2 * linux/mm/mmu_notifier.c
4 * Copyright (C) 2008 Qumranet, Inc.
5 * Copyright (C) 2008 SGI
6 * Christoph Lameter <cl@linux.com>
8 * This work is licensed under the terms of the GNU GPL, version 2. See
9 * the COPYING file in the top-level directory.
12 #include <linux/rculist.h>
13 #include <linux/mmu_notifier.h>
14 #include <linux/export.h>
16 #include <linux/err.h>
17 #include <linux/srcu.h>
18 #include <linux/rcupdate.h>
19 #include <linux/sched.h>
20 #include <linux/sched/mm.h>
21 #include <linux/slab.h>
23 /* global SRCU for all MMs */
24 DEFINE_STATIC_SRCU(srcu);
27 * This function allows mmu_notifier::release callback to delay a call to
28 * a function that will free appropriate resources. The function must be
29 * quick and must not block.
31 void mmu_notifier_call_srcu(struct rcu_head *rcu,
32 void (*func)(struct rcu_head *rcu))
34 call_srcu(&srcu, rcu, func);
36 EXPORT_SYMBOL_GPL(mmu_notifier_call_srcu);
39 * This function can't run concurrently against mmu_notifier_register
40 * because mm->mm_users > 0 during mmu_notifier_register and exit_mmap
41 * runs with mm_users == 0. Other tasks may still invoke mmu notifiers
42 * in parallel despite there being no task using this mm any more,
43 * through the vmas outside of the exit_mmap context, such as with
44 * vmtruncate. This serializes against mmu_notifier_unregister with
45 * the mmu_notifier_mm->lock in addition to SRCU and it serializes
46 * against the other mmu notifiers with SRCU. struct mmu_notifier_mm
47 * can't go away from under us as exit_mmap holds an mm_count pin
50 void __mmu_notifier_release(struct mm_struct *mm)
52 struct mmu_notifier *mn;
56 * SRCU here will block mmu_notifier_unregister until
59 id = srcu_read_lock(&srcu);
60 hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist)
62 * If ->release runs before mmu_notifier_unregister it must be
63 * handled, as it's the only way for the driver to flush all
64 * existing sptes and stop the driver from establishing any more
65 * sptes before all the pages in the mm are freed.
68 mn->ops->release(mn, mm);
70 spin_lock(&mm->mmu_notifier_mm->lock);
71 while (unlikely(!hlist_empty(&mm->mmu_notifier_mm->list))) {
72 mn = hlist_entry(mm->mmu_notifier_mm->list.first,
76 * We arrived before mmu_notifier_unregister so
77 * mmu_notifier_unregister will do nothing other than to wait
78 * for ->release to finish and for mmu_notifier_unregister to
81 hlist_del_init_rcu(&mn->hlist);
83 spin_unlock(&mm->mmu_notifier_mm->lock);
84 srcu_read_unlock(&srcu, id);
87 * synchronize_srcu here prevents mmu_notifier_release from returning to
88 * exit_mmap (which would proceed with freeing all pages in the mm)
89 * until the ->release method returns, if it was invoked by
90 * mmu_notifier_unregister.
92 * The mmu_notifier_mm can't go away from under us because one mm_count
93 * is held by exit_mmap.
