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
 122         return blkif;
 123 }
 124
 125 static int map_frontend_page(struct xen_blkif *blkif, unsigned long shared_page)
 126 {
 127         struct gnttab_map_grant_ref op;
 128
 129         gnttab_set_map_op(&op, (unsigned long)blkif->blk_ring_area->addr,
 130                           GNTMAP_host_map, shared_page, blkif->domid);
 131
 132         if (HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, &op, 1))
 133                 BUG();
 134
 135         if (op.status) {
 136                 DPRINTK("Grant table operation failure !\n");
 137                 return op.status;
 138         }
 139
 140         blkif->shmem_ref = shared_page;
 141         blkif->shmem_handle = op.handle;
 142
 143         return 0;
 144 }
 145
 146 static void unmap_frontend_page(struct xen_blkif *blkif)
 147 {
 148         struct gnttab_unmap_grant_ref op;
 149
 150         gnttab_set_unmap_op(&op, (unsigned long)blkif->blk_ring_area->addr,
 151                             GNTMAP_host_map, blkif->shmem_handle);
 152
 153         if (HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, &op, 1))
 154                 BUG();
 155 }
 156
 157 static int xen_blkif_map(struct xen_blkif *blkif, unsigned long shared_page,
 158                          unsigned int evtchn)
 159 {
 160         int err;
 161
 162         /* Already connected through? */
 163         if (blkif->irq)
 164                 return 0;
 165
 166         blkif->blk_ring_area = alloc_vm_area(PAGE_SIZE);
 167         if (!blkif->blk_ring_area)
 168                 return -ENOMEM;
 169
 170         err = map_frontend_page(blkif, shared_page);
 171         if (err) {
 172                 free_vm_area(blkif->blk_ring_area);
 173                 return err;
 174         }
 175
 176         switch (blkif->blk_protocol) {
 177         case BLKIF_PROTOCOL_NATIVE:
 178         {
 179                 struct blkif_sring *sring;
 180                 sring = (struct blkif_sring *)blkif->blk_ring_area->addr;
 181                 BACK_RING_INIT(&blkif->blk_rings.native, sring, PAGE_SIZE);
 182                 break;
 183         }
 184         case BLKIF_PROTOCOL_X86_32:
 185         {
 186                 struct blkif_x86_32_sring *sring_x86_32;
 187                 sring_x86_32 = (struct blkif_x86_32_sring *)blkif->blk_ring_area->addr;
 188                 BACK_RING_INIT(&blkif->blk_rings.x86_32, sring_x86_32, PAGE_SIZE);
 189                 break;
 190         }
 191         case BLKIF_PROTOCOL_X86_64:
 192         {
 193                 struct blkif_x86_64_sring *sring_x86_64;
 194                 sring_x86_64 = (struct blkif_x86_64_sring *)blkif->blk_ring_area->addr;
 195                 BACK_RING_INIT(&blkif->blk_rings.x86_64, sring_x86_64, PAGE_SIZE);
 196                 break;
 197         }
 198         default:
 199                 BUG();
 200         }
 201
 202         err = bind_interdomain_evtchn_to_irqhandler(blkif->domid, evtchn,
 203                                                     xen_blkif_be_int, 0,
 204                                                     "blkif-backend", blkif);
 205         if (err < 0) {
 206                 unmap_frontend_page(blkif);
 207                 free_vm_area(blkif->blk_ring_area);
 208                 blkif->blk_rings.common.sring = NULL;
 209                 return err;
 210         }
 211         blkif->irq = err;
 212
 213         return 0;
 214 }
 215
 216 static void xen_blkif_disconnect(struct xen_blkif *blkif)
 217 {
 218         if (blkif->xenblkd) {
