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, "%s", 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                 return;
 102         }
 103 }
 104
 105 static struct xen_blkif *xen_blkif_alloc(domid_t domid)
 106 {
 107         struct xen_blkif *blkif;
 108         struct pending_req *req, *n;
 109         int i, j;
 110
 111         BUILD_BUG_ON(MAX_INDIRECT_PAGES > BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST);
 112
 113         blkif = kmem_cache_zalloc(xen_blkif_cachep, GFP_KERNEL);
 114         if (!blkif)
 115                 return ERR_PTR(-ENOMEM);
 116
 117         blkif->domid = domid;
 118         spin_lock_init(&blkif->blk_ring_lock);
 119         atomic_set(&blkif->refcnt, 1);
 120         init_waitqueue_head(&blkif->wq);
 121         init_completion(&blkif->drain_complete);
 122         atomic_set(&blkif->drain, 0);
 123         blkif->st_print = jiffies;
 124         init_waitqueue_head(&blkif->waiting_to_free);
 125         blkif->persistent_gnts.rb_node = NULL;
 126         spin_lock_init(&blkif->free_pages_lock);
 127         INIT_LIST_HEAD(&blkif->free_pages);
 128         blkif->free_pages_num = 0;
 129         atomic_set(&blkif->persistent_gnt_in_use, 0);
 130
 131         INIT_LIST_HEAD(&blkif->pending_free);
 132
 133         for (i = 0; i < XEN_BLKIF_REQS; i++) {
 134                 req = kzalloc(sizeof(*req), GFP_KERNEL);
 135                 if (!req)
 136                         goto fail;
 137                 list_add_tail(&req->free_list,
 138                               &blkif->pending_free);
 139                 for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++) {
 140                         req->segments[j] = kzalloc(sizeof(*req->segments[0]),
 141                                                    GFP_KERNEL);
 142                         if (!req->segments[j])
 143                                 goto fail;
 144                 }
 145                 for (j = 0; j < MAX_INDIRECT_PAGES; j++) {
 146                         req->indirect_pages[j] = kzalloc(sizeof(*req->indirect_pages[0]),
 147                                                          GFP_KERNEL);
 148                         if (!req->indirect_pages[j])
 149                                 goto fail;
 150                 }
 151         }
 152         spin_lock_init(&blkif->pending_free_lock);
 153         init_waitqueue_head(&blkif->pending_free_wq);
 154         init_waitqueue_head(&blkif->shutdown_wq);
 155
 156         return blkif;
 157
 158 fail:
 159         list_for_each_entry_safe(req, n, &blkif->pending_free, free_list) {
 160                 list_del(&req->free_list);
 161                 for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++) {
 162                         if (!req->segments[j])
 163                                 break;
 164                         kfree(req->segments[j]);
 165                 }
 166                 for (j = 0; j < MAX_INDIRECT_PAGES; j++) {
 167                         if (!req->indirect_pages[j])
 168                                 break;
 169                         kfree(req->indirect_pages[j]);
 170                 }
 171                 kfree(req);
 172         }
 173
 174         kmem_cache_free(xen_blkif_cachep, blkif);
 175
 176         return ERR_PTR(-ENOMEM);
 177 }
 178
 179 static int xen_blkif_map(struct xen_blkif *blkif, unsigned long shared_page,
 180                          unsigned int evtchn)
 181 {
 182         int err;
 183
 184         /* Already connected through? */
 185         if (blkif->irq)
 186                 return 0;
 187
 188         err = xenbus_map_ring_valloc(blkif->be->dev, shared_page, &blkif->blk_ring);
 189         if (err < 0)
