drivers/block/xen-blkback/xenbus.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*  Xenbus code for blkif backend
   3     Copyright (C) 2005 Rusty Russell <rusty@rustcorp.com.au>
   4     Copyright (C) 2005 XenSource Ltd
   5
   6
   7 */
   8
   9 #define pr_fmt(fmt) "xen-blkback: " fmt
  10
  11 #include <stdarg.h>
  12 #include <linux/module.h>
  13 #include <linux/kthread.h>
  14 #include <xen/events.h>
  15 #include <xen/grant_table.h>
  16 #include "common.h"
  17
  18 /* On the XenBus the max length of 'ring-ref%u'. */
  19 #define RINGREF_NAME_LEN (20)
  20
  21 struct backend_info {
  22         struct xenbus_device    *dev;
  23         struct xen_blkif        *blkif;
  24         struct xenbus_watch     backend_watch;
  25         unsigned                major;
  26         unsigned                minor;
  27         char                    *mode;
  28 };
  29
  30 static struct kmem_cache *xen_blkif_cachep;
  31 static void connect(struct backend_info *);
  32 static int connect_ring(struct backend_info *);
  33 static void backend_changed(struct xenbus_watch *, const char *,
  34                             const char *);
  35 static void xen_blkif_free(struct xen_blkif *blkif);
  36 static void xen_vbd_free(struct xen_vbd *vbd);
  37
  38 struct xenbus_device *xen_blkbk_xenbus(struct backend_info *be)
  39 {
  40         return be->dev;
  41 }
  42
  43 /*
  44  * The last request could free the device from softirq context and
  45  * xen_blkif_free() can sleep.
  46  */
  47 static void xen_blkif_deferred_free(struct work_struct *work)
  48 {
  49         struct xen_blkif *blkif;
  50
  51         blkif = container_of(work, struct xen_blkif, free_work);
  52         xen_blkif_free(blkif);
  53 }
  54
  55 static int blkback_name(struct xen_blkif *blkif, char *buf)
  56 {
  57         char *devpath, *devname;
  58         struct xenbus_device *dev = blkif->be->dev;
  59
  60         devpath = xenbus_read(XBT_NIL, dev->nodename, "dev", NULL);
  61         if (IS_ERR(devpath))
  62                 return PTR_ERR(devpath);
  63
  64         devname = strstr(devpath, "/dev/");
  65         if (devname != NULL)
  66                 devname += strlen("/dev/");
  67         else
  68                 devname  = devpath;
  69
  70         snprintf(buf, TASK_COMM_LEN, "%d.%s", blkif->domid, devname);
  71         kfree(devpath);
  72
  73         return 0;
  74 }
  75
  76 static void xen_update_blkif_status(struct xen_blkif *blkif)
  77 {
  78         int err;
  79         char name[TASK_COMM_LEN];
  80         struct xen_blkif_ring *ring;
  81         int i;
  82
  83         /* Not ready to connect? */
  84         if (!blkif->rings || !blkif->rings[0].irq || !blkif->vbd.bdev)
  85                 return;
  86
  87         /* Already connected? */
  88         if (blkif->be->dev->state == XenbusStateConnected)
  89                 return;
  90
  91         /* Attempt to connect: exit if we fail to. */
  92         connect(blkif->be);
  93         if (blkif->be->dev->state != XenbusStateConnected)
  94                 return;
  95
  96         err = blkback_name(blkif, name);
  97         if (err) {
  98                 xenbus_dev_error(blkif->be->dev, err, "get blkback dev name");
  99                 return;
 100         }
 101
 102         err = filemap_write_and_wait(blkif->vbd.bdev->bd_inode->i_mapping);
 103         if (err) {
 104                 xenbus_dev_error(blkif->be->dev, err, "block flush");
 105                 return;
 106         }
 107         invalidate_inode_pages2(blkif->vbd.bdev->bd_inode->i_mapping);
 108
 109         for (i = 0; i < blkif->nr_rings; i++) {
 110                 ring = &blkif->rings[i];
 111                 ring->xenblkd = kthread_run(xen_blkif_schedule, ring, "%s-%d", name, i);
 112                 if (IS_ERR(ring->xenblkd)) {
 113                         err = PTR_ERR(ring->xenblkd);
 114                         ring->xenblkd = NULL;
 115                         xenbus_dev_fatal(blkif->be->dev, err,
 116                                         "start %s-%d xenblkd", name, i);
 117                         goto out;
 118                 }
 119         }
 120         return;
 121
 122 out:
 123         while (--i >= 0) {
 124                 ring = &blkif->rings[i];
 125                 kthread_stop(ring->xenblkd);
 126         }
 127         return;
 128 }
 129
 130 static int xen_blkif_alloc_rings(struct xen_blkif *blkif)
 131 {
 132         unsigned int r;
 133
 134         blkif->rings = kcalloc(blkif->nr_rings, sizeof(struct xen_blkif_ring),
 135                                GFP_KERNEL);
 136         if (!blkif->rings)
 137                 return -ENOMEM;
 138
 139         for (r = 0; r < blkif->nr_rings; r++) {
 140                 struct xen_blkif_ring *ring = &blkif->rings[r];
 141
 142                 spin_lock_init(&ring->blk_ring_lock);
 143                 init_waitqueue_head(&ring->wq);
 144                 INIT_LIST_HEAD(&ring->pending_free);
 145                 INIT_LIST_HEAD(&ring->persistent_purge_list);
 146                 INIT_WORK(&ring->persistent_purge_work, xen_blkbk_unmap_purged_grants);
 147                 spin_lock_init(&ring->free_pages_lock);
 148                 INIT_LIST_HEAD(&ring->free_pages);
 149
 150                 spin_lock_init(&ring->pending_free_lock);
 151                 init_waitqueue_head(&ring->pending_free_wq);
 152                 init_waitqueue_head(&ring->shutdown_wq);
 153                 ring->blkif = blkif;
 154                 ring->st_print = jiffies;
 155                 ring->active = true;
 156         }
 157
 158         return 0;
 159 }
 160
 161 static struct xen_blkif *xen_blkif_alloc(domid_t domid)
 162 {
 163         struct xen_blkif *blkif;
