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         init_completion(&blkif->drain_complete);
 118         atomic_set(&blkif->drain, 0);
 119         blkif->st_print = jiffies;
 120         init_waitqueue_head(&blkif->waiting_to_free);
 121         init_waitqueue_head(&blkif->shutdown_wq);
 122
 123         return blkif;
 124 }
 125
 126 static int xen_blkif_map(struct xen_blkif *blkif, unsigned long shared_page,
 127                          unsigned int evtchn)
 128 {
 129         int err;
 130
 131         /* Already connected through? */
 132         if (blkif->irq)
 133                 return 0;
 134
 135         err = xenbus_map_ring_valloc(blkif->be->dev, shared_page, &blkif->blk_ring);
 136         if (err < 0)
 137                 return err;
 138
 139         switch (blkif->blk_protocol) {
 140         case BLKIF_PROTOCOL_NATIVE:
 141         {
 142                 struct blkif_sring *sring;
 143                 sring = (struct blkif_sring *)blkif->blk_ring;
 144                 BACK_RING_INIT(&blkif->blk_rings.native, sring, PAGE_SIZE);
 145                 break;
 146         }
 147         case BLKIF_PROTOCOL_X86_32:
 148         {
 149                 struct blkif_x86_32_sring *sring_x86_32;
 150                 sring_x86_32 = (struct blkif_x86_32_sring *)blkif->blk_ring;
 151                 BACK_RING_INIT(&blkif->blk_rings.x86_32, sring_x86_32, PAGE_SIZE);
 152                 break;
 153         }
 154         case BLKIF_PROTOCOL_X86_64:
 155         {
 156                 struct blkif_x86_64_sring *sring_x86_64;
 157                 sring_x86_64 = (struct blkif_x86_64_sring *)blkif->blk_ring;
 158                 BACK_RING_INIT(&blkif->blk_rings.x86_64, sring_x86_64, PAGE_SIZE);
 159                 break;
 160         }
 161         default:
 162                 BUG();
 163         }
 164
 165         err = bind_interdomain_evtchn_to_irqhandler(blkif->domid, evtchn,
 166                                                     xen_blkif_be_int, 0,
 167                                                     "blkif-backend", blkif);
 168         if (err < 0) {
 169                 xenbus_unmap_ring_vfree(blkif->be->dev, blkif->blk_ring);
 170                 blkif->blk_rings.common.sring = NULL;
 171                 return err;
 172         }
 173         blkif->irq = err;
 174
 175         return 0;
 176 }
 177
 178 static void xen_blkif_disconnect(struct xen_blkif *blkif)
 179 {
 180         if (blkif->xenblkd) {
 181                 kthread_stop(blkif->xenblkd);
 182                 wake_up(&blkif->shutdown_wq);
 183                 blkif->xenblkd = NULL;
 184         }
 185
 186         atomic_dec(&blkif->refcnt);
 187         wait_event(blkif->waiting_to_free, atomic_read(&blkif->refcnt) == 0);
 188         atomic_inc(&blkif->refcnt);
 189
 190         if (blkif->irq) {
 191                 unbind_from_irqhandler(blkif->irq, blkif);
 192                 blkif->irq = 0;
 193         }
 194
 195         if (blkif->blk_rings.common.sring) {
 196                 xenbus_unmap_ring_vfree(blkif->be->dev, blkif->blk_ring);
 197                 blkif->blk_rings.common.sring = NULL;
 198         }
 199 }
 200
 201 void xen_blkif_free(struct xen_blkif *blkif)
 202 {
 203         if (!atomic_dec_and_test(&blkif->refcnt))
 204                 BUG();
 205         kmem_cache_free(xen_blkif_cachep, blkif);
 206 }
 207
 208 int __init xen_blkif_interface_init(void)
 209 {
 210         xen_blkif_cachep = kmem_cache_create("blkif_cache",
 211                                              sizeof(struct xen_blkif),
 212                                              0, 0, NULL);
 213         if (!xen_blkif_cachep)
 214                 return -ENOMEM;
 215
 216         return 0;
 217 }
 218
