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Howlett" Subject: [PATCH v3 1/6] maple_tree: convert mas_prealloc_calc() to take in a maple write state Date: Thu, 27 Feb 2025 20:48:18 +0000 Message-ID: <20250227204823.758784-2-sidhartha.kumar@oracle.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250227204823.758784-1-sidhartha.kumar@oracle.com> References: <20250227204823.758784-1-sidhartha.kumar@oracle.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1057,Hydra:6.0.680,FMLib:17.12.68.34 definitions=2025-02-27_07,2025-02-27_01,2024-11-22_01 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 phishscore=0 spamscore=0 mlxscore=0 adultscore=0 bulkscore=0 mlxlogscore=999 malwarescore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2502100000 definitions=main-2502270154 X-Proofpoint-ORIG-GUID: 3MQcGoUFxweh2jMn3Ee8qzJHIvxipMUo X-Proofpoint-GUID: 3MQcGoUFxweh2jMn3Ee8qzJHIvxipMUo Content-Type: text/plain; charset="utf-8" In a subsequent patch, mas_prealloc_calc() will need to access fields only in the ma_wr_state. Convert the function to take in a ma_wr_state and modify all callers. There is no functional change. Reviewed-by: Liam R. Howlett Signed-off-by: Sidhartha Kumar --- lib/maple_tree.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) diff --git a/lib/maple_tree.c b/lib/maple_tree.c index 42c65974a56c..0410e13a099e 100644 --- a/lib/maple_tree.c +++ b/lib/maple_tree.c @@ -4144,13 +4144,14 @@ static inline void mas_wr_prealloc_setup(struct ma_= wr_state *wr_mas) /** * mas_prealloc_calc() - Calculate number of nodes needed for a * given store oepration - * @mas: The maple state + * @wr_mas: The maple write state * @entry: The entry to store into the tree * * Return: Number of nodes required for preallocation. */ -static inline int mas_prealloc_calc(struct ma_state *mas, void *entry) +static inline int mas_prealloc_calc(struct ma_wr_state *wr_mas, void *entr= y) { + struct ma_state *mas =3D wr_mas->mas; int ret =3D mas_mt_height(mas) * 3 + 1; =20 switch (mas->store_type) { @@ -4247,16 +4248,15 @@ static inline enum store_type mas_wr_store_type(str= uct ma_wr_state *wr_mas) */ static inline void mas_wr_preallocate(struct ma_wr_state *wr_mas, void *en= try) { - struct ma_state *mas =3D wr_mas->mas; int request; =20 mas_wr_prealloc_setup(wr_mas); - mas->store_type =3D mas_wr_store_type(wr_mas); - request =3D mas_prealloc_calc(mas, entry); + wr_mas->mas->store_type =3D mas_wr_store_type(wr_mas); + request =3D mas_prealloc_calc(wr_mas, entry); if (!request) return; =20 - mas_node_count(mas, request); + mas_node_count(wr_mas->mas, request); } =20 /** @@ -5401,7 +5401,7 @@ void *mas_store(struct ma_state *mas, void *entry) return wr_mas.content; } =20 - request =3D mas_prealloc_calc(mas, entry); + request =3D mas_prealloc_calc(&wr_mas, entry); if (!request) goto store; =20 @@ -5498,7 +5498,7 @@ int mas_preallocate(struct ma_state *mas, void *entry= , gfp_t gfp) =20 mas_wr_prealloc_setup(&wr_mas); mas->store_type =3D mas_wr_store_type(&wr_mas); - request =3D mas_prealloc_calc(mas, entry); + request =3D mas_prealloc_calc(&wr_mas, entry); if (!request) return ret; =20 --=20 2.43.0 From nobody Sun Feb 8 05:16:31 2026 Received: from mx0a-00069f02.pphosted.com (mx0a-00069f02.pphosted.com [205.220.165.32]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C72B526A0E8 for ; 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charset="utf-8" For the maple tree, the root node is defined to have a depth of 0 with a height of 1. Each level down from the node, these values are incremented by 1. Various code paths define a root with depth 1 which is inconsisent with the definition. Modify the code to be consistent with this definition. Signed-off-by: Sidhartha Kumar --- lib/maple_tree.c | 85 ++++++++++++++++++++++++++---------------------- 1 file changed, 46 insertions(+), 39 deletions(-) diff --git a/lib/maple_tree.c b/lib/maple_tree.c index 0410e13a099e..a37837d6f3eb 100644 --- a/lib/maple_tree.c +++ b/lib/maple_tree.c @@ -211,14 +211,14 @@ static void ma_free_rcu(struct maple_node *node) call_rcu(&node->rcu, mt_free_rcu); } =20 -static void mas_set_height(struct ma_state *mas) +static void mt_set_height(struct maple_tree *mt, unsigned char height) { - unsigned int new_flags =3D mas->tree->ma_flags; + unsigned int new_flags =3D mt->ma_flags; =20 new_flags &=3D ~MT_FLAGS_HEIGHT_MASK; - MAS_BUG_ON(mas, mas->depth > MAPLE_HEIGHT_MAX); - new_flags |=3D mas->depth << MT_FLAGS_HEIGHT_OFFSET; - mas->tree->ma_flags =3D new_flags; + MT_BUG_ON(mt, height > MAPLE_HEIGHT_MAX); + new_flags |=3D height << MT_FLAGS_HEIGHT_OFFSET; + mt->ma_flags =3D new_flags; } =20 static unsigned int mas_mt_height(struct ma_state *mas) @@ -1375,7 +1375,7 @@ static inline struct maple_enode *mas_start(struct ma= _state *mas) root =3D mas_root(mas); /* Tree with nodes */ if (likely(xa_is_node(root))) { - mas->depth =3D 1; + mas->depth =3D 0; mas->status =3D ma_active; mas->node =3D mte_safe_root(root); mas->offset =3D 0; @@ -1716,9 +1716,10 @@ static inline void mas_adopt_children(struct ma_stat= e *mas, * node as dead. * @mas: the maple state with the new node * @old_enode: The old maple encoded node to replace. + * @new_height: if we are inserting a root node, update the height of the = tree */ static inline void mas_put_in_tree(struct ma_state *mas, - struct maple_enode *old_enode) + struct maple_enode *old_enode, char new_height) __must_hold(mas->tree->ma_lock) { unsigned char offset; @@ -1727,7 +1728,7 @@ static inline void mas_put_in_tree(struct ma_state *m= as, if (mte_is_root(mas->node)) { mas_mn(mas)->parent =3D ma_parent_ptr(mas_tree_parent(mas)); rcu_assign_pointer(mas->tree->ma_root, mte_mk_root(mas->node)); - mas_set_height(mas); + mt_set_height(mas->tree, new_height); } else { =20 offset =3D mte_parent_slot(mas->node); @@ -1745,12 +1746,13 @@ static inline void mas_put_in_tree(struct ma_state = *mas, * the parent encoding to locate the maple node in the tree. * @mas: the ma_state with @mas->node pointing to the new node. * @old_enode: The old maple encoded node. + * @new_height: The new height of the tree as a result of the operation */ static inline void mas_replace_node(struct ma_state *mas, - struct maple_enode *old_enode) + struct maple_enode *old_enode, unsigned char new_height) __must_hold(mas->tree->ma_lock) { - mas_put_in_tree(mas, old_enode); + mas_put_in_tree(mas, old_enode, new_height); mas_free(mas, old_enode); } =20 @@ -2540,10 +2542,11 @@ static inline void mas_topiary_node(struct ma_state= *mas, * * @mas: The maple state pointing at the new data * @old_enode: The maple encoded node being replaced + * @new_height: The new height of the tree as a result of the operation * */ static inline void mas_topiary_replace(struct ma_state *mas, - struct maple_enode *old_enode) + struct maple_enode *old_enode, unsigned char new_height) { struct ma_state tmp[3], tmp_next[3]; MA_TOPIARY(subtrees, mas->tree); @@ -2551,7 +2554,7 @@ static inline void mas_topiary_replace(struct ma_stat= e *mas, int i, n; =20 /* Place data in tree & then mark node as old */ - mas_put_in_tree(mas, old_enode); + mas_put_in_tree(mas, old_enode, new_height); =20 /* Update the parent pointers in the tree */ tmp[0] =3D *mas; @@ -2635,14 +2638,15 @@ static inline void mas_topiary_replace(struct ma_st= ate *mas, * mas_wmb_replace() - Write memory barrier and replace * @mas: The maple state * @old_enode: The old maple encoded node that is being replaced. + * @new_height: The new height of the tree as a result of the operation * * Updates gap as necessary. */ static inline void mas_wmb_replace(struct ma_state *mas, - struct maple_enode *old_enode) + struct maple_enode *old_enode, unsigned char new_height) { /* Insert the new data in the tree */ - mas_topiary_replace(mas, old_enode); + mas_topiary_replace(mas, old_enode, new_height); =20 if (mte_is_leaf(mas->node)) return; @@ -2828,6 +2832,7 @@ static void mas_spanning_rebalance(struct ma_state *m= as, { unsigned char split, mid_split; unsigned char slot =3D 0; + unsigned char new_height =3D 0; /* used if node is a new root */ struct maple_enode *left =3D NULL, *middle =3D NULL, *right =3D NULL; struct maple_enode *old_enode; =20 @@ -2877,7 +2882,7 @@ static void mas_spanning_rebalance(struct ma_state *m= as, */ memset(mast->bn, 0, sizeof(struct maple_big_node)); mast->bn->type =3D mte_node_type(left); - l_mas.depth++; + new_height++; =20 /* Root already stored in l->node. */ if (mas_is_root_limits(mast->l)) @@ -2901,8 +2906,10 @@ static void mas_spanning_rebalance(struct ma_state *= mas, continue; =20 /* May be a new root stored in mast->bn */ - if (mas_is_root_limits(mast->orig_l)) + if (mas_is_root_limits(mast->orig_l)) { + new_height++; break; + } =20 