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Subject[PATCH v6 3/6] mm/notifier: add mmu_interval_notifier_update()
Date
When using mmu interval notifiers, the underlying VMA range that the
interval is tracking might be expanded or shrunk. Add a helper function
to allow the interval to be updated safely from the ops->invalidate()
callback in response to VMA range changes. This is effectively removing
and inserting the mmu interval notifier but more efficient.

Signed-off-by: Ralph Campbell <rcampbell@nvidia.com>
---
include/linux/mmu_notifier.h | 4 +++
mm/mmu_notifier.c | 69 ++++++++++++++++++++++++++++++++++--
2 files changed, 70 insertions(+), 3 deletions(-)

diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h
index 6dcaa632eef7..0ce59b4f22c2 100644
--- a/include/linux/mmu_notifier.h
+++ b/include/linux/mmu_notifier.h
@@ -251,6 +251,8 @@ struct mmu_interval_notifier {
struct mm_struct *mm;
struct hlist_node deferred_item;
unsigned long invalidate_seq;
+ unsigned long updated_start;
+ unsigned long updated_last;
};

#ifdef CONFIG_MMU_NOTIFIER
@@ -310,6 +312,8 @@ int mmu_interval_notifier_insert_safe(
const struct mmu_interval_notifier_ops *ops);
void mmu_interval_notifier_remove(struct mmu_interval_notifier *mni);
void mmu_interval_notifier_put(struct mmu_interval_notifier *mni);
+void mmu_interval_notifier_update(struct mmu_interval_notifier *mni,
+ unsigned long start, unsigned long last);

/**
* mmu_interval_set_seq - Save the invalidation sequence
diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c
index 40c837ae8d90..47ad9cc89aab 100644
--- a/mm/mmu_notifier.c
+++ b/mm/mmu_notifier.c
@@ -157,7 +157,14 @@ static void mn_itree_inv_end(struct mmu_notifier_mm *mmn_mm)
else {
interval_tree_remove(&mni->interval_tree,
&mmn_mm->itree);
- if (mni->ops->release)
+ if (mni->updated_last) {
+ mni->interval_tree.start = mni->updated_start;
+ mni->interval_tree.last = mni->updated_last;
+ mni->updated_start = 0;
+ mni->updated_last = 0;
+ interval_tree_insert(&mni->interval_tree,
+ &mmn_mm->itree);
+ } else if (mni->ops->release)
hlist_add_head(&mni->deferred_item,
&removed_list);
}
@@ -872,6 +879,8 @@ static int __mmu_interval_notifier_insert(
mni->ops = ops;
RB_CLEAR_NODE(&mni->interval_tree.rb);
mni->interval_tree.start = start;
+ mni->updated_start = 0;
+ mni->updated_last = 0;
/*
* Note that the representation of the intervals in the interval tree
* considers the ending point as contained in the interval.
@@ -1038,8 +1047,12 @@ static unsigned long __mmu_interval_notifier_put(
if (RB_EMPTY_NODE(&mni->interval_tree.rb)) {
hlist_del(&mni->deferred_item);
} else {
- hlist_add_head(&mni->deferred_item,
- &mmn_mm->deferred_list);
+ if (mni->updated_last) {
+ mni->updated_start = 0;
+ mni->updated_last = 0;
+ } else
+ hlist_add_head(&mni->deferred_item,
+ &mmn_mm->deferred_list);
seq = mmn_mm->invalidate_seq;
}
} else {
@@ -1108,6 +1121,56 @@ void mmu_interval_notifier_put(struct mmu_interval_notifier *mni)
}
EXPORT_SYMBOL_GPL(mmu_interval_notifier_put);

+/**
+ * mmu_interval_notifier_update - Update interval notifier range
+ * @mni: Interval notifier to update
+ * @start: New starting virtual address to monitor
+ * @last: New last virtual address (inclusive) to monitor
+ *
+ * This function updates the range being monitored and is safe to call from
+ * the invalidate() callback function.
+ * Upon return, the mmu_interval_notifier range may not be updated in the
+ * interval tree yet. The caller must use the normal interval notifier read
+ * flow via mmu_interval_read_begin() to establish SPTEs for this range.
+ */
+void mmu_interval_notifier_update(struct mmu_interval_notifier *mni,
+ unsigned long start, unsigned long last)
+{
+ struct mm_struct *mm = mni->mm;
+ struct mmu_notifier_mm *mmn_mm = mm->mmu_notifier_mm;
+ unsigned long seq = 0;
+
+ if (WARN_ON(start >= last))
+ return;
+
+ spin_lock(&mmn_mm->lock);
+ if (mn_itree_is_invalidating(mmn_mm)) {
+ /*
+ * Update is being called after insert put this on the
+ * deferred list, but before the deferred list was processed.
+ */
+ if (RB_EMPTY_NODE(&mni->interval_tree.rb)) {
+ mni->interval_tree.start = start;
+ mni->interval_tree.last = last;
+ } else {
+ if (!mni->updated_last)
+ hlist_add_head(&mni->deferred_item,
+ &mmn_mm->deferred_list);
+ mni->updated_start = start;
+ mni->updated_last = last;
+ }
+ seq = mmn_mm->invalidate_seq;
+ } else {
+ WARN_ON(RB_EMPTY_NODE(&mni->interval_tree.rb));
+ interval_tree_remove(&mni->interval_tree, &mmn_mm->itree);
+ mni->interval_tree.start = start;
+ mni->interval_tree.last = last;
+ interval_tree_insert(&mni->interval_tree, &mmn_mm->itree);
+ }
+ spin_unlock(&mmn_mm->lock);
+}
+EXPORT_SYMBOL_GPL(mmu_interval_notifier_update);
+
/**
* mmu_notifier_synchronize - Ensure all mmu_notifiers are freed
*
--
2.20.1
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