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 static void xen_vbd_sync(struct xen_vbd *vbd);
  39
  40 struct xenbus_device *xen_blkbk_xenbus(struct backend_info *be)
  41 {
  42         return be->dev;
  43 }
  44
  45 static int blkback_name(struct xen_blkif *blkif, char *buf)
  46 {
  47         char *devpath, *devname;
  48         struct xenbus_device *dev = blkif->be->dev;
  49
  50         devpath = xenbus_read(XBT_NIL, dev->nodename, "dev", NULL);
  51         if (IS_ERR(devpath))
  52                 return PTR_ERR(devpath);
  53
  54         devname = strstr(devpath, "/dev/");
  55         if (devname != NULL)
  56                 devname += strlen("/dev/");
  57         else
  58                 devname  = devpath;
  59
  60         snprintf(buf, TASK_COMM_LEN, "blkback.%d.%s", blkif->domid, devname);
  61         kfree(devpath);
  62
  63         return 0;
  64 }
  65
  66 static void xen_update_blkif_status(struct xen_blkif *blkif)
  67 {
  68         int err;
  69         char name[TASK_COMM_LEN];
  70
  71         /* Not ready to connect? */
  72         if (!blkif->irq || !blkif->vbd.bdev)
  73                 return;
  74
  75         /* Already connected? */
  76         if (blkif->be->dev->state == XenbusStateConnected)
  77                 return;
  78
  79         /* Attempt to connect: exit if we fail to. */
  80         connect(blkif->be);
  81         if (blkif->be->dev->state != XenbusStateConnected)
  82                 return;
  83
  84         err = blkback_name(blkif, name);
  85         if (err) {
  86                 xenbus_dev_error(blkif->be->dev, err, "get blkback dev name");
  87                 return;
  88         }
  89
  90         err = filemap_write_and_wait(blkif->vbd.bdev->bd_inode->i_mapping);
  91         if (err) {
  92                 xenbus_dev_error(blkif->be->dev, err, "block flush");
  93                 return;
  94         }
  95         invalidate_inode_pages2(blkif->vbd.bdev->bd_inode->i_mapping);
  96
  97         blkif->xenblkd = kthread_run(xen_blkif_schedule, blkif, name);
  98         if (IS_ERR(blkif->xenblkd)) {
  99                 err = PTR_ERR(blkif->xenblkd);
 100                 blkif->xenblkd = NULL;
 101                 xenbus_dev_error(blkif->be->dev, err, "start xenblkd");
 102         }
 103 }
 104
 105 static struct xen_blkif *xen_blkif_alloc(domid_t domid)
 106 {
 107         struct xen_blkif *blkif;
 108
 109         blkif = kmem_cache_alloc(xen_blkif_cachep, GFP_KERNEL);
 110         if (!blkif)
 111                 return ERR_PTR(-ENOMEM);
 112
 113         memset(blkif, 0, sizeof(*blkif));
 114         blkif->domid = domid;
 115         spin_lock_init(&blkif->blk_ring_lock);
 116         atomic_set(&blkif->refcnt, 1);
 117         init_waitqueue_head(&blkif->wq);
 118         blkif->st_print = jiffies;
 119         init_waitqueue_head(&blkif->waiting_to_free);
 120
 121         return blkif;
 122 }
 123
 124 static int map_frontend_page(struct xen_blkif *blkif, unsigned long shared_page)
 125 {
 126         struct gnttab_map_grant_ref op;
 127
 128         gnttab_set_map_op(&op, (unsigned long)blkif->blk_ring_area->addr,
 129                           GNTMAP_host_map, shared_page, blkif->domid);
 130
 131         if (HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, &op, 1))
 132                 BUG();
 133
 134         if (op.status) {
 135                 DPRINTK("Grant table operation failure !\n");
 136                 return op.status;
 137         }
 138
 139         blkif->shmem_ref = shared_page;
 140         blkif->shmem_handle = op.handle;
 141
 142         return 0;
 143 }
 144
 145 static void unmap_frontend_page(struct xen_blkif *blkif)
 146 {
 147         struct gnttab_unmap_grant_ref op;
 148
 149         gnttab_set_unmap_op(&op, (unsigned long)blkif->blk_ring_area->addr,
