drivers/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     You should have received a copy of the GNU General Public License
  16     along with this program; if not, write to the Free Software
  17     Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  18 */
  19
  20 #include <stdarg.h>
  21 #include <linux/kthread.h>
  22 #include "common.h"
  23 #include "../core/domctl.h"
  24
  25 #undef DPRINTK
  26 #define DPRINTK(fmt, args...)                           \
  27         pr_debug("blkback/xenbus (%s:%d) " fmt ".\n",   \
  28                  __FUNCTION__, __LINE__, ##args)
  29
  30 static void connect(struct backend_info *);
  31 static int connect_ring(struct backend_info *);
  32 static void backend_changed(struct xenbus_watch *, const char **,
  33                             unsigned int);
  34
  35 static int blkback_name(blkif_t *blkif, char *buf)
  36 {
  37         char *devpath, *devname;
  38         struct xenbus_device *dev = blkif->be->dev;
  39
  40         devpath = xenbus_read(XBT_NIL, dev->nodename, "dev", NULL);
  41         if (IS_ERR(devpath))
  42                 return PTR_ERR(devpath);
  43
  44         if ((devname = strstr(devpath, "/dev/")) != NULL)
  45                 devname += strlen("/dev/");
  46         else
  47                 devname  = devpath;
  48
  49         snprintf(buf, TASK_COMM_LEN, "blkback.%d.%s", blkif->domid, devname);
  50         kfree(devpath);
  51
  52         return 0;
  53 }
  54
  55 static void update_blkif_status(blkif_t *blkif)
  56 {
  57         int err;
  58         char name[TASK_COMM_LEN];
  59
  60         /* Not ready to connect? */
  61         if (!blkif->irq)
  62                 return;
  63
  64         /* Already connected? */
  65         if (blkif->be->dev->state == XenbusStateConnected)
  66                 return;
  67
  68         /* Attempt to connect: exit if we fail to. */
  69         connect(blkif->be);
  70         if (blkif->be->dev->state != XenbusStateConnected)
  71                 return;
  72
  73         err = blkback_name(blkif, name);
  74         if (err) {
  75                 xenbus_dev_error(blkif->be->dev, err, "get blkback dev name");
  76                 return;
  77         }
  78
  79         if (blkif->vbd.bdev) {
  80                 struct address_space *mapping
  81                         = blkif->vbd.bdev->bd_inode->i_mapping;
  82
  83                 err = filemap_write_and_wait(mapping);
  84                 if (err) {
  85                         xenbus_dev_error(blkif->be->dev, err, "block flush");
  86                         return;
  87                 }
  88                 invalidate_inode_pages2(mapping);
  89         }
  90
  91         blkif->xenblkd = kthread_run(blkif_schedule, blkif, name);
  92         if (IS_ERR(blkif->xenblkd)) {
  93                 err = PTR_ERR(blkif->xenblkd);
  94                 blkif->xenblkd = NULL;
  95                 xenbus_dev_error(blkif->be->dev, err, "start xenblkd");
  96         }
  97 }
  98
  99
 100 /****************************************************************
 101  *  sysfs interface for VBD I/O requests
 102  */
 103
 104 #define VBD_SHOW(name, format, args...)                                 \
 105         static ssize_t show_##name(struct device *_dev,                 \
 106                                    struct device_attribute *attr,       \
 107                                    char *buf)                           \
 108         {                                                               \
 109                 ssize_t ret = -ENODEV;                                  \
 110                 struct xenbus_device *dev;                              \
 111                 struct backend_info *be;                                \
 112                                                                         \
 113                 if (!get_device(_dev))                                  \
 114                         return ret;                                     \
 115                 dev = to_xenbus_device(_dev);                           \
 116                 if ((be = dev_get_drvdata(&dev->dev)) != NULL)          \
 117                         ret = sprintf(buf, format, ##args);             \
 118                 put_device(_dev);                                       \
 119                 return ret;                                             \
 120         }                                                               \
 121         static DEVICE_ATTR(name, S_IRUGO, show_##name, NULL)
 122
 123 VBD_SHOW(oo_req,  "%d\n", be->blkif->st_oo_req);
 124 VBD_SHOW(rd_req,  "%d\n", be->blkif->st_rd_req);
 125 VBD_SHOW(wr_req,  "%d\n", be->blkif->st_wr_req);
 126 VBD_SHOW(br_req,  "%d\n", be->blkif->st_br_req);
 127 VBD_SHOW(fl_req,  "%d\n", be->blkif->st_fl_req);
 128 VBD_SHOW(ds_req,  "%d\n", be->blkif->st_ds_req);
 129 VBD_SHOW(rd_sect, "%d\n", be->blkif->st_rd_sect);
 130 VBD_SHOW(wr_sect, "%d\n", be->blkif->st_wr_sect);
 131
 132 static struct attribute *vbdstat_attrs[] = {
 133         &dev_attr_oo_req.attr,
 134         &dev_attr_rd_req.attr,
 135         &dev_attr_wr_req.attr,
 136         &dev_attr_br_req.attr,
 137         &dev_attr_fl_req.attr,
 138         &dev_attr_ds_req.attr,
