io-wq.c 26.4 KB
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// SPDX-License-Identifier: GPL-2.0
/*
 * Basic worker thread pool for io_uring
 *
 * Copyright (C) 2019 Jens Axboe
 *
 */
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/errno.h>
#include <linux/sched/signal.h>
#include <linux/mm.h>
#include <linux/mmu_context.h>
#include <linux/sched/mm.h>
#include <linux/percpu.h>
#include <linux/slab.h>
#include <linux/kthread.h>
#include <linux/rculist_nulls.h>
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#include <linux/uaccess.h>
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#include "io-wq.h"

#define WORKER_IDLE_TIMEOUT	(5 * HZ)

enum {
	IO_WORKER_F_UP		= 1,	/* up and active */
	IO_WORKER_F_RUNNING	= 2,	/* account as running */
	IO_WORKER_F_FREE	= 4,	/* worker on free list */
	IO_WORKER_F_EXITING	= 8,	/* worker exiting */
	IO_WORKER_F_FIXED	= 16,	/* static idle worker */
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	IO_WORKER_F_BOUND	= 32,	/* is doing bounded work */
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};

enum {
	IO_WQ_BIT_EXIT		= 0,	/* wq exiting */
	IO_WQ_BIT_CANCEL	= 1,	/* cancel work on list */
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	IO_WQ_BIT_ERROR		= 2,	/* error on setup */
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};

enum {
	IO_WQE_FLAG_STALLED	= 1,	/* stalled on hash */
};

/*
 * One for each thread in a wqe pool
 */
struct io_worker {
	refcount_t ref;
	unsigned flags;
	struct hlist_nulls_node nulls_node;
	struct task_struct *task;
	wait_queue_head_t wait;
	struct io_wqe *wqe;
	struct io_wq_work *cur_work;

	struct rcu_head rcu;
	struct mm_struct *mm;
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	const struct cred *creds;
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	struct files_struct *restore_files;
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};

struct io_wq_nulls_list {
	struct hlist_nulls_head head;
	unsigned long nulls;
};

#if BITS_PER_LONG == 64
#define IO_WQ_HASH_ORDER	6
#else
#define IO_WQ_HASH_ORDER	5
#endif

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struct io_wqe_acct {
	unsigned nr_workers;
	unsigned max_workers;
	atomic_t nr_running;
};

enum {
	IO_WQ_ACCT_BOUND,
	IO_WQ_ACCT_UNBOUND,
};

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/*
 * Per-node worker thread pool
 */
struct io_wqe {
	struct {
		spinlock_t lock;
		struct list_head work_list;
		unsigned long hash_map;
		unsigned flags;
	} ____cacheline_aligned_in_smp;

	int node;
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	struct io_wqe_acct acct[2];
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	struct io_wq_nulls_list free_list;
	struct io_wq_nulls_list busy_list;

	struct io_wq *wq;
};

/*
 * Per io_wq state
  */
struct io_wq {
	struct io_wqe **wqes;
	unsigned long state;
	unsigned nr_wqes;

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	get_work_fn *get_work;
	put_work_fn *put_work;

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	struct task_struct *manager;
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	struct user_struct *user;
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	const struct cred *creds;
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	struct mm_struct *mm;
	refcount_t refs;
	struct completion done;
};

static bool io_worker_get(struct io_worker *worker)
{
	return refcount_inc_not_zero(&worker->ref);
}

static void io_worker_release(struct io_worker *worker)
{
	if (refcount_dec_and_test(&worker->ref))
		wake_up_process(worker->task);
}

/*
 * Note: drops the wqe->lock if returning true! The caller must re-acquire
 * the lock in that case. Some callers need to restart handling if this
 * happens, so we can't just re-acquire the lock on behalf of the caller.
 */
static bool __io_worker_unuse(struct io_wqe *wqe, struct io_worker *worker)
{
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	bool dropped_lock = false;

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	if (worker->creds) {
		revert_creds(worker->creds);
		worker->creds = NULL;
	}

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	if (current->files != worker->restore_files) {
		__acquire(&wqe->lock);
		spin_unlock_irq(&wqe->lock);
		dropped_lock = true;

		task_lock(current);
		current->files = worker->restore_files;
		task_unlock(current);
	}

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	/*
	 * If we have an active mm, we need to drop the wq lock before unusing
	 * it. If we do, return true and let the caller retry the idle loop.
	 */
	if (worker->mm) {
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		if (!dropped_lock) {
			__acquire(&wqe->lock);
			spin_unlock_irq(&wqe->lock);
			dropped_lock = true;
		}
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		__set_current_state(TASK_RUNNING);
		set_fs(KERNEL_DS);
		unuse_mm(worker->mm);
		mmput(worker->mm);
		worker->mm = NULL;
	}

