// SPDX-License-Identifier: GPL-2.0

  /*
   * padata.c - generic interface to process data streams in parallel
   *

   * See Documentation/core-api/padata.rst for more information.

   *

   * Copyright (C) 2008, 2009 secunet Security Networks AG
   * Copyright (C) 2008, 2009 Steffen Klassert <steffen.klassert@secunet.com>
   *

   * Copyright (c) 2020 Oracle and/or its affiliates.
   * Author: Daniel Jordan <daniel.m.jordan@oracle.com>
   *

   * This program is free software; you can redistribute it and/or modify it
   * under the terms and conditions of the GNU General Public License,
   * version 2, as published by the Free Software Foundation.
   *
   * This program is distributed in the hope it will be useful, but WITHOUT
   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
   * more details.
   *
   * You should have received a copy of the GNU General Public License along with
   * this program; if not, write to the Free Software Foundation, Inc.,
   * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
   */

  #include <linux/completion.h>

  #include <linux/export.h>

  #include <linux/cpumask.h>
  #include <linux/err.h>
  #include <linux/cpu.h>
  #include <linux/padata.h>
  #include <linux/mutex.h>
  #include <linux/sched.h>

  #include <linux/slab.h>

  #include <linux/sysfs.h>

  #include <linux/rcupdate.h>

  #define	PADATA_WORK_ONSTACK	1	/* Work's memory is on stack */

  struct padata_work {
  	struct work_struct	pw_work;
  	struct list_head	pw_list;  /* padata_free_works linkage */
  	void			*pw_data;
  };
  
  static DEFINE_SPINLOCK(padata_works_lock);
  static struct padata_work *padata_works;
  static LIST_HEAD(padata_free_works);

  struct padata_mt_job_state {
  	spinlock_t		lock;
  	struct completion	completion;
  	struct padata_mt_job	*job;
  	int			nworks;
  	int			nworks_fini;
  	unsigned long		chunk_size;
  };

  static void padata_free_pd(struct parallel_data *pd);

  static void __init padata_mt_helper(struct work_struct *work);

  static int padata_index_to_cpu(struct parallel_data *pd, int cpu_index)
  {
  	int cpu, target_cpu;

  	target_cpu = cpumask_first(pd->cpumask.pcpu);

  	for (cpu = 0; cpu < cpu_index; cpu++)

  		target_cpu = cpumask_next(target_cpu, pd->cpumask.pcpu);

  
  	return target_cpu;
  }

  static int padata_cpu_hash(struct parallel_data *pd, unsigned int seq_nr)

  {

  	/*
  	 * Hash the sequence numbers to the cpus by taking
  	 * seq_nr mod. number of cpus in use.
  	 */

  	int cpu_index = seq_nr % cpumask_weight(pd->cpumask.pcpu);

  
  	return padata_index_to_cpu(pd, cpu_index);
  }

  static struct padata_work *padata_work_alloc(void)

  {

  	struct padata_work *pw;

  	lockdep_assert_held(&padata_works_lock);

  	if (list_empty(&padata_free_works))
  		return NULL;	/* No more work items allowed to be queued. */

  	pw = list_first_entry(&padata_free_works, struct padata_work, pw_list);
  	list_del(&pw->pw_list);
  	return pw;
  }

  static void padata_work_init(struct padata_work *pw, work_func_t work_fn,

  			     void *data, int flags)

  {

  	if (flags & PADATA_WORK_ONSTACK)
  		INIT_WORK_ONSTACK(&pw->pw_work, work_fn);
  	else
  		INIT_WORK(&pw->pw_work, work_fn);

  	pw->pw_data = data;
  }

  static int __init padata_work_alloc_mt(int nworks, void *data,
  				       struct list_head *head)
  {
  	int i;
  
  	spin_lock(&padata_works_lock);
  	/* Start at 1 because the current task participates in the job. */
  	for (i = 1; i < nworks; ++i) {
  		struct padata_work *pw = padata_work_alloc();
  
  		if (!pw)
  			break;
  		padata_work_init(pw, padata_mt_helper, data, 0);
  		list_add(&pw->pw_list, head);
  	}
  	spin_unlock(&padata_works_lock);
  
  	return i;
  }

  static void padata_work_free(struct padata_work *pw)
  {
  	lockdep_assert_held(&padata_works_lock);
  	list_add(&pw->pw_list, &padata_free_works);
  }

  static void __init padata_works_free(struct list_head *works)
  {
  	struct padata_work *cur, *next;
  
  	if (list_empty(works))
  		return;
  
  	spin_lock(&padata_works_lock);
  	list_for_each_entry_safe(cur, next, works, pw_list) {
  		list_del(&cur->pw_list);
  		padata_work_free(cur);
  	}
  	spin_unlock(&padata_works_lock);
  }