 219 /*
 220  *  sysfs interface for VBD I/O requests
 221  */
 222
 223 #define VBD_SHOW(name, format, args...)                                 \
 224         static ssize_t show_##name(struct device *_dev,                 \
 225                                    struct device_attribute *attr,       \
 226                                    char *buf)                           \
 227         {                                                               \
 228                 struct xenbus_device *dev = to_xenbus_device(_dev);     \
 229                 struct backend_info *be = dev_get_drvdata(&dev->dev);   \
 230                                                                         \
 231                 return sprintf(buf, format, ##args);                    \
 232         }                                                               \
 233         static DEVICE_ATTR(name, S_IRUGO, show_##name, NULL)
 234
 235 VBD_SHOW(oo_req,  "%d\n", be->blkif->st_oo_req);
 236 VBD_SHOW(rd_req,  "%d\n", be->blkif->st_rd_req);
 237 VBD_SHOW(wr_req,  "%d\n", be->blkif->st_wr_req);
 238 VBD_SHOW(f_req,  "%d\n", be->blkif->st_f_req);
 239 VBD_SHOW(ds_req,  "%d\n", be->blkif->st_ds_req);
 240 VBD_SHOW(rd_sect, "%d\n", be->blkif->st_rd_sect);
 241 VBD_SHOW(wr_sect, "%d\n", be->blkif->st_wr_sect);
 242
 243 static struct attribute *xen_vbdstat_attrs[] = {
 244         &dev_attr_oo_req.attr,
 245         &dev_attr_rd_req.attr,
 246         &dev_attr_wr_req.attr,
 247         &dev_attr_f_req.attr,
 248         &dev_attr_ds_req.attr,
 249         &dev_attr_rd_sect.attr,
 250         &dev_attr_wr_sect.attr,
 251         NULL
 252 };
 253
 254 static struct attribute_group xen_vbdstat_group = {
 255         .name = "statistics",
 256         .attrs = xen_vbdstat_attrs,
 257 };
 258
 259 VBD_SHOW(physical_device, "%x:%x\n", be->major, be->minor);
 260 VBD_SHOW(mode, "%s\n", be->mode);
 261
 262 int xenvbd_sysfs_addif(struct xenbus_device *dev)
 263 {
 264         int error;
 265
 266         error = device_create_file(&dev->dev, &dev_attr_physical_device);
 267         if (error)
 268                 goto fail1;
 269
 270         error = device_create_file(&dev->dev, &dev_attr_mode);
 271         if (error)
 272                 goto fail2;
 273
 274         error = sysfs_create_group(&dev->dev.kobj, &xen_vbdstat_group);
 275         if (error)
 276                 goto fail3;
 277
 278         return 0;
 279
 280 fail3:  sysfs_remove_group(&dev->dev.kobj, &xen_vbdstat_group);
 281 fail2:  device_remove_file(&dev->dev, &dev_attr_mode);
 282 fail1:  device_remove_file(&dev->dev, &dev_attr_physical_device);
 283         return error;
 284 }
 285
 286 void xenvbd_sysfs_delif(struct xenbus_device *dev)
 287 {
 288         sysfs_remove_group(&dev->dev.kobj, &xen_vbdstat_group);
 289         device_remove_file(&dev->dev, &dev_attr_mode);
 290         device_remove_file(&dev->dev, &dev_attr_physical_device);
 291 }
 292
 293
 294 static void xen_vbd_free(struct xen_vbd *vbd)
 295 {
 296         if (vbd->bdev)
 297                 blkdev_put(vbd->bdev, vbd->readonly ? FMODE_READ : FMODE_WRITE);
 298         vbd->bdev = NULL;
 299 }
 300
 301 static int xen_vbd_create(struct xen_blkif *blkif, blkif_vdev_t handle,
 302                           unsigned major, unsigned minor, int readonly,
 303                           int cdrom)
 304 {
 305         struct xen_vbd *vbd;
 306         struct block_device *bdev;
 307         struct request_queue *q;
 308
 309         vbd = &blkif->vbd;
 310         vbd->handle   = handle;
 311         vbd->readonly = readonly;
 312         vbd->type     = 0;
 313
 314         vbd->pdevice  = MKDEV(major, minor);
 315
 316         bdev = blkdev_get_by_dev(vbd->pdevice, vbd->readonly ?
