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![Vladimir Davydov](/assets/img/avatar_default.png)
In the scope of the idle memory tracking feature, which is introduced by the following patch, we need to clear the referenced/accessed bit not only in primary, but also in secondary ptes. The latter is required in order to estimate wss of KVM VMs. At the same time we want to avoid flushing tlb, because it is quite expensive and it won't really affect the final result. Currently, there is no function for clearing pte young bit that would meet our requirements, so this patch introduces one. To achieve that we have to add a new mmu-notifier callback, clear_young, since there is no method for testing-and-clearing a secondary pte w/o flushing tlb. The new method is not mandatory and currently only implemented by KVM. Signed-off-by: Vladimir Davydov <vdavydov@parallels.com> Reviewed-by: Andres Lagar-Cavilla <andreslc@google.com> Acked-by: Paolo Bonzini <pbonzini@redhat.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@suse.cz> Cc: Greg Thelen <gthelen@google.com> Cc: Michel Lespinasse <walken@google.com> Cc: David Rientjes <rientjes@google.com> Cc: Pavel Emelyanov <xemul@parallels.com> Cc: Cyrill Gorcunov <gorcunov@openvz.org> Cc: Jonathan Corbet <corbet@lwn.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
413 lines
12 KiB
C
413 lines
12 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/export.h>
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#include <linux/mm.h>
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#include <linux/err.h>
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#include <linux/srcu.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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/* global SRCU for all MMs */
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static struct srcu_struct srcu;
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/*
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* This function allows mmu_notifier::release callback to delay a call to
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* a function that will free appropriate resources. The function must be
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* quick and must not block.
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*/
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void mmu_notifier_call_srcu(struct rcu_head *rcu,
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void (*func)(struct rcu_head *rcu))
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{
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call_srcu(&srcu, rcu, func);
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}
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EXPORT_SYMBOL_GPL(mmu_notifier_call_srcu);
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void mmu_notifier_synchronize(void)
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{
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/* Wait for any running method to finish. */
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srcu_barrier(&srcu);
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}
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EXPORT_SYMBOL_GPL(mmu_notifier_synchronize);
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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 SRCU and it serializes
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* against the other mmu notifiers with SRCU. 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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int id;
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/*
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* SRCU here will block mmu_notifier_unregister until
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* ->release returns.
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*/
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id = srcu_read_lock(&srcu);
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hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist)
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/*
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* If ->release runs before mmu_notifier_unregister it must be
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* handled, as it's the only way for the driver to flush all
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* existing sptes and stop the driver from establishing any more
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* sptes before all the 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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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 to wait
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* for ->release to finish and for mmu_notifier_unregister to
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* return.
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*/
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hlist_del_init_rcu(&mn->hlist);
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}
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spin_unlock(&mm->mmu_notifier_mm->lock);
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srcu_read_unlock(&srcu, id);
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/*
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* synchronize_srcu here prevents mmu_notifier_release from returning to
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* exit_mmap (which would proceed with freeing all pages in the mm)
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* until the ->release method returns, if it was invoked by
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* mmu_notifier_unregister.
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*
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* The mmu_notifier_mm can't go away from under us because one mm_count
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* is held by exit_mmap.
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*/
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synchronize_srcu(&srcu);
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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 start,
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unsigned long end)
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{
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struct mmu_notifier *mn;
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int young = 0, id;
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id = srcu_read_lock(&srcu);
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hlist_for_each_entry_rcu(mn, &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, start, end);
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}
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srcu_read_unlock(&srcu, id);
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return young;
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}
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int __mmu_notifier_clear_young(struct mm_struct *mm,
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unsigned long start,
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unsigned long end)
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{
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struct mmu_notifier *mn;
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int young = 0, id;
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id = srcu_read_lock(&srcu);
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hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
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if (mn->ops->clear_young)
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young |= mn->ops->clear_young(mn, mm, start, end);
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}
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srcu_read_unlock(&srcu, id);
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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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int young = 0, id;
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id = srcu_read_lock(&srcu);
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hlist_for_each_entry_rcu(mn, &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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srcu_read_unlock(&srcu, id);
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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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int id;
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id = srcu_read_lock(&srcu);
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hlist_for_each_entry_rcu(mn, &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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srcu_read_unlock(&srcu, id);
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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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int id;
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id = srcu_read_lock(&srcu);
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hlist_for_each_entry_rcu(mn, &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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srcu_read_unlock(&srcu, id);
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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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int id;
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id = srcu_read_lock(&srcu);
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hlist_for_each_entry_rcu(mn, &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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srcu_read_unlock(&srcu, id);
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}
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EXPORT_SYMBOL_GPL(__mmu_notifier_invalidate_range_start);
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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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int id;
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id = srcu_read_lock(&srcu);
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hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
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/*
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* Call invalidate_range here too to avoid the need for the
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* subsystem of having to register an invalidate_range_end
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* call-back when there is invalidate_range already. Usually a
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* subsystem registers either invalidate_range_start()/end() or
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* invalidate_range(), so this will be no additional overhead
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* (besides the pointer check).
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*/
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if (mn->ops->invalidate_range)
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mn->ops->invalidate_range(mn, mm, start, end);
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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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srcu_read_unlock(&srcu, id);
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}
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EXPORT_SYMBOL_GPL(__mmu_notifier_invalidate_range_end);
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void __mmu_notifier_invalidate_range(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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int id;
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id = srcu_read_lock(&srcu);
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hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
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if (mn->ops->invalidate_range)
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mn->ops->invalidate_range(mn, mm, start, end);
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}
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srcu_read_unlock(&srcu, id);
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}
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EXPORT_SYMBOL_GPL(__mmu_notifier_invalidate_range);
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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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/*
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* Verify that mmu_notifier_init() already run and the global srcu is
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* initialized.
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*/
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BUG_ON(!srcu.per_cpu_ref);
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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_clean;
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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_clean:
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if (take_mmap_sem)
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up_write(&mm->mmap_sem);
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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 SRCU and against mmu_notifier_unregister
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* with the unregister lock + SRCU. 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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if (!hlist_unhashed(&mn->hlist)) {
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/*
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* SRCU here will force exit_mmap to wait for ->release to
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* finish before freeing the pages.
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*/
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int id;
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id = srcu_read_lock(&srcu);
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/*
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* exit_mmap will block in mmu_notifier_release to guarantee
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* that ->release is called before freeing the 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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srcu_read_unlock(&srcu, id);
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spin_lock(&mm->mmu_notifier_mm->lock);
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/*
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* Can not use list_del_rcu() since __mmu_notifier_release
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* can delete it before we hold the lock.
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*/
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hlist_del_init_rcu(&mn->hlist);
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spin_unlock(&mm->mmu_notifier_mm->lock);
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}
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/*
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* Wait for any running method to finish, of course including
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* ->release if it was run by mmu_notifier_release instead of us.
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*/
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synchronize_srcu(&srcu);
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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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/*
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* Same as mmu_notifier_unregister but no callback and no srcu synchronization.
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*/
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void mmu_notifier_unregister_no_release(struct mmu_notifier *mn,
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struct mm_struct *mm)
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{
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spin_lock(&mm->mmu_notifier_mm->lock);
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/*
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* Can not use list_del_rcu() since __mmu_notifier_release
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* can delete it before we hold the lock.
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*/
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hlist_del_init_rcu(&mn->hlist);
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spin_unlock(&mm->mmu_notifier_mm->lock);
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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_no_release);
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static int __init mmu_notifier_init(void)
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{
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return init_srcu_struct(&srcu);
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}
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subsys_initcall(mmu_notifier_init);
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