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1// SPDX-License-Identifier: GPL-2.0
2
3#include <linux/objpool.h>
4#include <linux/slab.h>
5#include <linux/vmalloc.h>
6#include <linux/atomic.h>
7#include <linux/irqflags.h>
8#include <linux/cpumask.h>
9#include <linux/log2.h>
10
11/*
12 * objpool: ring-array based lockless MPMC/FIFO queues
13 *
14 * Copyright: wuqiang.matt@bytedance.com,mhiramat@kernel.org
15 */
16
17/* initialize percpu objpool_slot */
18static int
19objpool_init_percpu_slot(struct objpool_head *pool,
20 struct objpool_slot *slot,
21 int nodes, void *context,
22 objpool_init_obj_cb objinit)
23{
24 void *obj = (void *)&slot->entries[pool->capacity];
25 int i;
26
27 /* initialize elements of percpu objpool_slot */
28 slot->mask = pool->capacity - 1;
29
30 for (i = 0; i < nodes; i++) {
31 if (objinit) {
32 int rc = objinit(obj, context);
33 if (rc)
34 return rc;
35 }
36 slot->entries[slot->tail & slot->mask] = obj;
37 obj = obj + pool->obj_size;
38 slot->tail++;
39 slot->last = slot->tail;
40 pool->nr_objs++;
41 }
42
43 return 0;
44}
45
46/* allocate and initialize percpu slots */
47static int
48objpool_init_percpu_slots(struct objpool_head *pool, int nr_objs,
49 void *context, objpool_init_obj_cb objinit)
50{
51 int i, cpu_count = 0;
52
53 for (i = 0; i < pool->nr_cpus; i++) {
54
55 struct objpool_slot *slot;
56 int nodes, size, rc;
57
58 /* skip the cpu node which could never be present */
59 if (!cpu_possible(i))
60 continue;
61
62 /* compute how many objects to be allocated with this slot */
63 nodes = nr_objs / num_possible_cpus();
64 if (cpu_count < (nr_objs % num_possible_cpus()))
65 nodes++;
66 cpu_count++;
67
68 size = struct_size(slot, entries, pool->capacity) +
69 pool->obj_size * nodes;
70
71 /*
72 * here we allocate percpu-slot & objs together in a single
73 * allocation to make it more compact, taking advantage of
74 * warm caches and TLB hits. in default vmalloc is used to
75 * reduce the pressure of kernel slab system. as we know,
76 * mimimal size of vmalloc is one page since vmalloc would
77 * always align the requested size to page size
78 */
79 if (pool->gfp & GFP_ATOMIC)
80 slot = kmalloc_node(size, pool->gfp, cpu_to_node(i));
81 else
82 slot = __vmalloc_node(size, sizeof(void *), pool->gfp,
83 cpu_to_node(i), __builtin_return_address(0));
84 if (!slot)
85 return -ENOMEM;
86 memset(slot, 0, size);
87 pool->cpu_slots[i] = slot;
88
89 /* initialize the objpool_slot of cpu node i */
90 rc = objpool_init_percpu_slot(pool, slot, nodes, context, objinit);
91 if (rc)
92 return rc;
93 }
94
95 return 0;
96}
97
98/* cleanup all percpu slots of the object pool */
99static void objpool_fini_percpu_slots(struct objpool_head *pool)
100{
101 int i;
102
103 if (!pool->cpu_slots)
104 return;
105
106 for (i = 0; i < pool->nr_cpus; i++)
107 kvfree(pool->cpu_slots[i]);
108 kfree(pool->cpu_slots);
109}
110
111/* initialize object pool and pre-allocate objects */
112int objpool_init(struct objpool_head *pool, int nr_objs, int object_size,
113 gfp_t gfp, void *context, objpool_init_obj_cb objinit,
114 objpool_fini_cb release)
115{
116 int rc, capacity, slot_size;
117
118 /* check input parameters */
119 if (nr_objs <= 0 || nr_objs > OBJPOOL_NR_OBJECT_MAX ||
120 object_size <= 0 || object_size > OBJPOOL_OBJECT_SIZE_MAX)
121 return -EINVAL;
122
123 /* align up to unsigned long size */
124 object_size = ALIGN(object_size, sizeof(long));
125
126 /* calculate capacity of percpu objpool_slot */
127 capacity = roundup_pow_of_two(nr_objs);
128 if (!capacity)
129 return -EINVAL;
130
131 /* initialize objpool pool */
132 memset(pool, 0, sizeof(struct objpool_head));
133 pool->nr_cpus = nr_cpu_ids;
134 pool->obj_size = object_size;
135 pool->capacity = capacity;
136 pool->gfp = gfp & ~__GFP_ZERO;
137 pool->context = context;
138 pool->release = release;
139 slot_size = pool->nr_cpus * sizeof(struct objpool_slot);
140 pool->cpu_slots = kzalloc(slot_size, pool->gfp);
141 if (!pool->cpu_slots)
142 return -ENOMEM;
143
144 /* initialize per-cpu slots */
145 rc = objpool_init_percpu_slots(pool, nr_objs, context, objinit);
146 if (rc)
147 objpool_fini_percpu_slots(pool);
148 else
149 refcount_set(&pool->ref, pool->nr_objs + 1);
150
