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_zalloc(xen_blkif_cachep, GFP_KERNEL);
 109         if (!blkif)
 110                 return ERR_PTR(-ENOMEM);
 111
 112         blkif->domid = domid;
 113         spin_lock_init(&blkif->blk_ring_lock);
 114         atomic_set(&blkif->refcnt, 1);
 115         init_waitqueue_head(&blkif->wq);
 116         init_completion(&blkif->drain_complete);
 117         atomic_set(&blkif->drain, 0);
 118         blkif->st_print = jiffies;
 119         init_waitqueue_head(&blkif->waiting_to_free);
 120         blkif->persistent_gnts.rb_node = NULL;
 121
 122         return blkif;
 123 }
 124
 125 static int xen_blkif_map(struct xen_blkif *blkif, unsigned long shared_page,
 126                          unsigned int evtchn)
 127 {
 128         int err;
 129
 130         /* Already connected through? */
 131         if (blkif->irq)
 132                 return 0;
 133
 134         err = xenbus_map_ring_valloc(blkif->be->dev, shared_page, &blkif->blk_ring);
 135         if (err < 0)
 136                 return err;
 137
 138         switch (blkif->blk_protocol) {
 139         case BLKIF_PROTOCOL_NATIVE:
 140         {
 141                 struct blkif_sring *sring;
 142                 sring = (struct blkif_sring *)blkif->blk_ring;
 143                 BACK_RING_INIT(&blkif->blk_rings.native, sring, PAGE_SIZE);
 144                 break;
 145         }
 146         case BLKIF_PROTOCOL_X86_32:
 147         {
 148                 struct blkif_x86_32_sring *sring_x86_32;
 149                 sring_x86_32 = (struct blkif_x86_32_sring *)blkif->blk_ring;
 150                 BACK_RING_INIT(&blkif->blk_rings.x86_32, sring_x86_32, PAGE_SIZE);
 151                 break;
 152         }
 153         case BLKIF_PROTOCOL_X86_64:
 154         {
 155                 struct blkif_x86_64_sring *sring_x86_64;
 156                 sring_x86_64 = (struct blkif_x86_64_sring *)blkif->blk_ring;
 157                 BACK_RING_INIT(&blkif->blk_rings.x86_64, sring_x86_64, PAGE_SIZE);
 158                 break;
 159         }
 160         default:
 161                 BUG();
 162         }
 163
 164         err = bind_interdomain_evtchn_to_irqhandler(blkif->domid, evtchn,
 165                                                     xen_blkif_be_int, 0,
 166                                                     "blkif-backend", blkif);
 167         if (err < 0) {
 168                 xenbus_unmap_ring_vfree(blkif->be->dev, blkif->blk_ring);
 169                 blkif->blk_rings.common.sring = NULL;
 170                 return err;
 171         }
 172         blkif->irq = err;
 173
 174         return 0;
 175 }
 176
 177 static void xen_blkif_disconnect(struct xen_blkif *blkif)
 178 {
 179         if (blkif->xenblkd) {
 180                 kthread_stop(blkif->xenblkd);
 181                 blkif->xenblkd = NULL;
 182         }
 183
 184         atomic_dec(&blkif->refcnt);
 185         wait_event(blkif->waiting_to_free, atomic_read(&blkif->refcnt) == 0);
 186         atomic_inc(&blkif->refcnt);
 187
 188         if (blkif->irq) {
 189                 unbind_from_irqhandler(blkif->irq, blkif);
 190                 blkif->irq = 0;
 191         }
 192
 193         if (blkif->blk_rings.common.sring) {
 194                 xenbus_unmap_ring_vfree(blkif->be->dev, blkif->blk_ring);
 195                 blkif->blk_rings.common.sring = NULL;
 196         }
 197 }
 198
 199 static void xen_blkif_free(struct xen_blkif *blkif)
 200 {
 201         if (!atomic_dec_and_test(&blkif->refcnt))
 202                 BUG();
 203         kmem_cache_free(xen_blkif_cachep, blkif);
 204 }
 205
 206 int __init xen_blkif_interface_init(void)
 207 {
 208         xen_blkif_cachep = kmem_cache_create("blkif_cache",
 209                                              sizeof(struct xen_blkif),
 210                                              0, 0, NULL);