mast_spanning_rebalance(mast); =20 @@ -2913,7 +2920,7 @@ static void mas_spanning_rebalance(struct ma_state *m= as, =20 l_mas.node =3D mt_mk_node(ma_mnode_ptr(mas_pop_node(mas)), mte_node_type(mast->orig_l->node)); - l_mas.depth++; + mab_mas_cp(mast->bn, 0, mt_slots[mast->bn->type] - 1, &l_mas, true); mas_set_parent(mas, left, l_mas.node, slot); if (middle) @@ -2937,7 +2944,7 @@ static void mas_spanning_rebalance(struct ma_state *m= as, mas->min =3D l_mas.min; mas->max =3D l_mas.max; mas->offset =3D l_mas.offset; - mas_wmb_replace(mas, old_enode); + mas_wmb_replace(mas, old_enode, new_height); mtree_range_walk(mas); return; } @@ -3013,6 +3020,7 @@ static inline void mas_destroy_rebalance(struct ma_st= ate *mas, unsigned char end void __rcu **l_slots, **slots; unsigned long *l_pivs, *pivs, gap; bool in_rcu =3D mt_in_rcu(mas->tree); + unsigned char new_height =3D mas_mt_height(mas); =20 MA_STATE(l_mas, mas->tree, mas->index, mas->last); =20 @@ -3107,7 +3115,7 @@ static inline void mas_destroy_rebalance(struct ma_st= ate *mas, unsigned char end mas_ascend(mas); =20 if (in_rcu) { - mas_replace_node(mas, old_eparent); + mas_replace_node(mas, old_eparent, new_height); mas_adopt_children(mas, mas->node); } =20 @@ -3118,10 +3126,9 @@ static inline void mas_destroy_rebalance(struct ma_s= tate *mas, unsigned char end * mas_split_final_node() - Split the final node in a subtree operation. * @mast: the maple subtree state * @mas: The maple state - * @height: The height of the tree in case it's a new root. */ static inline void mas_split_final_node(struct maple_subtree_state *mast, - struct ma_state *mas, int height) + struct ma_state *mas) { struct maple_enode *ancestor; =20 @@ -3130,7 +3137,6 @@ static inline void mas_split_final_node(struct maple_= subtree_state *mast, mast->bn->type =3D maple_arange_64; else mast->bn->type =3D maple_range_64; - mas->depth =3D height; } /* * Only a single node is used here, could be root. @@ -3218,7 +3224,6 @@ static inline void mast_split_data(struct maple_subtr= ee_state *mast, * mas_push_data() - Instead of splitting a node, it is beneficial to push= the * data to the right or left node if there is room. * @mas: The maple state - * @height: The current height of the maple state * @mast: The maple subtree state * @left: Push left or not. * @@ -3226,8 +3231,8 @@ static inline void mast_split_data(struct maple_subtr= ee_state *mast, * * Return: True if pushed, false otherwise. */ -static inline bool mas_push_data(struct ma_state *mas, int height, - struct maple_subtree_state *mast, bool left) +static inline bool mas_push_data(struct ma_state *mas, + struct maple_subtree_state *mast, bool left) { unsigned char slot_total =3D mast->bn->b_end; unsigned char end, space, split; @@ -3284,7 +3289,7 @@ static inline bool mas_push_data(struct ma_state *mas= , int height, =20 mast_split_data(mast, mas, split); mast_fill_bnode(mast, mas, 2); - mas_split_final_node(mast, mas, height + 1); + mas_split_final_node(mast, mas); return true; } =20 @@ -3297,6 +3302,7 @@ static void mas_split(struct ma_state *mas, struct ma= ple_big_node *b_node) { struct maple_subtree_state mast; int height =3D 0; + unsigned int orig_height =3D mas_mt_height(mas); unsigned char mid_split, split =3D 0; struct maple_enode *old; =20 @@ -3323,7 +3329,6 @@ static void mas_split(struct ma_state *mas, struct ma= ple_big_node *b_node) MA_STATE(prev_r_mas, mas->tree, mas->index, mas->last); =20 trace_ma_op(__func__, mas); - mas->depth =3D mas_mt_height(mas); =20 mast.l =3D &l_mas; mast.r =3D &r_mas; @@ -3331,9 +3336,9 @@ static void mas_split(struct ma_state *mas, struct ma= ple_big_node *b_node) mast.orig_r =3D &prev_r_mas; mast.bn =3D b_node; =20 - while (height++ <=3D mas->depth) { + while (height++ <=3D orig_height) { if (mt_slots[b_node->type] > b_node->b_end) { - mas_split_final_node(&mast, mas, height); + mas_split_final_node(&mast, mas); break; } =20 @@ -3348,11 +3353,15 @@ static void mas_split(struct ma_state *mas, struct = maple_big_node *b_node) * is a significant savings. */ /* Try to push left. */ - if (mas_push_data(mas, height, &mast, true)) + if (mas_push_data(mas, &mast, true)) { + height++; break; + } /* Try to push right. */ - if (mas_push_data(mas, height, &mast, false)) + if (mas_push_data(mas, &mast, false)) { + height++; break; + } =20 split =3D mab_calc_split(mas, b_node, &mid_split); mast_split_data(&mast, mas, split); @@ -3369,7 +3378,7 @@ static void mas_split(struct ma_state *mas, struct ma= ple_big_node *b_node) /* Set the original node as dead */ old =3D mas->node; mas->node =3D l_mas.node; - mas_wmb_replace(mas, old); + mas_wmb_replace(mas, old, height); mtree_range_walk(mas); return; } @@ -3428,8 +3437,7 @@ static inline void mas_root_expand(struct ma_state *m= as, void *entry) if (mas->last !