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	return dropped_lock;
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}

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static inline struct io_wqe_acct *io_work_get_acct(struct io_wqe *wqe,
						   struct io_wq_work *work)
{
	if (work->flags & IO_WQ_WORK_UNBOUND)
		return &wqe->acct[IO_WQ_ACCT_UNBOUND];

	return &wqe->acct[IO_WQ_ACCT_BOUND];
}

static inline struct io_wqe_acct *io_wqe_get_acct(struct io_wqe *wqe,
						  struct io_worker *worker)
{
	if (worker->flags & IO_WORKER_F_BOUND)
		return &wqe->acct[IO_WQ_ACCT_BOUND];

	return &wqe->acct[IO_WQ_ACCT_UNBOUND];
}

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static void io_worker_exit(struct io_worker *worker)
{
	struct io_wqe *wqe = worker->wqe;
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	struct io_wqe_acct *acct = io_wqe_get_acct(wqe, worker);
	unsigned nr_workers;
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	/*
	 * If we're not at zero, someone else is holding a brief reference
	 * to the worker. Wait for that to go away.
	 */
	set_current_state(TASK_INTERRUPTIBLE);
	if (!refcount_dec_and_test(&worker->ref))
		schedule();
	__set_current_state(TASK_RUNNING);

	preempt_disable();
	current->flags &= ~PF_IO_WORKER;
	if (worker->flags & IO_WORKER_F_RUNNING)
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		atomic_dec(&acct->nr_running);
	if (!(worker->flags & IO_WORKER_F_BOUND))
		atomic_dec(&wqe->wq->user->processes);
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	worker->flags = 0;
	preempt_enable();

	spin_lock_irq(&wqe->lock);
	hlist_nulls_del_rcu(&worker->nulls_node);
	if (__io_worker_unuse(wqe, worker)) {
		__release(&wqe->lock);
		spin_lock_irq(&wqe->lock);
	}
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	acct->nr_workers--;
	nr_workers = wqe->acct[IO_WQ_ACCT_BOUND].nr_workers +
			wqe->acct[IO_WQ_ACCT_UNBOUND].nr_workers;
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	spin_unlock_irq(&wqe->lock);

	/* all workers gone, wq exit can proceed */
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	if (!nr_workers && refcount_dec_and_test(&wqe->wq->refs))
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		complete(&wqe->wq->done);

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	kfree_rcu(worker, rcu);
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}

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static inline bool io_wqe_run_queue(struct io_wqe *wqe)
	__must_hold(wqe->lock)
{
	if (!list_empty(&wqe->work_list) && !(wqe->flags & IO_WQE_FLAG_STALLED))
		return true;
	return false;
}

/*
 * Check head of free list for an available worker. If one isn't available,
 * caller must wake up the wq manager to create one.
 */
static bool io_wqe_activate_free_worker(struct io_wqe *wqe)
	__must_hold(RCU)
{
	struct hlist_nulls_node *n;
	struct io_worker *worker;

	n = rcu_dereference(hlist_nulls_first_rcu(&wqe->free_list.head));
	if (is_a_nulls(n))
		return false;

	worker = hlist_nulls_entry(n, struct io_worker, nulls_node);
	if (io_worker_get(worker)) {
		wake_up(&worker->wait);
		io_worker_release(worker);
		return true;
	}

	return false;
}

/*
 * We need a worker. If we find a free one, we're good. If not, and we're
 * below the max number of workers, wake up the manager to create one.
 */
static void io_wqe_wake_worker(struct io_wqe *wqe, struct io_wqe_acct *acct)
{
	bool ret;

	/*
	 * Most likely an attempt to queue unbounded work on an io_wq that
	 * wasn't setup with any unbounded workers.
	 */
	WARN_ON_ONCE(!acct->max_workers);

	rcu_read_lock();
	ret = io_wqe_activate_free_worker(wqe);
	rcu_read_unlock();

	if (!ret && acct->nr_workers < acct->max_workers)
		wake_up_process(wqe->wq->manager);
}

static void io_wqe_inc_running(struct io_wqe *wqe, struct io_worker *worker)
{
	struct io_wqe_acct *acct = io_wqe_get_acct(wqe, worker);

	atomic_inc(&acct->nr_running);
}

static void io_wqe_dec_running(struct io_wqe *wqe, struct io_worker *worker)
	__must_hold(wqe->lock)
{
	struct io_wqe_acct *acct = io_wqe_get_acct(wqe, worker);

	if (atomic_dec_and_test(&acct->nr_running) && io_wqe_run_queue(wqe))
		io_wqe_wake_worker(wqe, acct);
}