 190                 return err;
 191
 192         switch (blkif->blk_protocol) {
 193         case BLKIF_PROTOCOL_NATIVE:
 194         {
 195                 struct blkif_sring *sring;
 196                 sring = (struct blkif_sring *)blkif->blk_ring;
 197                 BACK_RING_INIT(&blkif->blk_rings.native, sring, PAGE_SIZE);
 198                 break;
 199         }
 200         case BLKIF_PROTOCOL_X86_32:
 201         {
 202                 struct blkif_x86_32_sring *sring_x86_32;
 203                 sring_x86_32 = (struct blkif_x86_32_sring *)blkif->blk_ring;
 204                 BACK_RING_INIT(&blkif->blk_rings.x86_32, sring_x86_32, PAGE_SIZE);
 205                 break;
 206         }
 207         case BLKIF_PROTOCOL_X86_64:
 208         {
 209                 struct blkif_x86_64_sring *sring_x86_64;
 210                 sring_x86_64 = (struct blkif_x86_64_sring *)blkif->blk_ring;
 211                 BACK_RING_INIT(&blkif->blk_rings.x86_64, sring_x86_64, PAGE_SIZE);
 212                 break;
 213         }
 214         default:
 215                 BUG();
 216         }
 217
 218         err = bind_interdomain_evtchn_to_irqhandler(blkif->domid, evtchn,
 219                                                     xen_blkif_be_int, 0,
 220                                                     "blkif-backend", blkif);
 221         if (err < 0) {
 222                 xenbus_unmap_ring_vfree(blkif->be->dev, blkif->blk_ring);
 223                 blkif->blk_rings.common.sring = NULL;
 224                 return err;
 225         }
 226         blkif->irq = err;
 227
 228         return 0;
 229 }
 230
 231 static void xen_blkif_disconnect(struct xen_blkif *blkif)
 232 {
 233         if (blkif->xenblkd) {
 234                 kthread_stop(blkif->xenblkd);
 235                 wake_up(&blkif->shutdown_wq);
 236                 blkif->xenblkd = NULL;
 237         }
 238
 239         atomic_dec(&blkif->refcnt);
 240         wait_event(blkif->waiting_to_free, atomic_read(&blkif->refcnt) == 0);
 241         atomic_inc(&blkif->refcnt);
 242
 243         if (blkif->irq) {
 244                 unbind_from_irqhandler(blkif->irq, blkif);
 245                 blkif->irq = 0;
 246         }
 247
 248         if (blkif->blk_rings.common.sring) {
 249                 xenbus_unmap_ring_vfree(blkif->be->dev, blkif->blk_ring);
 250                 blkif->blk_rings.common.sring = NULL;
 251         }
 252 }
 253
 254 static void xen_blkif_free(struct xen_blkif *blkif)
 255 {
 256         struct pending_req *req, *n;
 257         int i = 0, j;
 258
 259         if (!atomic_dec_and_test(&blkif->refcnt))
 260                 BUG();
 261
 262         /* Check that there is no request in use */
 263         list_for_each_entry_safe(req, n, &blkif->pending_free, free_list) {
 264                 list_del(&req->free_list);
 265
 266                 for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++)
 267                         kfree(req->segments[j]);
 268
 269                 for (j = 0; j < MAX_INDIRECT_PAGES; j++)
 270                         kfree(req->indirect_pages[j]);
 271
 272                 kfree(req);
 273                 i++;
 274         }
 275
 276         WARN_ON(i != XEN_BLKIF_REQS);
 277
 278         kmem_cache_free(xen_blkif_cachep, blkif);
 279 }
 280
 281 int __init xen_blkif_interface_init(void)
 282 {
 283         xen_blkif_cachep = kmem_cache_create("blkif_cache",
 284                                              sizeof(struct xen_blkif),
 285                                              0, 0, NULL);
 286         if (!xen_blkif_cachep)
 287                 return -ENOMEM;
 288
 289         return 0;
 290 }
 291
 292 /*
 293  *  sysfs interface for VBD I/O requests
