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 mmu_notifier_range
*range
)
172 struct mmu_notifier
*mn
;
176 id
= srcu_read_lock(&srcu
);
177 hlist_for_each_entry_rcu(mn
, &range
->mm
->mmu_notifier_mm
->list
, hlist
) {
178 if (mn
->ops
->invalidate_range_start
) {
179 int _ret
= mn
->ops
->invalidate_range_start(mn
, range
);
181 pr_info("%pS callback failed with %d in %sblockable context.\n",
182 mn
->ops
->invalidate_range_start
, _ret
,
183 !range
->blockable
? "non-" : "");
188 srcu_read_unlock(&srcu
, id
);
192 EXPORT_SYMBOL_GPL(__mmu_notifier_invalidate_range_start
);
194 void __mmu_notifier_invalidate_range_end(struct mmu_notifier_range
*range
,
197 struct mmu_notifier
*mn
;
200 id
= srcu_read_lock(&srcu
);
201 hlist_for_each_entry_rcu(mn
, &range
->mm
->mmu_notifier_mm
->list
, hlist
) {
203 * Call invalidate_range here too to avoid the need for the
204 * subsystem of having to register an invalidate_range_end
205 * call-back when there is invalidate_range already. Usually a
206 * subsystem registers either invalidate_range_start()/end() or
207 * invalidate_range(), so this will be no additional overhead
208 * (besides the pointer check).
210 * We skip call to invalidate_range() if we know it is safe ie
211 * call site use mmu_notifier_invalidate_range_only_end() which
212 * is safe to do when we know that a call to invalidate_range()
213 * already happen under page table lock.
215 if (!only_end
&& mn
->ops
->invalidate_range
)
216 mn
->ops
->invalidate_range(mn
, range
->mm
,
219 if (mn
->ops
->invalidate_range_end
)
220 mn
->ops
->invalidate_range_end(mn
, range
);
222 srcu_read_unlock(&srcu
, id
);
224 EXPORT_SYMBOL_GPL(__mmu_notifier_invalidate_range_end
);
226 void __mmu_notifier_invalidate_range(struct mm_struct
*mm
,
227 unsigned long start
, unsigned long end
)
229 struct mmu_notifier
*mn
;
232 id
= srcu_read_lock(&srcu
);
233 hlist_for_each_entry_rcu(mn
, &mm
->mmu_notifier_mm
->list
, hlist
) {
234 if (mn
->ops
->invalidate_range
)
235 mn
->ops
->invalidate_range(mn
, mm
, start
, end
);
237 srcu_read_unlock(&srcu
, id
);
239 EXPORT_SYMBOL_GPL(__mmu_notifier_invalidate_range
);
241 static int do_mmu_notifier_register(struct mmu_notifier
*mn
,
242 struct mm_struct
*mm
,
245 struct mmu_notifier_mm
*mmu_notifier_mm
;
248 BUG_ON(atomic_read(&mm
->mm_users
) <= 0);
251 mmu_notifier_mm
= kmalloc(sizeof(struct mmu_notifier_mm
), GFP_KERNEL
);
252 if (unlikely(!mmu_notifier_mm
))
256 down_write(&mm
->mmap_sem
);
257 ret
= mm_take_all_locks(mm
);
261 if (!mm_has_notifiers(mm
)) {
262 INIT_HLIST_HEAD(&mmu_notifier_mm
->list
);
263 spin_lock_init(&mmu_notifier_mm
->lock
);
265 mm
->mmu_notifier_mm
= mmu_notifier_mm
;
266 mmu_notifier_mm
= NULL
;
271 * Serialize the update against mmu_notifier_unregister. A
272 * side note: mmu_notifier_release can't run concurrently with
273 * us because we hold the mm_users pin (either implicitly as
274 * current->mm or explicitly with get_task_mm() or similar).
275 * We can't race against any other mmu notifier method either
276 * thanks to mm_take_all_locks().