 211         if (!xen_blkif_cachep)
 212                 return -ENOMEM;
 213
 214         return 0;
 215 }
 216
 217 /*
 218  *  sysfs interface for VBD I/O requests
 219  */
 220
 221 #define VBD_SHOW(name, format, args...)                                 \
 222         static ssize_t show_##name(struct device *_dev,                 \
 223                                    struct device_attribute *attr,       \
 224                                    char *buf)                           \
 225         {                                                               \
 226                 struct xenbus_device *dev = to_xenbus_device(_dev);     \
 227                 struct backend_info *be = dev_get_drvdata(&dev->dev);   \
 228                                                                         \
 229                 return sprintf(buf, format, ##args);                    \
 230         }                                                               \
 231         static DEVICE_ATTR(name, S_IRUGO, show_##name, NULL)
 232
 233 VBD_SHOW(oo_req,  "%llu\n", be->blkif->st_oo_req);
 234 VBD_SHOW(rd_req,  "%llu\n", be->blkif->st_rd_req);
 235 VBD_SHOW(wr_req,  "%llu\n", be->blkif->st_wr_req);
 236 VBD_SHOW(f_req,  "%llu\n", be->blkif->st_f_req);
 237 VBD_SHOW(ds_req,  "%llu\n", be->blkif->st_ds_req);
 238 VBD_SHOW(rd_sect, "%llu\n", be->blkif->st_rd_sect);
 239 VBD_SHOW(wr_sect, "%llu\n", be->blkif->st_wr_sect);
 240
 241 static struct attribute *xen_vbdstat_attrs[] = {
 242         &dev_attr_oo_req.attr,
 243         &dev_attr_rd_req.attr,
 244         &dev_attr_wr_req.attr,
 245         &dev_attr_f_req.attr,
 246         &dev_attr_ds_req.attr,
 247         &dev_attr_rd_sect.attr,
 248         &dev_attr_wr_sect.attr,
 249         NULL
 250 };
 251
 252 static struct attribute_group xen_vbdstat_group = {
 253         .name = "statistics",
 254         .attrs = xen_vbdstat_attrs,
 255 };
 256
 257 VBD_SHOW(physical_device, "%x:%x\n", be->major, be->minor);
 258 VBD_SHOW(mode, "%s\n", be->mode);
 259
 260 static int xenvbd_sysfs_addif(struct xenbus_device *dev)
 261 {
 262         int error;
 263
 264         error = device_create_file(&dev->dev, &dev_attr_physical_device);
 265         if (error)
 266                 goto fail1;
 267
 268         error = device_create_file(&dev->dev, &dev_attr_mode);
 269         if (error)
 270                 goto fail2;
 271
 272         error = sysfs_create_group(&dev->dev.kobj, &xen_vbdstat_group);
 273         if (error)
 274                 goto fail3;
 275
 276         return 0;
 277
 278 fail3:  sysfs_remove_group(&dev->dev.kobj, &xen_vbdstat_group);
 279 fail2:  device_remove_file(&dev->dev, &dev_attr_mode);
 280 fail1:  device_remove_file(&dev->dev, &dev_attr_physical_device);
 281         return error;
 282 }
 283
 284 static void xenvbd_sysfs_delif(struct xenbus_device *dev)
 285 {
 286         sysfs_remove_group(&dev->dev.kobj, &xen_vbdstat_group);
 287         device_remove_file(&dev->dev, &dev_attr_mode);
 288         device_remove_file(&dev->dev, &dev_attr_physical_device);
 289 }
 290
 291
 292 static void xen_vbd_free(struct xen_vbd *vbd)
 293 {
 294         if (vbd->bdev)
 295                 blkdev_put(vbd->bdev, vbd->readonly ? FMODE_READ : FMODE_WRITE);
 296         vbd->bdev = NULL;
 297 }
 298
 299 static int xen_vbd_create(struct xen_blkif *blkif, blkif_vdev_t handle,
 300                           unsigned major, unsigned minor, int readonly,
 301                           int cdrom)
 302 {
 303         struct xen_vbd *vbd;
 304         struct block_device *bdev;
 305         struct request_queue *q;
 306
 307         vbd = &blkif->vbd;
 308         vbd->handle   = handle;
 309         vbd->readonly = readonly;
 310         vbd->type     = 0;
 311
 312         vbd->pdevice  = MKDEV(major, minor);
 313
 314         bdev = blkdev_get_by_dev(vbd->pdevice, vbd->readonly ?