=3D ULONG_MAX) pivots[++slot] =3D ULONG_MAX; =20 - mas->depth =3D 1; - mas_set_height(mas); + mt_set_height(mas->tree, 1); ma_set_meta(node, maple_leaf_64, 0, slot); /* swap the new root into the tree */ rcu_assign_pointer(mas->tree->ma_root, mte_mk_root(mas->node)); @@ -3673,8 +3681,7 @@ static inline void mas_new_root(struct ma_state *mas,= void *entry) WARN_ON_ONCE(mas->index || mas->last !=3D ULONG_MAX); =20 if (!entry) { - mas->depth =3D 0; - mas_set_height(mas); + mt_set_height(mas->tree, 0); rcu_assign_pointer(mas->tree->ma_root, entry); mas->status =3D ma_start; goto done; @@ -3688,8 +3695,7 @@ static inline void mas_new_root(struct ma_state *mas,= void *entry) mas->status =3D ma_active; rcu_assign_pointer(slots[0], entry); pivots[0] =3D mas->last; - mas->depth =3D 1; - mas_set_height(mas); + mt_set_height(mas->tree, 1); rcu_assign_pointer(mas->tree->ma_root, mte_mk_root(mas->node)); =20 done: @@ -3808,6 +3814,7 @@ static inline void mas_wr_node_store(struct ma_wr_sta= te *wr_mas, struct maple_node reuse, *newnode; unsigned char copy_size, node_pivots =3D mt_pivots[wr_mas->type]; 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charset="utf-8" In order to determine the store type for a maple tree operation, a walk of the tree is done through mas_wr_walk(). This function descends the tree until a spanning write is detected or we reach a leaf node. While descending, keep track of the height at which we encounter a node with available space. This is done by checking if mas->end is less than the number of slots a given node type can fit. Now that the height of the vacant node is tracked, we can use the difference between the height of the tree and the height of the vacant node to know how many levels we will have to propagate creating new nodes. Update mas_prealloc_calc() to consider the vacant height and reduce the number of worst-case allocations. Rebalancing and spanning stores are not supported and fall back to using the full height of the tree for allocations. Update preallocation testing assertions to take into account vacant height. Signed-off-by: Sidhartha --- include/linux/maple_tree.h | 2 + lib/maple_tree.c | 13 ++++-- tools/testing/radix-tree/maple.c | 79 ++++++++++++++++++++++++++++---- 3 files changed, 82 insertions(+), 12 deletions(-) diff --git a/include/linux/maple_tree.h b/include/linux/maple_tree.h index cbbcd18d4186..7d777aa2d9ed 100644 --- a/include/linux/maple_tree.h +++ b/include/linux/maple_tree.h @@ -463,6 +463,7 @@ struct ma_wr_state { void __rcu **slots; /* mas->node->slots pointer */ void *entry; /* The entry to write */ void *content; /* The existing entry that is being overwritten */ + unsigned char vacant_height; /* Depth of lowest node with free space */ }; =20 #define mas_lock(mas) spin_lock(&((mas)->tree->ma_lock)) @@ -498,6 +499,7 @@ struct ma_wr_state { .mas =3D ma_state, \ .content =3D NULL, \ .entry =3D wr_entry, \ + .vacant_height =3D 0 \ } =20 #define MA_TOPIARY(name, tree) \ diff --git a/lib/maple_tree.c b/lib/maple_tree.c index a37837d6f3eb..878a7740628c 100644 --- a/lib/maple_tree.c +++ b/lib/maple_tree.c @@ -3544,6 +3544,9 @@ static bool mas_wr_walk(struct ma_wr_state *wr_mas) if (ma_is_leaf(wr_mas->type)) return true; =20 + if (mas->end < mt_slots[wr_mas->type] - 1) + wr_mas->vacant_height =3D mas->depth + 1; + mas_wr_walk_traverse(wr_mas); } =20 @@ -4159,7 +4162,9 @@ static inline void mas_wr_prealloc_setup(struct ma_wr= _state *wr_mas) static inline int mas_prealloc_calc(struct ma_wr_state *wr_mas, void *entr= y) { struct ma_state *mas =3D wr_mas->mas; - int ret =3D mas_mt_height(mas) * 3 + 1; + unsigned char height =3D mas_mt_height(mas); + int ret =3D height * 3 + 1; + unsigned char delta =3D height - wr_mas->vacant_height; =20 switch (mas->store_type) { case wr_invalid: @@ -4177,13 +4182,13 @@ static inline int mas_prealloc_calc(struct ma_wr_st= ate *wr_mas, void *entry) ret =3D 0; break; case wr_spanning_store: - ret =3D mas_mt_height(mas) * 3 + 1; + WARN_ON_ONCE(ret !