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1/*
2 * linux/mm/mmu_notifier.c
3 *
4 * Copyright (C) 2008 Qumranet, Inc.
5 * Copyright (C) 2008 SGI
6 * Christoph Lameter <cl@linux.com>
7 *
8 * This work is licensed under the terms of the GNU GPL, version 2. See
9 * the COPYING file in the top-level directory.
10 */
11
12#include <linux/rculist.h>
13#include <linux/mmu_notifier.h>
14#include <linux/export.h>
15#include <linux/mm.h>
16#include <linux/err.h>
17#include <linux/srcu.h>
18#include <linux/rcupdate.h>
19#include <linux/sched.h>
20#include <linux/slab.h>
21
22/* global SRCU for all MMs */
23static struct srcu_struct srcu;
24
25/*
26 * This function allows mmu_notifier::release callback to delay a call to
27 * a function that will free appropriate resources. The function must be
28 * quick and must not block.
29 */
30void mmu_notifier_call_srcu(struct rcu_head *rcu,
31 void (*func)(struct rcu_head *rcu))
32{
33 call_srcu(&srcu, rcu, func);
34}
35EXPORT_SYMBOL_GPL(mmu_notifier_call_srcu);
36
37void mmu_notifier_synchronize(void)
38{
39 /* Wait for any running method to finish. */
40 srcu_barrier(&srcu);
41}
42EXPORT_SYMBOL_GPL(mmu_notifier_synchronize);
43
44/*
45 * This function can't run concurrently against mmu_notifier_register
46 * because mm->mm_users > 0 during mmu_notifier_register and exit_mmap
47 * runs with mm_users == 0. Other tasks may still invoke mmu notifiers
48 * in parallel despite there being no task using this mm any more,
49 * through the vmas outside of the exit_mmap context, such as with
50 * vmtruncate. This serializes against mmu_notifier_unregister with
51 * the mmu_notifier_mm->lock in addition to SRCU and it serializes
52 * against the other mmu notifiers with SRCU. struct mmu_notifier_mm
53 * can't go away from under us as exit_mmap holds an mm_count pin
54 * itself.
55 */
56void __mmu_notifier_release(struct mm_struct *mm)
57{
58 struct mmu_notifier *mn;
59 int id;
60
61 /*
62 * SRCU here will block mmu_notifier_unregister until
63 * ->release returns.
64 */
65 id = srcu_read_lock(&srcu);
66 hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist)
67 /*
68 * If ->release runs before mmu_notifier_unregister it must be
69 * handled, as it's the only way for the driver to flush all
70 * existing sptes and stop the driver from establishing any more
71 * sptes before all the pages in the mm are freed.
72 */
73 if (mn->ops->release)
74 mn->ops->release(mn, mm);
75
76 spin_lock(&mm->mmu_notifier_mm->lock);
77 while (unlikely(!hlist_empty(&mm->mmu_notifier_mm->list))) {
78 mn = hlist_entry(mm->mmu_notifier_mm->list.first,
79 struct mmu_notifier,
80 hlist);
81 /*
82 * We arrived before mmu_notifier_unregister so
83 * mmu_notifier_unregister will do nothing other than to wait
84 * for ->release to finish and for mmu_notifier_unregister to
85 * return.
86 */
87 hlist_del_init_rcu(&mn->hlist);
88 }
89 spin_unlock(&mm->mmu_notifier_mm->lock);
90 srcu_read_unlock(&srcu, id);
91
92 /*
93 * synchronize_srcu here prevents mmu_notifier_release from returning to
94 * exit_mmap (which would proceed with freeing all pages in the mm)
95 * until the ->release method returns, if it was invoked by
96 * mmu_notifier_unregister.
97 *
98 * The mmu_notifier_mm can't go away from under us because one mm_count
99 * is held by exit_mmap.
100 */
101 synchronize_srcu(&srcu);
102}
103
104/*
105 * If no young bitflag is supported by the hardware, ->clear_flush_young can
106 * unmap the address and return 1 or 0 depending if the mapping previously
107 * existed or not.