 315                                  FMODE_READ : FMODE_WRITE, NULL);
 316
 317         if (IS_ERR(bdev)) {
 318                 DPRINTK("xen_vbd_create: device %08x could not be opened.\n",
 319                         vbd->pdevice);
 320                 return -ENOENT;
 321         }
 322
 323         vbd->bdev = bdev;
 324         if (vbd->bdev->bd_disk == NULL) {
 325                 DPRINTK("xen_vbd_create: device %08x doesn't exist.\n",
 326                         vbd->pdevice);
 327                 xen_vbd_free(vbd);
 328                 return -ENOENT;
 329         }
 330         vbd->size = vbd_sz(vbd);
 331
 332         if (vbd->bdev->bd_disk->flags & GENHD_FL_CD || cdrom)
 333                 vbd->type |= VDISK_CDROM;
 334         if (vbd->bdev->bd_disk->flags & GENHD_FL_REMOVABLE)
 335                 vbd->type |= VDISK_REMOVABLE;
 336
 337         q = bdev_get_queue(bdev);
 338         if (q && q->flush_flags)
 339                 vbd->flush_support = true;
 340
 341         if (q && blk_queue_secdiscard(q))
 342                 vbd->discard_secure = true;
 343
 344         DPRINTK("Successful creation of handle=%04x (dom=%u)\n",
 345                 handle, blkif->domid);
 346         return 0;
 347 }
 348 static int xen_blkbk_remove(struct xenbus_device *dev)
 349 {
 350         struct backend_info *be = dev_get_drvdata(&dev->dev);
 351
 352         DPRINTK("");
 353
 354         if (be->major || be->minor)
 355                 xenvbd_sysfs_delif(dev);
 356
 357         if (be->backend_watch.node) {
 358                 unregister_xenbus_watch(&be->backend_watch);
 359                 kfree(be->backend_watch.node);
 360                 be->backend_watch.node = NULL;
 361         }
 362
 363         if (be->blkif) {
 364                 xen_blkif_disconnect(be->blkif);
 365                 xen_vbd_free(&be->blkif->vbd);
 366                 xen_blkif_free(be->blkif);
 367                 be->blkif = NULL;
 368         }
 369
 370         kfree(be->mode);
 371         kfree(be);
 372         dev_set_drvdata(&dev->dev, NULL);
 373         return 0;
 374 }
 375
 376 int xen_blkbk_flush_diskcache(struct xenbus_transaction xbt,
 377                               struct backend_info *be, int state)
 378 {
 379         struct xenbus_device *dev = be->dev;
 380         int err;
 381
 382         err = xenbus_printf(xbt, dev->nodename, "feature-flush-cache",
 383                             "%d", state);
 384         if (err)
 385                 dev_warn(&dev->dev, "writing feature-flush-cache (%d)", err);
 386
 387         return err;
 388 }
 389
 390 static void xen_blkbk_discard(struct xenbus_transaction xbt, struct backend_info *be)
 391 {
 392         struct xenbus_device *dev = be->dev;
 393         struct xen_blkif *blkif = be->blkif;
 394         int err;
 395         int state = 0;
 396         struct block_device *bdev = be->blkif->vbd.bdev;
 397         struct request_queue *q = bdev_get_queue(bdev);
 398
 399         if (blk_queue_discard(q)) {
 400                 err = xenbus_printf(xbt, dev->nodename,
 401                         "discard-granularity", "%u",
 402                         q->limits.discard_granularity);
 403                 if (err) {
 404                         dev_warn(&dev->dev, "writing discard-granularity (%d)", err);
 405                         return;
 406                 }
 407                 err = xenbus_printf(xbt, dev->nodename,
 408                         "discard-alignment", "%u",
 409                         q->limits.discard_alignment);
 410                 if (err) {
 411                         dev_warn(&dev->dev, "writing discard-alignment (%d)", err);
 412                         return;
 413                 }
 414                 state = 1;
 415                 /* Optional. */
 416                 err = xenbus_printf(xbt, dev->nodename,
 417                                     "discard-secure", "%d",
 418                                     blkif->vbd.discard_secure);
 419                 if (err) {
 420                         dev_warn(&dev->dev, "writing discard-secure (%d)", err);
 421                         return;
 422                 }
 423         }
 424         err = xenbus_printf(xbt, dev->nodename, "feature-discard",
 425                             "%d", state);
 426         if (err)
 427                 dev_warn(&dev->dev, "writing feature-discard (%d)", err);
 428 }
 429 int xen_blkbk_barrier(struct xenbus_transaction xbt,
 430                       struct backend_info *be, int state)
 431 {
 432         struct xenbus_device *dev = be->dev;
 433         int err;
 434
 435         err = xenbus_printf(xbt, dev->nodename, "feature-barrier",
 436                             "%d", state);
 437         if (err)
 438                 dev_warn(&dev->dev, "writing feature-barrier (%d)", err);
 439
 440         return err;
 441 }
 442
 443 /*
 444  * Entry point to this code when a new device is created.  Allocate the basic
 445  * structures, and watch the store waiting for the hotplug scripts to tell us
 446  * the device's physical major and minor numbers.  Switch to InitWait.
