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8ee53820ed
For GRU and EPT, we need gup-fast to set referenced bit too (this is why it's correct to return 0 when shadow_access_mask is zero, it requires gup-fast to set the referenced bit). qemu-kvm access already sets the young bit in the pte if it isn't zero-copy, if it's zero copy or a shadow paging EPT minor fault we relay on gup-fast to signal the page is in use... We also need to check the young bits on the secondary pagetables for NPT and not nested shadow mmu as the data may never get accessed again by the primary pte. Without this closer accuracy, we'd have to remove the heuristic that avoids collapsing hugepages in hugepage virtual regions that have not even a single subpage in use. ->test_young is full backwards compatible with GRU and other usages that don't have young bits in pagetables set by the hardware and that should nuke the secondary mmu mappings when ->clear_flush_young runs just like EPT does. Removing the heuristic that checks the young bit in khugepaged/collapse_huge_page completely isn't so bad either probably but I thought it was worth it and this makes it reliable. Signed-off-by: Andrea Arcangeli <aarcange@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
319 lines
9.1 KiB
C
319 lines
9.1 KiB
C
/*
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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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#include <linux/slab.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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int __mmu_notifier_test_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->test_young) {
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young = mn->ops->test_young(mn, mm, address);
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if (young)
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break;
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}
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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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