108 */
109int __mmu_notifier_clear_flush_young(struct mm_struct *mm,
110 unsigned long start,
111 unsigned long end)
112{
113 struct mmu_notifier *mn;
114 int young = 0, id;
115
116 id = srcu_read_lock(&srcu);
117 hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
118 if (mn->ops->clear_flush_young)
119 young |= mn->ops->clear_flush_young(mn, mm, start, end);
120 }
121 srcu_read_unlock(&srcu, id);
122
123 return young;
124}
125
126int __mmu_notifier_clear_young(struct mm_struct *mm,
127 unsigned long start,
128 unsigned long end)
129{
130 struct mmu_notifier *mn;
131 int young = 0, id;
132
133 id = srcu_read_lock(&srcu);
134 hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
135 if (mn->ops->clear_young)
136 young |= mn->ops->clear_young(mn, mm, start, end);
137 }
138 srcu_read_unlock(&srcu, id);
139
140 return young;
141}
142
143int __mmu_notifier_test_young(struct mm_struct *mm,
144 unsigned long address)
145{
146 struct mmu_notifier *mn;
147 int young = 0, id;
148
149 id = srcu_read_lock(&srcu);
150 hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
151 if (mn->ops->test_young) {
152 young = mn->ops->test_young(mn, mm, address);
153 if (young)
154 break;
155 }
156 }
157 srcu_read_unlock(&srcu, id);
158
159 return young;
160}
161
162void __mmu_notifier_change_pte(struct mm_struct *mm, unsigned long address,
163 pte_t pte)
164{
165 struct mmu_notifier *mn;
166 int id;
167
168 id = srcu_read_lock(&srcu);
169 hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
170 if (mn->ops->change_pte)
171 mn->ops->change_pte(mn, mm, address, pte);
172 }
173 srcu_read_unlock(&srcu, id);
174}
175
176void __mmu_notifier_invalidate_page(struct mm_struct *mm,
177 unsigned long address)
178{
179 struct mmu_notifier *mn;
180 int id;
181
182 id = srcu_read_lock(&srcu);
183 hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
184 if (mn->ops->invalidate_page)
185 mn->ops->invalidate_page(mn, mm, address);
186 }
187 srcu_read_unlock(&srcu, id);
188}
189
190void __mmu_notifier_invalidate_range_start(struct mm_struct *mm,
191 unsigned long start, unsigned long end)
192{
193 struct mmu_notifier *mn;
194 int id;
195
196 id = srcu_read_lock(&srcu);
197 hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
198 if (mn->ops->invalidate_range_start)
199 mn->ops->invalidate_range_start(mn, mm, start, end);
200 }
201 srcu_read_unlock(&srcu, id);
202}
203EXPORT_SYMBOL_GPL(__mmu_notifier_invalidate_range_start);
204
205void __mmu_notifier_invalidate_range_end(struct mm_struct *mm,
206 unsigned long start, unsigned long end)
207{
208 struct mmu_notifier *mn;
209 int id;
210
211 id = srcu_read_lock(&srcu);
212 hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
213 /*
214 * Call invalidate_range here too to avoid the need for the
215 * subsystem of having to register an invalidate_range_end
216 * call-back when there is invalidate_range already. Usually a
217 * subsystem registers either invalidate_range_start()/end() or
218 * invalidate_range(), so this will be no additional overhead
219 * (besides the pointer check).
220 */
221 if (mn->ops->invalidate_range)
222 mn->ops->invalidate_range(mn, mm, start, end);
223 if (mn->ops->invalidate_range_end)
224 mn->ops->invalidate_range_end(mn, mm, start, end);
225 }
226 srcu_read_unlock(&srcu, id);
227}
228EXPORT_SYMBOL_GPL(__mmu_notifier_invalidate_range_end);
229
230void __mmu_notifier_invalidate_range(struct mm_struct *mm,
231 unsigned long start, unsigned long end)
232{
233 struct mmu_notifier *mn;
234 int id;
235
236 id = srcu_read_lock(&srcu);
237 hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
238 if (mn->ops->invalidate_range)
239 mn->ops->invalidate_range(mn, mm, start, end);
240 }
241 srcu_read_unlock(&srcu, id);
242}
243EXPORT_SYMBOL_GPL(__mmu_notifier_invalidate_range);
244
245static int do_mmu_notifier_register(struct mmu_notifier *mn,
246 struct mm_struct *mm,
247 int take_mmap_sem)
248{
249 struct mmu_notifier_mm *mmu_notifier_mm;
250 int ret;
251
252 BUG_ON(atomic_read(&mm->mm_users) <= 0);
253
254 /*
255 * Verify that mmu_notifier_init() already run and the global srcu is
256 * initialized.