 164
 165         BUILD_BUG_ON(MAX_INDIRECT_PAGES > BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST);
 166
 167         blkif = kmem_cache_zalloc(xen_blkif_cachep, GFP_KERNEL);
 168         if (!blkif)
 169                 return ERR_PTR(-ENOMEM);
 170
 171         blkif->domid = domid;
 172         atomic_set(&blkif->refcnt, 1);
 173         init_completion(&blkif->drain_complete);
 174         INIT_WORK(&blkif->free_work, xen_blkif_deferred_free);
 175
 176         return blkif;
 177 }
 178
 179 static int xen_blkif_map(struct xen_blkif_ring *ring, grant_ref_t *gref,
 180                          unsigned int nr_grefs, unsigned int evtchn)
 181 {
 182         int err;
 183         struct xen_blkif *blkif = ring->blkif;
 184
 185         /* Already connected through? */
 186         if (ring->irq)
 187                 return 0;
 188
 189         err = xenbus_map_ring_valloc(blkif->be->dev, gref, nr_grefs,
 190                                      &ring->blk_ring);
 191         if (err < 0)
 192                 return err;
 193
 194         switch (blkif->blk_protocol) {
 195         case BLKIF_PROTOCOL_NATIVE:
 196         {
 197                 struct blkif_sring *sring;
 198                 sring = (struct blkif_sring *)ring->blk_ring;
 199                 BACK_RING_INIT(&ring->blk_rings.native, sring,
 200                                XEN_PAGE_SIZE * nr_grefs);
 201                 break;
 202         }
 203         case BLKIF_PROTOCOL_X86_32:
 204         {
 205                 struct blkif_x86_32_sring *sring_x86_32;
 206                 sring_x86_32 = (struct blkif_x86_32_sring *)ring->blk_ring;
 207                 BACK_RING_INIT(&ring->blk_rings.x86_32, sring_x86_32,
 208                                XEN_PAGE_SIZE * nr_grefs);
 209                 break;
 210         }
 211         case BLKIF_PROTOCOL_X86_64:
 212         {
 213                 struct blkif_x86_64_sring *sring_x86_64;
 214                 sring_x86_64 = (struct blkif_x86_64_sring *)ring->blk_ring;
 215                 BACK_RING_INIT(&ring->blk_rings.x86_64, sring_x86_64,
 216                                XEN_PAGE_SIZE * nr_grefs);
 217                 break;
 218         }
 219         default:
 220                 BUG();
 221         }
 222
 223         err = bind_interdomain_evtchn_to_irqhandler(blkif->domid, evtchn,
 224                                                     xen_blkif_be_int, 0,
 225                                                     "blkif-backend", ring);
 226         if (err < 0) {
 227                 xenbus_unmap_ring_vfree(blkif->be->dev, ring->blk_ring);
 228                 ring->blk_rings.common.sring = NULL;
 229                 return err;
 230         }
 231         ring->irq = err;
 232
 233         return 0;
 234 }
 235
 236 static int xen_blkif_disconnect(struct xen_blkif *blkif)
 237 {
 238         struct pending_req *req, *n;
 239         unsigned int j, r;
 240         bool busy = false;
 241
 242         for (r = 0; r < blkif->nr_rings; r++) {
 243                 struct xen_blkif_ring *ring = &blkif->rings[r];
 244                 unsigned int i = 0;
 245
 246                 if (!ring->active)
 247                         continue;
 248
 249                 if (ring->xenblkd) {
 250                         kthread_stop(ring->xenblkd);
 251                         wake_up(&ring->shutdown_wq);
 252                 }
 253
 254                 /* The above kthread_stop() guarantees that at this point we
 255                  * don't have any discard_io or other_io requests. So, checking
 256                  * for inflight IO is enough.
 257                  */
 258                 if (atomic_read(&ring->inflight) > 0) {
 259                         busy = true;
 260                         continue;
 261                 }
 262
 263                 if (ring->irq) {
 264                         unbind_from_irqhandler(ring->irq, ring);
 265                         ring->irq = 0;
 266                 }
 267
 268                 if (ring->blk_rings.common.sring) {
 269                         xenbus_unmap_ring_vfree(blkif->be->dev, ring->blk_ring);
 270                         ring->blk_rings.common.sring = NULL;
 271                 }
 272
 273                 /* Remove all persistent grants and the cache of ballooned pages. */
 274                 xen_blkbk_free_caches(ring);
 275
 276                 /* Check that there is no request in use */
 277                 list_for_each_entry_safe(req, n, &ring->pending_free, free_list) {
 278                         list_del(&req->free_list);
 279
 280                         for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++)
 281                                 kfree(req->segments[j]);
 282
 283                         for (j = 0; j < MAX_INDIRECT_PAGES; j++)
 284                                 kfree(req->indirect_pages[j]);
 285
 286                         kfree(req);
 287                         i++;
 288                 }
 289
 290                 BUG_ON(atomic_read(&ring->persistent_gnt_in_use) != 0);
 291                 BUG_ON(!list_empty(&ring->persistent_purge_list));
 292                 BUG_ON(!RB_EMPTY_ROOT(&ring->persistent_gnts));
 293                 BUG_ON(!list_empty(&ring->free_pages));
 294                 BUG_ON(ring->free_pages_num != 0);
 295                 BUG_ON(ring->persistent_gnt_c != 0);
 296                 WARN_ON(i != (XEN_BLKIF_REQS_PER_PAGE * blkif->nr_ring_pages));
 297                 ring->active = false;
 298         }
 299         if (busy)
 300                 return -EBUSY;
 301
 302         blkif->nr_ring_pages = 0;
 303         /*
 304          * blkif->rings was allocated in connect_ring, so we should free it in
 305          * here.
