io_uring: add timeout support for io_uring_enter()

Now users who want to get woken when waiting for events should submit a
timeout command first. It is not safe for applications that split SQ and
CQ handling between two threads, such as mysql. Users should synchronize
the two threads explicitly to protect SQ and that will impact the
performance.

This patch adds support for timeout to existing io_uring_enter(). To
avoid overloading arguments, it introduces a new parameter structure
which contains sigmask and timeout.

I have tested the workloads with one thread submiting nop requests
while the other reaping the cqe with timeout. It shows 1.8~2x faster
when the iodepth is 16.

Signed-off-by: Jiufei Xue <jiufei.xue@linux.alibaba.com>
Signed-off-by: Hao Xu <haoxu@linux.alibaba.com>
[axboe: various cleanups/fixes, and name change to SIG_IS_DATA]
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 62 insertions, 7 deletions

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 11ce97d6259c..ee25c70527aa 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -7118,7 +7118,8 @@ static int io_run_task_work_sig(void)
  * application must reap them itself, as they reside on the shared cq ring.
  */
 static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events,
-			  const sigset_t __user *sig, size_t sigsz)
+			  const sigset_t __user *sig, size_t sigsz,
+			  struct __kernel_timespec __user *uts)
 {
 	struct io_wait_queue iowq = {
 		.wq = {
@@ -7130,6 +7131,8 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events,
 		.to_wait	= min_events,
 	};
 	struct io_rings *rings = ctx->rings;
+	struct timespec64 ts;
+	signed long timeout = 0;
 	int ret = 0;
 
 	do {
@@ -7152,6 +7155,12 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events,
 			return ret;
 	}
 
+	if (uts) {
+		if (get_timespec64(&ts, uts))
+			return -EFAULT;
+		timeout = timespec64_to_jiffies(&ts);
+	}
+
 	iowq.nr_timeouts = atomic_read(&ctx->cq_timeouts);
 	trace_io_uring_cqring_wait(ctx, min_events);
 	do {
@@ -7165,7 +7174,15 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events,
 			break;
 		if (io_should_wake(&iowq, false))
 			break;
-		schedule();
+		if (uts) {
+			timeout = schedule_timeout(timeout);
+			if (timeout == 0) {
+				ret = -ETIME;
+				break;
+			}
+		} else {
+			schedule();
+		}
 	} while (1);
 	finish_wait(&ctx->wait, &iowq.wq);
 
@@ -9167,9 +9184,39 @@ static void io_sqpoll_wait_sq(struct io_ring_ctx *ctx)
 	finish_wait(&ctx->sqo_sq_wait, &wait);
 }
 
+static int io_get_ext_arg(unsigned flags, const void __user *argp, size_t *argsz,
+			  struct __kernel_timespec __user **ts,
+			  const sigset_t __user **sig)
+{
+	struct io_uring_getevents_arg arg;
+
+	/*
+	 * If EXT_ARG isn't set, then we have no timespec and the argp pointer
+	 * is just a pointer to the sigset_t.
+	 */
+	if (!(flags & IORING_ENTER_EXT_ARG)) {
+		*sig = (const sigset_t __user *) argp;
+		*ts = NULL;
+		return 0;
+	}
+
+	/*
+	 * EXT_ARG is set - ensure we agree on the size of it and copy in our
+	 * timespec and sigset_t pointers if good.
+	 */
+	if (*argsz != sizeof(arg))
+		return -EINVAL;
+	if (copy_from_user(&arg, argp, sizeof(arg)))
+		return -EFAULT;
+	*sig = u64_to_user_ptr(arg.sigmask);
+	*argsz = arg.sigmask_sz;
+	*ts = u64_to_user_ptr(arg.ts);
+	return 0;
+}
+
 SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
-		u32, min_complete, u32, flags, const sigset_t __user *, sig,
-		size_t, sigsz)
+		u32, min_complete, u32, flags, const void __user *, argp,
+		size_t, argsz)
 {
 	struct io_ring_ctx *ctx;
 	long ret = -EBADF;
@@ -9179,7 +9226,7 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
 	io_run_task_work();
 
 	if (flags & ~(IORING_ENTER_GETEVENTS | IORING_ENTER_SQ_WAKEUP |
-			IORING_ENTER_SQ_WAIT))
+			IORING_ENTER_SQ_WAIT | IORING_ENTER_EXT_ARG))
 		return -EINVAL;
 
 	f = fdget(fd);
@@ -9225,6 +9272,13 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
 			goto out;
 	}
 	if (flags & IORING_ENTER_GETEVENTS) {
+		const sigset_t __user *sig;
+		struct __kernel_timespec __user *ts;
+
+		ret = io_get_ext_arg(flags, argp, &argsz, &ts, &sig);
+		if (unlikely(ret))
+			goto out;
+
 		min_complete = min(min_complete, ctx->cq_entries);
 
 		/*
@@ -9237,7 +9291,7 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
 		    !(ctx->flags & IORING_SETUP_SQPOLL)) {
 			ret = io_iopoll_check(ctx, min_complete);
 		} else {
-			ret = io_cqring_wait(ctx, min_complete, sig, sigsz);
+			ret = io_cqring_wait(ctx, min_complete, sig, argsz, ts);
 		}
 	}
 
@@ -9600,7 +9654,8 @@ static int io_uring_create(unsigned entries, struct io_uring_params *p,
 	p->features = IORING_FEAT_SINGLE_MMAP | IORING_FEAT_NODROP |
 			IORING_FEAT_SUBMIT_STABLE | IORING_FEAT_RW_CUR_POS |
 			IORING_FEAT_CUR_PERSONALITY | IORING_FEAT_FAST_POLL |
-			IORING_FEAT_POLL_32BITS | IORING_FEAT_SQPOLL_NONFIXED;
+			IORING_FEAT_POLL_32BITS | IORING_FEAT_SQPOLL_NONFIXED |
+			IORING_FEAT_EXT_ARG;
 
 	if (copy_to_user(params, p, sizeof(*p))) {
 		ret = -EFAULT;