=3D height * 3 + 1); break; case wr_split_store: - ret =3D mas_mt_height(mas) * 2 + 1; + ret =3D delta * 2 + 1; break; case wr_rebalance: - ret =3D mas_mt_height(mas) * 2 - 1; + ret =3D height * 2 + 1; break; case wr_node_store: ret =3D mt_in_rcu(mas->tree) ? 1 : 0; diff --git a/tools/testing/radix-tree/maple.c b/tools/testing/radix-tree/ma= ple.c index bc30050227fd..5950a7c9b27f 100644 --- a/tools/testing/radix-tree/maple.c +++ b/tools/testing/radix-tree/maple.c @@ -35475,15 +35475,65 @@ static void check_dfs_preorder(struct maple_tree = *mt) } /* End of depth first search tests */ =20 +/* get height of the lowest non-leaf node with free space */ +static unsigned char get_vacant_height(struct ma_wr_state *wr_mas, void *e= ntry) +{ + struct ma_state *mas =3D wr_mas->mas; + char vacant_height =3D 0; + enum maple_type type; + unsigned long *pivots; + unsigned long min =3D 0; + unsigned long max =3D ULONG_MAX; + unsigned char offset; + + /* start traversal */ + mas_reset(mas); + mas_start(mas); + if (!xa_is_node(mas_root(mas))) + return 0; + + type =3D mte_node_type(mas->node); + wr_mas->type =3D type; + while (!ma_is_leaf(type)) { + mas_node_walk(mas, mte_to_node(mas->node), type, &min, &max); + offset =3D mas->offset; + mas->end =3D mas_data_end(mas); + pivots =3D ma_pivots(mte_to_node(mas->node), type); + + if (pivots) { + if (offset) + min =3D pivots[mas->offset - 1]; + if (offset < mas->end) + max =3D pivots[mas->offset]; + } + wr_mas->r_max =3D offset < mas->end ? pivots[offset] : mas->max; + + /* detect spanning write */ + if (mas_is_span_wr(wr_mas)) + break; + + if (mas->end < mt_slot_count(mas->node) - 1) + vacant_height =3D mas->depth + 1; + + mas_descend(mas); + type =3D mte_node_type(mas->node); + mas->depth++; + } + + return vacant_height; +} + /* Preallocation testing */ static noinline void __init check_prealloc(struct maple_tree *mt) { unsigned long i, max =3D 100; unsigned long allocated; unsigned char height; + unsigned char vacant_height; struct maple_node *mn; void *ptr =3D check_prealloc; MA_STATE(mas, mt, 10, 20); + MA_WR_STATE(wr_mas, &mas, ptr); =20 mt_set_non_kernel(1000); for (i =3D 0; i <=3D max; i++) @@ -35494,8 +35544,9 @@ static noinline void __init check_prealloc(struct m= aple_tree *mt) MT_BUG_ON(mt, mas_preallocate(&mas, ptr, GFP_KERNEL) !=3D 0); allocated =3D mas_allocated(&mas); height =3D mas_mt_height(&mas); + vacant_height =3D get_vacant_height(&wr_mas, ptr); MT_BUG_ON(mt, allocated =3D=3D 0); - MT_BUG_ON(mt, allocated !=3D 1 + height * 3); + MT_BUG_ON(mt, allocated !=3D 1 + (height - vacant_height) * 3); mas_destroy(&mas); allocated =3D mas_allocated(&mas); MT_BUG_ON(mt, allocated !=3D 0); @@ -35503,8 +35554,9 @@ static noinline void __init check_prealloc(struct m= aple_tree *mt) MT_BUG_ON(mt, mas_preallocate(&mas, ptr, GFP_KERNEL) !=3D 0); allocated =3D mas_allocated(&mas); height =3D mas_mt_height(&mas); + vacant_height =3D get_vacant_height(&wr_mas, ptr); MT_BUG_ON(mt, allocated =3D=3D 0); - MT_BUG_ON(mt, allocated !=3D 1 + height * 3); + MT_BUG_ON(mt, allocated !=3D 1 + (height - vacant_height) * 3); MT_BUG_ON(mt, mas_preallocate(&mas, ptr, GFP_KERNEL) !=3D 0); mas_destroy(&mas); allocated =3D mas_allocated(&mas); @@ -35514,7 +35566,8 @@ static noinline void __init check_prealloc(struct m= aple_tree *mt) MT_BUG_ON(mt, mas_preallocate(&mas, ptr, GFP_KERNEL) !=3D 0); allocated =3D mas_allocated(&mas); height =3D mas_mt_height(&mas); - MT_BUG_ON(mt, allocated !=3D 1 + height * 3); + vacant_height =3D get_vacant_height(&wr_mas, ptr); + MT_BUG_ON(mt, allocated !=3D 1 + (height - vacant_height) * 3); mn =3D mas_pop_node(&mas); MT_BUG_ON(mt, mas_allocated(&mas) !=3D allocated - 1); mn->parent =3D ma_parent_ptr(mn); @@ -35527,7 +35580,8 @@ static noinline void __init check_prealloc(struct m= aple_tree *mt) MT_BUG_ON(mt, mas_preallocate(&mas, ptr, GFP_KERNEL) !=3D 0); allocated =3D mas_allocated(&mas); height =3D mas_mt_height(&mas); - MT_BUG_ON(mt, allocated !=3D 1 + height * 3); + vacant_height =3D get_vacant_height(&wr_mas, ptr); + MT_BUG_ON(mt, allocated !=3D 1 + (height - vacant_height) * 3); mn =3D mas_pop_node(&mas); MT_BUG_ON(mt, mas_allocated(&mas) !=3D allocated - 1); MT_BUG_ON(mt, mas_preallocate(&mas, ptr, GFP_KERNEL) !=3D 0); @@ -35540,7 +35594,8 @@ static noinline void __init check_prealloc(struct m= aple_tree *mt) MT_BUG_ON(mt, mas_preallocate(&mas, ptr, GFP_KERNEL) !