Commit 773697b6 authored by Pavel Begunkov's avatar Pavel Begunkov Committed by Jens Axboe
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io_uring: pre-calculate syscall iopolling decision 



Syscall should only iopoll for events when it's a IOPOLL ring and is not
SQPOLL. Instead of check both flags every time we can save it in ring
flags so it's easier to use. We don't care much about an extra if there,
however it will be inconvenient to copy-paste this chunk with checks in
future patches.

Signed-off-by: default avatarPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/7fd2f8fc2606305aa06dd8c0ff8f76a66b39c383.1647957378.git.asml.silence@gmail.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent f81440d3

fs/io_uring.c

+13 −8
Original line number Diff line number Diff line
@@ -356,6 +356,7 @@ struct io_ring_ctx { 
		unsigned int		drain_active: 1;

		unsigned int		drain_disabled: 1;

		unsigned int		has_evfd: 1;

		unsigned int		syscall_iopoll: 1;

	} ____cacheline_aligned_in_smp;



	/* submission data */
@@ -10829,14 +10830,7 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit, 
	if (flags & IORING_ENTER_GETEVENTS) {

		min_complete = min(min_complete, ctx->cq_entries);



		/*

		 * When SETUP_IOPOLL and SETUP_SQPOLL are both enabled, user

		 * space applications don't need to do io completion events

		 * polling again, they can rely on io_sq_thread to do polling

		 * work, which can reduce cpu usage and uring_lock contention.

		 */

		if (ctx->flags & IORING_SETUP_IOPOLL &&

		    !(ctx->flags & IORING_SETUP_SQPOLL)) {

		if (ctx->syscall_iopoll) {

			ret = io_validate_ext_arg(flags, argp, argsz);

			if (unlikely(ret))

				goto out;
@@ -11174,6 +11168,17 @@ static __cold int io_uring_create(unsigned entries, struct io_uring_params *p, 
	ctx = io_ring_ctx_alloc(p);

	if (!ctx)

		return -ENOMEM;



	/*

	 * When SETUP_IOPOLL and SETUP_SQPOLL are both enabled, user

	 * space applications don't need to do io completion events

	 * polling again, they can rely on io_sq_thread to do polling

	 * work, which can reduce cpu usage and uring_lock contention.

	 */

	if (ctx->flags & IORING_SETUP_IOPOLL &&

	    !(ctx->flags & IORING_SETUP_SQPOLL))

		ctx->syscall_iopoll = 1;



	ctx->compat = in_compat_syscall();

	if (!capable(CAP_IPC_LOCK))

		ctx->user = get_uid(current_user());