 306          */
 307         kfree(blkif->rings);
 308         blkif->rings = NULL;
 309         blkif->nr_rings = 0;
 310
 311         return 0;
 312 }
 313
 314 static void xen_blkif_free(struct xen_blkif *blkif)
 315 {
 316         WARN_ON(xen_blkif_disconnect(blkif));
 317         xen_vbd_free(&blkif->vbd);
 318         kfree(blkif->be->mode);
 319         kfree(blkif->be);
 320
 321         /* Make sure everything is drained before shutting down */
 322         kmem_cache_free(xen_blkif_cachep, blkif);
 323 }
 324
 325 int __init xen_blkif_interface_init(void)
 326 {
 327         xen_blkif_cachep = kmem_cache_create("blkif_cache",
 328                                              sizeof(struct xen_blkif),
 329                                              0, 0, NULL);
 330         if (!xen_blkif_cachep)
 331                 return -ENOMEM;
 332
 333         return 0;
 334 }
 335
 336 /*
 337  *  sysfs interface for VBD I/O requests
 338  */
 339
 340 #define VBD_SHOW_ALLRING(name, format)                                  \
 341         static ssize_t show_##name(struct device *_dev,                 \
 342                                    struct device_attribute *attr,       \
 343                                    char *buf)                           \
 344         {                                                               \
 345                 struct xenbus_device *dev = to_xenbus_device(_dev);     \
 346                 struct backend_info *be = dev_get_drvdata(&dev->dev);   \
 347                 struct xen_blkif *blkif = be->blkif;                    \
 348                 unsigned int i;                                         \
 349                 unsigned long long result = 0;                          \
 350                                                                         \
 351                 if (!blkif->rings)                              \
 352                         goto out;                                       \
 353                                                                         \
 354                 for (i = 0; i < blkif->nr_rings; i++) {         \
 355                         struct xen_blkif_ring *ring = &blkif->rings[i]; \
 356                                                                         \
 357                         result += ring->st_##name;                      \
 358                 }                                                       \
 359                                                                         \
 360 out:                                                                    \
 361                 return sprintf(buf, format, result);                    \
 362         }                                                               \
 363         static DEVICE_ATTR(name, 0444, show_##name, NULL)
 364
 365 VBD_SHOW_ALLRING(oo_req,  "%llu\n");
 366 VBD_SHOW_ALLRING(rd_req,  "%llu\n");
 367 VBD_SHOW_ALLRING(wr_req,  "%llu\n");
 368 VBD_SHOW_ALLRING(f_req,  "%llu\n");
 369 VBD_SHOW_ALLRING(ds_req,  "%llu\n");
 370 VBD_SHOW_ALLRING(rd_sect, "%llu\n");
 371 VBD_SHOW_ALLRING(wr_sect, "%llu\n");
 372
 373 static struct attribute *xen_vbdstat_attrs[] = {
 374         &dev_attr_oo_req.attr,
 375         &dev_attr_rd_req.attr,
 376         &dev_attr_wr_req.attr,
 377         &dev_attr_f_req.attr,
 378         &dev_attr_ds_req.attr,
 379         &dev_attr_rd_sect.attr,
 380         &dev_attr_wr_sect.attr,
 381         NULL
 382 };
 383
 384 static const struct attribute_group xen_vbdstat_group = {
 385         .name = "statistics",
 386         .attrs = xen_vbdstat_attrs,
 387 };
 388
 389 #define VBD_SHOW(name, format, args...)                                 \
 390         static ssize_t show_##name(struct device *_dev,                 \
 391                                    struct device_attribute *attr,       \
 392                                    char *buf)                           \
 393         {                                                               \
 394                 struct xenbus_device *dev = to_xenbus_device(_dev);     \
 395                 struct backend_info *be = dev_get_drvdata(&dev->dev);   \
 396                                                                         \
 397                 return sprintf(buf, format, ##args);                    \
 398         }                                                               \
 399         static DEVICE_ATTR(name, 0444, show_##name, NULL)
 400
 401 VBD_SHOW(physical_device, "%x:%x\n", be->major, be->minor);
 402 VBD_SHOW(mode, "%s\n", be->mode);
 403
 404 static int xenvbd_sysfs_addif(struct xenbus_device *dev)
 405 {
 406         int error;
 407
 408         error = device_create_file(&dev->dev, &dev_attr_physical_device);
 409         if (error)
 410                 goto fail1;
 411
 412         error = device_create_file(&dev->dev, &dev_attr_mode);
 413         if (error)
 414                 goto fail2;
 415
 416         error = sysfs_create_group(&dev->dev.kobj, &xen_vbdstat_group);
 417         if (error)
 418                 goto fail3;
 419
 420         return 0;
 421
 422 fail3:  sysfs_remove_group(&dev->dev.kobj, &xen_vbdstat_group);
 423 fail2:  device_remove_file(&dev->dev, &dev_attr_mode);
 424 fail1:  device_remove_file(&dev->dev, &dev_attr_physical_device);
 425         return error;
 426 }
 427
 428 static void xenvbd_sysfs_delif(struct xenbus_device *dev)
 429 {
 430         sysfs_remove_group(&dev->dev.kobj, &xen_vbdstat_group);
 431         device_remove_file(&dev->dev, &dev_attr_mode);
 432         device_remove_file(&dev->dev, &dev_attr_physical_device);
 433 }
 434
 435
 436 static void xen_vbd_free(struct xen_vbd *vbd)
 437 {
 438         if (vbd->bdev)
 439                 blkdev_put(vbd->bdev, vbd->readonly ? FMODE_READ : FMODE_WRITE);
 440         vbd->bdev = NULL;
