| 1 | // SPDX-License-Identifier: GPL-2.0-only |
| 2 | /* |
| 3 | * linux/mm/mmu_notifier.c |
| 4 | * |
| 5 | * Copyright (C) 2008 Qumranet, Inc. |
| 6 | * Copyright (C) 2008 SGI |
| 7 | * Christoph Lameter <cl@linux.com> |
| 8 | */ |
| 9 | |
| 10 | #include <linux/rculist.h> |
| 11 | #include <linux/mmu_notifier.h> |
| 12 | #include <linux/export.h> |
| 13 | #include <linux/mm.h> |
| 14 | #include <linux/err.h> |
| 15 | #include <linux/interval_tree.h> |
| 16 | #include <linux/srcu.h> |
| 17 | #include <linux/rcupdate.h> |
| 18 | #include <linux/sched.h> |
| 19 | #include <linux/sched/mm.h> |
| 20 | #include <linux/slab.h> |
| 21 | |
| 22 | /* global SRCU for all MMs */ |
| 23 | DEFINE_STATIC_SRCU(srcu); |
| 24 | |
| 25 | #ifdef CONFIG_LOCKDEP |
| 26 | struct lockdep_map __mmu_notifier_invalidate_range_start_map = { |
| 27 | .name = "mmu_notifier_invalidate_range_start" |
| 28 | }; |
| 29 | #endif |
| 30 | |
| 31 | /* |
| 32 | * The mmu_notifier_subscriptions structure is allocated and installed in |
| 33 | * mm->notifier_subscriptions inside the mm_take_all_locks() protected |
| 34 | * critical section and it's released only when mm_count reaches zero |
| 35 | * in mmdrop(). |
| 36 | */ |
| 37 | struct mmu_notifier_subscriptions { |
| 38 | /* all mmu notifiers registered in this mm are queued in this list */ |
| 39 | struct hlist_head list; |
| 40 | bool has_itree; |
| 41 | /* to serialize the list modifications and hlist_unhashed */ |
| 42 | spinlock_t lock; |
| 43 | unsigned long invalidate_seq; |
| 44 | unsigned long active_invalidate_ranges; |
| 45 | struct rb_root_cached itree; |
| 46 | wait_queue_head_t wq; |
| 47 | struct hlist_head deferred_list; |
| 48 | }; |
| 49 | |
| 50 | /* |
| 51 | * This is a collision-retry read-side/write-side 'lock', a lot like a |
| 52 | * seqcount, however this allows multiple write-sides to hold it at |
| 53 | * once. Conceptually the write side is protecting the values of the PTEs in |
| 54 | * this mm, such that PTES cannot be read into SPTEs (shadow PTEs) while any |
| 55 | * writer exists. |
| 56 | * |
| 57 | * Note that the core mm creates nested invalidate_range_start()/end() regions |
| 58 | * within the same thread, and runs invalidate_range_start()/end() in parallel |
| 59 | * on multiple CPUs. This is designed to not reduce concurrency or block |
| 60 | * progress on the mm side. |
| 61 | * |
| 62 | * As a secondary function, holding the full write side also serves to prevent |
| 63 | * writers for the itree, this is an optimization to avoid extra locking |
| 64 | * during invalidate_range_start/end notifiers. |
| 65 | * |
| 66 | * The write side has two states, fully excluded: |
| 67 | * - mm->active_invalidate_ranges != 0 |
| 68 | * - subscriptions->invalidate_seq & 1 == True (odd) |
| 69 | * - some range on the mm_struct is being invalidated |
| 70 | * - the itree is not allowed to change |
| 71 | * |
| 72 | * And partially excluded: |
| 73 | * - mm->active_invalidate_ranges != 0 |
| 74 | * - subscriptions->invalidate_seq & 1 == False (even) |
| 75 | * - some range on the mm_struct is being invalidated |
| 76 | * - the itree is allowed to change |
| 77 | * |
| 78 | * Operations on notifier_subscriptions->invalidate_seq (under spinlock): |
| 79 | * seq |= 1 # Begin writing |
| 80 | * seq++ # Release the writing state |
| 81 | * seq & 1 # True if a writer exists |
| 82 | * |
| 83 | * The later state avoids some expensive work on inv_end in the common case of |
| 84 | * no mmu_interval_notifier monitoring the VA. |
| 85 | */ |
| 86 | static bool |
| 87 | mn_itree_is_invalidating(struct mmu_notifier_subscriptions *subscriptions) |
| 88 | { |
| 89 | lockdep_assert_held(&subscriptions->lock); |
| 90 | return subscriptions->invalidate_seq & 1; |
| 91 | } |
| 92 | |
| 93 | static struct mmu_interval_notifier * |
| 94 | mn_itree_inv_start_range(struct mmu_notifier_subscriptions *subscriptions, |
| 95 | const struct mmu_notifier_range *range, |
| 96 | unsigned long *seq) |
| 97 | { |
| 98 | struct interval_tree_node *node; |
| 99 | struct mmu_interval_notifier *res = NULL; |
| 100 | |
| 101 | spin_lock(&subscriptions->lock); |
| 102 | subscriptions->active_invalidate_ranges++; |
| 103 | node = interval_tree_iter_first(&subscriptions->itree, range->start, |
| 104 | range->end - 1); |
| 105 | if (node) { |
| 106 | subscriptions->invalidate_seq |= 1; |
| 107 | res = container_of(node, struct mmu_interval_notifier, |
| 108 | interval_tree); |
| 109 | } |
| 110 | |
| 111 | *seq = subscriptions->invalidate_seq; |
| 112 | spin_unlock(&subscriptions->lock); |
| 113 | return res; |
| 114 | } |
| 115 | |
| 116 | static struct mmu_interval_notifier * |
| 117 | mn_itree_inv_next(struct mmu_interval_notifier *interval_sub, |
| 118 | const struct mmu_notifier_range *range) |
| 119 | { |
| 120 | struct interval_tree_node *node; |
| 121 | |
| 122 | node = interval_tree_iter_next(&interval_sub->interval_tree, |
| 123 | range->start, range->end - 1); |
| 124 | if (!node) |
| 125 | return NULL; |
| 126 | return container_of(node, struct mmu_interval_notifier, interval_tree); |
| 127 | } |
| 128 | |
| 129 | static void mn_itree_inv_end(struct mmu_notifier_subscriptions *subscriptions) |
| 130 | { |
| 131 | struct mmu_interval_notifier *interval_sub; |
| 132 | struct hlist_node *next; |
| 133 | |
| 134 | spin_lock(&subscriptions->lock); |
| 135 | if (--subscriptions->active_invalidate_ranges || |
| 136 | !mn_itree_is_invalidating(subscriptions)) { |
| 137 | spin_unlock(&subscriptions->lock); |
| 138 | return; |
| 139 | } |
| 140 | |
