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
 175         /*
 176          * Because freeing back to the cache may be deferred, it is not
 177          * safe to unload the module (and hence destroy the cache) until
 178          * this has completed. To prevent premature unloading, take an
 179          * extra module reference here and release only when the object
 180          * has been freed back to the cache.
 181          */
 182         __module_get(THIS_MODULE);
 183         INIT_WORK(&blkif->free_work, xen_blkif_deferred_free);
 184
 185         return blkif;
 186 }
 187
 188 static int xen_blkif_map(struct xen_blkif_ring *ring, grant_ref_t *gref,
 189                          unsigned int nr_grefs, unsigned int evtchn)
 190 {
 191         int err;
 192         struct xen_blkif *blkif = ring->blkif;
 193         const struct blkif_common_sring *sring_common;
 194         RING_IDX rsp_prod, req_prod;
 195         unsigned int size;
 196
 197         /* Already connected through? */
 198         if (ring->irq)
 199                 return 0;
 200
 201         err = xenbus_map_ring_valloc(blkif->be->dev, gref, nr_grefs,
 202                                      &ring->blk_ring);
 203         if (err < 0)
 204                 return err;
 205
 206         sring_common = (struct blkif_common_sring *)ring->blk_ring;
 207         rsp_prod = READ_ONCE(sring_common->rsp_prod);
 208         req_prod = READ_ONCE(sring_common->req_prod);
 209
 210         switch (blkif->blk_protocol) {
 211         case BLKIF_PROTOCOL_NATIVE:
 212         {
 213                 struct blkif_sring *sring_native =
 214                         (struct blkif_sring *)ring->blk_ring;
 215
 216                 BACK_RING_ATTACH(&ring->blk_rings.native, sring_native,
 217                                  rsp_prod, XEN_PAGE_SIZE * nr_grefs);
 218                 size = __RING_SIZE(sring_native, XEN_PAGE_SIZE * nr_grefs);
 219                 break;
 220         }
 221         case BLKIF_PROTOCOL_X86_32:
 222         {
 223                 struct blkif_x86_32_sring *sring_x86_32 =
 224                         (struct blkif_x86_32_sring *)ring->blk_ring;
 225
 226                 BACK_RING_ATTACH(&ring->blk_rings.x86_32, sring_x86_32,
 227                                  rsp_prod, XEN_PAGE_SIZE * nr_grefs);
 228                 size = __RING_SIZE(sring_x86_32, XEN_PAGE_SIZE * nr_grefs);
 229                 break;
 230         }
 231         case BLKIF_PROTOCOL_X86_64:
 232         {
 233                 struct blkif_x86_64_sring *sring_x86_64 =
 234                         (struct blkif_x86_64_sring *)ring->blk_ring;
 235
 236                 BACK_RING_ATTACH(&ring->blk_rings.x86_64, sring_x86_64,
 237                                  rsp_prod, XEN_PAGE_SIZE * nr_grefs);
 238                 size = __RING_SIZE(sring_x86_64, XEN_PAGE_SIZE * nr_grefs);
 239                 break;
 240         }
 241         default:
 242                 BUG();
 243         }
 244
 245         err = -EIO;
 246         if (req_prod - rsp_prod > size)
 247                 goto fail;
 248
 249         err = bind_interdomain_evtchn_to_irqhandler(blkif->domid, evtchn,
 250                                                     xen_blkif_be_int, 0,
 251                                                     "blkif-backend", ring);
 252         if (err < 0)
 253                 goto fail;
 254         ring->irq = err;
 255
 256         return 0;
 257
 258 fail:
 259         xenbus_unmap_ring_vfree(blkif->be->dev, ring->blk_ring);
 260         ring->blk_rings.common.sring = NULL;
 261         return err;
 262 }
 263
 264 static int xen_blkif_disconnect(struct xen_blkif *blkif)
 265 {
 266         struct pending_req *req, *n;
 267         unsigned int j, r;
 268         bool busy = false;
 269
 270         for (r = 0; r < blkif->nr_rings; r++) {
 271                 struct xen_blkif_ring *ring = &blkif->rings[r];
 272                 unsigned int i = 0;
 273
 274                 if (!ring->active)
 275                         continue;
 276
 277                 if (ring->xenblkd) {
 278                         kthread_stop(ring->xenblkd);
 279                         wake_up(&ring->shutdown_wq);
 280                 }
 281
 282                 /* The above kthread_stop() guarantees that at this point we
 283                  * don't have any discard_io or other_io requests. So, checking
 284                  * for inflight IO is enough.
