io-wq.c
// 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>
#include <linux/fs_struct.h>
#include <linux/task_work.h>
#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 */
IO_WORKER_F_BOUND = 32, /* is doing bounded work */
};
enum {
IO_WQ_BIT_EXIT = 0, /* wq exiting */
IO_WQ_BIT_CANCEL = 1, /* cancel work on list */
IO_WQ_BIT_ERROR = 2, /* error on setup */
};
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 list_head all_list;
struct task_struct *task;
struct io_wqe *wqe;
struct io_wq_work *cur_work;
spinlock_t lock;
struct rcu_head rcu;
struct mm_struct *mm;
const struct cred *cur_creds;
const struct cred *saved_creds;
struct files_struct *restore_files;
struct fs_struct *restore_fs;
};
#if BITS_PER_LONG == 64
#define IO_WQ_HASH_ORDER 6
#else
#define IO_WQ_HASH_ORDER 5
#endif
#define IO_WQ_NR_HASH_BUCKETS (1u << IO_WQ_HASH_ORDER)
struct io_wqe_acct {
unsigned nr_workers;
unsigned max_workers;
atomic_t nr_running;
};
enum {
IO_WQ_ACCT_BOUND,
IO_WQ_ACCT_UNBOUND,
};
/*
* Per-node worker thread pool
*/
struct io_wqe {
struct {
spinlock_t lock;
struct io_wq_work_list work_list;
unsigned long hash_map;
unsigned flags;
} ____cacheline_aligned_in_smp;
int node;
struct io_wqe_acct acct[2];
struct hlist_nulls_head free_list;
struct list_head all_list;
struct io_wq *wq;
struct io_wq_work *hash_tail[IO_WQ_NR_HASH_BUCKETS];
};
/*
* Per io_wq state
*/
struct io_wq {
struct io_wqe **wqes;
unsigned long state;
free_work_fn *free_work;
struct task_struct *manager;
struct user_struct *user;
refcount_t refs;
struct completion done;
refcount_t use_refs;
};
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)
{
bool dropped_lock = false;
if (worker->saved_creds) {
revert_creds(worker->saved_creds);
worker->cur_creds = worker->saved_creds = NULL;
}
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);
}
if (current->fs != worker->restore_fs)
current->fs = worker->restore_fs;
/*
* 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) {
if (!dropped_lock) {
__acquire(&wqe->lock);
spin_unlock_irq(&wqe->lock);
dropped_lock = true;
}
__set_current_state(TASK_RUNNING);
set_fs(KERNEL_DS);
unuse_mm(worker->mm);
mmput(worker->mm);
worker->mm = NULL;
}
return dropped_lock;
}
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];
}
static void io_worker_exit(struct io_worker *worker)
{
struct io_wqe *wqe = worker->wqe;
struct io_wqe_acct *acct = io_wqe_get_acct(wqe, worker);
unsigned nr_workers;
/*
* 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)
atomic_dec(&acct->nr_running);
if (!(worker->flags & IO_WORKER_F_BOUND))
atomic_dec(&wqe->wq->user->processes);
worker->flags = 0;
preempt_enable();
spin_lock_irq(&wqe->lock);
hlist_nulls_del_rcu(&worker->nulls_node);
list_del_rcu(&worker->all_list);
if (__io_worker_unuse(wqe, worker)) {
__release(&wqe->lock);
spin_lock_irq(&wqe->lock);
}
acct->nr_workers--;
nr_workers = wqe->acct[IO_WQ_ACCT_BOUND].nr_workers +
wqe->acct[IO_WQ_ACCT_UNBOUND].nr_workers;
spin_unlock_irq(&wqe->lock);
/* all workers gone, wq exit can proceed */
if (!nr_workers && refcount_dec_and_test(&wqe->wq->refs))
complete(&wqe->wq->done);
kfree_rcu(worker, rcu);
}
static inline bool io_wqe_run_queue(struct io_wqe *wqe)
__must_hold(wqe->lock)
{
if (!wq_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));
if (is_a_nulls(n))
return false;
worker = hlist_nulls_entry(n, struct io_worker, nulls_node);
if (io_worker_get(worker)) {
wake_up_process(worker->task);
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);
}
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);
worker->restore_files = current->files;
worker->restore_fs = current->fs;