257 */
258 BUG_ON(!srcu.per_cpu_ref);
259
260 ret = -ENOMEM;
261 mmu_notifier_mm = kmalloc(sizeof(struct mmu_notifier_mm), GFP_KERNEL);
262 if (unlikely(!mmu_notifier_mm))
263 goto out;
264
265 if (take_mmap_sem)
266 down_write(&mm->mmap_sem);
267 ret = mm_take_all_locks(mm);
268 if (unlikely(ret))
269 goto out_clean;
270
271 if (!mm_has_notifiers(mm)) {
272 INIT_HLIST_HEAD(&mmu_notifier_mm->list);
273 spin_lock_init(&mmu_notifier_mm->lock);
274
275 mm->mmu_notifier_mm = mmu_notifier_mm;
276 mmu_notifier_mm = NULL;
277 }
278 atomic_inc(&mm->mm_count);
279
280 /*
281 * Serialize the update against mmu_notifier_unregister. A
282 * side note: mmu_notifier_release can't run concurrently with
283 * us because we hold the mm_users pin (either implicitly as
284 * current->mm or explicitly with get_task_mm() or similar).
285 * We can't race against any other mmu notifier method either
286 * thanks to mm_take_all_locks().
287 */
288 spin_lock(&mm->mmu_notifier_mm->lock);
289 hlist_add_head(&mn->hlist, &mm->mmu_notifier_mm->list);
290 spin_unlock(&mm->mmu_notifier_mm->lock);
291
292 mm_drop_all_locks(mm);
293out_clean:
294 if (take_mmap_sem)
295 up_write(&mm->mmap_sem);
296 kfree(mmu_notifier_mm);
297out:
298 BUG_ON(atomic_read(&mm->mm_users) <= 0);
299 return ret;
300}
301
302/*
303 * Must not hold mmap_sem nor any other VM related lock when calling
304 * this registration function. Must also ensure mm_users can't go down
305 * to zero while this runs to avoid races with mmu_notifier_release,
306 * so mm has to be current->mm or the mm should be pinned safely such
307 * as with get_task_mm(). If the mm is not current->mm, the mm_users
308 * pin should be released by calling mmput after mmu_notifier_register
309 * returns. mmu_notifier_unregister must be always called to
310 * unregister the notifier. mm_count is automatically pinned to allow
311 * mmu_notifier_unregister to safely run at any time later, before or
312 * after exit_mmap. ->release will always be called before exit_mmap
313 * frees the pages.
314 */
315int mmu_notifier_register(struct mmu_notifier *mn, struct mm_struct *mm)
316{
317 return do_mmu_notifier_register(mn, mm, 1);
318}
319EXPORT_SYMBOL_GPL(mmu_notifier_register);
320
321/*
322 * Same as mmu_notifier_register but here the caller must hold the
323 * mmap_sem in write mode.
324 */
325int __mmu_notifier_register(struct mmu_notifier *mn, struct mm_struct *mm)
326{
327 return do_mmu_notifier_register(mn, mm, 0);
328}
329EXPORT_SYMBOL_GPL(__mmu_notifier_register);
330
331/* this is called after the last mmu_notifier_unregister() returned */
332void __mmu_notifier_mm_destroy(struct mm_struct *mm)
333{
334 BUG_ON(!hlist_empty(&mm->mmu_notifier_mm->list));
335 kfree(mm->mmu_notifier_mm);
336 mm->mmu_notifier_mm = LIST_POISON1; /* debug */
337}
338
339/*
340 * This releases the mm_count pin automatically and frees the mm
341 * structure if it was the last user of it. It serializes against
342 * running mmu notifiers with SRCU and against mmu_notifier_unregister
343 * with the unregister lock + SRCU. All sptes must be dropped before
344 * calling mmu_notifier_unregister. ->release or any other notifier
345 * method may be invoked concurrently with mmu_notifier_unregister,
346 * and only after mmu_notifier_unregister returned we're guaranteed
347 * that ->release or any other method can't run anymore.
348 */
349void mmu_notifier_unregister(struct mmu_notifier *mn, struct mm_struct *mm)
350{
351 BUG_ON(atomic_read(&mm->mm_count) <= 0);
352
353 if (!hlist_unhashed(&mn->hlist)) {
354 /*
355 * SRCU here will force exit_mmap to wait for ->release to
356 * finish before freeing the pages.
