1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * padata.c - generic interface to process data streams in parallel
   4 *
   5 * See Documentation/core-api/padata.rst for more information.
   6 *
   7 * Copyright (C) 2008, 2009 secunet Security Networks AG
   8 * Copyright (C) 2008, 2009 Steffen Klassert <steffen.klassert@secunet.com>
   9 *
  10 * Copyright (c) 2020 Oracle and/or its affiliates.
  11 * Author: Daniel Jordan <daniel.m.jordan@oracle.com>
 
 
 
 
 
 
 
 
 
 
 
 
 
  12 */
  13
  14#include <linux/completion.h>
  15#include <linux/export.h>
  16#include <linux/cpumask.h>
  17#include <linux/err.h>
  18#include <linux/cpu.h>
  19#include <linux/padata.h>
  20#include <linux/mutex.h>
  21#include <linux/sched.h>
  22#include <linux/slab.h>
  23#include <linux/sysfs.h>
  24#include <linux/rcupdate.h>
  25
  26#define	PADATA_WORK_ONSTACK	1	/* Work's memory is on stack */
  27
  28struct padata_work {
  29	struct work_struct	pw_work;
  30	struct list_head	pw_list;  /* padata_free_works linkage */
  31	void			*pw_data;
  32};
  33
  34static DEFINE_SPINLOCK(padata_works_lock);
  35static struct padata_work *padata_works;
  36static LIST_HEAD(padata_free_works);
  37
  38struct padata_mt_job_state {
  39	spinlock_t		lock;
  40	struct completion	completion;
  41	struct padata_mt_job	*job;
  42	int			nworks;
  43	int			nworks_fini;
  44	unsigned long		chunk_size;
  45};
  46
  47static void padata_free_pd(struct parallel_data *pd);
  48static void __init padata_mt_helper(struct work_struct *work);
  49
  50static int padata_index_to_cpu(struct parallel_data *pd, int cpu_index)
  51{
  52	int cpu, target_cpu;
  53
  54	target_cpu = cpumask_first(pd->cpumask.pcpu);
  55	for (cpu = 0; cpu < cpu_index; cpu++)
  56		target_cpu = cpumask_next(target_cpu, pd->cpumask.pcpu);
  57
  58	return target_cpu;
  59}
  60
  61static int padata_cpu_hash(struct parallel_data *pd, unsigned int seq_nr)
  62{
  63	/*
  64	 * Hash the sequence numbers to the cpus by taking
  65	 * seq_nr mod. number of cpus in use.
  66	 */
  67	int cpu_index = seq_nr % cpumask_weight(pd->cpumask.pcpu);
  68
  69	return padata_index_to_cpu(pd, cpu_index);
  70}
  71
  72static struct padata_work *padata_work_alloc(void)
  73{
  74	struct padata_work *pw;
  75
  76	lockdep_assert_held(&padata_works_lock);
  77
  78	if (list_empty(&padata_free_works))
  79		return NULL;	/* No more work items allowed to be queued. */
  80
  81	pw = list_first_entry(&padata_free_works, struct padata_work, pw_list);
  82	list_del(&pw->pw_list);
  83	return pw;
  84}
  85
  86/*
  87 * This function is marked __ref because this function may be optimized in such
  88 * a way that it directly refers to work_fn's address, which causes modpost to
  89 * complain when work_fn is marked __init. This scenario was observed with clang
  90 * LTO, where padata_work_init() was optimized to refer directly to
  91 * padata_mt_helper() because the calls to padata_work_init() with other work_fn
  92 * values were eliminated or inlined.
  93 */
  94static void __ref padata_work_init(struct padata_work *pw, work_func_t work_fn,
  95				   void *data, int flags)
  96{
  97	if (flags & PADATA_WORK_ONSTACK)
  98		INIT_WORK_ONSTACK(&pw->pw_work, work_fn);
  99	else
 100		INIT_WORK(&pw->pw_work, work_fn);
 101	pw->pw_data = data;
 102}
 103
 104static int __init padata_work_alloc_mt(int nworks, void *data,
 105				       struct list_head *head)
 106{
 107	int i;
 108
 109	spin_lock(&padata_works_lock);
 110	/* Start at 1 because the current task participates in the job. */
 111	for (i = 1; i < nworks; ++i) {
 112		struct padata_work *pw = padata_work_alloc();
 113
 114		if (!pw)
 115			break;
 116		padata_work_init(pw, padata_mt_helper, data, 0);
 117		list_add(&pw->pw_list, head);
 118	}
 119	spin_unlock(&padata_works_lock);
 120
 121	return i;
 122}
 123
 124static void padata_work_free(struct padata_work *pw)
 125{
 126	lockdep_assert_held(&padata_works_lock);
 127	list_add(&pw->pw_list, &padata_free_works);
 128}
 129
 130static void __init padata_works_free(struct list_head *works)
 131{
 132	struct padata_work *cur, *next;
 133
 134	if (list_empty(works))
 135		return;
 136
 137	spin_lock(&padata_works_lock);
 138	list_for_each_entry_safe(cur, next, works, pw_list) {
 139		list_del(&cur->pw_list);
 140		padata_work_free(cur);
 141	}
 142	spin_unlock(&padata_works_lock);
 143}
 144
 145static void padata_parallel_worker(struct work_struct *parallel_work)
 146{
 147	struct padata_work *pw = container_of(parallel_work, struct padata_work,
 148					      pw_work);
 149	struct padata_priv *padata = pw->pw_data;
 150
 151	local_bh_disable();
 152	padata->parallel(padata);
 153	spin_lock(&padata_works_lock);
 154	padata_work_free(pw);
 155	spin_unlock(&padata_works_lock);
 156	local_bh_enable();
 157}
 158
 159/**
 160 * padata_do_parallel - padata parallelization function
 161 *
 162 * @ps: padatashell
 163 * @padata: object to be parallelized
 164 * @cb_cpu: pointer to the CPU that the serialization callback function should
 165 *          run on.  If it's not in the serial cpumask of @pinst
 166 *          (i.e. cpumask.cbcpu), this function selects a fallback CPU and if
 167 *          none found, returns -EINVAL.
