[PATCHv3 04/41] radix-tree: Add radix_tree_split

Kirill A. Shutemov
2016-09-15T11:54:46Z

From: Matthew Wilcox <willy@linux.intel.com>

This new function splits a larger multiorder entry into smaller entries
(potentially multi-order entries). These entries are initialised to
RADIX_TREE_RETRY to ensure that RCU walkers who see this state aren't
confused. The caller should then call radix_tree_for_each_slot() and
radix_tree_replace_slot() in order to turn these retry entries into the
intended new entries. Tags are replicated from the original multiorder
entry into each new entry.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
include/linux/radix-tree.h | 6 +-
lib/radix-tree.c | 109 ++++++++++++++++++++++++++++++++--
tools/testing/radix-tree/multiorder.c | 26 ++++++++
3 files changed, 135 insertions(+), 6 deletions(-)

diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h
index 75ae4648d13d..459e8a152c8a 100644
--- a/include/linux/radix-tree.h
+++ b/include/linux/radix-tree.h
@@ -280,8 +280,7 @@ bool __radix_tree_delete_node(struct radix_tree_root *root,
struct radix_tree_node *node);
void *radix_tree_delete_item(struct radix_tree_root *, unsigned long, void *);
void *radix_tree_delete(struct radix_tree_root *, unsigned long);
-struct radix_tree_node *radix_tree_replace_clear_tags(
- struct radix_tree_root *root,
+struct radix_tree_node *radix_tree_replace_clear_tags(struct radix_tree_root *,
unsigned long index, void *entry);
unsigned int radix_tree_gang_lookup(struct radix_tree_root *root,
void **results, unsigned long first_index,
@@ -319,8 +318,11 @@ static inline void radix_tree_preload_end(void)
preempt_enable();
}

+int radix_tree_split(struct radix_tree_root *, unsigned long index,
+ unsigned new_order);
int radix_tree_join(struct radix_tree_root *, unsigned long index,
unsigned new_order, void *);
+
/**
* struct radix_tree_iter - radix tree iterator state
*
diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 3157f223c268..ad3116cbe61b 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -231,7 +231,10 @@ static void dump_node(struct radix_tree_node *node, unsigned long index)
void *entry = node->slots[i];
if (!entry)
continue;
- if (is_sibling_entry(node, entry)) {
+ if (entry == RADIX_TREE_RETRY) {
+ pr_debug("radix retry offset %ld indices %ld-%ld\n",
+ i, first, last);
+ } else if (is_sibling_entry(node, entry)) {
pr_debug("radix sblng %p offset %ld val %p indices %ld-%ld\n",
entry, i,
*(void **)entry_to_node(entry),
@@ -641,7 +644,10 @@ static inline int insert_entries(struct radix_tree_node *node, void **slot,
unsigned i, n, tag, offset, tags = 0;

if (node) {
- n = 1 << (order - node->shift);
+ if (order > node->shift)
+ n = 1 << (order - node->shift);
+ else
+ n = 1;
offset = get_slot_offset(node, slot);
} else {
n = 1;
@@ -680,7 +686,8 @@ static inline int insert_entries(struct radix_tree_node *node, void **slot,
tag_set(node, tag, offset);
}
if (radix_tree_is_internal_node(old) &&
- !is_sibling_entry(node, old))
+ !is_sibling_entry(node, old) &&
+ (old != RADIX_TREE_RETRY))
radix_tree_free_nodes(old);
}
if (node)
@@ -843,6 +850,98 @@ int radix_tree_join(struct radix_tree_root *root, unsigned long index,