io_wqe_inc_running(wqe, worker);
}
/*
* 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)
{
bool worker_bound, work_bound;
if (worker->flags & IO_WORKER_F_FREE) {
worker->flags &= ~IO_WORKER_F_FREE;
hlist_nulls_del_init_rcu(&worker->nulls_node);
}
/*
* 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);
}
}
/*
* 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_add_head_rcu(&worker->nulls_node, &wqe->free_list);
}
return __io_worker_unuse(wqe, worker);
}
static inline unsigned int io_get_work_hash(struct io_wq_work *work)
{
return work->flags >> IO_WQ_HASH_SHIFT;
}
static struct io_wq_work *io_get_next_work(struct io_wqe *wqe)
__must_hold(wqe->lock)
{
struct io_wq_work_node *node, *prev;
struct io_wq_work *work, *tail;
unsigned int hash;
wq_list_for_each(node, prev, &wqe->work_list) {
work = container_of(node, struct io_wq_work, list);
/* not hashed, can run anytime */
if (!io_wq_is_hashed(work)) {
wq_list_del(&wqe->work_list, node, prev);
return work;
}
/* hashed, can run if not already running */
hash = io_get_work_hash(work);
if (!(wqe->hash_map & BIT(hash))) {
wqe->hash_map |= BIT(hash);
/* all items with this hash lie in [work, tail] */
tail = wqe->hash_tail[hash];
wqe->hash_tail[hash] = NULL;
wq_list_cut(&wqe->work_list, &tail->list, prev);
return work;
}
}
return NULL;
}
static void io_wq_switch_mm(struct io_worker *worker, struct io_wq_work *work)
{
if (worker->mm) {
unuse_mm(worker->mm);
mmput(worker->mm);
worker->mm = NULL;
}
if (!work->mm) {
set_fs(KERNEL_DS);
return;
}
if (mmget_not_zero(work->mm)) {
use_mm(work->mm);
if (!worker->mm)
set_fs(USER_DS);
worker->mm = work->mm;
/* hang on to this mm */
work->mm = NULL;
return;
}
/* failed grabbing mm, ensure work gets cancelled */
work->flags |= IO_WQ_WORK_CANCEL;
}
static void io_wq_switch_creds(struct io_worker *worker,
struct io_wq_work *work)
{
const struct cred *old_creds = override_creds(work->creds);
worker->cur_creds = work->creds;
if (worker->saved_creds)
put_cred(old_creds); /* creds set by previous switch */
else
worker->saved_creds = old_creds;
}
static void io_impersonate_work(struct io_worker *worker,
struct io_wq_work *work)
{
if (work->files && current->files != work->files) {
task_lock(current);
current->files = work->files;
task_unlock(current);
}
if (work->fs && current->fs != work->fs)
current->fs = work->fs;
if (work->mm != worker->mm)
io_wq_switch_mm(worker, work);
if (worker->cur_creds != work->creds)
io_wq_switch_creds(worker, work);
}
static void io_assign_current_work(struct io_worker *worker,
struct io_wq_work *work)
{
if (work) {
/* flush pending signals before assigning new work */
if (signal_pending(current))
flush_signals(current);
cond_resched();
}
spin_lock_irq(&worker->lock);
worker->cur_work = work;
spin_unlock_irq(&worker->lock);
}
static void io_wqe_enqueue(struct io_wqe *wqe, struct io_wq_work *work);
static void io_worker_handle_work(struct io_worker *worker)
__releases(wqe->lock)
{
struct io_wqe *wqe = worker->wqe;
struct io_wq *wq = wqe->wq;
do {
struct io_wq_work *work;
unsigned int hash;
get_next:
/*
* 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);
if (work)
__io_worker_busy(wqe, worker, work);
else if (!wq_list_empty(&wqe->work_list))
wqe->flags |= IO_WQE_FLAG_STALLED;
spin_unlock_irq(&wqe->lock);
if (!work)
break;
io_assign_current_work(worker, work);
/* handle a whole dependent link */
do {
struct io_wq_work *old_work, *next_hashed, *linked;
next_hashed = wq_next_work(work);
io_impersonate_work(worker, work);
/*
* OK to set IO_WQ_WORK_CANCEL even for uncancellable
* work, the worker function will do the right thing.
