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                 gnttab_page_cache_init(&ring->free_pages);
 148
 149                 spin_lock_init(&ring->pending_free_lock);
 150                 init_waitqueue_head(&ring->pending_free_wq);
 151                 init_waitqueue_head(&ring->shutdown_wq);
 152                 ring->blkif = blkif;
 153                 ring->st_print = jiffies;
 154                 ring->active = true;
 155         }
 156
 157         return 0;
 158 }
 159
 160 static struct xen_blkif *xen_blkif_alloc(domid_t domid)
 161 {
 162         struct xen_blkif *blkif;
 163
 164         BUILD_BUG_ON(MAX_INDIRECT_PAGES > BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST);
 165
 166         blkif = kmem_cache_zalloc(xen_blkif_cachep, GFP_KERNEL);
 167         if (!blkif)
 168                 return ERR_PTR(-ENOMEM);
 169
 170         blkif->domid = domid;
 171         atomic_set(&blkif->refcnt, 1);
 172         init_completion(&blkif->drain_complete);
 173
 174         /*
 175          * Because freeing back to the cache may be deferred, it is not
 176          * safe to unload the module (and hence destroy the cache) until
 177          * this has completed. To prevent premature unloading, take an
 178          * extra module reference here and release only when the object
 179          * has been freed back to the cache.
 180          */
 181         __module_get(THIS_MODULE);
 182         INIT_WORK(&blkif->free_work, xen_blkif_deferred_free);
 183
 184         return blkif;
 185 }
 186
 187 static int xen_blkif_map(struct xen_blkif_ring *ring, grant_ref_t *gref,
 188                          unsigned int nr_grefs, unsigned int evtchn)
 189 {
 190         int err;
 191         struct xen_blkif *blkif = ring->blkif;
 192         const struct blkif_common_sring *sring_common;
 193         RING_IDX rsp_prod, req_prod;
 194         unsigned int size;
 195
 196         /* Already connected through? */
 197         if (ring->irq)
 198                 return 0;
 199
 200         err = xenbus_map_ring_valloc(blkif->be->dev, gref, nr_grefs,
 201                                      &ring->blk_ring);
 202         if (err < 0)
 203                 return err;
 204
 205         sring_common = (struct blkif_common_sring *)ring->blk_ring;
 206         rsp_prod = READ_ONCE(sring_common->rsp_prod);
 207         req_prod = READ_ONCE(sring_common->req_prod);
 208
 209         switch (blkif->blk_protocol) {
 210         case BLKIF_PROTOCOL_NATIVE:
 211         {
 212                 struct blkif_sring *sring_native =
 213                         (struct blkif_sring *)ring->blk_ring;
 214
 215                 BACK_RING_ATTACH(&ring->blk_rings.native, sring_native,
 216                                  rsp_prod, XEN_PAGE_SIZE * nr_grefs);
 217                 size = __RING_SIZE(sring_native, XEN_PAGE_SIZE * nr_grefs);
 218                 break;
 219         }
 220         case BLKIF_PROTOCOL_X86_32:
 221         {
 222                 struct blkif_x86_32_sring *sring_x86_32 =
 223                         (struct blkif_x86_32_sring *)ring->blk_ring;
 224
 225                 BACK_RING_ATTACH(&ring->blk_rings.x86_32, sring_x86_32,
 226                                  rsp_prod, XEN_PAGE_SIZE * nr_grefs);
 227                 size = __RING_SIZE(sring_x86_32, XEN_PAGE_SIZE * nr_grefs);
 228                 break;
 229         }
 230         case BLKIF_PROTOCOL_X86_64:
 231         {
 232                 struct blkif_x86_64_sring *sring_x86_64 =
 233                         (struct blkif_x86_64_sring *)ring->blk_ring;
 234
 235                 BACK_RING_ATTACH(&ring->blk_rings.x86_64, sring_x86_64,
 236                                  rsp_prod, XEN_PAGE_SIZE * nr_grefs);
 237                 size = __RING_SIZE(sring_x86_64, XEN_PAGE_SIZE * nr_grefs);
 238                 break;
 239         }
 240         default:
 241                 BUG();
 242         }
 243
 244         err = -EIO;
 245         if (req_prod - rsp_prod > size)
 246                 goto fail;
 247
 248         err = bind_interdomain_evtchn_to_irqhandler_lateeoi(blkif->be->dev,
 249                         evtchn, xen_blkif_be_int, 0, "blkif-backend", ring);
 250         if (err < 0)
 251                 goto fail;
 252         ring->irq = err;
 253
 254         return 0;
 255
 256 fail:
 257         xenbus_unmap_ring_vfree(blkif->be->dev, ring->blk_ring);
 258         ring->blk_rings.common.sring = NULL;
 259         return err;
 260 }
 261
 262 static int xen_blkif_disconnect(struct xen_blkif *blkif)
 263 {
 264         struct pending_req *req, *n;
 265         unsigned int j, r;
 266         bool busy = false;
 267
 268         for (r = 0; r < blkif->nr_rings; r++) {
 269                 struct xen_blkif_ring *ring = &blkif->rings[r];
 270                 unsigned int i = 0;
 271
 272                 if (!ring->active)
 273                         continue;
 274
 275                 if (ring->xenblkd) {
 276                         kthread_stop(ring->xenblkd);
 277                         ring->xenblkd = NULL;
 278                         wake_up(&ring->shutdown_wq);
 279                 }
 280
 281                 /* The above kthread_stop() guarantees that at this point we
 282                  * don't have any discard_io or other_io requests. So, checking
 283                  * for inflight IO is enough.