 219                 kthread_stop(blkif->xenblkd);
 220                 blkif->xenblkd = NULL;
 221         }
 222
 223         atomic_dec(&blkif->refcnt);
 224         wait_event(blkif->waiting_to_free, atomic_read(&blkif->refcnt) == 0);
 225         atomic_inc(&blkif->refcnt);
 226
 227         if (blkif->irq) {
 228                 unbind_from_irqhandler(blkif->irq, blkif);
 229                 blkif->irq = 0;
 230         }
 231
 232         if (blkif->blk_rings.common.sring) {
 233                 unmap_frontend_page(blkif);
 234                 free_vm_area(blkif->blk_ring_area);
 235                 blkif->blk_rings.common.sring = NULL;
 236         }
 237 }
 238
 239 void xen_blkif_free(struct xen_blkif *blkif)
 240 {
 241         if (!atomic_dec_and_test(&blkif->refcnt))
 242                 BUG();
 243         kmem_cache_free(xen_blkif_cachep, blkif);
 244 }
 245
 246 int __init xen_blkif_interface_init(void)
 247 {
 248         xen_blkif_cachep = kmem_cache_create("blkif_cache",
 249                                              sizeof(struct xen_blkif),
 250                                              0, 0, NULL);
 251         if (!xen_blkif_cachep)
 252                 return -ENOMEM;
 253
 254         return 0;
 255 }
 256
 257 /*
 258  *  sysfs interface for VBD I/O requests
 259  */
 260
 261 #define VBD_SHOW(name, format, args...)                                 \
 262         static ssize_t show_##name(struct device *_dev,                 \
 263                                    struct device_attribute *attr,       \
 264                                    char *buf)                           \
 265         {                                                               \
 266                 struct xenbus_device *dev = to_xenbus_device(_dev);     \
 267                 struct backend_info *be = dev_get_drvdata(&dev->dev);   \
 268                                                                         \
 269                 return sprintf(buf, format, ##args);                    \
 270         }                                                               \
 271         static DEVICE_ATTR(name, S_IRUGO, show_##name, NULL)
 272
 273 VBD_SHOW(oo_req,  "%d\n", be->blkif->st_oo_req);
 274 VBD_SHOW(rd_req,  "%d\n", be->blkif->st_rd_req);
 275 VBD_SHOW(wr_req,  "%d\n", be->blkif->st_wr_req);
 276 VBD_SHOW(f_req,  "%d\n", be->blkif->st_f_req);
 277 VBD_SHOW(ds_req,  "%d\n", be->blkif->st_ds_req);
 278 VBD_SHOW(rd_sect, "%d\n", be->blkif->st_rd_sect);
 279 VBD_SHOW(wr_sect, "%d\n", be->blkif->st_wr_sect);
 280
 281 static struct attribute *xen_vbdstat_attrs[] = {
 282         &dev_attr_oo_req.attr,
 283         &dev_attr_rd_req.attr,
 284         &dev_attr_wr_req.attr,
 285         &dev_attr_f_req.attr,
 286         &dev_attr_ds_req.attr,
 287         &dev_attr_rd_sect.attr,
 288         &dev_attr_wr_sect.attr,
 289         NULL
 290 };
 291
 292 static struct attribute_group xen_vbdstat_group = {
 293         .name = "statistics",
 294         .attrs = xen_vbdstat_attrs,
 295 };
 296
 297 VBD_SHOW(physical_device, "%x:%x\n", be->major, be->minor);
 298 VBD_SHOW(mode, "%s\n", be->mode);
 299
 300 int xenvbd_sysfs_addif(struct xenbus_device *dev)
 301 {
 302         int error;
 303
 304         error = device_create_file(&dev->dev, &dev_attr_physical_device);
 305         if (error)
 306                 goto fail1;
 307
 308         error = device_create_file(&dev->dev, &dev_attr_mode);
 309         if (error)
 310                 goto fail2;
 311
 312         error = sysfs_create_group(&dev->dev.kobj, &xen_vbdstat_group);