 150                             GNTMAP_host_map, blkif->shmem_handle);
 151
 152         if (HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, &op, 1))
 153                 BUG();
 154 }
 155
 156 static int xen_blkif_map(struct xen_blkif *blkif, unsigned long shared_page,
 157                          unsigned int evtchn)
 158 {
 159         int err;
 160
 161         /* Already connected through? */
 162         if (blkif->irq)
 163                 return 0;
 164
 165         blkif->blk_ring_area = alloc_vm_area(PAGE_SIZE);
 166         if (!blkif->blk_ring_area)
 167                 return -ENOMEM;
 168
 169         err = map_frontend_page(blkif, shared_page);
 170         if (err) {
 171                 free_vm_area(blkif->blk_ring_area);
 172                 return err;
 173         }
 174
 175         switch (blkif->blk_protocol) {
 176         case BLKIF_PROTOCOL_NATIVE:
 177         {
 178                 struct blkif_sring *sring;
 179                 sring = (struct blkif_sring *)blkif->blk_ring_area->addr;
 180                 BACK_RING_INIT(&blkif->blk_rings.native, sring, PAGE_SIZE);
 181                 break;
 182         }
 183         case BLKIF_PROTOCOL_X86_32:
 184         {
 185                 struct blkif_x86_32_sring *sring_x86_32;
 186                 sring_x86_32 = (struct blkif_x86_32_sring *)blkif->blk_ring_area->addr;
 187                 BACK_RING_INIT(&blkif->blk_rings.x86_32, sring_x86_32, PAGE_SIZE);
 188                 break;
 189         }
 190         case BLKIF_PROTOCOL_X86_64:
 191         {
 192                 struct blkif_x86_64_sring *sring_x86_64;
 193                 sring_x86_64 = (struct blkif_x86_64_sring *)blkif->blk_ring_area->addr;
 194                 BACK_RING_INIT(&blkif->blk_rings.x86_64, sring_x86_64, PAGE_SIZE);
 195                 break;
 196         }
 197         default:
 198                 BUG();
 199         }
 200
 201         err = bind_interdomain_evtchn_to_irqhandler(blkif->domid, evtchn,
 202                                                     xen_blkif_be_int, 0,
 203                                                     "blkif-backend", blkif);
 204         if (err < 0) {
 205                 unmap_frontend_page(blkif);
 206                 free_vm_area(blkif->blk_ring_area);
 207                 blkif->blk_rings.common.sring = NULL;
 208                 return err;
 209         }
 210         blkif->irq = err;
 211
 212         return 0;
 213 }
 214
 215 static void xen_blkif_disconnect(struct xen_blkif *blkif)
 216 {
 217         if (blkif->xenblkd) {
 218                 kthread_stop(blkif->xenblkd);
 219                 blkif->xenblkd = NULL;
 220         }
 221
 222         atomic_dec(&blkif->refcnt);
 223         wait_event(blkif->waiting_to_free, atomic_read(&blkif->refcnt) == 0);
 224         atomic_inc(&blkif->refcnt);
 225
 226         if (blkif->irq) {
 227                 unbind_from_irqhandler(blkif->irq, blkif);
 228                 blkif->irq = 0;
 229         }
 230
 231         if (blkif->blk_rings.common.sring) {
 232                 unmap_frontend_page(blkif);
 233                 free_vm_area(blkif->blk_ring_area);
 234                 blkif->blk_rings.common.sring = NULL;
 235         }
 236         xen_vbd_sync(&blkif->vbd);
 237 }
 238
 239 void xen_blkif_free(struct xen_blkif *blkif)
 240 {
 241         if (!atomic_dec_and_test(&blkif->refcnt))
 242                 BUG();
 243         kmem_cache_free(xen_blkif_cachep, blkif);
 244 }
 245
 246 int __init xen_blkif_interface_init(void)
 247 {
 248         xen_blkif_cachep = kmem_cache_create("blkif_cache",
 249                                              sizeof(struct xen_blkif),
 250                                              0, 0, NULL);
 251         if (!xen_blkif_cachep)
 252                 return -ENOMEM;
 253