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static void io_worker_start(struct io_wqe *wqe, struct io_worker *worker)
{
	allow_kernel_signal(SIGINT);

	current->flags |= PF_IO_WORKER;

	worker->flags |= (IO_WORKER_F_UP | IO_WORKER_F_RUNNING);
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	worker->restore_files = current->files;
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	io_wqe_inc_running(wqe, worker);
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}

/*
 * Worker will start processing some work. Move it to the busy list, if
 * it's currently on the freelist
 */
static void __io_worker_busy(struct io_wqe *wqe, struct io_worker *worker,
			     struct io_wq_work *work)
	__must_hold(wqe->lock)
{
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	bool worker_bound, work_bound;

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	if (worker->flags & IO_WORKER_F_FREE) {
		worker->flags &= ~IO_WORKER_F_FREE;
		hlist_nulls_del_init_rcu(&worker->nulls_node);
		hlist_nulls_add_head_rcu(&worker->nulls_node,
						&wqe->busy_list.head);
	}
	worker->cur_work = work;
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	/*
	 * If worker is moving from bound to unbound (or vice versa), then
	 * ensure we update the running accounting.
	 */
	 worker_bound = (worker->flags & IO_WORKER_F_BOUND) != 0;
	 work_bound = (work->flags & IO_WQ_WORK_UNBOUND) == 0;
	 if (worker_bound != work_bound) {
		io_wqe_dec_running(wqe, worker);
		if (work_bound) {
			worker->flags |= IO_WORKER_F_BOUND;
			wqe->acct[IO_WQ_ACCT_UNBOUND].nr_workers--;
			wqe->acct[IO_WQ_ACCT_BOUND].nr_workers++;
			atomic_dec(&wqe->wq->user->processes);
		} else {
			worker->flags &= ~IO_WORKER_F_BOUND;
			wqe->acct[IO_WQ_ACCT_UNBOUND].nr_workers++;
			wqe->acct[IO_WQ_ACCT_BOUND].nr_workers--;
			atomic_inc(&wqe->wq->user->processes);
		}
		io_wqe_inc_running(wqe, worker);
	 }
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}

/*
 * No work, worker going to sleep. Move to freelist, and unuse mm if we
 * have one attached. Dropping the mm may potentially sleep, so we drop
 * the lock in that case and return success. Since the caller has to
 * retry the loop in that case (we changed task state), we don't regrab
 * the lock if we return success.
 */
static bool __io_worker_idle(struct io_wqe *wqe, struct io_worker *worker)
	__must_hold(wqe->lock)
{
	if (!(worker->flags & IO_WORKER_F_FREE)) {
		worker->flags |= IO_WORKER_F_FREE;
		hlist_nulls_del_init_rcu(&worker->nulls_node);
		hlist_nulls_add_head_rcu(&worker->nulls_node,
						&wqe->free_list.head);
	}

	return __io_worker_unuse(wqe, worker);
}

static struct io_wq_work *io_get_next_work(struct io_wqe *wqe, unsigned *hash)
	__must_hold(wqe->lock)
{
	struct io_wq_work *work;

	list_for_each_entry(work, &wqe->work_list, list) {
		/* not hashed, can run anytime */
		if (!(work->flags & IO_WQ_WORK_HASHED)) {
			list_del(&work->list);
			return work;
		}

		/* hashed, can run if not already running */
		*hash = work->flags >> IO_WQ_HASH_SHIFT;
		if (!(wqe->hash_map & BIT_ULL(*hash))) {
			wqe->hash_map |= BIT_ULL(*hash);
			list_del(&work->list);
			return work;
		}
	}

	return NULL;
}

static void io_worker_handle_work(struct io_worker *worker)
	__releases(wqe->lock)
{
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	struct io_wq_work *work, *old_work = NULL, *put_work = NULL;
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	struct io_wqe *wqe = worker->wqe;
	struct io_wq *wq = wqe->wq;

	do {
		unsigned hash = -1U;

		/*
		 * Signals are either sent to cancel specific work, or to just
		 * cancel all work items. For the former, ->cur_work must
		 * match. ->cur_work is NULL at this point, since we haven't
		 * assigned any work, so it's safe to flush signals for that
		 * case. For the latter case of cancelling all work, the caller
		 * wil have set IO_WQ_BIT_CANCEL.
		 */
		if (signal_pending(current))
			flush_signals(current);

