The patch titled
Subject: maple_tree: introduce mas_wr_store_type()
has been added to the -mm mm-unstable branch. Its filename is
maple_tree-introduce-mas_wr_store_type.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/maple_tree-introduce-mas_wr_store_type.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Sidhartha Kumar <sidhartha.kumar@xxxxxxxxxx>
Subject: maple_tree: introduce mas_wr_store_type()
Date: Wed, 14 Aug 2024 12:19:31 -0400
Introduce mas_wr_store_type() which will set the correct store type based
on a walk of the tree. In mas_wr_node_store() the <= min_slots condition
is changed to < as if new_end is = to mt_min_slots then there is not
enough room.
mas_prealloc_calc() is also introduced to abstract the calculation used to
determine the number of nodes needed for a store operation.
In this change a call to mas_reset() is removed in the error case of
mas_prealloc(). This is only needed in the MA_STATE_REBALANCE case of
mas_destroy(). We can move the call to mas_reset() directly to
mas_destroy().
Also, add a test case to validate the order that we check the store type
in is correct. This test models a vma expanding and then shrinking which
is part of the boot process.
Link: https://lkml.kernel.org/r/20240814161944.55347-5-sidhartha.kumar@xxxxxxxxxx
Signed-off-by: Sidhartha Kumar <sidhartha.kumar@xxxxxxxxxx>
Cc: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
lib/maple_tree.c | 217 ++++++++++++++++++++---------
tools/testing/radix-tree/maple.c | 36 ++++
2 files changed, 193 insertions(+), 60 deletions(-)
--- a/lib/maple_tree.c~maple_tree-introduce-mas_wr_store_type
+++ a/lib/maple_tree.c
@@ -1372,9 +1372,9 @@ retry:
return NULL;
}
+ mas->node = NULL;
/* empty tree */
if (unlikely(!root)) {
- mas->node = NULL;
mas->status = ma_none;
mas->offset = MAPLE_NODE_SLOTS;
return NULL;
@@ -3890,7 +3890,7 @@ static inline bool mas_wr_node_store(str
bool in_rcu = mt_in_rcu(mas->tree);
/* Check if there is enough data. The room is enough. */
- if (!mte_is_root(mas->node) && (new_end <= mt_min_slots[wr_mas->type]) &&
+ if (!mte_is_root(mas->node) && (new_end < mt_min_slots[wr_mas->type]) &&
!(mas->mas_flags & MA_STATE_BULK))
return false;
@@ -4276,6 +4276,146 @@ static inline void mas_wr_prealloc_setup
}
/**
+ * mas_prealloc_calc() - Calculate number of nodes needed for a
+ * given store oepration
+ * @mas: The maple state
+ * @entry: The entry to store into the tree
+ *
+ * Return: Number of nodes required for preallocation.
+ */
+static inline int mas_prealloc_calc(struct ma_state *mas, void *entry)
+{
+ int ret = mas_mt_height(mas) * 3 + 1;
+
+ switch (mas->store_type) {
+ case wr_invalid:
+ WARN_ON_ONCE(1);
+ break;
+ case wr_new_root:
+ ret = 1;
+ break;
+ case wr_store_root:
+ if (likely((mas->last != 0) || (mas->index != 0)))
+ ret = 1;
+ else if (((unsigned long) (entry) & 3) == 2)
+ ret = 1;
+ else
+ ret = 0;
+ break;
+ case wr_spanning_store:
+ ret = mas_mt_height(mas) * 3 + 1;
+ break;
+ case wr_split_store:
+ ret = mas_mt_height(mas) * 2 + 1;
+ break;
+ case wr_rebalance:
+ ret = mas_mt_height(mas) * 2 - 1;
+ break;
+ case wr_node_store:
+ ret = mt_in_rcu(mas->tree) ? 1 : 0;
+ break;
+ case wr_append:
+ case wr_exact_fit:
+ case wr_slot_store:
+ ret = 0;
+ }
+
+ return ret;
+}
+
+/*
+ * mas_wr_store_type() - Set the store type for a given
+ * store operation.