 285                  */
 286                 if (atomic_read(&ring->inflight) > 0) {
 287                         busy = true;
 288                         continue;
 289                 }
 290
 291                 if (ring->irq) {
 292                         unbind_from_irqhandler(ring->irq, ring);
 293                         ring->irq = 0;
 294                 }
 295
 296                 if (ring->blk_rings.common.sring) {
 297                         xenbus_unmap_ring_vfree(blkif->be->dev, ring->blk_ring);
 298                         ring->blk_rings.common.sring = NULL;
 299                 }
 300
 301                 /* Remove all persistent grants and the cache of ballooned pages. */
 302                 xen_blkbk_free_caches(ring);
 303
 304                 /* Check that there is no request in use */
 305                 list_for_each_entry_safe(req, n, &ring->pending_free, free_list) {
 306                         list_del(&req->free_list);
 307
 308                         for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++)
 309                                 kfree(req->segments[j]);
 310
 311                         for (j = 0; j < MAX_INDIRECT_PAGES; j++)
 312                                 kfree(req->indirect_pages[j]);
 313
 314                         kfree(req);
 315                         i++;
 316                 }
 317
 318                 BUG_ON(atomic_read(&ring->persistent_gnt_in_use) != 0);
 319                 BUG_ON(!list_empty(&ring->persistent_purge_list));
 320                 BUG_ON(!RB_EMPTY_ROOT(&ring->persistent_gnts));
 321                 BUG_ON(!list_empty(&ring->free_pages));
 322                 BUG_ON(ring->free_pages_num != 0);
 323                 BUG_ON(ring->persistent_gnt_c != 0);
 324                 WARN_ON(i != (XEN_BLKIF_REQS_PER_PAGE * blkif->nr_ring_pages));
 325                 ring->active = false;
 326         }
 327         if (busy)
 328                 return -EBUSY;
 329
 330         blkif->nr_ring_pages = 0;
 331         /*
 332          * blkif->rings was allocated in connect_ring, so we should free it in
 333          * here.
 334          */
 335         kfree(blkif->rings);
 336         blkif->rings = NULL;
 337         blkif->nr_rings = 0;
 338
 339         return 0;
 340 }
 341
 342 static void xen_blkif_free(struct xen_blkif *blkif)
 343 {
 344         WARN_ON(xen_blkif_disconnect(blkif));
 345         xen_vbd_free(&blkif->vbd);
 346         kfree(blkif->be->mode);
 347         kfree(blkif->be);
 348
 349         /* Make sure everything is drained before shutting down */
 350         kmem_cache_free(xen_blkif_cachep, blkif);
 351         module_put(THIS_MODULE);
 352 }
 353
 354 int __init xen_blkif_interface_init(void)
 355 {
 356         xen_blkif_cachep = kmem_cache_create("blkif_cache",
 357                                              sizeof(struct xen_blkif),
 358                                              0, 0, NULL);
 359         if (!xen_blkif_cachep)
 360                 return -ENOMEM;
 361
 362         return 0;
 363 }
 364
 365 void xen_blkif_interface_fini(void)
 366 {
 367         kmem_cache_destroy(xen_blkif_cachep);
 368         xen_blkif_cachep = NULL;
 369 }
 370
 371 /*
 372  *  sysfs interface for VBD I/O requests
 373  */
 374
 375 #define VBD_SHOW_ALLRING(name, format)                                  \
 376         static ssize_t show_##name(struct device *_dev,                 \
 377                                    struct device_attribute *attr,       \
 378                                    char *buf)                           \
 379         {                                                               \
 380                 struct xenbus_device *dev = to_xenbus_device(_dev);     \
 381                 struct backend_info *be = dev_get_drvdata(&dev->dev);   \
 382                 struct xen_blkif *blkif = be->blkif;                    \
 383                 unsigned int i;                                         \
 384                 unsigned long long result = 0;                          \
 385                                                                         \
 386                 if (!blkif->rings)                              \
 387                         goto out;                                       \
 388                                                                         \
 389                 for (i = 0; i < blkif->nr_rings; i++) {         \
 390                         struct xen_blkif_ring *ring = &blkif->rings[i]; \
 391                                                                         \
 392                         result += ring->st_##name;                      \
 393                 }                                                       \
 394                                                                         \
 395 out:                                                                    \
 396                 return sprintf(buf, format, result);                    \
 397         }                                                               \
 398         static DEVICE_ATTR(name, 0444, show_##name, NULL)
 399
 400 VBD_SHOW_ALLRING(oo_req,  "%llu\n");
 401 VBD_SHOW_ALLRING(rd_req,  "%llu\n");
 402 VBD_SHOW_ALLRING(wr_req,  "%llu\n");
 403 VBD_SHOW_ALLRING(f_req,  "%llu\n");
 404 VBD_SHOW_ALLRING(ds_req,  "%llu\n");
 405 VBD_SHOW_ALLRING(rd_sect, "%llu\n");
 406 VBD_SHOW_ALLRING(wr_sect, "%llu\n");
 407
 408 static struct attribute *xen_vbdstat_attrs[] = {
 409         &dev_attr_oo_req.attr,
 410         &dev_attr_rd_req.attr,
 411         &dev_attr_wr_req.attr,