 441 }
 442
 443 static int xen_vbd_create(struct xen_blkif *blkif, blkif_vdev_t handle,
 444                           unsigned major, unsigned minor, int readonly,
 445                           int cdrom)
 446 {
 447         struct xen_vbd *vbd;
 448         struct block_device *bdev;
 449         struct request_queue *q;
 450
 451         vbd = &blkif->vbd;
 452         vbd->handle   = handle;
 453         vbd->readonly = readonly;
 454         vbd->type     = 0;
 455
 456         vbd->pdevice  = MKDEV(major, minor);
 457
 458         bdev = blkdev_get_by_dev(vbd->pdevice, vbd->readonly ?
 459                                  FMODE_READ : FMODE_WRITE, NULL);
 460
 461         if (IS_ERR(bdev)) {
 462                 pr_warn("xen_vbd_create: device %08x could not be opened\n",
 463                         vbd->pdevice);
 464                 return -ENOENT;
 465         }
 466
 467         vbd->bdev = bdev;
 468         if (vbd->bdev->bd_disk == NULL) {
 469                 pr_warn("xen_vbd_create: device %08x doesn't exist\n",
 470                         vbd->pdevice);
 471                 xen_vbd_free(vbd);
 472                 return -ENOENT;
 473         }
 474         vbd->size = vbd_sz(vbd);
 475
 476         if (vbd->bdev->bd_disk->flags & GENHD_FL_CD || cdrom)
 477                 vbd->type |= VDISK_CDROM;
 478         if (vbd->bdev->bd_disk->flags & GENHD_FL_REMOVABLE)
 479                 vbd->type |= VDISK_REMOVABLE;
 480
 481         q = bdev_get_queue(bdev);
 482         if (q && test_bit(QUEUE_FLAG_WC, &q->queue_flags))
 483                 vbd->flush_support = true;
 484
 485         if (q && blk_queue_secure_erase(q))
 486                 vbd->discard_secure = true;
 487
 488         pr_debug("Successful creation of handle=%04x (dom=%u)\n",
 489                 handle, blkif->domid);
 490         return 0;
 491 }
 492 static int xen_blkbk_remove(struct xenbus_device *dev)
 493 {
 494         struct backend_info *be = dev_get_drvdata(&dev->dev);
 495
 496         pr_debug("%s %p %d\n", __func__, dev, dev->otherend_id);
 497
 498         if (be->major || be->minor)
 499                 xenvbd_sysfs_delif(dev);
 500
 501         if (be->backend_watch.node) {
 502                 unregister_xenbus_watch(&be->backend_watch);
 503                 kfree(be->backend_watch.node);
 504                 be->backend_watch.node = NULL;
 505         }
 506
 507         dev_set_drvdata(&dev->dev, NULL);
 508
 509         if (be->blkif) {
 510                 xen_blkif_disconnect(be->blkif);
 511
 512                 /* Put the reference we set in xen_blkif_alloc(). */
 513                 xen_blkif_put(be->blkif);
 514         }
 515
 516         return 0;
 517 }
 518
 519 int xen_blkbk_flush_diskcache(struct xenbus_transaction xbt,
 520                               struct backend_info *be, int state)
 521 {
 522         struct xenbus_device *dev = be->dev;
 523         int err;
 524
 525         err = xenbus_printf(xbt, dev->nodename, "feature-flush-cache",
 526                             "%d", state);
 527         if (err)
 528                 dev_warn(&dev->dev, "writing feature-flush-cache (%d)", err);
 529
 530         return err;
 531 }
 532
 533 static void xen_blkbk_discard(struct xenbus_transaction xbt, struct backend_info *be)
 534 {
 535         struct xenbus_device *dev = be->dev;
 536         struct xen_blkif *blkif = be->blkif;
 537         int err;
 538         int state = 0;
 539         struct block_device *bdev = be->blkif->vbd.bdev;
 540         struct request_queue *q = bdev_get_queue(bdev);
 541
 542         if (!xenbus_read_unsigned(dev->nodename, "discard-enable", 1))
 543                 return;
 544
 545         if (blk_queue_discard(q)) {
 546                 err = xenbus_printf(xbt, dev->nodename,
 547                         "discard-granularity", "%u",
 548                         q->limits.discard_granularity);
 549                 if (err) {
 550                         dev_warn(&dev->dev, "writing discard-granularity (%d)", err);
 551                         return;
 552                 }
 553                 err = xenbus_printf(xbt, dev->nodename,
 554                         "discard-alignment", "%u",
 555                         q->limits.discard_alignment);
 556                 if (err) {
 557                         dev_warn(&dev->dev, "writing discard-alignment (%d)", err);
 558                         return;
 559                 }
 560                 state = 1;
 561                 /* Optional. */
 562                 err = xenbus_printf(xbt, dev->nodename,
 563                                     "discard-secure", "%d",
 564                                     blkif->vbd.discard_secure);
 565                 if (err) {
 566                         dev_warn(&dev->dev, "writing discard-secure (%d)", err);
 567                         return;
 568                 }
 569         }
 570         err = xenbus_printf(xbt, dev->nodename, "feature-discard",
 571                             "%d", state);
 572         if (err)
 573                 dev_warn(&dev->dev, "writing feature-discard (%d)", err);
 574 }
 575 int xen_blkbk_barrier(struct xenbus_transaction xbt,
 576                       struct backend_info *be, int state)
 577 {
 578         struct xenbus_device *dev = be->dev;
 579         int err;
 580
 581         err = xenbus_printf(xbt, dev->nodename, "feature-barrier",
 582                             "%d", state);
 583         if (err)
 584                 dev_warn(&dev->dev, "writing feature-barrier (%d)", err);
 585
 586         return err;
 587 }
 588
 589 /*
 590  * Entry point to this code when a new device is created.  Allocate the basic
 591  * structures, and watch the store waiting for the hotplug scripts to tell us
 592  * the device's physical major and minor numbers.  Switch to InitWait.
