linux/io_uring/io-wq.c
Jens Axboe adeaa3f290 io_uring/io-wq: clear current->worker_private on exit
A recent fix stopped clearing PF_IO_WORKER from current->flags on exit,
which meant that we can now call inc/dec running on the worker after it
has been removed if it ends up scheduling in/out as part of exit.

If this happens after an RCU grace period has passed, then the struct
pointed to by current->worker_private may have been freed, and we can
now be accessing memory that is freed.

Ensure this doesn't happen by clearing the task worker_private field.
Both io_wq_worker_running() and io_wq_worker_sleeping() check this
field before going any further, and we don't need any accounting etc
done after this worker has exited.

Fixes: fd37b88400 ("io_uring/io-wq: don't clear PF_IO_WORKER on exit")
Reported-by: Zorro Lang <zlang@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2023-06-14 12:54:55 -06:00

1352 lines
32 KiB
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/percpu.h>
#include <linux/slab.h>
#include <linux/rculist_nulls.h>
#include <linux/cpu.h>
#include <linux/task_work.h>
#include <linux/audit.h>
#include <linux/mmu_context.h>
#include <uapi/linux/io_uring.h>
#include "io-wq.h"
#include "slist.h"
#include "io_uring.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_BOUND = 8, /* is doing bounded work */
};
enum {
IO_WQ_BIT_EXIT = 0, /* wq exiting */
};
enum {
IO_ACCT_STALLED_BIT = 0, /* stalled on hash */
};
/*
* One for each thread in a wq 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_wq *wq;
struct io_wq_work *cur_work;
struct io_wq_work *next_work;
raw_spinlock_t lock;
struct completion ref_done;
unsigned long create_state;
struct callback_head create_work;
int create_index;
union {
struct rcu_head rcu;
struct work_struct work;
};
};
#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_wq_acct {
unsigned nr_workers;
unsigned max_workers;
int index;
atomic_t nr_running;
raw_spinlock_t lock;
struct io_wq_work_list work_list;
unsigned long flags;
};
enum {
IO_WQ_ACCT_BOUND,
IO_WQ_ACCT_UNBOUND,
IO_WQ_ACCT_NR,
};
/*
* Per io_wq state
*/
struct io_wq {
unsigned long state;
free_work_fn *free_work;
io_wq_work_fn *do_work;
struct io_wq_hash *hash;
atomic_t worker_refs;
struct completion worker_done;
struct hlist_node cpuhp_node;
struct task_struct *task;
struct io_wq_acct acct[IO_WQ_ACCT_NR];
/* lock protects access to elements below */
raw_spinlock_t lock;
struct hlist_nulls_head free_list;
struct list_head all_list;
struct wait_queue_entry wait;
struct io_wq_work *hash_tail[IO_WQ_NR_HASH_BUCKETS];
cpumask_var_t cpu_mask;
};
static enum cpuhp_state io_wq_online;
struct io_cb_cancel_data {
work_cancel_fn *fn;
void *data;
int nr_running;
int nr_pending;
bool cancel_all;
};
static bool create_io_worker(struct io_wq *wq, int index);
static void io_wq_dec_running(struct io_worker *worker);
static bool io_acct_cancel_pending_work(struct io_wq *wq,
struct io_wq_acct *acct,
struct io_cb_cancel_data *match);
static void create_worker_cb(struct callback_head *cb);
static void io_wq_cancel_tw_create(struct io_wq *wq);
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))
complete(&worker->ref_done);
}
static inline struct io_wq_acct *io_get_acct(struct io_wq *wq, bool bound)
{
return &wq->acct[bound ? IO_WQ_ACCT_BOUND : IO_WQ_ACCT_UNBOUND];
}
static inline struct io_wq_acct *io_work_get_acct(struct io_wq *wq,
struct io_wq_work *work)
{
return io_get_acct(wq, !(work->flags & IO_WQ_WORK_UNBOUND));
}
static inline struct io_wq_acct *io_wq_get_acct(struct io_worker *worker)
{
return io_get_acct(worker->wq, worker->flags & IO_WORKER_F_BOUND);
}
static void io_worker_ref_put(struct io_wq *wq)
{
if (atomic_dec_and_test(&wq->worker_refs))
complete(&wq->worker_done);
}
static void io_worker_cancel_cb(struct io_worker *worker)
{
struct io_wq_acct *acct = io_wq_get_acct(worker);
struct io_wq *wq = worker->wq;
atomic_dec(&acct->nr_running);
raw_spin_lock(&wq->lock);
acct->nr_workers--;
raw_spin_unlock(&wq->lock);
io_worker_ref_put(wq);
clear_bit_unlock(0, &worker->create_state);
io_worker_release(worker);
}
static bool io_task_worker_match(struct callback_head *cb, void *data)
{
struct io_worker *worker;
if (cb->func != create_worker_cb)
return false;
worker = container_of(cb, struct io_worker, create_work);
return worker == data;
}
static void io_worker_exit(struct io_worker *worker)
{
struct io_wq *wq = worker->wq;
while (1) {
struct callback_head *cb = task_work_cancel_match(wq->task,
io_task_worker_match, worker);
if (!cb)
break;
io_worker_cancel_cb(worker);
}
io_worker_release(worker);
wait_for_completion(&worker->ref_done);
raw_spin_lock(&wq->lock);
if (worker->flags & IO_WORKER_F_FREE)
hlist_nulls_del_rcu(&worker->nulls_node);
list_del_rcu(&worker->all_list);
raw_spin_unlock(&wq->lock);
io_wq_dec_running(worker);
/*
* this worker is a goner, clear ->worker_private to avoid any
* inc/dec running calls that could happen as part of exit from
* touching 'worker'.