 412         &dev_attr_f_req.attr,
 413         &dev_attr_ds_req.attr,
 414         &dev_attr_rd_sect.attr,
 415         &dev_attr_wr_sect.attr,
 416         NULL
 417 };
 418
 419 static const struct attribute_group xen_vbdstat_group = {
 420         .name = "statistics",
 421         .attrs = xen_vbdstat_attrs,
 422 };
 423
 424 #define VBD_SHOW(name, format, args...)                                 \
 425         static ssize_t show_##name(struct device *_dev,                 \
 426                                    struct device_attribute *attr,       \
 427                                    char *buf)                           \
 428         {                                                               \
 429                 struct xenbus_device *dev = to_xenbus_device(_dev);     \
 430                 struct backend_info *be = dev_get_drvdata(&dev->dev);   \
 431                                                                         \
 432                 return sprintf(buf, format, ##args);                    \
 433         }                                                               \
 434         static DEVICE_ATTR(name, 0444, show_##name, NULL)
 435
 436 VBD_SHOW(physical_device, "%x:%x\n", be->major, be->minor);
 437 VBD_SHOW(mode, "%s\n", be->mode);
 438
 439 static int xenvbd_sysfs_addif(struct xenbus_device *dev)
 440 {
 441         int error;
 442
 443         error = device_create_file(&dev->dev, &dev_attr_physical_device);
 444         if (error)
 445                 goto fail1;
 446
 447         error = device_create_file(&dev->dev, &dev_attr_mode);
 448         if (error)
 449                 goto fail2;
 450
 451         error = sysfs_create_group(&dev->dev.kobj, &xen_vbdstat_group);
 452         if (error)
 453                 goto fail3;
 454
 455         return 0;
 456
 457 fail3:  sysfs_remove_group(&dev->dev.kobj, &xen_vbdstat_group);
 458 fail2:  device_remove_file(&dev->dev, &dev_attr_mode);
 459 fail1:  device_remove_file(&dev->dev, &dev_attr_physical_device);
 460         return error;
 461 }
 462
 463 static void xenvbd_sysfs_delif(struct xenbus_device *dev)
 464 {
 465         sysfs_remove_group(&dev->dev.kobj, &xen_vbdstat_group);
 466         device_remove_file(&dev->dev, &dev_attr_mode);
 467         device_remove_file(&dev->dev, &dev_attr_physical_device);
 468 }
 469
 470 static void xen_vbd_free(struct xen_vbd *vbd)
 471 {
 472         if (vbd->bdev)
 473                 blkdev_put(vbd->bdev, vbd->readonly ? FMODE_READ : FMODE_WRITE);
 474         vbd->bdev = NULL;
 475 }
 476
 477 static int xen_vbd_create(struct xen_blkif *blkif, blkif_vdev_t handle,
 478                           unsigned major, unsigned minor, int readonly,
 479                           int cdrom)
 480 {
 481         struct xen_vbd *vbd;
 482         struct block_device *bdev;
 483         struct request_queue *q;
 484
 485         vbd = &blkif->vbd;
 486         vbd->handle   = handle;
 487         vbd->readonly = readonly;
 488         vbd->type     = 0;
 489
 490         vbd->pdevice  = MKDEV(major, minor);
 491
 492         bdev = blkdev_get_by_dev(vbd->pdevice, vbd->readonly ?
 493                                  FMODE_READ : FMODE_WRITE, NULL);
 494
 495         if (IS_ERR(bdev)) {
 496                 pr_warn("xen_vbd_create: device %08x could not be opened\n",
 497                         vbd->pdevice);
 498                 return -ENOENT;
 499         }
 500
 501         vbd->bdev = bdev;
 502         if (vbd->bdev->bd_disk == NULL) {
 503                 pr_warn("xen_vbd_create: device %08x doesn't exist\n",
 504                         vbd->pdevice);
 505                 xen_vbd_free(vbd);
 506                 return -ENOENT;
 507         }
 508         vbd->size = vbd_sz(vbd);
 509
 510         if (vbd->bdev->bd_disk->flags & GENHD_FL_CD || cdrom)
 511                 vbd->type |= VDISK_CDROM;
 512         if (vbd->bdev->bd_disk->flags & GENHD_FL_REMOVABLE)
 513                 vbd->type |= VDISK_REMOVABLE;
 514
 515         q = bdev_get_queue(bdev);
 516         if (q && test_bit(QUEUE_FLAG_WC, &q->queue_flags))
 517                 vbd->flush_support = true;
 518
 519         if (q && blk_queue_secure_erase(q))
 520                 vbd->discard_secure = true;
 521
 522         pr_debug("Successful creation of handle=%04x (dom=%u)\n",
 523                 handle, blkif->domid);
 524         return 0;
 525 }
 526
 527 static int xen_blkbk_remove(struct xenbus_device *dev)
 528 {
 529         struct backend_info *be = dev_get_drvdata(&dev->dev);
 530
 531         pr_debug("%s %p %d\n", __func__, dev, dev->otherend_id);
 532
 533         if (be->major || be->minor)
 534                 xenvbd_sysfs_delif(dev);
 535
 536         if (be->backend_watch.node) {
 537                 unregister_xenbus_watch(&be->backend_watch);
 538                 kfree(be->backend_watch.node);
 539                 be->backend_watch.node = NULL;
 540         }
 541
 542         dev_set_drvdata(&dev->dev, NULL);
 543
 544         if (be->blkif) {
 545                 xen_blkif_disconnect(be->blkif);
 546
 547                 /* Put the reference we set in xen_blkif_alloc(). */
 548                 xen_blkif_put(be->blkif);
 549         }
 550
 551         return 0;
 552 }
 553
 554 int xen_blkbk_flush_diskcache(struct xenbus_transaction xbt,
 555                               struct backend_info *be, int state)
 556 {
 557         struct xenbus_device *dev = be->dev;
 558         int err;
 559
 560         err = xenbus_printf(xbt, dev->nodename, "feature-flush-cache",