 593  */
 594 static int xen_blkbk_probe(struct xenbus_device *dev,
 595                            const struct xenbus_device_id *id)
 596 {
 597         int err;
 598         struct backend_info *be = kzalloc(sizeof(struct backend_info),
 599                                           GFP_KERNEL);
 600
 601         /* match the pr_debug in xen_blkbk_remove */
 602         pr_debug("%s %p %d\n", __func__, dev, dev->otherend_id);
 603
 604         if (!be) {
 605                 xenbus_dev_fatal(dev, -ENOMEM,
 606                                  "allocating backend structure");
 607                 return -ENOMEM;
 608         }
 609         be->dev = dev;
 610         dev_set_drvdata(&dev->dev, be);
 611
 612         be->blkif = xen_blkif_alloc(dev->otherend_id);
 613         if (IS_ERR(be->blkif)) {
 614                 err = PTR_ERR(be->blkif);
 615                 be->blkif = NULL;
 616                 xenbus_dev_fatal(dev, err, "creating block interface");
 617                 goto fail;
 618         }
 619
 620         err = xenbus_printf(XBT_NIL, dev->nodename,
 621                             "feature-max-indirect-segments", "%u",
 622                             MAX_INDIRECT_SEGMENTS);
 623         if (err)
 624                 dev_warn(&dev->dev,
 625                          "writing %s/feature-max-indirect-segments (%d)",
 626                          dev->nodename, err);
 627
 628         /* Multi-queue: advertise how many queues are supported by us.*/
 629         err = xenbus_printf(XBT_NIL, dev->nodename,
 630                             "multi-queue-max-queues", "%u", xenblk_max_queues);
 631         if (err)
 632                 pr_warn("Error writing multi-queue-max-queues\n");
 633
 634         /* setup back pointer */
 635         be->blkif->be = be;
 636
 637         err = xenbus_watch_pathfmt(dev, &be->backend_watch, backend_changed,
 638                                    "%s/%s", dev->nodename, "physical-device");
 639         if (err)
 640                 goto fail;
 641
 642         err = xenbus_printf(XBT_NIL, dev->nodename, "max-ring-page-order", "%u",
 643                             xen_blkif_max_ring_order);
 644         if (err)
 645                 pr_warn("%s write out 'max-ring-page-order' failed\n", __func__);
 646
 647         err = xenbus_switch_state(dev, XenbusStateInitWait);
 648         if (err)
 649                 goto fail;
 650
 651         return 0;
 652
 653 fail:
 654         pr_warn("%s failed\n", __func__);
 655         xen_blkbk_remove(dev);
 656         return err;
 657 }
 658
 659
 660 /*
 661  * Callback received when the hotplug scripts have placed the physical-device
 662  * node.  Read it and the mode node, and create a vbd.  If the frontend is
 663  * ready, connect.
 664  */
 665 static void backend_changed(struct xenbus_watch *watch,
 666                             const char *path, const char *token)
 667 {
 668         int err;
 669         unsigned major;
 670         unsigned minor;
 671         struct backend_info *be
 672                 = container_of(watch, struct backend_info, backend_watch);
 673         struct xenbus_device *dev = be->dev;
 674         int cdrom = 0;
 675         unsigned long handle;
 676         char *device_type;
 677
 678         pr_debug("%s %p %d\n", __func__, dev, dev->otherend_id);
 679
 680         err = xenbus_scanf(XBT_NIL, dev->nodename, "physical-device", "%x:%x",
 681                            &major, &minor);
 682         if (XENBUS_EXIST_ERR(err)) {
 683                 /*
 684                  * Since this watch will fire once immediately after it is
 685                  * registered, we expect this.  Ignore it, and wait for the
 686                  * hotplug scripts.