| 141 | /* Make invalidate_seq even */ |
| 142 | subscriptions->invalidate_seq++; |
| 143 | |
| 144 | /* |
| 145 | * The inv_end incorporates a deferred mechanism like rtnl_unlock(). |
| 146 | * Adds and removes are queued until the final inv_end happens then |
| 147 | * they are progressed. This arrangement for tree updates is used to |
| 148 | * avoid using a blocking lock during invalidate_range_start. |
| 149 | */ |
| 150 | hlist_for_each_entry_safe(interval_sub, next, |
| 151 | &subscriptions->deferred_list, |
| 152 | deferred_item) { |
| 153 | if (RB_EMPTY_NODE(&interval_sub->interval_tree.rb)) |
| 154 | interval_tree_insert(&interval_sub->interval_tree, |
| 155 | &subscriptions->itree); |
| 156 | else |
| 157 | interval_tree_remove(&interval_sub->interval_tree, |
| 158 | &subscriptions->itree); |
| 159 | hlist_del(&interval_sub->deferred_item); |
| 160 | } |
| 161 | spin_unlock(&subscriptions->lock); |
| 162 | |
| 163 | wake_up_all(&subscriptions->wq); |
| 164 | } |
| 165 | |
| 166 | /** |
| 167 | * mmu_interval_read_begin - Begin a read side critical section against a VA |
| 168 | * range |
| 169 | * @interval_sub: The interval subscription |
| 170 | * |
| 171 | * mmu_iterval_read_begin()/mmu_iterval_read_retry() implement a |
| 172 | * collision-retry scheme similar to seqcount for the VA range under |
| 173 | * subscription. If the mm invokes invalidation during the critical section |
| 174 | * then mmu_interval_read_retry() will return true. |
| 175 | * |
| 176 | * This is useful to obtain shadow PTEs where teardown or setup of the SPTEs |
| 177 | * require a blocking context. The critical region formed by this can sleep, |
| 178 | * and the required 'user_lock' can also be a sleeping lock. |
| 179 | * |
| 180 | * The caller is required to provide a 'user_lock' to serialize both teardown |
| 181 | * and setup. |
| 182 | * |
| 183 | * The return value should be passed to mmu_interval_read_retry(). |
| 184 | */ |
| 185 | unsigned long |
| 186 | mmu_interval_read_begin(struct mmu_interval_notifier *interval_sub) |
| 187 | { |
| 188 | struct mmu_notifier_subscriptions *subscriptions = |
| 189 | interval_sub->mm->notifier_subscriptions; |
| 190 | unsigned long seq; |
| 191 | bool is_invalidating; |
| 192 | |
| 193 | /* |
| 194 | * If the subscription has a different seq value under the user_lock |
| 195 | * than we started with then it has collided. |
| 196 | * |
| 197 | * If the subscription currently has the same seq value as the |
| 198 | * subscriptions seq, then it is currently between |
| 199 | * invalidate_start/end and is colliding. |
| 200 | * |
| 201 | * The locking looks broadly like this: |
| 202 | * mn_tree_invalidate_start(): mmu_interval_read_begin(): |
| 203 | * spin_lock |
| 204 | * seq = READ_ONCE(interval_sub->invalidate_seq); |
| 205 | * seq == subs->invalidate_seq |
| 206 | * spin_unlock |
| 207 | * spin_lock |
| 208 | * seq = ++subscriptions->invalidate_seq |
| 209 | * spin_unlock |
| 210 | * op->invalidate_range(): |
| 211 | * user_lock |
| 212 | * mmu_interval_set_seq() |
| 213 | * interval_sub->invalidate_seq = seq |
| 214 | * user_unlock |
| 215 | * |
| 216 | * [Required: mmu_interval_read_retry() == true] |
| 217 | * |
| 218 | * mn_itree_inv_end(): |
| 219 | * spin_lock |
| 220 | * seq = ++subscriptions->invalidate_seq |
| 221 | * spin_unlock |
| 222 | * |
| 223 | * user_lock |
| 224 | * mmu_interval_read_retry(): |
| 225 | * interval_sub->invalidate_seq != seq |
| 226 | * user_unlock |
| 227 | * |
| 228 | * Barriers are not needed here as any races here are closed by an |
| 229 | * eventual mmu_interval_read_retry(), which provides a barrier via the |
| 230 | * user_lock. |
| 231 | */ |
| 232 | spin_lock(&subscriptions->lock); |
| 233 | /* Pairs with the WRITE_ONCE in mmu_interval_set_seq() */ |
| 234 | seq = READ_ONCE(interval_sub->invalidate_seq); |
| 235 | is_invalidating = seq == subscriptions->invalidate_seq; |
| 236 | spin_unlock(&subscriptions->lock); |
| 237 | |
| 238 | /* |
| 239 | * interval_sub->invalidate_seq must always be set to an odd value via |
| 240 | * mmu_interval_set_seq() using the provided cur_seq from |
| 241 | * mn_itree_inv_start_range(). This ensures that if seq does wrap we |
| 242 | * will always clear the below sleep in some reasonable time as |
| 243 | * subscriptions->invalidate_seq is even in the idle state. |
| 244 | */ |
| 245 | lock_map_acquire(&__mmu_notifier_invalidate_range_start_map); |
| 246 | lock_map_release(&__mmu_notifier_invalidate_range_start_map); |
| 247 | if (is_invalidating) |
| 248 | wait_event(subscriptions->wq, |
| 249 | READ_ONCE(subscriptions->invalidate_seq) != seq); |
| 250 | |
| 251 | /* |
| 252 | * Notice that mmu_interval_read_retry() can already be true at this |
| 253 | * point, avoiding loops here allows the caller to provide a global |
| 254 | * time bound. |
| 255 | */ |
| 256 | |
| 257 | return seq; |
| 258 | } |
| 259 | EXPORT_SYMBOL_GPL(mmu_interval_read_begin); |
| 260 | |
| 261 | static void mn_itree_release(struct mmu_notifier_subscriptions *subscriptions, |
| 262 | struct mm_struct *mm) |
| 263 | { |
| 264 | struct mmu_notifier_range range = { |
| 265 | .flags = MMU_NOTIFIER_RANGE_BLOCKABLE, |
| 266 | .event = MMU_NOTIFY_RELEASE, |
| 267 | .mm = mm, |
| 268 | .start = 0, |
| 269 | .end = ULONG_MAX, |
| 270 | }; |
| 271 | struct mmu_interval_notifier *interval_sub; |
| 272 | unsigned long cur_seq; |
| 273 | bool ret; |
| 274 | |
| 275 | for (interval_sub = |
| 276 | mn_itree_inv_start_range(subscriptions, &range, &cur_seq); |
| 277 | interval_sub; |
