drivers/gpu/drm/drm_gem.c

   1 /*
   2  * Copyright © 2008 Intel Corporation
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining a
   5  * copy of this software and associated documentation files (the "Software"),
   6  * to deal in the Software without restriction, including without limitation
   7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   8  * and/or sell copies of the Software, and to permit persons to whom the
   9  * Software is furnished to do so, subject to the following conditions:
  10  *
  11  * The above copyright notice and this permission notice (including the next
  12  * paragraph) shall be included in all copies or substantial portions of the
  13  * Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  18  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  20  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  21  * IN THE SOFTWARE.
  22  *
  23  * Authors:
  24  *    Eric Anholt <eric@anholt.net>
  25  *
  26  */
  27
  28 #include <linux/types.h>
  29 #include <linux/slab.h>
  30 #include <linux/mm.h>
  31 #include <linux/uaccess.h>
  32 #include <linux/fs.h>
  33 #include <linux/file.h>
  34 #include <linux/module.h>
  35 #include <linux/mman.h>
  36 #include <linux/pagemap.h>
  37 #include <linux/shmem_fs.h>
  38 #include <linux/dma-buf.h>
  39 #include <drm/drmP.h>
  40 #include <drm/drm_vma_manager.h>
  41
  42 /** @file drm_gem.c
  43  *
  44  * This file provides some of the base ioctls and library routines for
  45  * the graphics memory manager implemented by each device driver.
  46  *
  47  * Because various devices have different requirements in terms of
  48  * synchronization and migration strategies, implementing that is left up to
  49  * the driver, and all that the general API provides should be generic --
  50  * allocating objects, reading/writing data with the cpu, freeing objects.
  51  * Even there, platform-dependent optimizations for reading/writing data with
  52  * the CPU mean we'll likely hook those out to driver-specific calls.  However,
  53  * the DRI2 implementation wants to have at least allocate/mmap be generic.
  54  *
  55  * The goal was to have swap-backed object allocation managed through
  56  * struct file.  However, file descriptors as handles to a struct file have
  57  * two major failings:
  58  * - Process limits prevent more than 1024 or so being used at a time by
  59  *   default.
  60  * - Inability to allocate high fds will aggravate the X Server's select()
  61  *   handling, and likely that of many GL client applications as well.
  62  *
  63  * This led to a plan of using our own integer IDs (called handles, following
  64  * DRM terminology) to mimic fds, and implement the fd syscalls we need as
  65  * ioctls.  The objects themselves will still include the struct file so
  66  * that we can transition to fds if the required kernel infrastructure shows
  67  * up at a later date, and as our interface with shmfs for memory allocation.
  68  */
  69
  70 /*
  71  * We make up offsets for buffer objects so we can recognize them at
  72  * mmap time.
  73  */
  74
  75 /* pgoff in mmap is an unsigned long, so we need to make sure that
  76  * the faked up offset will fit
  77  */
  78
  79 #if BITS_PER_LONG == 64
  80 #define DRM_FILE_PAGE_OFFSET_START ((0xFFFFFFFFUL >> PAGE_SHIFT) + 1)
  81 #define DRM_FILE_PAGE_OFFSET_SIZE ((0xFFFFFFFFUL >> PAGE_SHIFT) * 16)
  82 #else
  83 #define DRM_FILE_PAGE_OFFSET_START ((0xFFFFFFFUL >> PAGE_SHIFT) + 1)
  84 #define DRM_FILE_PAGE_OFFSET_SIZE ((0xFFFFFFFUL >> PAGE_SHIFT) * 16)
  85 #endif
  86
  87 /**
  88  * Initialize the GEM device fields
  89  */
  90
  91 int
  92 drm_gem_init(struct drm_device *dev)
  93 {
  94         struct drm_gem_mm *mm;
  95
  96         spin_lock_init(&dev->object_name_lock);
  97         idr_init(&dev->object_name_idr);
  98
  99         mm = kzalloc(sizeof(struct drm_gem_mm), GFP_KERNEL);
 100         if (!mm) {
 101                 DRM_ERROR("out of memory\n");
 102                 return -ENOMEM;
 103         }
 104
 105         dev->mm_private = mm;
 106         drm_vma_offset_manager_init(&mm->vma_manager,
 107                                     DRM_FILE_PAGE_OFFSET_START,
 108                                     DRM_FILE_PAGE_OFFSET_SIZE);
 109
 110         return 0;
 111 }
 112
 113 void
 114 drm_gem_destroy(struct drm_device *dev)
 115 {
 116         struct drm_gem_mm *mm = dev->mm_private;
 117
 118         drm_vma_offset_manager_destroy(&mm->vma_manager);
 119         kfree(mm);
 120         dev->mm_private = NULL;
 121 }
 122
 123 /**
 124  * Initialize an already allocated GEM object of the specified size with
 125  * shmfs backing store.