 294  */
 295
 296 #define VBD_SHOW(name, format, args...)                                 \
 297         static ssize_t show_##name(struct device *_dev,                 \
 298                                    struct device_attribute *attr,       \
 299                                    char *buf)                           \
 300         {                                                               \
 301                 struct xenbus_device *dev = to_xenbus_device(_dev);     \
 302                 struct backend_info *be = dev_get_drvdata(&dev->dev);   \
 303                                                                         \
 304                 return sprintf(buf, format, ##args);                    \
 305         }                                                               \
 306         static DEVICE_ATTR(name, S_IRUGO, show_##name, NULL)
 307
 308 VBD_SHOW(oo_req,  "%llu\n", be->blkif->st_oo_req);
 309 VBD_SHOW(rd_req,  "%llu\n", be->blkif->st_rd_req);
 310 VBD_SHOW(wr_req,  "%llu\n", be->blkif->st_wr_req);
 311 VBD_SHOW(f_req,  "%llu\n", be->blkif->st_f_req);
 312 VBD_SHOW(ds_req,  "%llu\n", be->blkif->st_ds_req);
 313 VBD_SHOW(rd_sect, "%llu\n", be->blkif->st_rd_sect);
 314 VBD_SHOW(wr_sect, "%llu\n", be->blkif->st_wr_sect);
 315
 316 static struct attribute *xen_vbdstat_attrs[] = {
 317         &dev_attr_oo_req.attr,
 318         &dev_attr_rd_req.attr,
 319         &dev_attr_wr_req.attr,
 320         &dev_attr_f_req.attr,
 321         &dev_attr_ds_req.attr,
 322         &dev_attr_rd_sect.attr,
 323         &dev_attr_wr_sect.attr,
 324         NULL
 325 };
 326
 327 static struct attribute_group xen_vbdstat_group = {
 328         .name = "statistics",
 329         .attrs = xen_vbdstat_attrs,
 330 };
 331
 332 VBD_SHOW(physical_device, "%x:%x\n", be->major, be->minor);
 333 VBD_SHOW(mode, "%s\n", be->mode);
 334
 335 static int xenvbd_sysfs_addif(struct xenbus_device *dev)
 336 {
 337         int error;
 338
 339         error = device_create_file(&dev->dev, &dev_attr_physical_device);
 340         if (error)
 341                 goto fail1;
 342
 343         error = device_create_file(&dev->dev, &dev_attr_mode);
 344         if (error)
 345                 goto fail2;
 346
 347         error = sysfs_create_group(&dev->dev.kobj, &xen_vbdstat_group);
 348         if (error)
 349                 goto fail3;
 350
 351         return 0;
 352
 353 fail3:  sysfs_remove_group(&dev->dev.kobj, &xen_vbdstat_group);
 354 fail2:  device_remove_file(&dev->dev, &dev_attr_mode);
 355 fail1:  device_remove_file(&dev->dev, &dev_attr_physical_device);
 356         return error;
 357 }
 358
 359 static void xenvbd_sysfs_delif(struct xenbus_device *dev)
 360 {
 361         sysfs_remove_group(&dev->dev.kobj, &xen_vbdstat_group);
 362         device_remove_file(&dev->dev, &dev_attr_mode);
 363         device_remove_file(&dev->dev, &dev_attr_physical_device);
 364 }
 365
 366
 367 static void xen_vbd_free(struct xen_vbd *vbd)
 368 {
 369         if (vbd->bdev)
 370                 blkdev_put(vbd->bdev, vbd->readonly ? FMODE_READ : FMODE_WRITE);
 371         vbd->bdev = NULL;
 372 }
 373
 374 static int xen_vbd_create(struct xen_blkif *blkif, blkif_vdev_t handle,
 375                           unsigned major, unsigned minor, int readonly,
 376                           int cdrom)
 377 {
 378         struct xen_vbd *vbd;
 379         struct block_device *bdev;
 380         struct request_queue *q;
 381
 382         vbd = &blkif->vbd;
 383         vbd->handle   = handle;
 384         vbd->readonly = readonly;
 385         vbd->type     = 0;
 386
 387         vbd->pdevice  = MKDEV(major, minor);
 388
 389         bdev = blkdev_get_by_dev(vbd->pdevice, vbd->readonly ?