357 */
358 int id;
359
360 id = srcu_read_lock(&srcu);
361 /*
362 * exit_mmap will block in mmu_notifier_release to guarantee
363 * that ->release is called before freeing the pages.
364 */
365 if (mn->ops->release)
366 mn->ops->release(mn, mm);
367 srcu_read_unlock(&srcu, id);
368
369 spin_lock(&mm->mmu_notifier_mm->lock);
370 /*
371 * Can not use list_del_rcu() since __mmu_notifier_release
372 * can delete it before we hold the lock.
373 */
374 hlist_del_init_rcu(&mn->hlist);
375 spin_unlock(&mm->mmu_notifier_mm->lock);
376 }
377
378 /*
379 * Wait for any running method to finish, of course including
380 * ->release if it was run by mmu_notifier_release instead of us.
381 */
382 synchronize_srcu(&srcu);
383
384 BUG_ON(atomic_read(&mm->mm_count) <= 0);
385
386 mmdrop(mm);
387}
388EXPORT_SYMBOL_GPL(mmu_notifier_unregister);
389
390/*
391 * Same as mmu_notifier_unregister but no callback and no srcu synchronization.
392 */
393void mmu_notifier_unregister_no_release(struct mmu_notifier *mn,
394 struct mm_struct *mm)
395{
396 spin_lock(&mm->mmu_notifier_mm->lock);
397 /*
398 * Can not use list_del_rcu() since __mmu_notifier_release
399 * can delete it before we hold the lock.
400 */
401 hlist_del_init_rcu(&mn->hlist);
402 spin_unlock(&mm->mmu_notifier_mm->lock);
403
404 BUG_ON(atomic_read(&mm->mm_count) <= 0);
405 mmdrop(mm);
406}
407EXPORT_SYMBOL_GPL(mmu_notifier_unregister_no_release);
408
409static int __init mmu_notifier_init(void)
410{
411 return init_srcu_struct(&srcu);
412}
413subsys_initcall(mmu_notifier_init);
1/*
2 * linux/mm/mmu_notifier.c
3 *
4 * Copyright (C) 2008 Qumranet, Inc.
5 * Copyright (C) 2008 SGI
6 * Christoph Lameter <cl@linux.com>
7 *
8 * This work is licensed under the terms of the GNU GPL, version 2. See
9 * the COPYING file in the top-level directory.
10 */
11
12#include <linux/rculist.h>
13#include <linux/mmu_notifier.h>
14#include <linux/export.h>
15#include <linux/mm.h>
16#include <linux/err.h>
17#include <linux/srcu.h>
18#include <linux/rcupdate.h>
19#include <linux/sched.h>
20#include <linux/slab.h>
21
22/* global SRCU for all MMs */
23static struct srcu_struct srcu;
24
25/*
26 * This function allows mmu_notifier::release callback to delay a call to
27 * a function that will free appropriate resources. The function must be
28 * quick and must not block.
29 */
30void mmu_notifier_call_srcu(struct rcu_head *rcu,
31 void (*func)(struct rcu_head *rcu))
32{
33 call_srcu(&srcu, rcu, func);
34}
35EXPORT_SYMBOL_GPL(mmu_notifier_call_srcu);
36
37void mmu_notifier_synchronize(void)
38{
39 /* Wait for any running method to finish. */
40 srcu_barrier(&srcu);
41}
42EXPORT_SYMBOL_GPL(mmu_notifier_synchronize);
43
44/*
45 * This function can't run concurrently against mmu_notifier_register
46 * because mm->mm_users > 0 during mmu_notifier_register and exit_mmap
47 * runs with mm_users == 0. Other tasks may still invoke mmu notifiers
48 * in parallel despite there being no task using this mm any more,
49 * through the vmas outside of the exit_mmap context, such as with
50 * vmtruncate. This serializes against mmu_notifier_unregister with
51 * the mmu_notifier_mm->lock in addition to SRCU and it serializes
52 * against the other mmu notifiers with SRCU. struct mmu_notifier_mm
53 * can't go away from under us as exit_mmap holds an mm_count pin
54 * itself.