 254         return 0;
 255 }
 256
 257 /*
 258  *  sysfs interface for VBD I/O requests
 259  */
 260
 261 #define VBD_SHOW(name, format, args...)                                 \
 262         static ssize_t show_##name(struct device *_dev,                 \
 263                                    struct device_attribute *attr,       \
 264                                    char *buf)                           \
 265         {                                                               \
 266                 struct xenbus_device *dev = to_xenbus_device(_dev);     \
 267                 struct backend_info *be = dev_get_drvdata(&dev->dev);   \
 268                                                                         \
 269                 return sprintf(buf, format, ##args);                    \
 270         }                                                               \
 271         static DEVICE_ATTR(name, S_IRUGO, show_##name, NULL)
 272
 273 VBD_SHOW(oo_req,  "%d\n", be->blkif->st_oo_req);
 274 VBD_SHOW(rd_req,  "%d\n", be->blkif->st_rd_req);
 275 VBD_SHOW(wr_req,  "%d\n", be->blkif->st_wr_req);
 276 VBD_SHOW(f_req,  "%d\n", be->blkif->st_f_req);
 277 VBD_SHOW(rd_sect, "%d\n", be->blkif->st_rd_sect);
 278 VBD_SHOW(wr_sect, "%d\n", be->blkif->st_wr_sect);
 279
 280 static struct attribute *xen_vbdstat_attrs[] = {
 281         &dev_attr_oo_req.attr,
 282         &dev_attr_rd_req.attr,
 283         &dev_attr_wr_req.attr,
 284         &dev_attr_f_req.attr,
 285         &dev_attr_rd_sect.attr,
 286         &dev_attr_wr_sect.attr,
 287         NULL
 288 };
 289
 290 static struct attribute_group xen_vbdstat_group = {
 291         .name = "statistics",
 292         .attrs = xen_vbdstat_attrs,
 293 };
 294
 295 VBD_SHOW(physical_device, "%x:%x\n", be->major, be->minor);
 296 VBD_SHOW(mode, "%s\n", be->mode);
 297
 298 int xenvbd_sysfs_addif(struct xenbus_device *dev)
 299 {
 300         int error;
 301
 302         error = device_create_file(&dev->dev, &dev_attr_physical_device);
 303         if (error)
 304                 goto fail1;
 305
 306         error = device_create_file(&dev->dev, &dev_attr_mode);
 307         if (error)
 308                 goto fail2;
 309
 310         error = sysfs_create_group(&dev->dev.kobj, &xen_vbdstat_group);
 311         if (error)
 312                 goto fail3;
 313
 314         return 0;
 315
 316 fail3:  sysfs_remove_group(&dev->dev.kobj, &xen_vbdstat_group);
 317 fail2:  device_remove_file(&dev->dev, &dev_attr_mode);
 318 fail1:  device_remove_file(&dev->dev, &dev_attr_physical_device);
 319         return error;
 320 }
 321
 322 void xenvbd_sysfs_delif(struct xenbus_device *dev)
 323 {
 324         sysfs_remove_group(&dev->dev.kobj, &xen_vbdstat_group);
 325         device_remove_file(&dev->dev, &dev_attr_mode);
 326         device_remove_file(&dev->dev, &dev_attr_physical_device);
 327 }
 328
 329
 330 static void xen_vbd_free(struct xen_vbd *vbd)
 331 {
 332         if (vbd->bdev)
 333                 blkdev_put(vbd->bdev, vbd->readonly ? FMODE_READ : FMODE_WRITE);
 334         vbd->bdev = NULL;
 335 }
 336
 337 static void xen_vbd_sync(struct xen_vbd *vbd)
 338 {
 339         if (vbd->bdev)
 340                 fsync_bdev(vbd->bdev);
 341 }
 342
 343 static int xen_vbd_create(struct xen_blkif *blkif, blkif_vdev_t handle,
 344                           unsigned major, unsigned minor, int readonly,
 345                           int cdrom)
 346 {
 347         struct xen_vbd *vbd;
 348         struct block_device *bdev;
 349         struct request_queue *q;
 350
 351         vbd = &blkif->vbd;
 352         vbd->handle   = handle;
 353         vbd->readonly = readonly;
 354         vbd->type     = 0;
 355
 356         vbd->pdevice  = MKDEV(major, minor);
 357
 358         bdev = blkdev_get_by_dev(vbd->pdevice, vbd->readonly ?