 284                  */
 285                 if (atomic_read(&ring->inflight) > 0) {
 286                         busy = true;
 287                         continue;
 288                 }
 289
 290                 if (ring->irq) {
 291                         unbind_from_irqhandler(ring->irq, ring);
 292                         ring->irq = 0;
 293                 }
 294
 295                 if (ring->blk_rings.common.sring) {
 296                         xenbus_unmap_ring_vfree(blkif->be->dev, ring->blk_ring);
 297                         ring->blk_rings.common.sring = NULL;
 298                 }
 299
 300                 /* Remove all persistent grants and the cache of ballooned pages. */
 301                 xen_blkbk_free_caches(ring);
 302
 303                 /* Check that there is no request in use */
 304                 list_for_each_entry_safe(req, n, &ring->pending_free, free_list) {
 305                         list_del(&req->free_list);
 306
 307                         for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++)
 308                                 kfree(req->segments[j]);
 309
 310                         for (j = 0; j < MAX_INDIRECT_PAGES; j++)
 311                                 kfree(req->indirect_pages[j]);
 312
 313                         kfree(req);
 314                         i++;
 315                 }
 316
 317                 BUG_ON(atomic_read(&ring->persistent_gnt_in_use) != 0);
 318                 BUG_ON(!list_empty(&ring->persistent_purge_list));
 319                 BUG_ON(!RB_EMPTY_ROOT(&ring->persistent_gnts));
 320                 BUG_ON(ring->free_pages.num_pages != 0);
 321                 BUG_ON(ring->persistent_gnt_c != 0);
 322                 WARN_ON(i != (XEN_BLKIF_REQS_PER_PAGE * blkif->nr_ring_pages));
 323                 ring->active = false;
 324         }
 325         if (busy)
 326                 return -EBUSY;
 327
 328         blkif->nr_ring_pages = 0;
 329         /*
 330          * blkif->rings was allocated in connect_ring, so we should free it in
 331          * here.
 332          */
 333         kfree(blkif->rings);
 334         blkif->rings = NULL;
 335         blkif->nr_rings = 0;
 336
 337         return 0;
 338 }
 339
 340 static void xen_blkif_free(struct xen_blkif *blkif)
 341 {
 342         WARN_ON(xen_blkif_disconnect(blkif));
 343         xen_vbd_free(&blkif->vbd);
 344         kfree(blkif->be->mode);
 345         kfree(blkif->be);
 346
 347         /* Make sure everything is drained before shutting down */
 348         kmem_cache_free(xen_blkif_cachep, blkif);
 349         module_put(THIS_MODULE);
 350 }
 351
 352 int __init xen_blkif_interface_init(void)
 353 {
 354         xen_blkif_cachep = kmem_cache_create("blkif_cache",
 355                                              sizeof(struct xen_blkif),
 356                                              0, 0, NULL);
 357         if (!xen_blkif_cachep)
 358                 return -ENOMEM;
 359
 360         return 0;
 361 }
 362
 363 void xen_blkif_interface_fini(void)
 364 {
 365         kmem_cache_destroy(xen_blkif_cachep);
 366         xen_blkif_cachep = NULL;
 367 }
 368
 369 /*
 370  *  sysfs interface for VBD I/O requests
 371  */
 372
 373 #define VBD_SHOW_ALLRING(name, format)                                  \
 374         static ssize_t show_##name(struct device *_dev,                 \
 375                                    struct device_attribute *attr,       \
 376                                    char *buf)                           \
 377         {                                                               \
 378                 struct xenbus_device *dev = to_xenbus_device(_dev);     \
 379                 struct backend_info *be = dev_get_drvdata(&dev->dev);   \
 380                 struct xen_blkif *blkif = be->blkif;                    \
 381                 unsigned int i;                                         \
 382                 unsigned long long result = 0;                          \
 383                                                                         \
 384                 if (!blkif->rings)                              \
 385                         goto out;                                       \
 386                                                                         \
 387                 for (i = 0; i < blkif->nr_rings; i++) {         \
 388                         struct xen_blkif_ring *ring = &blkif->rings[i]; \