 168 *
 169 * The parallelization callback function will run with BHs off.
 170 * Note: Every object which is parallelized by padata_do_parallel
 171 * must be seen by padata_do_serial.
 172 *
 173 * Return: 0 on success or else negative error code.
 174 */
 175int padata_do_parallel(struct padata_shell *ps,
 176		       struct padata_priv *padata, int *cb_cpu)
 177{
 178	struct padata_instance *pinst = ps->pinst;
 179	int i, cpu, cpu_index, err;
 180	struct parallel_data *pd;
 181	struct padata_work *pw;
 182
 183	rcu_read_lock_bh();
 184
 185	pd = rcu_dereference_bh(ps->pd);
 186
 187	err = -EINVAL;
 188	if (!(pinst->flags & PADATA_INIT) || pinst->flags & PADATA_INVALID)
 189		goto out;
 190
 191	if (!cpumask_test_cpu(*cb_cpu, pd->cpumask.cbcpu)) {
 192		if (cpumask_empty(pd->cpumask.cbcpu))
 193			goto out;
 194
 195		/* Select an alternate fallback CPU and notify the caller. */
 196		cpu_index = *cb_cpu % cpumask_weight(pd->cpumask.cbcpu);
 197
 198		cpu = cpumask_first(pd->cpumask.cbcpu);
 199		for (i = 0; i < cpu_index; i++)
 200			cpu = cpumask_next(cpu, pd->cpumask.cbcpu);
 201
 202		*cb_cpu = cpu;
 203	}
 204
 205	err =  -EBUSY;
 206	if ((pinst->flags & PADATA_RESET))
 207		goto out;
 208
 209	refcount_inc(&pd->refcnt);
 210	padata->pd = pd;
 211	padata->cb_cpu = *cb_cpu;
 212
 213	spin_lock(&padata_works_lock);
 214	padata->seq_nr = ++pd->seq_nr;
 215	pw = padata_work_alloc();
 216	spin_unlock(&padata_works_lock);
 217
 218	if (!pw) {
 219		/* Maximum works limit exceeded, run in the current task. */
 220		padata->parallel(padata);
 221	}
 222
 223	rcu_read_unlock_bh();
 224
 225	if (pw) {
 226		padata_work_init(pw, padata_parallel_worker, padata, 0);
 227		queue_work(pinst->parallel_wq, &pw->pw_work);
 
 
 
 228	}
 229
 230	return 0;
 231out:
 232	rcu_read_unlock_bh();
 233
 234	return err;
 235}
 236EXPORT_SYMBOL(padata_do_parallel);
 237
 238/*
 239 * padata_find_next - Find the next object that needs serialization.
 240 *
 241 * Return:
 242 * * A pointer to the control struct of the next object that needs
 243 *   serialization, if present in one of the percpu reorder queues.
 244 * * NULL, if the next object that needs serialization will
 245 *   be parallel processed by another cpu and is not yet present in
 246 *   the cpu's reorder queue.
 247 */
 248static struct padata_priv *padata_find_next(struct parallel_data *pd,
 249					    bool remove_object)
 250{
 251	struct padata_priv *padata;
 252	struct padata_list *reorder;
 253	int cpu = pd->cpu;
 254
 255	reorder = per_cpu_ptr(pd->reorder_list, cpu);
 256
 257	spin_lock(&reorder->lock);
 258	if (list_empty(&reorder->list)) {
 259		spin_unlock(&reorder->lock);
 260		return NULL;
 261	}
 262
 263	padata = list_entry(reorder->list.next, struct padata_priv, list);
 264
 265	/*
 266	 * Checks the rare case where two or more parallel jobs have hashed to
 267	 * the same CPU and one of the later ones finishes first.
 268	 */
 269	if (padata->seq_nr != pd->processed) {
 270		spin_unlock(&reorder->lock);
 271		return NULL;
 272	}
 273
 274	if (remove_object) {
 275		list_del_init(&padata->list);
 276		++pd->processed;
 277		pd->cpu = cpumask_next_wrap(cpu, pd->cpumask.pcpu, -1, false);
 278	}
 279
 280	spin_unlock(&reorder->lock);
 281	return padata;
 282}
 283
 284static void padata_reorder(struct parallel_data *pd)
 285{
 286	struct padata_instance *pinst = pd->ps->pinst;
 287	int cb_cpu;
 288	struct padata_priv *padata;
 289	struct padata_serial_queue *squeue;
 290	struct padata_list *reorder;
 291
 292	/*
 293	 * We need to ensure that only one cpu can work on dequeueing of
 294	 * the reorder queue the time. Calculating in which percpu reorder
 295	 * queue the next object will arrive takes some time. A spinlock
 296	 * would be highly contended. Also it is not clear in which order
 297	 * the objects arrive to the reorder queues. So a cpu could wait to
 298	 * get the lock just to notice that there is nothing to do at the
 299	 * moment. Therefore we use a trylock and let the holder of the lock
 300	 * care for all the objects enqueued during the holdtime of the lock.
