drivers/virtio/virtio_balloon.c

   1 /*
   2  * Virtio balloon implementation, inspired by Dor Laor and Marcelo
   3  * Tosatti's implementations.
   4  *
   5  *  Copyright 2008 Rusty Russell IBM Corporation
   6  *
   7  *  This program is free software; you can redistribute it and/or modify
   8  *  it under the terms of the GNU General Public License as published by
   9  *  the Free Software Foundation; either version 2 of the License, or
  10  *  (at your option) any later version.
  11  *
  12  *  This program is distributed in the hope that it will be useful,
  13  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  *  GNU General Public License for more details.
  16  *
  17  *  You should have received a copy of the GNU General Public License
  18  *  along with this program; if not, write to the Free Software
  19  *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  20  */
  21
  22 #include <linux/virtio.h>
  23 #include <linux/virtio_balloon.h>
  24 #include <linux/swap.h>
  25 #include <linux/workqueue.h>
  26 #include <linux/delay.h>
  27 #include <linux/slab.h>
  28 #include <linux/module.h>
  29 #include <linux/balloon_compaction.h>
  30 #include <linux/oom.h>
  31 #include <linux/wait.h>
  32 #include <linux/mm.h>
  33 #include <linux/mount.h>
  34
  35 /*
  36  * Balloon device works in 4K page units.  So each page is pointed to by
  37  * multiple balloon pages.  All memory counters in this driver are in balloon
  38  * page units.
  39  */
  40 #define VIRTIO_BALLOON_PAGES_PER_PAGE (unsigned)(PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT)
  41 #define VIRTIO_BALLOON_ARRAY_PFNS_MAX 256
  42 #define OOM_VBALLOON_DEFAULT_PAGES 256
  43 #define VIRTBALLOON_OOM_NOTIFY_PRIORITY 80
  44
  45 static int oom_pages = OOM_VBALLOON_DEFAULT_PAGES;
  46 module_param(oom_pages, int, S_IRUSR | S_IWUSR);
  47 MODULE_PARM_DESC(oom_pages, "pages to free on OOM");
  48
  49 #ifdef CONFIG_BALLOON_COMPACTION
  50 static struct vfsmount *balloon_mnt;
  51 #endif
  52
  53 struct virtio_balloon {
  54         struct virtio_device *vdev;
  55         struct virtqueue *inflate_vq, *deflate_vq, *stats_vq;
  56
  57         /* The balloon servicing is delegated to a freezable workqueue. */
  58         struct work_struct update_balloon_stats_work;
  59         struct work_struct update_balloon_size_work;
  60
  61         /* Prevent updating balloon when it is being canceled. */
  62         spinlock_t stop_update_lock;
  63         bool stop_update;
  64
  65         /* Waiting for host to ack the pages we released. */
  66         wait_queue_head_t acked;
  67
  68         /* Number of balloon pages we've told the Host we're not using. */
  69         unsigned int num_pages;
  70         /*
  71          * The pages we've told the Host we're not using are enqueued
  72          * at vb_dev_info->pages list.
  73          * Each page on this list adds VIRTIO_BALLOON_PAGES_PER_PAGE
  74          * to num_pages above.
  75          */
  76         struct balloon_dev_info vb_dev_info;
  77
  78         /* Synchronize access/update to this struct virtio_balloon elements */
  79         struct mutex balloon_lock;
  80
  81         /* The array of pfns we tell the Host about. */
  82         unsigned int num_pfns;
  83         __virtio32 pfns[VIRTIO_BALLOON_ARRAY_PFNS_MAX];
  84
  85         /* Memory statistics */
  86         struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
  87
  88         /* To register callback in oom notifier call chain */
  89         struct notifier_block nb;
  90 };
  91
  92 static struct virtio_device_id id_table[] = {
  93         { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
  94         { 0 },
  95 };
  96
  97 static u32 page_to_balloon_pfn(struct page *page)
  98 {
  99         unsigned long pfn = page_to_pfn(page);
 100
 101         BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT);
 102         /* Convert pfn from Linux page size to balloon page size. */
 103         return pfn * VIRTIO_BALLOON_PAGES_PER_PAGE;
 104 }
 105
 106 static struct page *balloon_pfn_to_page(u32 pfn)
 107 {
 108         BUG_ON(pfn % VIRTIO_BALLOON_PAGES_PER_PAGE);
 109         return pfn_to_page(pfn / VIRTIO_BALLOON_PAGES_PER_PAGE);
 110 }
 111
 112 static void balloon_ack(struct virtqueue *vq)
 113 {
 114         struct virtio_balloon *vb = vq->vdev->priv;
 115
 116         wake_up(&vb->acked);
 117 }
 118
 119 static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
 120 {
 121         struct scatterlist sg;
 122         unsigned int len;
 123
 124         sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
 125
 126         /* We should always be able to add one buffer to an empty queue. */
 127         virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
 128         virtqueue_kick(vq);
 129
 130         /* When host has read buffer, this completes via balloon_ack */
 131         wait_event(vb->acked, virtqueue_get_buf(vq, &len));
 132
 133 }
 134
 135 static void set_page_pfns(struct virtio_balloon *vb,
 136                           __virtio32 pfns[], struct page *page)
 137 {
 138         unsigned int i;
 139
 140         /* Set balloon pfns pointing at this page.
