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 <linux/module.h>
  12 #include <linux/kthread.h>
  13 #include <linux/pagemap.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 = sync_blockdev(blkif->vbd.bdev);
 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 /* Enable the persistent grants feature. */
 161 static bool feature_persistent = true;
 162 module_param(feature_persistent, bool, 0644);
 163 MODULE_PARM_DESC(feature_persistent, "Enables the persistent grants feature");
 164
 165 static struct xen_blkif *xen_blkif_alloc(domid_t domid)
 166 {
 167         struct xen_blkif *blkif;
 168
 169         BUILD_BUG_ON(MAX_INDIRECT_PAGES > BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST);
 170
 171         blkif = kmem_cache_zalloc(xen_blkif_cachep, GFP_KERNEL);
 172         if (!blkif)
 173                 return ERR_PTR(-ENOMEM);
 174
 175         blkif->domid = domid;
 176         atomic_set(&blkif->refcnt, 1);
 177         init_completion(&blkif->drain_complete);
 178
 179         /*
 180          * Because freeing back to the cache may be deferred, it is not
 181          * safe to unload the module (and hence destroy the cache) until
 182          * this has completed. To prevent premature unloading, take an
 183          * extra module reference here and release only when the object
 184          * has been freed back to the cache.
 185          */
 186         __module_get(THIS_MODULE);
 187         INIT_WORK(&blkif->free_work, xen_blkif_deferred_free);
 188
 189         return blkif;
 190 }
 191
 192 static int xen_blkif_map(struct xen_blkif_ring *ring, grant_ref_t *gref,
 193                          unsigned int nr_grefs, unsigned int evtchn)
 194 {
 195         int err;
 196         struct xen_blkif *blkif = ring->blkif;
 197         const struct blkif_common_sring *sring_common;
 198         RING_IDX rsp_prod, req_prod;
 199         unsigned int size;
 200
 201         /* Already connected through? */
 202         if (ring->irq)
 203                 return 0;
 204
 205         err = xenbus_map_ring_valloc(blkif->be->dev, gref, nr_grefs,
 206                                      &ring->blk_ring);
 207         if (err < 0)
 208                 return err;
 209
 210         sring_common = (struct blkif_common_sring *)ring->blk_ring;
 211         rsp_prod = READ_ONCE(sring_common->rsp_prod);
 212         req_prod = READ_ONCE(sring_common->req_prod);
 213
 214         switch (blkif->blk_protocol) {
 215         case BLKIF_PROTOCOL_NATIVE:
 216         {
 217                 struct blkif_sring *sring_native =
 218                         (struct blkif_sring *)ring->blk_ring;
 219
 220                 BACK_RING_ATTACH(&ring->blk_rings.native, sring_native,
 221                                  rsp_prod, XEN_PAGE_SIZE * nr_grefs);
 222                 size = __RING_SIZE(sring_native, XEN_PAGE_SIZE * nr_grefs);
 223                 break;
 224         }
 225         case BLKIF_PROTOCOL_X86_32:
 226         {
 227                 struct blkif_x86_32_sring *sring_x86_32 =
 228                         (struct blkif_x86_32_sring *)ring->blk_ring;
 229
 230                 BACK_RING_ATTACH(&ring->blk_rings.x86_32, sring_x86_32,
 231                                  rsp_prod, XEN_PAGE_SIZE * nr_grefs);
 232                 size = __RING_SIZE(sring_x86_32, XEN_PAGE_SIZE * nr_grefs);
 233                 break;
 234         }
 235         case BLKIF_PROTOCOL_X86_64:
 236         {
 237                 struct blkif_x86_64_sring *sring_x86_64 =
 238                         (struct blkif_x86_64_sring *)ring->blk_ring;
 239
 240                 BACK_RING_ATTACH(&ring->blk_rings.x86_64, sring_x86_64,
 241                                  rsp_prod, XEN_PAGE_SIZE * nr_grefs);
 242                 size = __RING_SIZE(sring_x86_64, XEN_PAGE_SIZE * nr_grefs);
 243                 break;
 244         }
 245         default:
 246                 BUG();
 247         }
 248
 249         err = -EIO;
 250         if (req_prod - rsp_prod > size)
 251                 goto fail;
 252
 253         err = bind_interdomain_evtchn_to_irqhandler_lateeoi(blkif->be->dev,
 254                         evtchn, xen_blkif_be_int, 0, "blkif-backend", ring);
 255         if (err < 0)
 256                 goto fail;
 257         ring->irq = err;
 258
 259         return 0;
 260
 261 fail:
 262         xenbus_unmap_ring_vfree(blkif->be->dev, ring->blk_ring);
 263         ring->blk_rings.common.sring = NULL;
 264         return err;
 265 }
 266
 267 static int xen_blkif_disconnect(struct xen_blkif *blkif)
 268 {
 269         struct pending_req *req, *n;
 270         unsigned int j, r;
 271         bool busy = false;
 272
 273         for (r = 0; r < blkif->nr_rings; r++) {
 274                 struct xen_blkif_ring *ring = &blkif->rings[r];
 275                 unsigned int i = 0;
 276
 277                 if (!ring->active)
 278                         continue;
 279
 280                 if (ring->xenblkd) {
 281                         kthread_stop(ring->xenblkd);
 282                         ring->xenblkd = NULL;
 283                         wake_up(&ring->shutdown_wq);
 284                 }
 285
 286                 /* The above kthread_stop() guarantees that at this point we
 287                  * don't have any discard_io or other_io requests. So, checking
 288                  * for inflight IO is enough.
