[PATCH v3 1/3] iova: convert from rbtree to maple tree

[Rik van Riel <riel@surriel.com>]

From: Rik van Riel <riel@meta.com>

Replace the hand-rolled rbtree in the IOVA allocator with a maple tree.
The maple tree is a B-tree variant designed for range tracking with
built-in gap searching, making it a natural fit for IOVA address space
management -- the same data structure is used by the kernel VMA
subsystem for the analogous problem.

Key changes:

  - struct iova shrinks from 40 bytes (rb_node 24 + pfn_hi 8 + pfn_lo 8)
    to just pfn_hi + pfn_lo (16 bytes). SLAB_HWCACHE_ALIGN is dropped
    from the iova slab cache since struct iova no longer contains an
    embedded rb_node touched during tree rebalancing -- tree traversal
    now touches maple nodes exclusively. This lets the slab allocator
    pack 16-byte objects tightly instead of rounding to 64 bytes.

    The maple tree replaces the embedded rb_node with external B-tree
    nodes: each maple_arange_64 node is 256 bytes and holds up to 10
    entries, plus internal nodes add ~11% overhead. At typical
    utilization (~70-90% full), this works out to ~28-41 bytes of maple
    tree node memory per IOVA entry. The net per-entry cost is ~44-57
    bytes (16 bytes slab + ~28-41 bytes maple), compared to ~64 bytes
    with the old rbtree (64 bytes HWCACHE_ALIGN slab + 0 bytes
    embedded rbtree). Combined with the maple tree's O(log_10 n)
    search depth and better cache locality from B-tree fan-out,
    this improves both memory efficiency and search performance.

  - struct iova_domain replaces rb_root + cached_node + cached32_node
    + anchor with a single struct maple_tree. The iova_rbtree_lock
    spinlock is renamed to iova_lock. The maple tree is initialized
    with MT_FLAGS_ALLOC_RANGE (enables gap tracking for
    mas_empty_area_rev) and MT_FLAGS_LOCK_EXTERN (uses the existing
    iova_lock spinlock instead of the maple tree internal lock).

  - Allocation via __alloc_and_insert_iova_range() uses
    mas_empty_area_rev() to find the highest-addressed gap of
    sufficient size below limit_pfn in O(log n) with B-tree fan-out.
    Alignment is handled by over-requesting (size + alignment - 1)
    to guarantee room after rounding, eliminating the need for a
    retry loop. The result is stored with mas_store_gfp().

  - Lookup via private_find_iova() uses mas_walk() for O(log n)
    point-in-range lookup.

  - Deletion via remove_iova() uses mas_erase(). No successor gap
    fixup needed -- the maple tree handles it internally.

  - reserve_iova() walks the requested range for existing entries,
    computes the merged range, collects old entries for freeing, then
    stores a single merged entry. If the request is fully covered by
    an existing entry, it returns that entry without allocating.

  - The IOVA_ANCHOR sentinel node is eliminated. The maple tree
    tracks gaps implicitly, including the space above the highest
    allocation.

  - The cached_node / cached32_node fields and all their helpers
    are eliminated. The maple tree B-tree structure provides
    equivalent or better cache behaviour.

The rcache (magazine cache) layer is unchanged -- it operates on raw
pfn values and is orthogonal to the tree backing store.

Assisted-by: Claude:claude-opus-4-6
Signed-off-by: Rik van Riel <riel@surriel.com>
Suggested-by: Robin Murphy <robin.murphy@arm.com>
---
 drivers/iommu/iova.c | 338 ++++++++++++-------------------------------
 include/linux/iova.h |  10 +-
 2 files changed, 98 insertions(+), 250 deletions(-)

diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
index 021daf6528de..523d1e8315f9 100644
--- a/drivers/iommu/iova.c
+++ b/drivers/iommu/iova.c
@@ -13,9 +13,7 @@
 #include <linux/bitops.h>
 #include <linux/cpu.h>
 #include <linux/workqueue.h>
-
-/* The anchor node sits above the top of the usable address space */
-#define IOVA_ANCHOR	~0UL
+#include <linux/maple_tree.h>
 
 #define IOVA_RANGE_CACHE_MAX_SIZE 6	/* log of max cached IOVA range size (in pages) */
 
@@ -29,11 +27,6 @@ static void free_iova_rcaches(struct iova_domain *iovad);
 static void free_cpu_cached_iovas(unsigned int cpu, struct iova_domain *iovad);
 static void free_global_cached_iovas(struct iova_domain *iovad);
 