=3D 0); allocated =3D mas_allocated(&mas); height =3D mas_mt_height(&mas); - MT_BUG_ON(mt, allocated !=3D 1 + height * 3); + vacant_height =3D get_vacant_height(&wr_mas, ptr); + MT_BUG_ON(mt, allocated !=3D 1 + (height - vacant_height) * 3); mn =3D mas_pop_node(&mas); MT_BUG_ON(mt, mas_allocated(&mas) !=3D allocated - 1); mas_push_node(&mas, mn); @@ -35553,7 +35608,8 @@ static noinline void __init check_prealloc(struct m= aple_tree *mt) MT_BUG_ON(mt, mas_preallocate(&mas, ptr, GFP_KERNEL) !=3D 0); allocated =3D mas_allocated(&mas); height =3D mas_mt_height(&mas); - MT_BUG_ON(mt, allocated !=3D 1 + height * 3); + vacant_height =3D get_vacant_height(&wr_mas, ptr); + MT_BUG_ON(mt, allocated !=3D 1 + (height - vacant_height) * 3); mas_store_prealloc(&mas, ptr); MT_BUG_ON(mt, mas_allocated(&mas) !=3D 0); =20 @@ -35578,7 +35634,8 @@ static noinline void __init check_prealloc(struct m= aple_tree *mt) MT_BUG_ON(mt, mas_preallocate(&mas, ptr, GFP_KERNEL) !=3D 0); allocated =3D mas_allocated(&mas); height =3D mas_mt_height(&mas); - MT_BUG_ON(mt, allocated !=3D 1 + height * 2); + vacant_height =3D get_vacant_height(&wr_mas, ptr); + MT_BUG_ON(mt, allocated !=3D 1 + (height - vacant_height) * 2); mas_store_prealloc(&mas, ptr); MT_BUG_ON(mt, mas_allocated(&mas) !=3D 0); mt_set_non_kernel(1); @@ -35595,8 +35652,14 @@ static noinline void __init check_prealloc(struct = maple_tree *mt) MT_BUG_ON(mt, mas_preallocate(&mas, ptr, GFP_KERNEL) !=3D 0); allocated =3D mas_allocated(&mas); height =3D mas_mt_height(&mas); + vacant_height =3D get_vacant_height(&wr_mas, ptr); MT_BUG_ON(mt, allocated =3D=3D 0); - MT_BUG_ON(mt, allocated !=3D 1 + height * 3); + /* + * vacant height cannot be used to compute the number of nodes needed + * as the root contains two entries which means it is on the verge of + * insufficiency. 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Howlett" Subject: [PATCH v3 4/6] maple_tree: break on convergence in mas_spanning_rebalance() Date: Thu, 27 Feb 2025 20:48:21 +0000 Message-ID: <20250227204823.758784-5-sidhartha.kumar@oracle.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250227204823.758784-1-sidhartha.kumar@oracle.com> References: <20250227204823.758784-1-sidhartha.kumar@oracle.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1057,Hydra:6.0.680,FMLib:17.12.68.34 definitions=2025-02-27_07,2025-02-27_01,2024-11-22_01 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 phishscore=0 spamscore=0 mlxscore=0 adultscore=0 bulkscore=0 mlxlogscore=999 malwarescore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2502100000 definitions=main-2502270154 X-Proofpoint-ORIG-GUID: qbzTOSdHShzfMYbSFjzmfG_Qc6PIheuw X-Proofpoint-GUID: qbzTOSdHShzfMYbSFjzmfG_Qc6PIheuw Content-Type: text/plain; charset="utf-8" This allows support for using the vacant height to calculate the worst case number of nodes needed for wr_rebalance operation. mas_spanning_rebalance() was seen to perform unnecessary node allocations. We can reduce allocations by breaking early during the rebalancing loop once we realize that we have ascended to a common ancestor. Suggested-by: Liam Howlett Reviewed-by: Wei Yang Reviewed-by: Liam R. Howlett Signed-off-by: Sidhartha Kumar --- lib/maple_tree.c | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-) diff --git a/lib/maple_tree.c b/lib/maple_tree.c index 878a7740628c..c859c7253d69 100644 --- a/lib/maple_tree.c +++ b/lib/maple_tree.c @@ -2899,11 +2899,24 @@ static void mas_spanning_rebalance(struct ma_state = *mas, mast_combine_cp_right(mast); mast->orig_l->last =3D mast->orig_l->max; =20 - if (mast_sufficient(mast)) - continue; + if (mast_sufficient(mast)) { + if (mast_overflow(mast)) + continue; + + if (mast->orig_l->node =3D=3D mast->orig_r->node) { + /* + * The data in b_node should be stored in one + * node and in the tree + */ + slot =3D mast->l->offset; + /* May be a new root stored in mast->bn */ + if (mas_is_root_limits(mast->orig_l)) + new_height++; + break; + } =20 - if (mast_overflow(mast)) continue; + } =20 /* May be a new root stored in mast->bn */ if (mas_is_root_limits(mast->orig_l)) { --=20 2.43.0 From nobody Sun Feb 8 05:16:31 2026 Received: from mx0a-00069f02.pphosted.com (mx0a-00069f02.pphosted.com [205.220.165.32]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 50589271808 for ; 