From ac90f249e15cd2a850daa9e36e15f81ce1ff6550 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Fri, 6 Sep 2019 10:26:21 -0600 Subject: io_uring: expose single mmap capability After commit 75b28affdd6a we can get by with just a single mmap to map both the sq and cq ring. However, userspace doesn't know that. Add a features variable to io_uring_params, and notify userspace that the kernel has this ability. This can then be used in liburing (or in applications directly) to avoid the second mmap. Signed-off-by: Jens Axboe --- fs/io_uring.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'fs') diff --git a/fs/io_uring.c b/fs/io_uring.c index 17dfe57c57f8..be24596e90d7 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -3391,6 +3391,8 @@ static int io_uring_create(unsigned entries, struct io_uring_params *p) p->cq_off.ring_entries = offsetof(struct io_rings, cq_ring_entries); p->cq_off.overflow = offsetof(struct io_rings, cq_overflow); p->cq_off.cqes = offsetof(struct io_rings, cqes); + + p->features = IORING_FEAT_SINGLE_MMAP; return ret; err: io_ring_ctx_wait_and_kill(ctx); -- cgit v1.2.3