  static void padata_parallel_worker(struct work_struct *parallel_work)
  {
  	struct padata_work *pw = container_of(parallel_work, struct padata_work,
  					      pw_work);
  	struct padata_priv *padata = pw->pw_data;

  	local_bh_disable();
  	padata->parallel(padata);
  	spin_lock(&padata_works_lock);
  	padata_work_free(pw);
  	spin_unlock(&padata_works_lock);

  	local_bh_enable();
  }

  /**

   * padata_do_parallel - padata parallelization function
   *

   * @ps: padatashell

   * @padata: object to be parallelized

   * @cb_cpu: pointer to the CPU that the serialization callback function should
   *          run on.  If it's not in the serial cpumask of @pinst
   *          (i.e. cpumask.cbcpu), this function selects a fallback CPU and if
   *          none found, returns -EINVAL.

   *
   * The parallelization callback function will run with BHs off.
   * Note: Every object which is parallelized by padata_do_parallel
   * must be seen by padata_do_serial.

   *
   * Return: 0 on success or else negative error code.

   */

  int padata_do_parallel(struct padata_shell *ps,

  		       struct padata_priv *padata, int *cb_cpu)

  {

  	struct padata_instance *pinst = ps->pinst;

  	int i, cpu, cpu_index, err;

  	struct parallel_data *pd;

  	struct padata_work *pw;

  
  	rcu_read_lock_bh();

  	pd = rcu_dereference_bh(ps->pd);

  	err = -EINVAL;

  	if (!(pinst->flags & PADATA_INIT) || pinst->flags & PADATA_INVALID)

  		goto out;

  	if (!cpumask_test_cpu(*cb_cpu, pd->cpumask.cbcpu)) {
  		if (!cpumask_weight(pd->cpumask.cbcpu))
  			goto out;
  
  		/* Select an alternate fallback CPU and notify the caller. */
  		cpu_index = *cb_cpu % cpumask_weight(pd->cpumask.cbcpu);
  
  		cpu = cpumask_first(pd->cpumask.cbcpu);
  		for (i = 0; i < cpu_index; i++)
  			cpu = cpumask_next(cpu, pd->cpumask.cbcpu);
  
  		*cb_cpu = cpu;
  	}

  
  	err =  -EBUSY;
  	if ((pinst->flags & PADATA_RESET))
  		goto out;

  	atomic_inc(&pd->refcnt);
  	padata->pd = pd;

  	padata->cb_cpu = *cb_cpu;

  	spin_lock(&padata_works_lock);
  	padata->seq_nr = ++pd->seq_nr;
  	pw = padata_work_alloc();
  	spin_unlock(&padata_works_lock);

  
  	rcu_read_unlock_bh();

  	if (pw) {

  		padata_work_init(pw, padata_parallel_worker, padata, 0);

  		queue_work(pinst->parallel_wq, &pw->pw_work);
  	} else {
  		/* Maximum works limit exceeded, run in the current task. */
  		padata->parallel(padata);
  	}

  	return 0;

  out:
  	rcu_read_unlock_bh();
  
  	return err;
  }
  EXPORT_SYMBOL(padata_do_parallel);

  /*

   * padata_find_next - Find the next object that needs serialization.

   *

   * Return:
   * * A pointer to the control struct of the next object that needs
   *   serialization, if present in one of the percpu reorder queues.
   * * NULL, if the next object that needs serialization will
   *   be parallel processed by another cpu and is not yet present in
   *   the cpu's reorder queue.

   */

  static struct padata_priv *padata_find_next(struct parallel_data *pd,
  					    bool remove_object)

  {

  	struct padata_priv *padata;
  	struct padata_list *reorder;

  	int cpu = pd->cpu;

  	reorder = per_cpu_ptr(pd->reorder_list, cpu);

  	spin_lock(&reorder->lock);

  	if (list_empty(&reorder->list)) {
  		spin_unlock(&reorder->lock);
  		return NULL;
  	}

  	padata = list_entry(reorder->list.next, struct padata_priv, list);

  	/*
  	 * Checks the rare case where two or more parallel jobs have hashed to
  	 * the same CPU and one of the later ones finishes first.
  	 */
  	if (padata->seq_nr != pd->processed) {

  		spin_unlock(&reorder->lock);

  		return NULL;

  	}

  	if (remove_object) {
  		list_del_init(&padata->list);

  		++pd->processed;
  		pd->cpu = cpumask_next_wrap(cpu, pd->cpumask.pcpu, -1, false);

  	}

  	spin_unlock(&reorder->lock);

  	return padata;
  }
  
  static void padata_reorder(struct parallel_data *pd)
  {

  	struct padata_instance *pinst = pd->ps->pinst;

  	int cb_cpu;

  	struct padata_priv *padata;

  	struct padata_serial_queue *squeue;

  	struct padata_list *reorder;