 687                  */
 688                 return;
 689         }
 690         if (err != 2) {
 691                 xenbus_dev_fatal(dev, err, "reading physical-device");
 692                 return;
 693         }
 694
 695         if (be->major | be->minor) {
 696                 if (be->major != major || be->minor != minor)
 697                         pr_warn("changing physical device (from %x:%x to %x:%x) not supported.\n",
 698                                 be->major, be->minor, major, minor);
 699                 return;
 700         }
 701
 702         be->mode = xenbus_read(XBT_NIL, dev->nodename, "mode", NULL);
 703         if (IS_ERR(be->mode)) {
 704                 err = PTR_ERR(be->mode);
 705                 be->mode = NULL;
 706                 xenbus_dev_fatal(dev, err, "reading mode");
 707                 return;
 708         }
 709
 710         device_type = xenbus_read(XBT_NIL, dev->otherend, "device-type", NULL);
 711         if (!IS_ERR(device_type)) {
 712                 cdrom = strcmp(device_type, "cdrom") == 0;
 713                 kfree(device_type);
 714         }
 715
 716         /* Front end dir is a number, which is used as the handle. */
 717         err = kstrtoul(strrchr(dev->otherend, '/') + 1, 0, &handle);
 718         if (err) {
 719                 kfree(be->mode);
 720                 be->mode = NULL;
 721                 return;
 722         }
 723
 724         be->major = major;
 725         be->minor = minor;
 726
 727         err = xen_vbd_create(be->blkif, handle, major, minor,
 728                              !strchr(be->mode, 'w'), cdrom);
 729
 730         if (err)
 731                 xenbus_dev_fatal(dev, err, "creating vbd structure");
 732         else {
 733                 err = xenvbd_sysfs_addif(dev);
 734                 if (err) {
 735                         xen_vbd_free(&be->blkif->vbd);
 736                         xenbus_dev_fatal(dev, err, "creating sysfs entries");
 737                 }
 738         }
 739
 740         if (err) {
 741                 kfree(be->mode);
 742                 be->mode = NULL;
 743                 be->major = 0;
 744                 be->minor = 0;
 745         } else {
 746                 /* We're potentially connected now */
 747                 xen_update_blkif_status(be->blkif);
 748         }
 749 }
 750
 751
 752 /*
 753  * Callback received when the frontend's state changes.
 754  */
 755 static void frontend_changed(struct xenbus_device *dev,
 756                              enum xenbus_state frontend_state)
 757 {
 758         struct backend_info *be = dev_get_drvdata(&dev->dev);
 759         int err;
 760
 761         pr_debug("%s %p %s\n", __func__, dev, xenbus_strstate(frontend_state));
 762
 763         switch (frontend_state) {
 764         case XenbusStateInitialising:
 765                 if (dev->state == XenbusStateClosed) {
 766                         pr_info("%s: prepare for reconnect\n", dev->nodename);
 767                         xenbus_switch_state(dev, XenbusStateInitWait);
 768                 }
 769                 break;
 770
 771         case XenbusStateInitialised:
 772         case XenbusStateConnected:
 773                 /*
 774                  * Ensure we connect even when two watches fire in
 775                  * close succession and we miss the intermediate value
 776                  * of frontend_state.
 777                  */
 778                 if (dev->state == XenbusStateConnected)
 779                         break;
 780
 781                 /*
 782                  * Enforce precondition before potential leak point.
 783                  * xen_blkif_disconnect() is idempotent.
 784                  */
 785                 err = xen_blkif_disconnect(be->blkif);
 786                 if (err) {
 787                         xenbus_dev_fatal(dev, err, "pending I/O");
 788                         break;
 789                 }
 790
 791                 err = connect_ring(be);
 792                 if (err) {
 793                         /*
 794                          * Clean up so that memory resources can be used by
 795                          * other devices. connect_ring reported already error.
 796                          */
 797                         xen_blkif_disconnect(be->blkif);
 798                         break;
 799                 }
 800                 xen_update_blkif_status(be->blkif);
 801                 break;
 802
 803         case XenbusStateClosing:
 804                 xenbus_switch_state(dev, XenbusStateClosing);
 805                 break;
 806
 807         case XenbusStateClosed:
 808                 xen_blkif_disconnect(be->blkif);
 809                 xenbus_switch_state(dev, XenbusStateClosed);
 810                 if (xenbus_dev_is_online(dev))
 811                         break;
 812                 /* fall through */
 813                 /* if not online */
 814         case XenbusStateUnknown:
 815                 /* implies xen_blkif_disconnect() via xen_blkbk_remove() */
 816                 device_unregister(&dev->dev);
 817                 break;
 818
 819         default:
 820                 xenbus_dev_fatal(dev, -EINVAL, "saw state %d at frontend",
 821                                  frontend_state);
 822                 break;
 823         }
 824 }
 825
 826
 827 /* ** Connection ** */
 828
 829
 830 /*
 831  * Write the physical details regarding the block device to the store, and
 832  * switch to Connected state.