 141          * Note that the first pfn points at start of the page. */
 142         for (i = 0; i < VIRTIO_BALLOON_PAGES_PER_PAGE; i++)
 143                 pfns[i] = cpu_to_virtio32(vb->vdev,
 144                                           page_to_balloon_pfn(page) + i);
 145 }
 146
 147 static unsigned fill_balloon(struct virtio_balloon *vb, size_t num)
 148 {
 149         struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
 150         unsigned num_allocated_pages;
 151
 152         /* We can only do one array worth at a time. */
 153         num = min(num, ARRAY_SIZE(vb->pfns));
 154
 155         mutex_lock(&vb->balloon_lock);
 156         for (vb->num_pfns = 0; vb->num_pfns < num;
 157              vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
 158                 struct page *page = balloon_page_enqueue(vb_dev_info);
 159
 160                 if (!page) {
 161                         dev_info_ratelimited(&vb->vdev->dev,
 162                                              "Out of puff! Can't get %u pages\n",
 163                                              VIRTIO_BALLOON_PAGES_PER_PAGE);
 164                         /* Sleep for at least 1/5 of a second before retry. */
 165                         msleep(200);
 166                         break;
 167                 }
 168                 set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
 169                 vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
 170                 if (!virtio_has_feature(vb->vdev,
 171                                         VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
 172                         adjust_managed_page_count(page, -1);
 173         }
 174
 175         num_allocated_pages = vb->num_pfns;
 176         /* Did we get any? */
 177         if (vb->num_pfns != 0)
 178                 tell_host(vb, vb->inflate_vq);
 179         mutex_unlock(&vb->balloon_lock);
 180
 181         return num_allocated_pages;
 182 }
 183
 184 static void release_pages_balloon(struct virtio_balloon *vb)
 185 {
 186         unsigned int i;
 187         struct page *page;
 188
 189         /* Find pfns pointing at start of each page, get pages and free them. */
 190         for (i = 0; i < vb->num_pfns; i += VIRTIO_BALLOON_PAGES_PER_PAGE) {
 191                 page = balloon_pfn_to_page(virtio32_to_cpu(vb->vdev,
 192                                                            vb->pfns[i]));
 193                 if (!virtio_has_feature(vb->vdev,
 194                                         VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
 195                         adjust_managed_page_count(page, 1);
 196                 put_page(page); /* balloon reference */
 197         }
 198 }
 199
 200 static unsigned leak_balloon(struct virtio_balloon *vb, size_t num)
 201 {
 202         unsigned num_freed_pages;
 203         struct page *page;
 204         struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
 205
 206         /* We can only do one array worth at a time. */
 207         num = min(num, ARRAY_SIZE(vb->pfns));
 208
 209         mutex_lock(&vb->balloon_lock);
 210         /* We can't release more pages than taken */
 211         num = min(num, (size_t)vb->num_pages);
 212         for (vb->num_pfns = 0; vb->num_pfns < num;
 213              vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
 214                 page = balloon_page_dequeue(vb_dev_info);
 215                 if (!page)
 216                         break;
 217                 set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
 218                 vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
 219         }
 220
 221         num_freed_pages = vb->num_pfns;
 222         /*
 223          * Note that if
 224          * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
 225          * is true, we *have* to do it in this order
 226          */
 227         if (vb->num_pfns != 0)
 228                 tell_host(vb, vb->deflate_vq);
 229         release_pages_balloon(vb);
 230         mutex_unlock(&vb->balloon_lock);
 231         return num_freed_pages;
 232 }
 233
 234 static inline void update_stat(struct virtio_balloon *vb, int idx,
 235                                u16 tag, u64 val)
 236 {
 237         BUG_ON(idx >= VIRTIO_BALLOON_S_NR);
 238         vb->stats[idx].tag = cpu_to_virtio16(vb->vdev, tag);
 239         vb->stats[idx].val = cpu_to_virtio64(vb->vdev, val);
 240 }
 241
 242 #define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
