From ca0a26511c679a797f86589894a4523db36d833e Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Thu, 4 Mar 2021 17:15:48 -0700 Subject: [PATCH] io_uring: don't keep looping for more events if we can't flush overflow It doesn't make sense to wait for more events to come in, if we can't even flush the overflow we already have to the ring. Return -EBUSY for that condition, just like we do for attempts to submit with overflow pending. Cc: stable@vger.kernel.org # 5.11 Signed-off-by: Jens Axboe --- fs/io_uring.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) diff --git a/fs/io_uring.c b/fs/io_uring.c index 76e243c..0441701 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -1451,18 +1451,22 @@ static bool __io_cqring_overflow_flush(struct io_ring_ctx *ctx, bool force, return all_flushed; } -static void io_cqring_overflow_flush(struct io_ring_ctx *ctx, bool force, +static bool io_cqring_overflow_flush(struct io_ring_ctx *ctx, bool force, struct task_struct *tsk, struct files_struct *files) { + bool ret = true; + if (test_bit(0, &ctx->cq_check_overflow)) { /* iopoll syncs against uring_lock, not completion_lock */ if (ctx->flags & IORING_SETUP_IOPOLL) mutex_lock(&ctx->uring_lock); - __io_cqring_overflow_flush(ctx, force, tsk, files); + ret = __io_cqring_overflow_flush(ctx, force, tsk, files); if (ctx->flags & IORING_SETUP_IOPOLL) mutex_unlock(&ctx->uring_lock); } + + return ret; } static void __io_cqring_fill_event(struct io_kiocb *req, long res, long cflags) @@ -6883,11 +6887,16 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events, iowq.nr_timeouts = atomic_read(&ctx->cq_timeouts); trace_io_uring_cqring_wait(ctx, min_events); do { - io_cqring_overflow_flush(ctx, false, NULL, NULL); + /* if we can't even flush overflow, don't wait for more */ + if (!io_cqring_overflow_flush(ctx, false, NULL, NULL)) { + ret = -EBUSY; + break; + } prepare_to_wait_exclusive(&ctx->wait, &iowq.wq, TASK_INTERRUPTIBLE); ret = io_cqring_wait_schedule(ctx, &iowq, &timeout); finish_wait(&ctx->wait, &iowq.wq); + cond_resched(); } while (ret > 0); restore_saved_sigmask_unless(ret == -EINTR); -- 2.7.4