*/
current->worker_private = NULL;
kfree_rcu(worker, rcu);
io_worker_ref_put(wq);
do_exit(0);
}
static inline bool io_acct_run_queue(struct io_wq_acct *acct)
{
bool ret = false;
raw_spin_lock(&acct->lock);
if (!wq_list_empty(&acct->work_list) &&
!test_bit(IO_ACCT_STALLED_BIT, &acct->flags))
ret = true;
raw_spin_unlock(&acct->lock);
return ret;
}
/*
* Check head of free list for an available worker. If one isn't available,
* caller must create one.
*/
static bool io_wq_activate_free_worker(struct io_wq *wq,
struct io_wq_acct *acct)
__must_hold(RCU)
{
struct hlist_nulls_node *n;
struct io_worker *worker;
/*
* Iterate free_list and see if we can find an idle worker to
* activate. If a given worker is on the free_list but in the process
* of exiting, keep trying.
*/
hlist_nulls_for_each_entry_rcu(worker, n, &wq->free_list, nulls_node) {
if (!io_worker_get(worker))
continue;
if (io_wq_get_acct(worker) != acct) {
io_worker_release(worker);
continue;
}
if (wake_up_process(worker->task)) {
io_worker_release(worker);
return true;
}
io_worker_release(worker);
}
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, create one.
*/
static bool io_wq_create_worker(struct io_wq *wq, struct io_wq_acct *acct)
{
/*
* Most likely an attempt to queue unbounded work on an io_wq that
* wasn't setup with any unbounded workers.
*/
if (unlikely(!acct->max_workers))
pr_warn_once("io-wq is not configured for unbound workers");
raw_spin_lock(&wq->lock);
if (acct->nr_workers >= acct->max_workers) {
raw_spin_unlock(&wq->lock);
return true;
}
acct->nr_workers++;
raw_spin_unlock(&wq->lock);
atomic_inc(&acct->nr_running);
atomic_inc(&wq->worker_refs);
return create_io_worker(wq, acct->index);
}
static void io_wq_inc_running(struct io_worker *worker)
{
struct io_wq_acct *acct = io_wq_get_acct(worker);
atomic_inc(&acct->nr_running);
}
static void create_worker_cb(struct callback_head *cb)
{
struct io_worker *worker;
struct io_wq *wq;
struct io_wq_acct *acct;
bool do_create = false;
worker = container_of(cb, struct io_worker, create_work);
wq = worker->wq;
acct = &wq->acct[worker->create_index];
raw_spin_lock(&wq->lock);
if (acct->nr_workers < acct->max_workers) {
acct->nr_workers++;
do_create = true;
}
raw_spin_unlock(&wq->lock);
if (do_create) {
create_io_worker(wq, worker->create_index);
} else {
atomic_dec(&acct->nr_running);
io_worker_ref_put(wq);
}
clear_bit_unlock(0, &worker->create_state);
io_worker_release(worker);
}
static bool io_queue_worker_create(struct io_worker *worker,
struct io_wq_acct *acct,
task_work_func_t func)
{
struct io_wq *wq = worker->wq;
/* raced with exit, just ignore create call */
if (test_bit(IO_WQ_BIT_EXIT, &wq->state))
goto fail;
if (!io_worker_get(worker))
goto fail;
/*
* create_state manages ownership of create_work/index. We should
* only need one entry per worker, as the worker going to sleep
* will trigger the condition, and waking will clear it once it
* runs the task_work.