 243
 244 static void update_balloon_stats(struct virtio_balloon *vb)
 245 {
 246         unsigned long events[NR_VM_EVENT_ITEMS];
 247         struct sysinfo i;
 248         int idx = 0;
 249         long available;
 250
 251         all_vm_events(events);
 252         si_meminfo(&i);
 253
 254         available = si_mem_available();
 255
 256         update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN,
 257                                 pages_to_bytes(events[PSWPIN]));
 258         update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT,
 259                                 pages_to_bytes(events[PSWPOUT]));
 260         update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]);
 261         update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]);
 262         update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE,
 263                                 pages_to_bytes(i.freeram));
 264         update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT,
 265                                 pages_to_bytes(i.totalram));
 266         update_stat(vb, idx++, VIRTIO_BALLOON_S_AVAIL,
 267                                 pages_to_bytes(available));
 268 }
 269
 270 /*
 271  * While most virtqueues communicate guest-initiated requests to the hypervisor,
 272  * the stats queue operates in reverse.  The driver initializes the virtqueue
 273  * with a single buffer.  From that point forward, all conversations consist of
 274  * a hypervisor request (a call to this function) which directs us to refill
 275  * the virtqueue with a fresh stats buffer.  Since stats collection can sleep,
 276  * we delegate the job to a freezable workqueue that will do the actual work via
 277  * stats_handle_request().
 278  */
 279 static void stats_request(struct virtqueue *vq)
 280 {
 281         struct virtio_balloon *vb = vq->vdev->priv;
 282
 283         spin_lock(&vb->stop_update_lock);
 284         if (!vb->stop_update)
 285                 queue_work(system_freezable_wq, &vb->update_balloon_stats_work);
 286         spin_unlock(&vb->stop_update_lock);
 287 }
 288
 289 static void stats_handle_request(struct virtio_balloon *vb)
 290 {
 291         struct virtqueue *vq;
 292         struct scatterlist sg;
 293         unsigned int len;
 294
 295         update_balloon_stats(vb);
 296
 297         vq = vb->stats_vq;
 298         if (!virtqueue_get_buf(vq, &len))
 299                 return;
 300         sg_init_one(&sg, vb->stats, sizeof(vb->stats));
 301         virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
 302         virtqueue_kick(vq);
 303 }
 304
 305 static void virtballoon_changed(struct virtio_device *vdev)
 306 {
 307         struct virtio_balloon *vb = vdev->priv;
 308         unsigned long flags;
 309
 310         spin_lock_irqsave(&vb->stop_update_lock, flags);
 311         if (!vb->stop_update)
 312                 queue_work(system_freezable_wq, &vb->update_balloon_size_work);
 313         spin_unlock_irqrestore(&vb->stop_update_lock, flags);
 314 }
 315
 316 static inline s64 towards_target(struct virtio_balloon *vb)
 317 {
 318         s64 target;
 319         u32 num_pages;
 320
 321         virtio_cread(vb->vdev, struct virtio_balloon_config, num_pages,
 322                      &num_pages);
 323
 324         /* Legacy balloon config space is LE, unlike all other devices. */
 325         if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))
 326                 num_pages = le32_to_cpu((__force __le32)num_pages);
 327
 328         target = num_pages;
 329         return target - vb->num_pages;
 330 }
 331
 332 static void update_balloon_size(struct virtio_balloon *vb)
 333 {
 334         u32 actual = vb->num_pages;
 335
 336         /* Legacy balloon config space is LE, unlike all other devices. */
 337         if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))
 338                 actual = (__force u32)cpu_to_le32(actual);
 339
 340         virtio_cwrite(vb->vdev, struct virtio_balloon_config, actual,
 341                       &actual);
 342 }
 343
 344 /*
 345  * virtballoon_oom_notify - release pages when system is under severe
 346  *                          memory pressure (called from out_of_memory())
 347  * @self : notifier block struct
 348  * @dummy: not used
 349  * @parm : returned - number of freed pages
 350  *
 351  * The balancing of memory by use of the virtio balloon should not cause
 352  * the termination of processes while there are pages in the balloon.