 390                                  FMODE_READ : FMODE_WRITE, NULL);
 391
 392         if (IS_ERR(bdev)) {
 393                 DPRINTK("xen_vbd_create: device %08x could not be opened.\n",
 394                         vbd->pdevice);
 395                 return -ENOENT;
 396         }
 397
 398         vbd->bdev = bdev;
 399         if (vbd->bdev->bd_disk == NULL) {
 400                 DPRINTK("xen_vbd_create: device %08x doesn't exist.\n",
 401                         vbd->pdevice);
 402                 xen_vbd_free(vbd);
 403                 return -ENOENT;
 404         }
 405         vbd->size = vbd_sz(vbd);
 406
 407         if (vbd->bdev->bd_disk->flags & GENHD_FL_CD || cdrom)
 408                 vbd->type |= VDISK_CDROM;
 409         if (vbd->bdev->bd_disk->flags & GENHD_FL_REMOVABLE)
 410                 vbd->type |= VDISK_REMOVABLE;
 411
 412         q = bdev_get_queue(bdev);
 413         if (q && q->flush_flags)
 414                 vbd->flush_support = true;
 415
 416         if (q && blk_queue_secdiscard(q))
 417                 vbd->discard_secure = true;
 418
 419         DPRINTK("Successful creation of handle=%04x (dom=%u)\n",
 420                 handle, blkif->domid);
 421         return 0;
 422 }
 423 static int xen_blkbk_remove(struct xenbus_device *dev)
 424 {
 425         struct backend_info *be = dev_get_drvdata(&dev->dev);
 426
 427         DPRINTK("");
 428
 429         if (be->major || be->minor)
 430                 xenvbd_sysfs_delif(dev);
 431
 432         if (be->backend_watch.node) {
 433                 unregister_xenbus_watch(&be->backend_watch);
 434                 kfree(be->backend_watch.node);
 435                 be->backend_watch.node = NULL;
 436         }
 437
 438         if (be->blkif) {
 439                 xen_blkif_disconnect(be->blkif);
 440                 xen_vbd_free(&be->blkif->vbd);
 441                 xen_blkif_free(be->blkif);
 442                 be->blkif = NULL;
 443         }
 444
 445         kfree(be->mode);
 446         kfree(be);
 447         dev_set_drvdata(&dev->dev, NULL);
 448         return 0;
 449 }
 450
 451 int xen_blkbk_flush_diskcache(struct xenbus_transaction xbt,
 452                               struct backend_info *be, int state)
 453 {
 454         struct xenbus_device *dev = be->dev;
 455         int err;
 456
 457         err = xenbus_printf(xbt, dev->nodename, "feature-flush-cache",
 458                             "%d", state);
 459         if (err)
 460                 dev_warn(&dev->dev, "writing feature-flush-cache (%d)", err);
 461
 462         return err;
 463 }
 464
 465 static void xen_blkbk_discard(struct xenbus_transaction xbt, struct backend_info *be)
 466 {
 467         struct xenbus_device *dev = be->dev;
 468         struct xen_blkif *blkif = be->blkif;
 469         int err;
 470         int state = 0;
 471         struct block_device *bdev = be->blkif->vbd.bdev;
 472         struct request_queue *q = bdev_get_queue(bdev);
 473
 474         if (blk_queue_discard(q)) {
 475                 err = xenbus_printf(xbt, dev->nodename,
 476                         "discard-granularity", "%u",
 477                         q->limits.discard_granularity);
 478                 if (err) {
 479                         dev_warn(&dev->dev, "writing discard-granularity (%d)", err);
 480                         return;
 481                 }
 482                 err = xenbus_printf(xbt, dev->nodename,
 483                         "discard-alignment", "%u",
 484                         q->limits.discard_alignment);
 485                 if (err) {
 486                         dev_warn(&dev->dev, "writing discard-alignment (%d)", err);
 487                         return;
 488                 }
 489                 state = 1;
 490                 /* Optional. */
 491                 err = xenbus_printf(xbt, dev->nodename,
 492                                     "discard-secure", "%d",
 493                                     blkif->vbd.discard_secure);
 494                 if (err) {
 495                         dev_warn(&dev->dev, "writing discard-secure (%d)", err);
 496                         return;
 497                 }
 498         }
 499         err = xenbus_printf(xbt, dev->nodename, "feature-discard",
 500                             "%d", state);
 501         if (err)
 502                 dev_warn(&dev->dev, "writing feature-discard (%d)", err);
 503 }
 504 int xen_blkbk_barrier(struct xenbus_transaction xbt,
 505                       struct backend_info *be, int state)
 506 {
 507         struct xenbus_device *dev = be->dev;
 508         int err;
 509
 510         err = xenbus_printf(xbt, dev->nodename, "feature-barrier",
 511                             "%d", state);
 512         if (err)
 513                 dev_warn(&dev->dev, "writing feature-barrier (%d)", err);
 514
 515         return err;
 516 }
 517
 518 /*
 519  * Entry point to this code when a new device is created.  Allocate the basic
 520  * structures, and watch the store waiting for the hotplug scripts to tell us
 521  * the device's physical major and minor numbers.  Switch to InitWait.
