From: Jens Axboe axboe@kernel.dk
mainline inclusion from mainline-5.5-rc1 commit c1edbf5f081be9fbbea68c1d564b773e59c1acf3 category: feature bugzilla: https://bugzilla.openeuler.org/show_bug.cgi?id=27 CVE: NA ---------------------------
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 axboe@kernel.dk Signed-off-by: Zhihao Cheng chengzhihao1@huawei.com Signed-off-by: yangerkun yangerkun@huawei.com Reviewed-by: zhangyi (F) yi.zhang@huawei.com Signed-off-by: Cheng Jian cj.chengjian@huawei.com --- 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 645939e864db..85c21fee7ac0 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;