 447  */
 448 static int xen_blkbk_probe(struct xenbus_device *dev,
 449                            const struct xenbus_device_id *id)
 450 {
 451         int err;
 452         struct backend_info *be = kzalloc(sizeof(struct backend_info),
 453                                           GFP_KERNEL);
 454         if (!be) {
 455                 xenbus_dev_fatal(dev, -ENOMEM,
 456                                  "allocating backend structure");
 457                 return -ENOMEM;
 458         }
 459         be->dev = dev;
 460         dev_set_drvdata(&dev->dev, be);
 461
 462         be->blkif = xen_blkif_alloc(dev->otherend_id);
 463         if (IS_ERR(be->blkif)) {
 464                 err = PTR_ERR(be->blkif);
 465                 be->blkif = NULL;
 466                 xenbus_dev_fatal(dev, err, "creating block interface");
 467                 goto fail;
 468         }
 469
 470         /* setup back pointer */
 471         be->blkif->be = be;
 472
 473         err = xenbus_watch_pathfmt(dev, &be->backend_watch, backend_changed,
 474                                    "%s/%s", dev->nodename, "physical-device");
 475         if (err)
 476                 goto fail;
 477
 478         err = xenbus_switch_state(dev, XenbusStateInitWait);
 479         if (err)
 480                 goto fail;
 481
 482         return 0;
 483
 484 fail:
 485         DPRINTK("failed");
 486         xen_blkbk_remove(dev);
 487         return err;
 488 }
 489
 490
 491 /*
 492  * Callback received when the hotplug scripts have placed the physical-device
 493  * node.  Read it and the mode node, and create a vbd.  If the frontend is
 494  * ready, connect.
 495  */
 496 static void backend_changed(struct xenbus_watch *watch,
 497                             const char **vec, unsigned int len)
 498 {
 499         int err;
 500         unsigned major;
 501         unsigned minor;
 502         struct backend_info *be
 503                 = container_of(watch, struct backend_info, backend_watch);
 504         struct xenbus_device *dev = be->dev;
 505         int cdrom = 0;
 506         unsigned long handle;
 507         char *device_type;
 508
 509         DPRINTK("");
 510
 511         err = xenbus_scanf(XBT_NIL, dev->nodename, "physical-device", "%x:%x",
 512                            &major, &minor);
 513         if (XENBUS_EXIST_ERR(err)) {
 514                 /*
 515                  * Since this watch will fire once immediately after it is
 516                  * registered, we expect this.  Ignore it, and wait for the
 517                  * hotplug scripts.
 518                  */
 519                 return;
 520         }
 521         if (err != 2) {
 522                 xenbus_dev_fatal(dev, err, "reading physical-device");
 523                 return;
 524         }
 525
 526         if (be->major | be->minor) {
 527                 if (be->major != major || be->minor != minor)
 528                         pr_warn(DRV_PFX "changing physical device (from %x:%x to %x:%x) not supported.\n",
 529                                 be->major, be->minor, major, minor);
 530                 return;
 531         }
 532
 533         be->mode = xenbus_read(XBT_NIL, dev->nodename, "mode", NULL);
 534         if (IS_ERR(be->mode)) {
 535                 err = PTR_ERR(be->mode);
 536                 be->mode = NULL;
 537                 xenbus_dev_fatal(dev, err, "reading mode");
 538                 return;
 539         }
 540
 541         device_type = xenbus_read(XBT_NIL, dev->otherend, "device-type", NULL);
 542         if (!IS_ERR(device_type)) {
 543                 cdrom = strcmp(device_type, "cdrom") == 0;
 544                 kfree(device_type);
 545         }
 546
 547         /* Front end dir is a number, which is used as the handle. */
 548         err = strict_strtoul(strrchr(dev->otherend, '/') + 1, 0, &handle);
 549         if (err)
 550                 return;
 551
 552         be->major = major;
 553         be->minor = minor;
 554
 555         err = xen_vbd_create(be->blkif, handle, major, minor,
 556                              !strchr(be->mode, 'w'), cdrom);
 557
 558         if (err)
 559                 xenbus_dev_fatal(dev, err, "creating vbd structure");
 560         else {
 561                 err = xenvbd_sysfs_addif(dev);
 562                 if (err) {
 563                         xen_vbd_free(&be->blkif->vbd);
 564                         xenbus_dev_fatal(dev, err, "creating sysfs entries");
 565                 }
 566         }
 567
 568         if (err) {
 569                 kfree(be->mode);
 570                 be->mode = NULL;
 571                 be->major = 0;
 572                 be->minor = 0;
 573         } else {
 574                 /* We're potentially connected now */
 575                 xen_update_blkif_status(be->blkif);
 576         }
 577 }
 578
 579
 580 /*
 581  * Callback received when the frontend's state changes.
