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