* Peng Zhang <zhangpeng.00@xxxxxxxxxxxxx> [230726 04:10]:
> 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;
> +
Can we make these labels inline functions and try to make this a loop?
> +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)
I am trying to change the functions to be two tabs of indent for
arguments from now on. It allows for more to fit on a single line and
still maintains a clear separation between code and argument lists.
> +{
> + 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:
Can you make copy_node, descend, ascend inline functions instead of the
goto jumping please? It's better to have loops over jumping around a
lot. Gotos are good for undoing things and retry, but constructing
loops with them makes it difficult to follow.
> + 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;
Maybe make a small inline to set the parent instead of this?
There are some defined helpers for setting the types like
ma_parent_ptr() and ma_enode_ptr() to make casting more type-safe.
> + 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)
We use mas_ for things that won't handle the locking and pass in a maple
state. Considering the leaves need to be altered once this is returned,
I would expect passing in a maple state should be feasible?
> +{
> + int ret;
> + struct maple_node *to_free = NULL;
> +
> + ret = mt_dup_build(mt, new, gfp, &to_free);
> +
> + if (unlikely(ret == -ENOMEM)) {
On other errors, will the half constructed tree be returned? Is this
safe?
> + 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)
mtree_ ususually used to indicate locking is handled.
> +{
> + 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);
Again, is a half constructed tree safe to return? Since each caller
checks to_free is NULL, could that be in mt_dup_free() instead?
> + }
> +
> + 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
>
>