*/
if (test_bit(IO_WQ_BIT_CANCEL, &wq->state))
work->flags |= IO_WQ_WORK_CANCEL;
hash = io_get_work_hash(work);
linked = old_work = work;
linked->func(&linked);
linked = (old_work == linked) ? NULL : linked;
work = next_hashed;
if (!work && linked && !io_wq_is_hashed(linked)) {
work = linked;
linked = NULL;
}
io_assign_current_work(worker, work);
wq->free_work(old_work);
if (linked)
io_wqe_enqueue(wqe, linked);
if (hash != -1U && !next_hashed) {
spin_lock_irq(&wqe->lock);
wqe->hash_map &= ~BIT_ULL(hash);
wqe->flags &= ~IO_WQE_FLAG_STALLED;
/* dependent work is not hashed */
hash = -1U;
/* skip unnecessary unlock-lock wqe->lock */
if (!work)
goto get_next;
spin_unlock_irq(&wqe->lock);
}
} while (work);
spin_lock_irq(&wqe->lock);
} 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;
io_worker_start(wqe, worker);
while (!test_bit(IO_WQ_BIT_EXIT, &wq->state)) {
set_current_state(TASK_INTERRUPTIBLE);
loop:
spin_lock_irq(&wqe->lock);
if (io_wqe_run_queue(wqe)) {
__set_current_state(TASK_RUNNING);
io_worker_handle_work(worker);
goto loop;
}
/* drops the lock on success, retry */
if (__io_worker_idle(wqe, worker)) {
__release(&wqe->lock);
goto loop;
}
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;
}
if (test_bit(IO_WQ_BIT_EXIT, &wq->state)) {
spin_lock_irq(&wqe->lock);
if (!wq_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;
io_wqe_inc_running(wqe, worker);
}
/*
* 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);
io_wqe_dec_running(wqe, worker);
spin_unlock_irq(&wqe->lock);
}
static bool create_io_worker(struct io_wq *wq, struct io_wqe *wqe, int index)
{
struct io_wqe_acct *acct =&wqe->acct[index];
struct io_worker *worker;
worker = kzalloc_node(sizeof(*worker), GFP_KERNEL, wqe->node);
if (!worker)
return false;
refcount_set(&worker->ref, 1);
worker->nulls_node.pprev = NULL;
worker->wqe = wqe;
spin_lock_init(&worker->lock);
worker->task = kthread_create_on_node(io_wqe_worker, worker, wqe->node,
"io_wqe_worker-%d/%d", index, wqe->node);
if (IS_ERR(worker->task)) {
kfree(worker);
return false;
}
spin_lock_irq(&wqe->lock);
hlist_nulls_add_head_rcu(&worker->nulls_node, &wqe->free_list);
list_add_tail_rcu(&worker->all_list, &wqe->all_list);
worker->flags |= IO_WORKER_F_FREE;
if (index == IO_WQ_ACCT_BOUND)
worker->flags |= IO_WORKER_F_BOUND;
if (!acct->nr_workers && (worker->flags & IO_WORKER_F_BOUND))
worker->flags |= IO_WORKER_F_FIXED;
acct->nr_workers++;
spin_unlock_irq(&wqe->lock);
if (index == IO_WQ_ACCT_UNBOUND)
atomic_inc(&wq->user->processes);
wake_up_process(worker->task);
return true;
}
static inline bool io_wqe_need_worker(struct io_wqe *wqe, int index)
__must_hold(wqe->lock)
{
struct io_wqe_acct *acct = &wqe->acct[index];
/* if we have available workers or no work, no need */
if (!hlist_nulls_empty(&wqe->free_list) || !io_wqe_run_queue(wqe))
return false;
return acct->nr_workers < acct->max_workers;
}
/*
* Manager thread. Tasked with creating new workers, if we need them.