 561                             "%d", state);
 562         if (err)
 563                 dev_warn(&dev->dev, "writing feature-flush-cache (%d)", err);
 564
 565         return err;
 566 }
 567
 568 static void xen_blkbk_discard(struct xenbus_transaction xbt, struct backend_info *be)
 569 {
 570         struct xenbus_device *dev = be->dev;
 571         struct xen_blkif *blkif = be->blkif;
 572         int err;
 573         int state = 0;
 574         struct block_device *bdev = be->blkif->vbd.bdev;
 575         struct request_queue *q = bdev_get_queue(bdev);
 576
 577         if (!xenbus_read_unsigned(dev->nodename, "discard-enable", 1))
 578                 return;
 579
 580         if (blk_queue_discard(q)) {
 581                 err = xenbus_printf(xbt, dev->nodename,
 582                         "discard-granularity", "%u",
 583                         q->limits.discard_granularity);
 584                 if (err) {
 585                         dev_warn(&dev->dev, "writing discard-granularity (%d)", err);
 586                         return;
 587                 }
 588                 err = xenbus_printf(xbt, dev->nodename,
 589                         "discard-alignment", "%u",
 590                         q->limits.discard_alignment);
 591                 if (err) {
 592                         dev_warn(&dev->dev, "writing discard-alignment (%d)", err);
 593                         return;
 594                 }
 595                 state = 1;
 596                 /* Optional. */
 597                 err = xenbus_printf(xbt, dev->nodename,
 598                                     "discard-secure", "%d",
 599                                     blkif->vbd.discard_secure);
 600                 if (err) {
 601                         dev_warn(&dev->dev, "writing discard-secure (%d)", err);
 602                         return;
 603                 }
 604         }
 605         err = xenbus_printf(xbt, dev->nodename, "feature-discard",
 606                             "%d", state);
 607         if (err)
 608                 dev_warn(&dev->dev, "writing feature-discard (%d)", err);
 609 }
 610
 611 int xen_blkbk_barrier(struct xenbus_transaction xbt,
 612                       struct backend_info *be, int state)
 613 {
 614         struct xenbus_device *dev = be->dev;
 615         int err;
 616
 617         err = xenbus_printf(xbt, dev->nodename, "feature-barrier",
 618                             "%d", state);
 619         if (err)
 620                 dev_warn(&dev->dev, "writing feature-barrier (%d)", err);
 621
 622         return err;
 623 }
 624
 625 /*
 626  * Entry point to this code when a new device is created.  Allocate the basic
 627  * structures, and watch the store waiting for the hotplug scripts to tell us
 628  * the device's physical major and minor numbers.  Switch to InitWait.
 629  */
 630 static int xen_blkbk_probe(struct xenbus_device *dev,
 631                            const struct xenbus_device_id *id)
 632 {
 633         int err;
 634         struct backend_info *be = kzalloc(sizeof(struct backend_info),
 635                                           GFP_KERNEL);
 636
 637         /* match the pr_debug in xen_blkbk_remove */
 638         pr_debug("%s %p %d\n", __func__, dev, dev->otherend_id);
 639
 640         if (!be) {
 641                 xenbus_dev_fatal(dev, -ENOMEM,
 642                                  "allocating backend structure");
 643                 return -ENOMEM;
 644         }
 645         be->dev = dev;
 646         dev_set_drvdata(&dev->dev, be);
 647
 648         be->blkif = xen_blkif_alloc(dev->otherend_id);
 649         if (IS_ERR(be->blkif)) {
 650                 err = PTR_ERR(be->blkif);
 651                 be->blkif = NULL;
 652                 xenbus_dev_fatal(dev, err, "creating block interface");
 653                 goto fail;
 654         }
 655
 656         err = xenbus_printf(XBT_NIL, dev->nodename,
 657                             "feature-max-indirect-segments", "%u",
 658                             MAX_INDIRECT_SEGMENTS);
 659         if (err)
 660                 dev_warn(&dev->dev,
 661                          "writing %s/feature-max-indirect-segments (%d)",
 662                          dev->nodename, err);
 663
 664         /* Multi-queue: advertise how many queues are supported by us.*/
 665         err = xenbus_printf(XBT_NIL, dev->nodename,
 666                             "multi-queue-max-queues", "%u", xenblk_max_queues);
 667         if (err)
 668                 pr_warn("Error writing multi-queue-max-queues\n");
 669
 670         /* setup back pointer */
 671         be->blkif->be = be;
 672
 673         err = xenbus_watch_pathfmt(dev, &be->backend_watch, backend_changed,
 674                                    "%s/%s", dev->nodename, "physical-device");
 675         if (err)
 676                 goto fail;
 677
 678         err = xenbus_printf(XBT_NIL, dev->nodename, "max-ring-page-order", "%u",
 679                             xen_blkif_max_ring_order);
 680         if (err)
 681                 pr_warn("%s write out 'max-ring-page-order' failed\n", __func__);
 682
 683         err = xenbus_switch_state(dev, XenbusStateInitWait);
 684         if (err)
 685                 goto fail;
 686
 687         return 0;
 688
 689 fail:
 690         pr_warn("%s failed\n", __func__);
 691         xen_blkbk_remove(dev);
 692         return err;
 693 }
 694
 695 /*
 696  * Callback received when the hotplug scripts have placed the physical-device
 697  * node.  Read it and the mode node, and create a vbd.  If the frontend is
 698  * ready, connect.