  	/*
  	 * We need to ensure that only one cpu can work on dequeueing of
  	 * the reorder queue the time. Calculating in which percpu reorder
  	 * queue the next object will arrive takes some time. A spinlock
  	 * would be highly contended. Also it is not clear in which order
  	 * the objects arrive to the reorder queues. So a cpu could wait to
  	 * get the lock just to notice that there is nothing to do at the
  	 * moment. Therefore we use a trylock and let the holder of the lock
  	 * care for all the objects enqueued during the holdtime of the lock.
  	 */

  	if (!spin_trylock_bh(&pd->lock))

  		return;

  
  	while (1) {

  		padata = padata_find_next(pd, true);

  		/*

  		 * If the next object that needs serialization is parallel
  		 * processed by another cpu and is still on it's way to the
  		 * cpu's reorder queue, nothing to do for now.

  		 */

  		if (!padata)

  			break;

  		cb_cpu = padata->cb_cpu;
  		squeue = per_cpu_ptr(pd->squeue, cb_cpu);

  		spin_lock(&squeue->serial.lock);
  		list_add_tail(&padata->list, &squeue->serial.list);
  		spin_unlock(&squeue->serial.lock);

  		queue_work_on(cb_cpu, pinst->serial_wq, &squeue->work);

  	}
  
  	spin_unlock_bh(&pd->lock);

  	/*
  	 * The next object that needs serialization might have arrived to

  	 * the reorder queues in the meantime.

  	 *

  	 * Ensure reorder queue is read after pd->lock is dropped so we see
  	 * new objects from another task in padata_do_serial.  Pairs with

  	 * smp_mb in padata_do_serial.

  	 */

  	smp_mb();

  	reorder = per_cpu_ptr(pd->reorder_list, pd->cpu);
  	if (!list_empty(&reorder->list) && padata_find_next(pd, false))

  		queue_work(pinst->serial_wq, &pd->reorder_work);

  }

  static void invoke_padata_reorder(struct work_struct *work)
  {

  	struct parallel_data *pd;
  
  	local_bh_disable();

  	pd = container_of(work, struct parallel_data, reorder_work);

  	padata_reorder(pd);
  	local_bh_enable();
  }

  static void padata_serial_worker(struct work_struct *serial_work)

  {

  	struct padata_serial_queue *squeue;

  	struct parallel_data *pd;
  	LIST_HEAD(local_list);

  	int cnt;

  
  	local_bh_disable();

  	squeue = container_of(serial_work, struct padata_serial_queue, work);
  	pd = squeue->pd;

  	spin_lock(&squeue->serial.lock);
  	list_replace_init(&squeue->serial.list, &local_list);
  	spin_unlock(&squeue->serial.lock);

  	cnt = 0;

  	while (!list_empty(&local_list)) {
  		struct padata_priv *padata;
  
  		padata = list_entry(local_list.next,
  				    struct padata_priv, list);
  
  		list_del_init(&padata->list);
  
  		padata->serial(padata);

  		cnt++;

  	}
  	local_bh_enable();

  
  	if (atomic_sub_and_test(cnt, &pd->refcnt))
  		padata_free_pd(pd);

  }

  /**

   * padata_do_serial - padata serialization function
   *
   * @padata: object to be serialized.
   *
   * padata_do_serial must be called for every parallelized object.
   * The serialization callback function will run with BHs off.
   */
  void padata_do_serial(struct padata_priv *padata)
  {

  	struct parallel_data *pd = padata->pd;

  	int hashed_cpu = padata_cpu_hash(pd, padata->seq_nr);

  	struct padata_list *reorder = per_cpu_ptr(pd->reorder_list, hashed_cpu);

  	struct padata_priv *cur;

  	spin_lock(&reorder->lock);

  	/* Sort in ascending order of sequence number. */

  	list_for_each_entry_reverse(cur, &reorder->list, list)

  		if (cur->seq_nr < padata->seq_nr)
  			break;
  	list_add(&padata->list, &cur->list);

  	spin_unlock(&reorder->lock);

  	/*

  	 * Ensure the addition to the reorder list is ordered correctly

  	 * with the trylock of pd->lock in padata_reorder.  Pairs with smp_mb
  	 * in padata_reorder.
  	 */

  	smp_mb();

  	padata_reorder(pd);

  }
  EXPORT_SYMBOL(padata_do_serial);

  static int padata_setup_cpumasks(struct padata_instance *pinst)

  {

  	struct workqueue_attrs *attrs;

  	int err;
  
  	attrs = alloc_workqueue_attrs();
  	if (!attrs)
  		return -ENOMEM;
  