 289                  */
 290                 if (atomic_read(&ring->inflight) > 0) {
 291                         busy = true;
 292                         continue;
 293                 }
 294
 295                 if (ring->irq) {
 296                         unbind_from_irqhandler(ring->irq, ring);
 297                         ring->irq = 0;
 298                 }
 299
 300                 if (ring->blk_rings.common.sring) {
 301                         xenbus_unmap_ring_vfree(blkif->be->dev, ring->blk_ring);
 302                         ring->blk_rings.common.sring = NULL;
 303                 }
 304
 305                 /* Remove all persistent grants and the cache of ballooned pages. */
 306                 xen_blkbk_free_caches(ring);
 307
 308                 /* Check that there is no request in use */
 309                 list_for_each_entry_safe(req, n, &ring->pending_free, free_list) {
 310                         list_del(&req->free_list);
 311
 312                         for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++)
 313                                 kfree(req->segments[j]);
 314
 315                         for (j = 0; j < MAX_INDIRECT_PAGES; j++)
 316                                 kfree(req->indirect_pages[j]);
 317
 318                         kfree(req);
 319                         i++;
 320                 }
 321
 322                 BUG_ON(atomic_read(&ring->persistent_gnt_in_use) != 0);
 323                 BUG_ON(!list_empty(&ring->persistent_purge_list));
 324                 BUG_ON(!RB_EMPTY_ROOT(&ring->persistent_gnts));
 325                 BUG_ON(ring->free_pages.num_pages != 0);
 326                 BUG_ON(ring->persistent_gnt_c != 0);
 327                 WARN_ON(i != (XEN_BLKIF_REQS_PER_PAGE * blkif->nr_ring_pages));
 328                 ring->active = false;
 329         }
 330         if (busy)
 331                 return -EBUSY;
 332
 333         blkif->nr_ring_pages = 0;
 334         /*
 335          * blkif->rings was allocated in connect_ring, so we should free it in
 336          * here.
 337          */
 338         kfree(blkif->rings);
 339         blkif->rings = NULL;
 340         blkif->nr_rings = 0;
 341
 342         return 0;
 343 }
 344
 345 static void xen_blkif_free(struct xen_blkif *blkif)
 346 {
 347         WARN_ON(xen_blkif_disconnect(blkif));
 348         xen_vbd_free(&blkif->vbd);
 349         kfree(blkif->be->mode);
 350         kfree(blkif->be);
 351
 352         /* Make sure everything is drained before shutting down */
 353         kmem_cache_free(xen_blkif_cachep, blkif);
 354         module_put(THIS_MODULE);
 355 }
 356
 357 int __init xen_blkif_interface_init(void)
 358 {
 359         xen_blkif_cachep = kmem_cache_create("blkif_cache",
 360                                              sizeof(struct xen_blkif),
 361                                              0, 0, NULL);
 362         if (!xen_blkif_cachep)
 363                 return -ENOMEM;
 364
 365         return 0;
 366 }
 367
 368 void xen_blkif_interface_fini(void)
 369 {
 370         kmem_cache_destroy(xen_blkif_cachep);
 371         xen_blkif_cachep = NULL;
 372 }
 373
 374 /*
 375  *  sysfs interface for VBD I/O requests
 376  */
 377
 378 #define VBD_SHOW_ALLRING(name, format)                                  \
 379         static ssize_t show_##name(struct device *_dev,                 \
 380                                    struct device_attribute *attr,       \
 381                                    char *buf)                           \
 382         {                                                               \
 383                 struct xenbus_device *dev = to_xenbus_device(_dev);     \
 384                 struct backend_info *be = dev_get_drvdata(&dev->dev);   \
 385                 struct xen_blkif *blkif = be->blkif;                    \
 386                 unsigned int i;                                         \
 387                 unsigned long long result = 0;                          \
 388                                                                         \
 389                 if (!blkif->rings)                              \
 390                         goto out;                                       \
 391                                                                         \