 139         &dev_attr_rd_sect.attr,
 140         &dev_attr_wr_sect.attr,
 141         NULL
 142 };
 143
 144 static const struct attribute_group vbdstat_group = {
 145         .name = "statistics",
 146         .attrs = vbdstat_attrs,
 147 };
 148
 149 VBD_SHOW(physical_device, "%x:%x\n", be->major, be->minor);
 150 VBD_SHOW(mode, "%s\n", be->mode);
 151
 152 int xenvbd_sysfs_addif(struct xenbus_device *dev)
 153 {
 154         int error;
 155
 156         error = device_create_file(&dev->dev, &dev_attr_physical_device);
 157         if (error)
 158                 goto fail1;
 159
 160         error = device_create_file(&dev->dev, &dev_attr_mode);
 161         if (error)
 162                 goto fail2;
 163
 164         error = sysfs_create_group(&dev->dev.kobj, &vbdstat_group);
 165         if (error)
 166                 goto fail3;
 167
 168         return 0;
 169
 170 fail3:  sysfs_remove_group(&dev->dev.kobj, &vbdstat_group);
 171 fail2:  device_remove_file(&dev->dev, &dev_attr_mode);
 172 fail1:  device_remove_file(&dev->dev, &dev_attr_physical_device);
 173         return error;
 174 }
 175
 176 void xenvbd_sysfs_delif(struct xenbus_device *dev)
 177 {
 178         sysfs_remove_group(&dev->dev.kobj, &vbdstat_group);
 179         device_remove_file(&dev->dev, &dev_attr_mode);
 180         device_remove_file(&dev->dev, &dev_attr_physical_device);
 181 }
 182
 183 static int blkback_remove(struct xenbus_device *dev)
 184 {
 185         struct backend_info *be = dev_get_drvdata(&dev->dev);
 186
 187         DPRINTK("");
 188
 189         if (be->major || be->minor)
 190                 xenvbd_sysfs_delif(dev);
 191
 192         if (be->backend_watch.node) {
 193                 unregister_xenbus_watch(&be->backend_watch);
 194                 kfree(be->backend_watch.node);
 195                 be->backend_watch.node = NULL;
 196         }
 197
 198         if (be->cdrom_watch.node) {
 199                 unregister_xenbus_watch(&be->cdrom_watch);
 200                 kfree(be->cdrom_watch.node);
 201                 be->cdrom_watch.node = NULL;
 202         }
 203
 204         if (be->blkif) {
 205                 blkif_disconnect(be->blkif);
 206                 vbd_free(&be->blkif->vbd);
 207                 blkif_free(be->blkif);
 208                 be->blkif = NULL;
 209         }
 210
 211         kfree(be);
 212         dev_set_drvdata(&dev->dev, NULL);
 213         return 0;
 214 }
 215
 216 void blkback_barrier(struct xenbus_transaction xbt,
 217                      struct backend_info *be, int state)
 218 {
 219         struct xenbus_device *dev = be->dev;
 220         int err = xenbus_printf(xbt, dev->nodename, "feature-barrier",
 221                                 "%d", state);
 222
 223         if (err)
 224                 xenbus_dev_error(dev, err, "writing feature-barrier");
 225 }
 226
 227 void blkback_flush_diskcache(struct xenbus_transaction xbt,
 228                              struct backend_info *be, int state)
 229 {
 230         struct xenbus_device *dev = be->dev;
 231         int err = xenbus_printf(xbt, dev->nodename, "feature-flush-cache",
 232                                 "%d", state);
 233
 234         if (err)
 235                 xenbus_dev_error(dev, err, "writing feature-flush-cache");
 236 }
 237
 238 static void blkback_discard(struct xenbus_transaction xbt,
 239                             struct backend_info *be)
 240 {
 241         struct xenbus_device *dev = be->dev;
 242         struct vbd *vbd = &be->blkif->vbd;
 243         struct request_queue *q = bdev_get_queue(vbd->bdev);
 244         int err, state = 0;
 245
 246         if (blk_queue_discard(q)) {
 247                 err = xenbus_printf(xbt, dev->nodename, "discard-granularity",
 248                                     "%u", q->limits.discard_granularity);
 249                 if (!err)
 250                         state = 1;
 251                 else
 252                         xenbus_dev_error(dev, err,
 253                                          "writing discard-granularity");
 254                 err = xenbus_printf(xbt, dev->nodename, "discard-alignment",
 255                                     "%u", q->limits.discard_alignment);
 256                 if (err) {
 257                         xenbus_dev_error(dev, err,
 258                                          "writing discard-alignment");
 259                         state = 0;
 260                 }
 261         }
 262
 263         /* Optional. */
 264         if (state) {
 265                 err = xenbus_printf(xbt, dev->nodename, "discard-secure",
 266                                     "%d", vbd->discard_secure);
 267                 if (err)
 268                         xenbus_dev_error(dev, err, "writing discard-secure");
 269         }
 270
 271         err = xenbus_printf(xbt, dev->nodename, "feature-discard",
 272                             "%d", state);
 273         if (err)
 274                 xenbus_dev_error(dev, err, "writing feature-discard");
 275 }
 276
 277 /**
 278  * Entry point to this code when a new device is created.  Allocate the basic
 279  * structures, and watch the store waiting for the hotplug scripts to tell us
 280  * the device's physical major and minor numbers.  Switch to InitWait.