 301	 */
 302	if (!spin_trylock_bh(&pd->lock))
 303		return;
 304
 305	while (1) {
 306		padata = padata_find_next(pd, true);
 307
 308		/*
 309		 * If the next object that needs serialization is parallel
 310		 * processed by another cpu and is still on it's way to the
 311		 * cpu's reorder queue, nothing to do for now.
 312		 */
 313		if (!padata)
 314			break;
 315
 316		cb_cpu = padata->cb_cpu;
 317		squeue = per_cpu_ptr(pd->squeue, cb_cpu);
 318
 319		spin_lock(&squeue->serial.lock);
 320		list_add_tail(&padata->list, &squeue->serial.list);
 321		spin_unlock(&squeue->serial.lock);
 322
 323		queue_work_on(cb_cpu, pinst->serial_wq, &squeue->work);
 324	}
 325
 326	spin_unlock_bh(&pd->lock);
 327
 328	/*
 329	 * The next object that needs serialization might have arrived to
 330	 * the reorder queues in the meantime.
 331	 *
 332	 * Ensure reorder queue is read after pd->lock is dropped so we see
 333	 * new objects from another task in padata_do_serial.  Pairs with
 334	 * smp_mb in padata_do_serial.
 335	 */
 336	smp_mb();
 337
 338	reorder = per_cpu_ptr(pd->reorder_list, pd->cpu);
 339	if (!list_empty(&reorder->list) && padata_find_next(pd, false))
 340		queue_work(pinst->serial_wq, &pd->reorder_work);
 341}
 342
 343static void invoke_padata_reorder(struct work_struct *work)
 344{
 345	struct parallel_data *pd;
 346
 347	local_bh_disable();
 348	pd = container_of(work, struct parallel_data, reorder_work);
 349	padata_reorder(pd);
 350	local_bh_enable();
 351}
 352
 353static void padata_serial_worker(struct work_struct *serial_work)
 354{
 355	struct padata_serial_queue *squeue;
 356	struct parallel_data *pd;
 357	LIST_HEAD(local_list);
 358	int cnt;
 359
 360	local_bh_disable();
 361	squeue = container_of(serial_work, struct padata_serial_queue, work);
 362	pd = squeue->pd;
 363
 364	spin_lock(&squeue->serial.lock);
 365	list_replace_init(&squeue->serial.list, &local_list);
 366	spin_unlock(&squeue->serial.lock);
 367
 368	cnt = 0;
 369
 370	while (!list_empty(&local_list)) {
 371		struct padata_priv *padata;
 372
 373		padata = list_entry(local_list.next,
 374				    struct padata_priv, list);
 375
 376		list_del_init(&padata->list);
 377
 378		padata->serial(padata);
 379		cnt++;
 380	}
 381	local_bh_enable();
 382
 383	if (refcount_sub_and_test(cnt, &pd->refcnt))
 384		padata_free_pd(pd);
 385}
 386
 387/**
 388 * padata_do_serial - padata serialization function
 389 *
 390 * @padata: object to be serialized.
 391 *
 392 * padata_do_serial must be called for every parallelized object.
 393 * The serialization callback function will run with BHs off.
 394 */
 395void padata_do_serial(struct padata_priv *padata)
 396{
 397	struct parallel_data *pd = padata->pd;
 398	int hashed_cpu = padata_cpu_hash(pd, padata->seq_nr);
 399	struct padata_list *reorder = per_cpu_ptr(pd->reorder_list, hashed_cpu);
 400	struct padata_priv *cur;
 401	struct list_head *pos;
 402
 403	spin_lock(&reorder->lock);
 404	/* Sort in ascending order of sequence number. */
 405	list_for_each_prev(pos, &reorder->list) {
 406		cur = list_entry(pos, struct padata_priv, list);
 407		if (cur->seq_nr < padata->seq_nr)
 408			break;
 409	}
 410	list_add(&padata->list, pos);
 411	spin_unlock(&reorder->lock);
 412
 413	/*
 414	 * Ensure the addition to the reorder list is ordered correctly
 415	 * with the trylock of pd->lock in padata_reorder.  Pairs with smp_mb
 416	 * in padata_reorder.