 522  */
 523 static int xen_blkbk_probe(struct xenbus_device *dev,
 524                            const struct xenbus_device_id *id)
 525 {
 526         int err;
 527         struct backend_info *be = kzalloc(sizeof(struct backend_info),
 528                                           GFP_KERNEL);
 529         if (!be) {
 530                 xenbus_dev_fatal(dev, -ENOMEM,
 531                                  "allocating backend structure");
 532                 return -ENOMEM;
 533         }
 534         be->dev = dev;
 535         dev_set_drvdata(&dev->dev, be);
 536
 537         be->blkif = xen_blkif_alloc(dev->otherend_id);
 538         if (IS_ERR(be->blkif)) {
 539                 err = PTR_ERR(be->blkif);
 540                 be->blkif = NULL;
 541                 xenbus_dev_fatal(dev, err, "creating block interface");
 542                 goto fail;
 543         }
 544
 545         /* setup back pointer */
 546         be->blkif->be = be;
 547
 548         err = xenbus_watch_pathfmt(dev, &be->backend_watch, backend_changed,
 549                                    "%s/%s", dev->nodename, "physical-device");
 550         if (err)
 551                 goto fail;
 552
 553         err = xenbus_switch_state(dev, XenbusStateInitWait);
 554         if (err)
 555                 goto fail;
 556
 557         return 0;
 558
 559 fail:
 560         DPRINTK("failed");
 561         xen_blkbk_remove(dev);
 562         return err;
 563 }
 564
 565
 566 /*
 567  * Callback received when the hotplug scripts have placed the physical-device
 568  * node.  Read it and the mode node, and create a vbd.  If the frontend is
 569  * ready, connect.
 570  */
 571 static void backend_changed(struct xenbus_watch *watch,
 572                             const char **vec, unsigned int len)
 573 {
 574         int err;
 575         unsigned major;
 576         unsigned minor;
 577         struct backend_info *be
 578                 = container_of(watch, struct backend_info, backend_watch);
 579         struct xenbus_device *dev = be->dev;
 580         int cdrom = 0;
 581         unsigned long handle;
 582         char *device_type;
 583
 584         DPRINTK("");
 585
 586         err = xenbus_scanf(XBT_NIL, dev->nodename, "physical-device", "%x:%x",
 587                            &major, &minor);
 588         if (XENBUS_EXIST_ERR(err)) {
 589                 /*
 590                  * Since this watch will fire once immediately after it is
 591                  * registered, we expect this.  Ignore it, and wait for the
 592                  * hotplug scripts.
 593                  */
 594                 return;
 595         }
 596         if (err != 2) {
 597                 xenbus_dev_fatal(dev, err, "reading physical-device");
 598                 return;
 599         }
 600
 601         if (be->major | be->minor) {
 602                 if (be->major != major || be->minor != minor)
 603                         pr_warn(DRV_PFX "changing physical device (from %x:%x to %x:%x) not supported.\n",
 604                                 be->major, be->minor, major, minor);
 605                 return;
 606         }
 607
 608         be->mode = xenbus_read(XBT_NIL, dev->nodename, "mode", NULL);
 609         if (IS_ERR(be->mode)) {
 610                 err = PTR_ERR(be->mode);
 611                 be->mode = NULL;
 612                 xenbus_dev_fatal(dev, err, "reading mode");
 613                 return;
 614         }
 615
 616         device_type = xenbus_read(XBT_NIL, dev->otherend, "device-type", NULL);
 617         if (!IS_ERR(device_type)) {
 618                 cdrom = strcmp(device_type, "cdrom") == 0;
 619                 kfree(device_type);
 620         }
 621
 622         /* Front end dir is a number, which is used as the handle. */
 623         err = strict_strtoul(strrchr(dev->otherend, '/') + 1, 0, &handle);
 624         if (err)
 625                 return;
 626
 627         be->major = major;
 628         be->minor = minor;
 629
 630         err = xen_vbd_create(be->blkif, handle, major, minor,
 631                              !strchr(be->mode, 'w'), cdrom);
 632
 633         if (err)
 634                 xenbus_dev_fatal(dev, err, "creating vbd structure");
 635         else {
 636                 err = xenvbd_sysfs_addif(dev);
 637                 if (err) {
 638                         xen_vbd_free(&be->blkif->vbd);
 639                         xenbus_dev_fatal(dev, err, "creating sysfs entries");
 640                 }
 641         }
 642
 643         if (err) {
 644                 kfree(be->mode);
 645                 be->mode = NULL;
 646                 be->major = 0;
 647                 be->minor = 0;
 648         } else {
 649                 /* We're potentially connected now */
 650                 xen_update_blkif_status(be->blkif);
 651         }
 652 }
 653
 654
 655 /*
 656  * Callback received when the frontend's state changes.