 389                                                                         \
 390                         result += ring->st_##name;                      \
 391                 }                                                       \
 392                                                                         \
 393 out:                                                                    \
 394                 return sprintf(buf, format, result);                    \
 395         }                                                               \
 396         static DEVICE_ATTR(name, 0444, show_##name, NULL)
 397
 398 VBD_SHOW_ALLRING(oo_req,  "%llu\n");
 399 VBD_SHOW_ALLRING(rd_req,  "%llu\n");
 400 VBD_SHOW_ALLRING(wr_req,  "%llu\n");
 401 VBD_SHOW_ALLRING(f_req,  "%llu\n");
 402 VBD_SHOW_ALLRING(ds_req,  "%llu\n");
 403 VBD_SHOW_ALLRING(rd_sect, "%llu\n");
 404 VBD_SHOW_ALLRING(wr_sect, "%llu\n");
 405
 406 static struct attribute *xen_vbdstat_attrs[] = {
 407         &dev_attr_oo_req.attr,
 408         &dev_attr_rd_req.attr,
 409         &dev_attr_wr_req.attr,
 410         &dev_attr_f_req.attr,
 411         &dev_attr_ds_req.attr,
 412         &dev_attr_rd_sect.attr,
 413         &dev_attr_wr_sect.attr,
 414         NULL
 415 };
 416
 417 static const struct attribute_group xen_vbdstat_group = {
 418         .name = "statistics",
 419         .attrs = xen_vbdstat_attrs,
 420 };
 421
 422 #define VBD_SHOW(name, format, args...)                                 \
 423         static ssize_t show_##name(struct device *_dev,                 \
 424                                    struct device_attribute *attr,       \
 425                                    char *buf)                           \
 426         {                                                               \
 427                 struct xenbus_device *dev = to_xenbus_device(_dev);     \
 428                 struct backend_info *be = dev_get_drvdata(&dev->dev);   \
 429                                                                         \
 430                 return sprintf(buf, format, ##args);                    \
 431         }                                                               \
 432         static DEVICE_ATTR(name, 0444, show_##name, NULL)
 433
 434 VBD_SHOW(physical_device, "%x:%x\n", be->major, be->minor);
 435 VBD_SHOW(mode, "%s\n", be->mode);
 436
 437 static int xenvbd_sysfs_addif(struct xenbus_device *dev)
 438 {
 439         int error;
 440
 441         error = device_create_file(&dev->dev, &dev_attr_physical_device);
 442         if (error)
 443                 goto fail1;
 444
 445         error = device_create_file(&dev->dev, &dev_attr_mode);
 446         if (error)
 447                 goto fail2;
 448
 449         error = sysfs_create_group(&dev->dev.kobj, &xen_vbdstat_group);
 450         if (error)
 451                 goto fail3;
 452
 453         return 0;
 454
 455 fail3:  sysfs_remove_group(&dev->dev.kobj, &xen_vbdstat_group);
 456 fail2:  device_remove_file(&dev->dev, &dev_attr_mode);
 457 fail1:  device_remove_file(&dev->dev, &dev_attr_physical_device);
 458         return error;
 459 }
 460
 461 static void xenvbd_sysfs_delif(struct xenbus_device *dev)
 462 {
 463         sysfs_remove_group(&dev->dev.kobj, &xen_vbdstat_group);
 464         device_remove_file(&dev->dev, &dev_attr_mode);
 465         device_remove_file(&dev->dev, &dev_attr_physical_device);
 466 }
 467
 468 static void xen_vbd_free(struct xen_vbd *vbd)
 469 {
 470         if (vbd->bdev)
 471                 blkdev_put(vbd->bdev, vbd->readonly ? FMODE_READ : FMODE_WRITE);
 472         vbd->bdev = NULL;
 473 }
 474
 475 /* Enable the persistent grants feature. */
 476 static bool feature_persistent = true;
 477 module_param(feature_persistent, bool, 0644);
 478 MODULE_PARM_DESC(feature_persistent,
 479                 "Enables the persistent grants feature");
 480
 481 static int xen_vbd_create(struct xen_blkif *blkif, blkif_vdev_t handle,
 482                           unsigned major, unsigned minor, int readonly,
 483                           int cdrom)
 484 {
 485         struct xen_vbd *vbd;
 486         struct block_device *bdev;
 487         struct request_queue *q;
 488
 489         vbd = &blkif->vbd;
 490         vbd->handle   = handle;
 491         vbd->readonly = readonly;
 492         vbd->type     = 0;
 493
 494         vbd->pdevice  = MKDEV(major, minor);
 495
 496         bdev = blkdev_get_by_dev(vbd->pdevice, vbd->readonly ?