 313         if (error)
 314                 goto fail3;
 315
 316         return 0;
 317
 318 fail3:  sysfs_remove_group(&dev->dev.kobj, &xen_vbdstat_group);
 319 fail2:  device_remove_file(&dev->dev, &dev_attr_mode);
 320 fail1:  device_remove_file(&dev->dev, &dev_attr_physical_device);
 321         return error;
 322 }
 323
 324 void xenvbd_sysfs_delif(struct xenbus_device *dev)
 325 {
 326         sysfs_remove_group(&dev->dev.kobj, &xen_vbdstat_group);
 327         device_remove_file(&dev->dev, &dev_attr_mode);
 328         device_remove_file(&dev->dev, &dev_attr_physical_device);
 329 }
 330
 331
 332 static void xen_vbd_free(struct xen_vbd *vbd)
 333 {
 334         if (vbd->bdev)
 335                 blkdev_put(vbd->bdev, vbd->readonly ? FMODE_READ : FMODE_WRITE);
 336         vbd->bdev = NULL;
 337 }
 338
 339 static int xen_vbd_create(struct xen_blkif *blkif, blkif_vdev_t handle,
 340                           unsigned major, unsigned minor, int readonly,
 341                           int cdrom)
 342 {
 343         struct xen_vbd *vbd;
 344         struct block_device *bdev;
 345         struct request_queue *q;
 346
 347         vbd = &blkif->vbd;
 348         vbd->handle   = handle;
 349         vbd->readonly = readonly;
 350         vbd->type     = 0;
 351
 352         vbd->pdevice  = MKDEV(major, minor);
 353
 354         bdev = blkdev_get_by_dev(vbd->pdevice, vbd->readonly ?
 355                                  FMODE_READ : FMODE_WRITE, NULL);
 356
 357         if (IS_ERR(bdev)) {
 358                 DPRINTK("xen_vbd_create: device %08x could not be opened.\n",
 359                         vbd->pdevice);
 360                 return -ENOENT;
 361         }
 362
 363         vbd->bdev = bdev;
 364         if (vbd->bdev->bd_disk == NULL) {
 365                 DPRINTK("xen_vbd_create: device %08x doesn't exist.\n",
 366                         vbd->pdevice);
 367                 xen_vbd_free(vbd);
 368                 return -ENOENT;
 369         }
 370         vbd->size = vbd_sz(vbd);
 371
 372         if (vbd->bdev->bd_disk->flags & GENHD_FL_CD || cdrom)
 373                 vbd->type |= VDISK_CDROM;
 374         if (vbd->bdev->bd_disk->flags & GENHD_FL_REMOVABLE)
 375                 vbd->type |= VDISK_REMOVABLE;
 376
 377         q = bdev_get_queue(bdev);
 378         if (q && q->flush_flags)
 379                 vbd->flush_support = true;
 380
 381         DPRINTK("Successful creation of handle=%04x (dom=%u)\n",
 382                 handle, blkif->domid);
 383         return 0;
 384 }
 385 static int xen_blkbk_remove(struct xenbus_device *dev)
 386 {
 387         struct backend_info *be = dev_get_drvdata(&dev->dev);
 388
 389         DPRINTK("");
 390
 391         if (be->major || be->minor)
 392                 xenvbd_sysfs_delif(dev);
 393
 394         if (be->backend_watch.node) {
 395                 unregister_xenbus_watch(&be->backend_watch);
 396                 kfree(be->backend_watch.node);
 397                 be->backend_watch.node = NULL;
 398         }
 399
 400         if (be->blkif) {
 401                 xen_blkif_disconnect(be->blkif);
 402                 xen_vbd_free(&be->blkif->vbd);
 403                 xen_blkif_free(be->blkif);
 404                 be->blkif = NULL;
 405         }
 406
 407         kfree(be);
 408         dev_set_drvdata(&dev->dev, NULL);
 409         return 0;
 410 }
 411
 412 int xen_blkbk_flush_diskcache(struct xenbus_transaction xbt,
 413                               struct backend_info *be, int state)
 414 {
 415         struct xenbus_device *dev = be->dev;