 582  */
 583 static void frontend_changed(struct xenbus_device *dev,
 584                              enum xenbus_state frontend_state)
 585 {
 586         struct backend_info *be = dev_get_drvdata(&dev->dev);
 587         int err;
 588
 589         DPRINTK("%s", xenbus_strstate(frontend_state));
 590
 591         switch (frontend_state) {
 592         case XenbusStateInitialising:
 593                 if (dev->state == XenbusStateClosed) {
 594                         pr_info(DRV_PFX "%s: prepare for reconnect\n",
 595                                 dev->nodename);
 596                         xenbus_switch_state(dev, XenbusStateInitWait);
 597                 }
 598                 break;
 599
 600         case XenbusStateInitialised:
 601         case XenbusStateConnected:
 602                 /*
 603                  * Ensure we connect even when two watches fire in
 604                  * close succession and we miss the intermediate value
 605                  * of frontend_state.
 606                  */
 607                 if (dev->state == XenbusStateConnected)
 608                         break;
 609
 610                 /*
 611                  * Enforce precondition before potential leak point.
 612                  * xen_blkif_disconnect() is idempotent.
 613                  */
 614                 xen_blkif_disconnect(be->blkif);
 615
 616                 err = connect_ring(be);
 617                 if (err)
 618                         break;
 619                 xen_update_blkif_status(be->blkif);
 620                 break;
 621
 622         case XenbusStateClosing:
 623                 xenbus_switch_state(dev, XenbusStateClosing);
 624                 break;
 625
 626         case XenbusStateClosed:
 627                 xen_blkif_disconnect(be->blkif);
 628                 xenbus_switch_state(dev, XenbusStateClosed);
 629                 if (xenbus_dev_is_online(dev))
 630                         break;
 631                 /* fall through if not online */
 632         case XenbusStateUnknown:
 633                 /* implies xen_blkif_disconnect() via xen_blkbk_remove() */
 634                 device_unregister(&dev->dev);
 635                 break;
 636
 637         default:
 638                 xenbus_dev_fatal(dev, -EINVAL, "saw state %d at frontend",
 639                                  frontend_state);
 640                 break;
 641         }
 642 }
 643
 644
 645 /* ** Connection ** */
 646
 647
 648 /*
 649  * Write the physical details regarding the block device to the store, and
 650  * switch to Connected state.
 651  */
 652 static void connect(struct backend_info *be)
 653 {
 654         struct xenbus_transaction xbt;
 655         int err;
 656         struct xenbus_device *dev = be->dev;
 657
 658         DPRINTK("%s", dev->otherend);
 659
 660         /* Supply the information about the device the frontend needs */
 661 again:
 662         err = xenbus_transaction_start(&xbt);
 663         if (err) {
 664                 xenbus_dev_fatal(dev, err, "starting transaction");
 665                 return;
 666         }
 667
 668         /* If we can't advertise it is OK. */
 669         xen_blkbk_flush_diskcache(xbt, be, be->blkif->vbd.flush_support);
 670
 671         xen_blkbk_discard(xbt, be);
 672
 673         xen_blkbk_barrier(xbt, be, be->blkif->vbd.flush_support);
 674
 675         err = xenbus_printf(xbt, dev->nodename, "feature-persistent", "%u", 1);
 676         if (err) {
 677                 xenbus_dev_fatal(dev, err, "writing %s/feature-persistent",
 678                                  dev->nodename);
 679                 goto abort;
 680         }
 681
 682         err = xenbus_printf(xbt, dev->nodename, "sectors", "%llu",
 683                             (unsigned long long)vbd_sz(&be->blkif->vbd));
 684         if (err) {
 685                 xenbus_dev_fatal(dev, err, "writing %s/sectors",
 686                                  dev->nodename);
 687                 goto abort;
 688         }
 689
 690         /* FIXME: use a typename instead */
 691         err = xenbus_printf(xbt, dev->nodename, "info", "%u",
 692                             be->blkif->vbd.type |
 693                             (be->blkif->vbd.readonly ? VDISK_READONLY : 0));