 497                                  FMODE_READ : FMODE_WRITE, NULL);
 498
 499         if (IS_ERR(bdev)) {
 500                 pr_warn("xen_vbd_create: device %08x could not be opened\n",
 501                         vbd->pdevice);
 502                 return -ENOENT;
 503         }
 504
 505         vbd->bdev = bdev;
 506         if (vbd->bdev->bd_disk == NULL) {
 507                 pr_warn("xen_vbd_create: device %08x doesn't exist\n",
 508                         vbd->pdevice);
 509                 xen_vbd_free(vbd);
 510                 return -ENOENT;
 511         }
 512         vbd->size = vbd_sz(vbd);
 513
 514         if (vbd->bdev->bd_disk->flags & GENHD_FL_CD || cdrom)
 515                 vbd->type |= VDISK_CDROM;
 516         if (vbd->bdev->bd_disk->flags & GENHD_FL_REMOVABLE)
 517                 vbd->type |= VDISK_REMOVABLE;
 518
 519         q = bdev_get_queue(bdev);
 520         if (q && test_bit(QUEUE_FLAG_WC, &q->queue_flags))
 521                 vbd->flush_support = true;
 522
 523         if (q && blk_queue_secure_erase(q))
 524                 vbd->discard_secure = true;
 525
 526         vbd->feature_gnt_persistent = feature_persistent;
 527
 528         pr_debug("Successful creation of handle=%04x (dom=%u)\n",
 529                 handle, blkif->domid);
 530         return 0;
 531 }
 532
 533 static int xen_blkbk_remove(struct xenbus_device *dev)
 534 {
 535         struct backend_info *be = dev_get_drvdata(&dev->dev);
 536
 537         pr_debug("%s %p %d\n", __func__, dev, dev->otherend_id);
 538
 539         if (be->major || be->minor)
 540                 xenvbd_sysfs_delif(dev);
 541
 542         if (be->backend_watch.node) {
 543                 unregister_xenbus_watch(&be->backend_watch);
 544                 kfree(be->backend_watch.node);
 545                 be->backend_watch.node = NULL;
 546         }
 547
 548         dev_set_drvdata(&dev->dev, NULL);
 549
 550         if (be->blkif) {
 551                 xen_blkif_disconnect(be->blkif);
 552
 553                 /* Put the reference we set in xen_blkif_alloc(). */
 554                 xen_blkif_put(be->blkif);
 555         }
 556
 557         return 0;
 558 }
 559
 560 int xen_blkbk_flush_diskcache(struct xenbus_transaction xbt,
 561                               struct backend_info *be, int state)
 562 {
 563         struct xenbus_device *dev = be->dev;
 564         int err;
 565
 566         err = xenbus_printf(xbt, dev->nodename, "feature-flush-cache",
 567                             "%d", state);
 568         if (err)
 569                 dev_warn(&dev->dev, "writing feature-flush-cache (%d)", err);
 570
 571         return err;
 572 }
 573
 574 static void xen_blkbk_discard(struct xenbus_transaction xbt, struct backend_info *be)
 575 {
 576         struct xenbus_device *dev = be->dev;
 577         struct xen_blkif *blkif = be->blkif;
 578         int err;
 579         int state = 0;
 580         struct block_device *bdev = be->blkif->vbd.bdev;
 581         struct request_queue *q = bdev_get_queue(bdev);
 582
 583         if (!xenbus_read_unsigned(dev->nodename, "discard-enable", 1))
 584                 return;
 585
 586         if (blk_queue_discard(q)) {
 587                 err = xenbus_printf(xbt, dev->nodename,
 588                         "discard-granularity", "%u",
 589                         q->limits.discard_granularity);
 590                 if (err) {
 591                         dev_warn(&dev->dev, "writing discard-granularity (%d)", err);
 592                         return;
 593                 }
 594                 err = xenbus_printf(xbt, dev->nodename,
 595                         "discard-alignment", "%u",
 596                         q->limits.discard_alignment);
 597                 if (err) {
 598                         dev_warn(&dev->dev, "writing discard-alignment (%d)", err);
 599                         return;
 600                 }
 601                 state = 1;
 602                 /* Optional. */
 603                 err = xenbus_printf(xbt, dev->nodename,
 604                                     "discard-secure", "%d",
 605                                     blkif->vbd.discard_secure);
 606                 if (err) {
 607                         dev_warn(&dev->dev, "writing discard-secure (%d)", err);
 608                         return;
 609                 }
 610         }
 611         err = xenbus_printf(xbt, dev->nodename, "feature-discard",
 612                             "%d", state);
 613         if (err)
 614                 dev_warn(&dev->dev, "writing feature-discard (%d)", err);
 615 }
 616
 617 int xen_blkbk_barrier(struct xenbus_transaction xbt,
 618                       struct backend_info *be, int state)
 619 {
 620         struct xenbus_device *dev = be->dev;
 621         int err;
 622
 623         err = xenbus_printf(xbt, dev->nodename, "feature-barrier",
 624                             "%d", state);
 625         if (err)
 626                 dev_warn(&dev->dev, "writing feature-barrier (%d)", err);
 627
 628         return err;
 629 }
 630
 631 /*
 632  * Entry point to this code when a new device is created.  Allocate the basic
 633  * structures, and watch the store waiting for the hotplug scripts to tell us
 634  * the device's physical major and minor numbers.  Switch to InitWait.
