439         if (!be) {
 440                 xenbus_dev_fatal(dev, -ENOMEM,
 441                                  "allocating backend structure");
 442                 return -ENOMEM;
 443         }
 444         be->dev = dev;
 445         dev_set_drvdata(&dev->dev, be);
 446
 447         be->blkif = xen_blkif_alloc(dev->otherend_id);
 448         if (IS_ERR(be->blkif)) {
 449                 err = PTR_ERR(be->blkif);
 450                 be->blkif = NULL;
 451                 xenbus_dev_fatal(dev, err, "creating block interface");
 452                 goto fail;
 453         }
 454
 455         /* setup back pointer */
 456         be->blkif->be = be;
 457
 458         err = xenbus_watch_pathfmt(dev, &be->backend_watch, backend_changed,
 459                                    "%s/%s", dev->nodename, "physical-device");
 460         if (err)
 461                 goto fail;
 462
 463         err = xenbus_switch_state(dev, XenbusStateInitWait);
 464         if (err)
 465                 goto fail;
 466
 467         return 0;
 468
 469 fail:
 470         DPRINTK("failed");
 471         xen_blkbk_remove(dev);
 472         return err;
 473 }
 474
 475
 476 /**
 477  * Callback received when the hotplug scripts have placed the physical-device
 478  * node.  Read it and the mode node, and create a vbd.  If the frontend is
 479  * ready, connect.
 480  */
 481 static void backend_changed(struct xenbus_watch *watch,
 482                             const char **vec, unsigned int len)
 483 {
 484         int err;
 485         unsigned major;
 486         unsigned minor;
 487         struct backend_info *be
 488                 = container_of(watch, struct backend_info, backend_watch);
 489         struct xenbus_device *dev = be->dev;
 490         int cdrom = 0;
 491         char *device_type;
 492
 493         DPRINTK("");
 494
 495         err = xenbus_scanf(XBT_NIL, dev->nodename, "physical-device", "%x:%x",
 496                            &major, &minor);
 497         if (XENBUS_EXIST_ERR(err)) {
 498                 /* Since this watch will fire once immediately after it is
 499                    registered, we expect this.  Ignore it, and wait for the
 500                    hotplug scripts. */
 501                 return;
 502         }
 503         if (err != 2) {
 504                 xenbus_dev_fatal(dev, err, "reading physical-device");
 505                 return;
 506         }
 507
 508         if ((be->major || be->minor) &&
 509             ((be->major != major) || (be->minor != minor))) {
 510                 printk(KERN_WARNING
 511                        "blkback: changing physical device (from %x:%x to "
 512                        "%x:%x) not supported.\n", be->major, be->minor,
 513                        major, minor);
 514                 return;
 515         }
 516
 517         be->mode = xenbus_read(XBT_NIL, dev->nodename, "mode", NULL);
 518         if (IS_ERR(be->mode)) {
 519                 err = PTR_ERR(be->mode);
 520                 be->mode = NULL;
 521                 xenbus_dev_fatal(dev, err, "reading mode");
 522                 return;
 523         }
 524
 525         device_type = xenbus_read(XBT_NIL, dev->otherend, "device-type", NULL);
 526         if (!IS_ERR(device_type)) {
 527                 cdrom = strcmp(device_type, "cdrom") == 0;
 528                 kfree(device_type);
 529         }
 530
 531         if (be->major == 0 && be->minor == 0) {
 532                 /* Front end dir is a number, which is used as the handle. */
 533
 534                 char *p = strrchr(dev->otherend, '/') + 1;
 535                 long handle;
 536                 err = strict_strtoul(p, 0, &handle);
 537                 if (err)
 538                         return;
 539
 540                 be->major = major;
 541                 be->minor = minor;
 542
 543                 err = vbd_create(be->blkif, handle, major, minor,
 544                                  (NULL == strchr(be->mode, 'w')), cdrom);
 545                 if (err) {
 546                         be->major = be->minor = 0;
 547                         xenbus_dev_fatal(dev, err, "creating vbd structure");
 548                         return;
 549                 }
 550
 551                 err = xenvbd_sysfs_addif(dev);
 552                 if (err) {
 553                         vbd_free(&be->blkif->vbd);
 554                         be->major = be->minor = 0;
 555                         xenbus_dev_fatal(dev, err, "creating sysfs entries");
 556                         return;
 557                 }
 558
 559                 /* We're potentially connected now */
 560                 xen_update_blkif_status(be->blkif);
 561         }
 562 }
 563
 564
 565 /**
 566  * Callback received when the frontend's state changes.
 567  */
 568 static void frontend_changed(struct xenbus_device *dev,
 569                              enum xenbus_state frontend_state)
 570 {
 571         struct backend_info *be = dev_get_drvdata(&dev->dev);
 572         int err;
 573
 574         DPRINTK("%s", xenbus_strstate(frontend_state));
 575
 576         switch (frontend_state) {
 577         case XenbusStateInitialising:
 578                 if (dev->state == XenbusStateClosed) {
 579                         printk(KERN_INFO "%s: %s: prepare for reconnect\n",
 580                                __func__, dev->nodename);
 581                         xenbus_switch_state(dev, XenbusStateInitWait);
 582                 }
 583                 break;
 584
 585         case XenbusStateInitialised:
 586         case XenbusStateConnected:
 587                 /* Ensure we connect even when two watches fire in
 588                    close successsion and we miss the intermediate value
 589                    of frontend_state. */
 590                 if (dev->state == XenbusStateConnected)
 591                         break;
 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         printk(KERN_INFO
 732                "blkback: ring-ref %ld, event-channel %d, protocol %d (%s)\n",
 733                ring_ref, evtchn, be->blkif->blk_protocol, protocol);
 734
 735         /* Map the shared frame, irq etc. */
 736         err = xen_blkif_map(be->blkif, ring_ref, evtchn);
 737         if (err) {
 738                 xenbus_dev_fatal(dev, err, "mapping ring-ref %lu port %u",
 739                                  ring_ref, evtchn);
 740                 return err;
 741         }
 742
 743         return 0;
 744 }
 745
 746
 747 /* ** Driver Registration ** */
 748
 749
 750 static const struct xenbus_device_id xen_blkbk_ids[] = {
 751         { "vbd" },
 752         { "" }
 753 };
 754
 755
 756 static struct xenbus_driver xen_blkbk = {
 757         .name = "vbd",
 758         .owner = THIS_MODULE,
 759         .ids = xen_blkbk_ids,
 760         .probe = xen_blkbk_probe,
 761         .remove = xen_blkbk_remove,
 762         .otherend_changed = frontend_changed
 763 };
 764
 765
 766 int xen_blkif_xenbus_init(void)
 767 {
 768         return xenbus_register_backend(&xen_blkbk);
 769 }