95 synchronize_srcu(&srcu);
99 * If no young bitflag is supported by the hardware, ->clear_flush_young can
100 * unmap the address and return 1 or 0 depending if the mapping previously
103 int __mmu_notifier_clear_flush_young(struct mm_struct *mm,
107 struct mmu_notifier *mn;
110 id = srcu_read_lock(&srcu);
111 hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
112 if (mn->ops->clear_flush_young)
113 young |= mn->ops->clear_flush_young(mn, mm, start, end);
115 srcu_read_unlock(&srcu, id);
120 int __mmu_notifier_clear_young(struct mm_struct *mm,
124 struct mmu_notifier *mn;
127 id = srcu_read_lock(&srcu);
128 hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
129 if (mn->ops->clear_young)
130 young |= mn->ops->clear_young(mn, mm, start, end);
132 srcu_read_unlock(&srcu, id);
137 int __mmu_notifier_test_young(struct mm_struct *mm,
138 unsigned long address)
140 struct mmu_notifier *mn;
143 id = srcu_read_lock(&srcu);
144 hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
145 if (mn->ops->test_young) {
146 young = mn->ops->test_young(mn, mm, address);
151 srcu_read_unlock(&srcu, id);
156 void __mmu_notifier_change_pte(struct mm_struct *mm, unsigned long address,
159 struct mmu_notifier *mn;
162 id = srcu_read_lock(&srcu);
163 hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
164 if (mn->ops->change_pte)
165 mn->ops->change_pte(mn, mm, address, pte);
167 srcu_read_unlock(&srcu, id);
170 int __mmu_notifier_invalidate_range_start(struct mm_struct *mm,
171 unsigned long start, unsigned long end,
174 struct mmu_notifier_range _range, *range = &_range;
175 struct mmu_notifier *mn;
179 range->blockable = blockable;
180 range->start = start;
184 id = srcu_read_lock(&srcu);
185 hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
186 if (mn->ops->invalidate_range_start) {
187 int _ret = mn->ops->invalidate_range_start(mn, range);
189 pr_info("%pS callback failed with %d in %sblockable context.\n",
190 mn->ops->invalidate_range_start, _ret,
191 !blockable ? "non-" : "");
196 srcu_read_unlock(&srcu, id);
200 EXPORT_SYMBOL_GPL(__mmu_notifier_invalidate_range_start);
202 void __mmu_notifier_invalidate_range_end(struct mm_struct *mm,
207 struct mmu_notifier_range _range, *range = &_range;
208 struct mmu_notifier *mn;
212 * The end call back will never be call if the start refused to go
213 * through because of blockable was false so here assume that we
216 range->blockable = true;
217 range->start = start;
221 id = srcu_read_lock(&srcu);
222 hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
224 * Call invalidate_range here too to avoid the need for the
225 * subsystem of having to register an invalidate_range_end
226 * call-back when there is invalidate_range already. Usually a
227 * subsystem registers either invalidate_range_start()/end() or
228 * invalidate_range(), so this will be no additional overhead
229 * (besides the pointer check).
231 * We skip call to invalidate_range() if we know it is safe ie
232 * call site use mmu_notifier_invalidate_range_only_end() which
233 * is safe to do when we know that a call to invalidate_range()
234 * already happen under page table lock.
236 if (!only_end && mn->ops->invalidate_range)
237 mn->ops->invalidate_range(mn, mm, start, end);
238 if (mn->ops->invalidate_range_end)
239 mn->ops->invalidate_range_end(mn, range);
241 srcu_read_unlock(&srcu, id);
243 EXPORT_SYMBOL_GPL(__mmu_notifier_invalidate_range_end);
245 void __mmu_notifier_invalidate_range(struct mm_struct *mm,
246 unsigned long start, unsigned long end)
248 struct mmu_notifier *mn;
251 id = srcu_read_lock(&srcu);
252 hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
253 if (mn->ops->invalidate_range)
254 mn->ops->invalidate_range(mn, mm, start, end);
256 srcu_read_unlock(&srcu, id);
258 EXPORT_SYMBOL_GPL(__mmu_notifier_invalidate_range);
260 static int do_mmu_notifier_register(struct mmu_notifier *mn,
261 struct mm_struct *mm,
264 struct mmu_notifier_mm *mmu_notifier_mm;
267 BUG_ON(atomic_read(&mm->mm_users) <= 0);
270 mmu_notifier_mm = kmalloc(sizeof(struct mmu_notifier_mm), GFP_KERNEL);
271 if (unlikely(!mmu_notifier_mm))
275 down_write(&mm->mmap_sem);
276 ret = mm_take_all_locks(mm);
280 if (!mm_has_notifiers(mm)) {
281 INIT_HLIST_HEAD(&mmu_notifier_mm->list);
282 spin_lock_init(&mmu_notifier_mm->lock);
284 mm->mmu_notifier_mm = mmu_notifier_mm;
285 mmu_notifier_mm = NULL;
290 * Serialize the update against mmu_notifier_unregister. A
291 * side note: mmu_notifier_release can't run concurrently with
292 * us because we hold the mm_users pin (either implicitly as
293 * current->mm or explicitly with get_task_mm() or similar).
294 * We can't race against any other mmu notifier method either
295 * thanks to mm_take_all_locks().