 281  */
 282 static int blkback_probe(struct xenbus_device *dev,
 283                          const struct xenbus_device_id *id)
 284 {
 285         int err;
 286         struct backend_info *be = kzalloc(sizeof(struct backend_info),
 287                                           GFP_KERNEL);
 288         if (!be) {
 289                 xenbus_dev_fatal(dev, -ENOMEM,
 290                                  "allocating backend structure");
 291                 return -ENOMEM;
 292         }
 293         be->dev = dev;
 294         dev_set_drvdata(&dev->dev, be);
 295
 296         be->blkif = blkif_alloc(dev->otherend_id);
 297         if (IS_ERR(be->blkif)) {
 298                 err = PTR_ERR(be->blkif);
 299                 be->blkif = NULL;
 300                 xenbus_dev_fatal(dev, err, "creating block interface");
 301                 goto fail;
 302         }
 303
 304         /* setup back pointer */
 305         be->blkif->be = be;
 306
 307         err = xenbus_watch_path2(dev, dev->nodename, "physical-device",
 308                                  &be->backend_watch, backend_changed);
 309         if (err)
 310                 goto fail;
 311
 312         err = xenbus_switch_state(dev, XenbusStateInitWait);
 313         if (err)
 314                 goto fail;
 315
 316         return 0;
 317
 318 fail:
 319         DPRINTK("failed");
 320         blkback_remove(dev);
 321         return err;
 322 }
 323
 324
 325 /**
 326  * Callback received when the hotplug scripts have placed the physical-device
 327  * node.  Read it and the mode node, and create a vbd.  If the frontend is
 328  * ready, connect.
 329  */
 330 static void backend_changed(struct xenbus_watch *watch,
 331                             const char **vec, unsigned int len)
 332 {
 333         int err;
 334         unsigned major;
 335         unsigned minor;
 336         struct backend_info *be
 337                 = container_of(watch, struct backend_info, backend_watch);
 338         struct xenbus_device *dev = be->dev;
 339         int cdrom = 0;
 340         char *device_type;
 341
 342         DPRINTK("");
 343
 344         err = xenbus_scanf(XBT_NIL, dev->nodename, "physical-device", "%x:%x",
 345                            &major, &minor);
 346         if (XENBUS_EXIST_ERR(err)) {
 347                 /* Since this watch will fire once immediately after it is
 348                    registered, we expect this.  Ignore it, and wait for the
 349                    hotplug scripts. */
 350                 return;
 351         }
 352         if (err != 2) {
 353                 xenbus_dev_fatal(dev, err, "reading physical-device");
 354                 return;
 355         }
 356
 357         if ((be->major || be->minor) &&
 358             ((be->major != major) || (be->minor != minor))) {
 359                 pr_warning("blkback: changing physical device (from %x:%x to"
 360                            " %x:%x) not supported\n", be->major, be->minor,
 361                            major, minor);
 362                 return;
 363         }
 364
 365         be->mode = xenbus_read(XBT_NIL, dev->nodename, "mode", NULL);
 366         if (IS_ERR(be->mode)) {
 367                 err = PTR_ERR(be->mode);
 368                 be->mode = NULL;
 369                 xenbus_dev_fatal(dev, err, "reading mode");
 370                 return;
 371         }
 372
 373         device_type = xenbus_read(XBT_NIL, dev->otherend, "device-type", NULL);
 374         if (!IS_ERR(device_type)) {
 375                 cdrom = strcmp(device_type, "cdrom") == 0;
 376                 kfree(device_type);
 377         }
 378
 379         if (be->major == 0 && be->minor == 0) {
 380                 /* Front end dir is a number, which is used as the handle. */
 381
 382                 char *p = strrchr(dev->otherend, '/') + 1;
 383                 long handle = simple_strtoul(p, NULL, 0);
 384
 385                 be->major = major;
 386                 be->minor = minor;
 387