-static struct iova *to_iova(struct rb_node *node)
-{
-	return rb_entry(node, struct iova, node);
-}
-
 void
 init_iova_domain(struct iova_domain *iovad, unsigned long granule,
 	unsigned long start_pfn)
@@ -45,180 +38,63 @@ init_iova_domain(struct iova_domain *iovad, unsigned long granule,
 	 */
 	BUG_ON((granule > PAGE_SIZE) || !is_power_of_2(granule));
 
-	spin_lock_init(&iovad->iova_rbtree_lock);
-	iovad->rbroot = RB_ROOT;
-	iovad->cached_node = &iovad->anchor.node;
-	iovad->cached32_node = &iovad->anchor.node;
+	spin_lock_init(&iovad->iova_lock);
+	mt_init_flags(&iovad->mtree,
+		      MT_FLAGS_ALLOC_RANGE | MT_FLAGS_LOCK_EXTERN);
+	mt_set_external_lock(&iovad->mtree, &iovad->iova_lock);
 	iovad->granule = granule;
 	iovad->start_pfn = start_pfn;
 	iovad->dma_32bit_pfn = 1UL << (32 - iova_shift(iovad));
 	iovad->max32_alloc_size = iovad->dma_32bit_pfn;
-	iovad->anchor.pfn_lo = iovad->anchor.pfn_hi = IOVA_ANCHOR;
-	rb_link_node(&iovad->anchor.node, NULL, &iovad->rbroot.rb_node);
-	rb_insert_color(&iovad->anchor.node, &iovad->rbroot);
 }
 EXPORT_SYMBOL_GPL(init_iova_domain);
 
-static struct rb_node *
-__get_cached_rbnode(struct iova_domain *iovad, unsigned long limit_pfn)
-{
-	if (limit_pfn <= iovad->dma_32bit_pfn)
-		return iovad->cached32_node;
-
-	return iovad->cached_node;
-}
-
-static void
-__cached_rbnode_insert_update(struct iova_domain *iovad, struct iova *new)
-{
-	if (new->pfn_hi < iovad->dma_32bit_pfn)
-		iovad->cached32_node = &new->node;
-	else
-		iovad->cached_node = &new->node;
-}
-
-static void
-__cached_rbnode_delete_update(struct iova_domain *iovad, struct iova *free)
-{
-	struct iova *cached_iova;
-
-	cached_iova = to_iova(iovad->cached32_node);
-	if (free == cached_iova ||
-	    (free->pfn_hi < iovad->dma_32bit_pfn &&
-	     free->pfn_lo >= cached_iova->pfn_lo))
-		iovad->cached32_node = rb_next(&free->node);
-
-	if (free->pfn_lo < iovad->dma_32bit_pfn)
-		iovad->max32_alloc_size = iovad->dma_32bit_pfn;
-
-	cached_iova = to_iova(iovad->cached_node);
-	if (free->pfn_lo >= cached_iova->pfn_lo)
-		iovad->cached_node = rb_next(&free->node);
-}
-
-static struct rb_node *iova_find_limit(struct iova_domain *iovad, unsigned long limit_pfn)
-{
-	struct rb_node *node, *next;
-	/*
-	 * Ideally what we'd like to judge here is whether limit_pfn is close
-	 * enough to the highest-allocated IOVA that starting the allocation
-	 * walk from the anchor node will be quicker than this initial work to
-	 * find an exact starting point (especially if that ends up being the
-	 * anchor node anyway). This is an incredibly crude approximation which
-	 * only really helps the most likely case, but is at least trivially easy.
-	 */
-	if (limit_pfn > iovad->dma_32bit_pfn)
-		return &iovad->anchor.node;
-
-	node = iovad->rbroot.rb_node;
-	while (to_iova(node)->pfn_hi < limit_pfn)
-		node = node->rb_right;
-
-search_left:
-	while (node->rb_left && to_iova(node->rb_left)->pfn_lo >= limit_pfn)
-		node = node->rb_left;
-
-	if (!node->rb_left)
-		return node;
-
-	next = node->rb_left;
-	while (next->rb_right) {
-		next = next->rb_right;
-		if (to_iova(next)->pfn_lo >= limit_pfn) {
-			node = next;
-			goto search_left;
-		}
-	}
-
-	return node;
-}
-
-/* Insert the iova into domain rbtree by holding writer lock */
-static void
-iova_insert_rbtree(struct rb_root *root, struct iova *iova,
-		   struct rb_node *start)
-{
-	struct rb_node **new, *parent = NULL;
-
-	new = (start) ? &start : &(root->rb_node);
-	/* Figure out where to put new node */
-	while (*new) {
-		struct iova *this = to_iova(*new);
-
-		parent = *new;
-
-		if (iova->pfn_lo < this->pfn_lo)
-			new = &((*new)->rb_left);
-		else if (iova->pfn_lo > this->pfn_lo)
-			new = &((*new)->rb_right);
-		else {
-			WARN_ON(1); /* this should not happen */
-			return;
-		}
-	}
-	/* Add new node and rebalance tree. */
-	rb_link_node(&iova->node, parent, new);
-	rb_insert_color(&iova->node, root);
-}
-
 static int __alloc_and_insert_iova_range(struct iova_domain *iovad,
 		unsigned long size, unsigned long limit_pfn,
 			struct iova *new, bool size_aligned)
 {
-	struct rb_node *curr, *prev;
-	struct iova *curr_iova;
 	unsigned long flags;
-	unsigned long new_pfn, retry_pfn;
+	unsigned long new_pfn;
 	unsigned long align_mask = ~0UL;
-	unsigned long high_pfn = limit_pfn, low_pfn = iovad->start_pfn;
+	unsigned long search_size = size;
+	MA_STATE(mas, &iovad->mtree, 0, 0);
+
+	if (size_aligned) {
+		unsigned long align = 1UL << fls_long(size - 1);
 