 699  */
 700 static void backend_changed(struct xenbus_watch *watch,
 701                             const char *path, const char *token)
 702 {
 703         int err;
 704         unsigned major;
 705         unsigned minor;
 706         struct backend_info *be
 707                 = container_of(watch, struct backend_info, backend_watch);
 708         struct xenbus_device *dev = be->dev;
 709         int cdrom = 0;
 710         unsigned long handle;
 711         char *device_type;
 712
 713         pr_debug("%s %p %d\n", __func__, dev, dev->otherend_id);
 714
 715         err = xenbus_scanf(XBT_NIL, dev->nodename, "physical-device", "%x:%x",
 716                            &major, &minor);
 717         if (XENBUS_EXIST_ERR(err)) {
 718                 /*
 719                  * Since this watch will fire once immediately after it is
 720                  * registered, we expect this.  Ignore it, and wait for the
 721                  * hotplug scripts.
 722                  */
 723                 return;
 724         }
 725         if (err != 2) {
 726                 xenbus_dev_fatal(dev, err, "reading physical-device");
 727                 return;
 728         }
 729
 730         if (be->major | be->minor) {
 731                 if (be->major != major || be->minor != minor)
 732                         pr_warn("changing physical device (from %x:%x to %x:%x) not supported.\n",
 733                                 be->major, be->minor, major, minor);
 734                 return;
 735         }
 736
 737         be->mode = xenbus_read(XBT_NIL, dev->nodename, "mode", NULL);
 738         if (IS_ERR(be->mode)) {
 739                 err = PTR_ERR(be->mode);
 740                 be->mode = NULL;
 741                 xenbus_dev_fatal(dev, err, "reading mode");
 742                 return;
 743         }
 744
 745         device_type = xenbus_read(XBT_NIL, dev->otherend, "device-type", NULL);
 746         if (!IS_ERR(device_type)) {
 747                 cdrom = strcmp(device_type, "cdrom") == 0;
 748                 kfree(device_type);
 749         }
 750
 751         /* Front end dir is a number, which is used as the handle. */
 752         err = kstrtoul(strrchr(dev->otherend, '/') + 1, 0, &handle);
 753         if (err) {
 754                 kfree(be->mode);
 755                 be->mode = NULL;
 756                 return;
 757         }
 758
 759         be->major = major;
 760         be->minor = minor;
 761
 762         err = xen_vbd_create(be->blkif, handle, major, minor,
 763                              !strchr(be->mode, 'w'), cdrom);
 764
 765         if (err)
 766                 xenbus_dev_fatal(dev, err, "creating vbd structure");
 767         else {
 768                 err = xenvbd_sysfs_addif(dev);
 769                 if (err) {
 770                         xen_vbd_free(&be->blkif->vbd);
 771                         xenbus_dev_fatal(dev, err, "creating sysfs entries");
 772                 }
 773         }
 774
 775         if (err) {
 776                 kfree(be->mode);
 777                 be->mode = NULL;
 778                 be->major = 0;
 779                 be->minor = 0;
 780         } else {
 781                 /* We're potentially connected now */
 782                 xen_update_blkif_status(be->blkif);
 783         }
 784 }
 785
 786 /*
 787  * Callback received when the frontend's state changes.
 788  */
 789 static void frontend_changed(struct xenbus_device *dev,
 790                              enum xenbus_state frontend_state)
 791 {
 792         struct backend_info *be = dev_get_drvdata(&dev->dev);
 793         int err;
 794
 795         pr_debug("%s %p %s\n", __func__, dev, xenbus_strstate(frontend_state));
 796
 797         switch (frontend_state) {
 798         case XenbusStateInitialising:
 799                 if (dev->state == XenbusStateClosed) {
 800                         pr_info("%s: prepare for reconnect\n", dev->nodename);
 801                         xenbus_switch_state(dev, XenbusStateInitWait);
 802                 }
 803                 break;
 804
 805         case XenbusStateInitialised:
 806         case XenbusStateConnected:
 807                 /*
 808                  * Ensure we connect even when two watches fire in
 809                  * close succession and we miss the intermediate value
 810                  * of frontend_state.