 388                 err = vbd_create(be->blkif, handle, major, minor,
 389                                  FMODE_READ
 390                                  | (strchr(be->mode, 'w') ? FMODE_WRITE : 0)
 391                                  | (strchr(be->mode, '!') ? 0 : FMODE_EXCL),
 392                                  cdrom);
 393                 switch (err) {
 394                 case -ENOMEDIUM:
 395                         if (be->blkif->vbd.type
 396                             & (VDISK_CDROM | VDISK_REMOVABLE))
 397                 case 0:
 398                                 break;
 399                 default:
 400                         be->major = be->minor = 0;
 401                         xenbus_dev_fatal(dev, err, "creating vbd structure");
 402                         return;
 403                 }
 404
 405                 err = xenvbd_sysfs_addif(dev);
 406                 if (err) {
 407                         vbd_free(&be->blkif->vbd);
 408                         be->major = be->minor = 0;
 409                         xenbus_dev_fatal(dev, err, "creating sysfs entries");
 410                         return;
 411                 }
 412
 413                 /* We're potentially connected now */
 414                 update_blkif_status(be->blkif);
 415
 416                 /* Add watch for cdrom media status if necessay */
 417                 cdrom_add_media_watch(be);
 418         }
 419 }
 420
 421
 422 /**
 423  * Callback received when the frontend's state changes.
 424  */
 425 static void frontend_changed(struct xenbus_device *dev,
 426                              enum xenbus_state frontend_state)
 427 {
 428         struct backend_info *be = dev_get_drvdata(&dev->dev);
 429         int err;
 430
 431         DPRINTK("%s", xenbus_strstate(frontend_state));
 432
 433         switch (frontend_state) {
 434         case XenbusStateInitialising:
 435                 if (dev->state == XenbusStateClosed) {
 436                         pr_info("%s: %s: prepare for reconnect\n",
 437                                 __FUNCTION__, dev->nodename);
 438                         xenbus_switch_state(dev, XenbusStateInitWait);
 439                 }
 440                 break;
 441
 442         case XenbusStateInitialised:
 443         case XenbusStateConnected:
 444                 /* Ensure we connect even when two watches fire in
 445                    close successsion and we miss the intermediate value
 446                    of frontend_state. */
 447                 if (dev->state == XenbusStateConnected)
 448                         break;
 449
 450                 /* Enforce precondition before potential leak point.
 451                  * blkif_disconnect() is idempotent.
 452                  */
 453                 blkif_disconnect(be->blkif);
 454
 455                 err = connect_ring(be);
 456                 if (err)
 457                         break;
 458                 if (be->blkif->vbd.bdev)
 459                         update_blkif_status(be->blkif);
 460                 break;
 461
 462         case XenbusStateClosing:
 463         case XenbusStateClosed:
 464                 blkif_disconnect(be->blkif);
 465                 xenbus_switch_state(dev, frontend_state);
 466                 if (frontend_state != XenbusStateClosed ||
 467                     xenbus_dev_is_online(dev))
 468                         break;
 469                 /* fall through if not online */
 470         case XenbusStateUnknown:
 471                 /* implies blkif_disconnect() via blkback_remove() */
 472                 device_unregister(&dev->dev);
 473                 break;
 474
 475         default:
 476                 xenbus_dev_fatal(dev, -EINVAL, "saw state %d at frontend",
 477                                  frontend_state);
 478                 break;
 479         }
 480 }
 481
 482
 483 /* ** Connection ** */
 484
 485
 486 /**
 487  * Write the physical details regarding the block device to the store, and
 488  * switch to Connected state.
