1/* SPDX-License-Identifier: GPL-2.0 */ 2 3#ifndef _LINUX_OBJPOOL_H 4#define _LINUX_OBJPOOL_H 5 6#include <linux/types.h> 7#include <linux/refcount.h> 8 9/* 10 * objpool: ring-array based lockless MPMC queue 11 * 12 * Copyright: wuqiang.matt@bytedance.com,mhiramat@kernel.org 13 * 14 * objpool is a scalable implementation of high performance queue for 15 * object allocation and reclamation, such as kretprobe instances. 16 * 17 * With leveraging percpu ring-array to mitigate hot spots of memory 18 * contention, it delivers near-linear scalability for high parallel 19 * scenarios. The objpool is best suited for the following cases: 20 * 1) Memory allocation or reclamation are prohibited or too expensive 21 * 2) Consumers are of different priorities, such as irqs and threads 22 * 23 * Limitations: 24 * 1) Maximum objects (capacity) is fixed after objpool creation 25 * 2) All pre-allocated objects are managed in percpu ring array, 26 * which consumes more memory than linked lists 27 */ 28 29/** 30 * struct objpool_slot - percpu ring array of objpool 31 * @head: head sequence of the local ring array (to retrieve at) 32 * @tail: tail sequence of the local ring array (to append at) 33 * @last: the last sequence number marked as ready for retrieve 34 * @mask: bits mask for modulo capacity to compute array indexes 35 * @entries: object entries on this slot 36 * 37 * Represents a cpu-local array-based ring buffer, its size is specialized 38 * during initialization of object pool. The percpu objpool node is to be 39 * allocated from local memory for NUMA system, and to be kept compact in 40 * continuous memory: CPU assigned number of objects are stored just after 41 * the body of objpool_node. 42 * 43 * Real size of the ring array is far too smaller than the value range of 44 * head and tail, typed as uint32_t: [0, 2^32), so only lower bits (mask) 45 * of head and tail are used as the actual position in the ring array. In 46 * general the ring array is acting like a small sliding window, which is 47 * always moving forward in the loop of [0, 2^32). 48 */ 49struct objpool_slot { 50 uint32_t head; 51 uint32_t tail; 52 uint32_t last; 53 uint32_t mask; 54 void *entries[]; 55} __packed; 56 57struct objpool_head; 58 59/* 60 * caller-specified callback for object initial setup, it's only called 61 * once for each object (just after the memory allocation of the object) 62 */ 63typedef int (*objpool_init_obj_cb)(void *obj, void *context); 64 65/* caller-specified cleanup callback for objpool destruction */ 66typedef int (*objpool_fini_cb)(struct objpool_head *head, void *context); 67 68/** 69 * struct objpool_head - object pooling metadata 70 * @obj_size: object size, aligned to sizeof(void *) 71 * @nr_objs: total objs (to be pre-allocated with objpool) 72 * @nr_cpus: local copy of nr_cpu_ids 73 * @capacity: max objs can be managed by one objpool_slot 74 * @gfp: gfp flags for kmalloc & vmalloc 75 * @ref: refcount of objpool 76 * @flags: flags for objpool management 77 * @cpu_slots: pointer to the array of objpool_slot 78 * @release: resource cleanup callback 79 * @context: caller-provided context 80 */ 81struct objpool_head { 82 int obj_size; 83 int nr_objs; 84 int nr_cpus; 85 int capacity; 86 gfp_t gfp; 87 refcount_t ref; 88 unsigned long flags; 89 struct objpool_slot **cpu_slots; 90 objpool_fini_cb release; 91 void *context; 92}; 93 94#define OBJPOOL_NR_OBJECT_MAX (1UL << 24) /* maximum numbers of total objects */ 95#define OBJPOOL_OBJECT_SIZE_MAX (1UL << 16) /* maximum size of an object */ 96 97/** 98 * objpool_init() - initialize objpool and pre-allocated objects 99 * @pool: the object pool to be initialized, declared by caller 100 * @nr_objs: total objects to be pre-allocated by this object pool 101 * @object_size: size of an object (should be > 0) 102 * @gfp: flags for memory allocation (via kmalloc or vmalloc) 103 * @context: user context for object initialization callback 104 * @objinit: object initialization callback for extra setup 105 * @release: cleanup callback for extra cleanup task 106 * 107 * return value: 0 for success, otherwise error code 108 * 109 * All pre-allocated objects are to be zeroed after memory allocation. 110 * Caller could do extra initialization in objinit callback. objinit() 111 * will be called just after slot allocation and called only once for 112 * each object. After that the objpool won't touch any content of the 113 * objects. It's caller's duty to perform reinitialization after each 114 * pop (object allocation) or do clearance before each push (object 115 * reclamation). 116 */ 117int objpool_init(struct objpool_head *pool, int nr_objs, int object_size, 118 gfp_t gfp, void *context, objpool_init_obj_cb objinit, 119 objpool_fini_cb release); 120 121/** 122 * objpool_pop() - allocate an object from objpool 123 * @pool: object pool 124 * 125 * return value: object ptr or NULL if failed 126 */ 127void *objpool_pop(struct objpool_head *pool); 128 129/** 130 * objpool_push() - reclaim the object and return back to objpool 131 * @obj: object ptr to be pushed to objpool 132 * @pool: object pool 133 * 134 * return: 0 or error code (it fails only when user tries to push 135 * the same object multiple times or wrong "objects" into objpool) 136 */ 137int objpool_push(void *obj, struct objpool_head *pool); 138 139/** 140 * objpool_drop() - discard the object and deref objpool 141 * @obj: object ptr to be discarded 142 * @pool: object pool 143 * 144 * return: 0 if objpool was released; -EAGAIN if there are still 145 * outstanding objects 146 * 147 * objpool_drop is normally for the release of outstanding objects 148 * after objpool cleanup (objpool_fini). Thinking of this example: 149 * kretprobe is unregistered and objpool_fini() is called to release 150 * all remained objects, but there are still objects being used by 151 * unfinished kretprobes (like blockable function: sys_accept). So 152 * only when the last outstanding object is dropped could the whole 153 * objpool be released along with the call of objpool_drop() 154 */ 155int objpool_drop(void *obj, struct objpool_head *pool); 156 157/** 158 * objpool_free() - release objpool forcely (all objects to be freed) 159 * @pool: object pool to be released 160 */ 161void objpool_free(struct objpool_head *pool); 162 163/** 164 * objpool_fini() - deref object pool (also releasing unused objects) 165 * @pool: object pool to be dereferenced 166 * 167 * objpool_fini() will try to release all remained free objects and 168 * then drop an extra reference of the objpool. If all objects are 169 * already returned to objpool (so called synchronous use cases), 170 * the objpool itself will be freed together. But if there are still 171 * outstanding objects (so called asynchronous use cases, such like 172 * blockable kretprobe), the objpool won't be released until all 173 * the outstanding objects are dropped, but the caller must assure 174 * there are no concurrent objpool_push() on the fly. Normally RCU 175 * is being required to make sure all ongoing objpool_push() must 176 * be finished before calling objpool_fini(), so does test_objpool, 177 * kretprobe or rethook 178 */ 179void objpool_fini(struct objpool_head *pool); 180 181#endif /* _LINUX_OBJPOOL_H */ 182