 417	 */
 418	smp_mb();
 419
 420	padata_reorder(pd);
 421}
 422EXPORT_SYMBOL(padata_do_serial);
 423
 424static int padata_setup_cpumasks(struct padata_instance *pinst)
 425{
 426	struct workqueue_attrs *attrs;
 427	int err;
 428
 429	attrs = alloc_workqueue_attrs();
 430	if (!attrs)
 431		return -ENOMEM;
 432
 433	/* Restrict parallel_wq workers to pd->cpumask.pcpu. */
 434	cpumask_copy(attrs->cpumask, pinst->cpumask.pcpu);
 435	err = apply_workqueue_attrs(pinst->parallel_wq, attrs);
 436	free_workqueue_attrs(attrs);
 437
 438	return err;
 439}
 440
 441static void __init padata_mt_helper(struct work_struct *w)
 442{
 443	struct padata_work *pw = container_of(w, struct padata_work, pw_work);
 444	struct padata_mt_job_state *ps = pw->pw_data;
 445	struct padata_mt_job *job = ps->job;
 446	bool done;
 447
 448	spin_lock(&ps->lock);
 449
 450	while (job->size > 0) {
 451		unsigned long start, size, end;
 452
 453		start = job->start;
 454		/* So end is chunk size aligned if enough work remains. */
 455		size = roundup(start + 1, ps->chunk_size) - start;
 456		size = min(size, job->size);
 457		end = start + size;
 458
 459		job->start = end;
 460		job->size -= size;
 461
 462		spin_unlock(&ps->lock);
 463		job->thread_fn(start, end, job->fn_arg);
 464		spin_lock(&ps->lock);
 465	}
 466
 467	++ps->nworks_fini;
 468	done = (ps->nworks_fini == ps->nworks);
 469	spin_unlock(&ps->lock);
 470
 471	if (done)
 472		complete(&ps->completion);
 473}
 474
 475/**
 476 * padata_do_multithreaded - run a multithreaded job
 477 * @job: Description of the job.
 478 *
 479 * See the definition of struct padata_mt_job for more details.
 480 */
 481void __init padata_do_multithreaded(struct padata_mt_job *job)
 482{
 483	/* In case threads finish at different times. */
 484	static const unsigned long load_balance_factor = 4;
 485	struct padata_work my_work, *pw;
 486	struct padata_mt_job_state ps;
 487	LIST_HEAD(works);
 488	int nworks;
 489
 490	if (job->size == 0)
 491		return;
 492
 493	/* Ensure at least one thread when size < min_chunk. */
 494	nworks = max(job->size / job->min_chunk, 1ul);
 495	nworks = min(nworks, job->max_threads);
 496
 497	if (nworks == 1) {
 498		/* Single thread, no coordination needed, cut to the chase. */
 499		job->thread_fn(job->start, job->start + job->size, job->fn_arg);
 500		return;
 501	}
 502
 503	spin_lock_init(&ps.lock);
 504	init_completion(&ps.completion);
 505	ps.job	       = job;
 506	ps.nworks      = padata_work_alloc_mt(nworks, &ps, &works);
 507	ps.nworks_fini = 0;
 508
 509	/*
 510	 * Chunk size is the amount of work a helper does per call to the
 511	 * thread function.  Load balance large jobs between threads by
 512	 * increasing the number of chunks, guarantee at least the minimum
 513	 * chunk size from the caller, and honor the caller's alignment.
 514	 */
 515	ps.chunk_size = job->size / (ps.nworks * load_balance_factor);
 516	ps.chunk_size = max(ps.chunk_size, job->min_chunk);
 517	ps.chunk_size = roundup(ps.chunk_size, job->align);
 518
 519	list_for_each_entry(pw, &works, pw_list)
 520		queue_work(system_unbound_wq, &pw->pw_work);
 521
 522	/* Use the current thread, which saves starting a workqueue worker. */
 523	padata_work_init(&my_work, padata_mt_helper, &ps, PADATA_WORK_ONSTACK);
 524	padata_mt_helper(&my_work.pw_work);
 525
 526	/* Wait for all the helpers to finish. */
 527	wait_for_completion(&ps.completion);
 528
 529	destroy_work_on_stack(&my_work.pw_work);
 530	padata_works_free(&works);
 531}
 532
 533static void __padata_list_init(struct padata_list *pd_list)
 534{
 535	INIT_LIST_HEAD(&pd_list->list);
 536	spin_lock_init(&pd_list->lock);
 537}
 538
 539/* Initialize all percpu queues used by serial workers */
 540static void padata_init_squeues(struct parallel_data *pd)
 541{
 542	int cpu;
 543	struct padata_serial_queue *squeue;
 544
 545	for_each_cpu(cpu, pd->cpumask.cbcpu) {
 546		squeue = per_cpu_ptr(pd->squeue, cpu);
 547		squeue->pd = pd;
 548		__padata_list_init(&squeue->serial);
 549		INIT_WORK(&squeue->work, padata_serial_worker);
 550	}
 551}
 552
 553/* Initialize per-CPU reorder lists */
 554static void padata_init_reorder_list(struct parallel_data *pd)
 555{
 556	int cpu;
 557	struct padata_list *list;
 558
 559	for_each_cpu(cpu, pd->cpumask.pcpu) {
 560		list = per_cpu_ptr(pd->reorder_list, cpu);
 561		__padata_list_init(list);