 392                 for (i = 0; i < blkif->nr_rings; i++) {         \
 393                         struct xen_blkif_ring *ring = &blkif->rings[i]; \
 394                                                                         \
 395                         result += ring->st_##name;                      \
 396                 }                                                       \
 397                                                                         \
 398 out:                                                                    \
 399                 return sprintf(buf, format, result);                    \
 400         }                                                               \
 401         static DEVICE_ATTR(name, 0444, show_##name, NULL)
 402
 403 VBD_SHOW_ALLRING(oo_req,  "%llu\n");
 404 VBD_SHOW_ALLRING(rd_req,  "%llu\n");
 405 VBD_SHOW_ALLRING(wr_req,  "%llu\n");
 406 VBD_SHOW_ALLRING(f_req,  "%llu\n");
 407 VBD_SHOW_ALLRING(ds_req,  "%llu\n");
 408 VBD_SHOW_ALLRING(rd_sect, "%llu\n");
 409 VBD_SHOW_ALLRING(wr_sect, "%llu\n");
 410
 411 static struct attribute *xen_vbdstat_attrs[] = {
 412         &dev_attr_oo_req.attr,
 413         &dev_attr_rd_req.attr,
 414         &dev_attr_wr_req.attr,
 415         &dev_attr_f_req.attr,
 416         &dev_attr_ds_req.attr,
 417         &dev_attr_rd_sect.attr,
 418         &dev_attr_wr_sect.attr,
 419         NULL
 420 };
 421
 422 static const struct attribute_group xen_vbdstat_group = {
 423         .name = "statistics",
 424         .attrs = xen_vbdstat_attrs,
 425 };
 426
 427 #define VBD_SHOW(name, format, args...)                                 \
 428         static ssize_t show_##name(struct device *_dev,                 \
 429                                    struct device_attribute *attr,       \
 430                                    char *buf)                           \
 431         {                                                               \
 432                 struct xenbus_device *dev = to_xenbus_device(_dev);     \
 433                 struct backend_info *be = dev_get_drvdata(&dev->dev);   \
 434                                                                         \
 435                 return sprintf(buf, format, ##args);                    \
 436         }                                                               \
 437         static DEVICE_ATTR(name, 0444, show_##name, NULL)
 438
 439 VBD_SHOW(physical_device, "%x:%x\n", be->major, be->minor);
 440 VBD_SHOW(mode, "%s\n", be->mode);
 441
 442 static int xenvbd_sysfs_addif(struct xenbus_device *dev)
 443 {
 444         int error;
 445
 446         error = device_create_file(&dev->dev, &dev_attr_physical_device);
 447         if (error)
 448                 goto fail1;
 449
 450         error = device_create_file(&dev->dev, &dev_attr_mode);
 451         if (error)
 452                 goto fail2;
 453
 454         error = sysfs_create_group(&dev->dev.kobj, &xen_vbdstat_group);
 455         if (error)
 456                 goto fail3;
 457
 458         return 0;
 459
 460 fail3:  sysfs_remove_group(&dev->dev.kobj, &xen_vbdstat_group);
 461 fail2:  device_remove_file(&dev->dev, &dev_attr_mode);
 462 fail1:  device_remove_file(&dev->dev, &dev_attr_physical_device);
 463         return error;
 464 }
 465
 466 static void xenvbd_sysfs_delif(struct xenbus_device *dev)
 467 {
 468         sysfs_remove_group(&dev->dev.kobj, &xen_vbdstat_group);
 469         device_remove_file(&dev->dev, &dev_attr_mode);
 470         device_remove_file(&dev->dev, &dev_attr_physical_device);
 471 }
 472
 473 static void xen_vbd_free(struct xen_vbd *vbd)
 474 {
 475         if (vbd->bdev)
 476                 blkdev_put(vbd->bdev, vbd->readonly ? FMODE_READ : FMODE_WRITE);
 477         vbd->bdev = NULL;
 478 }
 479
 480 static int xen_vbd_create(struct xen_blkif *blkif, blkif_vdev_t handle,
 481                           unsigned major, unsigned minor, int readonly,
 482                           int cdrom)
 483 {
 484         struct xen_vbd *vbd;
 485         struct block_device *bdev;
 486
 487         vbd = &blkif->vbd;
 488         vbd->handle   = handle;
 489         vbd->readonly = readonly;
 490         vbd->type     = 0;
 491
 492         vbd->pdevice  = MKDEV(major, minor);
 493
 494         bdev = blkdev_get_by_dev(vbd->pdevice, vbd->readonly ?