 359                                  FMODE_READ : FMODE_WRITE, NULL);
 360
 361         if (IS_ERR(bdev)) {
 362                 DPRINTK("xen_vbd_create: device %08x could not be opened.\n",
 363                         vbd->pdevice);
 364                 return -ENOENT;
 365         }
 366
 367         vbd->bdev = bdev;
 368         if (vbd->bdev->bd_disk == NULL) {
 369                 DPRINTK("xen_vbd_create: device %08x doesn't exist.\n",
 370                         vbd->pdevice);
 371                 xen_vbd_free(vbd);
 372                 return -ENOENT;
 373         }
 374         vbd->size = vbd_sz(vbd);
 375
 376         if (vbd->bdev->bd_disk->flags & GENHD_FL_CD || cdrom)
 377                 vbd->type |= VDISK_CDROM;
 378         if (vbd->bdev->bd_disk->flags & GENHD_FL_REMOVABLE)
 379                 vbd->type |= VDISK_REMOVABLE;
 380
 381         q = bdev_get_queue(bdev);
 382         if (q && q->flush_flags)
 383                 vbd->flush_support = true;
 384
 385         DPRINTK("Successful creation of handle=%04x (dom=%u)\n",
 386                 handle, blkif->domid);
 387         return 0;
 388 }
 389 static int xen_blkbk_remove(struct xenbus_device *dev)
 390 {
 391         struct backend_info *be = dev_get_drvdata(&dev->dev);
 392
 393         DPRINTK("");
 394
 395         if (be->major || be->minor)
 396                 xenvbd_sysfs_delif(dev);
 397
 398         if (be->backend_watch.node) {
 399                 unregister_xenbus_watch(&be->backend_watch);
 400                 kfree(be->backend_watch.node);
 401                 be->backend_watch.node = NULL;
 402         }
 403
 404         if (be->blkif) {
 405                 xen_blkif_disconnect(be->blkif);
 406                 xen_vbd_free(&be->blkif->vbd);
 407                 xen_blkif_free(be->blkif);
 408                 be->blkif = NULL;
 409         }
 410
 411         kfree(be);
 412         dev_set_drvdata(&dev->dev, NULL);
 413         return 0;
 414 }
 415
 416 int xen_blkbk_flush_diskcache(struct xenbus_transaction xbt,
 417                               struct backend_info *be, int state)
 418 {
 419         struct xenbus_device *dev = be->dev;
 420         int err;
 421
 422         err = xenbus_printf(xbt, dev->nodename, "feature-flush-cache",
 423                             "%d", state);
 424         if (err)
 425                 xenbus_dev_fatal(dev, err, "writing feature-flush-cache");
 426
 427         return err;
 428 }
 429
 430 /*
 431  * Entry point to this code when a new device is created.  Allocate the basic
 432  * structures, and watch the store waiting for the hotplug scripts to tell us
 433  * the device's physical major and minor numbers.  Switch to InitWait.