 126  */
 127 int drm_gem_object_init(struct drm_device *dev,
 128                         struct drm_gem_object *obj, size_t size)
 129 {
 130         struct file *filp;
 131
 132         filp = shmem_file_setup("drm mm object", size, VM_NORESERVE);
 133         if (IS_ERR(filp))
 134                 return PTR_ERR(filp);
 135
 136         drm_gem_private_object_init(dev, obj, size);
 137         obj->filp = filp;
 138
 139         return 0;
 140 }
 141 EXPORT_SYMBOL(drm_gem_object_init);
 142
 143 /**
 144  * Initialize an already allocated GEM object of the specified size with
 145  * no GEM provided backing store. Instead the caller is responsible for
 146  * backing the object and handling it.
 147  */
 148 void drm_gem_private_object_init(struct drm_device *dev,
 149                                  struct drm_gem_object *obj, size_t size)
 150 {
 151         BUG_ON((size & (PAGE_SIZE - 1)) != 0);
 152
 153         obj->dev = dev;
 154         obj->filp = NULL;
 155
 156         kref_init(&obj->refcount);
 157         atomic_set(&obj->handle_count, 0);
 158         obj->size = size;
 159 }
 160 EXPORT_SYMBOL(drm_gem_private_object_init);
 161
 162 /**
 163  * Allocate a GEM object of the specified size with shmfs backing store
 164  */
 165 struct drm_gem_object *
 166 drm_gem_object_alloc(struct drm_device *dev, size_t size)
 167 {
 168         struct drm_gem_object *obj;
 169
 170         obj = kzalloc(sizeof(*obj), GFP_KERNEL);
 171         if (!obj)
 172                 goto free;
 173
 174         if (drm_gem_object_init(dev, obj, size) != 0)
 175                 goto free;
 176
 177         if (dev->driver->gem_init_object != NULL &&
 178             dev->driver->gem_init_object(obj) != 0) {
 179                 goto fput;
 180         }
 181         return obj;
 182 fput:
 183         /* Object_init mangles the global counters - readjust them. */
 184         fput(obj->filp);
 185 free:
 186         kfree(obj);
 187         return NULL;
 188 }
 189 EXPORT_SYMBOL(drm_gem_object_alloc);
 190
 191 static void
 192 drm_gem_remove_prime_handles(struct drm_gem_object *obj, struct drm_file *filp)
 193 {
 194         if (obj->import_attach) {
 195                 drm_prime_remove_buf_handle(&filp->prime,
 196                                 obj->import_attach->dmabuf);
 197         }
 198         if (obj->export_dma_buf) {
 199                 drm_prime_remove_buf_handle(&filp->prime,
 200                                 obj->export_dma_buf);
 201         }
 202 }
 203
 204 /**
 205  * Removes the mapping from handle to filp for this object.
 206  */
 207 int
 208 drm_gem_handle_delete(struct drm_file *filp, u32 handle)
 209 {
 210         struct drm_device *dev;
 211         struct drm_gem_object *obj;
 212
 213         /* This is gross. The idr system doesn't let us try a delete and
 214          * return an error code.  It just spews if you fail at deleting.
 215          * So, we have to grab a lock around finding the object and then
 216          * doing the delete on it and dropping the refcount, or the user
 217          * could race us to double-decrement the refcount and cause a
 218          * use-after-free later.  Given the frequency of our handle lookups,
 219          * we may want to use ida for number allocation and a hash table
 220          * for the pointers, anyway.
