// SPDX-License-Identifier: GPL-2.0/* * Task work handling for io_uring */#include <linux/kernel.h>#include <linux/errno.h>#include <linux/sched/signal.h>#include <linux/io_uring.h>#include <linux/indirect_call_wrapper.h> #include "io_uring.h"#include "tctx.h"#include "poll.h"#include "rw.h"#include "eventfd.h"#include "wait.h"#include "mpscq.h" static void ctx_flush_and_put(struct io_ring_ctx *ctx, io_tw_token_t tw){	if (!ctx)		return;	if (ctx->flags & IORING_SETUP_TASKRUN_FLAG)		atomic_andnot(IORING_SQ_TASKRUN, &ctx->rings->sq_flags); 	io_submit_flush_completions(ctx);	mutex_unlock(&ctx->uring_lock);	percpu_ref_put(&ctx->refs);} void io_tctx_fallback_work(struct work_struct *work){	struct io_uring_task *tctx = container_of(work, struct io_uring_task,						  fallback_work);	unsigned int count = 0; 	/*	 * Run the entries directly. We're in PF_KTHRED context, hence	 * io_should_terminate_tw() is true and they will be marked as	 * canceled.	 */	tctx_task_work_run(tctx, UINT_MAX, &count);	put_task_struct(tctx->task);} static void io_fallback_tw(struct io_uring_task *tctx){	/*	 * The task ref both keeps ->task valid and, as __io_uring_free() is	 * only called when the task itself is freed, ensures the tctx (and	 * the queued work) stay around until the drain has run.	 */	get_task_struct(tctx->task);	if (!queue_work(system_dfl_wq, &tctx->fallback_work))		put_task_struct(tctx->task);} /* * Run queued task_work, processing no more than max_entries, with the number * of entries processed added to *count. If more entries than max_entries are * available, the remainder simply stay on the queue for the next run. */void tctx_task_work_run(struct io_uring_task *tctx, unsigned int max_entries,			unsigned int *count){	struct io_ring_ctx *ctx = NULL;	struct io_tw_state ts = { }; 	while (*count < max_entries) {		struct llist_node *node = mpscq_pop(&tctx->task_list,						    &tctx->task_head);		struct io_kiocb *req; 		if (!node) {			if (mpscq_empty(&tctx->task_list))				break;			/*			 * A producer has published a node but hasn't			 * linked it into the queue yet (see mpscq_pop()).			 * Give it a chance to finish rather than spinning,			 * and don't sit on the ctx lock while doing so.			 */			ctx_flush_and_put(ctx, ts);			ctx = NULL;			cond_resched();			continue;		}		req = container_of(node, struct io_kiocb, io_task_work.node);		if (req->ctx != ctx) {			ctx_flush_and_put(ctx, ts);			ctx = req->ctx;			mutex_lock(&ctx->uring_lock);			percpu_ref_get(&ctx->refs);			ts.cancel = io_should_terminate_tw(ctx);		}		INDIRECT_CALL_2(req->io_task_work.func,				io_poll_task_func, io_req_rw_complete,				(struct io_tw_req){req}, ts);		(*count)++;		/*		 * Break if most recent pop emptied the queue. This helps		 * bound task_work run, and also protects the regular		 * task_work addition.		 */		if (mpscq_pop_emptied(&tctx->task_list, tctx->task_head))			break;		if (unlikely(need_resched())) {			ctx_flush_and_put(ctx, ts);			ctx = NULL;			cond_resched();		}	}	ctx_flush_and_put(ctx, ts); 	/*	 * Relaxed read is enough as only the task itself sets ->in_cancel.	 * The tctx may also be drained by io_tctx_fallback_work(), in which	 * case current is a kworker that has no tctx refs to drop.	 */	if (unlikely(atomic_read(&tctx->in_cancel)) &&	    current->io_uring == tctx)		io_uring_drop_tctx_refs(current); 	trace_io_uring_task_work_run(tctx, *count);} void tctx_task_work(struct callback_head *cb){	struct io_uring_task *tctx;	unsigned int count = 0; 	tctx = container_of(cb, struct io_uring_task, task_work);	tctx_task_work_run(tctx, UINT_MAX, &count);} /* * Sets IORING_SQ_TASKRUN in the sq_flags shared with userspace, using the * RCU protected rings pointer to be safe against concurrent ring resizing. */static void io_ctx_mark_taskrun(struct io_ring_ctx *ctx){	lockdep_assert_in_rcu_read_lock(); 	if (ctx->flags & IORING_SETUP_TASKRUN_FLAG) {		struct io_rings *rings = rcu_dereference(ctx->rings_rcu); 		atomic_or(IORING_SQ_TASKRUN, &rings->sq_flags);	}} void io_req_local_work_add(struct io_kiocb *req, unsigned flags){	struct io_ring_ctx *ctx = req->ctx;	int nr_wait; 	/* pairs with synchronize_rcu() in io_ring_exit_work() */	guard(rcu)(); 	/*	 * We don't know how many requests there are in the link and whether	 * they can even be queued lazily, fall back to non-lazy.	 */	if (req->flags & IO_REQ_LINK_FLAGS)		flags &= ~IOU_F_TWQ_LAZY_WAKE; 	/*	 * The xchg() in mpscq_push() implies a full barrier, which pairs with	 * the barrier in set_current_state() on the io_cqring_wait() side. This	 * ensures that either we see the updated ->cq_wait_nr, or waiters going	 * to sleep will observe the work added to the list, which is similar to	 * the wait/wake task state sync.	 */	if (mpscq_push(&ctx->work_list, &req->io_task_work.node)) {		io_ctx_mark_taskrun(ctx);		if (data_race(ctx->int_flags) & IO_RING_F_HAS_EVFD)			io_eventfd_signal(ctx, false, flags & IOU_F_TWQ_IN_WAKE);	} 	/*	 * No one is waiting (IO_CQ_WAKE_INIT), or this cycle's wake up has	 * already been issued (zero or negative, see below).	 */	nr_wait = atomic_read(&ctx->cq_wait_nr);	if (nr_wait <= 0)		return;	if (flags & IOU_F_TWQ_LAZY_WAKE) {		/*		 * ->cq_wait_nr counts down the number of lazy adds, once it		 * hits zero we're good to wake the waiter. A producer that		 * gets delayed between pushing its entry and getting here		 * may count down a later wait cycle. That's OK, it'll be an		 * early wake, not a lost one.		 */		if (!atomic_dec_and_test(&ctx->cq_wait_nr))			return;	} else if (atomic_xchg(&ctx->cq_wait_nr, IO_CQ_WAKE_INIT) <= 0) {		/*		 * Potentially raced with lazy add, claim the wake. A value		 * <= 0 means a lazy add hit zero or another forced add		 * claimed IO_CQ_WAKE_INIT. Either way, the wake up for this		 * wait cycle has already been done.		 */		return;	}	wake_up_state(ctx->submitter_task, TASK_INTERRUPTIBLE);} void io_req_normal_work_add(struct io_kiocb *req){	struct io_uring_task *tctx = req->tctx;	struct io_ring_ctx *ctx = req->ctx; 	/* tw run already pending, nothing else to do */	if (!mpscq_push(&tctx->task_list, &req->io_task_work.node))		return; 	/*	 * Doesn't need to use ->rings_rcu, as resizing isn't supported for	 * !DEFER_TASKRUN.	 */	if (ctx->flags & IORING_SETUP_TASKRUN_FLAG)		atomic_or(IORING_SQ_TASKRUN, &ctx->rings->sq_flags); 	/* SQPOLL doesn't need the task_work added, it'll run it itself */	if (ctx->flags & IORING_SETUP_SQPOLL) {		__set_notify_signal(tctx->task);		return;	} 	if (likely(!task_work_add(tctx->task, &tctx->task_work, ctx->notify_method)))		return; 	io_fallback_tw(tctx);} void io_req_task_work_add_remote(struct io_kiocb *req, unsigned flags){	if (WARN_ON_ONCE(!