  	/* Restrict parallel_wq workers to pd->cpumask.pcpu. */
  	cpumask_copy(attrs->cpumask, pinst->cpumask.pcpu);
  	err = apply_workqueue_attrs(pinst->parallel_wq, attrs);
  	free_workqueue_attrs(attrs);
  
  	return err;
  }

  static void __init padata_mt_helper(struct work_struct *w)
  {
  	struct padata_work *pw = container_of(w, struct padata_work, pw_work);
  	struct padata_mt_job_state *ps = pw->pw_data;
  	struct padata_mt_job *job = ps->job;
  	bool done;
  
  	spin_lock(&ps->lock);
  
  	while (job->size > 0) {
  		unsigned long start, size, end;
  
  		start = job->start;
  		/* So end is chunk size aligned if enough work remains. */
  		size = roundup(start + 1, ps->chunk_size) - start;
  		size = min(size, job->size);
  		end = start + size;
  
  		job->start = end;
  		job->size -= size;
  
  		spin_unlock(&ps->lock);
  		job->thread_fn(start, end, job->fn_arg);
  		spin_lock(&ps->lock);
  	}
  
  	++ps->nworks_fini;
  	done = (ps->nworks_fini == ps->nworks);
  	spin_unlock(&ps->lock);
  
  	if (done)
  		complete(&ps->completion);
  }
  
  /**
   * padata_do_multithreaded - run a multithreaded job
   * @job: Description of the job.
   *
   * See the definition of struct padata_mt_job for more details.
   */
  void __init padata_do_multithreaded(struct padata_mt_job *job)
  {
  	/* In case threads finish at different times. */
  	static const unsigned long load_balance_factor = 4;
  	struct padata_work my_work, *pw;
  	struct padata_mt_job_state ps;
  	LIST_HEAD(works);
  	int nworks;
  
  	if (job->size == 0)
  		return;
  
  	/* Ensure at least one thread when size < min_chunk. */
  	nworks = max(job->size / job->min_chunk, 1ul);
  	nworks = min(nworks, job->max_threads);
  
  	if (nworks == 1) {
  		/* Single thread, no coordination needed, cut to the chase. */
  		job->thread_fn(job->start, job->start + job->size, job->fn_arg);
  		return;
  	}
  
  	spin_lock_init(&ps.lock);
  	init_completion(&ps.completion);
  	ps.job	       = job;
  	ps.nworks      = padata_work_alloc_mt(nworks, &ps, &works);
  	ps.nworks_fini = 0;
  
  	/*
  	 * Chunk size is the amount of work a helper does per call to the
  	 * thread function.  Load balance large jobs between threads by
  	 * increasing the number of chunks, guarantee at least the minimum
  	 * chunk size from the caller, and honor the caller's alignment.
  	 */
  	ps.chunk_size = job->size / (ps.nworks * load_balance_factor);
  	ps.chunk_size = max(ps.chunk_size, job->min_chunk);
  	ps.chunk_size = roundup(ps.chunk_size, job->align);
  
  	list_for_each_entry(pw, &works, pw_list)
  		queue_work(system_unbound_wq, &pw->pw_work);
  
  	/* Use the current thread, which saves starting a workqueue worker. */
  	padata_work_init(&my_work, padata_mt_helper, &ps, PADATA_WORK_ONSTACK);
  	padata_mt_helper(&my_work.pw_work);
  
  	/* Wait for all the helpers to finish. */
  	wait_for_completion(&ps.completion);
  
  	destroy_work_on_stack(&my_work.pw_work);
  	padata_works_free(&works);
  }

  static void __padata_list_init(struct padata_list *pd_list)
  {
  	INIT_LIST_HEAD(&pd_list->list);
  	spin_lock_init(&pd_list->lock);
  }

  /* Initialize all percpu queues used by serial workers */
  static void padata_init_squeues(struct parallel_data *pd)
  {
  	int cpu;
  	struct padata_serial_queue *squeue;

  	for_each_cpu(cpu, pd->cpumask.cbcpu) {
  		squeue = per_cpu_ptr(pd->squeue, cpu);
  		squeue->pd = pd;
  		__padata_list_init(&squeue->serial);
  		INIT_WORK(&squeue->work, padata_serial_worker);
  	}
  }

  /* Initialize per-CPU reorder lists */
  static void padata_init_reorder_list(struct parallel_data *pd)

  {

  	int cpu;

  	struct padata_list *list;

  	for_each_cpu(cpu, pd->cpumask.pcpu) {

  		list = per_cpu_ptr(pd->reorder_list, cpu);
  		__padata_list_init(list);

  	}

  }

  /* Allocate and initialize the internal cpumask dependend resources. */

  static struct parallel_data *padata_alloc_pd(struct padata_shell *ps)