*/
static int io_wq_manager(void *data)
{
struct io_wq *wq = data;
int workers_to_create = num_possible_nodes();
int node;
/* create fixed workers */
refcount_set(&wq->refs, workers_to_create);
for_each_node(node) {
if (!node_online(node))
continue;
if (!create_io_worker(wq, wq->wqes[node], IO_WQ_ACCT_BOUND))
goto err;
workers_to_create--;
}
while (workers_to_create--)
refcount_dec(&wq->refs);
complete(&wq->done);
while (!kthread_should_stop()) {
if (current->task_works)
task_work_run();
for_each_node(node) {
struct io_wqe *wqe = wq->wqes[node];
bool fork_worker[2] = { false, false };
if (!node_online(node))
continue;
spin_lock_irq(&wqe->lock);
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;
spin_unlock_irq(&wqe->lock);
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);
}
set_current_state(TASK_INTERRUPTIBLE);
schedule_timeout(HZ);
}
if (current->task_works)
task_work_run();
return 0;
err:
set_bit(IO_WQ_BIT_ERROR, &wq->state);
set_bit(IO_WQ_BIT_EXIT, &wq->state);
if (refcount_sub_and_test(workers_to_create, &wq->refs))
complete(&wq->done);
return 0;
}
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);
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;
}
static void io_run_cancel(struct io_wq_work *work, struct io_wqe *wqe)
{
struct io_wq *wq = wqe->wq;
do {
struct io_wq_work *old_work = work;
work->flags |= IO_WQ_WORK_CANCEL;
work->func(&work);
work = (work == old_work) ? NULL : work;
wq->free_work(old_work);
} while (work);
}
static void io_wqe_insert_work(struct io_wqe *wqe, struct io_wq_work *work)
{
unsigned int hash;
struct io_wq_work *tail;
if (!io_wq_is_hashed(work)) {
append:
wq_list_add_tail(&work->list, &wqe->work_list);
return;
}
hash = io_get_work_hash(work);
tail = wqe->hash_tail[hash];
wqe->hash_tail[hash] = work;
if (!tail)
goto append;
wq_list_add_after(&work->list, &tail->list, &wqe->work_list);
}
static void io_wqe_enqueue(struct io_wqe *wqe, struct io_wq_work *work)
{
struct io_wqe_acct *acct = io_work_get_acct(wqe, work);
int work_flags;
unsigned long flags;
/*
* 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))) {
io_run_cancel(work, wqe);
return;
}
work_flags = work->flags;
spin_lock_irqsave(&wqe->lock, flags);
io_wqe_insert_work(wqe, work);
wqe->flags &= ~IO_WQE_FLAG_STALLED;
spin_unlock_irqrestore(&wqe->lock, flags);
if ((work_flags & IO_WQ_WORK_CONCURRENT) ||
!atomic_read(&acct->nr_running))
io_wqe_wake_worker(wqe, acct);
}
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);
}
/*
* 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_hash_work(struct io_wq_work *work, void *val)
{
unsigned int bit;
bit = hash_ptr(val, IO_WQ_HASH_ORDER);
work->flags |= (IO_WQ_WORK_HASHED | (bit << IO_WQ_HASH_SHIFT));
}
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,
bool (*func)(struct io_worker *, void *),
void *data)
{
struct io_worker *worker;
bool ret = false;
list_for_each_entry_rcu(worker, &wqe->all_list, all_list) {
if (io_worker_get(worker)) {
/* no task if node is/was offline */
if (worker->task)
ret = func(worker, data);
io_worker_release(worker);
if (ret)
break;
}
}
return ret;
}
void io_wq_cancel_all(struct io_wq *wq)
{
int node;
set_bit(IO_WQ_BIT_CANCEL, &wq->state);
rcu_read_lock();
for_each_node(node) {
struct io_wqe *wqe = wq->wqes[node];
io_wq_for_each_worker(wqe, io_wqe_worker_send_sig, NULL);
}
rcu_read_unlock();
}
struct io_cb_cancel_data {
work_cancel_fn *fn;
void *data;
};
static bool io_wq_worker_cancel(struct io_worker *worker, void *data)
{
struct io_cb_cancel_data *match = data;
unsigned long flags;
bool ret = false;
/*
* Hold the lock to avoid ->cur_work going out of scope, caller
* may dereference the passed in work.
*/
spin_lock_irqsave(&worker->lock, flags);
if (worker->cur_work &&
!(worker->cur_work->flags & IO_WQ_WORK_NO_CANCEL) &&
match->fn(worker->cur_work, match->data)) {
send_sig(SIGINT, worker->task, 1);
ret = true;
}
spin_unlock_irqrestore(&worker->lock, flags);
return ret;
}
static enum io_wq_cancel io_wqe_cancel_work(struct io_wqe *wqe,
struct io_cb_cancel_data *match)
{
struct io_wq_work_node *node, *prev;
struct io_wq_work *work;
unsigned long flags;
bool found = false;
/*
* 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.
*/
spin_lock_irqsave(&wqe->lock, flags);
wq_list_for_each(node, prev, &wqe->work_list) {
work = container_of(node, struct io_wq_work, list);
if (match->fn(work, match->data)) {
wq_list_del(&wqe->work_list, node, prev);
found = true;
break;
}
}
spin_unlock_irqrestore(&wqe->lock, flags);
if (found) {
io_run_cancel(work, wqe);
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 attempt to signal cancellation. The
* completion will run normally in this case.