(req->ctx->flags & IORING_SETUP_DEFER_TASKRUN)))		return;	__io_req_task_work_add(req, flags);} void __cold io_cancel_local_task_work(struct io_ring_ctx *ctx){	struct io_tw_state ts = { .cancel = true };	struct llist_node *node; 	/*	 * The work list consumer side is serialized by ->uring_lock, see	 * __io_run_local_work(). Grab it to guard against racing with normal	 * task_work running, as the task may be exiting. The ring is going	 * away, run the entries in cancel mode right here - the callers	 * provide the same process context the per-ctx fallback work that	 * they were previously punted to ran in.	 */	guard(mutex)(&ctx->uring_lock); 	while (!mpscq_empty(&ctx->work_list)) {		struct io_kiocb *req; 		node = mpscq_pop(&ctx->work_list, &ctx->work_head);		if (!node) {			/* a producer is mid-push, wait for it to link */			cond_resched();			continue;		}		req = container_of(node, struct io_kiocb, io_task_work.node);		req->io_task_work.func((struct io_tw_req){req}, ts);	}	io_submit_flush_completions(ctx);} static bool io_run_local_work_continue(struct io_ring_ctx *ctx, int events,				       int min_events){	if (!io_local_work_pending(ctx))		return false;	if (events < min_events)		return true;	if (ctx->flags & IORING_SETUP_TASKRUN_FLAG)		atomic_or(IORING_SQ_TASKRUN, &ctx->rings->sq_flags);	return false;} static int __io_run_local_work_loop(struct io_ring_ctx *ctx,				    io_tw_token_t tw,				    int events){	int ret = 0; 	while (ret < events) {		struct llist_node *node = mpscq_pop(&ctx->work_list, &ctx->work_head);		struct io_kiocb *req; 		if (!node)			break;		req = container_of(node, struct io_kiocb, io_task_work.node);		INDIRECT_CALL_2(req->io_task_work.func,				io_poll_task_func, io_req_rw_complete,				(struct io_tw_req){req}, tw);		ret++;	} 	return ret;} static int __io_run_local_work(struct io_ring_ctx *ctx, io_tw_token_t tw,			       int min_events, int max_events){	unsigned int loops = 0;	int ret = 0; 	if (WARN_ON_ONCE(ctx->submitter_task != current))		return -EEXIST;	if (ctx->flags & IORING_SETUP_TASKRUN_FLAG)		atomic_andnot(IORING_SQ_TASKRUN, &ctx->rings->sq_flags);again:	/*	 * If the last loop made no progress while work is still pending,	 * a producer has published a node but hasn't linked it into the	 * queue yet (see mpscq_pop()). Give it a chance to finish rather	 * than spinning on the queue.	 */	if (unlikely(loops && !ret))		cond_resched();	tw.cancel = io_should_terminate_tw(ctx);	min_events -= ret;	ret = __io_run_local_work_loop(ctx, tw, max_events);	loops++; 	if (io_run_local_work_continue(ctx, ret, min_events))		goto again;	io_submit_flush_completions(ctx);	if (io_run_local_work_continue(ctx, ret, min_events))		goto again; 	trace_io_uring_local_work_run(ctx, ret, loops);	return ret;} int io_run_local_work_locked(struct io_ring_ctx *ctx, int min_events){	struct io_tw_state ts = {}; 	if (!io_local_work_pending(ctx))		return 0;	return __io_run_local_work(ctx, ts, min_events,					max(IO_LOCAL_TW_DEFAULT_MAX, min_events));} int io_run_local_work(struct io_ring_ctx *ctx, int min_events, int max_events){	struct io_tw_state ts = {};	int ret; 	mutex_lock(&ctx->uring_lock);	ret = __io_run_local_work(ctx, ts, min_events, max_events);	mutex_unlock(&ctx->uring_lock);	return ret;}