 221          */
 222         spin_lock(&filp->table_lock);
 223
 224         /* Check if we currently have a reference on the object */
 225         obj = idr_find(&filp->object_idr, handle);
 226         if (obj == NULL) {
 227                 spin_unlock(&filp->table_lock);
 228                 return -EINVAL;
 229         }
 230         dev = obj->dev;
 231
 232         /* Release reference and decrement refcount. */
 233         idr_remove(&filp->object_idr, handle);
 234         spin_unlock(&filp->table_lock);
 235
 236         drm_gem_remove_prime_handles(obj, filp);
 237
 238         if (dev->driver->gem_close_object)
 239                 dev->driver->gem_close_object(obj, filp);
 240         drm_gem_object_handle_unreference_unlocked(obj);
 241
 242         return 0;
 243 }
 244 EXPORT_SYMBOL(drm_gem_handle_delete);
 245
 246 /**
 247  * drm_gem_dumb_destroy - dumb fb callback helper for gem based drivers
 248  *
 249  * This implements the ->dumb_destroy kms driver callback for drivers which use
 250  * gem to manage their backing storage.
 251  */
 252 int drm_gem_dumb_destroy(struct drm_file *file,
 253                          struct drm_device *dev,
 254                          uint32_t handle)
 255 {
 256         return drm_gem_handle_delete(file, handle);
 257 }
 258 EXPORT_SYMBOL(drm_gem_dumb_destroy);
 259
 260 /**
 261  * Create a handle for this object. This adds a handle reference
 262  * to the object, which includes a regular reference count. Callers
 263  * will likely want to dereference the object afterwards.
 264  */
 265 int
 266 drm_gem_handle_create(struct drm_file *file_priv,
 267                        struct drm_gem_object *obj,
 268                        u32 *handlep)
 269 {
 270         struct drm_device *dev = obj->dev;
 271         int ret;
 272
 273         /*
 274          * Get the user-visible handle using idr.  Preload and perform
 275          * allocation under our spinlock.
 276          */
 277         idr_preload(GFP_KERNEL);
 278         spin_lock(&file_priv->table_lock);
 279
 280         ret = idr_alloc(&file_priv->object_idr, obj, 1, 0, GFP_NOWAIT);
 281
 282         spin_unlock(&file_priv->table_lock);
 283         idr_preload_end();
 284         if (ret < 0)
 285                 return ret;
 286         *handlep = ret;
 287
 288         drm_gem_object_handle_reference(obj);
 289
 290         if (dev->driver->gem_open_object) {
 291                 ret = dev->driver->gem_open_object(obj, file_priv);
 292                 if (ret) {
 293                         drm_gem_handle_delete(file_priv, *handlep);
 294                         return ret;
 295                 }
 296         }
 297
 298         return 0;
 299 }
 300 EXPORT_SYMBOL(drm_gem_handle_create);
 301
 302
 303 /**
 304  * drm_gem_free_mmap_offset - release a fake mmap offset for an object
 305  * @obj: obj in question
 306  *
 307  * This routine frees fake offsets allocated by drm_gem_create_mmap_offset().
 308  */
 309 void
 310 drm_gem_free_mmap_offset(struct drm_gem_object *obj)
 311 {
 312         struct drm_device *dev = obj->dev;
 313         struct drm_gem_mm *mm = dev->mm_private;
 314
 315         drm_vma_offset_remove(&mm->vma_manager, &obj->vma_node);
 316 }
 317 EXPORT_SYMBOL(drm_gem_free_mmap_offset);
 318
 319 /**
 320  * drm_gem_create_mmap_offset - create a fake mmap offset for an object
 321  * @obj: obj in question
 322  *
 323  * GEM memory mapping works by handing back to userspace a fake mmap offset
 324  * it can use in a subsequent mmap(2) call.  The DRM core code then looks
 325  * up the object based on the offset and sets up the various memory mapping
 326  * structures.
 327  *
 328  * This routine allocates and attaches a fake offset for @obj.