 811                  */
 812                 if (dev->state == XenbusStateConnected)
 813                         break;
 814
 815                 /*
 816                  * Enforce precondition before potential leak point.
 817                  * xen_blkif_disconnect() is idempotent.
 818                  */
 819                 err = xen_blkif_disconnect(be->blkif);
 820                 if (err) {
 821                         xenbus_dev_fatal(dev, err, "pending I/O");
 822                         break;
 823                 }
 824
 825                 err = connect_ring(be);
 826                 if (err) {
 827                         /*
 828                          * Clean up so that memory resources can be used by
 829                          * other devices. connect_ring reported already error.
 830                          */
 831                         xen_blkif_disconnect(be->blkif);
 832                         break;
 833                 }
 834                 xen_update_blkif_status(be->blkif);
 835                 break;
 836
 837         case XenbusStateClosing:
 838                 xenbus_switch_state(dev, XenbusStateClosing);
 839                 break;
 840
 841         case XenbusStateClosed:
 842                 xen_blkif_disconnect(be->blkif);
 843                 xenbus_switch_state(dev, XenbusStateClosed);
 844                 if (xenbus_dev_is_online(dev))
 845                         break;
 846                 fallthrough;
 847                 /* if not online */
 848         case XenbusStateUnknown:
 849                 /* implies xen_blkif_disconnect() via xen_blkbk_remove() */
 850                 device_unregister(&dev->dev);
 851                 break;
 852
 853         default:
 854                 xenbus_dev_fatal(dev, -EINVAL, "saw state %d at frontend",
 855                                  frontend_state);
 856                 break;
 857         }
 858 }
 859
 860 /* Once a memory pressure is detected, squeeze free page pools for a while. */
 861 static unsigned int buffer_squeeze_duration_ms = 10;
 862 module_param_named(buffer_squeeze_duration_ms,
 863                 buffer_squeeze_duration_ms, int, 0644);
 864 MODULE_PARM_DESC(buffer_squeeze_duration_ms,
 865 "Duration in ms to squeeze pages buffer when a memory pressure is detected");
 866
 867 /*
 868  * Callback received when the memory pressure is detected.
 869  */
 870 static void reclaim_memory(struct xenbus_device *dev)
 871 {
 872         struct backend_info *be = dev_get_drvdata(&dev->dev);
 873
 874         if (!be)
 875                 return;
 876         be->blkif->buffer_squeeze_end = jiffies +
 877                 msecs_to_jiffies(buffer_squeeze_duration_ms);
 878 }
 879
 880 /* ** Connection ** */
 881
 882 /*
 883  * Write the physical details regarding the block device to the store, and
 884  * switch to Connected state.
 885  */
 886 static void connect(struct backend_info *be)
 887 {
 888         struct xenbus_transaction xbt;
 889         int err;
 890         struct xenbus_device *dev = be->dev;
 891
 892         pr_debug("%s %s\n", __func__, dev->otherend);
 893
 894         /* Supply the information about the device the frontend needs */
 895 again:
 896         err = xenbus_transaction_start(&xbt);
 897         if (err) {
 898                 xenbus_dev_fatal(dev, err, "starting transaction");
 899                 return;
 900         }
 901
 902         /* If we can't advertise it is OK. */
 903         xen_blkbk_flush_diskcache(xbt, be, be->blkif->vbd.flush_support);
 904
 905         xen_blkbk_discard(xbt, be);
 906
 907         xen_blkbk_barrier(xbt, be, be->blkif->vbd.flush_support);
 908
 909         err = xenbus_printf(xbt, dev->nodename, "feature-persistent", "%u", 1);
 910         if (err) {
 911                 xenbus_dev_fatal(dev, err, "writing %s/feature-persistent",
 912                                  dev->nodename);
 913                 goto abort;
 914         }
 915
 916         err = xenbus_printf(xbt, dev->nodename, "sectors", "%llu",
 917                             (unsigned long long)vbd_sz(&be->blkif->vbd));
 918         if (err) {
 919                 xenbus_dev_fatal(dev, err, "writing %s/sectors",
 920                                  dev->nodename);
 921                 goto abort;
 922         }
 923
 924         /* FIXME: use a typename instead */
 925         err = xenbus_printf(xbt, dev->nodename, "info", "%u",
 926                             be->blkif->vbd.type |
 927                             (be->blkif->vbd.readonly ? VDISK_READONLY : 0));
 928         if (err) {
 929                 xenbus_dev_fatal(dev, err, "writing %s/info",
 930                                  dev->nodename);
 931                 goto abort;
 932         }
 933         err = xenbus_printf(xbt, dev->nodename, "sector-size", "%lu",
 934                             (unsigned long)
 935                             bdev_logical_block_size(be->blkif->vbd.bdev));
 936         if (err) {
 937                 xenbus_dev_fatal(dev, err, "writing %s/sector-size",
 938                                  dev->nodename);
 939                 goto abort;
 940         }
 941         err = xenbus_printf(xbt, dev->nodename, "physical-sector-size", "%u",
 942                             bdev_physical_block_size(be->blkif->vbd.bdev));
 943         if (err)
 944                 xenbus_dev_error(dev, err, "writing %s/physical-sector-size",
 945                                  dev->nodename);
 946
 947         err = xenbus_transaction_end(xbt, 0);
 948         if (err == -EAGAIN)
 949                 goto again;
 950         if (err)
 951                 xenbus_dev_fatal(dev, err, "ending transaction");
 952
 953         err = xenbus_switch_state(dev, XenbusStateConnected);
 954         if (err)
 955                 xenbus_dev_fatal(dev, err, "%s: switching to Connected state",
 956                                  dev->nodename);
 957
 958         return;
 959  abort:
 960         xenbus_transaction_end(xbt, 1);
 961 }
 962
 963 /*
 964  * Each ring may have multi pages, depends on "ring-page-order".