| 278 | interval_sub = mn_itree_inv_next(interval_sub, &range)) { |
| 279 | ret = interval_sub->ops->invalidate(interval_sub, &range, |
| 280 | cur_seq); |
| 281 | WARN_ON(!ret); |
| 282 | } |
| 283 | |
| 284 | mn_itree_inv_end(subscriptions); |
| 285 | } |
| 286 | |
| 287 | /* |
| 288 | * This function can't run concurrently against mmu_notifier_register |
| 289 | * because mm->mm_users > 0 during mmu_notifier_register and exit_mmap |
| 290 | * runs with mm_users == 0. Other tasks may still invoke mmu notifiers |
| 291 | * in parallel despite there being no task using this mm any more, |
| 292 | * through the vmas outside of the exit_mmap context, such as with |
| 293 | * vmtruncate. This serializes against mmu_notifier_unregister with |
| 294 | * the notifier_subscriptions->lock in addition to SRCU and it serializes |
| 295 | * against the other mmu notifiers with SRCU. struct mmu_notifier_subscriptions |
| 296 | * can't go away from under us as exit_mmap holds an mm_count pin |
| 297 | * itself. |
| 298 | */ |
| 299 | static void mn_hlist_release(struct mmu_notifier_subscriptions *subscriptions, |
| 300 | struct mm_struct *mm) |
| 301 | { |
| 302 | struct mmu_notifier *subscription; |
| 303 | int id; |
| 304 | |
| 305 | /* |
| 306 | * SRCU here will block mmu_notifier_unregister until |
| 307 | * ->release returns. |
| 308 | */ |
| 309 | id = srcu_read_lock(&srcu); |
| 310 | hlist_for_each_entry_rcu(subscription, &subscriptions->list, hlist, |
| 311 | srcu_read_lock_held(&srcu)) |
| 312 | /* |
| 313 | * If ->release runs before mmu_notifier_unregister it must be |
| 314 | * handled, as it's the only way for the driver to flush all |
| 315 | * existing sptes and stop the driver from establishing any more |
| 316 | * sptes before all the pages in the mm are freed. |
| 317 | */ |
| 318 | if (subscription->ops->release) |
| 319 | subscription->ops->release(subscription, mm); |
| 320 | |
| 321 | spin_lock(&subscriptions->lock); |
| 322 | while (unlikely(!hlist_empty(&subscriptions->list))) { |
| 323 | subscription = hlist_entry(subscriptions->list.first, |
| 324 | struct mmu_notifier, hlist); |
| 325 | /* |
| 326 | * We arrived before mmu_notifier_unregister so |
| 327 | * mmu_notifier_unregister will do nothing other than to wait |
| 328 | * for ->release to finish and for mmu_notifier_unregister to |
| 329 | * return. |
| 330 | */ |
| 331 | hlist_del_init_rcu(&subscription->hlist); |
| 332 | } |
| 333 | spin_unlock(&subscriptions->lock); |
| 334 | srcu_read_unlock(&srcu, id); |
| 335 | |
| 336 | /* |
| 337 | * synchronize_srcu here prevents mmu_notifier_release from returning to |
| 338 | * exit_mmap (which would proceed with freeing all pages in the mm) |
| 339 | * until the ->release method returns, if it was invoked by |
| 340 | * mmu_notifier_unregister. |
| 341 | * |
| 342 | * The notifier_subscriptions can't go away from under us because |
| 343 | * one mm_count is held by exit_mmap. |
| 344 | */ |
| 345 | synchronize_srcu(&srcu); |
| 346 | } |
| 347 | |
| 348 | void __mmu_notifier_release(struct mm_struct *mm) |
| 349 | { |
| 350 | struct mmu_notifier_subscriptions *subscriptions = |
| 351 | mm->notifier_subscriptions; |
| 352 | |
| 353 | if (subscriptions->has_itree) |
| 354 | mn_itree_release(subscriptions, mm); |
| 355 | |
| 356 | if (!hlist_empty(&subscriptions->list)) |
| 357 | mn_hlist_release(subscriptions, mm); |
| 358 | } |
| 359 | |
| 360 | /* |
| 361 | * If no young bitflag is supported by the hardware, ->clear_flush_young can |
| 362 | * unmap the address and return 1 or 0 depending if the mapping previously |
| 363 | * existed or not. |
| 364 | */ |
| 365 | int __mmu_notifier_clear_flush_young(struct mm_struct *mm, |
| 366 | unsigned long start, |
| 367 | unsigned long end) |
| 368 | { |
| 369 | struct mmu_notifier *subscription; |
| 370 | int young = 0, id; |
| 371 | |
| 372 | id = srcu_read_lock(&srcu); |
| 373 | hlist_for_each_entry_rcu(subscription, |
| 374 | &mm->notifier_subscriptions->list, hlist, |
| 375 | srcu_read_lock_held(&srcu)) { |
| 376 | if (subscription->ops->clear_flush_young) |
| 377 | young |= subscription->ops->clear_flush_young( |
| 378 | subscription, mm, start, end); |
| 379 | } |
| 380 | srcu_read_unlock(&srcu, id); |
| 381 | |
| 382 | return young; |
| 383 | } |
| 384 | |
| 385 | int __mmu_notifier_clear_young(struct mm_struct *mm, |
| 386 | unsigned long start, |
| 387 | unsigned long end) |
| 388 | { |
| 389 | struct mmu_notifier *subscription; |
| 390 | int young = 0, id; |
| 391 | |
| 392 | id = srcu_read_lock(&srcu); |
| 393 | hlist_for_each_entry_rcu(subscription, |
| 394 | &mm->notifier_subscriptions->list, hlist, |
| 395 | srcu_read_lock_held(&srcu)) { |
| 396 | if (subscription->ops->clear_young) |
| 397 | young |= subscription->ops->clear_young(subscription, |
| 398 | mm, start, end); |
| 399 | } |
| 400 | srcu_read_unlock(&srcu, id); |
| 401 | |
| 402 | return young; |
| 403 | } |
| 404 | |
| 405 | int __mmu_notifier_test_young(struct mm_struct *mm, |
| 406 | unsigned long address) |
| 407 | { |
| 408 | struct mmu_notifier *subscription; |
| 409 | int young = 0, id; |
| 410 | |
| 411 | id = srcu_read_lock(&srcu); |
| 412 | hlist_for_each_entry_rcu(subscription, |
| 413 | &mm->notifier_subscriptions->list, hlist, |
| 414 | srcu_read_lock_held(&srcu)) { |
| 415 | if (subscription->ops->test_young) { |
| 416 | young = subscription->ops->test_young(subscription, mm, |
| 417 | address); |
| 418 | if (young) |
| 419 | break; |
| 420 | } |
| 421 | } |
| 422 | srcu_read_unlock(&srcu, id); |
| 423 | |
| 424 | return young; |
| 425 | } |
| 426 | |
