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