2 * linux/mm/mmu_notifier.c
4 * Copyright (C) 2008 Qumranet, Inc.
5 * Copyright (C) 2008 SGI
6 * Christoph Lameter <clameter@sgi.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/module.h>
16 #include <linux/err.h>
17 #include <linux/rcupdate.h>
18 #include <linux/sched.h>
19 #include <linux/slab.h>
22 * This function can't run concurrently against mmu_notifier_register
23 * because mm->mm_users > 0 during mmu_notifier_register and exit_mmap
24 * runs with mm_users == 0. Other tasks may still invoke mmu notifiers
25 * in parallel despite there being no task using this mm any more,
26 * through the vmas outside of the exit_mmap context, such as with
27 * vmtruncate. This serializes against mmu_notifier_unregister with
28 * the mmu_notifier_mm->lock in addition to RCU and it serializes
29 * against the other mmu notifiers with RCU. struct mmu_notifier_mm
30 * can't go away from under us as exit_mmap holds an mm_count pin
33 void __mmu_notifier_release(struct mm_struct *mm)
35 struct mmu_notifier *mn;
37 spin_lock(&mm->mmu_notifier_mm->lock);
38 while (unlikely(!hlist_empty(&mm->mmu_notifier_mm->list))) {
39 mn = hlist_entry(mm->mmu_notifier_mm->list.first,
43 * We arrived before mmu_notifier_unregister so
44 * mmu_notifier_unregister will do nothing other than
45 * to wait ->release to finish and
46 * mmu_notifier_unregister to return.
48 hlist_del_init_rcu(&mn->hlist);
50 * RCU here will block mmu_notifier_unregister until
54 spin_unlock(&mm->mmu_notifier_mm->lock);
56 * if ->release runs before mmu_notifier_unregister it
57 * must be handled as it's the only way for the driver
58 * to flush all existing sptes and stop the driver
59 * from establishing any more sptes before all the
60 * pages in the mm are freed.
63 mn->ops->release(mn, mm);
65 spin_lock(&mm->mmu_notifier_mm->lock);
67 spin_unlock(&mm->mmu_notifier_mm->lock);
70 * synchronize_rcu here prevents mmu_notifier_release to
71 * return to exit_mmap (which would proceed freeing all pages
72 * in the mm) until the ->release method returns, if it was
73 * invoked by mmu_notifier_unregister.
75 * The mmu_notifier_mm can't go away from under us because one
76 * mm_count is hold by exit_mmap.
82 * If no young bitflag is supported by the hardware, ->clear_flush_young can
83 * unmap the address and return 1 or 0 depending if the mapping previously
86 int __mmu_notifier_clear_flush_young(struct mm_struct *mm,
87 unsigned long address)
89 struct mmu_notifier *mn;
94 hlist_for_each_entry_rcu(mn, n, &mm->mmu_notifier_mm->list, hlist) {
95 if (mn->ops->clear_flush_young)
96 young |= mn->ops->clear_flush_young(mn, mm, address);
103 int __mmu_notifier_test_young(struct mm_struct *mm,
104 unsigned long address)
106 struct mmu_notifier *mn;
107 struct hlist_node *n;
111 hlist_for_each_entry_rcu(mn, n, &mm->mmu_notifier_mm->list, hlist) {
112 if (mn->ops->test_young) {
113 young = mn->ops->test_young(mn, mm, address);
123 void __mmu_notifier_change_pte(struct mm_struct *mm, unsigned long address,
126 struct mmu_notifier *mn;
127 struct hlist_node *n;
130 hlist_for_each_entry_rcu(mn, n, &mm->mmu_notifier_mm->list, hlist) {
131 if (mn->ops->change_pte)
132 mn->ops->change_pte(mn, mm, address, pte);
134 * Some drivers don't have change_pte,
135 * so we must call invalidate_page in that case.