| 427 | void __mmu_notifier_change_pte(struct mm_struct *mm, unsigned long address, |
| 428 | pte_t pte) |
| 429 | { |
| 430 | struct mmu_notifier *subscription; |
| 431 | int id; |
| 432 | |
| 433 | id = srcu_read_lock(&srcu); |
| 434 | hlist_for_each_entry_rcu(subscription, |
| 435 | &mm->notifier_subscriptions->list, hlist, |
| 436 | srcu_read_lock_held(&srcu)) { |
| 437 | if (subscription->ops->change_pte) |
| 438 | subscription->ops->change_pte(subscription, mm, address, |
| 439 | pte); |
| 440 | } |
| 441 | srcu_read_unlock(&srcu, id); |
| 442 | } |
| 443 | |
| 444 | static int mn_itree_invalidate(struct mmu_notifier_subscriptions *subscriptions, |
| 445 | const struct mmu_notifier_range *range) |
| 446 | { |
| 447 | struct mmu_interval_notifier *interval_sub; |
| 448 | unsigned long cur_seq; |
| 449 | |
| 450 | for (interval_sub = |
| 451 | mn_itree_inv_start_range(subscriptions, range, &cur_seq); |
| 452 | interval_sub; |
| 453 | interval_sub = mn_itree_inv_next(interval_sub, range)) { |
| 454 | bool ret; |
| 455 | |
| 456 | ret = interval_sub->ops->invalidate(interval_sub, range, |
| 457 | cur_seq); |
| 458 | if (!ret) { |
| 459 | if (WARN_ON(mmu_notifier_range_blockable(range))) |
| 460 | continue; |
| 461 | goto out_would_block; |
| 462 | } |
| 463 | } |
| 464 | return 0; |
| 465 | |
| 466 | out_would_block: |
| 467 | /* |
| 468 | * On -EAGAIN the non-blocking caller is not allowed to call |
| 469 | * invalidate_range_end() |
| 470 | */ |
| 471 | mn_itree_inv_end(subscriptions); |
| 472 | return -EAGAIN; |
| 473 | } |
| 474 | |
| 475 | static int mn_hlist_invalidate_range_start( |
| 476 | struct mmu_notifier_subscriptions *subscriptions, |
| 477 | struct mmu_notifier_range *range) |
| 478 | { |
| 479 | struct mmu_notifier *subscription; |
| 480 | int ret = 0; |
| 481 | int id; |
| 482 | |
| 483 | id = srcu_read_lock(&srcu); |
| 484 | hlist_for_each_entry_rcu(subscription, &subscriptions->list, hlist, |
| 485 | srcu_read_lock_held(&srcu)) { |
| 486 | const struct mmu_notifier_ops *ops = subscription->ops; |
| 487 | |
| 488 | if (ops->invalidate_range_start) { |
| 489 | int _ret; |
| 490 | |
| 491 | if (!mmu_notifier_range_blockable(range)) |
| 492 | non_block_start(); |
| 493 | _ret = ops->invalidate_range_start(subscription, range); |
| 494 | if (!mmu_notifier_range_blockable(range)) |
| 495 | non_block_end(); |
| 496 | if (_ret) { |
| 497 | pr_info("%pS callback failed with %d in %sblockable context.\n", |
| 498 | ops->invalidate_range_start, _ret, |
| 499 | !mmu_notifier_range_blockable(range) ? |
| 500 | "non-" : |
| 501 | ""); |
| 502 | WARN_ON(mmu_notifier_range_blockable(range) || |
| 503 | _ret != -EAGAIN); |
| 504 | /* |
| 505 | * We call all the notifiers on any EAGAIN, |
| 506 | * there is no way for a notifier to know if |
| 507 | * its start method failed, thus a start that |
| 508 | * does EAGAIN can't also do end. |
| 509 | */ |
| 510 | WARN_ON(ops->invalidate_range_end); |
| 511 | ret = _ret; |
| 512 | } |
| 513 | } |
| 514 | } |
| 515 | |
| 516 | if (ret) { |
| 517 | /* |
| 518 | * Must be non-blocking to get here. If there are multiple |
| 519 | * notifiers and one or more failed start, any that succeeded |
| 520 | * start are expecting their end to be called. Do so now. |
| 521 | */ |
| 522 | hlist_for_each_entry_rcu(subscription, &subscriptions->list, |
| 523 | hlist, srcu_read_lock_held(&srcu)) { |
| 524 | if (!subscription->ops->invalidate_range_end) |
| 525 | continue; |
| 526 | |
| 527 | subscription->ops->invalidate_range_end(subscription, |
| 528 | range); |
| 529 | } |
| 530 | } |
| 531 | srcu_read_unlock(&srcu, id); |
| 532 | |
| 533 | return ret; |
| 534 | } |
| 535 | |
| 536 | int __mmu_notifier_invalidate_range_start(struct mmu_notifier_range *range) |
| 537 | { |
| 538 | struct mmu_notifier_subscriptions *subscriptions = |
| 539 | range->mm->notifier_subscriptions; |
| 540 | int ret; |
| 541 | |
| 542 | if (subscriptions->has_itree) { |
| 543 | ret = mn_itree_invalidate(subscriptions, range); |
| 544 | if (ret) |
| 545 | return ret; |
| 546 | } |
| 547 | if (!hlist_empty(&subscriptions->list)) |
| 548 | return mn_hlist_invalidate_range_start(subscriptions, range); |
| 549 | return 0; |
| 550 | } |
| 551 | |
| 552 | static void |
| 553 | mn_hlist_invalidate_end(struct mmu_notifier_subscriptions *subscriptions, |
| 554 | struct mmu_notifier_range *range, bool only_end) |
| 555 | { |
| 556 | struct mmu_notifier *subscription; |
| 557 | int id; |
| 558 | |
| 559 | id = srcu_read_lock(&srcu); |
| 560 | hlist_for_each_entry_rcu(subscription, &subscriptions->list, hlist, |
| 561 | srcu_read_lock_held(&srcu)) { |
| 562 | /* |
| 563 | * Call invalidate_range here too to avoid the need for the |
| 564 | * subsystem of having to register an invalidate_range_end |
| 565 | * call-back when there is invalidate_range already. Usually a |
| 566 | * subsystem registers either invalidate_range_start()/end() or |
| 567 | * invalidate_range(), so this will be no additional overhead |
| 568 | * (besides the pointer check). |
| 569 | * |
| 570 | * We skip call to invalidate_range() if we know it is safe ie |
| 571 | * call site use mmu_notifier_invalidate_range_only_end() which |
| 572 | * is safe to do when we know that a call to invalidate_range() |
| 573 | * already happen under page table lock. |
| 574 | */ |
| 575 | if (!only_end && subscription->ops->invalidate_range) |
| 576 | subscription->ops->invalidate_range(subscription, |
| 577 | range->mm, |
| 578 | range->start, |
| 579 | range->end); |
| 580 | if (subscription->ops->invalidate_range_end) { |