+ * @wr_mas: The maple write state
+ */
+static inline void mas_wr_store_type(struct ma_wr_state *wr_mas)
+{
+ struct ma_state *mas = wr_mas->mas;
+ unsigned char new_end;
+
+ if (unlikely(mas_is_none(mas) || mas_is_ptr(mas))) {
+ mas->store_type = wr_store_root;
+ return;
+ }
+
+ if (unlikely(!mas_wr_walk(wr_mas))) {
+ mas->store_type = wr_spanning_store;
+ return;
+ }
+
+ /* At this point, we are at the leaf node that needs to be altered. */
+ mas_wr_end_piv(wr_mas);
+ if (!wr_mas->entry)
+ mas_wr_extend_null(wr_mas);
+
+ new_end = mas_wr_new_end(wr_mas);
+ if ((wr_mas->r_min == mas->index) && (wr_mas->r_max == mas->last)) {
+ mas->store_type = wr_exact_fit;
+ return;
+ }
+
+ if (unlikely(!mas->index && mas->last == ULONG_MAX)) {
+ mas->store_type = wr_new_root;
+ return;
+ }
+
+ /* Potential spanning rebalance collapsing a node */
+ if (new_end < mt_min_slots[wr_mas->type]) {
+ if (!mte_is_root(mas->node)) {
+ mas->store_type = wr_rebalance;
+ return;
+ }
+ mas->store_type = wr_node_store;
+ return;
+ }
+
+ if (new_end >= mt_slots[wr_mas->type]) {
+ mas->store_type = wr_split_store;
+ return;
+ }
+
+ if (!mt_in_rcu(mas->tree) && (mas->offset == mas->end)) {
+ mas->store_type = wr_append;
+ return;
+ }
+
+ if ((new_end == mas->end) && (!mt_in_rcu(mas->tree) ||
+ (wr_mas->offset_end - mas->offset == 1))) {
+ mas->store_type = wr_slot_store;
+ return;
+ }
+
+ if (mte_is_root(mas->node) || (new_end >= mt_min_slots[wr_mas->type]) ||
+ (mas->mas_flags & MA_STATE_BULK)) {
+ mas->store_type = wr_node_store;
+ return;
+ }
+
+ mas->store_type = wr_invalid;
+ MAS_WARN_ON(mas, 1);
+}
+
+/**
+ * mas_wr_preallocate() - Preallocate enough nodes for a store operation
+ * @wr_mas: The maple write state
+ * @entry: The entry that will be stored
+ *
+ */
+static inline void mas_wr_preallocate(struct ma_wr_state *wr_mas, void *entry)
+{
+ struct ma_state *mas = wr_mas->mas;
+ int request;
+
+ mas_wr_prealloc_setup(wr_mas);
+ mas_wr_store_type(wr_mas);
+ request = mas_prealloc_calc(mas, entry);
+ if (!request)
+ return;
+
+ mas_node_count(mas, request);
+}
+
+/**
* mas_insert() - Internal call to insert a value
* @mas: The maple state
* @entry: The entry to store
@@ -5508,69 +5648,25 @@ EXPORT_SYMBOL_GPL(mas_store_prealloc);
int mas_preallocate(struct ma_state *mas, void *entry, gfp_t gfp)
{
MA_WR_STATE(wr_mas, mas, entry);
- unsigned char node_size;
- int request = 1;
- int ret;
-
-
- if (unlikely(!mas->index && mas->last == ULONG_MAX))
- goto ask_now;
+ int ret = 0;
+ int request;
mas_wr_prealloc_setup(&wr_mas);
- /* Root expand */
- if (unlikely(mas_is_none(mas) || mas_is_ptr(mas)))
- goto ask_now;
+ mas_wr_store_type(&wr_mas);
+ request = mas_prealloc_calc(mas, entry);
+ if (!request)
+ return ret;
- if (unlikely(!mas_wr_walk(&wr_mas))) {
- /* Spanning store, use worst case for now */
- request = 1 + mas_mt_height(mas) * 3;
- goto ask_now;
+ mas_node_count_gfp(mas, request, gfp);
+ if (mas_is_err(mas)) {
+ mas_set_alloc_req(mas, 0);
+ ret = xa_err(mas->node);
+ mas_destroy(mas);
+ mas_reset(mas);
+ return ret;
}
- /* At this point, we are at the leaf node that needs to be altered. */
- /* Exact fit, no nodes needed. */
- if (wr_mas.r_min == mas->index && wr_mas.r_max == mas->last)
- return 0;
-
- mas_wr_end_piv(&wr_mas);
- node_size = mas_wr_new_end(&wr_mas);
-
- /* Slot store, does not require additional nodes */
- if (node_size == mas->end) {
- /* reuse node */
- if (!mt_in_rcu(mas->tree))
- return 0;
- /* shifting boundary */
- if (wr_mas.offset_end - mas->offset == 1)
- return 0;
- }
-
- if (node_size >= mt_slots[wr_mas.type]) {
- /* Split, worst case for now. */