*/
rcu_read_lock();
found = io_wq_for_each_worker(wqe, io_wq_worker_cancel, match);
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)
{
struct io_cb_cancel_data match = {
.fn = cancel,
.data = data,
};
enum io_wq_cancel ret = IO_WQ_CANCEL_NOTFOUND;
int node;
for_each_node(node) {
struct io_wqe *wqe = wq->wqes[node];
ret = io_wqe_cancel_work(wqe, &match);
if (ret != IO_WQ_CANCEL_NOTFOUND)
break;
}
return ret;
}
static bool io_wq_io_cb_cancel_data(struct io_wq_work *work, void *data)
{
return work == data;
}
enum io_wq_cancel io_wq_cancel_work(struct io_wq *wq, struct io_wq_work *cwork)
{
return io_wq_cancel_cb(wq, io_wq_io_cb_cancel_data, (void *)cwork);
}
static bool io_wq_pid_match(struct io_wq_work *work, void *data)
{
pid_t pid = (pid_t) (unsigned long) data;
return work->task_pid == pid;
}
enum io_wq_cancel io_wq_cancel_pid(struct io_wq *wq, pid_t pid)
{
void *data = (void *) (unsigned long) pid;
return io_wq_cancel_cb(wq, io_wq_pid_match, data);
}
struct io_wq *io_wq_create(unsigned bounded, struct io_wq_data *data)
{
int ret = -ENOMEM, node;
struct io_wq *wq;
if (WARN_ON_ONCE(!data->free_work))
return ERR_PTR(-EINVAL);
wq = kzalloc(sizeof(*wq), GFP_KERNEL);
if (!wq)
return ERR_PTR(-ENOMEM);
wq->wqes = kcalloc(nr_node_ids, sizeof(struct io_wqe *), GFP_KERNEL);
if (!wq->wqes) {
kfree(wq);
return ERR_PTR(-ENOMEM);
}
wq->free_work = data->free_work;
/* caller must already hold a reference to this */
wq->user = data->user;
for_each_node(node) {
struct io_wqe *wqe;
int alloc_node = node;
if (!node_online(alloc_node))
alloc_node = NUMA_NO_NODE;
wqe = kzalloc_node(sizeof(struct io_wqe), GFP_KERNEL, alloc_node);
if (!wqe)
goto err;
wq->wqes[node] = wqe;
wqe->node = alloc_node;
wqe->acct[IO_WQ_ACCT_BOUND].max_workers = bounded;
atomic_set(&wqe->acct[IO_WQ_ACCT_BOUND].nr_running, 0);
if (wq->user) {
wqe->acct[IO_WQ_ACCT_UNBOUND].max_workers =
task_rlimit(current, RLIMIT_NPROC);
}
atomic_set(&wqe->acct[IO_WQ_ACCT_UNBOUND].nr_running, 0);
wqe->wq = wq;
spin_lock_init(&wqe->lock);
INIT_WQ_LIST(&wqe->work_list);
INIT_HLIST_NULLS_HEAD(&wqe->free_list, 0);
INIT_LIST_HEAD(&wqe->all_list);
}
init_completion(&wq->done);
wq->manager = kthread_create(io_wq_manager, wq, "io_wq_manager");
if (!IS_ERR(wq->manager)) {
wake_up_process(wq->manager);
wait_for_completion(&wq->done);
if (test_bit(IO_WQ_BIT_ERROR, &wq->state)) {
ret = -ENOMEM;
goto err;
}
refcount_set(&wq->use_refs, 1);
reinit_completion(&wq->done);
return wq;
}
ret = PTR_ERR(wq->manager);
complete(&wq->done);
err:
for_each_node(node)
kfree(wq->wqes[node]);
kfree(wq->wqes);
kfree(wq);
return ERR_PTR(ret);
}
bool io_wq_get(struct io_wq *wq, struct io_wq_data *data)
{
if (data->free_work != wq->free_work)
return false;
return refcount_inc_not_zero(&wq->use_refs);
}
static bool io_wq_worker_wake(struct io_worker *worker, void *data)
{
wake_up_process(worker->task);
return false;
}
static void __io_wq_destroy(struct io_wq *wq)
{
int node;
set_bit(IO_WQ_BIT_EXIT, &wq->state);
if (wq->manager)
kthread_stop(wq->manager);
rcu_read_lock();
for_each_node(node)
io_wq_for_each_worker(wq->wqes[node], io_wq_worker_wake, NULL);
rcu_read_unlock();
wait_for_completion(&wq->done);
for_each_node(node)
kfree(wq->wqes[node]);
kfree(wq->wqes);
kfree(wq);
}
void io_wq_destroy(struct io_wq *wq)
{
if (refcount_dec_and_test(&wq->use_refs))
__io_wq_destroy(wq);
}
struct task_struct *io_wq_get_task(struct io_wq *wq)
{
return wq->manager;
}