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);
298