 495                                  FMODE_READ : FMODE_WRITE, NULL);
 496
 497         if (IS_ERR(bdev)) {
 498                 pr_warn("xen_vbd_create: device %08x could not be opened\n",
 499                         vbd->pdevice);
 500                 return -ENOENT;
 501         }
 502
 503         vbd->bdev = bdev;
 504         if (vbd->bdev->bd_disk == NULL) {
 505                 pr_warn("xen_vbd_create: device %08x doesn't exist\n",
 506                         vbd->pdevice);
 507                 xen_vbd_free(vbd);
 508                 return -ENOENT;
 509         }
 510         vbd->size = vbd_sz(vbd);
 511
 512         if (cdrom || disk_to_cdi(vbd->bdev->bd_disk))
 513                 vbd->type |= VDISK_CDROM;
 514         if (vbd->bdev->bd_disk->flags & GENHD_FL_REMOVABLE)
 515                 vbd->type |= VDISK_REMOVABLE;
 516
 517         if (bdev_write_cache(bdev))
 518                 vbd->flush_support = true;
 519         if (bdev_max_secure_erase_sectors(bdev))
 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 void 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
 552 int xen_blkbk_flush_diskcache(struct xenbus_transaction xbt,
 553                               struct backend_info *be, int state)
 554 {
 555         struct xenbus_device *dev = be->dev;
 556         int err;
 557
 558         err = xenbus_printf(xbt, dev->nodename, "feature-flush-cache",
 559                             "%d", state);
 560         if (err)
 561                 dev_warn(&dev->dev, "writing feature-flush-cache (%d)", err);
 562
 563         return err;
 564 }
 565
 566 static void xen_blkbk_discard(struct xenbus_transaction xbt, struct backend_info *be)
 567 {
 568         struct xenbus_device *dev = be->dev;
 569         struct xen_blkif *blkif = be->blkif;
 570         int err;
 571         int state = 0;
 572         struct block_device *bdev = be->blkif->vbd.bdev;
 573
 574         if (!xenbus_read_unsigned(dev->nodename, "discard-enable", 1))
 575                 return;
 576
 577         if (bdev_max_discard_sectors(bdev)) {
 578                 err = xenbus_printf(xbt, dev->nodename,
 579                         "discard-granularity", "%u",
 580                         bdev_discard_granularity(bdev));
 581                 if (err) {
 582                         dev_warn(&dev->dev, "writing discard-granularity (%d)", err);
 583                         return;
 584                 }
 585                 err = xenbus_printf(xbt, dev->nodename,
 586                         "discard-alignment", "%u",
 587                         bdev_discard_alignment(bdev));
 588                 if (err) {
 589                         dev_warn(&dev->dev, "writing discard-alignment (%d)", err);
 590                         return;
 591                 }
 592                 state = 1;
 593                 /* Optional. */
 594                 err = xenbus_printf(xbt, dev->nodename,
 595                                     "discard-secure", "%d",
 596                                     blkif->vbd.discard_secure);
 597                 if (err) {
 598                         dev_warn(&dev->dev, "writing discard-secure (%d)", err);
 599                         return;
 600                 }
 601         }
 602         err = xenbus_printf(xbt, dev->nodename, "feature-discard",
 603                             "%d", state);
 604         if (err)
 605                 dev_warn(&dev->dev, "writing feature-discard (%d)", err);
 606 }
 607
 608 int xen_blkbk_barrier(struct xenbus_transaction xbt,
 609                       struct backend_info *be, int state)
 610 {
 611         struct xenbus_device *dev = be->dev;
 612         int err;
 613
 614         err = xenbus_printf(xbt, dev->nodename, "feature-barrier",
 615                             "%d", state);
 616         if (err)
 617                 dev_warn(&dev->dev, "writing feature-barrier (%d)", err);
 618
 619         return err;
 620 }
 621
 622 /*
 623  * Entry point to this code when a new device is created.  Allocate the basic
 624  * structures, and watch the store waiting for the hotplug scripts to tell us
 625  * the device's physical major and minor numbers.  Switch to InitWait.
 626  */
 627 static int xen_blkbk_probe(struct xenbus_device *dev,
 628                            const struct xenbus_device_id *id)
 629 {
 630         int err;
 631         struct backend_info *be = kzalloc(sizeof(struct backend_info),
 632                                           GFP_KERNEL);
 633
 634         /* match the pr_debug in xen_blkbk_remove */
 635         pr_debug("%s %p %d\n", __func__, dev, dev->otherend_id);
 636
 637         if (!be) {
 638                 xenbus_dev_fatal(dev, -ENOMEM,
 639                                  "allocating backend structure");
 640                 return -ENOMEM;
 641         }
 642         be->dev = dev;
 643         dev_set_drvdata(&dev->dev, be);
 644
 645         be->blkif = xen_blkif_alloc(dev->otherend_id);
 646         if (IS_ERR(be->blkif)) {
 647                 err = PTR_ERR(be->blkif);
 648                 be->blkif = NULL;
 649                 xenbus_dev_fatal(dev, err, "creating block interface");
 650                 goto fail;
 651         }
 652
 653         err = xenbus_printf(XBT_NIL, dev->nodename,
 654                             "feature-max-indirect-segments", "%u",
 655                             MAX_INDIRECT_SEGMENTS);
 656         if (err)
 657                 dev_warn(&dev->dev,
 658                          "writing %s/feature-max-indirect-segments (%d)",
 659                          dev->nodename, err);
 660
 661         /* Multi-queue: advertise how many queues are supported by us.*/
 662         err = xenbus_printf(XBT_NIL, dev->nodename,
 663                             "multi-queue-max-queues", "%u", xenblk_max_queues);
 664         if (err)
 665                 pr_warn("Error writing multi-queue-max-queues\n");
 666
 667         /* setup back pointer */
 668         be->blkif->be = be;
 669
 670         err = xenbus_watch_pathfmt(dev, &be->backend_watch, NULL,
 671                                    backend_changed,
 672                                    "%s/%s", dev->nodename, "physical-device");
 673         if (err)
 674                 goto fail;
 675
 676         err = xenbus_printf(XBT_NIL, dev->nodename, "max-ring-page-order", "%u",
 677                             xen_blkif_max_ring_order);
 678         if (err)
 679                 pr_warn("%s write out 'max-ring-page-order' failed\n", __func__);
 680
 681         err = xenbus_switch_state(dev, XenbusStateInitWait);
 682         if (err)
 683                 goto fail;
 684
 685         return 0;
 686
 687 fail:
 688         pr_warn("%s failed\n", __func__);
 689         xen_blkbk_remove(dev);
 690         return err;
 691 }
 692
 693 /*
 694  * Callback received when the hotplug scripts have placed the physical-device
 695  * node.  Read it and the mode node, and create a vbd.  If the frontend is
 696  * ready, connect.