  {

  	struct padata_instance *pinst = ps->pinst;

  	struct parallel_data *pd;

  	pd = kzalloc(sizeof(struct parallel_data), GFP_KERNEL);
  	if (!pd)
  		goto err;

  	pd->reorder_list = alloc_percpu(struct padata_list);
  	if (!pd->reorder_list)

  		goto err_free_pd;
  
  	pd->squeue = alloc_percpu(struct padata_serial_queue);
  	if (!pd->squeue)

  		goto err_free_reorder_list;

  	pd->ps = ps;

  
  	if (!alloc_cpumask_var(&pd->cpumask.pcpu, GFP_KERNEL))

  		goto err_free_squeue;

  	if (!alloc_cpumask_var(&pd->cpumask.cbcpu, GFP_KERNEL))
  		goto err_free_pcpu;

  	cpumask_and(pd->cpumask.pcpu, pinst->cpumask.pcpu, cpu_online_mask);
  	cpumask_and(pd->cpumask.cbcpu, pinst->cpumask.cbcpu, cpu_online_mask);

  	padata_init_reorder_list(pd);

  	padata_init_squeues(pd);

  	pd->seq_nr = -1;

  	atomic_set(&pd->refcnt, 1);

  	spin_lock_init(&pd->lock);

  	pd->cpu = cpumask_first(pd->cpumask.pcpu);

  	INIT_WORK(&pd->reorder_work, invoke_padata_reorder);

  
  	return pd;

  err_free_pcpu:
  	free_cpumask_var(pd->cpumask.pcpu);

  err_free_squeue:
  	free_percpu(pd->squeue);

  err_free_reorder_list:
  	free_percpu(pd->reorder_list);

  err_free_pd:
  	kfree(pd);
  err:
  	return NULL;
  }
  
  static void padata_free_pd(struct parallel_data *pd)
  {

  	free_cpumask_var(pd->cpumask.pcpu);
  	free_cpumask_var(pd->cpumask.cbcpu);

  	free_percpu(pd->reorder_list);

  	free_percpu(pd->squeue);

  	kfree(pd);
  }

  static void __padata_start(struct padata_instance *pinst)
  {
  	pinst->flags |= PADATA_INIT;
  }

  static void __padata_stop(struct padata_instance *pinst)
  {
  	if (!(pinst->flags & PADATA_INIT))
  		return;
  
  	pinst->flags &= ~PADATA_INIT;
  
  	synchronize_rcu();

  }

  /* Replace the internal control structure with a new one. */

  static int padata_replace_one(struct padata_shell *ps)

  {

  	struct parallel_data *pd_new;

  	pd_new = padata_alloc_pd(ps);
  	if (!pd_new)
  		return -ENOMEM;

  	ps->opd = rcu_dereference_protected(ps->pd, 1);
  	rcu_assign_pointer(ps->pd, pd_new);

  	return 0;
  }

  static int padata_replace(struct padata_instance *pinst)

  {

  	struct padata_shell *ps;

  	int err = 0;

  
  	pinst->flags |= PADATA_RESET;

  	list_for_each_entry(ps, &pinst->pslist, list) {
  		err = padata_replace_one(ps);
  		if (err)
  			break;
  	}
  
  	synchronize_rcu();
  
  	list_for_each_entry_continue_reverse(ps, &pinst->pslist, list)
  		if (atomic_dec_and_test(&ps->opd->refcnt))
  			padata_free_pd(ps->opd);

  
  	pinst->flags &= ~PADATA_RESET;

  
  	return err;

  }

  /* If cpumask contains no active cpu, we mark the instance as invalid. */
  static bool padata_validate_cpumask(struct padata_instance *pinst,
  				    const struct cpumask *cpumask)
  {

  	if (!cpumask_intersects(cpumask, cpu_online_mask)) {

  		pinst->flags |= PADATA_INVALID;
  		return false;
  	}
  
  	pinst->flags &= ~PADATA_INVALID;
  	return true;
  }

  static int __padata_set_cpumasks(struct padata_instance *pinst,
  				 cpumask_var_t pcpumask,
  				 cpumask_var_t cbcpumask)
  {
  	int valid;

  	int err;

  
  	valid = padata_validate_cpumask(pinst, pcpumask);
  	if (!valid) {
  		__padata_stop(pinst);
  		goto out_replace;
  	}
  
  	valid = padata_validate_cpumask(pinst, cbcpumask);
  	if (!valid)
  		__padata_stop(pinst);
  
  out_replace:

  	cpumask_copy(pinst->cpumask.pcpu, pcpumask);
  	cpumask_copy(pinst->cpumask.cbcpu, cbcpumask);

  	err = padata_setup_cpumasks(pinst) ?: padata_replace(pinst);

  
  	if (valid)
  		__padata_start(pinst);

  	return err;

  }
  
  /**

   * padata_set_cpumask - Sets specified by @cpumask_type cpumask to the value
   *                      equivalent to @cpumask.

   * @pinst: padata instance

   * @cpumask_type: PADATA_CPU_SERIAL or PADATA_CPU_PARALLEL corresponding
   *                to parallel and serial cpumasks respectively.