 694         if (err) {
 695                 xenbus_dev_fatal(dev, err, "writing %s/info",
 696                                  dev->nodename);
 697                 goto abort;
 698         }
 699         err = xenbus_printf(xbt, dev->nodename, "sector-size", "%lu",
 700                             (unsigned long)
 701                             bdev_logical_block_size(be->blkif->vbd.bdev));
 702         if (err) {
 703                 xenbus_dev_fatal(dev, err, "writing %s/sector-size",
 704                                  dev->nodename);
 705                 goto abort;
 706         }
 707
 708         err = xenbus_transaction_end(xbt, 0);
 709         if (err == -EAGAIN)
 710                 goto again;
 711         if (err)
 712                 xenbus_dev_fatal(dev, err, "ending transaction");
 713
 714         err = xenbus_switch_state(dev, XenbusStateConnected);
 715         if (err)
 716                 xenbus_dev_fatal(dev, err, "%s: switching to Connected state",
 717                                  dev->nodename);
 718
 719         return;
 720  abort:
 721         xenbus_transaction_end(xbt, 1);
 722 }
 723
 724
 725 static int connect_ring(struct backend_info *be)
 726 {
 727         struct xenbus_device *dev = be->dev;
 728         unsigned long ring_ref;
 729         unsigned int evtchn;
 730         unsigned int pers_grants;
 731         char protocol[64] = "";
 732         int err;
 733
 734         DPRINTK("%s", dev->otherend);
 735
 736         err = xenbus_gather(XBT_NIL, dev->otherend, "ring-ref", "%lu",
 737                             &ring_ref, "event-channel", "%u", &evtchn, NULL);
 738         if (err) {
 739                 xenbus_dev_fatal(dev, err,
 740                                  "reading %s/ring-ref and event-channel",
 741                                  dev->otherend);
 742                 return err;
 743         }
 744
 745         be->blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
 746         err = xenbus_gather(XBT_NIL, dev->otherend, "protocol",
 747                             "%63s", protocol, NULL);
 748         if (err)
 749                 strcpy(protocol, "unspecified, assuming native");
 750         else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_NATIVE))
 751                 be->blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
 752         else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_32))
 753                 be->blkif->blk_protocol = BLKIF_PROTOCOL_X86_32;
 754         else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_64))
 755                 be->blkif->blk_protocol = BLKIF_PROTOCOL_X86_64;
 756         else {
 757                 xenbus_dev_fatal(dev, err, "unknown fe protocol %s", protocol);
 758                 return -1;
 759         }
 760         err = xenbus_gather(XBT_NIL, dev->otherend,
 761                             "feature-persistent", "%u",
 762                             &pers_grants, NULL);
 763         if (err)
 764                 pers_grants = 0;
 765
 766         be->blkif->vbd.feature_gnt_persistent = pers_grants;
 767         be->blkif->vbd.overflow_max_grants = 0;
 768
 769         pr_info(DRV_PFX "ring-ref %ld, event-channel %d, protocol %d (%s) %s\n",
 770                 ring_ref, evtchn, be->blkif->blk_protocol, protocol,
 771                 pers_grants ? "persistent grants" : "");
 772
 773         /* Map the shared frame, irq etc. */
 774         err = xen_blkif_map(be->blkif, ring_ref, evtchn);
 775         if (err) {
 776                 xenbus_dev_fatal(dev, err, "mapping ring-ref %lu port %u",
 777                                  ring_ref, evtchn);
 778                 return err;
 779         }
 780
 781         return 0;
 782 }
 783
 784
 785 /* ** Driver Registration ** */
 786
 787
 788 static const struct xenbus_device_id xen_blkbk_ids[] = {
 789         { "vbd" },
 790         { "" }
 791 };
 792
 793
 794 static DEFINE_XENBUS_DRIVER(xen_blkbk, ,
 795         .probe = xen_blkbk_probe,
 796         .remove = xen_blkbk_remove,
 797         .otherend_changed = frontend_changed
 798 );
 799
 800
 801 int xen_blkif_xenbus_init(void)
 802 {
 803         return xenbus_register_backend(&xen_blkbk_driver);
 804 }