| 581 | if (!mmu_notifier_range_blockable(range)) |
| 582 | non_block_start(); |
| 583 | subscription->ops->invalidate_range_end(subscription, |
| 584 | range); |
| 585 | if (!mmu_notifier_range_blockable(range)) |
| 586 | non_block_end(); |
| 587 | } |
| 588 | } |
| 589 | srcu_read_unlock(&srcu, id); |
| 590 | } |
| 591 | |
| 592 | void __mmu_notifier_invalidate_range_end(struct mmu_notifier_range *range, |
| 593 | bool only_end) |
| 594 | { |
| 595 | struct mmu_notifier_subscriptions *subscriptions = |
| 596 | range->mm->notifier_subscriptions; |
| 597 | |
| 598 | lock_map_acquire(&__mmu_notifier_invalidate_range_start_map); |
| 599 | if (subscriptions->has_itree) |
| 600 | mn_itree_inv_end(subscriptions); |
| 601 | |
| 602 | if (!hlist_empty(&subscriptions->list)) |
| 603 | mn_hlist_invalidate_end(subscriptions, range, only_end); |
| 604 | lock_map_release(&__mmu_notifier_invalidate_range_start_map); |
| 605 | } |
| 606 | |
| 607 | void __mmu_notifier_invalidate_range(struct mm_struct *mm, |
| 608 | unsigned long start, unsigned long end) |
| 609 | { |
| 610 | struct mmu_notifier *subscription; |
| 611 | int id; |
| 612 | |
| 613 | id = srcu_read_lock(&srcu); |
| 614 | hlist_for_each_entry_rcu(subscription, |
| 615 | &mm->notifier_subscriptions->list, hlist, |
| 616 | srcu_read_lock_held(&srcu)) { |
| 617 | if (subscription->ops->invalidate_range) |
| 618 | subscription->ops->invalidate_range(subscription, mm, |
| 619 | start, end); |
| 620 | } |
| 621 | srcu_read_unlock(&srcu, id); |
| 622 | } |
| 623 | |
| 624 | /* |
| 625 | * Same as mmu_notifier_register but here the caller must hold the mmap_lock in |
| 626 | * write mode. A NULL mn signals the notifier is being registered for itree |
| 627 | * mode. |
| 628 | */ |
| 629 | int __mmu_notifier_register(struct mmu_notifier *subscription, |
| 630 | struct mm_struct *mm) |
| 631 | { |
| 632 | struct mmu_notifier_subscriptions *subscriptions = NULL; |
| 633 | int ret; |
| 634 | |
| 635 | mmap_assert_write_locked(mm); |
| 636 | BUG_ON(atomic_read(&mm->mm_users) <= 0); |
| 637 | |
| 638 | if (!mm->notifier_subscriptions) { |
| 639 | /* |
| 640 | * kmalloc cannot be called under mm_take_all_locks(), but we |
| 641 | * know that mm->notifier_subscriptions can't change while we |
| 642 | * hold the write side of the mmap_lock. |
| 643 | */ |
| 644 | subscriptions = kzalloc( |
| 645 | sizeof(struct mmu_notifier_subscriptions), GFP_KERNEL); |
| 646 | if (!subscriptions) |
| 647 | return -ENOMEM; |
| 648 | |
| 649 | INIT_HLIST_HEAD(&subscriptions->list); |
| 650 | spin_lock_init(&subscriptions->lock); |
| 651 | subscriptions->invalidate_seq = 2; |
| 652 | subscriptions->itree = RB_ROOT_CACHED; |
| 653 | init_waitqueue_head(&subscriptions->wq); |
| 654 | INIT_HLIST_HEAD(&subscriptions->deferred_list); |
| 655 | } |
| 656 | |
| 657 | ret = mm_take_all_locks(mm); |
| 658 | if (unlikely(ret)) |
| 659 | goto out_clean; |
| 660 | |
| 661 | /* |
| 662 | * Serialize the update against mmu_notifier_unregister. A |
| 663 | * side note: mmu_notifier_release can't run concurrently with |
| 664 | * us because we hold the mm_users pin (either implicitly as |
| 665 | * current->mm or explicitly with get_task_mm() or similar). |
| 666 | * We can't race against any other mmu notifier method either |
| 667 | * thanks to mm_take_all_locks(). |
| 668 | * |
| 669 | * release semantics on the initialization of the |
| 670 | * mmu_notifier_subscriptions's contents are provided for unlocked |
| 671 | * readers. acquire can only be used while holding the mmgrab or |
| 672 | * mmget, and is safe because once created the |
| 673 | * mmu_notifier_subscriptions is not freed until the mm is destroyed. |
| 674 | * As above, users holding the mmap_lock or one of the |
| 675 | * mm_take_all_locks() do not need to use acquire semantics. |
| 676 | */ |
| 677 | if (subscriptions) |
| 678 | smp_store_release(&mm->notifier_subscriptions, subscriptions); |
| 679 | |
| 680 | if (subscription) { |
| 681 | /* Pairs with the mmdrop in mmu_notifier_unregister_* */ |
| 682 | mmgrab(mm); |
| 683 | subscription->mm = mm; |
| 684 | subscription->users = 1; |
| 685 | |
| 686 | spin_lock(&mm->notifier_subscriptions->lock); |
| 687 | hlist_add_head_rcu(&subscription->hlist, |
| 688 | &mm->notifier_subscriptions->list); |
| 689 | spin_unlock(&mm->notifier_subscriptions->lock); |
| 690 | } else |
| 691 | mm->notifier_subscriptions->has_itree = true; |
| 692 | |
| 693 | mm_drop_all_locks(mm); |
| 694 | BUG_ON(atomic_read(&mm->mm_users) <= 0); |
| 695 | return 0; |
| 696 | |
| 697 | out_clean: |
| 698 | kfree(subscriptions); |
| 699 | return ret; |
| 700 | } |
| 701 | EXPORT_SYMBOL_GPL(__mmu_notifier_register); |
| 702 | |
| 703 | /** |
| 704 | * mmu_notifier_register - Register a notifier on a mm |
| 705 | * @subscription: The notifier to attach |
| 706 | * @mm: The mm to attach the notifier to |
| 707 | * |
| 708 | * Must not hold mmap_lock nor any other VM related lock when calling |
| 709 | * this registration function. Must also ensure mm_users can't go down |
| 710 | * to zero while this runs to avoid races with mmu_notifier_release, |
| 711 | * so mm has to be current->mm or the mm should be pinned safely such |
| 712 | * as with get_task_mm(). If the mm is not current->mm, the mm_users |
| 713 | * pin should be released by calling mmput after mmu_notifier_register |
| 714 | * returns. |
| 715 | * |
| 716 | * mmu_notifier_unregister() or mmu_notifier_put() must be always called to |
| 717 | * unregister the notifier. |
| 718 | * |