 562	}
 563}
 564
 565/* Allocate and initialize the internal cpumask dependend resources. */
 566static struct parallel_data *padata_alloc_pd(struct padata_shell *ps)
 567{
 568	struct padata_instance *pinst = ps->pinst;
 569	struct parallel_data *pd;
 570
 571	pd = kzalloc(sizeof(struct parallel_data), GFP_KERNEL);
 572	if (!pd)
 573		goto err;
 574
 575	pd->reorder_list = alloc_percpu(struct padata_list);
 576	if (!pd->reorder_list)
 577		goto err_free_pd;
 578
 579	pd->squeue = alloc_percpu(struct padata_serial_queue);
 580	if (!pd->squeue)
 581		goto err_free_reorder_list;
 582
 583	pd->ps = ps;
 584
 585	if (!alloc_cpumask_var(&pd->cpumask.pcpu, GFP_KERNEL))
 586		goto err_free_squeue;
 587	if (!alloc_cpumask_var(&pd->cpumask.cbcpu, GFP_KERNEL))
 588		goto err_free_pcpu;
 589
 590	cpumask_and(pd->cpumask.pcpu, pinst->cpumask.pcpu, cpu_online_mask);
 591	cpumask_and(pd->cpumask.cbcpu, pinst->cpumask.cbcpu, cpu_online_mask);
 592
 593	padata_init_reorder_list(pd);
 594	padata_init_squeues(pd);
 595	pd->seq_nr = -1;
 596	refcount_set(&pd->refcnt, 1);
 597	spin_lock_init(&pd->lock);
 598	pd->cpu = cpumask_first(pd->cpumask.pcpu);
 599	INIT_WORK(&pd->reorder_work, invoke_padata_reorder);
 600
 601	return pd;
 602
 603err_free_pcpu:
 604	free_cpumask_var(pd->cpumask.pcpu);
 605err_free_squeue:
 606	free_percpu(pd->squeue);
 607err_free_reorder_list:
 608	free_percpu(pd->reorder_list);
 609err_free_pd:
 610	kfree(pd);
 611err:
 612	return NULL;
 613}
 614
 615static void padata_free_pd(struct parallel_data *pd)
 616{
 617	free_cpumask_var(pd->cpumask.pcpu);
 618	free_cpumask_var(pd->cpumask.cbcpu);
 619	free_percpu(pd->reorder_list);
 620	free_percpu(pd->squeue);
 621	kfree(pd);
 622}
 623
 624static void __padata_start(struct padata_instance *pinst)
 625{
 626	pinst->flags |= PADATA_INIT;
 627}
 628
 629static void __padata_stop(struct padata_instance *pinst)
 630{
 631	if (!(pinst->flags & PADATA_INIT))
 632		return;
 633
 634	pinst->flags &= ~PADATA_INIT;
 635
 636	synchronize_rcu();
 637}
 638
 639/* Replace the internal control structure with a new one. */
 640static int padata_replace_one(struct padata_shell *ps)
 641{
 642	struct parallel_data *pd_new;
 643
 644	pd_new = padata_alloc_pd(ps);
 645	if (!pd_new)
 646		return -ENOMEM;
 647
 648	ps->opd = rcu_dereference_protected(ps->pd, 1);
 649	rcu_assign_pointer(ps->pd, pd_new);
 650
 651	return 0;
 652}
 653
 654static int padata_replace(struct padata_instance *pinst)
 655{
 656	struct padata_shell *ps;
 657	int err = 0;
 658
 659	pinst->flags |= PADATA_RESET;
 660
 661	list_for_each_entry(ps, &pinst->pslist, list) {
 662		err = padata_replace_one(ps);
 663		if (err)
 664			break;
 665	}
 666
 667	synchronize_rcu();
 668
 669	list_for_each_entry_continue_reverse(ps, &pinst->pslist, list)
 670		if (refcount_dec_and_test(&ps->opd->refcnt))
 671			padata_free_pd(ps->opd);
 672
 673	pinst->flags &= ~PADATA_RESET;
 674
 675	return err;
 676}
 677
 678/* If cpumask contains no active cpu, we mark the instance as invalid. */
 679static bool padata_validate_cpumask(struct padata_instance *pinst,
 680				    const struct cpumask *cpumask)
 681{
 682	if (!cpumask_intersects(cpumask, cpu_online_mask)) {
 683		pinst->flags |= PADATA_INVALID;
 684		return false;
 685	}
 686
 687	pinst->flags &= ~PADATA_INVALID;
 688	return true;
 689}
 690
 691static int __padata_set_cpumasks(struct padata_instance *pinst,
 692				 cpumask_var_t pcpumask,
 693				 cpumask_var_t cbcpumask)
 694{
 695	int valid;
 696	int err;
 697
 698	valid = padata_validate_cpumask(pinst, pcpumask);
 699	if (!valid) {
 700		__padata_stop(pinst);
 701		goto out_replace;
 702	}
 703
 704	valid = padata_validate_cpumask(pinst, cbcpumask);
 705	if (!valid)
 706		__padata_stop(pinst);
 707
 708out_replace:
 709	cpumask_copy(pinst->cpumask.pcpu, pcpumask);
 710	cpumask_copy(pinst->cpumask.cbcpu, cbcpumask);
 711
 712	err = padata_setup_cpumasks(pinst) ?: padata_replace(pinst);
 713
 714	if (valid)
 715		__padata_start(pinst);
 716
 717	return err;
 718}
 719
 720/**
 721 * padata_set_cpumask - Sets specified by @cpumask_type cpumask to the value
 722 *                      equivalent to @cpumask.
 723 * @pinst: padata instance
 724 * @cpumask_type: PADATA_CPU_SERIAL or PADATA_CPU_PARALLEL corresponding
 725 *                to parallel and serial cpumasks respectively.