 697  */
 698 static void backend_changed(struct xenbus_watch *watch,
 699                             const char *path, const char *token)
 700 {
 701         int err;
 702         unsigned major;
 703         unsigned minor;
 704         struct backend_info *be
 705                 = container_of(watch, struct backend_info, backend_watch);
 706         struct xenbus_device *dev = be->dev;
 707         int cdrom = 0;
 708         unsigned long handle;
 709         char *device_type;
 710
 711         pr_debug("%s %p %d\n", __func__, dev, dev->otherend_id);
 712
 713         err = xenbus_scanf(XBT_NIL, dev->nodename, "physical-device", "%x:%x",
 714                            &major, &minor);
 715         if (XENBUS_EXIST_ERR(err)) {
 716                 /*
 717                  * Since this watch will fire once immediately after it is
 718                  * registered, we expect this.  Ignore it, and wait for the
 719                  * hotplug scripts.
 720                  */
 721                 return;
 722         }
 723         if (err != 2) {
 724                 xenbus_dev_fatal(dev, err, "reading physical-device");
 725                 return;
 726         }
 727
 728         if (be->major | be->minor) {
 729                 if (be->major != major || be->minor != minor)
 730                         pr_warn("changing physical device (from %x:%x to %x:%x) not supported.\n",
 731                                 be->major, be->minor, major, minor);
 732                 return;
 733         }
 734
 735         be->mode = xenbus_read(XBT_NIL, dev->nodename, "mode", NULL);
 736         if (IS_ERR(be->mode)) {
 737                 err = PTR_ERR(be->mode);
 738                 be->mode = NULL;
 739                 xenbus_dev_fatal(dev, err, "reading mode");
 740                 return;
 741         }
 742
 743         device_type = xenbus_read(XBT_NIL, dev->otherend, "device-type", NULL);
 744         if (!IS_ERR(device_type)) {
 745                 cdrom = strcmp(device_type, "cdrom") == 0;
 746                 kfree(device_type);
 747         }
 748
 749         /* Front end dir is a number, which is used as the handle. */
 750         err = kstrtoul(strrchr(dev->otherend, '/') + 1, 0, &handle);
 751         if (err) {
 752                 kfree(be->mode);
 753                 be->mode = NULL;
 754                 return;
 755         }
 756
 757         be->major = major;
 758         be->minor = minor;
 759
 760         err = xen_vbd_create(be->blkif, handle, major, minor,
 761                              !strchr(be->mode, 'w'), cdrom);
 762
 763         if (err)
 764                 xenbus_dev_fatal(dev, err, "creating vbd structure");
 765         else {
 766                 err = xenvbd_sysfs_addif(dev);
 767                 if (err) {
 768                         xen_vbd_free(&be->blkif->vbd);
 769                         xenbus_dev_fatal(dev, err, "creating sysfs entries");
 770                 }
 771         }
 772
 773         if (err) {
 774                 kfree(be->mode);
 775                 be->mode = NULL;
 776                 be->major = 0;
 777                 be->minor = 0;
 778         } else {
 779                 /* We're potentially connected now */
 780                 xen_update_blkif_status(be->blkif);
 781         }
 782 }
 783
 784 /*
 785  * Callback received when the frontend's state changes.
 786  */
 787 static void frontend_changed(struct xenbus_device *dev,
 788                              enum xenbus_state frontend_state)
 789 {
 790         struct backend_info *be = dev_get_drvdata(&dev->dev);
 791         int err;
 792
 793         pr_debug("%s %p %s\n", __func__, dev, xenbus_strstate(frontend_state));
 794
 795         switch (frontend_state) {
 796         case XenbusStateInitialising:
 797                 if (dev->state == XenbusStateClosed) {
 798                         pr_info("%s: prepare for reconnect\n", dev->nodename);
 799                         xenbus_switch_state(dev, XenbusStateInitWait);
 800                 }
 801                 break;
 802
 803         case XenbusStateInitialised:
 804         case XenbusStateConnected:
 805                 /*
 806                  * Ensure we connect even when two watches fire in
 807                  * close succession and we miss the intermediate value
 808                  * of frontend_state.