 416         int err;
 417
 418         err = xenbus_printf(xbt, dev->nodename, "feature-flush-cache",
 419                             "%d", state);
 420         if (err)
 421                 xenbus_dev_fatal(dev, err, "writing feature-flush-cache");
 422
 423         return err;
 424 }
 425
 426 int xen_blkbk_discard(struct xenbus_transaction xbt, struct backend_info *be)
 427 {
 428         struct xenbus_device *dev = be->dev;
 429         struct xen_blkif *blkif = be->blkif;
 430         char *type;
 431         int err;
 432         int state = 0;
 433
 434         type = xenbus_read(XBT_NIL, dev->nodename, "type", NULL);
 435         if (!IS_ERR(type)) {
 436                 if (strncmp(type, "file", 4) == 0) {
 437                         state = 1;
 438                         blkif->blk_backend_type = BLKIF_BACKEND_FILE;
 439                 }
 440                 if (strncmp(type, "phy", 3) == 0) {
 441                         struct block_device *bdev = be->blkif->vbd.bdev;
 442                         struct request_queue *q = bdev_get_queue(bdev);
 443                         if (blk_queue_discard(q)) {
 444                                 err = xenbus_printf(xbt, dev->nodename,
 445                                         "discard-granularity", "%u",
 446                                         q->limits.discard_granularity);
 447                                 if (err) {
 448                                         xenbus_dev_fatal(dev, err,
 449                                                 "writing discard-granularity");
 450                                         goto kfree;
 451                                 }
 452                                 err = xenbus_printf(xbt, dev->nodename,
 453                                         "discard-alignment", "%u",
 454                                         q->limits.discard_alignment);
 455                                 if (err) {
 456                                         xenbus_dev_fatal(dev, err,
 457                                                 "writing discard-alignment");
 458                                         goto kfree;
 459                                 }
 460                                 state = 1;
 461                                 blkif->blk_backend_type = BLKIF_BACKEND_PHY;
 462                         }
 463                 }
 464         } else {
 465                 err = PTR_ERR(type);
 466                 xenbus_dev_fatal(dev, err, "reading type");
 467                 goto out;
 468         }
 469
 470         err = xenbus_printf(xbt, dev->nodename, "feature-discard",
 471                             "%d", state);
 472         if (err)
 473                 xenbus_dev_fatal(dev, err, "writing feature-discard");
 474 kfree:
 475         kfree(type);
 476 out:
 477         return err;
 478 }
 479 int xen_blkbk_barrier(struct xenbus_transaction xbt,
 480                       struct backend_info *be, int state)
 481 {
 482         struct xenbus_device *dev = be->dev;
 483         int err;
 484
 485         err = xenbus_printf(xbt, dev->nodename, "feature-barrier",
 486                             "%d", state);
 487         if (err)
 488                 xenbus_dev_fatal(dev, err, "writing feature-barrier");
 489
 490         return err;
 491 }
 492
 493 /*
 494  * Entry point to this code when a new device is created.  Allocate the basic
 495  * structures, and watch the store waiting for the hotplug scripts to tell us
 496  * the device's physical major and minor numbers.  Switch to InitWait.