 635  */
 636 static int xen_blkbk_probe(struct xenbus_device *dev,
 637                            const struct xenbus_device_id *id)
 638 {
 639         int err;
 640         struct backend_info *be = kzalloc(sizeof(struct backend_info),
 641                                           GFP_KERNEL);
 642
 643         /* match the pr_debug in xen_blkbk_remove */
 644         pr_debug("%s %p %d\n", __func__, dev, dev->otherend_id);
 645
 646         if (!be) {
 647                 xenbus_dev_fatal(dev, -ENOMEM,
 648                                  "allocating backend structure");
 649                 return -ENOMEM;
 650         }
 651         be->dev = dev;
 652         dev_set_drvdata(&dev->dev, be);
 653
 654         be->blkif = xen_blkif_alloc(dev->otherend_id);
 655         if (IS_ERR(be->blkif)) {
 656                 err = PTR_ERR(be->blkif);
 657                 be->blkif = NULL;
 658                 xenbus_dev_fatal(dev, err, "creating block interface");
 659                 goto fail;
 660         }
 661
 662         err = xenbus_printf(XBT_NIL, dev->nodename,
 663                             "feature-max-indirect-segments", "%u",
 664                             MAX_INDIRECT_SEGMENTS);
 665         if (err)
 666                 dev_warn(&dev->dev,
 667                          "writing %s/feature-max-indirect-segments (%d)",
 668                          dev->nodename, err);
 669
 670         /* Multi-queue: advertise how many queues are supported by us.*/
 671         err = xenbus_printf(XBT_NIL, dev->nodename,
 672                             "multi-queue-max-queues", "%u", xenblk_max_queues);
 673         if (err)
 674                 pr_warn("Error writing multi-queue-max-queues\n");
 675
 676         /* setup back pointer */
 677         be->blkif->be = be;
 678
 679         err = xenbus_watch_pathfmt(dev, &be->backend_watch, NULL,
 680                                    backend_changed,
 681                                    "%s/%s", dev->nodename, "physical-device");
 682         if (err)
 683                 goto fail;
 684
 685         err = xenbus_printf(XBT_NIL, dev->nodename, "max-ring-page-order", "%u",
 686                             xen_blkif_max_ring_order);
 687         if (err)
 688                 pr_warn("%s write out 'max-ring-page-order' failed\n", __func__);
 689
 690         err = xenbus_switch_state(dev, XenbusStateInitWait);
 691         if (err)
 692                 goto fail;
 693
 694         return 0;
 695
 696 fail:
 697         pr_warn("%s failed\n", __func__);
 698         xen_blkbk_remove(dev);
 699         return err;
 700 }
 701
 702 /*
 703  * Callback received when the hotplug scripts have placed the physical-device
 704  * node.  Read it and the mode node, and create a vbd.  If the frontend is
 705  * ready, connect.
 706  */
 707 static void backend_changed(struct xenbus_watch *watch,
 708                             const char *path, const char *token)
 709 {
 710         int err;
 711         unsigned major;
 712         unsigned minor;
 713         struct backend_info *be
 714                 = container_of(watch, struct backend_info, backend_watch);
 715         struct xenbus_device *dev = be->dev;
 716         int cdrom = 0;
 717         unsigned long handle;
 718         char *device_type;
 719
 720         pr_debug("%s %p %d\n", __func__, dev, dev->otherend_id);
 721
 722         err = xenbus_scanf(XBT_NIL, dev->nodename, "physical-device", "%x:%x",
 723                            &major, &minor);
 724         if (XENBUS_EXIST_ERR(err)) {
 725                 /*
 726                  * Since this watch will fire once immediately after it is
 727                  * registered, we expect this.  Ignore it, and wait for the
 728                  * hotplug scripts.
 729                  */
 730                 return;
 731         }
 732         if (err != 2) {
 733                 xenbus_dev_fatal(dev, err, "reading physical-device");
 734                 return;
 735         }
 736
 737         if (be->major | be->minor) {
 738                 if (be->major != major || be->minor != minor)
 739                         pr_warn("changing physical device (from %x:%x to %x:%x) not supported.\n",
 740                                 be->major, be->minor, major, minor);
 741                 return;
 742         }
 743
 744         be->mode = xenbus_read(XBT_NIL, dev->nodename, "mode", NULL);
 745         if (IS_ERR(be->mode)) {
 746                 err = PTR_ERR(be->mode);
 747                 be->mode = NULL;
 748                 xenbus_dev_fatal(dev, err, "reading mode");
 749                 return;
 750         }
 751
 752         device_type = xenbus_read(XBT_NIL, dev->otherend, "device-type", NULL);
 753         if (!IS_ERR(device_type)) {
 754                 cdrom = strcmp(device_type, "cdrom") == 0;
 755                 kfree(device_type);
 756         }
 757
 758         /* Front end dir is a number, which is used as the handle. */
 759         err = kstrtoul(strrchr(dev->otherend, '/') + 1, 0, &handle);
 760         if (err) {
 761                 kfree(be->mode);
 762                 be->mode = NULL;
 763                 return;
 764         }
 765
 766         be->major = major;
 767         be->minor = minor;
 768
 769         err = xen_vbd_create(be->blkif, handle, major, minor,
 770                              !strchr(be->mode, 'w'), cdrom);
 771
 772         if (err)
 773                 xenbus_dev_fatal(dev, err, "creating vbd structure");
 774         else {
 775                 err = xenvbd_sysfs_addif(dev);
 776                 if (err) {
 777                         xen_vbd_free(&be->blkif->vbd);
 778                         xenbus_dev_fatal(dev, err, "creating sysfs entries");
 779                 }
 780         }
 781
 782         if (err) {
 783                 kfree(be->mode);
 784                 be->mode = NULL;
 785                 be->major = 0;
 786                 be->minor = 0;
 787         } else {
 788                 /* We're potentially connected now */
 789                 xen_update_blkif_status(be->blkif);
 790         }
 791 }
 792
 793 /*
 794  * Callback received when the frontend's state changes.