*/
if (test_bit(0, &worker->create_state) ||
test_and_set_bit_lock(0, &worker->create_state))
goto fail_release;
atomic_inc(&wq->worker_refs);
init_task_work(&worker->create_work, func);
worker->create_index = acct->index;
if (!task_work_add(wq->task, &worker->create_work, TWA_SIGNAL)) {
/*
* EXIT may have been set after checking it above, check after
* adding the task_work and remove any creation item if it is
* now set. wq exit does that too, but we can have added this
* work item after we canceled in io_wq_exit_workers().
*/
if (test_bit(IO_WQ_BIT_EXIT, &wq->state))
io_wq_cancel_tw_create(wq);
io_worker_ref_put(wq);
return true;
}
io_worker_ref_put(wq);
clear_bit_unlock(0, &worker->create_state);
fail_release:
io_worker_release(worker);
fail:
atomic_dec(&acct->nr_running);
io_worker_ref_put(wq);
return false;
}
static void io_wq_dec_running(struct io_worker *worker)
{
struct io_wq_acct *acct = io_wq_get_acct(worker);
struct io_wq *wq = worker->wq;
if (!(worker->flags & IO_WORKER_F_UP))
return;
if (!atomic_dec_and_test(&acct->nr_running))
return;
if (!io_acct_run_queue(acct))
return;
atomic_inc(&acct->nr_running);
atomic_inc(&wq->worker_refs);
io_queue_worker_create(worker, acct, create_worker_cb);
}
/*
* 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_wq *wq, struct io_worker *worker)
{
if (worker->flags & IO_WORKER_F_FREE) {
worker->flags &= ~IO_WORKER_F_FREE;
raw_spin_lock(&wq->lock);
hlist_nulls_del_init_rcu(&worker->nulls_node);
raw_spin_unlock(&wq->lock);
}
}
/*
* No work, worker going to sleep. Move to freelist.
*/
static void __io_worker_idle(struct io_wq *wq, struct io_worker *worker)
__must_hold(wq->lock)
{
if (!(worker->flags & IO_WORKER_F_FREE)) {
worker->flags |= IO_WORKER_F_FREE;
hlist_nulls_add_head_rcu(&worker->nulls_node, &wq->free_list);
}
}
static inline unsigned int io_get_work_hash(struct io_wq_work *work)
{
return work->flags >> IO_WQ_HASH_SHIFT;
}
static bool io_wait_on_hash(struct io_wq *wq, unsigned int hash)
{
bool ret = false;
spin_lock_irq(&wq->hash->wait.lock);
if (list_empty(&wq->wait.entry)) {
__add_wait_queue(&wq->hash->wait, &wq->wait);
if (!test_bit(hash, &wq->hash->map)) {
__set_current_state(TASK_RUNNING);
list_del_init(&wq->wait.entry);
ret = true;
}
}
spin_unlock_irq(&wq->hash->wait.lock);
return ret;
}
static struct io_wq_work *io_get_next_work(struct io_wq_acct *acct,
struct io_worker *worker)
__must_hold(acct->lock)
{
struct io_wq_work_node *node, *prev;
struct io_wq_work *work, *tail;
unsigned int stall_hash = -1U;
struct io_wq *wq = worker->wq;
wq_list_for_each(node, prev, &acct->work_list) {
unsigned int hash;
work = container_of(node, struct io_wq_work, list);
/* not hashed, can run anytime */
if (!io_wq_is_hashed(work)) {
wq_list_del(&acct->work_list, node, prev);
return work;
}
hash = io_get_work_hash(work);
/* all items with this hash lie in [work, tail] */
tail = wq->hash_tail[hash];
/* hashed, can run if not already running */
if (!test_and_set_bit(hash, &wq->hash->map)) {
wq->hash_tail[hash] = NULL;
wq_list_cut(&acct->work_list, &tail->list, prev);
return work;
}
if (stall_hash == -1U)
stall_hash = hash;
/* fast forward to a next hash, for-each will fix up @prev */
node = &tail->list;
}
if (stall_hash != -1U) {
bool unstalled;
/*
* Set this before dropping the lock to avoid racing with new
* work being added and clearing the stalled bit.
*/
set_bit(IO_ACCT_STALLED_BIT, &acct->flags);
raw_spin_unlock(&acct->lock);
unstalled = io_wait_on_hash(wq, stall_hash);
raw_spin_lock(&acct->lock);
if (unstalled) {
clear_bit(IO_ACCT_STALLED_BIT, &acct->flags);
if (wq_has_sleeper(&wq->hash->wait))
wake_up(&wq->hash->wait);
}
}
return NULL;
}
static void io_assign_current_work(struct io_worker *worker,
struct io_wq_work *work)
{
if (work) {
io_run_task_work();
cond_resched();
}
raw_spin_lock(&worker->lock);
worker->cur_work = work;
worker->next_work = NULL;
raw_spin_unlock(&worker->lock);
}
static void io_worker_handle_work(struct io_worker *worker)
{
struct io_wq_acct *acct = io_wq_get_acct(worker);
struct io_wq *wq = worker->wq;
bool do_kill = test_bit(IO_WQ_BIT_EXIT, &wq->state);
do {
struct io_wq_work *work;
/*
* 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.