151 return rc;
152}
153EXPORT_SYMBOL_GPL(objpool_init);
154
155/* adding object to slot, abort if the slot was already full */
156static inline int
157objpool_try_add_slot(void *obj, struct objpool_head *pool, int cpu)
158{
159 struct objpool_slot *slot = pool->cpu_slots[cpu];
160 uint32_t head, tail;
161
162 /* loading tail and head as a local snapshot, tail first */
163 tail = READ_ONCE(slot->tail);
164
165 do {
166 head = READ_ONCE(slot->head);
167 /* fault caught: something must be wrong */
168 WARN_ON_ONCE(tail - head > pool->nr_objs);
169 } while (!try_cmpxchg_acquire(&slot->tail, &tail, tail + 1));
170
171 /* now the tail position is reserved for the given obj */
172 WRITE_ONCE(slot->entries[tail & slot->mask], obj);
173 /* update sequence to make this obj available for pop() */
174 smp_store_release(&slot->last, tail + 1);
175
176 return 0;
177}
178
179/* reclaim an object to object pool */
180int objpool_push(void *obj, struct objpool_head *pool)
181{
182 unsigned long flags;
183 int rc;
184
185 /* disable local irq to avoid preemption & interruption */
186 raw_local_irq_save(flags);
187 rc = objpool_try_add_slot(obj, pool, raw_smp_processor_id());
188 raw_local_irq_restore(flags);
189
190 return rc;
191}
192EXPORT_SYMBOL_GPL(objpool_push);
193
194/* try to retrieve object from slot */
195static inline void *objpool_try_get_slot(struct objpool_head *pool, int cpu)
196{
197 struct objpool_slot *slot = pool->cpu_slots[cpu];
198 /* load head snapshot, other cpus may change it */
199 uint32_t head = smp_load_acquire(&slot->head);
200
201 while (head != READ_ONCE(slot->last)) {
202 void *obj;
203
204 /*
205 * data visibility of 'last' and 'head' could be out of
206 * order since memory updating of 'last' and 'head' are
207 * performed in push() and pop() independently
208 *
209 * before any retrieving attempts, pop() must guarantee
210 * 'last' is behind 'head', that is to say, there must
211 * be available objects in slot, which could be ensured
212 * by condition 'last != head && last - head <= nr_objs'
213 * that is equivalent to 'last - head - 1 < nr_objs' as
214 * 'last' and 'head' are both unsigned int32
215 */
216 if (READ_ONCE(slot->last) - head - 1 >= pool->nr_objs) {
217 head = READ_ONCE(slot->head);
218 continue;
219 }
220
221 /* obj must be retrieved before moving forward head */
222 obj = READ_ONCE(slot->entries[head & slot->mask]);
223
224 /* move head forward to mark it's consumption */
225 if (try_cmpxchg_release(&slot->head, &head, head + 1))
226 return obj;
227 }
228
229 return NULL;
230}
231
232/* allocate an object from object pool */
233void *objpool_pop(struct objpool_head *pool)
234{
235 void *obj = NULL;
236 unsigned long flags;
237 int i, cpu;
238
239 /* disable local irq to avoid preemption & interruption */
240 raw_local_irq_save(flags);
241
242 cpu = raw_smp_processor_id();
243 for (i = 0; i < num_possible_cpus(); i++) {
244 obj = objpool_try_get_slot(pool, cpu);
245 if (obj)
246 break;
247 cpu = cpumask_next_wrap(cpu, cpu_possible_mask, -1, 1);
248 }
249 raw_local_irq_restore(flags);
250
251 return obj;
252}
253EXPORT_SYMBOL_GPL(objpool_pop);
254
255/* release whole objpool forcely */
256void objpool_free(struct objpool_head *pool)
257{
258 if (!pool->cpu_slots)
259 return;
260
261 /* release percpu slots */
262 objpool_fini_percpu_slots(pool);
263
264 /* call user's cleanup callback if provided */
265 if (pool->release)
266 pool->release(pool, pool->context);
267}
268EXPORT_SYMBOL_GPL(objpool_free);
269
270/* drop the allocated object, rather reclaim it to objpool */
271int objpool_drop(void *obj, struct objpool_head *pool)
272{
273 if (!obj || !pool)
274 return -EINVAL;
275
276 if (refcount_dec_and_test(&pool->ref)) {
277 objpool_free(pool);
278 return 0;
279 }
280
281 return -EAGAIN;
282}
283EXPORT_SYMBOL_GPL(objpool_drop);
284
285/* drop unused objects and defref objpool for releasing */
286void objpool_fini(struct objpool_head *pool)
287{
288 int count = 1; /* extra ref for objpool itself */
289
290 /* drop all remained objects from objpool */
291 while (objpool_pop(pool))
292 count++;
293
294 if (refcount_sub_and_test(count, &pool->ref))
295 objpool_free(pool);
296}
297EXPORT_SYMBOL_GPL(objpool_fini);