278 spin_lock(&mm
->mmu_notifier_mm
->lock
);
279 hlist_add_head(&mn
->hlist
, &mm
->mmu_notifier_mm
->list
);
280 spin_unlock(&mm
->mmu_notifier_mm
->lock
);
282 mm_drop_all_locks(mm
);
285 up_write(&mm
->mmap_sem
);
286 kfree(mmu_notifier_mm
);
288 BUG_ON(atomic_read(&mm
->mm_users
) <= 0);
293 * Must not hold mmap_sem nor any other VM related lock when calling
294 * this registration function. Must also ensure mm_users can't go down
295 * to zero while this runs to avoid races with mmu_notifier_release,
296 * so mm has to be current->mm or the mm should be pinned safely such
297 * as with get_task_mm(). If the mm is not current->mm, the mm_users
298 * pin should be released by calling mmput after mmu_notifier_register
299 * returns. mmu_notifier_unregister must be always called to
300 * unregister the notifier. mm_count is automatically pinned to allow
301 * mmu_notifier_unregister to safely run at any time later, before or
302 * after exit_mmap. ->release will always be called before exit_mmap
305 int mmu_notifier_register(struct mmu_notifier
*mn
, struct mm_struct
*mm
)
307 return do_mmu_notifier_register(mn
, mm
, 1);
309 EXPORT_SYMBOL_GPL(mmu_notifier_register
);
312 * Same as mmu_notifier_register but here the caller must hold the
313 * mmap_sem in write mode.
315 int __mmu_notifier_register(struct mmu_notifier
*mn
, struct mm_struct
*mm
)
317 return do_mmu_notifier_register(mn
, mm
, 0);
319 EXPORT_SYMBOL_GPL(__mmu_notifier_register
);
321 /* this is called after the last mmu_notifier_unregister() returned */
322 void __mmu_notifier_mm_destroy(struct mm_struct
*mm
)
324 BUG_ON(!hlist_empty(&mm
->mmu_notifier_mm
->list
));
325 kfree(mm
->mmu_notifier_mm
);
326 mm
->mmu_notifier_mm
= LIST_POISON1
; /* debug */
330 * This releases the mm_count pin automatically and frees the mm
331 * structure if it was the last user of it. It serializes against
332 * running mmu notifiers with SRCU and against mmu_notifier_unregister
333 * with the unregister lock + SRCU. All sptes must be dropped before
334 * calling mmu_notifier_unregister. ->release or any other notifier
335 * method may be invoked concurrently with mmu_notifier_unregister,
336 * and only after mmu_notifier_unregister returned we're guaranteed
337 * that ->release or any other method can't run anymore.
339 void mmu_notifier_unregister(struct mmu_notifier
*mn
, struct mm_struct
*mm
)
341 BUG_ON(atomic_read(&mm
->mm_count
) <= 0);
343 if (!hlist_unhashed(&mn
->hlist
)) {
345 * SRCU here will force exit_mmap to wait for ->release to
346 * finish before freeing the pages.
350 id
= srcu_read_lock(&srcu
);
352 * exit_mmap will block in mmu_notifier_release to guarantee
353 * that ->release is called before freeing the pages.
355 if (mn
->ops
->release
)
356 mn
->ops
->release(mn
, mm
);
357 srcu_read_unlock(&srcu
, id
);
359 spin_lock(&mm
->mmu_notifier_mm
->lock
);
361 * Can not use list_del_rcu() since __mmu_notifier_release
362 * can delete it before we hold the lock.
364 hlist_del_init_rcu(&mn
->hlist
);
365 spin_unlock(&mm
->mmu_notifier_mm
->lock
);
369 * Wait for any running method to finish, of course including
370 * ->release if it was run by mmu_notifier_release instead of us.
372 synchronize_srcu(&srcu
);
374 BUG_ON(atomic_read(&mm
->mm_count
) <= 0);
378 EXPORT_SYMBOL_GPL(mmu_notifier_unregister
);
381 * Same as mmu_notifier_unregister but no callback and no srcu synchronization.
383 void mmu_notifier_unregister_no_release(struct mmu_notifier
*mn
,
384 struct mm_struct
*mm
)
386 spin_lock(&mm
->mmu_notifier_mm
->lock
);
388 * Can not use list_del_rcu() since __mmu_notifier_release
389 * can delete it before we hold the lock.
391 hlist_del_init_rcu(&mn
->hlist
);
392 spin_unlock(&mm
->mmu_notifier_mm
->lock
);
394 BUG_ON(atomic_read(&mm
->mm_count
) <= 0);
397 EXPORT_SYMBOL_GPL(mmu_notifier_unregister_no_release
);