 726 * @cpumask: the cpumask to use
 727 *
 728 * Return: 0 on success or negative error code
 729 */
 730int padata_set_cpumask(struct padata_instance *pinst, int cpumask_type,
 731		       cpumask_var_t cpumask)
 732{
 733	struct cpumask *serial_mask, *parallel_mask;
 734	int err = -EINVAL;
 735
 736	cpus_read_lock();
 737	mutex_lock(&pinst->lock);
 738
 739	switch (cpumask_type) {
 740	case PADATA_CPU_PARALLEL:
 741		serial_mask = pinst->cpumask.cbcpu;
 742		parallel_mask = cpumask;
 743		break;
 744	case PADATA_CPU_SERIAL:
 745		parallel_mask = pinst->cpumask.pcpu;
 746		serial_mask = cpumask;
 747		break;
 748	default:
 749		 goto out;
 750	}
 751
 752	err =  __padata_set_cpumasks(pinst, parallel_mask, serial_mask);
 753
 754out:
 755	mutex_unlock(&pinst->lock);
 756	cpus_read_unlock();
 757
 758	return err;
 759}
 760EXPORT_SYMBOL(padata_set_cpumask);
 761
 762#ifdef CONFIG_HOTPLUG_CPU
 763
 764static int __padata_add_cpu(struct padata_instance *pinst, int cpu)
 765{
 766	int err = 0;
 767
 768	if (cpumask_test_cpu(cpu, cpu_online_mask)) {
 769		err = padata_replace(pinst);
 770
 771		if (padata_validate_cpumask(pinst, pinst->cpumask.pcpu) &&
 772		    padata_validate_cpumask(pinst, pinst->cpumask.cbcpu))
 773			__padata_start(pinst);
 774	}
 775
 776	return err;
 777}
 778
 779static int __padata_remove_cpu(struct padata_instance *pinst, int cpu)
 780{
 781	int err = 0;
 782
 783	if (!cpumask_test_cpu(cpu, cpu_online_mask)) {
 784		if (!padata_validate_cpumask(pinst, pinst->cpumask.pcpu) ||
 785		    !padata_validate_cpumask(pinst, pinst->cpumask.cbcpu))
 786			__padata_stop(pinst);
 787
 788		err = padata_replace(pinst);
 789	}
 790
 791	return err;
 792}
 793
 794static inline int pinst_has_cpu(struct padata_instance *pinst, int cpu)
 795{
 796	return cpumask_test_cpu(cpu, pinst->cpumask.pcpu) ||
 797		cpumask_test_cpu(cpu, pinst->cpumask.cbcpu);
 798}
 799
 800static int padata_cpu_online(unsigned int cpu, struct hlist_node *node)
 801{
 802	struct padata_instance *pinst;
 803	int ret;
 804
 805	pinst = hlist_entry_safe(node, struct padata_instance, cpu_online_node);
 806	if (!pinst_has_cpu(pinst, cpu))
 807		return 0;
 808
 809	mutex_lock(&pinst->lock);
 810	ret = __padata_add_cpu(pinst, cpu);
 811	mutex_unlock(&pinst->lock);
 812	return ret;
 813}
 814
 815static int padata_cpu_dead(unsigned int cpu, struct hlist_node *node)
 816{
 817	struct padata_instance *pinst;
 818	int ret;
 819
 820	pinst = hlist_entry_safe(node, struct padata_instance, cpu_dead_node);
 821	if (!pinst_has_cpu(pinst, cpu))
 822		return 0;
 823
 824	mutex_lock(&pinst->lock);
 825	ret = __padata_remove_cpu(pinst, cpu);
 826	mutex_unlock(&pinst->lock);
 827	return ret;
 828}
 829
 830static enum cpuhp_state hp_online;
 831#endif
 832
 833static void __padata_free(struct padata_instance *pinst)
 834{
 835#ifdef CONFIG_HOTPLUG_CPU
 836	cpuhp_state_remove_instance_nocalls(CPUHP_PADATA_DEAD,
 837					    &pinst->cpu_dead_node);
 838	cpuhp_state_remove_instance_nocalls(hp_online, &pinst->cpu_online_node);
 839#endif
 840
 841	WARN_ON(!list_empty(&pinst->pslist));
 842
 843	free_cpumask_var(pinst->cpumask.pcpu);
 844	free_cpumask_var(pinst->cpumask.cbcpu);
 845	destroy_workqueue(pinst->serial_wq);
 846	destroy_workqueue(pinst->parallel_wq);
 847	kfree(pinst);
 848}
 849
 850#define kobj2pinst(_kobj)					\
 851	container_of(_kobj, struct padata_instance, kobj)
 852#define attr2pentry(_attr)					\
 853	container_of(_attr, struct padata_sysfs_entry, attr)
 854
 855static void padata_sysfs_release(struct kobject *kobj)
 856{
 857	struct padata_instance *pinst = kobj2pinst(kobj);
 858	__padata_free(pinst);
 859}
 860
 861struct padata_sysfs_entry {
 862	struct attribute attr;
 863	ssize_t (*show)(struct padata_instance *, struct attribute *, char *);
 864	ssize_t (*store)(struct padata_instance *, struct attribute *,
 865			 const char *, size_t);
 866};
 867
 868static ssize_t show_cpumask(struct padata_instance *pinst,
 869			    struct attribute *attr,  char *buf)
 870{
 871	struct cpumask *cpumask;
 872	ssize_t len;
 873
 874	mutex_lock(&pinst->lock);
 875	if (!strcmp(attr->name, "serial_cpumask"))
 876		cpumask = pinst->cpumask.cbcpu;
 877	else
 878		cpumask = pinst->cpumask.pcpu;
 879
 880	len = snprintf(buf, PAGE_SIZE, "%*pb\n",
 881		       nr_cpu_ids, cpumask_bits(cpumask));
 882	mutex_unlock(&pinst->lock);
 883	return len < PAGE_SIZE ? len : -EINVAL;
 884}
 885
 886static ssize_t store_cpumask(struct padata_instance *pinst,
 887			     struct attribute *attr,
 888			     const char *buf, size_t count)
 889{
 890	cpumask_var_t new_cpumask;
 891	ssize_t ret;
 892	int mask_type;
 893
 894	if (!alloc_cpumask_var(&new_cpumask, GFP_KERNEL))
 895		return -ENOMEM;
 896
 897	ret = bitmap_parse(buf, count, cpumask_bits(new_cpumask),
 898			   nr_cpumask_bits);
 899	if (ret < 0)
 900		goto out;
 901
 902	mask_type = !strcmp(attr->name, "serial_cpumask") ?