		/*
		 * If we got some work, mark us as busy. If we didn't, but
		 * the list isn't empty, it means we stalled on hashed work.
		 * Mark us stalled so we don't keep looking for work when we
		 * can't make progress, any work completion or insertion will
		 * clear the stalled flag.
		 */
		work = io_get_next_work(wqe, &hash);
		if (work)
			__io_worker_busy(wqe, worker, work);
		else if (!list_empty(&wqe->work_list))
			wqe->flags |= IO_WQE_FLAG_STALLED;

		spin_unlock_irq(&wqe->lock);
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		if (put_work && wq->put_work)
			wq->put_work(old_work);
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		if (!work)
			break;
next:
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		if ((work->flags & IO_WQ_WORK_NEEDS_FILES) &&
		    current->files != work->files) {
			task_lock(current);
			current->files = work->files;
			task_unlock(current);
		}
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		if ((work->flags & IO_WQ_WORK_NEEDS_USER) && !worker->mm &&
		    wq->mm && mmget_not_zero(wq->mm)) {
			use_mm(wq->mm);
			set_fs(USER_DS);
			worker->mm = wq->mm;
		}
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		if (!worker->creds)
			worker->creds = override_creds(wq->creds);
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		if (test_bit(IO_WQ_BIT_CANCEL, &wq->state))
			work->flags |= IO_WQ_WORK_CANCEL;
		if (worker->mm)
			work->flags |= IO_WQ_WORK_HAS_MM;

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		if (wq->get_work && !(work->flags & IO_WQ_WORK_INTERNAL)) {
			put_work = work;
			wq->get_work(work);
		}

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		old_work = work;
		work->func(&work);

		spin_lock_irq(&wqe->lock);
		worker->cur_work = NULL;
		if (hash != -1U) {
			wqe->hash_map &= ~BIT_ULL(hash);
			wqe->flags &= ~IO_WQE_FLAG_STALLED;
		}
		if (work && work != old_work) {
			spin_unlock_irq(&wqe->lock);
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			if (put_work && wq->put_work) {
				wq->put_work(put_work);
				put_work = NULL;
			}

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			/* dependent work not hashed */
			hash = -1U;
			goto next;
		}
	} while (1);
}

static int io_wqe_worker(void *data)
{
	struct io_worker *worker = data;
	struct io_wqe *wqe = worker->wqe;
	struct io_wq *wq = wqe->wq;
	DEFINE_WAIT(wait);

	io_worker_start(wqe, worker);

	while (!test_bit(IO_WQ_BIT_EXIT, &wq->state)) {
		prepare_to_wait(&worker->wait, &wait, TASK_INTERRUPTIBLE);

		spin_lock_irq(&wqe->lock);
		if (io_wqe_run_queue(wqe)) {
			__set_current_state(TASK_RUNNING);
			io_worker_handle_work(worker);
			continue;
		}
		/* drops the lock on success, retry */
		if (__io_worker_idle(wqe, worker)) {
			__release(&wqe->lock);
			continue;
		}
		spin_unlock_irq(&wqe->lock);
		if (signal_pending(current))
			flush_signals(current);
		if (schedule_timeout(WORKER_IDLE_TIMEOUT))
			continue;
		/* timed out, exit unless we're the fixed worker */
		if (test_bit(IO_WQ_BIT_EXIT, &wq->state) ||
		    !(worker->flags & IO_WORKER_F_FIXED))
			break;
	}

	finish_wait(&worker->wait, &wait);

	if (test_bit(IO_WQ_BIT_EXIT, &wq->state)) {
		spin_lock_irq(&wqe->lock);
		if (!list_empty(&wqe->work_list))
			io_worker_handle_work(worker);
		else
			spin_unlock_irq(&wqe->lock);
	}

	io_worker_exit(worker);
	return 0;
}

/*
 * Called when a worker is scheduled in. Mark us as currently running.
 */
void io_wq_worker_running(struct task_struct *tsk)
{
	struct io_worker *worker = kthread_data(tsk);
	struct io_wqe *wqe = worker->wqe;

	if (!(worker->flags & IO_WORKER_F_UP))
		return;
	if (worker->flags & IO_WORKER_F_RUNNING)
		return;
	worker->flags |= IO_WORKER_F_RUNNING;
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	io_wqe_inc_running(wqe, worker);
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}

/*
 * Called when worker is going to sleep. If there are no workers currently
 * running and we have work pending, wake up a free one or have the manager
 * set one up.
 */
void io_wq_worker_sleeping(struct task_struct *tsk)
{
	struct io_worker *worker = kthread_data(tsk);
	struct io_wqe *wqe = worker->wqe;

	if (!(worker->flags & IO_WORKER_F_UP))
		return;
	if (!(worker->flags & IO_WORKER_F_RUNNING))
		return;

	worker->flags &= ~IO_WORKER_F_RUNNING;

	spin_lock_irq(&wqe->lock);
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	io_wqe_dec_running(wqe, worker);
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	spin_unlock_irq(&wqe->lock);
}