| 719 | * While the caller has a mmu_notifier get the subscription->mm pointer will remain |
| 720 | * valid, and can be converted to an active mm pointer via mmget_not_zero(). |
| 721 | */ |
| 722 | int mmu_notifier_register(struct mmu_notifier *subscription, |
| 723 | struct mm_struct *mm) |
| 724 | { |
| 725 | int ret; |
| 726 | |
| 727 | mmap_write_lock(mm); |
| 728 | ret = __mmu_notifier_register(subscription, mm); |
| 729 | mmap_write_unlock(mm); |
| 730 | return ret; |
| 731 | } |
| 732 | EXPORT_SYMBOL_GPL(mmu_notifier_register); |
| 733 | |
| 734 | static struct mmu_notifier * |
| 735 | find_get_mmu_notifier(struct mm_struct *mm, const struct mmu_notifier_ops *ops) |
| 736 | { |
| 737 | struct mmu_notifier *subscription; |
| 738 | |
| 739 | spin_lock(&mm->notifier_subscriptions->lock); |
| 740 | hlist_for_each_entry_rcu(subscription, |
| 741 | &mm->notifier_subscriptions->list, hlist, |
| 742 | lockdep_is_held(&mm->notifier_subscriptions->lock)) { |
| 743 | if (subscription->ops != ops) |
| 744 | continue; |
| 745 | |
| 746 | if (likely(subscription->users != UINT_MAX)) |
| 747 | subscription->users++; |
| 748 | else |
| 749 | subscription = ERR_PTR(-EOVERFLOW); |
| 750 | spin_unlock(&mm->notifier_subscriptions->lock); |
| 751 | return subscription; |
| 752 | } |
| 753 | spin_unlock(&mm->notifier_subscriptions->lock); |
| 754 | return NULL; |
| 755 | } |
| 756 | |
| 757 | /** |
| 758 | * mmu_notifier_get_locked - Return the single struct mmu_notifier for |
| 759 | * the mm & ops |
| 760 | * @ops: The operations struct being subscribe with |
| 761 | * @mm : The mm to attach notifiers too |
| 762 | * |
| 763 | * This function either allocates a new mmu_notifier via |
| 764 | * ops->alloc_notifier(), or returns an already existing notifier on the |
| 765 | * list. The value of the ops pointer is used to determine when two notifiers |
| 766 | * are the same. |
| 767 | * |
| 768 | * Each call to mmu_notifier_get() must be paired with a call to |
| 769 | * mmu_notifier_put(). The caller must hold the write side of mm->mmap_lock. |
| 770 | * |
| 771 | * While the caller has a mmu_notifier get the mm pointer will remain valid, |
| 772 | * and can be converted to an active mm pointer via mmget_not_zero(). |
| 773 | */ |
| 774 | struct mmu_notifier *mmu_notifier_get_locked(const struct mmu_notifier_ops *ops, |
| 775 | struct mm_struct *mm) |
| 776 | { |
| 777 | struct mmu_notifier *subscription; |
| 778 | int ret; |
| 779 | |
| 780 | mmap_assert_write_locked(mm); |
| 781 | |
| 782 | if (mm->notifier_subscriptions) { |
| 783 | subscription = find_get_mmu_notifier(mm, ops); |
| 784 | if (subscription) |
| 785 | return subscription; |
| 786 | } |
| 787 | |
| 788 | subscription = ops->alloc_notifier(mm); |
| 789 | if (IS_ERR(subscription)) |
| 790 | return subscription; |
| 791 | subscription->ops = ops; |
| 792 | ret = __mmu_notifier_register(subscription, mm); |
| 793 | if (ret) |
| 794 | goto out_free; |
| 795 | return subscription; |
| 796 | out_free: |
| 797 | subscription->ops->free_notifier(subscription); |
| 798 | return ERR_PTR(ret); |
| 799 | } |
| 800 | EXPORT_SYMBOL_GPL(mmu_notifier_get_locked); |
| 801 | |
| 802 | /* this is called after the last mmu_notifier_unregister() returned */ |
| 803 | void __mmu_notifier_subscriptions_destroy(struct mm_struct *mm) |
| 804 | { |
| 805 | BUG_ON(!hlist_empty(&mm->notifier_subscriptions->list)); |
| 806 | kfree(mm->notifier_subscriptions); |
| 807 | mm->notifier_subscriptions = LIST_POISON1; /* debug */ |
| 808 | } |
| 809 | |
| 810 | /* |
| 811 | * This releases the mm_count pin automatically and frees the mm |
| 812 | * structure if it was the last user of it. It serializes against |
| 813 | * running mmu notifiers with SRCU and against mmu_notifier_unregister |
| 814 | * with the unregister lock + SRCU. All sptes must be dropped before |
| 815 | * calling mmu_notifier_unregister. ->release or any other notifier |
| 816 | * method may be invoked concurrently with mmu_notifier_unregister, |
| 817 | * and only after mmu_notifier_unregister returned we're guaranteed |
| 818 | * that ->release or any other method can't run anymore. |
| 819 | */ |
| 820 | void mmu_notifier_unregister(struct mmu_notifier *subscription, |
| 821 | struct mm_struct *mm) |
| 822 | { |
| 823 | BUG_ON(atomic_read(&mm->mm_count) <= 0); |
| 824 | |
| 825 | if (!hlist_unhashed(&subscription->hlist)) { |
| 826 | /* |
| 827 | * SRCU here will force exit_mmap to wait for ->release to |
| 828 | * finish before freeing the pages. |
| 829 | */ |
| 830 | int id; |
| 831 | |
| 832 | id = srcu_read_lock(&srcu); |
| 833 | /* |
| 834 | * exit_mmap will block in mmu_notifier_release to guarantee |
| 835 | * that ->release is called before freeing the pages. |
| 836 | */ |
| 837 | if (subscription->ops->release) |
| 838 | subscription->ops->release(subscription, mm); |
| 839 | srcu_read_unlock(&srcu, id); |
| 840 | |
| 841 | spin_lock(&mm->notifier_subscriptions->lock); |
| 842 | /* |
| 843 | * Can not use list_del_rcu() since __mmu_notifier_release |
| 844 | * can delete it before we hold the lock. |
| 845 | */ |
| 846 | hlist_del_init_rcu(&subscription->hlist); |
| 847 | spin_unlock(&mm->notifier_subscriptions->lock); |
| 848 | } |
| 849 | |
| 850 | /* |
| 851 | * Wait for any running method to finish, of course including |
| 852 | * ->release if it was run by mmu_notifier_release instead of us. |
| 853 | */ |
| 854 | synchronize_srcu(&srcu); |
| 855 | |
| 856 | BUG_ON(atomic_read(&mm->mm_count) <= 0); |
| 857 | |
| 858 | mmdrop(mm); |
| 859 | } |
| 860 | EXPORT_SYMBOL_GPL(mmu_notifier_unregister); |
| 861 | |