 317                                  FMODE_READ : FMODE_WRITE, NULL);
 318
 319         if (IS_ERR(bdev)) {
 320                 DPRINTK("xen_vbd_create: device %08x could not be opened.\n",
 321                         vbd->pdevice);
 322                 return -ENOENT;
 323         }
 324
 325         vbd->bdev = bdev;
 326         if (vbd->bdev->bd_disk == NULL) {
 327                 DPRINTK("xen_vbd_create: device %08x doesn't exist.\n",
 328                         vbd->pdevice);
 329                 xen_vbd_free(vbd);
 330                 return -ENOENT;
 331         }
 332         vbd->size = vbd_sz(vbd);
 333
 334         if (vbd->bdev->bd_disk->flags & GENHD_FL_CD || cdrom)
 335                 vbd->type |= VDISK_CDROM;
 336         if (vbd->bdev->bd_disk->flags & GENHD_FL_REMOVABLE)
 337                 vbd->type |= VDISK_REMOVABLE;
 338
 339         q = bdev_get_queue(bdev);
 340         if (q && q->flush_flags)
 341                 vbd->flush_support = true;
 342
 343         DPRINTK("Successful creation of handle=%04x (dom=%u)\n",
 344                 handle, blkif->domid);
 345         return 0;
 346 }
 347 static int xen_blkbk_remove(struct xenbus_device *dev)
 348 {
 349         struct backend_info *be = dev_get_drvdata(&dev->dev);
 350
 351         DPRINTK("");
 352
 353         if (be->major || be->minor)
 354                 xenvbd_sysfs_delif(dev);
 355
 356         if (be->backend_watch.node) {
 357                 unregister_xenbus_watch(&be->backend_watch);
 358                 kfree(be->backend_watch.node);
 359                 be->backend_watch.node = NULL;
 360         }
 361
 362         if (be->blkif) {
 363                 xen_blkif_disconnect(be->blkif);
 364                 xen_vbd_free(&be->blkif->vbd);
 365                 xen_blkif_free(be->blkif);
 366                 be->blkif = NULL;
 367         }
 368
 369         kfree(be->mode);
 370         kfree(be);
 371         dev_set_drvdata(&dev->dev, NULL);
 372         return 0;
 373 }
 374
 375 int xen_blkbk_flush_diskcache(struct xenbus_transaction xbt,
 376                               struct backend_info *be, int state)
 377 {
 378         struct xenbus_device *dev = be->dev;
 379         int err;
 380
 381         err = xenbus_printf(xbt, dev->nodename, "feature-flush-cache",
 382                             "%d", state);
 383         if (err)
 384                 xenbus_dev_fatal(dev, err, "writing feature-flush-cache");
 385
 386         return err;
 387 }
 388
 389 int xen_blkbk_discard(struct xenbus_transaction xbt, struct backend_info *be)
 390 {
 391         struct xenbus_device *dev = be->dev;
 392         struct xen_blkif *blkif = be->blkif;
 393         char *type;
 394         int err;
 395         int state = 0;
 396
 397         type = xenbus_read(XBT_NIL, dev->nodename, "type", NULL);
 398         if (!IS_ERR(type)) {
 399                 if (strncmp(type, "file", 4) == 0) {
 400                         state = 1;
 401                         blkif->blk_backend_type = BLKIF_BACKEND_FILE;
 402                 }
 403                 if (strncmp(type, "phy", 3) == 0) {
 404                         struct block_device *bdev = be->blkif->vbd.bdev;
 405                         struct request_queue *q = bdev_get_queue(bdev);
 406                         if (blk_queue_discard(q)) {
 407                                 err = xenbus_printf(xbt, dev->nodename,
 408                                         "discard-granularity", "%u",
 409                                         q->limits.discard_granularity);
 410                                 if (err) {
 411                                         xenbus_dev_fatal(dev, err,
 412                                                 "writing discard-granularity");
 413                                         goto kfree;
 414                                 }
 415                                 err = xenbus_printf(xbt, dev->nodename,
 416                                         "discard-alignment", "%u",
 417                                         q->limits.discard_alignment);
 418                                 if (err) {
 419                                         xenbus_dev_fatal(dev, err,
 420                                                 "writing discard-alignment");
 421                                         goto kfree;
 422                                 }
 423                                 state = 1;
 424                                 blkif->blk_backend_type = BLKIF_BACKEND_PHY;
 425                         }
 426                 }
 427         } else {
 428                 err = PTR_ERR(type);
 429                 xenbus_dev_fatal(dev, err, "reading type");
 430                 goto out;
 431         }
 432
 433         err = xenbus_printf(xbt, dev->nodename, "feature-discard",
 434                             "%d", state);
 435         if (err)
 436                 xenbus_dev_fatal(dev, err, "writing feature-discard");
 437 kfree:
 438         kfree(type);
 439 out:
 440         return err;
 441 }
 442 int xen_blkbk_barrier(struct xenbus_transaction xbt,
 443                       struct backend_info *be, int state)
 444 {
 445         struct xenbus_device *dev = be->dev;
 446         int err;
 447
 448         err = xenbus_printf(xbt, dev->nodename, "feature-barrier",
 449                             "%d", state);
 450         if (err)
 451                 xenbus_dev_fatal(dev, err, "writing feature-barrier");
 452
 453         return err;
 454 }
 455
 456 /*
 457  * Entry point to this code when a new device is created.  Allocate the basic
 458  * structures, and watch the store waiting for the hotplug scripts to tell us
 459  * the device's physical major and minor numbers.  Switch to InitWait.