 795  */
 796 static void frontend_changed(struct xenbus_device *dev,
 797                              enum xenbus_state frontend_state)
 798 {
 799         struct backend_info *be = dev_get_drvdata(&dev->dev);
 800         int err;
 801
 802         pr_debug("%s %p %s\n", __func__, dev, xenbus_strstate(frontend_state));
 803
 804         switch (frontend_state) {
 805         case XenbusStateInitialising:
 806                 if (dev->state == XenbusStateClosed) {
 807                         pr_info("%s: prepare for reconnect\n", dev->nodename);
 808                         xenbus_switch_state(dev, XenbusStateInitWait);
 809                 }
 810                 break;
 811
 812         case XenbusStateInitialised:
 813         case XenbusStateConnected:
 814                 /*
 815                  * Ensure we connect even when two watches fire in
 816                  * close succession and we miss the intermediate value
 817                  * of frontend_state.
 818                  */
 819                 if (dev->state == XenbusStateConnected)
 820                         break;
 821
 822                 /*
 823                  * Enforce precondition before potential leak point.
 824                  * xen_blkif_disconnect() is idempotent.
 825                  */
 826                 err = xen_blkif_disconnect(be->blkif);
 827                 if (err) {
 828                         xenbus_dev_fatal(dev, err, "pending I/O");
 829                         break;
 830                 }
 831
 832                 err = connect_ring(be);
 833                 if (err) {
 834                         /*
 835                          * Clean up so that memory resources can be used by
 836                          * other devices. connect_ring reported already error.
 837                          */
 838                         xen_blkif_disconnect(be->blkif);
 839                         break;
 840                 }
 841                 xen_update_blkif_status(be->blkif);
 842                 break;
 843
 844         case XenbusStateClosing:
 845                 xenbus_switch_state(dev, XenbusStateClosing);
 846                 break;
 847
 848         case XenbusStateClosed:
 849                 xen_blkif_disconnect(be->blkif);
 850                 xenbus_switch_state(dev, XenbusStateClosed);
 851                 if (xenbus_dev_is_online(dev))
 852                         break;
 853                 fallthrough;
 854                 /* if not online */
 855         case XenbusStateUnknown:
 856                 /* implies xen_blkif_disconnect() via xen_blkbk_remove() */
 857                 device_unregister(&dev->dev);
 858                 break;
 859
 860         default:
 861                 xenbus_dev_fatal(dev, -EINVAL, "saw state %d at frontend",
 862                                  frontend_state);
 863                 break;
 864         }
 865 }
 866
 867 /* Once a memory pressure is detected, squeeze free page pools for a while. */
 868 static unsigned int buffer_squeeze_duration_ms = 10;
 869 module_param_named(buffer_squeeze_duration_ms,
 870                 buffer_squeeze_duration_ms, int, 0644);
 871 MODULE_PARM_DESC(buffer_squeeze_duration_ms,
 872 "Duration in ms to squeeze pages buffer when a memory pressure is detected");
 873
 874 /*
 875  * Callback received when the memory pressure is detected.
 876  */
 877 static void reclaim_memory(struct xenbus_device *dev)
 878 {
 879         struct backend_info *be = dev_get_drvdata(&dev->dev);
 880
 881         if (!be)
 882                 return;
 883         be->blkif->buffer_squeeze_end = jiffies +
 884                 msecs_to_jiffies(buffer_squeeze_duration_ms);
 885 }
 886
 887 /* ** Connection ** */
 888
 889 /*
 890  * Write the physical details regarding the block device to the store, and
 891  * switch to Connected state.