 497  */
 498 static int xen_blkbk_probe(struct xenbus_device *dev,
 499                            const struct xenbus_device_id *id)
 500 {
 501         int err;
 502         struct backend_info *be = kzalloc(sizeof(struct backend_info),
 503                                           GFP_KERNEL);
 504         if (!be) {
 505                 xenbus_dev_fatal(dev, -ENOMEM,
 506                                  "allocating backend structure");
 507                 return -ENOMEM;
 508         }
 509         be->dev = dev;
 510         dev_set_drvdata(&dev->dev, be);
 511
 512         be->blkif = xen_blkif_alloc(dev->otherend_id);
 513         if (IS_ERR(be->blkif)) {
 514                 err = PTR_ERR(be->blkif);
 515                 be->blkif = NULL;
 516                 xenbus_dev_fatal(dev, err, "creating block interface");
 517                 goto fail;
 518         }
 519
 520         /* setup back pointer */
 521         be->blkif->be = be;
 522
 523         err = xenbus_watch_pathfmt(dev, &be->backend_watch, backend_changed,
 524                                    "%s/%s", dev->nodename, "physical-device");
 525         if (err)
 526                 goto fail;
 527
 528         err = xenbus_switch_state(dev, XenbusStateInitWait);
 529         if (err)
 530                 goto fail;
 531
 532         return 0;
 533
 534 fail:
 535         DPRINTK("failed");
 536         xen_blkbk_remove(dev);
 537         return err;
 538 }
 539
 540
 541 /*
 542  * Callback received when the hotplug scripts have placed the physical-device
 543  * node.  Read it and the mode node, and create a vbd.  If the frontend is
 544  * ready, connect.
 545  */
 546 static void backend_changed(struct xenbus_watch *watch,
 547                             const char **vec, unsigned int len)
 548 {
 549         int err;
 550         unsigned major;
 551         unsigned minor;
 552         struct backend_info *be
 553                 = container_of(watch, struct backend_info, backend_watch);
 554         struct xenbus_device *dev = be->dev;
 555         int cdrom = 0;
 556         char *device_type;
 557
 558         DPRINTK("");
 559
 560         err = xenbus_scanf(XBT_NIL, dev->nodename, "physical-device", "%x:%x",
 561                            &major, &minor);
 562         if (XENBUS_EXIST_ERR(err)) {
 563                 /*
 564                  * Since this watch will fire once immediately after it is
 565                  * registered, we expect this.  Ignore it, and wait for the
 566                  * hotplug scripts.
 567                  */
 568                 return;
 569         }
 570         if (err != 2) {
 571                 xenbus_dev_fatal(dev, err, "reading physical-device");
 572                 return;
 573         }
 574
 575         if ((be->major || be->minor) &&
 576             ((be->major != major) || (be->minor != minor))) {
 577                 pr_warn(DRV_PFX "changing physical device (from %x:%x to %x:%x) not supported.\n",
 578                         be->major, be->minor, major, minor);
 579                 return;
 580         }
 581
 582         be->mode = xenbus_read(XBT_NIL, dev->nodename, "mode", NULL);
 583         if (IS_ERR(be->mode)) {
 584                 err = PTR_ERR(be->mode);
 585                 be->mode = NULL;
 586                 xenbus_dev_fatal(dev, err, "reading mode");
 587                 return;
 588         }
 589
 590         device_type = xenbus_read(XBT_NIL, dev->otherend, "device-type", NULL);
 591         if (!IS_ERR(device_type)) {
 592                 cdrom = strcmp(device_type, "cdrom") == 0;
 593                 kfree(device_type);
 594         }
 595
 596         if (be->major == 0 && be->minor == 0) {
 597                 /* Front end dir is a number, which is used as the handle. */
 598
 599                 char *p = strrchr(dev->otherend, '/') + 1;
 600                 long handle;
 601                 err = strict_strtoul(p, 0, &handle);
 602                 if (err)
 603                         return;
 604
 605                 be->major = major;
 606                 be->minor = minor;
 607
 608                 err = xen_vbd_create(be->blkif, handle, major, minor,
 609                                  (NULL == strchr(be->mode, 'w')), cdrom);
 610                 if (err) {
 611                         be->major = 0;
 612                         be->minor = 0;
 613                         xenbus_dev_fatal(dev, err, "creating vbd structure");
 614                         return;
 615                 }
 616
 617                 err = xenvbd_sysfs_addif(dev);
 618                 if (err) {
 619                         xen_vbd_free(&be->blkif->vbd);
 620                         be->major = 0;
 621                         be->minor = 0;
 622                         xenbus_dev_fatal(dev, err, "creating sysfs entries");
 623                         return;
 624                 }
 625
 626                 /* We're potentially connected now */
 627                 xen_update_blkif_status(be->blkif);
 628         }
 629 }
 630
 631
 632 /*
 633  * Callback received when the frontend's state changes.
