298 lines
8.7 KiB
C
298 lines
8.7 KiB
C
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/*
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* linux/mm/mmu_notifier.c
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*
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* Copyright (C) 2008 Qumranet, Inc.
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* Copyright (C) 2008 SGI
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* Christoph Lameter <clameter@sgi.com>
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*
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* This work is licensed under the terms of the GNU GPL, version 2. See
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* the COPYING file in the top-level directory.
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*/
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#include <linux/rculist.h>
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#include <linux/mmu_notifier.h>
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#include <linux/module.h>
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#include <linux/mm.h>
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#include <linux/err.h>
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#include <linux/rcupdate.h>
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#include <linux/sched.h>
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/*
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* This function can't run concurrently against mmu_notifier_register
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* because mm->mm_users > 0 during mmu_notifier_register and exit_mmap
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* runs with mm_users == 0. Other tasks may still invoke mmu notifiers
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* in parallel despite there being no task using this mm any more,
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* through the vmas outside of the exit_mmap context, such as with
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* vmtruncate. This serializes against mmu_notifier_unregister with
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* the mmu_notifier_mm->lock in addition to RCU and it serializes
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* against the other mmu notifiers with RCU. struct mmu_notifier_mm
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* can't go away from under us as exit_mmap holds an mm_count pin
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* itself.
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*/
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void __mmu_notifier_release(struct mm_struct *mm)
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{
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struct mmu_notifier *mn;
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spin_lock(&mm->mmu_notifier_mm->lock);
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while (unlikely(!hlist_empty(&mm->mmu_notifier_mm->list))) {
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mn = hlist_entry(mm->mmu_notifier_mm->list.first,
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struct mmu_notifier,
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hlist);
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/*
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* We arrived before mmu_notifier_unregister so
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* mmu_notifier_unregister will do nothing other than
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* to wait ->release to finish and
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* mmu_notifier_unregister to return.
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*/
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hlist_del_init_rcu(&mn->hlist);
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/*
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* RCU here will block mmu_notifier_unregister until
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* ->release returns.
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*/
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rcu_read_lock();
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spin_unlock(&mm->mmu_notifier_mm->lock);
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/*
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* if ->release runs before mmu_notifier_unregister it
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* must be handled as it's the only way for the driver
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* to flush all existing sptes and stop the driver
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* from establishing any more sptes before all the
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* pages in the mm are freed.
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*/
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if (mn->ops->release)
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mn->ops->release(mn, mm);
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rcu_read_unlock();
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spin_lock(&mm->mmu_notifier_mm->lock);
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}
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spin_unlock(&mm->mmu_notifier_mm->lock);
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/*
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* synchronize_rcu here prevents mmu_notifier_release to
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* return to exit_mmap (which would proceed freeing all pages
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* in the mm) until the ->release method returns, if it was
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* invoked by mmu_notifier_unregister.
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*
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* The mmu_notifier_mm can't go away from under us because one
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* mm_count is hold by exit_mmap.
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*/
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synchronize_rcu();
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}
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/*
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* If no young bitflag is supported by the hardware, ->clear_flush_young can
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* unmap the address and return 1 or 0 depending if the mapping previously
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* existed or not.
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*/
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int __mmu_notifier_clear_flush_young(struct mm_struct *mm,
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unsigned long address)
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{
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struct mmu_notifier *mn;
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struct hlist_node *n;
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int young = 0;
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rcu_read_lock();
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hlist_for_each_entry_rcu(mn, n, &mm->mmu_notifier_mm->list, hlist) {
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if (mn->ops->clear_flush_young)
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young |= mn->ops->clear_flush_young(mn, mm, address);
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}
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rcu_read_unlock();
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return young;
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}
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void __mmu_notifier_change_pte(struct mm_struct *mm, unsigned long address,
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pte_t pte)
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{
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struct mmu_notifier *mn;
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struct hlist_node *n;
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rcu_read_lock();
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hlist_for_each_entry_rcu(mn, n, &mm->mmu_notifier_mm->list, hlist) {
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if (mn->ops->change_pte)
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mn->ops->change_pte(mn, mm, address, pte);
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/*
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* Some drivers don't have change_pte,
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* so we must call invalidate_page in that case.