 809                  */
 810                 if (dev->state == XenbusStateConnected)
 811                         break;
 812
 813                 /*
 814                  * Enforce precondition before potential leak point.
 815                  * xen_blkif_disconnect() is idempotent.
 816                  */
 817                 err = xen_blkif_disconnect(be->blkif);
 818                 if (err) {
 819                         xenbus_dev_fatal(dev, err, "pending I/O");
 820                         break;
 821                 }
 822
 823                 err = connect_ring(be);
 824                 if (err) {
 825                         /*
 826                          * Clean up so that memory resources can be used by
 827                          * other devices. connect_ring reported already error.
 828                          */
 829                         xen_blkif_disconnect(be->blkif);
 830                         break;
 831                 }
 832                 xen_update_blkif_status(be->blkif);
 833                 break;
 834
 835         case XenbusStateClosing:
 836                 xenbus_switch_state(dev, XenbusStateClosing);
 837                 break;
 838
 839         case XenbusStateClosed:
 840                 xen_blkif_disconnect(be->blkif);
 841                 xenbus_switch_state(dev, XenbusStateClosed);
 842                 if (xenbus_dev_is_online(dev))
 843                         break;
 844                 fallthrough;
 845                 /* if not online */
 846         case XenbusStateUnknown:
 847                 /* implies xen_blkif_disconnect() via xen_blkbk_remove() */
 848                 device_unregister(&dev->dev);
 849                 break;
 850
 851         default:
 852                 xenbus_dev_fatal(dev, -EINVAL, "saw state %d at frontend",
 853                                  frontend_state);
 854                 break;
 855         }
 856 }
 857
 858 /* Once a memory pressure is detected, squeeze free page pools for a while. */
 859 static unsigned int buffer_squeeze_duration_ms = 10;
 860 module_param_named(buffer_squeeze_duration_ms,
 861                 buffer_squeeze_duration_ms, int, 0644);
 862 MODULE_PARM_DESC(buffer_squeeze_duration_ms,
 863 "Duration in ms to squeeze pages buffer when a memory pressure is detected");
 864
 865 /*
 866  * Callback received when the memory pressure is detected.
 867  */
 868 static void reclaim_memory(struct xenbus_device *dev)
 869 {
 870         struct backend_info *be = dev_get_drvdata(&dev->dev);
 871
 872         if (!be)
 873                 return;
 874         be->blkif->buffer_squeeze_end = jiffies +
 875                 msecs_to_jiffies(buffer_squeeze_duration_ms);
 876 }
 877
 878 /* ** Connection ** */
 879
 880 /*
 881  * Write the physical details regarding the block device to the store, and
 882  * switch to Connected state.
 883  */
 884 static void connect(struct backend_info *be)
 885 {
 886         struct xenbus_transaction xbt;
 887         int err;
 888         struct xenbus_device *dev = be->dev;
 889
 890         pr_debug("%s %s\n", __func__, dev->otherend);
 891
 892         /* Supply the information about the device the frontend needs */
 893 again:
 894         err = xenbus_transaction_start(&xbt);
 895         if (err) {
 896                 xenbus_dev_fatal(dev, err, "starting transaction");
 897                 return;
 898         }
 899
 900         /* If we can't advertise it is OK. */
 901         xen_blkbk_flush_diskcache(xbt, be, be->blkif->vbd.flush_support);
 902
 903         xen_blkbk_discard(xbt, be);
 904
 905         xen_blkbk_barrier(xbt, be, be->blkif->vbd.flush_support);
 906
 907         err = xenbus_printf(xbt, dev->nodename, "feature-persistent", "%u",
 908                         be->blkif->vbd.feature_gnt_persistent_parm);
 909         if (err) {
 910                 xenbus_dev_fatal(dev, err, "writing %s/feature-persistent",
 911                                  dev->nodename);
 912                 goto abort;
 913         }
 914
 915         err = xenbus_printf(xbt, dev->nodename, "sectors", "%llu",
 916                             (unsigned long long)vbd_sz(&be->blkif->vbd));
 917         if (err) {
 918                 xenbus_dev_fatal(dev, err, "writing %s/sectors",
 919                                  dev->nodename);
 920                 goto abort;
 921         }
 922
 923         /* FIXME: use a typename instead */
 924         err = xenbus_printf(xbt, dev->nodename, "info", "%u",
 925                             be->blkif->vbd.type |
 926                             (be->blkif->vbd.readonly ? VDISK_READONLY : 0));
 927         if (err) {
 928                 xenbus_dev_fatal(dev, err, "writing %s/info",
 929                                  dev->nodename);
 930                 goto abort;
 931         }
 932         err = xenbus_printf(xbt, dev->nodename, "sector-size", "%lu",
 933                             (unsigned long)
 934                             bdev_logical_block_size(be->blkif->vbd.bdev));
 935         if (err) {
 936                 xenbus_dev_fatal(dev, err, "writing %s/sector-size",
 937                                  dev->nodename);
 938                 goto abort;
 939         }
 940         err = xenbus_printf(xbt, dev->nodename, "physical-sector-size", "%u",
 941                             bdev_physical_block_size(be->blkif->vbd.bdev));
 942         if (err)
 943                 xenbus_dev_error(dev, err, "writing %s/physical-sector-size",
 944                                  dev->nodename);
 945
 946         err = xenbus_transaction_end(xbt, 0);
 947         if (err == -EAGAIN)
 948                 goto again;
 949         if (err)
 950                 xenbus_dev_fatal(dev, err, "ending transaction");
 951
 952         err = xenbus_switch_state(dev, XenbusStateConnected);
 953         if (err)
 954                 xenbus_dev_fatal(dev, err, "%s: switching to Connected state",
 955                                  dev->nodename);
 956
 957         return;
 958  abort:
 959         xenbus_transaction_end(xbt, 1);
 960 }
 961
 962 /*
 963  * Each ring may have multi pages, depends on "ring-page-order".
