[PATCH] io_uring: add support for absolute timeouts

[Jens Axboe]

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 <ax...@kernel.dk>
---
 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