 965  */
 966 static int read_per_ring_refs(struct xen_blkif_ring *ring, const char *dir)
 967 {
 968         unsigned int ring_ref[XENBUS_MAX_RING_GRANTS];
 969         struct pending_req *req, *n;
 970         int err, i, j;
 971         struct xen_blkif *blkif = ring->blkif;
 972         struct xenbus_device *dev = blkif->be->dev;
 973         unsigned int nr_grefs, evtchn;
 974
 975         err = xenbus_scanf(XBT_NIL, dir, "event-channel", "%u",
 976                           &evtchn);
 977         if (err != 1) {
 978                 err = -EINVAL;
 979                 xenbus_dev_fatal(dev, err, "reading %s/event-channel", dir);
 980                 return err;
 981         }
 982
 983         nr_grefs = blkif->nr_ring_pages;
 984
 985         if (unlikely(!nr_grefs)) {
 986                 WARN_ON(true);
 987                 return -EINVAL;
 988         }
 989
 990         for (i = 0; i < nr_grefs; i++) {
 991                 char ring_ref_name[RINGREF_NAME_LEN];
 992
 993                 snprintf(ring_ref_name, RINGREF_NAME_LEN, "ring-ref%u", i);
 994                 err = xenbus_scanf(XBT_NIL, dir, ring_ref_name,
 995                                    "%u", &ring_ref[i]);
 996
 997                 if (err != 1) {
 998                         if (nr_grefs == 1)
 999                                 break;
1000
1001                         err = -EINVAL;
1002                         xenbus_dev_fatal(dev, err, "reading %s/%s",
1003                                          dir, ring_ref_name);
1004                         return err;
1005                 }
1006         }
1007
1008         if (err != 1) {
1009                 WARN_ON(nr_grefs != 1);
1010
1011                 err = xenbus_scanf(XBT_NIL, dir, "ring-ref", "%u",
1012                                    &ring_ref[0]);
1013                 if (err != 1) {
1014                         err = -EINVAL;
1015                         xenbus_dev_fatal(dev, err, "reading %s/ring-ref", dir);
1016                         return err;
1017                 }
1018         }
1019
1020         err = -ENOMEM;
1021         for (i = 0; i < nr_grefs * XEN_BLKIF_REQS_PER_PAGE; i++) {
1022                 req = kzalloc(sizeof(*req), GFP_KERNEL);
1023                 if (!req)
1024                         goto fail;
1025                 list_add_tail(&req->free_list, &ring->pending_free);
1026                 for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++) {
1027                         req->segments[j] = kzalloc(sizeof(*req->segments[0]), GFP_KERNEL);
1028                         if (!req->segments[j])
1029                                 goto fail;
1030                 }
1031                 for (j = 0; j < MAX_INDIRECT_PAGES; j++) {
1032                         req->indirect_pages[j] = kzalloc(sizeof(*req->indirect_pages[0]),
1033                                                          GFP_KERNEL);
1034                         if (!req->indirect_pages[j])
1035                                 goto fail;
1036                 }
1037         }
1038
1039         /* Map the shared frame, irq etc. */
1040         err = xen_blkif_map(ring, ring_ref, nr_grefs, evtchn);
1041         if (err) {
1042                 xenbus_dev_fatal(dev, err, "mapping ring-ref port %u", evtchn);
1043                 goto fail;
1044         }
1045
1046         return 0;
1047
1048 fail:
1049         list_for_each_entry_safe(req, n, &ring->pending_free, free_list) {
1050                 list_del(&req->free_list);
1051                 for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++) {
1052                         if (!req->segments[j])
1053                                 break;
1054                         kfree(req->segments[j]);
1055                 }
1056                 for (j = 0; j < MAX_INDIRECT_PAGES; j++) {
1057                         if (!req->indirect_pages[j])
1058                                 break;
1059                         kfree(req->indirect_pages[j]);
1060                 }
1061                 kfree(req);
1062         }
1063         return err;
1064 }
1065
1066 static int connect_ring(struct backend_info *be)
1067 {
1068         struct xenbus_device *dev = be->dev;
1069         struct xen_blkif *blkif = be->blkif;
1070         unsigned int pers_grants;
1071         char protocol[64] = "";
1072         int err, i;
1073         char *xspath;
1074         size_t xspathsize;
1075         const size_t xenstore_path_ext_size = 11; /* sufficient for "/queue-NNN" */
1076         unsigned int requested_num_queues = 0;
1077         unsigned int ring_page_order;
1078