 353  * If virtio balloon manages to release some memory, it will make the
 354  * system return and retry the allocation that forced the OOM killer
 355  * to run.
 356  */
 357 static int virtballoon_oom_notify(struct notifier_block *self,
 358                                   unsigned long dummy, void *parm)
 359 {
 360         struct virtio_balloon *vb;
 361         unsigned long *freed;
 362         unsigned num_freed_pages;
 363
 364         vb = container_of(self, struct virtio_balloon, nb);
 365         if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
 366                 return NOTIFY_OK;
 367
 368         freed = parm;
 369         num_freed_pages = leak_balloon(vb, oom_pages);
 370         update_balloon_size(vb);
 371         *freed += num_freed_pages;
 372
 373         return NOTIFY_OK;
 374 }
 375
 376 static void update_balloon_stats_func(struct work_struct *work)
 377 {
 378         struct virtio_balloon *vb;
 379
 380         vb = container_of(work, struct virtio_balloon,
 381                           update_balloon_stats_work);
 382         stats_handle_request(vb);
 383 }
 384
 385 static void update_balloon_size_func(struct work_struct *work)
 386 {
 387         struct virtio_balloon *vb;
 388         s64 diff;
 389
 390         vb = container_of(work, struct virtio_balloon,
 391                           update_balloon_size_work);
 392         diff = towards_target(vb);
 393
 394         if (diff > 0)
 395                 diff -= fill_balloon(vb, diff);
 396         else if (diff < 0)
 397                 diff += leak_balloon(vb, -diff);
 398         update_balloon_size(vb);
 399
 400         if (diff)
 401                 queue_work(system_freezable_wq, work);
 402 }
 403
 404 static int init_vqs(struct virtio_balloon *vb)
 405 {
 406         struct virtqueue *vqs[3];
 407         vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request };
 408         static const char * const names[] = { "inflate", "deflate", "stats" };
 409         int err, nvqs;
 410
 411         /*
 412          * We expect two virtqueues: inflate and deflate, and
 413          * optionally stat.
 414          */
 415         nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2;
 416         err = vb->vdev->config->find_vqs(vb->vdev, nvqs, vqs, callbacks, names);
 417         if (err)
 418                 return err;
 419
 420         vb->inflate_vq = vqs[0];
 421         vb->deflate_vq = vqs[1];
 422         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
 423                 struct scatterlist sg;
 424                 vb->stats_vq = vqs[2];
 425
 426                 /*
 427                  * Prime this virtqueue with one buffer so the hypervisor can
 428                  * use it to signal us later (it can't be broken yet!).
 429                  */
 430                 sg_init_one(&sg, vb->stats, sizeof vb->stats);
 431                 if (virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb, GFP_KERNEL)
 432                     < 0)
 433                         BUG();
 434                 virtqueue_kick(vb->stats_vq);
 435         }
 436         return 0;
 437 }
 438
 439 #ifdef CONFIG_BALLOON_COMPACTION
 440 /*
 441  * virtballoon_migratepage - perform the balloon page migration on behalf of
 442  *                           a compation thread.     (called under page lock)
 443  * @vb_dev_info: the balloon device
 444  * @newpage: page that will replace the isolated page after migration finishes.
 445  * @page   : the isolated (old) page that is about to be migrated to newpage.
 446  * @mode   : compaction mode -- not used for balloon page migration.
 447  *
 448  * After a ballooned page gets isolated by compaction procedures, this is the
 449  * function that performs the page migration on behalf of a compaction thread
 450  * The page migration for virtio balloon is done in a simple swap fashion which
 451  * follows these two macro steps:
 452  *  1) insert newpage into vb->pages list and update the host about it;
 453  *  2) update the host about the old page removed from vb->pages list;
 454  *
 455  * This function preforms the balloon page migration task.