 634  */
 635 static void frontend_changed(struct xenbus_device *dev,
 636                              enum xenbus_state frontend_state)
 637 {
 638         struct backend_info *be = dev_get_drvdata(&dev->dev);
 639         int err;
 640
 641         DPRINTK("%s", xenbus_strstate(frontend_state));
 642
 643         switch (frontend_state) {
 644         case XenbusStateInitialising:
 645                 if (dev->state == XenbusStateClosed) {
 646                         pr_info(DRV_PFX "%s: prepare for reconnect\n",
 647                                 dev->nodename);
 648                         xenbus_switch_state(dev, XenbusStateInitWait);
 649                 }
 650                 break;
 651
 652         case XenbusStateInitialised:
 653         case XenbusStateConnected:
 654                 /*
 655                  * Ensure we connect even when two watches fire in
 656                  * close successsion and we miss the intermediate value
 657                  * of frontend_state.
 658                  */
 659                 if (dev->state == XenbusStateConnected)
 660                         break;
 661
 662                 /*
 663                  * Enforce precondition before potential leak point.
 664                  * xen_blkif_disconnect() is idempotent.
 665                  */
 666                 xen_blkif_disconnect(be->blkif);
 667
 668                 err = connect_ring(be);
 669                 if (err)
 670                         break;
 671                 xen_update_blkif_status(be->blkif);
 672                 break;
 673
 674         case XenbusStateClosing:
 675                 xenbus_switch_state(dev, XenbusStateClosing);
 676                 break;
 677
 678         case XenbusStateClosed:
 679                 xen_blkif_disconnect(be->blkif);
 680                 xenbus_switch_state(dev, XenbusStateClosed);
 681                 if (xenbus_dev_is_online(dev))
 682                         break;
 683                 /* fall through if not online */
 684         case XenbusStateUnknown:
 685                 /* implies xen_blkif_disconnect() via xen_blkbk_remove() */
 686                 device_unregister(&dev->dev);
 687                 break;
 688
 689         default:
 690                 xenbus_dev_fatal(dev, -EINVAL, "saw state %d at frontend",
 691                                  frontend_state);
 692                 break;
 693         }
 694 }
 695
 696
 697 /* ** Connection ** */
 698
 699
 700 /*
 701  * Write the physical details regarding the block device to the store, and
 702  * switch to Connected state.
 703  */
 704 static void connect(struct backend_info *be)
 705 {
 706         struct xenbus_transaction xbt;
 707         int err;
 708         struct xenbus_device *dev = be->dev;
 709
 710         DPRINTK("%s", dev->otherend);
 711
 712         /* Supply the information about the device the frontend needs */
 713 again:
 714         err = xenbus_transaction_start(&xbt);
 715         if (err) {
 716                 xenbus_dev_fatal(dev, err, "starting transaction");
 717                 return;
 718         }
 719
 720         err = xen_blkbk_flush_diskcache(xbt, be, be->blkif->vbd.flush_support);
 721         if (err)
 722                 goto abort;
 723
 724         err = xen_blkbk_discard(xbt, be);
 725
 726         /* If we can't advertise it is OK. */
 727         err = xen_blkbk_barrier(xbt, be, be->blkif->vbd.flush_support);
 728
 729         err = xenbus_printf(xbt, dev->nodename, "sectors", "%llu",
 730                             (unsigned long long)vbd_sz(&be->blkif->vbd));
 731         if (err) {
 732                 xenbus_dev_fatal(dev, err, "writing %s/sectors",
 733                                  dev->nodename);
 734                 goto abort;
 735         }
 736
 737         /* FIXME: use a typename instead */
 738         err = xenbus_printf(xbt, dev->nodename, "info", "%u",
 739                             be->blkif->vbd.type |