1079         pr_debug("%s %s\n", __func__, dev->otherend);
1080
1081         blkif->blk_protocol = BLKIF_PROTOCOL_DEFAULT;
1082         err = xenbus_scanf(XBT_NIL, dev->otherend, "protocol",
1083                            "%63s", protocol);
1084         if (err <= 0)
1085                 strcpy(protocol, "unspecified, assuming default");
1086         else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_NATIVE))
1087                 blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
1088         else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_32))
1089                 blkif->blk_protocol = BLKIF_PROTOCOL_X86_32;
1090         else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_64))
1091                 blkif->blk_protocol = BLKIF_PROTOCOL_X86_64;
1092         else {
1093                 xenbus_dev_fatal(dev, err, "unknown fe protocol %s", protocol);
1094                 return -ENOSYS;
1095         }
1096         pers_grants = xenbus_read_unsigned(dev->otherend, "feature-persistent",
1097                                            0);
1098         blkif->vbd.feature_gnt_persistent = pers_grants;
1099         blkif->vbd.overflow_max_grants = 0;
1100
1101         /*
1102          * Read the number of hardware queues from frontend.
1103          */
1104         requested_num_queues = xenbus_read_unsigned(dev->otherend,
1105                                                     "multi-queue-num-queues",
1106                                                     1);
1107         if (requested_num_queues > xenblk_max_queues
1108             || requested_num_queues == 0) {
1109                 /* Buggy or malicious guest. */
1110                 xenbus_dev_fatal(dev, err,
1111                                 "guest requested %u queues, exceeding the maximum of %u.",
1112                                 requested_num_queues, xenblk_max_queues);
1113                 return -ENOSYS;
1114         }
1115         blkif->nr_rings = requested_num_queues;
1116         if (xen_blkif_alloc_rings(blkif))
1117                 return -ENOMEM;
1118
1119         pr_info("%s: using %d queues, protocol %d (%s) %s\n", dev->nodename,
1120                  blkif->nr_rings, blkif->blk_protocol, protocol,
1121                  pers_grants ? "persistent grants" : "");
1122
1123         ring_page_order = xenbus_read_unsigned(dev->otherend,
1124                                                "ring-page-order", 0);
1125
1126         if (ring_page_order > xen_blkif_max_ring_order) {
1127                 err = -EINVAL;
1128                 xenbus_dev_fatal(dev, err,
1129                                  "requested ring page order %d exceed max:%d",
1130                                  ring_page_order,
1131                                  xen_blkif_max_ring_order);
1132                 return err;
1133         }
1134
1135         blkif->nr_ring_pages = 1 << ring_page_order;
1136
1137         if (blkif->nr_rings == 1)
1138                 return read_per_ring_refs(&blkif->rings[0], dev->otherend);
1139         else {
1140                 xspathsize = strlen(dev->otherend) + xenstore_path_ext_size;
1141                 xspath = kmalloc(xspathsize, GFP_KERNEL);
1142                 if (!xspath) {
1143                         xenbus_dev_fatal(dev, -ENOMEM, "reading ring references");
1144                         return -ENOMEM;
1145                 }
1146
1147                 for (i = 0; i < blkif->nr_rings; i++) {
1148                         memset(xspath, 0, xspathsize);
1149                         snprintf(xspath, xspathsize, "%s/queue-%u", dev->otherend, i);
1150                         err = read_per_ring_refs(&blkif->rings[i], xspath);
1151                         if (err) {
1152                                 kfree(xspath);
1153                                 return err;
1154                         }
1155                 }
1156                 kfree(xspath);
1157         }
1158         return 0;
1159 }
1160
1161 static const struct xenbus_device_id xen_blkbk_ids[] = {
1162         { "vbd" },
1163         { "" }
1164 };
1165
1166 static struct xenbus_driver xen_blkbk_driver = {
1167         .ids  = xen_blkbk_ids,
1168         .probe = xen_blkbk_probe,
1169         .remove = xen_blkbk_remove,
1170         .otherend_changed = frontend_changed,
1171         .allow_rebind = true,
1172         .reclaim_memory = reclaim_memory,
1173 };
1174
1175 int xen_blkif_xenbus_init(void)
1176 {
1177         return xenbus_register_backend(&xen_blkbk_driver);
1178 }
1179
1180 void xen_blkif_xenbus_fini(void)
1181 {
1182         xenbus_unregister_driver(&xen_blkbk_driver);
1183 }