runtime: disable io-uring on EPERM

[mox692]

Motivation

Closes #7691.

Solution

If we get EPERM at the initial io-uring syscall (io_uring_setup), then we set the Unsupported flag internally, which disables subsequent io-uring operations.

[martin-g]

LGTM!

I only wish there was an info log to tell me that uring is disabled for some reason.

[ADD-SP]

How to write tests for this fix? To make our testset self-contained, the crate libseccomp might be a good candidate. However, the libseccomp requires us to install the libseccomp.so on the system, it is a bit annoying for developer to run tests locally.

One possible solution is gating the test using special cfg and only apply this cfg on CI.

[ADD-SP]

Another alternative for testing is https://docs.rs/seccompiler/0.5.0/seccompiler/.

[Darksonn]

Testing this in CI sounds difficult, but can we perform a manual test?

[ADD-SP]

We can open another PR for testing if possible.

[ADD-SP]

Tested locally — this fix works as expected.

docker run --rm rust:latest bash -c "$(cat <<"EOF"
mkdir -p /tmp/test/src
cd /tmp/test
ln -s Cargo.toml a.toml

cat <<"EOF2" > Cargo.toml
[package]
edition = "2024"
name = "tokio-io-uring-symlink"

[dependencies]
tokio = { git = "https://github.com/tokio-rs/tokio.git", rev = "7f959e1049c8d252f4a1e18bbbabc94cfd91120d", features = ["full", "io-uring"] }
EOF2

cat <<"EOF2" > src/main.rs
#[tokio::main]
async fn main() {
    tokio::fs::File::open("a.toml").await.unwrap();
}
EOF2

RUSTFLAGS='--cfg tokio_unstable' cargo run
EOF
)"