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*/
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else if (mn->ops->invalidate_page)
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mn->ops->invalidate_page(mn, mm, address);
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}
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rcu_read_unlock();
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}
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void __mmu_notifier_invalidate_page(struct mm_struct *mm,
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unsigned long address)
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{
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struct mmu_notifier *mn;
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struct hlist_node *n;
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rcu_read_lock();
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hlist_for_each_entry_rcu(mn, n, &mm->mmu_notifier_mm->list, hlist) {
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if (mn->ops->invalidate_page)
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mn->ops->invalidate_page(mn, mm, address);
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}
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rcu_read_unlock();
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}
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void __mmu_notifier_invalidate_range_start(struct mm_struct *mm,
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unsigned long start, unsigned long end)
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{
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struct mmu_notifier *mn;
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struct hlist_node *n;
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rcu_read_lock();
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hlist_for_each_entry_rcu(mn, n, &mm->mmu_notifier_mm->list, hlist) {
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if (mn->ops->invalidate_range_start)
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mn->ops->invalidate_range_start(mn, mm, start, end);
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}
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rcu_read_unlock();
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}
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void __mmu_notifier_invalidate_range_end(struct mm_struct *mm,
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unsigned long start, unsigned long end)
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{
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struct mmu_notifier *mn;
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struct hlist_node *n;
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rcu_read_lock();
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hlist_for_each_entry_rcu(mn, n, &mm->mmu_notifier_mm->list, hlist) {
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if (mn->ops->invalidate_range_end)
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mn->ops->invalidate_range_end(mn, mm, start, end);
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}
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rcu_read_unlock();
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}
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static int do_mmu_notifier_register(struct mmu_notifier *mn,
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struct mm_struct *mm,
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int take_mmap_sem)
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{
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struct mmu_notifier_mm *mmu_notifier_mm;
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int ret;
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BUG_ON(atomic_read(&mm->mm_users) <= 0);
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ret = -ENOMEM;
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mmu_notifier_mm = kmalloc(sizeof(struct mmu_notifier_mm), GFP_KERNEL);
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if (unlikely(!mmu_notifier_mm))
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goto out;
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if (take_mmap_sem)
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down_write(&mm->mmap_sem);
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ret = mm_take_all_locks(mm);
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if (unlikely(ret))
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goto out_cleanup;
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if (!mm_has_notifiers(mm)) {
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INIT_HLIST_HEAD(&mmu_notifier_mm->list);
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spin_lock_init(&mmu_notifier_mm->lock);
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mm->mmu_notifier_mm = mmu_notifier_mm;
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mmu_notifier_mm = NULL;
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}
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atomic_inc(&mm->mm_count);
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/*
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* Serialize the update against mmu_notifier_unregister. A
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* side note: mmu_notifier_release can't run concurrently with
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* us because we hold the mm_users pin (either implicitly as
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* current->mm or explicitly with get_task_mm() or similar).
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* We can't race against any other mmu notifier method either
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* thanks to mm_take_all_locks().
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*/
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spin_lock(&mm->mmu_notifier_mm->lock);
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hlist_add_head(&mn->hlist, &mm->mmu_notifier_mm->list);
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spin_unlock(&mm->mmu_notifier_mm->lock);
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mm_drop_all_locks(mm);
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out_cleanup:
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if (take_mmap_sem)
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up_write(&mm->mmap_sem);
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/* kfree() does nothing if mmu_notifier_mm is NULL */
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kfree(mmu_notifier_mm);
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out:
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BUG_ON(atomic_read(&mm->mm_users) <= 0);
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return ret;
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}
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/*
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* Must not hold mmap_sem nor any other VM related lock when calling
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* this registration function. Must also ensure mm_users can't go down
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* to zero while this runs to avoid races with mmu_notifier_release,
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* so mm has to be current->mm or the mm should be pinned safely such
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* as with get_task_mm(). If the mm is not current->mm, the mm_users
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* pin should be released by calling mmput after mmu_notifier_register
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* returns. mmu_notifier_unregister must be always called to
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* unregister the notifier. mm_count is automatically pinned to allow
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* mmu_notifier_unregister to safely run at any time later, before or
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* after exit_mmap. ->release will always be called before exit_mmap
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* frees the pages.
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*/
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int mmu_notifier_register(struct mmu_notifier *mn, struct mm_struct *mm)
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{
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return do_mmu_notifier_register(mn, mm, 1);
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}
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EXPORT_SYMBOL_GPL(mmu_notifier_register);
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/*
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* Same as mmu_notifier_register but here the caller must hold the
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* mmap_sem in write mode.
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*/
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int __mmu_notifier_register(struct mmu_notifier *mn, struct mm_struct *mm)
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{
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return do_mmu_notifier_register(mn, mm, 0);
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}
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EXPORT_SYMBOL_GPL(__mmu_notifier_register);
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/* this is called after the last mmu_notifier_unregister() returned */
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void __mmu_notifier_mm_destroy(struct mm_struct *mm)
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{
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BUG_ON(!hlist_empty(&mm->mmu_notifier_mm->list));
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kfree(mm->mmu_notifier_mm);
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mm->mmu_notifier_mm = LIST_POISON1; /* debug */
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}
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/*
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* This releases the mm_count pin automatically and frees the mm
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* structure if it was the last user of it. It serializes against
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* running mmu notifiers with RCU and against mmu_notifier_unregister
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* with the unregister lock + RCU. All sptes must be dropped before
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* calling mmu_notifier_unregister. ->release or any other notifier
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* method may be invoked concurrently with mmu_notifier_unregister,
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* and only after mmu_notifier_unregister returned we're guaranteed
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* that ->release or any other method can't run anymore.
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*/
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void mmu_notifier_unregister(struct mmu_notifier *mn, struct mm_struct *mm)
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{
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BUG_ON(atomic_read(&mm->mm_count) <= 0);
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spin_lock(&mm->mmu_notifier_mm->lock);
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if (!hlist_unhashed(&mn->hlist)) {
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hlist_del_rcu(&mn->hlist);
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/*
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* RCU here will force exit_mmap to wait ->release to finish
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* before freeing the pages.
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*/
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rcu_read_lock();
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spin_unlock(&mm->mmu_notifier_mm->lock);
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/*
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* exit_mmap will block in mmu_notifier_release to
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* guarantee ->release is called before freeing the
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* pages.
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*/
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if (mn->ops->release)
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mn->ops->release(mn, mm);
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rcu_read_unlock();
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} else
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spin_unlock(&mm->mmu_notifier_mm->lock);
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/*
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* Wait any running method to finish, of course including
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* ->release if it was run by mmu_notifier_relase instead of us.
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*/
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synchronize_rcu();
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BUG_ON(atomic_read(&mm->mm_count) <= 0);
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mmdrop(mm);
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}
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EXPORT_SYMBOL_GPL(mmu_notifier_unregister);
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