 460  */
 461 static int xen_blkbk_probe(struct xenbus_device *dev,
 462                            const struct xenbus_device_id *id)
 463 {
 464         int err;
 465         struct backend_info *be = kzalloc(sizeof(struct backend_info),
 466                                           GFP_KERNEL);
 467         if (!be) {
 468                 xenbus_dev_fatal(dev, -ENOMEM,
 469                                  "allocating backend structure");
 470                 return -ENOMEM;
 471         }
 472         be->dev = dev;
 473         dev_set_drvdata(&dev->dev, be);
 474
 475         be->blkif = xen_blkif_alloc(dev->otherend_id);
 476         if (IS_ERR(be->blkif)) {
 477                 err = PTR_ERR(be->blkif);
 478                 be->blkif = NULL;
 479                 xenbus_dev_fatal(dev, err, "creating block interface");
 480                 goto fail;
 481         }
 482
 483         /* setup back pointer */
 484         be->blkif->be = be;
 485
 486         err = xenbus_watch_pathfmt(dev, &be->backend_watch, backend_changed,
 487                                    "%s/%s", dev->nodename, "physical-device");
 488         if (err)
 489                 goto fail;
 490
 491         err = xenbus_switch_state(dev, XenbusStateInitWait);
 492         if (err)
 493                 goto fail;
 494
 495         return 0;
 496
 497 fail:
 498         DPRINTK("failed");
 499         xen_blkbk_remove(dev);
 500         return err;
 501 }
 502
 503
 504 /*
 505  * Callback received when the hotplug scripts have placed the physical-device
 506  * node.  Read it and the mode node, and create a vbd.  If the frontend is
 507  * ready, connect.
 508  */
 509 static void backend_changed(struct xenbus_watch *watch,
 510                             const char **vec, unsigned int len)
 511 {
 512         int err;
 513         unsigned major;
 514         unsigned minor;
 515         struct backend_info *be
 516                 = container_of(watch, struct backend_info, backend_watch);
 517         struct xenbus_device *dev = be->dev;
 518         int cdrom = 0;
 519         unsigned long handle;
 520         char *device_type;
 521
 522         DPRINTK("");
 523
 524         err = xenbus_scanf(XBT_NIL, dev->nodename, "physical-device", "%x:%x",
 525                            &major, &minor);
 526         if (XENBUS_EXIST_ERR(err)) {
 527                 /*
 528                  * Since this watch will fire once immediately after it is
 529                  * registered, we expect this.  Ignore it, and wait for the
 530                  * hotplug scripts.