 903		PADATA_CPU_SERIAL : PADATA_CPU_PARALLEL;
 904	ret = padata_set_cpumask(pinst, mask_type, new_cpumask);
 905	if (!ret)
 906		ret = count;
 907
 908out:
 909	free_cpumask_var(new_cpumask);
 910	return ret;
 911}
 912
 913#define PADATA_ATTR_RW(_name, _show_name, _store_name)		\
 914	static struct padata_sysfs_entry _name##_attr =		\
 915		__ATTR(_name, 0644, _show_name, _store_name)
 916#define PADATA_ATTR_RO(_name, _show_name)		\
 917	static struct padata_sysfs_entry _name##_attr = \
 918		__ATTR(_name, 0400, _show_name, NULL)
 919
 920PADATA_ATTR_RW(serial_cpumask, show_cpumask, store_cpumask);
 921PADATA_ATTR_RW(parallel_cpumask, show_cpumask, store_cpumask);
 922
 923/*
 924 * Padata sysfs provides the following objects:
 925 * serial_cpumask   [RW] - cpumask for serial workers
 926 * parallel_cpumask [RW] - cpumask for parallel workers
 927 */
 928static struct attribute *padata_default_attrs[] = {
 929	&serial_cpumask_attr.attr,
 930	&parallel_cpumask_attr.attr,
 931	NULL,
 932};
 933ATTRIBUTE_GROUPS(padata_default);
 934
 935static ssize_t padata_sysfs_show(struct kobject *kobj,
 936				 struct attribute *attr, char *buf)
 937{
 938	struct padata_instance *pinst;
 939	struct padata_sysfs_entry *pentry;
 940	ssize_t ret = -EIO;
 941
 942	pinst = kobj2pinst(kobj);
 943	pentry = attr2pentry(attr);
 944	if (pentry->show)
 945		ret = pentry->show(pinst, attr, buf);
 946
 947	return ret;
 948}
 949
 950static ssize_t padata_sysfs_store(struct kobject *kobj, struct attribute *attr,
 951				  const char *buf, size_t count)
 952{
 953	struct padata_instance *pinst;
 954	struct padata_sysfs_entry *pentry;
 955	ssize_t ret = -EIO;
 956
 957	pinst = kobj2pinst(kobj);
 958	pentry = attr2pentry(attr);
 959	if (pentry->show)
 960		ret = pentry->store(pinst, attr, buf, count);
 961
 962	return ret;
 963}
 964
 965static const struct sysfs_ops padata_sysfs_ops = {
 966	.show = padata_sysfs_show,
 967	.store = padata_sysfs_store,
 968};
 969
 970static struct kobj_type padata_attr_type = {
 971	.sysfs_ops = &padata_sysfs_ops,
 972	.default_groups = padata_default_groups,
 973	.release = padata_sysfs_release,
 974};
 975
 976/**
 977 * padata_alloc - allocate and initialize a padata instance
 978 * @name: used to identify the instance
 979 *
 980 * Return: new instance on success, NULL on error
 981 */
 982struct padata_instance *padata_alloc(const char *name)
 983{
 984	struct padata_instance *pinst;
 985
 986	pinst = kzalloc(sizeof(struct padata_instance), GFP_KERNEL);
 987	if (!pinst)
 988		goto err;
 989
 990	pinst->parallel_wq = alloc_workqueue("%s_parallel", WQ_UNBOUND, 0,
 991					     name);
 992	if (!pinst->parallel_wq)
 993		goto err_free_inst;
 994
 995	cpus_read_lock();
 996
 997	pinst->serial_wq = alloc_workqueue("%s_serial", WQ_MEM_RECLAIM |
 998					   WQ_CPU_INTENSIVE, 1, name);
 999	if (!pinst->serial_wq)
1000		goto err_put_cpus;
1001
1002	if (!alloc_cpumask_var(&pinst->cpumask.pcpu, GFP_KERNEL))
1003		goto err_free_serial_wq;
1004	if (!alloc_cpumask_var(&pinst->cpumask.cbcpu, GFP_KERNEL)) {
1005		free_cpumask_var(pinst->cpumask.pcpu);
1006		goto err_free_serial_wq;
1007	}
1008
1009	INIT_LIST_HEAD(&pinst->pslist);
1010
1011	cpumask_copy(pinst->cpumask.pcpu, cpu_possible_mask);
1012	cpumask_copy(pinst->cpumask.cbcpu, cpu_possible_mask);
1013
1014	if (padata_setup_cpumasks(pinst))
1015		goto err_free_masks;