 456  * Called through balloon_mapping->a_ops->migratepage
 457  */
 458 static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
 459                 struct page *newpage, struct page *page, enum migrate_mode mode)
 460 {
 461         struct virtio_balloon *vb = container_of(vb_dev_info,
 462                         struct virtio_balloon, vb_dev_info);
 463         unsigned long flags;
 464
 465         /*
 466          * In order to avoid lock contention while migrating pages concurrently
 467          * to leak_balloon() or fill_balloon() we just give up the balloon_lock
 468          * this turn, as it is easier to retry the page migration later.
 469          * This also prevents fill_balloon() getting stuck into a mutex
 470          * recursion in the case it ends up triggering memory compaction
 471          * while it is attempting to inflate the ballon.
 472          */
 473         if (!mutex_trylock(&vb->balloon_lock))
 474                 return -EAGAIN;
 475
 476         get_page(newpage); /* balloon reference */
 477
 478         /* balloon's page migration 1st step  -- inflate "newpage" */
 479         spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
 480         balloon_page_insert(vb_dev_info, newpage);
 481         vb_dev_info->isolated_pages--;
 482         __count_vm_event(BALLOON_MIGRATE);
 483         spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
 484         vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
 485         set_page_pfns(vb, vb->pfns, newpage);
 486         tell_host(vb, vb->inflate_vq);
 487
 488         /* balloon's page migration 2nd step -- deflate "page" */
 489         balloon_page_delete(page);
 490         vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
 491         set_page_pfns(vb, vb->pfns, page);
 492         tell_host(vb, vb->deflate_vq);
 493
 494         mutex_unlock(&vb->balloon_lock);
 495
 496         put_page(page); /* balloon reference */
 497
 498         return MIGRATEPAGE_SUCCESS;
 499 }
 500
 501 static struct dentry *balloon_mount(struct file_system_type *fs_type,
 502                 int flags, const char *dev_name, void *data)
 503 {
 504         static const struct dentry_operations ops = {
 505                 .d_dname = simple_dname,
 506         };
 507
 508         return mount_pseudo(fs_type, "balloon-kvm:", NULL, &ops,
 509                                 BALLOON_KVM_MAGIC);
 510 }
 511
 512 static struct file_system_type balloon_fs = {
 513         .name           = "balloon-kvm",
 514         .mount          = balloon_mount,
 515         .kill_sb        = kill_anon_super,
 516 };
 517
 518 #endif /* CONFIG_BALLOON_COMPACTION */
 519
 520 static int virtballoon_probe(struct virtio_device *vdev)
 521 {
 522         struct virtio_balloon *vb;
 523         int err;
 524
 525         if (!vdev->config->get) {
 526                 dev_err(&vdev->dev, "%s failure: config access disabled\n",
 527                         __func__);
 528                 return -EINVAL;
 529         }
 530
 531         vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL);
 532         if (!vb) {
 533                 err = -ENOMEM;
 534                 goto out;
 535         }
 536
 537         INIT_WORK(&vb->update_balloon_stats_work, update_balloon_stats_func);
 538         INIT_WORK(&vb->update_balloon_size_work, update_balloon_size_func);
 539         spin_lock_init(&vb->stop_update_lock);
 540         vb->stop_update = false;
 541         vb->num_pages = 0;
 542         mutex_init(&vb->balloon_lock);
 543         init_waitqueue_head(&vb->acked);
 544         vb->vdev = vdev;
 545
 546         balloon_devinfo_init(&vb->vb_dev_info);
 547
 548         err = init_vqs(vb);
 549         if (err)
 550                 goto out_free_vb;
 551
 552         vb->nb.notifier_call = virtballoon_oom_notify;
 553         vb->nb.priority = VIRTBALLOON_OOM_NOTIFY_PRIORITY;
 554         err = register_oom_notifier(&vb->nb);
 555         if (err < 0)
 556                 goto out_del_vqs;