 434  */
 435 static int xen_blkbk_probe(struct xenbus_device *dev,
 436                            const struct xenbus_device_id *id)
 437 {
 438         int err;
 439         struct backend_info *be = kzalloc(sizeof(struct backend_info),
 440                                           GFP_KERNEL);
 441         if (!be) {
 442                 xenbus_dev_fatal(dev, -ENOMEM,
 443                                  "allocating backend structure");
 444                 return -ENOMEM;
 445         }
 446         be->dev = dev;
 447         dev_set_drvdata(&dev->dev, be);
 448
 449         be->blkif = xen_blkif_alloc(dev->otherend_id);
 450         if (IS_ERR(be->blkif)) {
 451                 err = PTR_ERR(be->blkif);
 452                 be->blkif = NULL;
 453                 xenbus_dev_fatal(dev, err, "creating block interface");
 454                 goto fail;
 455         }
 456
 457         /* setup back pointer */
 458         be->blkif->be = be;
 459
 460         err = xenbus_watch_pathfmt(dev, &be->backend_watch, backend_changed,
 461                                    "%s/%s", dev->nodename, "physical-device");
 462         if (err)
 463                 goto fail;
 464
 465         err = xenbus_switch_state(dev, XenbusStateInitWait);
 466         if (err)
 467                 goto fail;
 468
 469         return 0;
 470
 471 fail:
 472         DPRINTK("failed");
 473         xen_blkbk_remove(dev);
 474         return err;
 475 }
 476
 477
 478 /*
 479  * Callback received when the hotplug scripts have placed the physical-device
 480  * node.  Read it and the mode node, and create a vbd.  If the frontend is
 481  * ready, connect.
 482  */
 483 static void backend_changed(struct xenbus_watch *watch,
 484                             const char **vec, unsigned int len)
 485 {
 486         int err;
 487         unsigned major;
 488         unsigned minor;
 489         struct backend_info *be
 490                 = container_of(watch, struct backend_info, backend_watch);
 491         struct xenbus_device *dev = be->dev;
 492         int cdrom = 0;
 493         char *device_type;
 494
 495         DPRINTK("");
 496
 497         err = xenbus_scanf(XBT_NIL, dev->nodename, "physical-device", "%x:%x",
 498                            &major, &minor);
 499         if (XENBUS_EXIST_ERR(err)) {
 500                 /*
 501                  * Since this watch will fire once immediately after it is
 502                  * registered, we expect this.  Ignore it, and wait for the
 503                  * hotplug scripts.
 504                  */
 505                 return;
 506         }
 507         if (err != 2) {
 508                 xenbus_dev_fatal(dev, err, "reading physical-device");
 509                 return;
 510         }
 511
 512         if ((be->major || be->minor) &&
 513             ((be->major != major) || (be->minor != minor))) {
 514                 pr_warn(DRV_PFX "changing physical device (from %x:%x to %x:%x) not supported.\n",
 515                         be->major, be->minor, major, minor);
 516                 return;
 517         }
 518
 519         be->mode = xenbus_read(XBT_NIL, dev->nodename, "mode", NULL);
 520         if (IS_ERR(be->mode)) {
 521                 err = PTR_ERR(be->mode);
 522                 be->mode = NULL;
 523                 xenbus_dev_fatal(dev, err, "reading mode");
 524                 return;
 525         }
 526
 527         device_type = xenbus_read(XBT_NIL, dev->otherend, "device-type", NULL);
 528         if (!IS_ERR(device_type)) {
 529                 cdrom = strcmp(device_type, "cdrom") == 0;
 530                 kfree(device_type);
 531         }
 532
 533         if (be->major == 0 && be->minor == 0) {
 534                 /* Front end dir is a number, which is used as the handle. */
 535
 536                 char *p = strrchr(dev->otherend, '/') + 1;
 537                 long handle;
 538                 err = strict_strtoul(p, 0, &handle);
 539                 if (err)
 540                         return;
 541
 542                 be->major = major;
 543                 be->minor = minor;
 544
 545                 err = xen_vbd_create(be->blkif, handle, major, minor,
 546                                  (NULL == strchr(be->mode, 'w')), cdrom);
 547                 if (err) {
 548                         be->major = 0;
 549                         be->minor = 0;
 550                         xenbus_dev_fatal(dev, err, "creating vbd structure");
 551                         return;
 552                 }
 553
 554                 err = xenvbd_sysfs_addif(dev);
 555                 if (err) {
 556                         xen_vbd_free(&be->blkif->vbd);
 557                         be->major = 0;
 558                         be->minor = 0;
 559                         xenbus_dev_fatal(dev, err, "creating sysfs entries");
 560                         return;
 561                 }
 562
 563                 /* We're potentially connected now */
 564                 xen_update_blkif_status(be->blkif);
 565         }
 566 }
 567
 568
 569 /*
 570  * Callback received when the frontend's state changes.
