[PATCH v4 00/17] Introduce a store type enum for the Maple tree

[Sidhartha Kumar]

v3[1] -> v4:
    - move up mas->node = null in mas_start() so mas->node is cleared in all cases.
    - don't pass gfp into mas_wr_preallocate().This fixes the libfs error reported in v3[2].
    - change condition of node store so more writes can be eligible node stores.
    - more cleanup of mas_commit_b_node() as most of the function becomes dead code.
    - remove wr_bnode as a store type as it is no longer needed.
    - add a patch to change many write helper functions to be void.

================================ OVERVIEW ================================

This series implements two work items[3]: "aligning mas_store_gfp() with
mas_preallocate()" and "enum for store type".

mas_store_gfp() is modified to preallocate nodes. This simplies many of
the write helper functions by allowing them to use mas_store_gfp() rather
than open coding node allocation and error handling.

The enum defines the following store types:

enum store_type {
    wr_invalid,
    wr_new_root,
    wr_store_root,
    wr_exact_fit,
    wr_spanning_store,
    wr_split_store,
    wr_rebalance,
    wr_append,
    wr_node_store,
    wr_slot_store,
};

In the current maple tree code, a walk down the tree is done in
mas_preallocate() to determine the number of nodes needed for this write.
After node allocation, mas_wr_store_entry() will perform another walk to
determine which write helper function to use to complete the write.

Rather than performing the second walk, we can store the type of write
in the maple write state during node allocation and read this field to
complete the write.

Patches 1-16 implement this store type feature.
Patch 17 is a cleanup patch to change functions that have unused return
types to be void.

================================ RESULTS =================================

Phoronix t-test-1 (Seconds < Lower Is Better)
    v6.10-rc6
        Threads: 1
            33.15

        Threads: 2
            10.81

    v6.10-rc6 + this series
            Threads: 1
            32.69

        Threads: 2
            10.45

Stress-ng mmap
                    6.10_base  store_type_v4
Duration User        2744.65     2769.40
Duration System     10862.69    10817.59
Duration Elapsed     1477.58     1478.35



================================ TESTING =================================

Testing was done with the maple tree test suite. A new test case is also
added to validate the order in which we test for and assign the store type.

[1]: https://lore.kernel.org/linux-mm/80926b22-a8d2-9992-eb5e-27e2c99cf460@xxxxxxxxxx/T/#m81044feb66765265f8ca7f21e4b4b3725b18780a
[2]: https://lore.kernel.org/linux-mm/80926b22-a8d2-9992-eb5e-27e2c99cf460@xxxxxxxxxx/T/#mb36c6526486638e82518c0f37a428fb279c84d8a
[3]: https://lists.infradead.org/pipermail/maple-tree/2023-December/003098.html

Sidhartha Kumar (17):
  maple_tree: introduce store_type enum
  maple_tree: introduce mas_wr_prealloc_setup()
  maple_tree: move up mas_wr_store_setup() and mas_wr_prealloc_setup()
  maple_tree: introduce mas_wr_store_type()
  maple_tree: remove mas_destroy() from mas_nomem()
  maple_tree: preallocate nodes in mas_erase()
  maple_tree: use mas_store_gfp() in mtree_store_range()
  maple_tree: print store type in mas_dump()
  maple_tree: use store type in mas_wr_store_entry()
  maple_tree: convert mas_insert() to preallocate nodes
  maple_tree: simplify mas_commit_b_node()
  maple_tree: remove mas_wr_modify()
  maple_tree: have mas_store() allocate nodes if needed
  maple_tree: remove node allocations from various write helper
    functions
  maple_tree: remove repeated sanity checks from write helper functions
  maple_tree: remove unneeded mas_wr_walk() in mas_store_prealloc()
  maple_tree: make write helper functions void

 include/linux/maple_tree.h       |  14 +
 lib/maple_tree.c                 | 653 ++++++++++++++++---------------
 tools/testing/radix-tree/maple.c |  46 ++-
 3 files changed, 400 insertions(+), 313 deletions(-)

-- 
2.46.0