-	if (size_aligned)
 		align_mask <<= fls_long(size - 1);
+		search_size = size + align - 1;
+	}
 
-	/* Walk the tree backwards */
-	spin_lock_irqsave(&iovad->iova_rbtree_lock, flags);
+	spin_lock_irqsave(&iovad->iova_lock, flags);
 	if (limit_pfn <= iovad->dma_32bit_pfn &&
 			size >= iovad->max32_alloc_size)
 		goto iova32_full;
 
-	curr = __get_cached_rbnode(iovad, limit_pfn);
-	curr_iova = to_iova(curr);
-	retry_pfn = curr_iova->pfn_hi;
+	if (mas_empty_area_rev(&mas, iovad->start_pfn,
+				 limit_pfn - 1, search_size))
+		goto alloc_fail;
 
-retry:
-	do {
-		high_pfn = min(high_pfn, curr_iova->pfn_lo);
-		new_pfn = (high_pfn - size) & align_mask;
-		prev = curr;
-		curr = rb_prev(curr);
-		curr_iova = to_iova(curr);
-	} while (curr && new_pfn <= curr_iova->pfn_hi && new_pfn >= low_pfn);
-
-	if (high_pfn < size || new_pfn < low_pfn) {
-		if (low_pfn == iovad->start_pfn && retry_pfn < limit_pfn) {
-			high_pfn = limit_pfn;
-			low_pfn = retry_pfn + 1;
-			curr = iova_find_limit(iovad, limit_pfn);
-			curr_iova = to_iova(curr);
-			goto retry;
-		}
-		iovad->max32_alloc_size = size;
-		goto iova32_full;
-	}
+	new_pfn = (mas.last - size + 1) & align_mask;
+	if (new_pfn < mas.index || new_pfn < iovad->start_pfn)
+		goto alloc_fail;
 
-	/* pfn_lo will point to size aligned address if size_aligned is set */
 	new->pfn_lo = new_pfn;
-	new->pfn_hi = new->pfn_lo + size - 1;
+	new->pfn_hi = new_pfn + size - 1;
 
-	/* If we have 'prev', it's a valid place to start the insertion. */
-	iova_insert_rbtree(&iovad->rbroot, new, prev);
-	__cached_rbnode_insert_update(iovad, new);
+	mas.index = new->pfn_lo;
+	mas.last = new->pfn_hi;
+	if (mas_store_gfp(&mas, new, GFP_ATOMIC))
+		goto alloc_fail;
 
-	spin_unlock_irqrestore(&iovad->iova_rbtree_lock, flags);
+	spin_unlock_irqrestore(&iovad->iova_lock, flags);
 	return 0;
 