 571  */
 572 static void frontend_changed(struct xenbus_device *dev,
 573                              enum xenbus_state frontend_state)
 574 {
 575         struct backend_info *be = dev_get_drvdata(&dev->dev);
 576         int err;
 577
 578         DPRINTK("%s", xenbus_strstate(frontend_state));
 579
 580         switch (frontend_state) {
 581         case XenbusStateInitialising:
 582                 if (dev->state == XenbusStateClosed) {
 583                         pr_info(DRV_PFX "%s: prepare for reconnect\n",
 584                                 dev->nodename);
 585                         xenbus_switch_state(dev, XenbusStateInitWait);
 586                 }
 587                 break;
 588
 589         case XenbusStateInitialised:
 590         case XenbusStateConnected:
 591                 /*
 592                  * Ensure we connect even when two watches fire in
 593                  * close successsion and we miss the intermediate value
 594                  * of frontend_state.
 595                  */
 596                 if (dev->state == XenbusStateConnected)
 597                         break;
 598
 599                 /*
 600                  * Enforce precondition before potential leak point.
 601                  * xen_blkif_disconnect() is idempotent.
 602                  */
 603                 xen_blkif_disconnect(be->blkif);
 604
 605                 err = connect_ring(be);
 606                 if (err)
 607                         break;
 608                 xen_update_blkif_status(be->blkif);
 609                 break;
 610
 611         case XenbusStateClosing:
 612                 xenbus_switch_state(dev, XenbusStateClosing);
 613                 break;
 614
 615         case XenbusStateClosed:
 616                 xen_blkif_disconnect(be->blkif);
 617                 xenbus_switch_state(dev, XenbusStateClosed);
 618                 if (xenbus_dev_is_online(dev))
 619                         break;
 620                 /* fall through if not online */
 621         case XenbusStateUnknown:
 622                 /* implies xen_blkif_disconnect() via xen_blkbk_remove() */
 623                 device_unregister(&dev->dev);
 624                 break;
 625
 626         default:
 627                 xenbus_dev_fatal(dev, -EINVAL, "saw state %d at frontend",
 628                                  frontend_state);
 629                 break;
 630         }
 631 }
 632
 633
 634 /* ** Connection ** */
 635
 636
 637 /*
 638  * Write the physical details regarding the block device to the store, and
 639  * switch to Connected state.