*/
raw_spin_lock(&acct->lock);
work = io_get_next_work(acct, worker);
raw_spin_unlock(&acct->lock);
if (work) {
__io_worker_busy(wq, worker);
/*
* Make sure cancelation can find this, even before
* it becomes the active work. That avoids a window
* where the work has been removed from our general
* work list, but isn't yet discoverable as the
* current work item for this worker.
*/
raw_spin_lock(&worker->lock);
worker->next_work = work;
raw_spin_unlock(&worker->lock);
} else {
break;
}
io_assign_current_work(worker, work);
__set_current_state(TASK_RUNNING);
/* handle a whole dependent link */
do {
struct io_wq_work *next_hashed, *linked;
unsigned int hash = io_get_work_hash(work);
next_hashed = wq_next_work(work);
if (unlikely(do_kill) && (work->flags & IO_WQ_WORK_UNBOUND))
work->flags |= IO_WQ_WORK_CANCEL;
wq->do_work(work);
io_assign_current_work(worker, NULL);
linked = wq->free_work(work);
work = next_hashed;
if (!work && linked && !io_wq_is_hashed(linked)) {
work = linked;
linked = NULL;
}
io_assign_current_work(worker, work);
if (linked)
io_wq_enqueue(wq, linked);
if (hash != -1U && !next_hashed) {
/* serialize hash clear with wake_up() */
spin_lock_irq(&wq->hash->wait.lock);
clear_bit(hash, &wq->hash->map);
clear_bit(IO_ACCT_STALLED_BIT, &acct->flags);
spin_unlock_irq(&wq->hash->wait.lock);
if (wq_has_sleeper(&wq->hash->wait))
wake_up(&wq->hash->wait);
}
} while (work);
} while (1);
}
static int io_wq_worker(void *data)
{
struct io_worker *worker = data;
struct io_wq_acct *acct = io_wq_get_acct(worker);
struct io_wq *wq = worker->wq;
bool exit_mask = false, last_timeout = false;
char buf[TASK_COMM_LEN];
worker->flags |= (IO_WORKER_F_UP | IO_WORKER_F_RUNNING);
snprintf(buf, sizeof(buf), "iou-wrk-%d", wq->task->pid);
set_task_comm(current, buf);
while (!test_bit(IO_WQ_BIT_EXIT, &wq->state)) {
long ret;
set_current_state(TASK_INTERRUPTIBLE);
while (io_acct_run_queue(acct))
io_worker_handle_work(worker);
raw_spin_lock(&wq->lock);
/*
* Last sleep timed out. Exit if we're not the last worker,
* or if someone modified our affinity.
*/
if (last_timeout && (exit_mask || acct->nr_workers > 1)) {
acct->nr_workers--;
raw_spin_unlock(&wq->lock);
__set_current_state(TASK_RUNNING);
break;
}
last_timeout = false;
__io_worker_idle(wq, worker);
raw_spin_unlock(&wq->lock);
if (io_run_task_work())
continue;
ret = schedule_timeout(WORKER_IDLE_TIMEOUT);
if (signal_pending(current)) {
struct ksignal ksig;
if (!get_signal(&ksig))
continue;
break;
}
if (!ret) {
last_timeout = true;
exit_mask = !cpumask_test_cpu(raw_smp_processor_id(),
wq->cpu_mask);
}
}
if (test_bit(IO_WQ_BIT_EXIT, &wq->state))
io_worker_handle_work(worker);
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 = tsk->worker_private;
if (!worker)
return;
if (!(worker->flags & IO_WORKER_F_UP))
return;
if (worker->flags & IO_WORKER_F_RUNNING)
return;
worker->flags |= IO_WORKER_F_RUNNING;
io_wq_inc_running(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 create a new one.