   * @cpumask: the cpumask to use

   *
   * Return: 0 on success or negative error code

   */

  int padata_set_cpumask(struct padata_instance *pinst, int cpumask_type,
  		       cpumask_var_t cpumask)
  {
  	struct cpumask *serial_mask, *parallel_mask;

  	int err = -EINVAL;

  	get_online_cpus();

  	mutex_lock(&pinst->lock);

  	switch (cpumask_type) {
  	case PADATA_CPU_PARALLEL:
  		serial_mask = pinst->cpumask.cbcpu;
  		parallel_mask = cpumask;
  		break;
  	case PADATA_CPU_SERIAL:
  		parallel_mask = pinst->cpumask.pcpu;
  		serial_mask = cpumask;
  		break;
  	default:

  		 goto out;

  	}

  	err =  __padata_set_cpumasks(pinst, parallel_mask, serial_mask);

  
  out:
  	mutex_unlock(&pinst->lock);

  	put_online_cpus();

  
  	return err;
  }
  EXPORT_SYMBOL(padata_set_cpumask);

  #ifdef CONFIG_HOTPLUG_CPU

  static int __padata_add_cpu(struct padata_instance *pinst, int cpu)
  {

  	int err = 0;

  	if (cpumask_test_cpu(cpu, cpu_online_mask)) {

  		err = padata_replace(pinst);

  		if (padata_validate_cpumask(pinst, pinst->cpumask.pcpu) &&
  		    padata_validate_cpumask(pinst, pinst->cpumask.cbcpu))

  			__padata_start(pinst);

  	}

  	return err;

  }

  static int __padata_remove_cpu(struct padata_instance *pinst, int cpu)
  {

  	int err = 0;

  	if (!cpumask_test_cpu(cpu, cpu_online_mask)) {

  		if (!padata_validate_cpumask(pinst, pinst->cpumask.pcpu) ||

  		    !padata_validate_cpumask(pinst, pinst->cpumask.cbcpu))

  			__padata_stop(pinst);

  		err = padata_replace(pinst);

  	}

  	return err;

  }

  static inline int pinst_has_cpu(struct padata_instance *pinst, int cpu)
  {
  	return cpumask_test_cpu(cpu, pinst->cpumask.pcpu) ||
  		cpumask_test_cpu(cpu, pinst->cpumask.cbcpu);
  }

  static int padata_cpu_online(unsigned int cpu, struct hlist_node *node)

  {

  	struct padata_instance *pinst;

  	int ret;

  	pinst = hlist_entry_safe(node, struct padata_instance, cpu_online_node);

  	if (!pinst_has_cpu(pinst, cpu))
  		return 0;

  	mutex_lock(&pinst->lock);
  	ret = __padata_add_cpu(pinst, cpu);
  	mutex_unlock(&pinst->lock);
  	return ret;
  }

  static int padata_cpu_dead(unsigned int cpu, struct hlist_node *node)

  {
  	struct padata_instance *pinst;
  	int ret;

  	pinst = hlist_entry_safe(node, struct padata_instance, cpu_dead_node);

  	if (!pinst_has_cpu(pinst, cpu))
  		return 0;

  	mutex_lock(&pinst->lock);
  	ret = __padata_remove_cpu(pinst, cpu);
  	mutex_unlock(&pinst->lock);
  	return ret;

  }

  
  static enum cpuhp_state hp_online;

  #endif

  static void __padata_free(struct padata_instance *pinst)
  {
  #ifdef CONFIG_HOTPLUG_CPU

  	cpuhp_state_remove_instance_nocalls(CPUHP_PADATA_DEAD,
  					    &pinst->cpu_dead_node);
  	cpuhp_state_remove_instance_nocalls(hp_online, &pinst->cpu_online_node);

  #endif

  	WARN_ON(!list_empty(&pinst->pslist));

  	free_cpumask_var(pinst->cpumask.pcpu);
  	free_cpumask_var(pinst->cpumask.cbcpu);

  	destroy_workqueue(pinst->serial_wq);
  	destroy_workqueue(pinst->parallel_wq);

  	kfree(pinst);
  }
  
  #define kobj2pinst(_kobj)					\
  	container_of(_kobj, struct padata_instance, kobj)
  #define attr2pentry(_attr)					\
  	container_of(_attr, struct padata_sysfs_entry, attr)
  
  static void padata_sysfs_release(struct kobject *kobj)
  {
  	struct padata_instance *pinst = kobj2pinst(kobj);
  	__padata_free(pinst);
  }
  
  struct padata_sysfs_entry {
  	struct attribute attr;
  	ssize_t (*show)(struct padata_instance *, struct attribute *, char *);
  	ssize_t (*store)(struct padata_instance *, struct attribute *,
  			 const char *, size_t);
  };
  
  static ssize_t show_cpumask(struct padata_instance *pinst,
  			    struct attribute *attr,  char *buf)
  {
  	struct cpumask *cpumask;
  	ssize_t len;
  
  	mutex_lock(&pinst->lock);
  	if (!strcmp(attr->name, "serial_cpumask"))
  		cpumask = pinst->cpumask.cbcpu;
  	else
  		cpumask = pinst->cpumask.pcpu;

  	len = snprintf(buf, PAGE_SIZE, "%*pb
  ",
  		       nr_cpu_ids, cpumask_bits(cpumask));

  	mutex_unlock(&pinst->lock);

  	return len < PAGE_SIZE ? len : -EINVAL;

