Introduce interfaces __mt_dup() and mt_dup(), which are used to duplicate a maple tree. Compared with traversing the source tree and reinserting entry by entry in the new tree, it has better performance. The difference between __mt_dup() and mt_dup() is that mt_dup() holds an internal lock. Signed-off-by: Peng Zhang <zhangpeng.00@xxxxxxxxxxxxx> --- include/linux/maple_tree.h | 3 + lib/maple_tree.c | 211 +++++++++++++++++++++++++++++++++++++ 2 files changed, 214 insertions(+) diff --git a/include/linux/maple_tree.h b/include/linux/maple_tree.h index c962af188681..229fe78e4c89 100644 --- a/include/linux/maple_tree.h +++ b/include/linux/maple_tree.h @@ -327,6 +327,9 @@ int mtree_store(struct maple_tree *mt, unsigned long index, void *entry, gfp_t gfp); void *mtree_erase(struct maple_tree *mt, unsigned long index); +int mt_dup(struct maple_tree *mt, struct maple_tree *new, gfp_t gfp); +int __mt_dup(struct maple_tree *mt, struct maple_tree *new, gfp_t gfp); + void mtree_destroy(struct maple_tree *mt); void __mt_destroy(struct maple_tree *mt); diff --git a/lib/maple_tree.c b/lib/maple_tree.c index da3a2fb405c0..efac6761ae37 100644 --- a/lib/maple_tree.c +++ b/lib/maple_tree.c @@ -6595,6 +6595,217 @@ void *mtree_erase(struct maple_tree *mt, unsigned long index) } EXPORT_SYMBOL(mtree_erase); +/* + * mt_dup_free() - Free the nodes of a incomplete maple tree. + * @mt: The incomplete maple tree + * @node: Free nodes from @node + * + * This function frees all nodes starting from @node in the reverse order of + * mt_dup_build(). At this point we don't need to hold the source tree lock. + */ +static void mt_dup_free(struct maple_tree *mt, struct maple_node *node) +{ + void **slots; + unsigned char offset; + struct maple_enode *enode; + enum maple_type type; + unsigned char count = 0, i; + +try_ascend: + if (ma_is_root(node)) { + mt_free_one(node); + return; + } + + offset = ma_parent_slot(node); + type = ma_parent_type(mt, node); + node = ma_parent(node); + if (!offset) + goto free; + + offset--; + +descend: + slots = (void **)ma_slots(node, type); + enode = slots[offset]; + if (mte_is_leaf(enode)) + goto free; + + type = mte_node_type(enode); + node = mte_to_node(enode); + offset = ma_nonleaf_data_end_nocheck(node, type); + goto descend; + +free: + slots = (void **)ma_slots(node, type); + count = ma_nonleaf_data_end_nocheck(node, type) + 1; + for (i = 0; i < count; i++) + ((unsigned long *)slots)[i] &= ~MAPLE_NODE_MASK; + + /* Cast to __rcu to avoid sparse checker complaining. */ + mt_free_bulk(count, (void __rcu **)slots); + goto try_ascend; +} + +/* + * mt_dup_build() - Build a new maple tree from a source tree + * @mt: The source maple tree to copy from + * @new: The new maple tree + * @gfp: The GFP_FLAGS to use for allocations + * @to_free: Free nodes starting from @to_free if the build fails + * + * This function builds a new tree in DFS preorder. If it fails due to memory + * allocation, @to_free will store the last failed node to free the incomplete + * tree. Use mt_dup_free() to free nodes. + * + * Return: 0 on success, -ENOMEM if memory could not be allocated. + */ +static inline int mt_dup_build(struct maple_tree *mt, struct maple_tree *new, + gfp_t gfp, struct maple_node **to_free) +{ + struct maple_enode *enode; + struct maple_node *new_node, *new_parent = NULL, *node; + enum maple_type type; + void __rcu **slots; + void **new_slots; + unsigned char count, request, i, offset; + unsigned long *set_parent; + unsigned long new_root; + + mt_init_flags(new, mt->ma_flags); + enode = mt_root_locked(mt); + if (unlikely(!xa_is_node(enode))) { + rcu_assign_pointer(new->ma_root, enode); + return 