 964  */
 965 static int read_per_ring_refs(struct xen_blkif_ring *ring, const char *dir)
 966 {
 967         unsigned int ring_ref[XENBUS_MAX_RING_GRANTS];
 968         struct pending_req *req, *n;
 969         int err, i, j;
 970         struct xen_blkif *blkif = ring->blkif;
 971         struct xenbus_device *dev = blkif->be->dev;
 972         unsigned int nr_grefs, evtchn;
 973
 974         err = xenbus_scanf(XBT_NIL, dir, "event-channel", "%u",
 975                           &evtchn);
 976         if (err != 1) {
 977                 err = -EINVAL;
 978                 xenbus_dev_fatal(dev, err, "reading %s/event-channel", dir);
 979                 return err;
 980         }
 981
 982         nr_grefs = blkif->nr_ring_pages;
 983
 984         if (unlikely(!nr_grefs)) {
 985                 WARN_ON(true);
 986                 return -EINVAL;
 987         }
 988
 989         for (i = 0; i < nr_grefs; i++) {
 990                 char ring_ref_name[RINGREF_NAME_LEN];
 991
 992                 if (blkif->multi_ref)
 993                         snprintf(ring_ref_name, RINGREF_NAME_LEN, "ring-ref%u", i);
 994                 else {
 995                         WARN_ON(i != 0);
 996                         snprintf(ring_ref_name, RINGREF_NAME_LEN, "ring-ref");
 997                 }
 998
 999                 err = xenbus_scanf(XBT_NIL, dir, ring_ref_name,
1000                                    "%u", &ring_ref[i]);
1001
1002                 if (err != 1) {
1003                         err = -EINVAL;
1004                         xenbus_dev_fatal(dev, err, "reading %s/%s",
1005                                          dir, ring_ref_name);
1006                         return err;
1007                 }
1008         }
1009
1010         err = -ENOMEM;
1011         for (i = 0; i < nr_grefs * XEN_BLKIF_REQS_PER_PAGE; i++) {
1012                 req = kzalloc(sizeof(*req), GFP_KERNEL);
1013                 if (!req)
1014                         goto fail;
1015                 list_add_tail(&req->free_list, &ring->pending_free);
1016                 for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++) {
1017                         req->segments[j] = kzalloc(sizeof(*req->segments[0]), GFP_KERNEL);
1018                         if (!req->segments[j])
1019                                 goto fail;
1020                 }
1021                 for (j = 0; j < MAX_INDIRECT_PAGES; j++) {
1022                         req->indirect_pages[j] = kzalloc(sizeof(*req->indirect_pages[0]),
1023                                                          GFP_KERNEL);
1024                         if (!req->indirect_pages[j])
1025                                 goto fail;
1026                 }
1027         }
1028
1029         /* Map the shared frame, irq etc. */
1030         err = xen_blkif_map(ring, ring_ref, nr_grefs, evtchn);
1031         if (err) {
1032                 xenbus_dev_fatal(dev, err, "mapping ring-ref port %u", evtchn);
1033                 goto fail;
1034         }
1035
1036         return 0;
1037
1038 fail:
1039         list_for_each_entry_safe(req, n, &ring->pending_free, free_list) {
1040                 list_del(&req->free_list);
1041                 for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++) {
1042                         if (!req->segments[j])
1043                                 break;
1044                         kfree(req->segments[j]);
1045                 }
1046                 for (j = 0; j < MAX_INDIRECT_PAGES; j++) {
1047                         if (!req->indirect_pages[j])
1048                                 break;
1049                         kfree(req->indirect_pages[j]);
1050                 }
1051                 kfree(req);
1052         }
1053         return err;
1054 }
1055
1056 static int connect_ring(struct backend_info *be)
1057 {
1058         struct xenbus_device *dev = be->dev;
1059         struct xen_blkif *blkif = be->blkif;
1060         char protocol[64] = "";
1061         int err, i;
1062         char *xspath;
1063         size_t xspathsize;
1064         const size_t xenstore_path_ext_size = 11; /* sufficient for "/queue-NNN" */
1065         unsigned int requested_num_queues = 0;
1066         unsigned int ring_page_order;
1067
1068         pr_debug("%s %s\n", __func__, dev->otherend);
1069
1070         blkif->blk_protocol = BLKIF_PROTOCOL_DEFAULT;
1071         err = xenbus_scanf(XBT_NIL, dev->otherend, "protocol",
1072                            "%63s", protocol);
1073         if (err <= 0)
1074                 strcpy(protocol, "unspecified, assuming default");
1075         else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_NATIVE))
1076                 blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
1077         else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_32))
1078                 blkif->blk_protocol = BLKIF_PROTOCOL_X86_32;
1079         else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_64))
1080                 blkif->blk_protocol = BLKIF_PROTOCOL_X86_64;
1081         else {
1082                 xenbus_dev_fatal(dev, err, "unknown fe protocol %s", protocol);
1083                 return -ENOSYS;
1084         }
1085
1086         blkif->vbd.feature_gnt_persistent_parm = feature_persistent;
1087         blkif->vbd.feature_gnt_persistent =
1088                 blkif->vbd.feature_gnt_persistent_parm &&
1089                 xenbus_read_unsigned(dev->otherend, "feature-persistent", 0);
1090
1091         blkif->vbd.overflow_max_grants = 0;
1092
1093         /*
1094          * Read the number of hardware queues from frontend.