| 862 | static void mmu_notifier_free_rcu(struct rcu_head *rcu) |
| 863 | { |
| 864 | struct mmu_notifier *subscription = |
| 865 | container_of(rcu, struct mmu_notifier, rcu); |
| 866 | struct mm_struct *mm = subscription->mm; |
| 867 | |
| 868 | subscription->ops->free_notifier(subscription); |
| 869 | /* Pairs with the get in __mmu_notifier_register() */ |
| 870 | mmdrop(mm); |
| 871 | } |
| 872 | |
| 873 | /** |
| 874 | * mmu_notifier_put - Release the reference on the notifier |
| 875 | * @subscription: The notifier to act on |
| 876 | * |
| 877 | * This function must be paired with each mmu_notifier_get(), it releases the |
| 878 | * reference obtained by the get. If this is the last reference then process |
| 879 | * to free the notifier will be run asynchronously. |
| 880 | * |
| 881 | * Unlike mmu_notifier_unregister() the get/put flow only calls ops->release |
| 882 | * when the mm_struct is destroyed. Instead free_notifier is always called to |
| 883 | * release any resources held by the user. |
| 884 | * |
| 885 | * As ops->release is not guaranteed to be called, the user must ensure that |
| 886 | * all sptes are dropped, and no new sptes can be established before |
| 887 | * mmu_notifier_put() is called. |
| 888 | * |
| 889 | * This function can be called from the ops->release callback, however the |
| 890 | * caller must still ensure it is called pairwise with mmu_notifier_get(). |
| 891 | * |
| 892 | * Modules calling this function must call mmu_notifier_synchronize() in |
| 893 | * their __exit functions to ensure the async work is completed. |
| 894 | */ |
| 895 | void mmu_notifier_put(struct mmu_notifier *subscription) |
| 896 | { |
| 897 | struct mm_struct *mm = subscription->mm; |
| 898 | |
| 899 | spin_lock(&mm->notifier_subscriptions->lock); |
| 900 | if (WARN_ON(!subscription->users) || --subscription->users) |
| 901 | goto out_unlock; |
| 902 | hlist_del_init_rcu(&subscription->hlist); |
| 903 | spin_unlock(&mm->notifier_subscriptions->lock); |
| 904 | |
| 905 | call_srcu(&srcu, &subscription->rcu, mmu_notifier_free_rcu); |
| 906 | return; |
| 907 | |
| 908 | out_unlock: |
| 909 | spin_unlock(&mm->notifier_subscriptions->lock); |
| 910 | } |
| 911 | EXPORT_SYMBOL_GPL(mmu_notifier_put); |
| 912 | |
| 913 | static int __mmu_interval_notifier_insert( |
| 914 | struct mmu_interval_notifier *interval_sub, struct mm_struct *mm, |
| 915 | struct mmu_notifier_subscriptions *subscriptions, unsigned long start, |
| 916 | unsigned long length, const struct mmu_interval_notifier_ops *ops) |
| 917 | { |
| 918 | interval_sub->mm = mm; |
| 919 | interval_sub->ops = ops; |
| 920 | RB_CLEAR_NODE(&interval_sub->interval_tree.rb); |
| 921 | interval_sub->interval_tree.start = start; |
| 922 | /* |
| 923 | * Note that the representation of the intervals in the interval tree |
| 924 | * considers the ending point as contained in the interval. |
| 925 | */ |
| 926 | if (length == 0 || |
| 927 | check_add_overflow(start, length - 1, |
| 928 | &interval_sub->interval_tree.last)) |
| 929 | return -EOVERFLOW; |
| 930 | |
| 931 | /* Must call with a mmget() held */ |
| 932 | if (WARN_ON(atomic_read(&mm->mm_users) <= 0)) |
| 933 | return -EINVAL; |
| 934 | |
| 935 | /* pairs with mmdrop in mmu_interval_notifier_remove() */ |
| 936 | mmgrab(mm); |
| 937 | |
| 938 | /* |
| 939 | * If some invalidate_range_start/end region is going on in parallel |
| 940 | * we don't know what VA ranges are affected, so we must assume this |
| 941 | * new range is included. |
| 942 | * |
| 943 | * If the itree is invalidating then we are not allowed to change |
| 944 | * it. Retrying until invalidation is done is tricky due to the |
| 945 | * possibility for live lock, instead defer the add to |
| 946 | * mn_itree_inv_end() so this algorithm is deterministic. |
| 947 | * |
| 948 | * In all cases the value for the interval_sub->invalidate_seq should be |
| 949 | * odd, see mmu_interval_read_begin() |
| 950 | */ |
| 951 | spin_lock(&subscriptions->lock); |
| 952 | if (subscriptions->active_invalidate_ranges) { |
| 953 | if (mn_itree_is_invalidating(subscriptions)) |
| 954 | hlist_add_head(&interval_sub->deferred_item, |
| 955 | &subscriptions->deferred_list); |
| 956 | else { |
| 957 | subscriptions->invalidate_seq |= 1; |
| 958 | interval_tree_insert(&interval_sub->interval_tree, |
| 959 | &subscriptions->itree); |
| 960 | } |
| 961 | interval_sub->invalidate_seq = subscriptions->invalidate_seq; |
| 962 | } else { |
| 963 | WARN_ON(mn_itree_is_invalidating(subscriptions)); |
| 964 | /* |
| 965 | * The starting seq for a subscription not under invalidation |
| 966 | * should be odd, not equal to the current invalidate_seq and |
| 967 | * invalidate_seq should not 'wrap' to the new seq any time |
| 968 | * soon. |
| 969 | */ |
| 970 | interval_sub->invalidate_seq = |
| 971 | subscriptions->invalidate_seq - 1; |
| 972 | interval_tree_insert(&interval_sub->interval_tree, |
| 973 | &subscriptions->itree); |
| 974 | } |
| 975 | spin_unlock(&subscriptions->lock); |
| 976 | return 0; |
| 977 | } |
| 978 | |
| 979 | /** |
| 980 | * mmu_interval_notifier_insert - Insert an interval notifier |
| 981 | * @interval_sub: Interval subscription to register |
| 982 | * @start: Starting virtual address to monitor |
| 983 | * @length: Length of the range to monitor |
| 984 | * @mm: mm_struct to attach to |
| 985 | * @ops: Interval notifier operations to be called on matching events |
| 986 | * |
| 987 | * This function subscribes the interval notifier for notifications from the |