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static bool create_io_worker(struct io_wq *wq, struct io_wqe *wqe, int index)
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{
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	struct io_wqe_acct *acct =&wqe->acct[index];
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	struct io_worker *worker;

	worker = kcalloc_node(1, sizeof(*worker), GFP_KERNEL, wqe->node);
	if (!worker)
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		return false;
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	refcount_set(&worker->ref, 1);
	worker->nulls_node.pprev = NULL;
	init_waitqueue_head(&worker->wait);
	worker->wqe = wqe;

	worker->task = kthread_create_on_node(io_wqe_worker, worker, wqe->node,
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				"io_wqe_worker-%d/%d", index, wqe->node);
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	if (IS_ERR(worker->task)) {
		kfree(worker);
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		return false;
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	}

	spin_lock_irq(&wqe->lock);
	hlist_nulls_add_head_rcu(&worker->nulls_node, &wqe->free_list.head);
	worker->flags |= IO_WORKER_F_FREE;
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	if (index == IO_WQ_ACCT_BOUND)
		worker->flags |= IO_WORKER_F_BOUND;
	if (!acct->nr_workers && (worker->flags & IO_WORKER_F_BOUND))
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		worker->flags |= IO_WORKER_F_FIXED;
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	acct->nr_workers++;
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	spin_unlock_irq(&wqe->lock);

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	if (index == IO_WQ_ACCT_UNBOUND)
		atomic_inc(&wq->user->processes);

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	wake_up_process(worker->task);
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	return true;
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}

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static inline bool io_wqe_need_worker(struct io_wqe *wqe, int index)
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	__must_hold(wqe->lock)
{
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	struct io_wqe_acct *acct = &wqe->acct[index];
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	/* if we have available workers or no work, no need */
	if (!hlist_nulls_empty(&wqe->free_list.head) || !io_wqe_run_queue(wqe))
		return false;
	return acct->nr_workers < acct->max_workers;
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}

/*
 * Manager thread. Tasked with creating new workers, if we need them.
 */
static int io_wq_manager(void *data)
{
	struct io_wq *wq = data;
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	int i;
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	/* create fixed workers */
	refcount_set(&wq->refs, wq->nr_wqes);
	for (i = 0; i < wq->nr_wqes; i++) {
		if (create_io_worker(wq, wq->wqes[i], IO_WQ_ACCT_BOUND))
			continue;
		goto err;
	}
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	complete(&wq->done);

	while (!kthread_should_stop()) {
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		for (i = 0; i < wq->nr_wqes; i++) {
			struct io_wqe *wqe = wq->wqes[i];
648
			bool fork_worker[2] = { false, false };
649 650

			spin_lock_irq(&wqe->lock);
651 652 653 654
			if (io_wqe_need_worker(wqe, IO_WQ_ACCT_BOUND))
				fork_worker[IO_WQ_ACCT_BOUND] = true;
			if (io_wqe_need_worker(wqe, IO_WQ_ACCT_UNBOUND))
				fork_worker[IO_WQ_ACCT_UNBOUND] = true;
655
			spin_unlock_irq(&wqe->lock);
656 657 658 659
			if (fork_worker[IO_WQ_ACCT_BOUND])
				create_io_worker(wq, wqe, IO_WQ_ACCT_BOUND);
			if (fork_worker[IO_WQ_ACCT_UNBOUND])
				create_io_worker(wq, wqe, IO_WQ_ACCT_UNBOUND);
660 661 662 663 664 665
		}
		set_current_state(TASK_INTERRUPTIBLE);
		schedule_timeout(HZ);
	}

	return 0;
666 667 668 669 670 671
err:
	set_bit(IO_WQ_BIT_ERROR, &wq->state);
	set_bit(IO_WQ_BIT_EXIT, &wq->state);
	if (refcount_sub_and_test(wq->nr_wqes - i, &wq->refs))
		complete(&wq->done);
	return 0;
672 673
}

674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696
static bool io_wq_can_queue(struct io_wqe *wqe, struct io_wqe_acct *acct,
			    struct io_wq_work *work)
{
	bool free_worker;

	if (!(work->flags & IO_WQ_WORK_UNBOUND))
		return true;
	if (atomic_read(&acct->nr_running))
		return true;

	rcu_read_lock();
	free_worker = !hlist_nulls_empty(&wqe->free_list.head);
	rcu_read_unlock();
	if (free_worker)
		return true;

	if (atomic_read(&wqe->wq->user->processes) >= acct->max_workers &&
	    !(capable(CAP_SYS_RESOURCE) || capable(CAP_SYS_ADMIN)))
		return false;

	return true;
}

697 698
static void io_wqe_enqueue(struct io_wqe *wqe, struct io_wq_work *work)
{
699
	struct io_wqe_acct *acct = io_work_get_acct(wqe, work);
700 701
	unsigned long flags;