137 else if (mn->ops->invalidate_page)
138 mn->ops->invalidate_page(mn, mm, address);
143 void __mmu_notifier_invalidate_page(struct mm_struct *mm,
144 unsigned long address)
146 struct mmu_notifier *mn;
147 struct hlist_node *n;
150 hlist_for_each_entry_rcu(mn, n, &mm->mmu_notifier_mm->list, hlist) {
151 if (mn->ops->invalidate_page)
152 mn->ops->invalidate_page(mn, mm, address);
157 void __mmu_notifier_invalidate_range_start(struct mm_struct *mm,
158 unsigned long start, unsigned long end)
160 struct mmu_notifier *mn;
161 struct hlist_node *n;
164 hlist_for_each_entry_rcu(mn, n, &mm->mmu_notifier_mm->list, hlist) {
165 if (mn->ops->invalidate_range_start)
166 mn->ops->invalidate_range_start(mn, mm, start, end);
171 void __mmu_notifier_invalidate_range_end(struct mm_struct *mm,
172 unsigned long start, unsigned long end)
174 struct mmu_notifier *mn;
175 struct hlist_node *n;
178 hlist_for_each_entry_rcu(mn, n, &mm->mmu_notifier_mm->list, hlist) {
179 if (mn->ops->invalidate_range_end)
180 mn->ops->invalidate_range_end(mn, mm, start, end);
185 static int do_mmu_notifier_register(struct mmu_notifier *mn,
186 struct mm_struct *mm,
189 struct mmu_notifier_mm *mmu_notifier_mm;
192 BUG_ON(atomic_read(&mm->mm_users) <= 0);
195 mmu_notifier_mm = kmalloc(sizeof(struct mmu_notifier_mm), GFP_KERNEL);
196 if (unlikely(!mmu_notifier_mm))
200 down_write(&mm->mmap_sem);
201 ret = mm_take_all_locks(mm);
205 if (!mm_has_notifiers(mm)) {
206 INIT_HLIST_HEAD(&mmu_notifier_mm->list);
207 spin_lock_init(&mmu_notifier_mm->lock);
208 mm->mmu_notifier_mm = mmu_notifier_mm;
209 mmu_notifier_mm = NULL;
211 atomic_inc(&mm->mm_count);
214 * Serialize the update against mmu_notifier_unregister. A
215 * side note: mmu_notifier_release can't run concurrently with
216 * us because we hold the mm_users pin (either implicitly as
217 * current->mm or explicitly with get_task_mm() or similar).
218 * We can't race against any other mmu notifier method either
219 * thanks to mm_take_all_locks().
221 spin_lock(&mm->mmu_notifier_mm->lock);
222 hlist_add_head(&mn->hlist, &mm->mmu_notifier_mm->list);
223 spin_unlock(&mm->mmu_notifier_mm->lock);
225 mm_drop_all_locks(mm);
228 up_write(&mm->mmap_sem);
229 /* kfree() does nothing if mmu_notifier_mm is NULL */
230 kfree(mmu_notifier_mm);
232 BUG_ON(atomic_read(&mm->mm_users) <= 0);
237 * Must not hold mmap_sem nor any other VM related lock when calling
238 * this registration function. Must also ensure mm_users can't go down
239 * to zero while this runs to avoid races with mmu_notifier_release,
240 * so mm has to be current->mm or the mm should be pinned safely such
241 * as with get_task_mm(). If the mm is not current->mm, the mm_users
242 * pin should be released by calling mmput after mmu_notifier_register
243 * returns. mmu_notifier_unregister must be always called to
244 * unregister the notifier. mm_count is automatically pinned to allow
245 * mmu_notifier_unregister to safely run at any time later, before or
246 * after exit_mmap. ->release will always be called before exit_mmap
249 int mmu_notifier_register(struct mmu_notifier *mn, struct mm_struct *mm)
251 return do_mmu_notifier_register(mn, mm, 1);
253 EXPORT_SYMBOL_GPL(mmu_notifier_register);
256 * Same as mmu_notifier_register but here the caller must hold the
257 * mmap_sem in write mode.
259 int __mmu_notifier_register(struct mmu_notifier *mn, struct mm_struct *mm)
261 return do_mmu_notifier_register(mn, mm, 0);
263 EXPORT_SYMBOL_GPL(__mmu_notifier_register);
265 /* this is called after the last mmu_notifier_unregister() returned */
266 void __mmu_notifier_mm_destroy(struct mm_struct *mm)
268 BUG_ON(!hlist_empty(&mm->mmu_notifier_mm->list));
269 kfree(mm->mmu_notifier_mm);
270 mm->mmu_notifier_mm = LIST_POISON1; /* debug */
274 * This releases the mm_count pin automatically and frees the mm
275 * structure if it was the last user of it. It serializes against
276 * running mmu notifiers with RCU and against mmu_notifier_unregister
277 * with the unregister lock + RCU. All sptes must be dropped before
278 * calling mmu_notifier_unregister. ->release or any other notifier
279 * method may be invoked concurrently with mmu_notifier_unregister,
280 * and only after mmu_notifier_unregister returned we're guaranteed
281 * that ->release or any other method can't run anymore.
283 void mmu_notifier_unregister(struct mmu_notifier *mn, struct mm_struct *mm)
285 BUG_ON(atomic_read(&mm->mm_count) <= 0);
287 spin_lock(&mm->mmu_notifier_mm->lock);
288 if (!hlist_unhashed(&mn->hlist)) {
289 hlist_del_rcu(&mn->hlist);
292 * RCU here will force exit_mmap to wait ->release to finish
293 * before freeing the pages.
296 spin_unlock(&mm->mmu_notifier_mm->lock);
298 * exit_mmap will block in mmu_notifier_release to
299 * guarantee ->release is called before freeing the
302 if (mn->ops->release)
303 mn->ops->release(mn, mm);
306 spin_unlock(&mm->mmu_notifier_mm->lock);
309 * Wait any running method to finish, of course including
310 * ->release if it was run by mmu_notifier_relase instead of us.
314 BUG_ON(atomic_read(&mm->mm_count) <= 0);
318 EXPORT_SYMBOL_GPL(mmu_notifier_unregister);