*/
void io_wq_worker_sleeping(struct task_struct *tsk)
{
struct io_worker *worker = tsk->worker_private;
if (!worker)
return;
if (!(worker->flags & IO_WORKER_F_UP))
return;
if (!(worker->flags & IO_WORKER_F_RUNNING))
return;
worker->flags &= ~IO_WORKER_F_RUNNING;
io_wq_dec_running(worker);
}
static void io_init_new_worker(struct io_wq *wq, struct io_worker *worker,
struct task_struct *tsk)
{
tsk->worker_private = worker;
worker->task = tsk;
set_cpus_allowed_ptr(tsk, wq->cpu_mask);
raw_spin_lock(&wq->lock);
hlist_nulls_add_head_rcu(&worker->nulls_node, &wq->free_list);
list_add_tail_rcu(&worker->all_list, &wq->all_list);
worker->flags |= IO_WORKER_F_FREE;
raw_spin_unlock(&wq->lock);
wake_up_new_task(tsk);
}
static bool io_wq_work_match_all(struct io_wq_work *work, void *data)
{
return true;
}
static inline bool io_should_retry_thread(long err)
{
/*
* Prevent perpetual task_work retry, if the task (or its group) is
* exiting.
*/
if (fatal_signal_pending(current))
return false;
switch (err) {
case -EAGAIN:
case -ERESTARTSYS:
case -ERESTARTNOINTR:
case -ERESTARTNOHAND:
return true;
default:
return false;
}
}
static void create_worker_cont(struct callback_head *cb)
{
struct io_worker *worker;
struct task_struct *tsk;
struct io_wq *wq;
worker = container_of(cb, struct io_worker, create_work);
clear_bit_unlock(0, &worker->create_state);
wq = worker->wq;
tsk = create_io_thread(io_wq_worker, worker, NUMA_NO_NODE);
if (!IS_ERR(tsk)) {
io_init_new_worker(wq, worker, tsk);
io_worker_release(worker);
return;
} else if (!io_should_retry_thread(PTR_ERR(tsk))) {
struct io_wq_acct *acct = io_wq_get_acct(worker);
atomic_dec(&acct->nr_running);
raw_spin_lock(&wq->lock);
acct->nr_workers--;
if (!acct->nr_workers) {
struct io_cb_cancel_data match = {
.fn = io_wq_work_match_all,
.cancel_all = true,
};
raw_spin_unlock(&wq->lock);
while (io_acct_cancel_pending_work(wq, acct, &match))
;
} else {
raw_spin_unlock(&wq->lock);
}
io_worker_ref_put(wq);
kfree(worker);
return;
}
/* re-create attempts grab a new worker ref, drop the existing one */
io_worker_release(worker);
schedule_work(&worker->work);
}
static void io_workqueue_create(struct work_struct *work)
{
struct io_worker *worker = container_of(work, struct io_worker, work);
struct io_wq_acct *acct = io_wq_get_acct(worker);
if (!io_queue_worker_create(worker, acct, create_worker_cont))
kfree(worker);
}
static bool create_io_worker(struct io_wq *wq, int index)
{
struct io_wq_acct *acct = &wq->acct[index];
struct io_worker *worker;
struct task_struct *tsk;
__set_current_state(TASK_RUNNING);
worker = kzalloc(sizeof(*worker), GFP_KERNEL);
if (!worker) {
fail:
atomic_dec(&acct->nr_running);
raw_spin_lock(&wq->lock);
acct->nr_workers--;
raw_spin_unlock(&wq->lock);
io_worker_ref_put(wq);
return false;
}
refcount_set(&worker->ref, 1);
worker->wq = wq;
raw_spin_lock_init(&worker->lock);
init_completion(&worker->ref_done);
if (index == IO_WQ_ACCT_BOUND)
worker->flags |= IO_WORKER_F_BOUND;
tsk = create_io_thread(io_wq_worker, worker, NUMA_NO_NODE);
if (!IS_ERR(tsk)) {
io_init_new_worker(wq, worker, tsk);
} else if (!io_should_retry_thread(PTR_ERR(tsk))) {
kfree(worker);
goto fail;
} else {
INIT_WORK(&worker->work, io_workqueue_create);
schedule_work(&worker->work);
}
return true;
}
/*
* 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_wq *wq,
bool (*func)(struct io_worker *, void *),
void *data)
{
struct io_worker *worker;
bool ret = false;
list_for_each_entry_rcu(worker, &wq->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;
}
static bool io_wq_worker_wake(struct io_worker *worker, void *data)
{
__set_notify_signal(worker->task);
wake_up_process(worker->task);
return false;
}
static void io_run_cancel(struct io_wq_work *work, struct io_wq *wq)
{
do {
work->flags |= IO_WQ_WORK_CANCEL;
wq->do_work(work);
work = wq->free_work(work);
} while (work);
}
static void io_wq_insert_work(struct io_wq *wq, struct io_wq_work *work)
{
struct io_wq_acct *acct = io_work_get_acct(wq, work);
unsigned int hash;
struct io_wq_work *tail;
if (!io_wq_is_hashed(work)) {
append:
wq_list_add_tail(&work->list, &acct->work_list);
return;
}
hash = io_get_work_hash(work);
tail = wq->hash_tail[hash];
wq->hash_tail[hash] = work;
if (!tail)
goto append;
wq_list_add_after(&work->list, &tail->list, &acct->work_list);
}
static bool io_wq_work_match_item(struct io_wq_work *work, void *data)
{
return work == data;
}
void io_wq_enqueue(struct io_wq *wq, struct io_wq_work *work)
{
struct io_wq_acct *acct = io_work_get_acct(wq, work);
struct io_cb_cancel_data match;
unsigned work_flags = work->flags;
bool do_create;
/*
* If io-wq is exiting for this task, or if the request has explicitly
* been marked as one that should not get executed, cancel it here.