 329  */
 330 int
 331 drm_gem_create_mmap_offset(struct drm_gem_object *obj)
 332 {
 333         struct drm_device *dev = obj->dev;
 334         struct drm_gem_mm *mm = dev->mm_private;
 335
 336         return drm_vma_offset_add(&mm->vma_manager, &obj->vma_node,
 337                                   obj->size / PAGE_SIZE);
 338 }
 339 EXPORT_SYMBOL(drm_gem_create_mmap_offset);
 340
 341 /** Returns a reference to the object named by the handle. */
 342 struct drm_gem_object *
 343 drm_gem_object_lookup(struct drm_device *dev, struct drm_file *filp,
 344                       u32 handle)
 345 {
 346         struct drm_gem_object *obj;
 347
 348         spin_lock(&filp->table_lock);
 349
 350         /* Check if we currently have a reference on the object */
 351         obj = idr_find(&filp->object_idr, handle);
 352         if (obj == NULL) {
 353                 spin_unlock(&filp->table_lock);
 354                 return NULL;
 355         }
 356
 357         drm_gem_object_reference(obj);
 358
 359         spin_unlock(&filp->table_lock);
 360
 361         return obj;
 362 }
 363 EXPORT_SYMBOL(drm_gem_object_lookup);
 364
 365 /**
 366  * Releases the handle to an mm object.
 367  */
 368 int
 369 drm_gem_close_ioctl(struct drm_device *dev, void *data,
 370                     struct drm_file *file_priv)
 371 {
 372         struct drm_gem_close *args = data;
 373         int ret;
 374
 375         if (!(dev->driver->driver_features & DRIVER_GEM))
 376                 return -ENODEV;
 377
 378         ret = drm_gem_handle_delete(file_priv, args->handle);
 379
 380         return ret;
 381 }
 382
 383 /**
 384  * Create a global name for an object, returning the name.
 385  *
 386  * Note that the name does not hold a reference; when the object
 387  * is freed, the name goes away.
 388  */
 389 int
 390 drm_gem_flink_ioctl(struct drm_device *dev, void *data,
 391                     struct drm_file *file_priv)
 392 {
 393         struct drm_gem_flink *args = data;
 394         struct drm_gem_object *obj;
 395         int ret;
 396
 397         if (!(dev->driver->driver_features & DRIVER_GEM))
 398                 return -ENODEV;
 399
 400         obj = drm_gem_object_lookup(dev, file_priv, args->handle);
 401         if (obj == NULL)
 402                 return -ENOENT;
 403
 404         idr_preload(GFP_KERNEL);
 405         spin_lock(&dev->object_name_lock);
 406         if (!obj->name) {
 407                 ret = idr_alloc(&dev->object_name_idr, obj, 1, 0, GFP_NOWAIT);
 408                 if (ret < 0)
 409                         goto err;
 410
 411                 obj->name = ret;
 412
 413                 /* Allocate a reference for the name table.  */
 414                 drm_gem_object_reference(obj);
 415         }
 416
 417         args->name = (uint64_t) obj->name;
 418         ret = 0;
 419
 420 err:
 421         spin_unlock(&dev->object_name_lock);
 422         idr_preload_end();
 423         drm_gem_object_unreference_unlocked(obj);
 424         return ret;
 425 }
 426
 427 /**
 428  * Open an object using the global name, returning a handle and the size.
 429  *
 430  * This handle (of course) holds a reference to the object, so the object
 431  * will not go away until the handle is deleted.
 432  */
 433 int
 434 drm_gem_open_ioctl(struct drm_device *dev, void *data,
 435                    struct drm_file *file_priv)
 436 {
 437         struct drm_gem_open *args = data;
 438         struct drm_gem_object *obj;
 439         int ret;
 440         u32 handle;
 441
 442         if (!(dev->driver->driver_features & DRIVER_GEM))
 443                 return -ENODEV;
 444
 445         spin_lock(&dev->object_name_lock);
 446         obj = idr_find(&dev->object_name_idr, (int) args->name);
 447         if (obj)
 448                 drm_gem_object_reference(obj);
 449         spin_unlock(&dev->object_name_lock);
 450         if (!obj)
 451                 return -ENOENT;
 452
 453         ret = drm_gem_handle_create(file_priv, obj, &handle);
 454         drm_gem_object_unreference_unlocked(obj);
 455         if (ret)
 456                 return ret;
 457
 458         args->handle = handle;
 459         args->size = obj->size;
 460
 461         return 0;
 462 }
 463
 464 /**
 465  * Called at device open time, sets up the structure for handling refcounting
 466  * of mm objects.
 467  */
 468 void
 469 drm_gem_open(struct drm_device *dev, struct drm_file *file_private)
 470 {
 471         idr_init(&file_private->object_idr);
 472         spin_lock_init(&file_private->table_lock);
 473 }
 474
 475 /**
 476  * Called at device close to release the file's
 477  * handle references on objects.
