From c261e4f1dd29fabab54b325bc1da8769a3998be1 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Thu, 19 Dec 2024 09:32:26 -0700 Subject: [PATCH] io_uring/register: limit ring resizing to DEFER_TASKRUN With DEFER_TASKRUN, we know the ring can't be both waited upon and resized at the same time. This is important for CQ resizing. Allowing SQ ring resizing is more trivial, but isn't the interesting use case. Hence limit ring resizing in general to DEFER_TASKRUN only for now. This isn't a huge problem as CQ ring resizing is generally the most useful on networking type of workloads where it can be hard to size the ring appropriately upfront, and those should be using DEFER_TASKRUN for better performance. Fixes: 79cfe9e59c2a ("io_uring/register: add IORING_REGISTER_RESIZE_RINGS") Signed-off-by: Jens Axboe --- io_uring/register.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/io_uring/register.c b/io_uring/register.c index 1e99c783abdf..fdd44914c39c 100644 --- a/io_uring/register.c +++ b/io_uring/register.c @@ -414,6 +414,9 @@ static int io_register_resize_rings(struct io_ring_ctx *ctx, void __user *arg) if (ctx->flags & IORING_SETUP_SINGLE_ISSUER && current != ctx->submitter_task) return -EEXIST; + /* limited to DEFER_TASKRUN for now */ + if (!(ctx->flags & IORING_SETUP_DEFER_TASKRUN)) + return -EINVAL; if (copy_from_user(&p, arg, sizeof(p))) return -EFAULT; if (p.flags & ~RESIZE_FLAGS)