702 703 704 705 706 707 708 709 710 711 712 713
	/*
	 * Do early check to see if we need a new unbound worker, and if we do,
	 * if we're allowed to do so. This isn't 100% accurate as there's a
	 * gap between this check and incrementing the value, but that's OK.
	 * It's close enough to not be an issue, fork() has the same delay.
	 */
	if (unlikely(!io_wq_can_queue(wqe, acct, work))) {
		work->flags |= IO_WQ_WORK_CANCEL;
		work->func(&work);
		return;
	}

714 715 716 717 718
	spin_lock_irqsave(&wqe->lock, flags);
	list_add_tail(&work->list, &wqe->work_list);
	wqe->flags &= ~IO_WQE_FLAG_STALLED;
	spin_unlock_irqrestore(&wqe->lock, flags);

719 720
	if (!atomic_read(&acct->nr_running))
		io_wqe_wake_worker(wqe, acct);
721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800
}

void io_wq_enqueue(struct io_wq *wq, struct io_wq_work *work)
{
	struct io_wqe *wqe = wq->wqes[numa_node_id()];

	io_wqe_enqueue(wqe, work);
}

/*
 * Enqueue work, hashed by some key. Work items that hash to the same value
 * will not be done in parallel. Used to limit concurrent writes, generally
 * hashed by inode.
 */
void io_wq_enqueue_hashed(struct io_wq *wq, struct io_wq_work *work, void *val)
{
	struct io_wqe *wqe = wq->wqes[numa_node_id()];
	unsigned bit;


	bit = hash_ptr(val, IO_WQ_HASH_ORDER);
	work->flags |= (IO_WQ_WORK_HASHED | (bit << IO_WQ_HASH_SHIFT));
	io_wqe_enqueue(wqe, work);
}

static bool io_wqe_worker_send_sig(struct io_worker *worker, void *data)
{
	send_sig(SIGINT, worker->task, 1);
	return false;
}

/*
 * Iterate the passed in list and call the specific function for each
 * worker that isn't exiting
 */
static bool io_wq_for_each_worker(struct io_wqe *wqe,
				  struct io_wq_nulls_list *list,
				  bool (*func)(struct io_worker *, void *),
				  void *data)
{
	struct hlist_nulls_node *n;
	struct io_worker *worker;
	bool ret = false;

restart:
	hlist_nulls_for_each_entry_rcu(worker, n, &list->head, nulls_node) {
		if (io_worker_get(worker)) {
			ret = func(worker, data);
			io_worker_release(worker);
			if (ret)
				break;
		}
	}
	if (!ret && get_nulls_value(n) != list->nulls)
		goto restart;
	return ret;
}

void io_wq_cancel_all(struct io_wq *wq)
{
	int i;

	set_bit(IO_WQ_BIT_CANCEL, &wq->state);

	/*
	 * Browse both lists, as there's a gap between handing work off
	 * to a worker and the worker putting itself on the busy_list
	 */
	rcu_read_lock();
	for (i = 0; i < wq->nr_wqes; i++) {
		struct io_wqe *wqe = wq->wqes[i];

		io_wq_for_each_worker(wqe, &wqe->busy_list,
					io_wqe_worker_send_sig, NULL);
		io_wq_for_each_worker(wqe, &wqe->free_list,
					io_wqe_worker_send_sig, NULL);
	}
	rcu_read_unlock();
}

801 802 803 804 805 806 807 808 809 810
struct io_cb_cancel_data {
	struct io_wqe *wqe;
	work_cancel_fn *cancel;
	void *caller_data;
};

static bool io_work_cancel(struct io_worker *worker, void *cancel_data)
{
	struct io_cb_cancel_data *data = cancel_data;
	struct io_wqe *wqe = data->wqe;
811
	unsigned long flags;
812 813 814 815 816 817
	bool ret = false;

	/*
	 * Hold the lock to avoid ->cur_work going out of scope, caller
	 * may deference the passed in work.
	 */
818
	spin_lock_irqsave(&wqe->lock, flags);
819 820 821 822 823
	if (worker->cur_work &&
	    data->cancel(worker->cur_work, data->caller_data)) {
		send_sig(SIGINT, worker->task, 1);
		ret = true;
	}
824
	spin_unlock_irqrestore(&wqe->lock, flags);
825 826 827 828 829 830 831 832 833 834 835 836 837 838

	return ret;
}

static enum io_wq_cancel io_wqe_cancel_cb_work(struct io_wqe *wqe,
					       work_cancel_fn *cancel,
					       void *cancel_data)
{
	struct io_cb_cancel_data data = {
		.wqe = wqe,
		.cancel = cancel,
		.caller_data = cancel_data,
	};
	struct io_wq_work *work;
839
	unsigned long flags;
840 841
	bool found = false;