 657  */
 658 static void frontend_changed(struct xenbus_device *dev,
 659                              enum xenbus_state frontend_state)
 660 {
 661         struct backend_info *be = dev_get_drvdata(&dev->dev);
 662         int err;
 663
 664         DPRINTK("%s", xenbus_strstate(frontend_state));
 665
 666         switch (frontend_state) {
 667         case XenbusStateInitialising:
 668                 if (dev->state == XenbusStateClosed) {
 669                         pr_info(DRV_PFX "%s: prepare for reconnect\n",
 670                                 dev->nodename);
 671                         xenbus_switch_state(dev, XenbusStateInitWait);
 672                 }
 673                 break;
 674
 675         case XenbusStateInitialised:
 676         case XenbusStateConnected:
 677                 /*
 678                  * Ensure we connect even when two watches fire in
 679                  * close succession and we miss the intermediate value
 680                  * of frontend_state.
 681                  */
 682                 if (dev->state == XenbusStateConnected)
 683                         break;
 684
 685                 /*
 686                  * Enforce precondition before potential leak point.
 687                  * xen_blkif_disconnect() is idempotent.
 688                  */
 689                 xen_blkif_disconnect(be->blkif);
 690
 691                 err = connect_ring(be);
 692                 if (err)
 693                         break;
 694                 xen_update_blkif_status(be->blkif);
 695                 break;
 696
 697         case XenbusStateClosing:
 698                 xenbus_switch_state(dev, XenbusStateClosing);
 699                 break;
 700
 701         case XenbusStateClosed:
 702                 xen_blkif_disconnect(be->blkif);
 703                 xenbus_switch_state(dev, XenbusStateClosed);
 704                 if (xenbus_dev_is_online(dev))
 705                         break;
 706                 /* fall through if not online */
 707         case XenbusStateUnknown:
 708                 /* implies xen_blkif_disconnect() via xen_blkbk_remove() */
 709                 device_unregister(&dev->dev);
 710                 break;
 711
 712         default:
 713                 xenbus_dev_fatal(dev, -EINVAL, "saw state %d at frontend",
 714                                  frontend_state);
 715                 break;
 716         }
 717 }
 718
 719
 720 /* ** Connection ** */
 721
 722
 723 /*
 724  * Write the physical details regarding the block device to the store, and
 725  * switch to Connected state.
 726  */
 727 static void connect(struct backend_info *be)
 728 {
 729         struct xenbus_transaction xbt;
 730         int err;
 731         struct xenbus_device *dev = be->dev;
 732
 733         DPRINTK("%s", dev->otherend);
 734
 735         /* Supply the information about the device the frontend needs */
 736 again:
 737         err = xenbus_transaction_start(&xbt);
 738         if (err) {
 739                 xenbus_dev_fatal(dev, err, "starting transaction");
 740                 return;
 741         }
 742
 743         /* If we can't advertise it is OK. */
 744         xen_blkbk_flush_diskcache(xbt, be, be->blkif->vbd.flush_support);
 745
 746         xen_blkbk_discard(xbt, be);
 747
 748         xen_blkbk_barrier(xbt, be, be->blkif->vbd.flush_support);
 749
 750         err = xenbus_printf(xbt, dev->nodename, "feature-persistent", "%u", 1);
 751         if (err) {
 752                 xenbus_dev_fatal(dev, err, "writing %s/feature-persistent",
 753                                  dev->nodename);
 754                 goto abort;
 755         }
 756         err = xenbus_printf(xbt, dev->nodename, "feature-max-indirect-segments", "%u",
 757                             MAX_INDIRECT_SEGMENTS);
 758         if (err)
 759                 dev_warn(&dev->dev, "writing %s/feature-max-indirect-segments (%d)",
 760                          dev->nodename, err);
 761
 762         err = xenbus_printf(xbt, dev->nodename, "sectors", "%llu",
 763                             (unsigned long long)vbd_sz(&be->blkif->vbd));
 764         if (err) {
 765                 xenbus_dev_fatal(dev, err, "writing %s/sectors",
 766                                  dev->nodename);
 767                 goto abort;
 768         }
 769
 770         /* FIXME: use a typename instead */
 771         err = xenbus_printf(xbt, dev->nodename, "info", "%u",
 772                             be->blkif->vbd.type |
 773                             (be->blkif->vbd.readonly ? VDISK_READONLY : 0));