1095          */
1096         requested_num_queues = xenbus_read_unsigned(dev->otherend,
1097                                                     "multi-queue-num-queues",
1098                                                     1);
1099         if (requested_num_queues > xenblk_max_queues
1100             || requested_num_queues == 0) {
1101                 /* Buggy or malicious guest. */
1102                 xenbus_dev_fatal(dev, err,
1103                                 "guest requested %u queues, exceeding the maximum of %u.",
1104                                 requested_num_queues, xenblk_max_queues);
1105                 return -ENOSYS;
1106         }
1107         blkif->nr_rings = requested_num_queues;
1108         if (xen_blkif_alloc_rings(blkif))
1109                 return -ENOMEM;
1110
1111         pr_info("%s: using %d queues, protocol %d (%s) %s\n", dev->nodename,
1112                  blkif->nr_rings, blkif->blk_protocol, protocol,
1113                  blkif->vbd.feature_gnt_persistent ? "persistent grants" : "");
1114
1115         err = xenbus_scanf(XBT_NIL, dev->otherend, "ring-page-order", "%u",
1116                            &ring_page_order);
1117         if (err != 1) {
1118                 blkif->nr_ring_pages = 1;
1119                 blkif->multi_ref = false;
1120         } else if (ring_page_order <= xen_blkif_max_ring_order) {
1121                 blkif->nr_ring_pages = 1 << ring_page_order;
1122                 blkif->multi_ref = true;
1123         } else {
1124                 err = -EINVAL;
1125                 xenbus_dev_fatal(dev, err,
1126                                  "requested ring page order %d exceed max:%d",
1127                                  ring_page_order,
1128                                  xen_blkif_max_ring_order);
1129                 return err;
1130         }
1131
1132         if (blkif->nr_rings == 1)
1133                 return read_per_ring_refs(&blkif->rings[0], dev->otherend);
1134         else {
1135                 xspathsize = strlen(dev->otherend) + xenstore_path_ext_size;
1136                 xspath = kmalloc(xspathsize, GFP_KERNEL);
1137                 if (!xspath) {
1138                         xenbus_dev_fatal(dev, -ENOMEM, "reading ring references");
1139                         return -ENOMEM;
1140                 }
1141
1142                 for (i = 0; i < blkif->nr_rings; i++) {
1143                         memset(xspath, 0, xspathsize);
1144                         snprintf(xspath, xspathsize, "%s/queue-%u", dev->otherend, i);
1145                         err = read_per_ring_refs(&blkif->rings[i], xspath);
1146                         if (err) {
1147                                 kfree(xspath);
1148                                 return err;
1149                         }
1150                 }
1151                 kfree(xspath);
1152         }
1153         return 0;
1154 }
1155
1156 static const struct xenbus_device_id xen_blkbk_ids[] = {
1157         { "vbd" },
1158         { "" }
1159 };
1160
1161 static struct xenbus_driver xen_blkbk_driver = {
1162         .ids  = xen_blkbk_ids,
1163         .probe = xen_blkbk_probe,
1164         .remove = xen_blkbk_remove,
1165         .otherend_changed = frontend_changed,
1166         .allow_rebind = true,
1167         .reclaim_memory = reclaim_memory,
1168 };
1169
1170 int xen_blkif_xenbus_init(void)
1171 {
1172         return xenbus_register_backend(&xen_blkbk_driver);
1173 }
1174
1175 void xen_blkif_xenbus_fini(void)
1176 {
1177         xenbus_unregister_driver(&xen_blkbk_driver);
1178 }