*/
if (test_bit(IO_WQ_BIT_EXIT, &wq->state) ||
(work->flags & IO_WQ_WORK_CANCEL)) {
io_run_cancel(work, wq);
return;
}
raw_spin_lock(&acct->lock);
io_wq_insert_work(wq, work);
clear_bit(IO_ACCT_STALLED_BIT, &acct->flags);
raw_spin_unlock(&acct->lock);
raw_spin_lock(&wq->lock);
rcu_read_lock();
do_create = !io_wq_activate_free_worker(wq, acct);
rcu_read_unlock();
raw_spin_unlock(&wq->lock);
if (do_create && ((work_flags & IO_WQ_WORK_CONCURRENT) ||
!atomic_read(&acct->nr_running))) {
bool did_create;
did_create = io_wq_create_worker(wq, acct);
if (likely(did_create))
return;
raw_spin_lock(&wq->lock);
if (acct->nr_workers) {
raw_spin_unlock(&wq->lock);
return;
}
raw_spin_unlock(&wq->lock);
/* fatal condition, failed to create the first worker */
match.fn = io_wq_work_match_item,
match.data = work,
match.cancel_all = false,
io_acct_cancel_pending_work(wq, acct, &match);
}
}
/*
* 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_wq_worker_cancel(struct io_worker *worker,
struct io_cb_cancel_data *match,
struct io_wq_work *work)
{
if (work && match->fn(work, match->data)) {
work->flags |= IO_WQ_WORK_CANCEL;
__set_notify_signal(worker->task);
return true;
}
return false;
}
static bool io_wq_worker_cancel(struct io_worker *worker, void *data)
{
struct io_cb_cancel_data *match = data;
/*
* Hold the lock to avoid ->cur_work going out of scope, caller
* may dereference the passed in work.
*/
raw_spin_lock(&worker->lock);
if (__io_wq_worker_cancel(worker, match, worker->cur_work) ||
__io_wq_worker_cancel(worker, match, worker->next_work))
match->nr_running++;
raw_spin_unlock(&worker->lock);
return match->nr_running && !match->cancel_all;
}
static inline void io_wq_remove_pending(struct io_wq *wq,
struct io_wq_work *work,
struct io_wq_work_node *prev)
{
struct io_wq_acct *acct = io_work_get_acct(wq, work);
unsigned int hash = io_get_work_hash(work);
struct io_wq_work *prev_work = NULL;
if (io_wq_is_hashed(work) && work == wq->hash_tail[hash]) {
if (prev)
prev_work = container_of(prev, struct io_wq_work, list);
if (prev_work && io_get_work_hash(prev_work) == hash)
wq->hash_tail[hash] = prev_work;
else
wq->hash_tail[hash] = NULL;
}
wq_list_del(&acct->work_list, &work->list, prev);
}
static bool io_acct_cancel_pending_work(struct io_wq *wq,
struct io_wq_acct *acct,
struct io_cb_cancel_data *match)
{
struct io_wq_work_node *node, *prev;
struct io_wq_work *work;
raw_spin_lock(&acct->lock);
wq_list_for_each(node, prev, &acct->work_list) {
work = container_of(node, struct io_wq_work, list);
if (!match->fn(work, match->data))
continue;
io_wq_remove_pending(wq, work, prev);
raw_spin_unlock(&acct->lock);
io_run_cancel(work, wq);
match->nr_pending++;
/* not safe to continue after unlock */
return true;
}
raw_spin_unlock(&acct->lock);
return false;
}
static void io_wq_cancel_pending_work(struct io_wq *wq,
struct io_cb_cancel_data *match)
{
int i;
retry:
for (i = 0; i < IO_WQ_ACCT_NR; i++) {
struct io_wq_acct *acct = io_get_acct(wq, i == 0);
if (io_acct_cancel_pending_work(wq, acct, match)) {
if (match->cancel_all)
goto retry;
break;
}
}
}
static void io_wq_cancel_running_work(struct io_wq *wq,
struct io_cb_cancel_data *match)
{
rcu_read_lock();
io_wq_for_each_worker(wq, io_wq_worker_cancel, match);
rcu_read_unlock();
}
enum io_wq_cancel io_wq_cancel_cb(struct io_wq *wq, work_cancel_fn *cancel,
void *data, bool cancel_all)
{
struct io_cb_cancel_data match = {
.fn = cancel,
.data = data,
.cancel_all = cancel_all,
};
/*
* 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.