 774         if (err) {
 775                 xenbus_dev_fatal(dev, err, "writing %s/info",
 776                                  dev->nodename);
 777                 goto abort;
 778         }
 779         err = xenbus_printf(xbt, dev->nodename, "sector-size", "%lu",
 780                             (unsigned long)
 781                             bdev_logical_block_size(be->blkif->vbd.bdev));
 782         if (err) {
 783                 xenbus_dev_fatal(dev, err, "writing %s/sector-size",
 784                                  dev->nodename);
 785                 goto abort;
 786         }
 787         err = xenbus_printf(xbt, dev->nodename, "physical-sector-size", "%u",
 788                             bdev_physical_block_size(be->blkif->vbd.bdev));
 789         if (err)
 790                 xenbus_dev_error(dev, err, "writing %s/physical-sector-size",
 791                                  dev->nodename);
 792
 793         err = xenbus_transaction_end(xbt, 0);
 794         if (err == -EAGAIN)
 795                 goto again;
 796         if (err)
 797                 xenbus_dev_fatal(dev, err, "ending transaction");
 798
 799         err = xenbus_switch_state(dev, XenbusStateConnected);
 800         if (err)
 801                 xenbus_dev_fatal(dev, err, "%s: switching to Connected state",
 802                                  dev->nodename);
 803
 804         return;
 805  abort:
 806         xenbus_transaction_end(xbt, 1);
 807 }
 808
 809
 810 static int connect_ring(struct backend_info *be)
 811 {
 812         struct xenbus_device *dev = be->dev;
 813         unsigned long ring_ref;
 814         unsigned int evtchn;
 815         unsigned int pers_grants;
 816         char protocol[64] = "";
 817         int err;
 818
 819         DPRINTK("%s", dev->otherend);
 820
 821         err = xenbus_gather(XBT_NIL, dev->otherend, "ring-ref", "%lu",
 822                             &ring_ref, "event-channel", "%u", &evtchn, NULL);
 823         if (err) {
 824                 xenbus_dev_fatal(dev, err,
 825                                  "reading %s/ring-ref and event-channel",
 826                                  dev->otherend);
 827                 return err;
 828         }
 829
 830         be->blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
 831         err = xenbus_gather(XBT_NIL, dev->otherend, "protocol",
 832                             "%63s", protocol, NULL);
 833         if (err)
 834                 strcpy(protocol, "unspecified, assuming native");
 835         else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_NATIVE))
 836                 be->blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
 837         else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_32))
 838                 be->blkif->blk_protocol = BLKIF_PROTOCOL_X86_32;
 839         else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_64))
 840                 be->blkif->blk_protocol = BLKIF_PROTOCOL_X86_64;
 841         else {
 842                 xenbus_dev_fatal(dev, err, "unknown fe protocol %s", protocol);
 843                 return -1;
 844         }
 845         err = xenbus_gather(XBT_NIL, dev->otherend,
 846                             "feature-persistent", "%u",
 847                             &pers_grants, NULL);
 848         if (err)
 849                 pers_grants = 0;
 850
 851         be->blkif->vbd.feature_gnt_persistent = pers_grants;
 852         be->blkif->vbd.overflow_max_grants = 0;
 853
 854         pr_info(DRV_PFX "ring-ref %ld, event-channel %d, protocol %d (%s) %s\n",
 855                 ring_ref, evtchn, be->blkif->blk_protocol, protocol,
 856                 pers_grants ? "persistent grants" : "");
 857
 858         /* Map the shared frame, irq etc. */
 859         err = xen_blkif_map(be->blkif, ring_ref, evtchn);
 860         if (err) {
 861                 xenbus_dev_fatal(dev, err, "mapping ring-ref %lu port %u",
 862                                  ring_ref, evtchn);
 863                 return err;
 864         }
 865
 866         return 0;
 867 }
 868
 869
 870 /* ** Driver Registration ** */
 871
 872
 873 static const struct xenbus_device_id xen_blkbk_ids[] = {
 874         { "vbd" },
 875         { "" }
 876 };
 877
 878
 879 static DEFINE_XENBUS_DRIVER(xen_blkbk, ,
 880         .probe = xen_blkbk_probe,
 881         .remove = xen_blkbk_remove,
 882         .otherend_changed = frontend_changed
 883 );
 884
 885
 886 int xen_blkif_xenbus_init(void)
 887 {
 888         return xenbus_register_backend(&xen_blkbk_driver);
 889 }