842
	spin_lock_irqsave(&wqe->lock, flags);
843 844 845 846 847 848 849
	list_for_each_entry(work, &wqe->work_list, list) {
		if (cancel(work, cancel_data)) {
			list_del(&work->list);
			found = true;
			break;
		}
	}
850
	spin_unlock_irqrestore(&wqe->lock, flags);
851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887

	if (found) {
		work->flags |= IO_WQ_WORK_CANCEL;
		work->func(&work);
		return IO_WQ_CANCEL_OK;
	}

	rcu_read_lock();
	found = io_wq_for_each_worker(wqe, &wqe->free_list, io_work_cancel,
					&data);
	if (found)
		goto done;

	found = io_wq_for_each_worker(wqe, &wqe->busy_list, io_work_cancel,
					&data);
done:
	rcu_read_unlock();
	return found ? IO_WQ_CANCEL_RUNNING : IO_WQ_CANCEL_NOTFOUND;
}

enum io_wq_cancel io_wq_cancel_cb(struct io_wq *wq, work_cancel_fn *cancel,
				  void *data)
{
	enum io_wq_cancel ret = IO_WQ_CANCEL_NOTFOUND;
	int i;

	for (i = 0; i < wq->nr_wqes; i++) {
		struct io_wqe *wqe = wq->wqes[i];

		ret = io_wqe_cancel_cb_work(wqe, cancel, data);
		if (ret != IO_WQ_CANCEL_NOTFOUND)
			break;
	}

	return ret;
}

888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903
static bool io_wq_worker_cancel(struct io_worker *worker, void *data)
{
	struct io_wq_work *work = data;

	if (worker->cur_work == work) {
		send_sig(SIGINT, worker->task, 1);
		return true;
	}

	return false;
}

static enum io_wq_cancel io_wqe_cancel_work(struct io_wqe *wqe,
					    struct io_wq_work *cwork)
{
	struct io_wq_work *work;
904
	unsigned long flags;
905 906 907 908 909 910 911 912 913
	bool found = false;

	cwork->flags |= IO_WQ_WORK_CANCEL;

	/*
	 * First check pending list, if we're lucky we can just remove it
	 * from there. CANCEL_OK means that the work is returned as-new,
	 * no completion will be posted for it.
	 */
914
	spin_lock_irqsave(&wqe->lock, flags);
915 916 917 918 919 920 921
	list_for_each_entry(work, &wqe->work_list, list) {
		if (work == cwork) {
			list_del(&work->list);
			found = true;
			break;
		}
	}
922
	spin_unlock_irqrestore(&wqe->lock, flags);
923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992

	if (found) {
		work->flags |= IO_WQ_WORK_CANCEL;
		work->func(&work);
		return IO_WQ_CANCEL_OK;
	}

	/*
	 * Now check if a free (going busy) or busy worker has the work
	 * currently running. If we find it there, we'll return CANCEL_RUNNING
	 * as an indication that we attempte to signal cancellation. The
	 * completion will run normally in this case.
	 */
	rcu_read_lock();
	found = io_wq_for_each_worker(wqe, &wqe->free_list, io_wq_worker_cancel,
					cwork);
	if (found)
		goto done;

	found = io_wq_for_each_worker(wqe, &wqe->busy_list, io_wq_worker_cancel,
					cwork);
done:
	rcu_read_unlock();
	return found ? IO_WQ_CANCEL_RUNNING : IO_WQ_CANCEL_NOTFOUND;
}

enum io_wq_cancel io_wq_cancel_work(struct io_wq *wq, struct io_wq_work *cwork)
{
	enum io_wq_cancel ret = IO_WQ_CANCEL_NOTFOUND;
	int i;

	for (i = 0; i < wq->nr_wqes; i++) {
		struct io_wqe *wqe = wq->wqes[i];

		ret = io_wqe_cancel_work(wqe, cwork);
		if (ret != IO_WQ_CANCEL_NOTFOUND)
			break;
	}

	return ret;
}

struct io_wq_flush_data {
	struct io_wq_work work;
	struct completion done;
};

static void io_wq_flush_func(struct io_wq_work **workptr)
{
	struct io_wq_work *work = *workptr;
	struct io_wq_flush_data *data;

	data = container_of(work, struct io_wq_flush_data, work);
	complete(&data->done);
}