55 */
56void __mmu_notifier_release(struct mm_struct *mm)
57{
58 struct mmu_notifier *mn;
59 int id;
60
61 /*
62 * SRCU here will block mmu_notifier_unregister until
63 * ->release returns.
64 */
65 id = srcu_read_lock(&srcu);
66 hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist)
67 /*
68 * If ->release runs before mmu_notifier_unregister it must be
69 * handled, as it's the only way for the driver to flush all
70 * existing sptes and stop the driver from establishing any more
71 * sptes before all the pages in the mm are freed.
72 */
73 if (mn->ops->release)
74 mn->ops->release(mn, mm);
75
76 spin_lock(&mm->mmu_notifier_mm->lock);
77 while (unlikely(!hlist_empty(&mm->mmu_notifier_mm->list))) {
78 mn = hlist_entry(mm->mmu_notifier_mm->list.first,
79 struct mmu_notifier,
80 hlist);
81 /*
82 * We arrived before mmu_notifier_unregister so
83 * mmu_notifier_unregister will do nothing other than to wait
84 * for ->release to finish and for mmu_notifier_unregister to
85 * return.
86 */
87 hlist_del_init_rcu(&mn->hlist);
88 }
89 spin_unlock(&mm->mmu_notifier_mm->lock);
90 srcu_read_unlock(&srcu, id);
91
92 /*
93 * synchronize_srcu here prevents mmu_notifier_release from returning to
94 * exit_mmap (which would proceed with freeing all pages in the mm)
95 * until the ->release method returns, if it was invoked by
96 * mmu_notifier_unregister.
97 *
98 * The mmu_notifier_mm can't go away from under us because one mm_count
99 * is held by exit_mmap.
100 */
101 synchronize_srcu(&srcu);
102}
103
104/*
105 * If no young bitflag is supported by the hardware, ->clear_flush_young can
106 * unmap the address and return 1 or 0 depending if the mapping previously
107 * existed or not.
108 */
109int __mmu_notifier_clear_flush_young(struct mm_struct *mm,
110 unsigned long start,
111 unsigned long end)
112{
113 struct mmu_notifier *mn;
114 int young = 0, id;
115
116 id = srcu_read_lock(&srcu);
117 hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
118 if (mn->ops->clear_flush_young)
119 young |= mn->ops->clear_flush_young(mn, mm, start, end);
120 }
121 srcu_read_unlock(&srcu, id);
122
123 return young;
124}
125
126int __mmu_notifier_clear_young(struct mm_struct *mm,
127 unsigned long start,
128 unsigned long end)
129{
130 struct mmu_notifier *mn;
131 int young = 0, id;
132
133 id = srcu_read_lock(&srcu);
134 hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
135 if (mn->ops->clear_young)
136 young |= mn->ops->clear_young(mn, mm, start, end);
137 }
138 srcu_read_unlock(&srcu, id);
139
140 return young;
141}
142
143int __mmu_notifier_test_young(struct mm_struct *mm,
144 unsigned long address)
145{
146 struct mmu_notifier *mn;
147 int young = 0, id;
148
149 id = srcu_read_lock(&srcu);
150 hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
151 if (mn->ops->test_young) {
152 young = mn->ops->test_young(mn, mm, address);
153 if (young)
154 break;
155 }
156 }
157 srcu_read_unlock(&srcu, id);
158
159 return young;
160}
161
162void __mmu_notifier_change_pte(struct mm_struct *mm, unsigned long address,
163 pte_t pte)
164{
165 struct mmu_notifier *mn;
166 int id;
167
168 id = srcu_read_lock(&srcu);
169 hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
170 if (mn->ops->change_pte)
171 mn->ops->change_pte(mn, mm, address, pte);
172 }
173 srcu_read_unlock(&srcu, id);
174}
175
176void __mmu_notifier_invalidate_page(struct mm_struct *mm,
177 unsigned long address)
178{
179 struct mmu_notifier *mn;
180 int id;
181
182 id = srcu_read_lock(&srcu);
183 hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
184 if (mn->ops->invalidate_page)
185 mn->ops->invalidate_page(mn, mm, address);
186 }
187 srcu_read_unlock(&srcu, id);
188}
189
190void __mmu_notifier_invalidate_range_start(struct mm_struct *mm,
191 unsigned long start, unsigned long end)
192{
193 struct mmu_notifier *mn;
194 int id;
195
196 id = srcu_read_lock(&srcu);
197 hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
198 if (mn->ops->invalidate_range_start)
199 mn->ops->invalidate_range_start(mn, mm, start, end);
200 }
201 srcu_read_unlock(&srcu, id);
202}
203EXPORT_SYMBOL_GPL(__mmu_notifier_invalidate_range_start);
204
205void __mmu_notifier_invalidate_range_end(struct mm_struct *mm,
206 unsigned long start, unsigned long end)
207{
208 struct mmu_notifier *mn;
209 int id;
210
211 id = srcu_read_lock(&srcu);
212 hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
213 /*
214 * Call invalidate_range here too to avoid the need for the
215 * subsystem of having to register an invalidate_range_end
216 * call-back when there is invalidate_range already. Usually a
217 * subsystem registers either invalidate_range_start()/end() or
218 * invalidate_range(), so this will be no additional overhead
219 * (besides the pointer check).