- request = 1 + mas_mt_height(mas) * 2;
- goto ask_now;
- }
-
- /* New root needs a single node */
- if (unlikely(mte_is_root(mas->node)))
- goto ask_now;
-
- /* Potential spanning rebalance collapsing a node, use worst-case */
- if (node_size - 1 <= mt_min_slots[wr_mas.type])
- request = mas_mt_height(mas) * 2 - 1;
-
- /* node store, slot store needs one node */
-ask_now:
- mas_node_count_gfp(mas, request, gfp);
mas->mas_flags |= MA_STATE_PREALLOC;
- if (likely(!mas_is_err(mas)))
- return 0;
-
- mas_set_alloc_req(mas, 0);
- ret = xa_err(mas->node);
- mas_reset(mas);
- mas_destroy(mas);
- mas_reset(mas);
return ret;
}
EXPORT_SYMBOL_GPL(mas_preallocate);
@@ -5596,7 +5692,8 @@ void mas_destroy(struct ma_state *mas)
*/
if (mas->mas_flags & MA_STATE_REBALANCE) {
unsigned char end;
-
+ if (mas_is_err(mas))
+ mas_reset(mas);
mas_start(mas);
mtree_range_walk(mas);
end = mas->end + 1;
--- a/tools/testing/radix-tree/maple.c~maple_tree-introduce-mas_wr_store_type
+++ a/tools/testing/radix-tree/maple.c
@@ -36283,6 +36283,38 @@ static void check_nomem_writer_race(stru
mtree_unlock(mt);
}
+ /* test to simulate expanding a vma from [0x7fffffffe000, 0x7ffffffff000)
+ * to [0x7ffde4ca1000, 0x7ffffffff000) and then shrinking the vma to
+ * [0x7ffde4ca1000, 0x7ffde4ca2000)
+ */
+static inline int check_vma_modification(struct maple_tree *mt)
+{
+ MA_STATE(mas, mt, 0, 0);
+
+ mtree_lock(mt);
+ /* vma with old start and old end */
+ __mas_set_range(&mas, 0x7fffffffe000, 0x7ffffffff000 - 1);
+ mas_preallocate(&mas, xa_mk_value(1), GFP_KERNEL);
+ mas_store_prealloc(&mas, xa_mk_value(1));
+
+ /* next write occurs partly in previous range [0, 0x7fffffffe000)*/
+ mas_prev_range(&mas, 0);
+ /* expand vma to {0x7ffde4ca1000, 0x7ffffffff000) */
+ __mas_set_range(&mas, 0x7ffde4ca1000, 0x7ffffffff000 - 1);
+ mas_preallocate(&mas, xa_mk_value(1), GFP_KERNEL);
+ mas_store_prealloc(&mas, xa_mk_value(1));
+
+ /* shrink vma to [0x7ffde4ca1000, 7ffde4ca2000) */
+ __mas_set_range(&mas, 0x7ffde4ca2000, 0x7ffffffff000 - 1);
+ mas_preallocate(&mas, NULL, GFP_KERNEL);
+ mas_store_prealloc(&mas, NULL);
+ mt_dump(mt, mt_dump_hex);
+
+ mas_destroy(&mas);
+ mtree_unlock(mt);
+ return 0;
+}
+
void farmer_tests(void)
{
struct maple_node *node;
@@ -36290,6 +36322,10 @@ void farmer_tests(void)
mt_dump(&tree, mt_dump_dec);
+ mt_init_flags(&tree, MT_FLAGS_ALLOC_RANGE | MT_FLAGS_LOCK_EXTERN | MT_FLAGS_USE_RCU);
+ check_vma_modification(&tree);
+ mtree_destroy(&tree);
+
tree.ma_root = xa_mk_value(0);
mt_dump(&tree, mt_dump_dec);
_
Patches currently in -mm which might be from sidhartha.kumar@xxxxxxxxxx are
maple_tree-reset-mas-index-and-mas-last-on-write-retries.patch
maple_tree-add-test-to-replicate-low-memory-race-conditions.patch
maple_tree-introduce-store_type-enum.patch
maple_tree-introduce-mas_wr_prealloc_setup.patch
maple_tree-move-up-mas_wr_store_setup-and-mas_wr_prealloc_setup.patch
maple_tree-introduce-mas_wr_store_type.patch
maple_tree-remove-mas_destroy-from-mas_nomem.patch
maple_tree-preallocate-nodes-in-mas_erase.patch
maple_tree-use-mas_store_gfp-in-mtree_store_range.patch
maple_tree-print-store-type-in-mas_dump.patch
maple_tree-use-store-type-in-mas_wr_store_entry.patch
maple_tree-convert-mas_insert-to-preallocate-nodes.patch
maple_tree-simplify-mas_commit_b_node.patch
maple_tree-remove-mas_wr_modify.patch
maple_tree-have-mas_store-allocate-nodes-if-needed.patch
maple_tree-remove-node-allocations-from-various-write-helper-functions.patch
maple_tree-remove-repeated-sanity-checks-from-write-helper-functions.patch
maple_tree-remove-unneeded-mas_wr_walk-in-mas_store_prealloc.patch
maple_tree-make-write-helper-functions-void.patch