*
* Then 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.
*
* Do both of these while holding the wq->lock, to ensure that
* we'll find a work item regardless of state.
*/
io_wq_cancel_pending_work(wq, &match);
if (match.nr_pending && !match.cancel_all)
return IO_WQ_CANCEL_OK;
raw_spin_lock(&wq->lock);
io_wq_cancel_running_work(wq, &match);
raw_spin_unlock(&wq->lock);
if (match.nr_running && !match.cancel_all)
return IO_WQ_CANCEL_RUNNING;
if (match.nr_running)
return IO_WQ_CANCEL_RUNNING;
if (match.nr_pending)
return IO_WQ_CANCEL_OK;
return IO_WQ_CANCEL_NOTFOUND;
}
static int io_wq_hash_wake(struct wait_queue_entry *wait, unsigned mode,
int sync, void *key)
{
struct io_wq *wq = container_of(wait, struct io_wq, wait);
int i;
list_del_init(&wait->entry);
rcu_read_lock();
for (i = 0; i < IO_WQ_ACCT_NR; i++) {
struct io_wq_acct *acct = &wq->acct[i];
if (test_and_clear_bit(IO_ACCT_STALLED_BIT, &acct->flags))
io_wq_activate_free_worker(wq, acct);
}
rcu_read_unlock();
return 1;
}
struct io_wq *io_wq_create(unsigned bounded, struct io_wq_data *data)
{
int ret, i;
struct io_wq *wq;
if (WARN_ON_ONCE(!data->free_work || !data->do_work))
return ERR_PTR(-EINVAL);
if (WARN_ON_ONCE(!bounded))
return ERR_PTR(-EINVAL);
wq = kzalloc(sizeof(struct io_wq), GFP_KERNEL);
if (!wq)
return ERR_PTR(-ENOMEM);
ret = cpuhp_state_add_instance_nocalls(io_wq_online, &wq->cpuhp_node);
if (ret)
goto err_wq;
refcount_inc(&data->hash->refs);
wq->hash = data->hash;
wq->free_work = data->free_work;
wq->do_work = data->do_work;
ret = -ENOMEM;
if (!alloc_cpumask_var(&wq->cpu_mask, GFP_KERNEL))
goto err;
cpumask_copy(wq->cpu_mask, cpu_possible_mask);
wq->acct[IO_WQ_ACCT_BOUND].max_workers = bounded;
wq->acct[IO_WQ_ACCT_UNBOUND].max_workers =
task_rlimit(current, RLIMIT_NPROC);
INIT_LIST_HEAD(&wq->wait.entry);
wq->wait.func = io_wq_hash_wake;
for (i = 0; i < IO_WQ_ACCT_NR; i++) {
struct io_wq_acct *acct = &wq->acct[i];
acct->index = i;
atomic_set(&acct->nr_running, 0);
INIT_WQ_LIST(&acct->work_list);
raw_spin_lock_init(&acct->lock);
}
raw_spin_lock_init(&wq->lock);
INIT_HLIST_NULLS_HEAD(&wq->free_list, 0);
INIT_LIST_HEAD(&wq->all_list);
wq->task = get_task_struct(data->task);
atomic_set(&wq->worker_refs, 1);
init_completion(&wq->worker_done);
return wq;
err:
io_wq_put_hash(data->hash);
cpuhp_state_remove_instance_nocalls(io_wq_online, &wq->cpuhp_node);
free_cpumask_var(wq->cpu_mask);
err_wq:
kfree(wq);
return ERR_PTR(ret);
}
static bool io_task_work_match(struct callback_head *cb, void *data)
{
struct io_worker *worker;
if (cb->func != create_worker_cb && cb->func != create_worker_cont)
return false;
worker = container_of(cb, struct io_worker, create_work);
return worker->wq == data;
}
void io_wq_exit_start(struct io_wq *wq)
{
set_bit(IO_WQ_BIT_EXIT, &wq->state);
}
static void io_wq_cancel_tw_create(struct io_wq *wq)
{
struct callback_head *cb;
while ((cb = task_work_cancel_match(wq->task, io_task_work_match, wq)) != NULL) {
struct io_worker *worker;
worker = container_of(cb, struct io_worker, create_work);
io_worker_cancel_cb(worker);
/*
* Only the worker continuation helper has worker allocated and
* hence needs freeing.