220 */
221 if (mn->ops->invalidate_range)
222 mn->ops->invalidate_range(mn, mm, start, end);
223 if (mn->ops->invalidate_range_end)
224 mn->ops->invalidate_range_end(mn, mm, start, end);
225 }
226 srcu_read_unlock(&srcu, id);
227}
228EXPORT_SYMBOL_GPL(__mmu_notifier_invalidate_range_end);
229
230void __mmu_notifier_invalidate_range(struct mm_struct *mm,
231 unsigned long start, unsigned long end)
232{
233 struct mmu_notifier *mn;
234 int id;
235
236 id = srcu_read_lock(&srcu);
237 hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
238 if (mn->ops->invalidate_range)
239 mn->ops->invalidate_range(mn, mm, start, end);
240 }
241 srcu_read_unlock(&srcu, id);
242}
243EXPORT_SYMBOL_GPL(__mmu_notifier_invalidate_range);
244
245static int do_mmu_notifier_register(struct mmu_notifier *mn,
246 struct mm_struct *mm,
247 int take_mmap_sem)
248{
249 struct mmu_notifier_mm *mmu_notifier_mm;
250 int ret;
251
252 BUG_ON(atomic_read(&mm->mm_users) <= 0);
253
254 /*
255 * Verify that mmu_notifier_init() already run and the global srcu is
256 * initialized.
257 */
258 BUG_ON(!srcu.per_cpu_ref);
259
260 ret = -ENOMEM;
261 mmu_notifier_mm = kmalloc(sizeof(struct mmu_notifier_mm), GFP_KERNEL);
262 if (unlikely(!mmu_notifier_mm))
263 goto out;
264
265 if (take_mmap_sem)
266 down_write(&mm->mmap_sem);
267 ret = mm_take_all_locks(mm);
268 if (unlikely(ret))
269 goto out_clean;
270
271 if (!mm_has_notifiers(mm)) {
272 INIT_HLIST_HEAD(&mmu_notifier_mm->list);
273 spin_lock_init(&mmu_notifier_mm->lock);
274
275 mm->mmu_notifier_mm = mmu_notifier_mm;
276 mmu_notifier_mm = NULL;
277 }
278 atomic_inc(&mm->mm_count);
279
280 /*
281 * Serialize the update against mmu_notifier_unregister. A
282 * side note: mmu_notifier_release can't run concurrently with
283 * us because we hold the mm_users pin (either implicitly as
284 * current->mm or explicitly with get_task_mm() or similar).
285 * We can't race against any other mmu notifier method either
286 * thanks to mm_take_all_locks().
287 */
288 spin_lock(&mm->mmu_notifier_mm->lock);
289 hlist_add_head(&mn->hlist, &mm->mmu_notifier_mm->list);
290 spin_unlock(&mm->mmu_notifier_mm->lock);
291
292 mm_drop_all_locks(mm);
293out_clean:
294 if (take_mmap_sem)
295 up_write(&mm->mmap_sem);
296 kfree(mmu_notifier_mm);
297out:
298 BUG_ON(atomic_read(&mm->mm_users) <= 0);
299 return ret;
300}
301
302/*
303 * Must not hold mmap_sem nor any other VM related lock when calling
304 * this registration function. Must also ensure mm_users can't go down
305 * to zero while this runs to avoid races with mmu_notifier_release,
306 * so mm has to be current->mm or the mm should be pinned safely such
307 * as with get_task_mm(). If the mm is not current->mm, the mm_users
308 * pin should be released by calling mmput after mmu_notifier_register
309 * returns. mmu_notifier_unregister must be always called to
310 * unregister the notifier. mm_count is automatically pinned to allow
311 * mmu_notifier_unregister to safely run at any time later, before or
312 * after exit_mmap. ->release will always be called before exit_mmap
313 * frees the pages.