1016
1017	__padata_start(pinst);
1018
1019	kobject_init(&pinst->kobj, &padata_attr_type);
1020	mutex_init(&pinst->lock);
1021
1022#ifdef CONFIG_HOTPLUG_CPU
1023	cpuhp_state_add_instance_nocalls_cpuslocked(hp_online,
1024						    &pinst->cpu_online_node);
1025	cpuhp_state_add_instance_nocalls_cpuslocked(CPUHP_PADATA_DEAD,
1026						    &pinst->cpu_dead_node);
1027#endif
1028
1029	cpus_read_unlock();
1030
1031	return pinst;
1032
1033err_free_masks:
1034	free_cpumask_var(pinst->cpumask.pcpu);
1035	free_cpumask_var(pinst->cpumask.cbcpu);
1036err_free_serial_wq:
1037	destroy_workqueue(pinst->serial_wq);
1038err_put_cpus:
1039	cpus_read_unlock();
1040	destroy_workqueue(pinst->parallel_wq);
1041err_free_inst:
1042	kfree(pinst);
1043err:
1044	return NULL;
1045}
1046EXPORT_SYMBOL(padata_alloc);
1047
1048/**
1049 * padata_free - free a padata instance
1050 *
1051 * @pinst: padata instance to free
1052 */
1053void padata_free(struct padata_instance *pinst)
1054{
1055	kobject_put(&pinst->kobj);
1056}
1057EXPORT_SYMBOL(padata_free);
1058
1059/**
1060 * padata_alloc_shell - Allocate and initialize padata shell.
1061 *
1062 * @pinst: Parent padata_instance object.
1063 *
1064 * Return: new shell on success, NULL on error
1065 */
1066struct padata_shell *padata_alloc_shell(struct padata_instance *pinst)
1067{
1068	struct parallel_data *pd;
1069	struct padata_shell *ps;
1070
1071	ps = kzalloc(sizeof(*ps), GFP_KERNEL);
1072	if (!ps)
1073		goto out;
1074
1075	ps->pinst = pinst;
1076
1077	cpus_read_lock();
1078	pd = padata_alloc_pd(ps);
1079	cpus_read_unlock();
1080
1081	if (!pd)
1082		goto out_free_ps;
1083
1084	mutex_lock(&pinst->lock);
1085	RCU_INIT_POINTER(ps->pd, pd);
1086	list_add(&ps->list, &pinst->pslist);
1087	mutex_unlock(&pinst->lock);
1088
1089	return ps;
1090
1091out_free_ps:
1092	kfree(ps);
1093out:
1094	return NULL;
1095}
1096EXPORT_SYMBOL(padata_alloc_shell);
1097
1098/**
1099 * padata_free_shell - free a padata shell
1100 *
1101 * @ps: padata shell to free
1102 */
1103void padata_free_shell(struct padata_shell *ps)
1104{
1105	if (!ps)
1106		return;
1107
1108	mutex_lock(&ps->pinst->lock);
1109	list_del(&ps->list);
1110	padata_free_pd(rcu_dereference_protected(ps->pd, 1));
1111	mutex_unlock(&ps->pinst->lock);
1112
1113	kfree(ps);
1114}
1115EXPORT_SYMBOL(padata_free_shell);
1116
1117void __init padata_init(void)
1118{
1119	unsigned int i, possible_cpus;
1120#ifdef CONFIG_HOTPLUG_CPU
1121	int ret;
1122
1123	ret = cpuhp_setup_state_multi(CPUHP_AP_ONLINE_DYN, "padata:online",
1124				      padata_cpu_online, NULL);
1125	if (ret < 0)
1126		goto err;
1127	hp_online = ret;
1128
1129	ret = cpuhp_setup_state_multi(CPUHP_PADATA_DEAD, "padata:dead",
1130				      NULL, padata_cpu_dead);
1131	if (ret < 0)
1132		goto remove_online_state;
1133#endif
1134
1135	possible_cpus = num_possible_cpus();
1136	padata_works = kmalloc_array(possible_cpus, sizeof(struct padata_work),
1137				     GFP_KERNEL);
1138	if (!padata_works)
1139		goto remove_dead_state;
1140
1141	for (i = 0; i < possible_cpus; ++i)
1142		list_add(&padata_works[i].pw_list, &padata_free_works);
1143
1144	return;
1145
1146remove_dead_state:
1147#ifdef CONFIG_HOTPLUG_CPU
1148	cpuhp_remove_multi_state(CPUHP_PADATA_DEAD);
1149remove_online_state:
1150	cpuhp_remove_multi_state(hp_online);
1151err:
1152#endif
1153	pr_warn("padata: initialization failed\n");
1154}