diff options
Diffstat (limited to 'fs/io-wq.c')
| -rw-r--r-- | fs/io-wq.c | 825 |
1 files changed, 825 insertions, 0 deletions
diff --git a/fs/io-wq.c b/fs/io-wq.c new file mode 100644 index 000000000000..37863879e987 --- /dev/null +++ b/fs/io-wq.c @@ -0,0 +1,825 @@ +// 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 "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 */ +}; + +enum { + IO_WQ_BIT_EXIT = 0, /* wq exiting */ + IO_WQ_BIT_CANCEL = 1, /* cancel work on list */ +}; + +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; +}; + +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 + +/* + * 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; + unsigned nr_workers; + unsigned max_workers; + atomic_t nr_running; + + 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; + + struct task_struct *manager; + struct mm_struct *mm; + refcount_t refs; + struct completion done; +}; + +static void io_wq_free_worker(struct rcu_head *head) +{ + struct io_worker *worker = container_of(head, struct io_worker, rcu); + + kfree(worker); +} + +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) +{ + /* + * 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) { + __acquire(&wqe->lock); + spin_unlock_irq(&wqe->lock); + __set_current_state(TASK_RUNNING); + set_fs(KERNEL_DS); + unuse_mm(worker->mm); + mmput(worker->mm); + worker->mm = NULL; + return true; + } + + return false; +} + +static void io_worker_exit(struct io_worker *worker) +{ + struct io_wqe *wqe = worker->wqe; + bool all_done = false; + + /* + * 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(&wqe->nr_running); + 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); + } + wqe->nr_workers--; + all_done = !wqe->nr_workers; + spin_unlock_irq(&wqe->lock); + + /* all workers gone, wq exit can proceed */ + if (all_done && refcount_dec_and_test(&wqe->wq->refs)) + complete(&wqe->wq->done); + + call_rcu(&worker->rcu, io_wq_free_worker); +} + +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); + atomic_inc(&wqe->nr_running); +} + +/* + * 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) +{ + 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; +} + +/* + * 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) +{ + struct io_wq_work *work, *old_work; + 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); + if (!work) + break; +next: + 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; + } + 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; + + 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); + /* dependent work not hashed */ + hash = -1U; + goto next; + } + } while (1); +} + +static inline bool io_wqe_run_queue(struct io_wqe *wqe) + __must_hold(wqe->lock) +{ + if (!list_empty_careful(&wqe->work_list) && + !(wqe->flags & IO_WQE_FLAG_STALLED)) + return true; + return false; +} + +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; +} + +/* + * 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) +{ + bool ret; + + rcu_read_lock(); + ret = io_wqe_activate_free_worker(wqe); + rcu_read_unlock(); + + if (!ret && wqe->nr_workers < wqe->max_workers) + wake_up_process(wqe->wq->manager); +} + +/* + * 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; + atomic_inc(&wqe->nr_running); +} + +/* + * 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); + if (atomic_dec_and_test(&wqe->nr_running) && io_wqe_run_queue(wqe)) + io_wqe_wake_worker(wqe); + spin_unlock_irq(&wqe->lock); +} + +static void create_io_worker(struct io_wq *wq, struct io_wqe *wqe) +{ + struct io_worker *worker; + + worker = kcalloc_node(1, sizeof(*worker), GFP_KERNEL, wqe->node); + if (!worker) + return; + + 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, + "io_wqe_worker-%d", wqe->node); + if (IS_ERR(worker->task)) { + kfree(worker); + return; + } + + spin_lock_irq(&wqe->lock); + hlist_nulls_add_head_rcu(&worker->nulls_node, &wqe->free_list.head); + worker->flags |= IO_WORKER_F_FREE; + if (!wqe->nr_workers) + worker->flags |= IO_WORKER_F_FIXED; + wqe->nr_workers++; + spin_unlock_irq(&wqe->lock); + + wake_up_process(worker->task); +} + +static inline bool io_wqe_need_new_worker(struct io_wqe *wqe) + __must_hold(wqe->lock) +{ + if (!wqe->nr_workers) + return true; + if (hlist_nulls_empty(&wqe->free_list.head) && + wqe->nr_workers < wqe->max_workers && io_wqe_run_queue(wqe)) + return true; + + return false; +} + +/* + * Manager thread. Tasked with creating new workers, if we need them. + */ +static int io_wq_manager(void *data) +{ + struct io_wq *wq = data; + + while (!kthread_should_stop()) { + int i; + + for (i = 0; i < wq->nr_wqes; i++) { + struct io_wqe *wqe = wq->wqes[i]; + bool fork_worker = false; + + spin_lock_irq(&wqe->lock); + fork_worker = io_wqe_need_new_worker(wqe); + spin_unlock_irq(&wqe->lock); + if (fork_worker) + create_io_worker(wq, wqe); + } + set_current_state(TASK_INTERRUPTIBLE); + schedule_timeout(HZ); + } + + return 0; +} + +static void io_wqe_enqueue(struct io_wqe *wqe, struct io_wq_work *work) +{ + unsigned long flags; + + 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); + + if (!atomic_read(&wqe->nr_running)) + io_wqe_wake_worker(wqe); +} + +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(); +} + +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; + 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. + */ + spin_lock_irq(&wqe->lock); + list_for_each_entry(work, &wqe->work_list, list) { + if (work == cwork) { + list_del(&work->list); + found = true; + break; + } + } + spin_unlock_irq(&wqe->lock); + + 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); + io_wqe_enqueue(wqe, &data.work); + wait_for_completion(&data.done); + } +} + +struct io_wq *io_wq_create(unsigned concurrency, struct mm_struct *mm) +{ + 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); + } + + i = 0; + refcount_set(&wq->refs, wq->nr_wqes); + 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; + wqe->max_workers = concurrency; + 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; + atomic_set(&wqe->nr_running, 0); + + i++; + } + + init_completion(&wq->done); + + if (i != wq->nr_wqes) + goto err; + + /* caller must have already done mmgrab() on this mm */ + wq->mm = mm; + + wq->manager = kthread_create(io_wq_manager, wq, "io_wq_manager"); + if (!IS_ERR(wq->manager)) { + wake_up_process(wq->manager); + return wq; + } + + ret = PTR_ERR(wq->manager); + wq->manager = NULL; +err: + complete(&wq->done); + io_wq_destroy(wq); + 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; + + if (wq->manager) { + set_bit(IO_WQ_BIT_EXIT, &wq->state); + 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); +} |