*/
if (cb->func == create_worker_cont)
kfree(worker);
}
}
static void io_wq_exit_workers(struct io_wq *wq)
{
if (!wq->task)
return;
io_wq_cancel_tw_create(wq);
rcu_read_lock();
io_wq_for_each_worker(wq, io_wq_worker_wake, NULL);
rcu_read_unlock();
io_worker_ref_put(wq);
wait_for_completion(&wq->worker_done);
spin_lock_irq(&wq->hash->wait.lock);
list_del_init(&wq->wait.entry);
spin_unlock_irq(&wq->hash->wait.lock);
put_task_struct(wq->task);
wq->task = NULL;
}
static void io_wq_destroy(struct io_wq *wq)
{
struct io_cb_cancel_data match = {
.fn = io_wq_work_match_all,
.cancel_all = true,
};
cpuhp_state_remove_instance_nocalls(io_wq_online, &wq->cpuhp_node);
io_wq_cancel_pending_work(wq, &match);
free_cpumask_var(wq->cpu_mask);
io_wq_put_hash(wq->hash);
kfree(wq);
}
void io_wq_put_and_exit(struct io_wq *wq)
{
WARN_ON_ONCE(!test_bit(IO_WQ_BIT_EXIT, &wq->state));
io_wq_exit_workers(wq);
io_wq_destroy(wq);
}
struct online_data {
unsigned int cpu;
bool online;
};
static bool io_wq_worker_affinity(struct io_worker *worker, void *data)
{
struct online_data *od = data;
if (od->online)
cpumask_set_cpu(od->cpu, worker->wq->cpu_mask);
else
cpumask_clear_cpu(od->cpu, worker->wq->cpu_mask);
return false;
}
static int __io_wq_cpu_online(struct io_wq *wq, unsigned int cpu, bool online)
{
struct online_data od = {
.cpu = cpu,
.online = online
};
rcu_read_lock();
io_wq_for_each_worker(wq, io_wq_worker_affinity, &od);
rcu_read_unlock();
return 0;
}
static int io_wq_cpu_online(unsigned int cpu, struct hlist_node *node)
{
struct io_wq *wq = hlist_entry_safe(node, struct io_wq, cpuhp_node);
return __io_wq_cpu_online(wq, cpu, true);
}
static int io_wq_cpu_offline(unsigned int cpu, struct hlist_node *node)
{
struct io_wq *wq = hlist_entry_safe(node, struct io_wq, cpuhp_node);
return __io_wq_cpu_online(wq, cpu, false);
}
int io_wq_cpu_affinity(struct io_wq *wq, cpumask_var_t mask)
{
rcu_read_lock();
if (mask)
cpumask_copy(wq->cpu_mask, mask);
else
cpumask_copy(wq->cpu_mask, cpu_possible_mask);
rcu_read_unlock();
return 0;
}
/*
* Set max number of unbounded workers, returns old value. If new_count is 0,
* then just return the old value.
*/
int io_wq_max_workers(struct io_wq *wq, int *new_count)
{
struct io_wq_acct *acct;
int prev[IO_WQ_ACCT_NR];
int i;
BUILD_BUG_ON((int) IO_WQ_ACCT_BOUND != (int) IO_WQ_BOUND);
BUILD_BUG_ON((int) IO_WQ_ACCT_UNBOUND != (int) IO_WQ_UNBOUND);
BUILD_BUG_ON((int) IO_WQ_ACCT_NR != 2);
for (i = 0; i < IO_WQ_ACCT_NR; i++) {
if (new_count[i] > task_rlimit(current, RLIMIT_NPROC))
new_count[i] = task_rlimit(current, RLIMIT_NPROC);
}
for (i = 0; i < IO_WQ_ACCT_NR; i++)
prev[i] = 0;
rcu_read_lock();
raw_spin_lock(&wq->lock);
for (i = 0; i < IO_WQ_ACCT_NR; i++) {
acct = &wq->acct[i];
prev[i] = max_t(int, acct->max_workers, prev[i]);
if (new_count[i])
acct->max_workers = new_count[i];
}
raw_spin_unlock(&wq->lock);
rcu_read_unlock();
for (i = 0; i < IO_WQ_ACCT_NR; i++)
new_count[i] = prev[i];
return 0;
}
static __init int io_wq_init(void)
{
int ret;
ret = cpuhp_setup_state_multi(CPUHP_AP_ONLINE_DYN, "io-wq/online",
io_wq_cpu_online, io_wq_cpu_offline);
if (ret < 0)
return ret;
io_wq_online = ret;
return 0;
}
subsys_initcall(io_wq_init);