| 988 | * mm. Upon return the ops related to mmu_interval_notifier will be called |
| 989 | * whenever an event that intersects with the given range occurs. |
| 990 | * |
| 991 | * Upon return the range_notifier may not be present in the interval tree yet. |
| 992 | * The caller must use the normal interval notifier read flow via |
| 993 | * mmu_interval_read_begin() to establish SPTEs for this range. |
| 994 | */ |
| 995 | int mmu_interval_notifier_insert(struct mmu_interval_notifier *interval_sub, |
| 996 | struct mm_struct *mm, unsigned long start, |
| 997 | unsigned long length, |
| 998 | const struct mmu_interval_notifier_ops *ops) |
| 999 | { |
| 1000 | struct mmu_notifier_subscriptions *subscriptions; |
| 1001 | int ret; |
| 1002 | |
| 1003 | might_lock(&mm->mmap_lock); |
| 1004 | |
| 1005 | subscriptions = smp_load_acquire(&mm->notifier_subscriptions); |
| 1006 | if (!subscriptions || !subscriptions->has_itree) { |
| 1007 | ret = mmu_notifier_register(NULL, mm); |
| 1008 | if (ret) |
| 1009 | return ret; |
| 1010 | subscriptions = mm->notifier_subscriptions; |
| 1011 | } |
| 1012 | return __mmu_interval_notifier_insert(interval_sub, mm, subscriptions, |
| 1013 | start, length, ops); |
| 1014 | } |
| 1015 | EXPORT_SYMBOL_GPL(mmu_interval_notifier_insert); |
| 1016 | |
| 1017 | int mmu_interval_notifier_insert_locked( |
| 1018 | struct mmu_interval_notifier *interval_sub, struct mm_struct *mm, |
| 1019 | unsigned long start, unsigned long length, |
| 1020 | const struct mmu_interval_notifier_ops *ops) |
| 1021 | { |
| 1022 | struct mmu_notifier_subscriptions *subscriptions = |
| 1023 | mm->notifier_subscriptions; |
| 1024 | int ret; |
| 1025 | |
| 1026 | mmap_assert_write_locked(mm); |
| 1027 | |
| 1028 | if (!subscriptions || !subscriptions->has_itree) { |
| 1029 | ret = __mmu_notifier_register(NULL, mm); |
| 1030 | if (ret) |
| 1031 | return ret; |
| 1032 | subscriptions = mm->notifier_subscriptions; |
| 1033 | } |
| 1034 | return __mmu_interval_notifier_insert(interval_sub, mm, subscriptions, |
| 1035 | start, length, ops); |
| 1036 | } |
| 1037 | EXPORT_SYMBOL_GPL(mmu_interval_notifier_insert_locked); |
| 1038 | |
| 1039 | static bool |
| 1040 | mmu_interval_seq_released(struct mmu_notifier_subscriptions *subscriptions, |
| 1041 | unsigned long seq) |
| 1042 | { |
| 1043 | bool ret; |
| 1044 | |
| 1045 | spin_lock(&subscriptions->lock); |
| 1046 | ret = subscriptions->invalidate_seq != seq; |
| 1047 | spin_unlock(&subscriptions->lock); |
| 1048 | return ret; |
| 1049 | } |
| 1050 | |
| 1051 | /** |
| 1052 | * mmu_interval_notifier_remove - Remove a interval notifier |
| 1053 | * @interval_sub: Interval subscription to unregister |
| 1054 | * |
| 1055 | * This function must be paired with mmu_interval_notifier_insert(). It cannot |
| 1056 | * be called from any ops callback. |
| 1057 | * |
| 1058 | * Once this returns ops callbacks are no longer running on other CPUs and |
| 1059 | * will not be called in future. |
| 1060 | */ |
| 1061 | void mmu_interval_notifier_remove(struct mmu_interval_notifier *interval_sub) |
| 1062 | { |
| 1063 | struct mm_struct *mm = interval_sub->mm; |
| 1064 | struct mmu_notifier_subscriptions *subscriptions = |
| 1065 | mm->notifier_subscriptions; |
| 1066 | unsigned long seq = 0; |
| 1067 | |
| 1068 | might_sleep(); |
| 1069 | |
| 1070 | spin_lock(&subscriptions->lock); |
| 1071 | if (mn_itree_is_invalidating(subscriptions)) { |
| 1072 | /* |
| 1073 | * remove is being called after insert put this on the |
| 1074 | * deferred list, but before the deferred list was processed. |
| 1075 | */ |
| 1076 | if (RB_EMPTY_NODE(&interval_sub->interval_tree.rb)) { |
| 1077 | hlist_del(&interval_sub->deferred_item); |
| 1078 | } else { |
| 1079 | hlist_add_head(&interval_sub->deferred_item, |
| 1080 | &subscriptions->deferred_list); |
| 1081 | seq = subscriptions->invalidate_seq; |
| 1082 | } |
| 1083 | } else { |
| 1084 | WARN_ON(RB_EMPTY_NODE(&interval_sub->interval_tree.rb)); |
| 1085 | interval_tree_remove(&interval_sub->interval_tree, |
| 1086 | &subscriptions->itree); |
| 1087 | } |
| 1088 | spin_unlock(&subscriptions->lock); |
| 1089 | |
| 1090 | /* |
| 1091 | * The possible sleep on progress in the invalidation requires the |
| 1092 | * caller not hold any locks held by invalidation callbacks. |
| 1093 | */ |
| 1094 | lock_map_acquire(&__mmu_notifier_invalidate_range_start_map); |
| 1095 | lock_map_release(&__mmu_notifier_invalidate_range_start_map); |
| 1096 | if (seq) |
| 1097 | wait_event(subscriptions->wq, |
| 1098 | mmu_interval_seq_released(subscriptions, seq)); |
| 1099 | |
| 1100 | /* pairs with mmgrab in mmu_interval_notifier_insert() */ |
| 1101 | mmdrop(mm); |
| 1102 | } |
| 1103 | EXPORT_SYMBOL_GPL(mmu_interval_notifier_remove); |
| 1104 | |
| 1105 | /** |
| 1106 | * mmu_notifier_synchronize - Ensure all mmu_notifiers are freed |
| 1107 | * |
| 1108 | * This function ensures that all outstanding async SRU work from |
| 1109 | * mmu_notifier_put() is completed. After it returns any mmu_notifier_ops |
| 1110 | * associated with an unused mmu_notifier will no longer be called. |
| 1111 | * |
| 1112 | * Before using the caller must ensure that all of its mmu_notifiers have been |
| 1113 | * fully released via mmu_notifier_put(). |
| 1114 | * |
| 1115 | * Modules using the mmu_notifier_put() API should call this in their __exit |
| 1116 | * function to avoid module unloading races. |
| 1117 | */ |
| 1118 | void mmu_notifier_synchronize(void) |
| 1119 | { |
| 1120 | synchronize_srcu(&srcu); |
| 1121 | } |
| 1122 | EXPORT_SYMBOL_GPL(mmu_notifier_synchronize); |