 740                             (be->blkif->vbd.readonly ? VDISK_READONLY : 0));
 741         if (err) {
 742                 xenbus_dev_fatal(dev, err, "writing %s/info",
 743                                  dev->nodename);
 744                 goto abort;
 745         }
 746         err = xenbus_printf(xbt, dev->nodename, "sector-size", "%lu",
 747                             (unsigned long)
 748                             bdev_logical_block_size(be->blkif->vbd.bdev));
 749         if (err) {
 750                 xenbus_dev_fatal(dev, err, "writing %s/sector-size",
 751                                  dev->nodename);
 752                 goto abort;
 753         }
 754
 755         err = xenbus_transaction_end(xbt, 0);
 756         if (err == -EAGAIN)
 757                 goto again;
 758         if (err)
 759                 xenbus_dev_fatal(dev, err, "ending transaction");
 760
 761         err = xenbus_switch_state(dev, XenbusStateConnected);
 762         if (err)
 763                 xenbus_dev_fatal(dev, err, "%s: switching to Connected state",
 764                                  dev->nodename);
 765
 766         return;
 767  abort:
 768         xenbus_transaction_end(xbt, 1);
 769 }
 770
 771
 772 static int connect_ring(struct backend_info *be)
 773 {
 774         struct xenbus_device *dev = be->dev;
 775         unsigned long ring_ref;
 776         unsigned int evtchn;
 777         char protocol[64] = "";
 778         int err;
 779
 780         DPRINTK("%s", dev->otherend);
 781
 782         err = xenbus_gather(XBT_NIL, dev->otherend, "ring-ref", "%lu",
 783                             &ring_ref, "event-channel", "%u", &evtchn, NULL);
 784         if (err) {
 785                 xenbus_dev_fatal(dev, err,
 786                                  "reading %s/ring-ref and event-channel",
 787                                  dev->otherend);
 788                 return err;
 789         }
 790
 791         be->blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
 792         err = xenbus_gather(XBT_NIL, dev->otherend, "protocol",
 793                             "%63s", protocol, NULL);
 794         if (err)
 795                 strcpy(protocol, "unspecified, assuming native");
 796         else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_NATIVE))
 797                 be->blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
 798         else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_32))
 799                 be->blkif->blk_protocol = BLKIF_PROTOCOL_X86_32;
 800         else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_64))
 801                 be->blkif->blk_protocol = BLKIF_PROTOCOL_X86_64;
 802         else {
 803                 xenbus_dev_fatal(dev, err, "unknown fe protocol %s", protocol);
 804                 return -1;
 805         }
 806         pr_info(DRV_PFX "ring-ref %ld, event-channel %d, protocol %d (%s)\n",
 807                 ring_ref, evtchn, be->blkif->blk_protocol, protocol);
 808
 809         /* Map the shared frame, irq etc. */
 810         err = xen_blkif_map(be->blkif, ring_ref, evtchn);
 811         if (err) {
 812                 xenbus_dev_fatal(dev, err, "mapping ring-ref %lu port %u",
 813                                  ring_ref, evtchn);
 814                 return err;
 815         }
 816
 817         return 0;
 818 }
 819
 820
 821 /* ** Driver Registration ** */
 822
 823
 824 static const struct xenbus_device_id xen_blkbk_ids[] = {
 825         { "vbd" },
 826         { "" }
 827 };
 828
 829
 830 static struct xenbus_driver xen_blkbk = {
 831         .name = "vbd",
 832         .owner = THIS_MODULE,
 833         .ids = xen_blkbk_ids,
 834         .probe = xen_blkbk_probe,
 835         .remove = xen_blkbk_remove,
 836         .otherend_changed = frontend_changed
 837 };
 838
 839
 840 int xen_blkif_xenbus_init(void)
 841 {
 842         return xenbus_register_backend(&xen_blkbk);
 843 }