 478  */
 479 static int
 480 drm_gem_object_release_handle(int id, void *ptr, void *data)
 481 {
 482         struct drm_file *file_priv = data;
 483         struct drm_gem_object *obj = ptr;
 484         struct drm_device *dev = obj->dev;
 485
 486         drm_gem_remove_prime_handles(obj, file_priv);
 487
 488         if (dev->driver->gem_close_object)
 489                 dev->driver->gem_close_object(obj, file_priv);
 490
 491         drm_gem_object_handle_unreference_unlocked(obj);
 492
 493         return 0;
 494 }
 495
 496 /**
 497  * Called at close time when the filp is going away.
 498  *
 499  * Releases any remaining references on objects by this filp.
 500  */
 501 void
 502 drm_gem_release(struct drm_device *dev, struct drm_file *file_private)
 503 {
 504         idr_for_each(&file_private->object_idr,
 505                      &drm_gem_object_release_handle, file_private);
 506         idr_destroy(&file_private->object_idr);
 507 }
 508
 509 void
 510 drm_gem_object_release(struct drm_gem_object *obj)
 511 {
 512         if (obj->filp)
 513             fput(obj->filp);
 514 }
 515 EXPORT_SYMBOL(drm_gem_object_release);
 516
 517 /**
 518  * Called after the last reference to the object has been lost.
 519  * Must be called holding struct_ mutex
 520  *
 521  * Frees the object
 522  */
 523 void
 524 drm_gem_object_free(struct kref *kref)
 525 {
 526         struct drm_gem_object *obj = (struct drm_gem_object *) kref;
 527         struct drm_device *dev = obj->dev;
 528
 529         BUG_ON(!mutex_is_locked(&dev->struct_mutex));
 530
 531         if (dev->driver->gem_free_object != NULL)
 532                 dev->driver->gem_free_object(obj);
 533 }
 534 EXPORT_SYMBOL(drm_gem_object_free);
 535
 536 static void drm_gem_object_ref_bug(struct kref *list_kref)
 537 {
 538         BUG();
 539 }
 540
 541 /**
 542  * Called after the last handle to the object has been closed
 543  *
 544  * Removes any name for the object. Note that this must be
 545  * called before drm_gem_object_free or we'll be touching
 546  * freed memory
 547  */
 548 void drm_gem_object_handle_free(struct drm_gem_object *obj)
 549 {
 550         struct drm_device *dev = obj->dev;
 551
 552         /* Remove any name for this object */
 553         spin_lock(&dev->object_name_lock);
 554         if (obj->name) {
 555                 idr_remove(&dev->object_name_idr, obj->name);
 556                 obj->name = 0;
 557                 spin_unlock(&dev->object_name_lock);
 558                 /*
 559                  * The object name held a reference to this object, drop
 560                  * that now.
 561                 *
 562                 * This cannot be the last reference, since the handle holds one too.
 563                  */
 564                 kref_put(&obj->refcount, drm_gem_object_ref_bug);
 565         } else
 566                 spin_unlock(&dev->object_name_lock);
 567
 568 }
 569 EXPORT_SYMBOL(drm_gem_object_handle_free);
 570
 571 void drm_gem_vm_open(struct vm_area_struct *vma)
 572 {
 573         struct drm_gem_object *obj = vma->vm_private_data;
 574
 575         drm_gem_object_reference(obj);
 576
 577         mutex_lock(&obj->dev->struct_mutex);
 578         drm_vm_open_locked(obj->dev, vma);
 579         mutex_unlock(&obj->dev->struct_mutex);
 580 }
 581 EXPORT_SYMBOL(drm_gem_vm_open);
 582
 583 void drm_gem_vm_close(struct vm_area_struct *vma)
 584 {
 585         struct drm_gem_object *obj = vma->vm_private_data;
 586         struct drm_device *dev = obj->dev;
 587
 588         mutex_lock(&dev->struct_mutex);
 589         drm_vm_close_locked(obj->dev, vma);
 590         drm_gem_object_unreference(obj);
 591         mutex_unlock(&dev->struct_mutex);
 592 }
 593 EXPORT_SYMBOL(drm_gem_vm_close);
 594
 595 /**
 596  * drm_gem_mmap_obj - memory map a GEM object
 597  * @obj: the GEM object to map
 598  * @obj_size: the object size to be mapped, in bytes
 599  * @vma: VMA for the area to be mapped
 600  *
 601  * Set up the VMA to prepare mapping of the GEM object using the gem_vm_ops
 602  * provided by the driver. Depending on their requirements, drivers can either
 603  * provide a fault handler in their gem_vm_ops (in which case any accesses to
 604  * the object will be trapped, to perform migration, GTT binding, surface
 605  * register allocation, or performance monitoring), or mmap the buffer memory
 606  * synchronously after calling drm_gem_mmap_obj.