+alloc_fail:
+	if (limit_pfn <= iovad->dma_32bit_pfn)
+		iovad->max32_alloc_size = size;
 iova32_full:
-	spin_unlock_irqrestore(&iovad->iova_rbtree_lock, flags);
+	spin_unlock_irqrestore(&iovad->iova_lock, flags);
 	return -ENOMEM;
 }
 
@@ -233,8 +109,7 @@ static struct iova *alloc_iova_mem(void)
 
 static void free_iova_mem(struct iova *iova)
 {
-	if (iova->pfn_lo != IOVA_ANCHOR)
-		kmem_cache_free(iova_cache, iova);
+	kmem_cache_free(iova_cache, iova);
 }
 
 /**
@@ -275,29 +150,22 @@ EXPORT_SYMBOL_GPL(alloc_iova);
 static struct iova *
 private_find_iova(struct iova_domain *iovad, unsigned long pfn)
 {
-	struct rb_node *node = iovad->rbroot.rb_node;
+	MA_STATE(mas, &iovad->mtree, pfn, pfn);
 
-	assert_spin_locked(&iovad->iova_rbtree_lock);
-
-	while (node) {
-		struct iova *iova = to_iova(node);
-
-		if (pfn < iova->pfn_lo)
-			node = node->rb_left;
-		else if (pfn > iova->pfn_hi)
-			node = node->rb_right;
-		else
-			return iova;	/* pfn falls within iova's range */
-	}
-
-	return NULL;
+	assert_spin_locked(&iovad->iova_lock);
+	return mas_walk(&mas);
 }
 
 static void remove_iova(struct iova_domain *iovad, struct iova *iova)
 {
-	assert_spin_locked(&iovad->iova_rbtree_lock);
-	__cached_rbnode_delete_update(iovad, iova);
-	rb_erase(&iova->node, &iovad->rbroot);
+	MA_STATE(mas, &iovad->mtree, iova->pfn_lo, iova->pfn_hi);
+
+	assert_spin_locked(&iovad->iova_lock);
+
+	if (iova->pfn_lo < iovad->dma_32bit_pfn)
+		iovad->max32_alloc_size = iovad->dma_32bit_pfn;
+
+	mas_store_gfp(&mas, NULL, GFP_ATOMIC);
 }
 
 /**
@@ -312,10 +180,9 @@ struct iova *find_iova(struct iova_domain *iovad, unsigned long pfn)
 	unsigned long flags;
 	struct iova *iova;
 
-	/* Take the lock so that no other thread is manipulating the rbtree */
-	spin_lock_irqsave(&iovad->iova_rbtree_lock, flags);
+	spin_lock_irqsave(&iovad->iova_lock, flags);
 	iova = private_find_iova(iovad, pfn);
-	spin_unlock_irqrestore(&iovad->iova_rbtree_lock, flags);
+	spin_unlock_irqrestore(&iovad->iova_lock, flags);
 	return iova;
 }
 EXPORT_SYMBOL_GPL(find_iova);
@@ -331,9 +198,9 @@ __free_iova(struct iova_domain *iovad, struct iova *iova)
 {
 	unsigned long flags;
 
-	spin_lock_irqsave(&iovad->iova_rbtree_lock, flags);
+	spin_lock_irqsave(&iovad->iova_lock, flags);
 	remove_iova(iovad, iova);
-	spin_unlock_irqrestore(&iovad->iova_rbtree_lock, flags);
+	spin_unlock_irqrestore(&iovad->iova_lock, flags);
 	free_iova_mem(iova);
 }
 EXPORT_SYMBOL_GPL(__free_iova);
@@ -351,14 +218,14 @@ free_iova(struct iova_domain *iovad, unsigned long pfn)
 	unsigned long flags;
 	struct iova *iova;
 
-	spin_lock_irqsave(&iovad->iova_rbtree_lock, flags);
+	spin_lock_irqsave(&iovad->iova_lock, flags);
 	iova = private_find_iova(iovad, pfn);
 	if (!iova) {
-		spin_unlock_irqrestore(&iovad->iova_rbtree_lock, flags);
+		spin_unlock_irqrestore(&iovad->iova_lock, flags);
 		return;
 	}
 	remove_iova(iovad, iova);
-	spin_unlock_irqrestore(&iovad->iova_rbtree_lock, flags);
+	spin_unlock_irqrestore(&iovad->iova_lock, flags);
 	free_iova_mem(iova);
 }
 EXPORT_SYMBOL_GPL(free_iova);
@@ -445,27 +312,18 @@ static void iova_domain_free_rcaches(struct iova_domain *iovad)
  */
 void put_iova_domain(struct iova_domain *iovad)
 {
-	struct iova *iova, *tmp;
+	struct iova *iova;
+	MA_STATE(mas, &iovad->mtree, 0, 0);
 
 	if (iovad->rcaches)
 		iova_domain_free_rcaches(iovad);
 