 531                  */
 532                 return;
 533         }
 534         if (err != 2) {
 535                 xenbus_dev_fatal(dev, err, "reading physical-device");
 536                 return;
 537         }
 538
 539         if (be->major | be->minor) {
 540                 if (be->major != major || be->minor != minor)
 541                         pr_warn(DRV_PFX "changing physical device (from %x:%x to %x:%x) not supported.\n",
 542                                 be->major, be->minor, major, minor);
 543                 return;
 544         }
 545
 546         be->mode = xenbus_read(XBT_NIL, dev->nodename, "mode", NULL);
 547         if (IS_ERR(be->mode)) {
 548                 err = PTR_ERR(be->mode);
 549                 be->mode = NULL;
 550                 xenbus_dev_fatal(dev, err, "reading mode");
 551                 return;
 552         }
 553
 554         device_type = xenbus_read(XBT_NIL, dev->otherend, "device-type", NULL);
 555         if (!IS_ERR(device_type)) {
 556                 cdrom = strcmp(device_type, "cdrom") == 0;
 557                 kfree(device_type);
 558         }
 559
 560         /* Front end dir is a number, which is used as the handle. */
 561         err = strict_strtoul(strrchr(dev->otherend, '/') + 1, 0, &handle);
 562         if (err)
 563                 return;
 564
 565         be->major = major;
 566         be->minor = minor;
 567
 568         err = xen_vbd_create(be->blkif, handle, major, minor,
 569                              !strchr(be->mode, 'w'), cdrom);
 570
 571         if (err)
 572                 xenbus_dev_fatal(dev, err, "creating vbd structure");
 573         else {
 574                 err = xenvbd_sysfs_addif(dev);
 575                 if (err) {
 576                         xen_vbd_free(&be->blkif->vbd);
 577                         xenbus_dev_fatal(dev, err, "creating sysfs entries");
 578                 }
 579         }
 580
 581         if (err) {
 582                 kfree(be->mode);
 583                 be->mode = NULL;
 584                 be->major = 0;
 585                 be->minor = 0;
 586         } else {
 587                 /* We're potentially connected now */
 588                 xen_update_blkif_status(be->blkif);
 589         }
 590 }
 591
 592
 593 /*
 594  * Callback received when the frontend's state changes.
 595  */
 596 static void frontend_changed(struct xenbus_device *dev,
 597                              enum xenbus_state frontend_state)
 598 {
 599         struct backend_info *be = dev_get_drvdata(&dev->dev);
 600         int err;
 601
 602         DPRINTK("%s", xenbus_strstate(frontend_state));
 603
 604         switch (frontend_state) {
 605         case XenbusStateInitialising:
 606                 if (dev->state == XenbusStateClosed) {
 607                         pr_info(DRV_PFX "%s: prepare for reconnect\n",
 608                                 dev->nodename);
 609                         xenbus_switch_state(dev, XenbusStateInitWait);
 610                 }
 611                 break;
 612
 613         case XenbusStateInitialised:
 614         case XenbusStateConnected:
 615                 /*
 616                  * Ensure we connect even when two watches fire in
 617                  * close successsion and we miss the intermediate value
 618                  * of frontend_state.
 619                  */
 620                 if (dev->state == XenbusStateConnected)
 621                         break;
 622
 623                 /*
 624                  * Enforce precondition before potential leak point.
 625                  * xen_blkif_disconnect() is idempotent.
 626                  */
 627                 xen_blkif_disconnect(be->blkif);
 628
 629                 err = connect_ring(be);
 630                 if (err)
 631                         break;
 632                 xen_update_blkif_status(be->blkif);
 633                 break;
 634
 635         case XenbusStateClosing:
 636                 xenbus_switch_state(dev, XenbusStateClosing);
 637                 break;
 638
 639         case XenbusStateClosed:
 640                 xen_blkif_disconnect(be->blkif);
 641                 xenbus_switch_state(dev, XenbusStateClosed);
 642                 if (xenbus_dev_is_online(dev))
 643                         break;
 644                 /* fall through if not online */
 645         case XenbusStateUnknown:
 646                 /* implies xen_blkif_disconnect() via xen_blkbk_remove() */
 647                 device_unregister(&dev->dev);
 648                 break;
 649
 650         default:
 651                 xenbus_dev_fatal(dev, -EINVAL, "saw state %d at frontend",
 652                                  frontend_state);
 653                 break;
 654         }
 655 }
 656
 657
 658 /* ** Connection ** */
 659
 660
 661 /*
 662  * Write the physical details regarding the block device to the store, and
 663  * switch to Connected state.