 607  *
 608  * This function is mainly intended to implement the DMABUF mmap operation, when
 609  * the GEM object is not looked up based on its fake offset. To implement the
 610  * DRM mmap operation, drivers should use the drm_gem_mmap() function.
 611  *
 612  * NOTE: This function has to be protected with dev->struct_mutex
 613  *
 614  * Return 0 or success or -EINVAL if the object size is smaller than the VMA
 615  * size, or if no gem_vm_ops are provided.
 616  */
 617 int drm_gem_mmap_obj(struct drm_gem_object *obj, unsigned long obj_size,
 618                      struct vm_area_struct *vma)
 619 {
 620         struct drm_device *dev = obj->dev;
 621
 622         lockdep_assert_held(&dev->struct_mutex);
 623
 624         /* Check for valid size. */
 625         if (obj_size < vma->vm_end - vma->vm_start)
 626                 return -EINVAL;
 627
 628         if (!dev->driver->gem_vm_ops)
 629                 return -EINVAL;
 630
 631         vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP;
 632         vma->vm_ops = dev->driver->gem_vm_ops;
 633         vma->vm_private_data = obj;
 634         vma->vm_page_prot =  pgprot_writecombine(vm_get_page_prot(vma->vm_flags));
 635
 636         /* Take a ref for this mapping of the object, so that the fault
 637          * handler can dereference the mmap offset's pointer to the object.
 638          * This reference is cleaned up by the corresponding vm_close
 639          * (which should happen whether the vma was created by this call, or
 640          * by a vm_open due to mremap or partial unmap or whatever).
 641          */
 642         drm_gem_object_reference(obj);
 643
 644         drm_vm_open_locked(dev, vma);
 645         return 0;
 646 }
 647 EXPORT_SYMBOL(drm_gem_mmap_obj);
 648
 649 /**
 650  * drm_gem_mmap - memory map routine for GEM objects
 651  * @filp: DRM file pointer
 652  * @vma: VMA for the area to be mapped
 653  *
 654  * If a driver supports GEM object mapping, mmap calls on the DRM file
 655  * descriptor will end up here.
 656  *
 657  * Look up the GEM object based on the offset passed in (vma->vm_pgoff will
 658  * contain the fake offset we created when the GTT map ioctl was called on
 659  * the object) and map it with a call to drm_gem_mmap_obj().
 660  */
 661 int drm_gem_mmap(struct file *filp, struct vm_area_struct *vma)
 662 {
 663         struct drm_file *priv = filp->private_data;
 664         struct drm_device *dev = priv->minor->dev;
 665         struct drm_gem_mm *mm = dev->mm_private;
 666         struct drm_gem_object *obj;
 667         struct drm_vma_offset_node *node;
 668         int ret = 0;
 669
 670         if (drm_device_is_unplugged(dev))
 671                 return -ENODEV;
 672
 673         mutex_lock(&dev->struct_mutex);
 674
 675         node = drm_vma_offset_exact_lookup(&mm->vma_manager, vma->vm_pgoff,
 676                                            vma_pages(vma));
 677         if (!node) {
 678                 mutex_unlock(&dev->struct_mutex);
 679                 return drm_mmap(filp, vma);
 680         }
 681
 682         obj = container_of(node, struct drm_gem_object, vma_node);
 683         ret = drm_gem_mmap_obj(obj, drm_vma_node_size(node) << PAGE_SHIFT, vma);
 684
 685         mutex_unlock(&dev->struct_mutex);
 686
 687         return ret;
 688 }
 689 EXPORT_SYMBOL(drm_gem_mmap);