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charset="utf-8" In order to support rebalancing and spanning stores using less than the worst case number of nodes, we need to track more than just the vacant height. Using only vacant height to reduce the worst case maple node allocation count can lead to a shortcoming of nodes in the following scenarios. For rebalancing writes, when a leaf node becomes insufficient, it may be combined with a sibling into a single node. This means that the parent node which has entries for this children will lose one entry. If this parent node was just meeting the minimum entries, losing one entry will now cause this parent node to be insufficient. This leads to a cascading operation of rebalancing at different levels and can lead to more node allocations than simply using vacant height can return. For spanning writes, a similar situation occurs. At the location at which a spanning write is detected, the number of ancestor nodes may similarly need to rebalanced into a smaller number of nodes and the same cascading situation could occur. To use less than the full height of the tree for the number of allocations, we also need to track the height at which a non-leaf node cannot become insufficient. This means even if a rebalance occurs to a child of this node, it currently has enough entries that it can lose one without any further action. This field is stored in the maple write state as sufficient height. In mas_prealloc_calc() when figuring out how many nodes to allocate, we check if the the vacant node is lower in the tree than a sufficient node (has a larger value). If it is, we cannot use the vacant height and must use the difference in the height and sufficient height as the basis for the number of nodes needed. Signed-off-by: Sidhartha Kumar --- include/linux/maple_tree.h | 4 +++- lib/maple_tree.c | 17 +++++++++++++++-- tools/testing/radix-tree/maple.c | 28 ++++++++++++++++++++++++++++ 3 files changed, 46 insertions(+), 3 deletions(-) diff --git a/include/linux/maple_tree.h b/include/linux/maple_tree.h index 7d777aa2d9ed..37dc9525dff6 100644 --- a/include/linux/maple_tree.h +++ b/include/linux/maple_tree.h @@ -464,6 +464,7 @@ struct ma_wr_state { void *entry; /* The entry to write */ void *content; /* The existing entry that is being overwritten */ unsigned char vacant_height; /* Depth of lowest node with free space */ + unsigned char sufficient_height;/* Depth of lowest node with min sufficie= ncy + 1 nodes */ }; =20 #define mas_lock(mas) spin_lock(&((mas)->tree->ma_lock)) @@ -499,7 +500,8 @@ struct ma_wr_state { .mas =3D ma_state, \ .content =3D NULL, \ .entry =3D wr_entry, \ - .vacant_height =3D 0 \ + .vacant_height =3D 0, \ + .sufficient_height =3D 0 \ } =20 #define MA_TOPIARY(name, tree) \ diff --git a/lib/maple_tree.c b/lib/maple_tree.c index c859c7253d69..d3aa5241166b 100644 --- a/lib/maple_tree.c +++ b/lib/maple_tree.c @@ -3560,6 +3560,13 @@ static bool mas_wr_walk(struct ma_wr_state *wr_mas) if (mas->end < mt_slots[wr_mas->type] - 1) wr_mas->vacant_height =3D mas->depth + 1; =20 + if (ma_is_root(mas_mn(mas))) { + /* root needs more than 2 entries to be sufficient + 1 */ + if (mas->end > 2) + wr_mas->sufficient_height =3D 1; + } else if (mas->end > mt_min_slots[wr_mas->type] + 1) + wr_mas->sufficient_height =3D mas->depth + 1; + mas_wr_walk_traverse(wr_mas); } =20 @@ -4195,13 +4202,19 @@ static inline int mas_prealloc_calc(struct ma_wr_st= ate *wr_mas, void *entry) ret =3D 0; break; case wr_spanning_store: - WARN_ON_ONCE(ret !=3D height * 3 + 1); + if (wr_mas->sufficient_height < wr_mas->vacant_height) + ret =3D (height - wr_mas->sufficient_height) * 3 + 1; + else + ret =3D delta * 3 + 1; break; case wr_split_store: ret =3D delta * 2 + 1; break; case wr_rebalance: - ret =3D height * 2 + 1; + if (wr_mas->sufficient_height < wr_mas->vacant_height) + ret =3D (height - wr_mas->sufficient_height) * 2 + 1; + else + ret =3D delta * 2 + 1; break; case wr_node_store: ret =3D mt_in_rcu(mas->tree) ? 