297 spin_lock(&mm->mmu_notifier_mm->lock);
298 hlist_add_head(&mn->hlist, &mm->mmu_notifier_mm->list);
299 spin_unlock(&mm->mmu_notifier_mm->lock);
301 mm_drop_all_locks(mm);
304 up_write(&mm->mmap_sem);
305 kfree(mmu_notifier_mm);
307 BUG_ON(atomic_read(&mm->mm_users) <= 0);
312 * Must not hold mmap_sem nor any other VM related lock when calling
313 * this registration function. Must also ensure mm_users can't go down
314 * to zero while this runs to avoid races with mmu_notifier_release,
315 * so mm has to be current->mm or the mm should be pinned safely such
316 * as with get_task_mm(). If the mm is not current->mm, the mm_users
317 * pin should be released by calling mmput after mmu_notifier_register
318 * returns. mmu_notifier_unregister must be always called to
319 * unregister the notifier. mm_count is automatically pinned to allow
320 * mmu_notifier_unregister to safely run at any time later, before or
321 * after exit_mmap. ->release will always be called before exit_mmap
324 int mmu_notifier_register(struct mmu_notifier *mn, struct mm_struct *mm)
326 return do_mmu_notifier_register(mn, mm, 1);
328 EXPORT_SYMBOL_GPL(mmu_notifier_register);
331 * Same as mmu_notifier_register but here the caller must hold the
332 * mmap_sem in write mode.
334 int __mmu_notifier_register(struct mmu_notifier *mn, struct mm_struct *mm)
336 return do_mmu_notifier_register(mn, mm, 0);
338 EXPORT_SYMBOL_GPL(__mmu_notifier_register);
340 /* this is called after the last mmu_notifier_unregister() returned */
341 void __mmu_notifier_mm_destroy(struct mm_struct *mm)
343 BUG_ON(!hlist_empty(&mm->mmu_notifier_mm->list));
344 kfree(mm->mmu_notifier_mm);
345 mm->mmu_notifier_mm = LIST_POISON1; /* debug */
349 * This releases the mm_count pin automatically and frees the mm
350 * structure if it was the last user of it. It serializes against
351 * running mmu notifiers with SRCU and against mmu_notifier_unregister
352 * with the unregister lock + SRCU. All sptes must be dropped before
353 * calling mmu_notifier_unregister. ->release or any other notifier
354 * method may be invoked concurrently with mmu_notifier_unregister,
355 * and only after mmu_notifier_unregister returned we're guaranteed
356 * that ->release or any other method can't run anymore.
358 void mmu_notifier_unregister(struct mmu_notifier *mn, struct mm_struct *mm)
360 BUG_ON(atomic_read(&mm->mm_count) <= 0);
362 if (!hlist_unhashed(&mn->hlist)) {
364 * SRCU here will force exit_mmap to wait for ->release to
365 * finish before freeing the pages.
369 id = srcu_read_lock(&srcu);
371 * exit_mmap will block in mmu_notifier_release to guarantee
372 * that ->release is called before freeing the pages.
374 if (mn->ops->release)
375 mn->ops->release(mn, mm);
376 srcu_read_unlock(&srcu, id);
378 spin_lock(&mm->mmu_notifier_mm->lock);
380 * Can not use list_del_rcu() since __mmu_notifier_release
381 * can delete it before we hold the lock.
383 hlist_del_init_rcu(&mn->hlist);
384 spin_unlock(&mm->mmu_notifier_mm->lock);
388 * Wait for any running method to finish, of course including
389 * ->release if it was run by mmu_notifier_release instead of us.
391 synchronize_srcu(&srcu);
393 BUG_ON(atomic_read(&mm->mm_count) <= 0);
397 EXPORT_SYMBOL_GPL(mmu_notifier_unregister);
400 * Same as mmu_notifier_unregister but no callback and no srcu synchronization.
402 void mmu_notifier_unregister_no_release(struct mmu_notifier *mn,
403 struct mm_struct *mm)
405 spin_lock(&mm->mmu_notifier_mm->lock);
407 * Can not use list_del_rcu() since __mmu_notifier_release
408 * can delete it before we hold the lock.
410 hlist_del_init_rcu(&mn->hlist);
411 spin_unlock(&mm->mmu_notifier_mm->lock);
413 BUG_ON(atomic_read(&mm->mm_count) <= 0);
416 EXPORT_SYMBOL_GPL(mmu_notifier_unregister_no_release);