0; + } + + new_node = mt_alloc_one(gfp); + if (!new_node) + return -ENOMEM; + + new_root = (unsigned long)new_node; + new_root |= (unsigned long)enode & MAPLE_NODE_MASK; + +copy_node: + node = mte_to_node(enode); + type = mte_node_type(enode); + memcpy(new_node, node, sizeof(struct maple_node)); + + set_parent = (unsigned long *)&(new_node->parent); + *set_parent &= MAPLE_NODE_MASK; + *set_parent |= (unsigned long)new_parent; + if (ma_is_leaf(type)) + goto ascend; + + new_slots = (void **)ma_slots(new_node, type); + slots = ma_slots(node, type); + request = ma_nonleaf_data_end(mt, node, type) + 1; + count = mt_alloc_bulk(gfp, request, new_slots); + if (!count) { + *to_free = new_node; + return -ENOMEM; + } + + for (i = 0; i < count; i++) + ((unsigned long *)new_slots)[i] |= + ((unsigned long)mt_slot_locked(mt, slots, i) & + MAPLE_NODE_MASK); + offset = 0; + +descend: + new_parent = new_node; + enode = mt_slot_locked(mt, slots, offset); + new_node = mte_to_node(new_slots[offset]); + goto copy_node; + +ascend: + if (ma_is_root(node)) { + new_node = mte_to_node((void *)new_root); + new_node->parent = ma_parent_ptr((unsigned long)new | + MA_ROOT_PARENT); + rcu_assign_pointer(new->ma_root, (void *)new_root); + return 0; + } + + offset = ma_parent_slot(node); + type = ma_parent_type(mt, node); + node = ma_parent(node); + new_node = ma_parent(new_node); + if (offset < ma_nonleaf_data_end(mt, node, type)) { + offset++; + new_slots = (void **)ma_slots(new_node, type); + slots = ma_slots(node, type); + goto descend; + } + + goto ascend; +} + +/** + * __mt_dup(): Duplicate a maple tree + * @mt: The source maple tree + * @new: The new maple tree + * @gfp: The GFP_FLAGS to use for allocations + * + * This function duplicates a maple tree using a faster method than traversing + * the source tree and inserting entries into the new tree one by one. The user + * needs to lock the source tree manually. Before calling this function, @new + * must be an empty tree or an uninitialized tree. If @mt uses an external lock, + * we may also need to manually set @new's external lock using + * mt_set_external_lock(). + * + * Return: 0 on success, -ENOMEM if memory could not be allocated. + */ +int __mt_dup(struct maple_tree *mt, struct maple_tree *new, gfp_t gfp) +{ + int ret; + struct maple_node *to_free = NULL; + + ret = mt_dup_build(mt, new, gfp, &to_free); + + if (unlikely(ret == -ENOMEM)) { + if (to_free) + mt_dup_free(new, to_free); + } + + return ret; +} +EXPORT_SYMBOL(__mt_dup); + +/** + * mt_dup(): Duplicate a maple tree + * @mt: The source maple tree + * @new: The new maple tree + * @gfp: The GFP_FLAGS to use for allocations + * + * This function duplicates a maple tree using a faster method than traversing + * the source tree and inserting entries into the new tree one by one. The + * function will lock the source tree with an internal lock, and the user does + * not need to manually handle the lock. Before calling this function, @new must + * be an empty tree or an uninitialized tree. If @mt uses an external lock, we + * may also need to manually set @new's external lock using + * mt_set_external_lock(). + * + * Return: 0 on success, -ENOMEM if memory could not be allocated. + */ +int mt_dup(struct maple_tree *mt, struct maple_tree *new, gfp_t gfp) +{ + int ret; + struct maple_node *to_free = NULL; + + mtree_lock(mt); + ret = mt_dup_build(mt, new, gfp, &to_free); + mtree_unlock(mt); + + if (unlikely(ret == -ENOMEM)) { + if (to_free) + mt_dup_free(new, to_free); + } + + return ret; +} +EXPORT_SYMBOL(mt_dup); + /** * __mt_destroy() - Walk and free all nodes of a locked maple tree. * @mt: The maple tree -- 2.20.1