On Wed, Jul 23, 2025 at 6:35 AM Vlastimil Babka <vbabka@suse.cz> wrote:
>
> From: "Liam R. Howlett" <Liam.Howlett@Oracle.com>
>
> Use the generic interface which should result in less bulk allocations
> during a forking.
>
> A part of this is to abstract the freeing of the sheaf or maple state
> allocations into its own function so mas_destroy() and the tree
> duplication code can use the same functionality to return any unused
> resources.
>
> Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
> ---
> lib/maple_tree.c | 42 +++++++++++++++++++++++-------------------
> 1 file changed, 23 insertions(+), 19 deletions(-)
>
> diff --git a/lib/maple_tree.c b/lib/maple_tree.c
> index 9aa782b1497f224e7366ebbd65f997523ee0c8ab..180d5e2ea49440248aaae04a066276406b2537ed 100644
> --- a/lib/maple_tree.c
> +++ b/lib/maple_tree.c
> @@ -1178,6 +1178,19 @@ static inline void mas_alloc_nodes(struct ma_state *mas, gfp_t gfp)
> mas_set_err(mas, -ENOMEM);
> }
>
> +static inline void mas_empty_nodes(struct ma_state *mas)
> +{
> + mas->node_request = 0;
> + if (mas->sheaf) {
> + mt_return_sheaf(mas->sheaf);
> + mas->sheaf = NULL;
> + }
> +
> + if (mas->alloc) {
> + mt_free_one(mas->alloc);
> + mas->alloc = NULL;
> + }
> +}
>
> /*
> * mas_free() - Free an encoded maple node
> @@ -5414,15 +5427,7 @@ void mas_destroy(struct ma_state *mas)
> mas->mas_flags &= ~MA_STATE_REBALANCE;
> }
> mas->mas_flags &= ~(MA_STATE_BULK|MA_STATE_PREALLOC);
> -
> - mas->node_request = 0;
> - if (mas->sheaf)
> - mt_return_sheaf(mas->sheaf);
> - mas->sheaf = NULL;
> -
> - if (mas->alloc)
> - mt_free_one(mas->alloc);
> - mas->alloc = NULL;
> + mas_empty_nodes(mas);
> }
> EXPORT_SYMBOL_GPL(mas_destroy);
>
> @@ -6499,7 +6504,7 @@ static inline void mas_dup_alloc(struct ma_state *mas, struct ma_state *new_mas,
> struct maple_node *node = mte_to_node(mas->node);
> struct maple_node *new_node = mte_to_node(new_mas->node);
> enum maple_type type;
> - unsigned char request, count, i;
> + unsigned char count, i;
> void __rcu **slots;
> void __rcu **new_slots;
> unsigned long val;
> @@ -6507,20 +6512,17 @@ static inline void mas_dup_alloc(struct ma_state *mas, struct ma_state *new_mas,
> /* Allocate memory for child nodes. */
> type = mte_node_type(mas->node);
> new_slots = ma_slots(new_node, type);
> - request = mas_data_end(mas) + 1;
> - count = mt_alloc_bulk(gfp, request, (void **)new_slots);
> - if (unlikely(count < request)) {
> - memset(new_slots, 0, request * sizeof(void *));
> - mas_set_err(mas, -ENOMEM);
> + count = mas->node_request = mas_data_end(mas) + 1;
> + mas_alloc_nodes(mas, gfp);
> + if (unlikely(mas_is_err(mas)))
> return;
> - }
>
> - /* Restore node type information in slots. */
> slots = ma_slots(node, type);
> for (i = 0; i < count; i++) {
> val = (unsigned long)mt_slot_locked(mas->tree, slots, i);
> val &= MAPLE_NODE_MASK;
> - ((unsigned long *)new_slots)[i] |= val;
> + new_slots[i] = ma_mnode_ptr((unsigned long)mas_pop_node(mas) |
> + val);
> }
> }
>
> @@ -6574,7 +6576,7 @@ static inline void mas_dup_build(struct ma_state *mas, struct ma_state *new_mas,
> /* Only allocate child nodes for non-leaf nodes. */
> mas_dup_alloc(mas, new_mas, gfp);
> if (unlikely(mas_is_err(mas)))
> - return;
> + goto empty_mas;
> } else {
> /*
> * This is the last leaf node and duplication is
> @@ -6607,6 +6609,8 @@ static inline void mas_dup_build(struct ma_state *mas, struct ma_state *new_mas,
> /* Make them the same height */
> new_mas->tree->ma_flags = mas->tree->ma_flags;
> rcu_assign_pointer(new_mas->tree->ma_root, root);
> +empty_mas:
> + mas_empty_nodes(mas);
> }
>
> /**
>
> --
> 2.50.1
>