  }
  
  static ssize_t store_cpumask(struct padata_instance *pinst,
  			     struct attribute *attr,
  			     const char *buf, size_t count)
  {
  	cpumask_var_t new_cpumask;
  	ssize_t ret;
  	int mask_type;
  
  	if (!alloc_cpumask_var(&new_cpumask, GFP_KERNEL))
  		return -ENOMEM;
  
  	ret = bitmap_parse(buf, count, cpumask_bits(new_cpumask),
  			   nr_cpumask_bits);
  	if (ret < 0)
  		goto out;
  
  	mask_type = !strcmp(attr->name, "serial_cpumask") ?
  		PADATA_CPU_SERIAL : PADATA_CPU_PARALLEL;
  	ret = padata_set_cpumask(pinst, mask_type, new_cpumask);
  	if (!ret)
  		ret = count;
  
  out:
  	free_cpumask_var(new_cpumask);
  	return ret;
  }
  
  #define PADATA_ATTR_RW(_name, _show_name, _store_name)		\
  	static struct padata_sysfs_entry _name##_attr =		\
  		__ATTR(_name, 0644, _show_name, _store_name)
  #define PADATA_ATTR_RO(_name, _show_name)		\
  	static struct padata_sysfs_entry _name##_attr = \
  		__ATTR(_name, 0400, _show_name, NULL)
  
  PADATA_ATTR_RW(serial_cpumask, show_cpumask, store_cpumask);
  PADATA_ATTR_RW(parallel_cpumask, show_cpumask, store_cpumask);
  
  /*
   * Padata sysfs provides the following objects:
   * serial_cpumask   [RW] - cpumask for serial workers
   * parallel_cpumask [RW] - cpumask for parallel workers
   */
  static struct attribute *padata_default_attrs[] = {
  	&serial_cpumask_attr.attr,
  	&parallel_cpumask_attr.attr,
  	NULL,
  };

  ATTRIBUTE_GROUPS(padata_default);

  
  static ssize_t padata_sysfs_show(struct kobject *kobj,
  				 struct attribute *attr, char *buf)
  {
  	struct padata_instance *pinst;
  	struct padata_sysfs_entry *pentry;
  	ssize_t ret = -EIO;
  
  	pinst = kobj2pinst(kobj);
  	pentry = attr2pentry(attr);
  	if (pentry->show)
  		ret = pentry->show(pinst, attr, buf);
  
  	return ret;
  }
  
  static ssize_t padata_sysfs_store(struct kobject *kobj, struct attribute *attr,
  				  const char *buf, size_t count)
  {
  	struct padata_instance *pinst;
  	struct padata_sysfs_entry *pentry;
  	ssize_t ret = -EIO;
  
  	pinst = kobj2pinst(kobj);
  	pentry = attr2pentry(attr);
  	if (pentry->show)
  		ret = pentry->store(pinst, attr, buf, count);
  
  	return ret;
  }
  
  static const struct sysfs_ops padata_sysfs_ops = {
  	.show = padata_sysfs_show,
  	.store = padata_sysfs_store,
  };
  
  static struct kobj_type padata_attr_type = {
  	.sysfs_ops = &padata_sysfs_ops,

  	.default_groups = padata_default_groups,

  	.release = padata_sysfs_release,
  };

  /**

   * padata_alloc - allocate and initialize a padata instance

   * @name: used to identify the instance

   *
   * Return: new instance on success, NULL on error

   */

  struct padata_instance *padata_alloc(const char *name)

  {

  	struct padata_instance *pinst;

  
  	pinst = kzalloc(sizeof(struct padata_instance), GFP_KERNEL);
  	if (!pinst)
  		goto err;

  	pinst->parallel_wq = alloc_workqueue("%s_parallel", WQ_UNBOUND, 0,
  					     name);

  	if (!pinst->parallel_wq)

  		goto err_free_inst;

  	get_online_cpus();

  	pinst->serial_wq = alloc_workqueue("%s_serial", WQ_MEM_RECLAIM |
  					   WQ_CPU_INTENSIVE, 1, name);
  	if (!pinst->serial_wq)

  		goto err_put_cpus;

  
  	if (!alloc_cpumask_var(&pinst->cpumask.pcpu, GFP_KERNEL))
  		goto err_free_serial_wq;

  	if (!alloc_cpumask_var(&pinst->cpumask.cbcpu, GFP_KERNEL)) {
  		free_cpumask_var(pinst->cpumask.pcpu);

  		goto err_free_serial_wq;