 557
 558 #ifdef CONFIG_BALLOON_COMPACTION
 559         balloon_mnt = kern_mount(&balloon_fs);
 560         if (IS_ERR(balloon_mnt)) {
 561                 err = PTR_ERR(balloon_mnt);
 562                 unregister_oom_notifier(&vb->nb);
 563                 goto out_del_vqs;
 564         }
 565
 566         vb->vb_dev_info.migratepage = virtballoon_migratepage;
 567         vb->vb_dev_info.inode = alloc_anon_inode(balloon_mnt->mnt_sb);
 568         if (IS_ERR(vb->vb_dev_info.inode)) {
 569                 err = PTR_ERR(vb->vb_dev_info.inode);
 570                 kern_unmount(balloon_mnt);
 571                 unregister_oom_notifier(&vb->nb);
 572                 vb->vb_dev_info.inode = NULL;
 573                 goto out_del_vqs;
 574         }
 575         vb->vb_dev_info.inode->i_mapping->a_ops = &balloon_aops;
 576 #endif
 577
 578         virtio_device_ready(vdev);
 579
 580         if (towards_target(vb))
 581                 virtballoon_changed(vdev);
 582         return 0;
 583
 584 out_del_vqs:
 585         vdev->config->del_vqs(vdev);
 586 out_free_vb:
 587         kfree(vb);
 588 out:
 589         return err;
 590 }
 591
 592 static void remove_common(struct virtio_balloon *vb)
 593 {
 594         /* There might be pages left in the balloon: free them. */
 595         while (vb->num_pages)
 596                 leak_balloon(vb, vb->num_pages);
 597         update_balloon_size(vb);
 598
 599         /* Now we reset the device so we can clean up the queues. */
 600         vb->vdev->config->reset(vb->vdev);
 601
 602         vb->vdev->config->del_vqs(vb->vdev);
 603 }
 604
 605 static void virtballoon_remove(struct virtio_device *vdev)
 606 {
 607         struct virtio_balloon *vb = vdev->priv;
 608
 609         unregister_oom_notifier(&vb->nb);
 610
 611         spin_lock_irq(&vb->stop_update_lock);
 612         vb->stop_update = true;
 613         spin_unlock_irq(&vb->stop_update_lock);
 614         cancel_work_sync(&vb->update_balloon_size_work);
 615         cancel_work_sync(&vb->update_balloon_stats_work);
 616
 617         remove_common(vb);
 618         if (vb->vb_dev_info.inode)
 619                 iput(vb->vb_dev_info.inode);
 620         kfree(vb);
 621 }
 622
 623 #ifdef CONFIG_PM_SLEEP
 624 static int virtballoon_freeze(struct virtio_device *vdev)
 625 {
 626         struct virtio_balloon *vb = vdev->priv;
 627
 628         /*
 629          * The workqueue is already frozen by the PM core before this
 630          * function is called.
 631          */
 632         remove_common(vb);
 633         return 0;
 634 }
 635
 636 static int virtballoon_restore(struct virtio_device *vdev)
 637 {
 638         struct virtio_balloon *vb = vdev->priv;
 639         int ret;
 640
 641         ret = init_vqs(vdev->priv);
 642         if (ret)
 643                 return ret;
 644
 645         virtio_device_ready(vdev);
 646
 647         if (towards_target(vb))
 648                 virtballoon_changed(vdev);
 649         update_balloon_size(vb);
 650         return 0;
 651 }
 652 #endif
 653
 654 static unsigned int features[] = {
 655         VIRTIO_BALLOON_F_MUST_TELL_HOST,
 656         VIRTIO_BALLOON_F_STATS_VQ,
 657         VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
 658 };
 659
 660 static struct virtio_driver virtio_balloon_driver = {
 661         .feature_table = features,
 662         .feature_table_size = ARRAY_SIZE(features),
 663         .driver.name =  KBUILD_MODNAME,
 664         .driver.owner = THIS_MODULE,
 665         .id_table =     id_table,
 666         .probe =        virtballoon_probe,
 667         .remove =       virtballoon_remove,
 668         .config_changed = virtballoon_changed,
 669 #ifdef CONFIG_PM_SLEEP
 670         .freeze =       virtballoon_freeze,
 671         .restore =      virtballoon_restore,
 672 #endif
 673 };
 674
 675 module_virtio_driver(virtio_balloon_driver);
 676 MODULE_DEVICE_TABLE(virtio, id_table);
 677 MODULE_DESCRIPTION("Virtio balloon driver");
 678 MODULE_LICENSE("GPL");