 640  */
 641 static void connect(struct backend_info *be)
 642 {
 643         struct xenbus_transaction xbt;
 644         int err;
 645         struct xenbus_device *dev = be->dev;
 646
 647         DPRINTK("%s", dev->otherend);
 648
 649         /* Supply the information about the device the frontend needs */
 650 again:
 651         err = xenbus_transaction_start(&xbt);
 652         if (err) {
 653                 xenbus_dev_fatal(dev, err, "starting transaction");
 654                 return;
 655         }
 656
 657         err = xen_blkbk_flush_diskcache(xbt, be, be->blkif->vbd.flush_support);
 658         if (err)
 659                 goto abort;
 660
 661         err = xenbus_printf(xbt, dev->nodename, "sectors", "%llu",
 662                             (unsigned long long)vbd_sz(&be->blkif->vbd));
 663         if (err) {
 664                 xenbus_dev_fatal(dev, err, "writing %s/sectors",
 665                                  dev->nodename);
 666                 goto abort;
 667         }
 668
 669         /* FIXME: use a typename instead */
 670         err = xenbus_printf(xbt, dev->nodename, "info", "%u",
 671                             be->blkif->vbd.type |
 672                             (be->blkif->vbd.readonly ? VDISK_READONLY : 0));
 673         if (err) {
 674                 xenbus_dev_fatal(dev, err, "writing %s/info",
 675                                  dev->nodename);
 676                 goto abort;
 677         }
 678         err = xenbus_printf(xbt, dev->nodename, "sector-size", "%lu",
 679                             (unsigned long)
 680                             bdev_logical_block_size(be->blkif->vbd.bdev));
 681         if (err) {
 682                 xenbus_dev_fatal(dev, err, "writing %s/sector-size",
 683                                  dev->nodename);
 684                 goto abort;
 685         }
 686
 687         err = xenbus_transaction_end(xbt, 0);
 688         if (err == -EAGAIN)
 689                 goto again;
 690         if (err)
 691                 xenbus_dev_fatal(dev, err, "ending transaction");
 692
 693         err = xenbus_switch_state(dev, XenbusStateConnected);
 694         if (err)
 695                 xenbus_dev_fatal(dev, err, "%s: switching to Connected state",
 696                                  dev->nodename);
 697
 698         return;
 699  abort:
 700         xenbus_transaction_end(xbt, 1);
 701 }
 702
 703
 704 static int connect_ring(struct backend_info *be)
 705 {
 706         struct xenbus_device *dev = be->dev;
 707         unsigned long ring_ref;
 708         unsigned int evtchn;
 709         char protocol[64] = "";
 710         int err;
 711
 712         DPRINTK("%s", dev->otherend);
 713
 714         err = xenbus_gather(XBT_NIL, dev->otherend, "ring-ref", "%lu",
 715                             &ring_ref, "event-channel", "%u", &evtchn, NULL);
 716         if (err) {
 717                 xenbus_dev_fatal(dev, err,
 718                                  "reading %s/ring-ref and event-channel",
 719                                  dev->otherend);
 720                 return err;
 721         }
 722
 723         be->blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
 724         err = xenbus_gather(XBT_NIL, dev->otherend, "protocol",
 725                             "%63s", protocol, NULL);
 726         if (err)
 727                 strcpy(protocol, "unspecified, assuming native");
 728         else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_NATIVE))
 729                 be->blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
 730         else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_32))
 731                 be->blkif->blk_protocol = BLKIF_PROTOCOL_X86_32;
 732         else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_64))
 733                 be->blkif->blk_protocol = BLKIF_PROTOCOL_X86_64;
 734         else {
 735                 xenbus_dev_fatal(dev, err, "unknown fe protocol %s", protocol);
 736                 return -1;
 737         }
 738         pr_info(DRV_PFX "ring-ref %ld, event-channel %d, protocol %d (%s)\n",
 739                 ring_ref, evtchn, be->blkif->blk_protocol, protocol);
 740
 741         /* Map the shared frame, irq etc. */
 742         err = xen_blkif_map(be->blkif, ring_ref, evtchn);
 743         if (err) {
 744                 xenbus_dev_fatal(dev, err, "mapping ring-ref %lu port %u",
 745                                  ring_ref, evtchn);
 746                 return err;
 747         }
 748
 749         return 0;
 750 }
 751
 752
 753 /* ** Driver Registration ** */
 754
 755
 756 static const struct xenbus_device_id xen_blkbk_ids[] = {
 757         { "vbd" },
 758         { "" }
 759 };
 760
 761
 762 static struct xenbus_driver xen_blkbk = {
 763         .name = "vbd",
 764         .owner = THIS_MODULE,
 765         .ids = xen_blkbk_ids,
 766         .probe = xen_blkbk_probe,
 767         .remove = xen_blkbk_remove,
 768         .otherend_changed = frontend_changed
 769 };
 770
 771
 772 int xen_blkif_xenbus_init(void)
 773 {
 774         return xenbus_register_backend(&xen_blkbk);
 775 }