1 : 0; diff --git a/tools/testing/radix-tree/maple.c b/tools/testing/radix-tree/ma= ple.c index 5950a7c9b27f..dc8e40b94c3f 100644 --- a/tools/testing/radix-tree/maple.c +++ b/tools/testing/radix-tree/maple.c @@ -36311,6 +36311,30 @@ static noinline void __init check_mtree_dup(struct= maple_tree *mt) =20 extern void test_kmem_cache_bulk(void); =20 +/* + * Test to check the path of a spanning rebalance which results in + * a collapse where the rebalancing of the child node leads to + * insufficieny in the parent node. + */ +static void check_collapsing_rebalance(struct maple_tree *mt) +{ + int i =3D 0; + MA_STATE(mas, mt, ULONG_MAX, ULONG_MAX); + + /* create a height 4 tree */ + while (mt_height(mt) < 4) { + mtree_store_range(mt, i, i + 10, xa_mk_value(i), GFP_KERNEL); + i +=3D 9; + } + + /* delete all entries one at a time, starting from the right */ + do { + mas_erase(&mas); + } while (mas_prev(&mas, 0) !=3D NULL); + + mtree_unlock(mt); +} + /* callback function used for check_nomem_writer_race() */ static void writer2(void *maple_tree) { @@ -36477,6 +36501,10 @@ void farmer_tests(void) check_spanning_write(&tree); mtree_destroy(&tree); =20 + mt_init_flags(&tree, MT_FLAGS_ALLOC_RANGE); + check_collapsing_rebalance(&tree); + mtree_destroy(&tree); + mt_init_flags(&tree, MT_FLAGS_ALLOC_RANGE); check_null_expand(&tree); mtree_destroy(&tree); 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Howlett" Subject: [PATCH v3 6/6] maple_tree: reorder mas->store_type case statements Date: Thu, 27 Feb 2025 20:48:23 +0000 Message-ID: <20250227204823.758784-7-sidhartha.kumar@oracle.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250227204823.758784-1-sidhartha.kumar@oracle.com> References: <20250227204823.758784-1-sidhartha.kumar@oracle.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1057,Hydra:6.0.680,FMLib:17.12.68.34 definitions=2025-02-27_07,2025-02-27_01,2024-11-22_01 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 phishscore=0 spamscore=0 mlxscore=0 adultscore=0 bulkscore=0 mlxlogscore=999 malwarescore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2502100000 definitions=main-2502270154 X-Proofpoint-ORIG-GUID: lKETHqUtyLBnsXDOSH0cE46buP1f3N_E X-Proofpoint-GUID: lKETHqUtyLBnsXDOSH0cE46buP1f3N_E Content-Type: text/plain; charset="utf-8" Move the unlikely case that mas->store_type is invalid to be the last evaluated case and put liklier cases higher up. Suggested-by: Liam R. Howlett Reviewed-by: Liam R. Howlett Signed-off-by: Sidhartha Kumar --- lib/maple_tree.c | 51 ++++++++++++++++++++++++------------------------ 1 file changed, 25 insertions(+), 26 deletions(-) diff --git a/lib/maple_tree.c b/lib/maple_tree.c index d3aa5241166b..776693593ab9 100644 --- a/lib/maple_tree.c +++ b/lib/maple_tree.c @@ -4093,15 +4093,6 @@ static inline void mas_wr_store_entry(struct ma_wr_s= tate *wr_mas) unsigned char new_end =3D mas_wr_new_end(wr_mas); =20 switch (mas->store_type) { - case wr_invalid: - MT_BUG_ON(mas->tree, 1); - return; - case wr_new_root: - mas_new_root(mas, wr_mas->entry); - break; - case wr_store_root: - mas_store_root(mas, wr_mas->entry); - break; case wr_exact_fit: rcu_assign_pointer(wr_mas->slots[mas->offset], wr_mas->entry); if (!!wr_mas->entry ^ !!wr_mas->content) @@ -4123,6 +4114,14 @@ static inline void mas_wr_store_entry(struct ma_wr_s= tate *wr_mas) case wr_rebalance: mas_wr_bnode(wr_mas); break; + case wr_new_root: + mas_new_root(mas, wr_mas->entry); + break; + case wr_store_root: + mas_store_root(mas, wr_mas->entry); + break; + case wr_invalid: + MT_BUG_ON(mas->tree, 1); } =20 return; @@ -4187,19 +4186,10 @@ static inline int mas_prealloc_calc(struct ma_wr_st= ate *wr_mas, void *entry) unsigned char delta =3D height - wr_mas->vacant_height; =20 switch (mas->store_type) { - case wr_invalid: - WARN_ON_ONCE(1); - break; - case wr_new_root: - ret =3D 1; - break; - case wr_store_root: - if (likely((mas->last !=3D 0) || (mas->index !=3D 0))) - ret =3D 1; - else if (((unsigned long) (entry) & 3) =3D=3D 2) - ret =3D 1; - else - ret =3D 0; + case wr_exact_fit: + case wr_append: + case wr_slot_store: + ret =3D 0; break; case wr_spanning_store: if (wr_mas->sufficient_height < wr_mas->vacant_height) @@ -4219,10 +4209,19 @@ static inline int mas_prealloc_calc(struct ma_wr_st= ate *wr_mas, void *entry) case wr_node_store: ret =3D mt_in_rcu(mas->tree) ? 1 : 0; break; - case wr_append: - case wr_exact_fit: - case wr_slot_store: - ret =3D 0; + case wr_new_root: + ret =3D 1; + break; + case wr_store_root: + if (likely((mas->last !=3D 0) || (mas->index !=3D 0))) + ret =3D 1; + else if (((unsigned long) (entry) & 3) =3D=3D 2) + ret =3D 1; + else + ret =3D 0; + break; + case wr_invalid: + WARN_ON_ONCE(1); } =20 return ret; --=20 2.43.0