 892  */
 893 static void connect(struct backend_info *be)
 894 {
 895         struct xenbus_transaction xbt;
 896         int err;
 897         struct xenbus_device *dev = be->dev;
 898
 899         pr_debug("%s %s\n", __func__, dev->otherend);
 900
 901         /* Supply the information about the device the frontend needs */
 902 again:
 903         err = xenbus_transaction_start(&xbt);
 904         if (err) {
 905                 xenbus_dev_fatal(dev, err, "starting transaction");
 906                 return;
 907         }
 908
 909         /* If we can't advertise it is OK. */
 910         xen_blkbk_flush_diskcache(xbt, be, be->blkif->vbd.flush_support);
 911
 912         xen_blkbk_discard(xbt, be);
 913
 914         xen_blkbk_barrier(xbt, be, be->blkif->vbd.flush_support);
 915
 916         err = xenbus_printf(xbt, dev->nodename, "feature-persistent", "%u",
 917                         be->blkif->vbd.feature_gnt_persistent);
 918         if (err) {
 919                 xenbus_dev_fatal(dev, err, "writing %s/feature-persistent",
 920                                  dev->nodename);
 921                 goto abort;
 922         }
 923
 924         err = xenbus_printf(xbt, dev->nodename, "sectors", "%llu",
 925                             (unsigned long long)vbd_sz(&be->blkif->vbd));
 926         if (err) {
 927                 xenbus_dev_fatal(dev, err, "writing %s/sectors",
 928                                  dev->nodename);
 929                 goto abort;
 930         }
 931
 932         /* FIXME: use a typename instead */
 933         err = xenbus_printf(xbt, dev->nodename, "info", "%u",
 934                             be->blkif->vbd.type |
 935                             (be->blkif->vbd.readonly ? VDISK_READONLY : 0));
 936         if (err) {
 937                 xenbus_dev_fatal(dev, err, "writing %s/info",
 938                                  dev->nodename);
 939                 goto abort;
 940         }
 941         err = xenbus_printf(xbt, dev->nodename, "sector-size", "%lu",
 942                             (unsigned long)
 943                             bdev_logical_block_size(be->blkif->vbd.bdev));
 944         if (err) {
 945                 xenbus_dev_fatal(dev, err, "writing %s/sector-size",
 946                                  dev->nodename);
 947                 goto abort;
 948         }
 949         err = xenbus_printf(xbt, dev->nodename, "physical-sector-size", "%u",
 950                             bdev_physical_block_size(be->blkif->vbd.bdev));
 951         if (err)
 952                 xenbus_dev_error(dev, err, "writing %s/physical-sector-size",
 953                                  dev->nodename);
 954
 955         err = xenbus_transaction_end(xbt, 0);
 956         if (err == -EAGAIN)
 957                 goto again;
 958         if (err)
 959                 xenbus_dev_fatal(dev, err, "ending transaction");
 960
 961         err = xenbus_switch_state(dev, XenbusStateConnected);
 962         if (err)
 963                 xenbus_dev_fatal(dev, err, "%s: switching to Connected state",
 964                                  dev->nodename);
 965
 966         return;
 967  abort:
 968         xenbus_transaction_end(xbt, 1);
 969 }
 970
 971 /*
 972  * Each ring may have multi pages, depends on "ring-page-order".
 973  */
 974 static int read_per_ring_refs(struct xen_blkif_ring *ring, const char *dir)
 975 {
 976         unsigned int ring_ref[XENBUS_MAX_RING_GRANTS];
 977         struct pending_req *req, *n;
 978         int err, i, j;
 979         struct xen_blkif *blkif = ring->blkif;
 980         struct xenbus_device *dev = blkif->be->dev;
 981         unsigned int nr_grefs, evtchn;
 982
 983         err = xenbus_scanf(XBT_NIL, dir, "event-channel", "%u",
 984                           &evtchn);
 985         if (err != 1) {
 986                 err = -EINVAL;
 987                 xenbus_dev_fatal(dev, err, "reading %s/event-channel", dir);
 988                 return err;
 989         }
 990
 991         nr_grefs = blkif->nr_ring_pages;
 992
 993         if (unlikely(!nr_grefs)) {
 994                 WARN_ON(true);
 995                 return -EINVAL;
 996         }
 997
 998         for (i = 0; i < nr_grefs; i++) {
 999                 char ring_ref_name[RINGREF_NAME_LEN];
1000
1001                 if (blkif->multi_ref)
1002                         snprintf(ring_ref_name, RINGREF_NAME_LEN, "ring-ref%u", i);
1003                 else {
1004                         WARN_ON(i != 0);
1005                         snprintf(ring_ref_name, RINGREF_NAME_LEN, "ring-ref");
1006                 }
1007
1008                 err = xenbus_scanf(XBT_NIL, dir, ring_ref_name,
1009                                    "%u", &ring_ref[i]);
1010
1011                 if (err != 1) {
1012                         err = -EINVAL;
1013                         xenbus_dev_fatal(dev, err, "reading %s/%s",
1014                                          dir, ring_ref_name);
1015                         return err;
1016                 }
1017         }
1018
1019         err = -ENOMEM;
1020         for (i = 0; i < nr_grefs * XEN_BLKIF_REQS_PER_PAGE; i++) {
1021                 req = kzalloc(sizeof(*req), GFP_KERNEL);
1022                 if (!req)
1023                         goto fail;
1024                 list_add_tail(&req->free_list, &ring->pending_free);
1025                 for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++) {
1026                         req->segments[j] = kzalloc(sizeof(*req->segments[0]), GFP_KERNEL);
1027                         if (!req->segments[j])
1028                                 goto fail;
1029                 }
1030                 for (j = 0; j < MAX_INDIRECT_PAGES; j++) {