-	rbtree_postorder_for_each_entry_safe(iova, tmp, &iovad->rbroot, node)
+	mas_for_each(&mas, iova, ULONG_MAX)
 		free_iova_mem(iova);
+	__mt_destroy(&iovad->mtree);
 }
 EXPORT_SYMBOL_GPL(put_iova_domain);
 
-static int
-__is_range_overlap(struct rb_node *node,
-	unsigned long pfn_lo, unsigned long pfn_hi)
-{
-	struct iova *iova = to_iova(node);
-
-	if ((pfn_lo <= iova->pfn_hi) && (pfn_hi >= iova->pfn_lo))
-		return 1;
-	return 0;
-}
-
 static inline struct iova *
 alloc_and_init_iova(unsigned long pfn_lo, unsigned long pfn_hi)
 {
@@ -480,29 +338,6 @@ alloc_and_init_iova(unsigned long pfn_lo, unsigned long pfn_hi)
 	return iova;
 }
 
-static struct iova *
-__insert_new_range(struct iova_domain *iovad,
-	unsigned long pfn_lo, unsigned long pfn_hi)
-{
-	struct iova *iova;
-
-	iova = alloc_and_init_iova(pfn_lo, pfn_hi);
-	if (iova)
-		iova_insert_rbtree(&iovad->rbroot, iova, NULL);
-
-	return iova;
-}
-
-static void
-__adjust_overlap_range(struct iova *iova,
-	unsigned long *pfn_lo, unsigned long *pfn_hi)
-{
-	if (*pfn_lo < iova->pfn_lo)
-		iova->pfn_lo = *pfn_lo;
-	if (*pfn_hi > iova->pfn_hi)
-		*pfn_lo = iova->pfn_hi + 1;
-}
-
 /**
  * reserve_iova - reserves an iova in the given range
  * @iovad: - iova domain pointer
@@ -510,41 +345,58 @@ __adjust_overlap_range(struct iova *iova,
  * @pfn_hi:- higher pfn address
  * This function allocates reserves the address range from pfn_lo to pfn_hi so
  * that this address is not dished out as part of alloc_iova.
+ *
+ * If the requested range overlaps existing reservations, ranges are merged.
+ * If the requested range is fully covered by an existing reservation, the
+ * existing entry is returned without allocating.
  */
 struct iova *
 reserve_iova(struct iova_domain *iovad,
 	unsigned long pfn_lo, unsigned long pfn_hi)
 {
-	struct rb_node *node;
 	unsigned long flags;
-	struct iova *iova;
-	unsigned int overlap = 0;
+	struct iova *iova, *overlap;
+	unsigned long merged_lo = pfn_lo, merged_hi = pfn_hi;
 
 	/* Don't allow nonsensical pfns */
 	if (WARN_ON((pfn_hi | pfn_lo) > (ULLONG_MAX >> iova_shift(iovad))))
 		return NULL;
 
-	spin_lock_irqsave(&iovad->iova_rbtree_lock, flags);
-	for (node = rb_first(&iovad->rbroot); node; node = rb_next(node)) {
-		if (__is_range_overlap(node, pfn_lo, pfn_hi)) {
-			iova = to_iova(node);
-			__adjust_overlap_range(iova, &pfn_lo, &pfn_hi);
-			if ((pfn_lo >= iova->pfn_lo) &&
-				(pfn_hi <= iova->pfn_hi))
-				goto finish;
-			overlap = 1;
-
-		} else if (overlap)
-				break;
+	spin_lock_irqsave(&iovad->iova_lock, flags);
+	{
+		MA_STATE(mas, &iovad->mtree, pfn_lo, pfn_hi);
+
+		mas_for_each(&mas, overlap, pfn_hi) {
+			if (pfn_lo >= overlap->pfn_lo &&
+			    pfn_hi <= overlap->pfn_hi) {
+				spin_unlock_irqrestore(&iovad->iova_lock,
+						       flags);
+				return overlap;
+			}
+			if (overlap->pfn_lo < merged_lo)
+				merged_lo = overlap->pfn_lo;
+			if (overlap->pfn_hi > merged_hi)
+				merged_hi = overlap->pfn_hi;
+			free_iova_mem(overlap);
+		}
 	}
 
