From 086e6a0f0c614fc619f3ef35dee34fa304963404 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Sun, 10 Nov 2019 16:56:04 -0700 Subject: [PATCH] io_uring: flag SQPOLL busy condition to userspace commit c1edbf5f081be9fbbea68c1d564b773e59c1acf3 upstream. Now that we have backpressure, for SQPOLL, we have one more condition that warrants flagging that the application needs to enter the kernel: we failed to submit IO due to backpressure. Make sure we catch that and flag it appropriately. If we run into backpressure issues with the SQPOLL thread, flag it as such to the application by setting IORING_SQ_NEED_WAKEUP. This will cause the application to enter the kernel, and that will flush the backlog and clear the condition. Signed-off-by: Jens Axboe Signed-off-by: Joseph Qi Reviewed-by: Xiaoguang Wang --- fs/io_uring.c | 22 ++++++++++++++++------ 1 file changed, 16 insertions(+), 6 deletions(-) diff --git a/fs/io_uring.c b/fs/io_uring.c index f6c5446a79f3..b7b4a0a13eab 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -3118,16 +3118,16 @@ static int io_sq_thread(void *data) DEFINE_WAIT(wait); unsigned inflight; unsigned long timeout; + int ret; complete(&ctx->completions[1]); old_fs = get_fs(); set_fs(USER_DS); - timeout = inflight = 0; + ret = timeout = inflight = 0; while (!kthread_should_park()) { unsigned int to_submit; - int ret; if (inflight) { unsigned nr_events = 0; @@ -3161,13 +3161,21 @@ static int io_sq_thread(void *data) } to_submit = io_sqring_entries(ctx); - if (!to_submit) { + + /* + * If submit got -EBUSY, flag us as needing the application + * to enter the kernel to reap and flush events. + */ + if (!to_submit || ret == -EBUSY) { /* * We're polling. If we're within the defined idle * period, then let us spin without work before going - * to sleep. + * to sleep. The exception is if we got EBUSY doing + * more IO, we should wait for the application to + * reap events and wake us up. */ - if (inflight || !time_after(jiffies, timeout)) { + if (inflight || + (!time_after(jiffies, timeout) && ret != -EBUSY)) { cond_resched(); continue; } @@ -3193,7 +3201,7 @@ static int io_sq_thread(void *data) smp_mb(); to_submit = io_sqring_entries(ctx); - if (!to_submit) { + if (!to_submit || ret == -EBUSY) { if (kthread_should_park()) { finish_wait(&ctx->sqo_wait, &wait); break; @@ -4352,6 +4360,8 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit, */ ret = 0; if (ctx->flags & IORING_SETUP_SQPOLL) { + if (!list_empty_careful(&ctx->cq_overflow_list)) + io_cqring_overflow_flush(ctx, false); if (flags & IORING_ENTER_SQ_WAKEUP) wake_up(&ctx->sqo_wait); submitted = to_submit; -- GitLab