314 */
315int mmu_notifier_register(struct mmu_notifier *mn, struct mm_struct *mm)
316{
317 return do_mmu_notifier_register(mn, mm, 1);
318}
319EXPORT_SYMBOL_GPL(mmu_notifier_register);
320
321/*
322 * Same as mmu_notifier_register but here the caller must hold the
323 * mmap_sem in write mode.
324 */
325int __mmu_notifier_register(struct mmu_notifier *mn, struct mm_struct *mm)
326{
327 return do_mmu_notifier_register(mn, mm, 0);
328}
329EXPORT_SYMBOL_GPL(__mmu_notifier_register);
330
331/* this is called after the last mmu_notifier_unregister() returned */
332void __mmu_notifier_mm_destroy(struct mm_struct *mm)
333{
334 BUG_ON(!hlist_empty(&mm->mmu_notifier_mm->list));
335 kfree(mm->mmu_notifier_mm);
336 mm->mmu_notifier_mm = LIST_POISON1; /* debug */
337}
338
339/*
340 * This releases the mm_count pin automatically and frees the mm
341 * structure if it was the last user of it. It serializes against
342 * running mmu notifiers with SRCU and against mmu_notifier_unregister
343 * with the unregister lock + SRCU. All sptes must be dropped before
344 * calling mmu_notifier_unregister. ->release or any other notifier
345 * method may be invoked concurrently with mmu_notifier_unregister,
346 * and only after mmu_notifier_unregister returned we're guaranteed
347 * that ->release or any other method can't run anymore.
348 */
349void mmu_notifier_unregister(struct mmu_notifier *mn, struct mm_struct *mm)
350{
351 BUG_ON(atomic_read(&mm->mm_count) <= 0);
352
353 if (!hlist_unhashed(&mn->hlist)) {
354 /*
355 * SRCU here will force exit_mmap to wait for ->release to
356 * finish before freeing the pages.
357 */
358 int id;
359
360 id = srcu_read_lock(&srcu);
361 /*
362 * exit_mmap will block in mmu_notifier_release to guarantee
363 * that ->release is called before freeing the pages.
364 */
365 if (mn->ops->release)
366 mn->ops->release(mn, mm);
367 srcu_read_unlock(&srcu, id);
368
369 spin_lock(&mm->mmu_notifier_mm->lock);
370 /*
371 * Can not use list_del_rcu() since __mmu_notifier_release
372 * can delete it before we hold the lock.
373 */
374 hlist_del_init_rcu(&mn->hlist);
375 spin_unlock(&mm->mmu_notifier_mm->lock);
376 }
377
378 /*
379 * Wait for any running method to finish, of course including
380 * ->release if it was run by mmu_notifier_release instead of us.
381 */
382 synchronize_srcu(&srcu);
383
384 BUG_ON(atomic_read(&mm->mm_count) <= 0);
385
386 mmdrop(mm);
387}
388EXPORT_SYMBOL_GPL(mmu_notifier_unregister);
389
390/*
391 * Same as mmu_notifier_unregister but no callback and no srcu synchronization.
392 */
393void mmu_notifier_unregister_no_release(struct mmu_notifier *mn,
394 struct mm_struct *mm)
395{
396 spin_lock(&mm->mmu_notifier_mm->lock);
397 /*
398 * Can not use list_del_rcu() since __mmu_notifier_release
399 * can delete it before we hold the lock.
400 */
401 hlist_del_init_rcu(&mn->hlist);
402 spin_unlock(&mm->mmu_notifier_mm->lock);
403
404 BUG_ON(atomic_read(&mm->mm_count) <= 0);
405 mmdrop(mm);
406}
407EXPORT_SYMBOL_GPL(mmu_notifier_unregister_no_release);
408
409static int __init mmu_notifier_init(void)
410{
411 return init_srcu_struct(&srcu);
412}
413subsys_initcall(mmu_notifier_init);