-	/* We are here either because this is the first reserver node
-	 * or need to insert remaining non overlap addr range
-	 */
-	iova = __insert_new_range(iovad, pfn_lo, pfn_hi);
-finish:
+	iova = alloc_and_init_iova(merged_lo, merged_hi);
+	if (!iova) {
+		spin_unlock_irqrestore(&iovad->iova_lock, flags);
+		return NULL;
+	}
+
+	{
+		MA_STATE(mas, &iovad->mtree, merged_lo, merged_hi);
 
-	spin_unlock_irqrestore(&iovad->iova_rbtree_lock, flags);
+		if (mas_store_gfp(&mas, iova, GFP_ATOMIC)) {
+			spin_unlock_irqrestore(&iovad->iova_lock, flags);
+			free_iova_mem(iova);
+			return NULL;
+		}
+	}
+	spin_unlock_irqrestore(&iovad->iova_lock, flags);
 	return iova;
 }
 EXPORT_SYMBOL_GPL(reserve_iova);
@@ -621,7 +473,7 @@ iova_magazine_free_pfns(struct iova_magazine *mag, struct iova_domain *iovad)
 	unsigned long flags;
 	int i;
 
-	spin_lock_irqsave(&iovad->iova_rbtree_lock, flags);
+	spin_lock_irqsave(&iovad->iova_lock, flags);
 
 	for (i = 0 ; i < mag->size; ++i) {
 		struct iova *iova = private_find_iova(iovad, mag->pfns[i]);
@@ -633,7 +485,7 @@ iova_magazine_free_pfns(struct iova_magazine *mag, struct iova_domain *iovad)
 		free_iova_mem(iova);
 	}
 
-	spin_unlock_irqrestore(&iovad->iova_rbtree_lock, flags);
+	spin_unlock_irqrestore(&iovad->iova_lock, flags);
 
 	mag->size = 0;
 }
@@ -956,8 +808,8 @@ int iova_cache_get(void)
 
 	mutex_lock(&iova_cache_mutex);
 	if (!iova_cache_users) {
-		iova_cache = kmem_cache_create("iommu_iova", sizeof(struct iova), 0,
-					       SLAB_HWCACHE_ALIGN, NULL);
+		iova_cache = kmem_cache_create("iommu_iova", sizeof(struct iova),
+					       0, 0, NULL);
 		if (!iova_cache)
 			goto out_err;
 
diff --git a/include/linux/iova.h b/include/linux/iova.h
index d2c4fd923efa..eb4f9ead5451 100644
--- a/include/linux/iova.h
+++ b/include/linux/iova.h
@@ -11,12 +11,11 @@
 
 #include <linux/types.h>
 #include <linux/kernel.h>
-#include <linux/rbtree.h>
+#include <linux/maple_tree.h>
 #include <linux/dma-mapping.h>
 
 /* iova structure */
 struct iova {
-	struct rb_node	node;
 	unsigned long	pfn_hi; /* Highest allocated pfn */
 	unsigned long	pfn_lo; /* Lowest allocated pfn */
 };
@@ -26,15 +25,12 @@ struct iova_rcache;
 
 /* holds all the iova translations for a domain */
 struct iova_domain {
-	spinlock_t	iova_rbtree_lock; /* Lock to protect update of rbtree */
-	struct rb_root	rbroot;		/* iova domain rbtree root */
-	struct rb_node	*cached_node;	/* Save last alloced node */
-	struct rb_node	*cached32_node; /* Save last 32-bit alloced node */
+	spinlock_t	iova_lock;	/* Lock to protect update of maple tree */
+	struct maple_tree	mtree;
 	unsigned long	granule;	/* pfn granularity for this domain */
 	unsigned long	start_pfn;	/* Lower limit for this domain */
 	unsigned long	dma_32bit_pfn;
 	unsigned long	max32_alloc_size; /* Size of last failed allocation */
-	struct iova	anchor;		/* rbtree lookup anchor */
 
 	struct iova_rcache	*rcaches;
 	struct hlist_node	cpuhp_dead;
-- 
2.54.0