1031                         req->indirect_pages[j] = kzalloc(sizeof(*req->indirect_pages[0]),
1032                                                          GFP_KERNEL);
1033                         if (!req->indirect_pages[j])
1034                                 goto fail;
1035                 }
1036         }
1037
1038         /* Map the shared frame, irq etc. */
1039         err = xen_blkif_map(ring, ring_ref, nr_grefs, evtchn);
1040         if (err) {
1041                 xenbus_dev_fatal(dev, err, "mapping ring-ref port %u", evtchn);
1042                 goto fail;
1043         }
1044
1045         return 0;
1046
1047 fail:
1048         list_for_each_entry_safe(req, n, &ring->pending_free, free_list) {
1049                 list_del(&req->free_list);
1050                 for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++) {
1051                         if (!req->segments[j])
1052                                 break;
1053                         kfree(req->segments[j]);
1054                 }
1055                 for (j = 0; j < MAX_INDIRECT_PAGES; j++) {
1056                         if (!req->indirect_pages[j])
1057                                 break;
1058                         kfree(req->indirect_pages[j]);
1059                 }
1060                 kfree(req);
1061         }
1062         return err;
1063 }
1064
1065 static int connect_ring(struct backend_info *be)
1066 {
1067         struct xenbus_device *dev = be->dev;
1068         struct xen_blkif *blkif = be->blkif;
1069         char protocol[64] = "";
1070         int err, i;
1071         char *xspath;
1072         size_t xspathsize;
1073         const size_t xenstore_path_ext_size = 11; /* sufficient for "/queue-NNN" */
1074         unsigned int requested_num_queues = 0;
1075         unsigned int ring_page_order;
1076
1077         pr_debug("%s %s\n", __func__, dev->otherend);
1078
1079         blkif->blk_protocol = BLKIF_PROTOCOL_DEFAULT;
1080         err = xenbus_scanf(XBT_NIL, dev->otherend, "protocol",
1081                            "%63s", protocol);
1082         if (err <= 0)
1083                 strcpy(protocol, "unspecified, assuming default");
1084         else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_NATIVE))
1085                 blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
1086         else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_32))
1087                 blkif->blk_protocol = BLKIF_PROTOCOL_X86_32;
1088         else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_64))
1089                 blkif->blk_protocol = BLKIF_PROTOCOL_X86_64;
1090         else {
1091                 xenbus_dev_fatal(dev, err, "unknown fe protocol %s", protocol);
1092                 return -ENOSYS;
1093         }
1094         if (blkif->vbd.feature_gnt_persistent)
1095                 blkif->vbd.feature_gnt_persistent =
1096                         xenbus_read_unsigned(dev->otherend,
1097                                         "feature-persistent", 0);
1098
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                  blkif->vbd.feature_gnt_persistent ? "persistent grants" : "");
1122
1123         err = xenbus_scanf(XBT_NIL, dev->otherend, "ring-page-order", "%u",
1124                            &ring_page_order);
1125         if (err != 1) {
1126                 blkif->nr_ring_pages = 1;
1127                 blkif->multi_ref = false;
1128         } else if (ring_page_order <= xen_blkif_max_ring_order) {
1129                 blkif->nr_ring_pages = 1 << ring_page_order;
1130                 blkif->multi_ref = true;
1131         } else {
1132                 err = -EINVAL;
1133                 xenbus_dev_fatal(dev, err,
1134                                  "requested ring page order %d exceed max:%d",
1135                                  ring_page_order,
1136                                  xen_blkif_max_ring_order);
1137                 return err;
1138         }
1139
1140         if (blkif->nr_rings == 1)
1141                 return read_per_ring_refs(&blkif->rings[0], dev->otherend);
1142         else {
1143                 xspathsize = strlen(dev->otherend) + xenstore_path_ext_size;
1144                 xspath = kmalloc(xspathsize, GFP_KERNEL);
1145                 if (!xspath) {
1146                         xenbus_dev_fatal(dev, -ENOMEM, "reading ring references");
1147                         return -ENOMEM;
1148                 }
1149
1150                 for (i = 0; i < blkif->nr_rings; i++) {
1151                         memset(xspath, 0, xspathsize);
1152                         snprintf(xspath, xspathsize, "%s/queue-%u", dev->otherend, i);
1153                         err = read_per_ring_refs(&blkif->rings[i], xspath);
1154                         if (err) {
1155                                 kfree(xspath);
1156                                 return err;
1157                         }
1158                 }
1159                 kfree(xspath);
1160         }
1161         return 0;
1162 }
1163
1164 static const struct xenbus_device_id xen_blkbk_ids[] = {
1165         { "vbd" },
1166         { "" }
1167 };
1168
1169 static struct xenbus_driver xen_blkbk_driver = {
1170         .ids  = xen_blkbk_ids,
1171         .probe = xen_blkbk_probe,
1172         .remove = xen_blkbk_remove,
1173         .otherend_changed = frontend_changed,
1174         .allow_rebind = true,
1175         .reclaim_memory = reclaim_memory,
1176 };
1177
1178 int xen_blkif_xenbus_init(void)
1179 {
1180         return xenbus_register_backend(&xen_blkbk_driver);
1181 }
1182
1183 void xen_blkif_xenbus_fini(void)
1184 {
1185         xenbus_unregister_driver(&xen_blkbk_driver);
1186 }