 489  */
 490 static void connect(struct backend_info *be)
 491 {
 492         struct xenbus_transaction xbt;
 493         int err;
 494         struct xenbus_device *dev = be->dev;
 495
 496         DPRINTK("%s", dev->otherend);
 497
 498         /* Supply the information about the device the frontend needs */
 499 again:
 500         err = xenbus_transaction_start(&xbt);
 501         if (err) {
 502                 xenbus_dev_fatal(dev, err, "starting transaction");
 503                 return;
 504         }
 505
 506         blkback_flush_diskcache(xbt, be, be->blkif->vbd.flush_support);
 507         blkback_barrier(xbt, be, be->blkif->vbd.flush_support);
 508         blkback_discard(xbt, be);
 509
 510         err = xenbus_printf(xbt, dev->nodename, "sectors", "%llu",
 511                             vbd_size(&be->blkif->vbd));
 512         if (err) {
 513                 xenbus_dev_fatal(dev, err, "writing %s/sectors",
 514                                  dev->nodename);
 515                 goto abort;
 516         }
 517
 518         /* FIXME: use a typename instead */
 519         err = xenbus_printf(xbt, dev->nodename, "info", "%u",
 520                             be->blkif->vbd.type);
 521         if (err) {
 522                 xenbus_dev_fatal(dev, err, "writing %s/info",
 523                                  dev->nodename);
 524                 goto abort;
 525         }
 526         err = xenbus_printf(xbt, dev->nodename, "sector-size", "%lu",
 527                             vbd_secsize(&be->blkif->vbd));
 528         if (err) {
 529                 xenbus_dev_fatal(dev, err, "writing %s/sector-size",
 530                                  dev->nodename);
 531                 goto abort;
 532         }
 533
 534         err = xenbus_transaction_end(xbt, 0);
 535         if (err == -EAGAIN)
 536                 goto again;
 537         if (err)
 538                 xenbus_dev_fatal(dev, err, "ending transaction");
 539
 540         err = xenbus_switch_state(dev, XenbusStateConnected);
 541         if (err)
 542                 xenbus_dev_fatal(dev, err, "%s: switching to Connected state",
 543                                  dev->nodename);
 544
 545         return;
 546  abort:
 547         xenbus_transaction_end(xbt, 1);
 548 }
 549
 550
 551 static int connect_ring(struct backend_info *be)
 552 {
 553         struct xenbus_device *dev = be->dev;
 554         unsigned int ring_ref, evtchn;
 555         char *protocol;
 556         int err;
 557
 558         DPRINTK("%s", dev->otherend);
 559
 560         err = xenbus_gather(XBT_NIL, dev->otherend, "ring-ref", "%u", &ring_ref,
 561                             "event-channel", "%u", &evtchn, NULL);
 562         if (err) {
 563                 xenbus_dev_fatal(dev, err,
 564                                  "reading %s/ring-ref and event-channel",
 565                                  dev->otherend);
 566                 return err;
 567         }
 568
 569         be->blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
 570         protocol = xenbus_read(XBT_NIL, dev->otherend, "protocol", NULL);
 571         if (IS_ERR(protocol)) {
 572                 protocol = NULL;
 573                 be->blkif->blk_protocol = xen_guest_blkif_protocol(be->blkif->domid);
 574 #ifndef CONFIG_X86_32
 575         } else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_32)) {
 576                 be->blkif->blk_protocol = BLKIF_PROTOCOL_X86_32;
 577 #endif
 578 #ifndef CONFIG_X86_64
 579         } else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_64)) {
 580                 be->blkif->blk_protocol = BLKIF_PROTOCOL_X86_64;
 581 #endif
 582         } else if (0 != strcmp(protocol, XEN_IO_PROTO_ABI_NATIVE)) {
 583                 xenbus_dev_fatal(dev, err, "unknown fe protocol %s", protocol);
 584                 kfree(protocol);
 585                 return -1;
 586         }
 587         pr_info("blkback: ring-ref %u, event-channel %u, protocol %d (%s)\n",
 588                 ring_ref, evtchn, be->blkif->blk_protocol,
 589                 protocol ?: "unspecified");
 590         kfree(protocol);
 591
 592         /* Map the shared frame, irq etc. */
 593         err = blkif_map(be->blkif, ring_ref, evtchn);
 594         if (err) {
 595                 xenbus_dev_fatal(dev, err, "mapping ring-ref %u port %u",
 596                                  ring_ref, evtchn);
 597                 return err;
 598         }
 599
 600         return 0;
 601 }
 602
 603
 604 /* ** Driver Registration ** */
 605
 606
 607 static const struct xenbus_device_id blkback_ids[] = {
 608         { "vbd" },
 609         { "" }
 610 };
 611
 612 static DEFINE_XENBUS_DRIVER(blkback, ,
 613         .probe = blkback_probe,
 614         .remove = blkback_remove,
 615         .otherend_changed = frontend_changed
 616 );
 617
 618
 619 void blkif_xenbus_init(void)
 620 {
 621         WARN_ON(xenbus_register_backend(&blkback_driver));
 622 }