 833  */
 834 static void connect(struct backend_info *be)
 835 {
 836         struct xenbus_transaction xbt;
 837         int err;
 838         struct xenbus_device *dev = be->dev;
 839
 840         pr_debug("%s %s\n", __func__, dev->otherend);
 841
 842         /* Supply the information about the device the frontend needs */
 843 again:
 844         err = xenbus_transaction_start(&xbt);
 845         if (err) {
 846                 xenbus_dev_fatal(dev, err, "starting transaction");
 847                 return;
 848         }
 849
 850         /* If we can't advertise it is OK. */
 851         xen_blkbk_flush_diskcache(xbt, be, be->blkif->vbd.flush_support);
 852
 853         xen_blkbk_discard(xbt, be);
 854
 855         xen_blkbk_barrier(xbt, be, be->blkif->vbd.flush_support);
 856
 857         err = xenbus_printf(xbt, dev->nodename, "feature-persistent", "%u", 1);
 858         if (err) {
 859                 xenbus_dev_fatal(dev, err, "writing %s/feature-persistent",
 860                                  dev->nodename);
 861                 goto abort;
 862         }
 863
 864         err = xenbus_printf(xbt, dev->nodename, "sectors", "%llu",
 865                             (unsigned long long)vbd_sz(&be->blkif->vbd));
 866         if (err) {
 867                 xenbus_dev_fatal(dev, err, "writing %s/sectors",
 868                                  dev->nodename);
 869                 goto abort;
 870         }
 871
 872         /* FIXME: use a typename instead */
 873         err = xenbus_printf(xbt, dev->nodename, "info", "%u",
 874                             be->blkif->vbd.type |
 875                             (be->blkif->vbd.readonly ? VDISK_READONLY : 0));
 876         if (err) {
 877                 xenbus_dev_fatal(dev, err, "writing %s/info",
 878                                  dev->nodename);
 879                 goto abort;
 880         }
 881         err = xenbus_printf(xbt, dev->nodename, "sector-size", "%lu",
 882                             (unsigned long)
 883                             bdev_logical_block_size(be->blkif->vbd.bdev));
 884         if (err) {
 885                 xenbus_dev_fatal(dev, err, "writing %s/sector-size",
 886                                  dev->nodename);
 887                 goto abort;
 888         }
 889         err = xenbus_printf(xbt, dev->nodename, "physical-sector-size", "%u",
 890                             bdev_physical_block_size(be->blkif->vbd.bdev));
 891         if (err)
 892                 xenbus_dev_error(dev, err, "writing %s/physical-sector-size",
 893                                  dev->nodename);
 894
 895         err = xenbus_transaction_end(xbt, 0);
 896         if (err == -EAGAIN)
 897                 goto again;
 898         if (err)
 899                 xenbus_dev_fatal(dev, err, "ending transaction");
 900
 901         err = xenbus_switch_state(dev, XenbusStateConnected);
 902         if (err)
 903                 xenbus_dev_fatal(dev, err, "%s: switching to Connected state",
 904                                  dev->nodename);
 905
 906         return;
 907  abort:
 908         xenbus_transaction_end(xbt, 1);
 909 }
 910
 911 /*
 912  * Each ring may have multi pages, depends on "ring-page-order".
 913  */
 914 static int read_per_ring_refs(struct xen_blkif_ring *ring, const char *dir)
 915 {
 916         unsigned int ring_ref[XENBUS_MAX_RING_GRANTS];
 917         struct pending_req *req, *n;
 918         int err, i, j;
 919         struct xen_blkif *blkif = ring->blkif;
 920         struct xenbus_device *dev = blkif->be->dev;
 921         unsigned int nr_grefs, evtchn;
 922
 923         err = xenbus_scanf(XBT_NIL, dir, "event-channel", "%u",
 924                           &evtchn);
 925         if (err != 1) {
 926                 err = -EINVAL;
 927                 xenbus_dev_fatal(dev, err, "reading %s/event-channel", dir);
 928                 return err;
 929         }
 930
 931         nr_grefs = blkif->nr_ring_pages;
 932
 933         if (unlikely(!nr_grefs)) {
 934                 WARN_ON(true);
 935                 return -EINVAL;
 936         }
 937
 938         for (i = 0; i < nr_grefs; i++) {
 939                 char ring_ref_name[RINGREF_NAME_LEN];
 940
 941                 snprintf(ring_ref_name, RINGREF_NAME_LEN, "ring-ref%u", i);
 942                 err = xenbus_scanf(XBT_NIL, dir, ring_ref_name,
 943                                    "%u", &ring_ref[i]);
 944
 945                 if (err != 1) {
 946                         if (nr_grefs == 1)
 947                                 break;
 948
 949                         err = -EINVAL;
 950                         xenbus_dev_fatal(dev, err, "reading %s/%s",
 951                                          dir, ring_ref_name);
 952                         return err;
 953                 }
 954         }
 955
 956         if (err != 1) {
 957                 WARN_ON(nr_grefs != 1);
 958
 959                 err = xenbus_scanf(XBT_NIL, dir, "ring-ref", "%u",
 960                                    &ring_ref[0]);
 961                 if (err != 1) {
 962                         err = -EINVAL;
 963                         xenbus_dev_fatal(dev, err, "reading %s/ring-ref", dir);
 964                         return err;
 965                 }
 966         }
 967
 968         err = -ENOMEM;
 969         for (i = 0; i < nr_grefs * XEN_BLKIF_REQS_PER_PAGE; i++) {
 970                 req = kzalloc(sizeof(*req), GFP_KERNEL);
 971                 if (!req)
 972                         goto fail;
 973                 list_add_tail(&req->free_list, &ring->pending_free);
 974                 for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++) {
 975                         req->segments[j] = kzalloc(sizeof(*req->segments[0]), GFP_KERNEL);
 976                         if (!req->segments[j])
 977                                 goto fail;
 978                 }
 979                 for (j = 0; j < MAX_INDIRECT_PAGES; j++) {
 980                         req->indirect_pages[j] = kzalloc(sizeof(*req->indirect_pages[0]),
 981                                                          GFP_KERNEL);