/*
 * Doesn't wait for previously queued work to finish. When this completes,
 * it just means that previously queued work was started.
 */
void io_wq_flush(struct io_wq *wq)
{
	struct io_wq_flush_data data;
	int i;

	for (i = 0; i < wq->nr_wqes; i++) {
		struct io_wqe *wqe = wq->wqes[i];

		init_completion(&data.done);
		INIT_IO_WORK(&data.work, io_wq_flush_func);
993
		data.work.flags |= IO_WQ_WORK_INTERNAL;
994 995 996 997 998
		io_wqe_enqueue(wqe, &data.work);
		wait_for_completion(&data.done);
	}
}

999
struct io_wq *io_wq_create(unsigned bounded, struct io_wq_data *data)
1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014
{
	int ret = -ENOMEM, i, node;
	struct io_wq *wq;

	wq = kcalloc(1, sizeof(*wq), GFP_KERNEL);
	if (!wq)
		return ERR_PTR(-ENOMEM);

	wq->nr_wqes = num_online_nodes();
	wq->wqes = kcalloc(wq->nr_wqes, sizeof(struct io_wqe *), GFP_KERNEL);
	if (!wq->wqes) {
		kfree(wq);
		return ERR_PTR(-ENOMEM);
	}

1015 1016
	wq->get_work = data->get_work;
	wq->put_work = data->put_work;
1017

1018
	/* caller must already hold a reference to this */
1019
	wq->user = data->user;
1020
	wq->creds = data->creds;
1021

1022 1023 1024 1025 1026 1027 1028 1029 1030
	i = 0;
	for_each_online_node(node) {
		struct io_wqe *wqe;

		wqe = kcalloc_node(1, sizeof(struct io_wqe), GFP_KERNEL, node);
		if (!wqe)
			break;
		wq->wqes[i] = wqe;
		wqe->node = node;
1031 1032
		wqe->acct[IO_WQ_ACCT_BOUND].max_workers = bounded;
		atomic_set(&wqe->acct[IO_WQ_ACCT_BOUND].nr_running, 0);
1033
		if (wq->user) {
1034 1035 1036 1037
			wqe->acct[IO_WQ_ACCT_UNBOUND].max_workers =
					task_rlimit(current, RLIMIT_NPROC);
		}
		atomic_set(&wqe->acct[IO_WQ_ACCT_UNBOUND].nr_running, 0);
1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055
		wqe->node = node;
		wqe->wq = wq;
		spin_lock_init(&wqe->lock);
		INIT_LIST_HEAD(&wqe->work_list);
		INIT_HLIST_NULLS_HEAD(&wqe->free_list.head, 0);
		wqe->free_list.nulls = 0;
		INIT_HLIST_NULLS_HEAD(&wqe->busy_list.head, 1);
		wqe->busy_list.nulls = 1;

		i++;
	}

	init_completion(&wq->done);

	if (i != wq->nr_wqes)
		goto err;

	/* caller must have already done mmgrab() on this mm */
1056
	wq->mm = data->mm;
1057 1058 1059 1060

	wq->manager = kthread_create(io_wq_manager, wq, "io_wq_manager");
	if (!IS_ERR(wq->manager)) {
		wake_up_process(wq->manager);
1061 1062 1063 1064 1065 1066
		wait_for_completion(&wq->done);
		if (test_bit(IO_WQ_BIT_ERROR, &wq->state)) {
			ret = -ENOMEM;
			goto err;
		}
		reinit_completion(&wq->done);
1067 1068 1069 1070 1071
		return wq;
	}

	ret = PTR_ERR(wq->manager);
	complete(&wq->done);
1072 1073 1074 1075 1076
err:
	for (i = 0; i < wq->nr_wqes; i++)
		kfree(wq->wqes[i]);
	kfree(wq->wqes);
	kfree(wq);
1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089
	return ERR_PTR(ret);
}

static bool io_wq_worker_wake(struct io_worker *worker, void *data)
{
	wake_up_process(worker->task);
	return false;
}

void io_wq_destroy(struct io_wq *wq)
{
	int i;

1090 1091
	set_bit(IO_WQ_BIT_EXIT, &wq->state);
	if (wq->manager)
1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113
		kthread_stop(wq->manager);

	rcu_read_lock();
	for (i = 0; i < wq->nr_wqes; i++) {
		struct io_wqe *wqe = wq->wqes[i];

		if (!wqe)
			continue;
		io_wq_for_each_worker(wqe, &wqe->free_list, io_wq_worker_wake,
						NULL);
		io_wq_for_each_worker(wqe, &wqe->busy_list, io_wq_worker_wake,
						NULL);
	}
	rcu_read_unlock();

	wait_for_completion(&wq->done);

	for (i = 0; i < wq->nr_wqes; i++)
		kfree(wq->wqes[i]);
	kfree(wq->wqes);
	kfree(wq);
}