[PATCH] io_uring: add support for absolute timeouts

[Jens Axboe <axboe@xxxxxxxxx>]

This is a pretty trivial addition on top of the relative timeouts
we have now, but it's handy for ensuring tighter timing for those
that are building scheduling primitives on top of io_uring.

Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
---
 fs/io_uring.c                 | 17 ++++++++++++-----
 include/uapi/linux/io_uring.h |  5 +++++
 2 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index d92a34707afb..e48e0854bc1e 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1937,12 +1937,16 @@ static int io_timeout(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 	unsigned count, req_dist, tail_index;
 	struct io_ring_ctx *ctx = req->ctx;
 	struct list_head *entry;
+	enum hrtimer_mode mode;
 	struct timespec64 ts;
+	unsigned flags;
 
 	if (unlikely(ctx->flags & IORING_SETUP_IOPOLL))
 		return -EINVAL;
-	if (sqe->flags || sqe->ioprio || sqe->buf_index || sqe->timeout_flags ||
-	    sqe->len != 1)
+	if (sqe->flags || sqe->ioprio || sqe->buf_index || sqe->len != 1)
+		return -EINVAL;
+	flags = READ_ONCE(sqe->timeout_flags);
+	if (flags & ~IORING_TIMEOUT_ABS)
 		return -EINVAL;
 
 	if (get_timespec64(&ts, u64_to_user_ptr(sqe->addr)))
@@ -1977,10 +1981,13 @@ static int io_timeout(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 	list_add(&req->list, entry);
 	spin_unlock_irq(&ctx->completion_lock);
 
-	hrtimer_init(&req->timeout.timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+	if (flags & IORING_TIMEOUT_ABS)
+		mode = HRTIMER_MODE_ABS;
+	else
+		mode = HRTIMER_MODE_REL;
+	hrtimer_init(&req->timeout.timer, CLOCK_MONOTONIC, mode);
 	req->timeout.timer.function = io_timeout_fn;
-	hrtimer_start(&req->timeout.timer, timespec64_to_ktime(ts),
-			HRTIMER_MODE_REL);
+	hrtimer_start(&req->timeout.timer, timespec64_to_ktime(ts), mode);
 	return 0;
 }
 
diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index e0137ea6ad79..b402dfee5e15 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -70,6 +70,11 @@ struct io_uring_sqe {
  */
 #define IORING_FSYNC_DATASYNC	(1U << 0)
 
+/*
+ * sqe->timeout_flags
+ */
+#define IORING_TIMEOUT_ABS	(1U << 0)
+
 /*
  * IO completion data structure (Completion Queue Entry)
  */
-- 
2.17.1

-- 
Jens Axboe