return error;
}
+
+int radix_tree_split(struct radix_tree_root *root, unsigned long index,
+ unsigned order)
+{
+ struct radix_tree_node *parent, *node, *child;
+ void **slot;
+ unsigned int offset, end;
+ unsigned n, tag, tags = 0;
+
+ if (!__radix_tree_lookup(root, index, &parent, &slot))
+ return -ENOENT;
+ if (!parent)
+ return -ENOENT;
+
+ offset = get_slot_offset(parent, slot);
+
+ for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++)
+ if (tag_get(parent, tag, offset))
+ tags |= 1 << tag;
+
+ for (end = offset + 1; end < RADIX_TREE_MAP_SIZE; end++) {
+ if (!is_sibling_entry(parent, parent->slots[end]))
+ break;
+ for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++)
+ if (tags & (1 << tag))
+ tag_set(parent, tag, end);
+ /* tags must be set before RETRY is set */
+ rcu_assign_pointer(parent->slots[end], RADIX_TREE_RETRY);
+ }
+
+ if (order == parent->shift)
+ return 0;
+ if (order > parent->shift) {
+ while (offset < end)
+ offset += insert_entries(parent, &parent->slots[offset],
+ RADIX_TREE_RETRY, order, true);
+ return 0;
+ }
+
+ node = parent;
+
+ for (;;) {
+ if (node->shift > order) {
+ child = radix_tree_node_alloc(root);
+ if (!child)
+ goto nomem;
+ child->shift = node->shift - RADIX_TREE_MAP_SHIFT;
+ child->offset = offset;
+ child->count = 0;
+ child->parent = node;
+ if (node != parent) {
+ node->count++;
+ node->slots[offset] = node_to_entry(child);
+ for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++)
+ if (tags & (1 << tag))
+ tag_set(node, tag, offset);
+ }
+
+ node = child;
+ offset = 0;
+ continue;
+ }
+
+ n = insert_entries(node, &node->slots[offset],
+ RADIX_TREE_RETRY, order, false);
+ BUG_ON(n > RADIX_TREE_MAP_SIZE);
+
+ for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++)
+ if (tags & (1 << tag))
+ tag_set(node, tag, offset);
+ offset += n;
+
+ while (offset == RADIX_TREE_MAP_SIZE) {
+ if (node == parent)
+ break;
+ offset = node->offset;
+ child = node;
+ node = node->parent;
+ rcu_assign_pointer(node->slots[offset],
+ node_to_entry(child));
+ offset++;
+ }
+ if ((node == parent) && (offset == end))
+ return 0;
+ }
+
+ nomem:
+ /* Shouldn't happen; did user forget to preload? */
+ /* TODO: free all the allocated nodes */
+ WARN_ON(1);
+ return -ENOMEM;
+}
#endif

/**
@@ -1081,8 +1180,10 @@ void **radix_tree_next_chunk(struct radix_tree_root *root,
child = rcu_dereference_raw(node->slots[offset]);
}

- if ((child == NULL) || (child == RADIX_TREE_RETRY))
+ if (!child)
goto restart;
+ if (child == RADIX_TREE_RETRY)
+ break;
} while (radix_tree_is_internal_node(child));

/* Update the iterator state */
diff --git a/tools/testing/radix-tree/multiorder.c b/tools/testing/radix-tree/multiorder.c
index f917da164b00..9d27a4dd7b2a 100644
--- a/tools/testing/radix-tree/multiorder.c
+++ b/tools/testing/radix-tree/multiorder.c
@@ -348,6 +348,31 @@ static void multiorder_join(void)
}
}

+static void __multiorder_split(int old_order, int new_order)
+{
+ RADIX_TREE(tree, GFP_KERNEL);
+ void **slot;
+ struct radix_tree_iter iter;
+
+ item_insert_order(&tree, 0, old_order);
+ radix_tree_tag_set(&tree, 0, 2);
+ radix_tree_split(&tree, 0, new_order);
+ radix_tree_for_each_slot(slot, &tree, &iter, 0) {
+ radix_tree_replace_slot(slot, item_create(iter.index));
+ }
+
+ item_kill_tree(&tree);
+}
+
+static void multiorder_split(void)
+{
+ int i, j;
+
+ for (i = 9; i < 19; i++)
+ for (j = 0; j < i; j++)
+ __multiorder_split(i, j);
+}
+
void multiorder_checks(void)
{
int i;
@@ -366,4 +391,5 @@ void multiorder_checks(void)
multiorder_iteration();
multiorder_tagged_iteration();
multiorder_join();
+ multiorder_split();
}