  	}

  	INIT_LIST_HEAD(&pinst->pslist);

  	cpumask_copy(pinst->cpumask.pcpu, cpu_possible_mask);
  	cpumask_copy(pinst->cpumask.cbcpu, cpu_possible_mask);

  
  	if (padata_setup_cpumasks(pinst))

  		goto err_free_masks;

  	__padata_start(pinst);

  	kobject_init(&pinst->kobj, &padata_attr_type);

  	mutex_init(&pinst->lock);

  #ifdef CONFIG_HOTPLUG_CPU

  	cpuhp_state_add_instance_nocalls_cpuslocked(hp_online,
  						    &pinst->cpu_online_node);

  	cpuhp_state_add_instance_nocalls_cpuslocked(CPUHP_PADATA_DEAD,

  						    &pinst->cpu_dead_node);

  #endif

  
  	put_online_cpus();

  	return pinst;

  err_free_masks:
  	free_cpumask_var(pinst->cpumask.pcpu);
  	free_cpumask_var(pinst->cpumask.cbcpu);

  err_free_serial_wq:
  	destroy_workqueue(pinst->serial_wq);

  err_put_cpus:
  	put_online_cpus();

  	destroy_workqueue(pinst->parallel_wq);

  err_free_inst:
  	kfree(pinst);
  err:
  	return NULL;
  }

  EXPORT_SYMBOL(padata_alloc);

  
  /**

   * padata_free - free a padata instance
   *

   * @pinst: padata instance to free

   */
  void padata_free(struct padata_instance *pinst)
  {

  	kobject_put(&pinst->kobj);

  }
  EXPORT_SYMBOL(padata_free);

  /**
   * padata_alloc_shell - Allocate and initialize padata shell.
   *
   * @pinst: Parent padata_instance object.

   *
   * Return: new shell on success, NULL on error

   */
  struct padata_shell *padata_alloc_shell(struct padata_instance *pinst)
  {
  	struct parallel_data *pd;
  	struct padata_shell *ps;
  
  	ps = kzalloc(sizeof(*ps), GFP_KERNEL);
  	if (!ps)
  		goto out;
  
  	ps->pinst = pinst;
  
  	get_online_cpus();
  	pd = padata_alloc_pd(ps);
  	put_online_cpus();
  
  	if (!pd)
  		goto out_free_ps;
  
  	mutex_lock(&pinst->lock);
  	RCU_INIT_POINTER(ps->pd, pd);
  	list_add(&ps->list, &pinst->pslist);
  	mutex_unlock(&pinst->lock);
  
  	return ps;
  
  out_free_ps:
  	kfree(ps);
  out:
  	return NULL;
  }
  EXPORT_SYMBOL(padata_alloc_shell);
  
  /**
   * padata_free_shell - free a padata shell
   *
   * @ps: padata shell to free
   */
  void padata_free_shell(struct padata_shell *ps)
  {

  	if (!ps)
  		return;

  	mutex_lock(&ps->pinst->lock);

  	list_del(&ps->list);
  	padata_free_pd(rcu_dereference_protected(ps->pd, 1));

  	mutex_unlock(&ps->pinst->lock);

  
  	kfree(ps);
  }
  EXPORT_SYMBOL(padata_free_shell);

  void __init padata_init(void)

  {

  	unsigned int i, possible_cpus;

  #ifdef CONFIG_HOTPLUG_CPU

  	int ret;
  
  	ret = cpuhp_setup_state_multi(CPUHP_AP_ONLINE_DYN, "padata:online",

  				      padata_cpu_online, NULL);

  	if (ret < 0)

  		goto err;

  	hp_online = ret;

  
  	ret = cpuhp_setup_state_multi(CPUHP_PADATA_DEAD, "padata:dead",
  				      NULL, padata_cpu_dead);

  	if (ret < 0)
  		goto remove_online_state;
  #endif
  
  	possible_cpus = num_possible_cpus();
  	padata_works = kmalloc_array(possible_cpus, sizeof(struct padata_work),
  				     GFP_KERNEL);
  	if (!padata_works)
  		goto remove_dead_state;
  
  	for (i = 0; i < possible_cpus; ++i)
  		list_add(&padata_works[i].pw_list, &padata_free_works);

  	return;

  
  remove_dead_state:
  #ifdef CONFIG_HOTPLUG_CPU
  	cpuhp_remove_multi_state(CPUHP_PADATA_DEAD);
  remove_online_state:
  	cpuhp_remove_multi_state(hp_online);

  err:

  #endif

  	pr_warn("padata: initialization failed
  ");

  }