 664  */
 665 static void connect(struct backend_info *be)
 666 {
 667         struct xenbus_transaction xbt;
 668         int err;
 669         struct xenbus_device *dev = be->dev;
 670
 671         DPRINTK("%s", dev->otherend);
 672
 673         /* Supply the information about the device the frontend needs */
 674 again:
 675         err = xenbus_transaction_start(&xbt);
 676         if (err) {
 677                 xenbus_dev_fatal(dev, err, "starting transaction");
 678                 return;
 679         }
 680
 681         err = xen_blkbk_flush_diskcache(xbt, be, be->blkif->vbd.flush_support);
 682         if (err)
 683                 goto abort;
 684
 685         err = xen_blkbk_discard(xbt, be);
 686
 687         /* If we can't advertise it is OK. */
 688         err = xen_blkbk_barrier(xbt, be, be->blkif->vbd.flush_support);
 689
 690         err = xenbus_printf(xbt, dev->nodename, "sectors", "%llu",
 691                             (unsigned long long)vbd_sz(&be->blkif->vbd));
 692         if (err) {
 693                 xenbus_dev_fatal(dev, err, "writing %s/sectors",
 694                                  dev->nodename);
 695                 goto abort;
 696         }
 697
 698         /* FIXME: use a typename instead */
 699         err = xenbus_printf(xbt, dev->nodename, "info", "%u",
 700                             be->blkif->vbd.type |
 701                             (be->blkif->vbd.readonly ? VDISK_READONLY : 0));
 702         if (err) {
 703                 xenbus_dev_fatal(dev, err, "writing %s/info",
 704                                  dev->nodename);
 705                 goto abort;
 706         }
 707         err = xenbus_printf(xbt, dev->nodename, "sector-size", "%lu",
 708                             (unsigned long)
 709                             bdev_logical_block_size(be->blkif->vbd.bdev));
 710         if (err) {
 711                 xenbus_dev_fatal(dev, err, "writing %s/sector-size",
 712                                  dev->nodename);
 713                 goto abort;
 714         }
 715
 716         err = xenbus_transaction_end(xbt, 0);
 717         if (err == -EAGAIN)
 718                 goto again;
 719         if (err)
 720                 xenbus_dev_fatal(dev, err, "ending transaction");
 721
 722         err = xenbus_switch_state(dev, XenbusStateConnected);
 723         if (err)
 724                 xenbus_dev_fatal(dev, err, "%s: switching to Connected state",
 725                                  dev->nodename);
 726
 727         return;
 728  abort:
 729         xenbus_transaction_end(xbt, 1);
 730 }
 731
 732
 733 static int connect_ring(struct backend_info *be)
 734 {
 735         struct xenbus_device *dev = be->dev;
 736         unsigned long ring_ref;
 737         unsigned int evtchn;
 738         char protocol[64] = "";
 739         int err;
 740
 741         DPRINTK("%s", dev->otherend);
 742
 743         err = xenbus_gather(XBT_NIL, dev->otherend, "ring-ref", "%lu",
 744                             &ring_ref, "event-channel", "%u", &evtchn, NULL);
 745         if (err) {
 746                 xenbus_dev_fatal(dev, err,
 747                                  "reading %s/ring-ref and event-channel",
 748                                  dev->otherend);
 749                 return err;
 750         }
 751
 752         be->blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
 753         err = xenbus_gather(XBT_NIL, dev->otherend, "protocol",
 754                             "%63s", protocol, NULL);
 755         if (err)
 756                 strcpy(protocol, "unspecified, assuming native");
 757         else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_NATIVE))
 758                 be->blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
 759         else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_32))
 760                 be->blkif->blk_protocol = BLKIF_PROTOCOL_X86_32;
 761         else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_64))
 762                 be->blkif->blk_protocol = BLKIF_PROTOCOL_X86_64;
 763         else {
 764                 xenbus_dev_fatal(dev, err, "unknown fe protocol %s", protocol);
 765                 return -1;
 766         }
 767         pr_info(DRV_PFX "ring-ref %ld, event-channel %d, protocol %d (%s)\n",
 768                 ring_ref, evtchn, be->blkif->blk_protocol, protocol);
 769
 770         /* Map the shared frame, irq etc. */
 771         err = xen_blkif_map(be->blkif, ring_ref, evtchn);
 772         if (err) {
 773                 xenbus_dev_fatal(dev, err, "mapping ring-ref %lu port %u",
 774                                  ring_ref, evtchn);
 775                 return err;
 776         }
 777
 778         return 0;
 779 }
 780
 781
 782 /* ** Driver Registration ** */
 783
 784
 785 static const struct xenbus_device_id xen_blkbk_ids[] = {
 786         { "vbd" },
 787         { "" }
 788 };
 789
 790
 791 static struct xenbus_driver xen_blkbk = {
 792         .name = "vbd",
 793         .owner = THIS_MODULE,
 794         .ids = xen_blkbk_ids,
 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);
 804 }