 982                         if (!req->indirect_pages[j])
 983                                 goto fail;
 984                 }
 985         }
 986
 987         /* Map the shared frame, irq etc. */
 988         err = xen_blkif_map(ring, ring_ref, nr_grefs, evtchn);
 989         if (err) {
 990                 xenbus_dev_fatal(dev, err, "mapping ring-ref port %u", evtchn);
 991                 goto fail;
 992         }
 993
 994         return 0;
 995
 996 fail:
 997         list_for_each_entry_safe(req, n, &ring->pending_free, free_list) {
 998                 list_del(&req->free_list);
 999                 for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++) {
1000                         if (!req->segments[j])
1001                                 break;
1002                         kfree(req->segments[j]);
1003                 }
1004                 for (j = 0; j < MAX_INDIRECT_PAGES; j++) {
1005                         if (!req->indirect_pages[j])
1006                                 break;
1007                         kfree(req->indirect_pages[j]);
1008                 }
1009                 kfree(req);
1010         }
1011         return err;
1012 }
1013
1014 static int connect_ring(struct backend_info *be)
1015 {
1016         struct xenbus_device *dev = be->dev;
1017         struct xen_blkif *blkif = be->blkif;
1018         unsigned int pers_grants;
1019         char protocol[64] = "";
1020         int err, i;
1021         char *xspath;
1022         size_t xspathsize;
1023         const size_t xenstore_path_ext_size = 11; /* sufficient for "/queue-NNN" */
1024         unsigned int requested_num_queues = 0;
1025         unsigned int ring_page_order;
1026
1027         pr_debug("%s %s\n", __func__, dev->otherend);
1028
1029         blkif->blk_protocol = BLKIF_PROTOCOL_DEFAULT;
1030         err = xenbus_scanf(XBT_NIL, dev->otherend, "protocol",
1031                            "%63s", protocol);
1032         if (err <= 0)
1033                 strcpy(protocol, "unspecified, assuming default");
1034         else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_NATIVE))
1035                 blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
1036         else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_32))
1037                 blkif->blk_protocol = BLKIF_PROTOCOL_X86_32;
1038         else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_64))
1039                 blkif->blk_protocol = BLKIF_PROTOCOL_X86_64;
1040         else {
1041                 xenbus_dev_fatal(dev, err, "unknown fe protocol %s", protocol);
1042                 return -ENOSYS;
1043         }
1044         pers_grants = xenbus_read_unsigned(dev->otherend, "feature-persistent",
1045                                            0);
1046         blkif->vbd.feature_gnt_persistent = pers_grants;
1047         blkif->vbd.overflow_max_grants = 0;
1048
1049         /*
1050          * Read the number of hardware queues from frontend.
1051          */
1052         requested_num_queues = xenbus_read_unsigned(dev->otherend,
1053                                                     "multi-queue-num-queues",
1054                                                     1);
1055         if (requested_num_queues > xenblk_max_queues
1056             || requested_num_queues == 0) {
1057                 /* Buggy or malicious guest. */
1058                 xenbus_dev_fatal(dev, err,
1059                                 "guest requested %u queues, exceeding the maximum of %u.",
1060                                 requested_num_queues, xenblk_max_queues);
1061                 return -ENOSYS;
1062         }
1063         blkif->nr_rings = requested_num_queues;
1064         if (xen_blkif_alloc_rings(blkif))
1065                 return -ENOMEM;
1066
1067         pr_info("%s: using %d queues, protocol %d (%s) %s\n", dev->nodename,
1068                  blkif->nr_rings, blkif->blk_protocol, protocol,
1069                  pers_grants ? "persistent grants" : "");
1070
1071         ring_page_order = xenbus_read_unsigned(dev->otherend,
1072                                                "ring-page-order", 0);
1073
1074         if (ring_page_order > xen_blkif_max_ring_order) {
1075                 err = -EINVAL;
1076                 xenbus_dev_fatal(dev, err,
1077                                  "requested ring page order %d exceed max:%d",
1078                                  ring_page_order,
1079                                  xen_blkif_max_ring_order);
1080                 return err;
1081         }
1082
1083         blkif->nr_ring_pages = 1 << ring_page_order;
1084
1085         if (blkif->nr_rings == 1)
1086                 return read_per_ring_refs(&blkif->rings[0], dev->otherend);
1087         else {
1088                 xspathsize = strlen(dev->otherend) + xenstore_path_ext_size;
1089                 xspath = kmalloc(xspathsize, GFP_KERNEL);
1090                 if (!xspath) {
1091                         xenbus_dev_fatal(dev, -ENOMEM, "reading ring references");
1092                         return -ENOMEM;
1093                 }
1094
1095                 for (i = 0; i < blkif->nr_rings; i++) {
1096                         memset(xspath, 0, xspathsize);
1097                         snprintf(xspath, xspathsize, "%s/queue-%u", dev->otherend, i);
1098                         err = read_per_ring_refs(&blkif->rings[i], xspath);
1099                         if (err) {
1100                                 kfree(xspath);
1101                                 return err;
1102                         }
1103                 }
1104                 kfree(xspath);
1105         }
1106         return 0;
1107 }
1108
1109 static const struct xenbus_device_id xen_blkbk_ids[] = {
1110         { "vbd" },
1111         { "" }
1112 };
1113
1114 static struct xenbus_driver xen_blkbk_driver = {
1115         .ids  = xen_blkbk_ids,
1116         .probe = xen_blkbk_probe,
1117         .remove = xen_blkbk_remove,
1118         .otherend_changed = frontend_changed
1119 };
1120
1121 int xen_blkif_xenbus_init(void)
1122 {
1123         return xenbus_register_backend(&xen_blkbk_driver);
1124 }