io: use io_uring for all io

There should no longer be any

- read
- write
- connect
- sendmsg
- recvmsg
- accept

calls in the codebase. Previously we were using a mix of io_uring and
these calls which had some negative effects: Since we were using the old
system calls, we had to set the file descriptors to non-blocking. But
our io_uring code did not handle EAGAIN. This lead to programs sometimes
being killed when the wayland IO was actually blocking.

Now all file descriptors are set to blocking, but io_uring makes it
non-blocking from our perspective. The one exception are evdev files
because they are read via libinput and libinput uses the old system
calls.

src/io_uring/ops/read_write.rs

@@ -0,0 +1,102 @@
+use {
+    crate::{
+        io_uring::{
+            pending_result::PendingResult,
+            sys::{io_uring_sqe, IORING_OP_READ, IORING_OP_WRITE},
+            IoUring, IoUringData, IoUringError, Task, TaskResultExt,
+        },
+        time::Time,
+        utils::buf::Buf,
+    },
+    std::rc::Rc,
+    uapi::{c, OwnedFd},
+};
+
+impl IoUring {
+    pub async fn read(&self, fd: &Rc<OwnedFd>, buf: Buf) -> Result<usize, IoUringError> {
+        self.perform(fd, buf, None, IORING_OP_READ).await
+    }
+
+    pub async fn write(
+        &self,
+        fd: &Rc<OwnedFd>,
+        buf: Buf,
+        timeout: Option<Time>,
+    ) -> Result<usize, IoUringError> {
+        self.perform(fd, buf, timeout, IORING_OP_WRITE).await
+    }
+
+    async fn perform(
+        &self,
+        fd: &Rc<OwnedFd>,
+        buf: Buf,
+        timeout: Option<Time>,
+        opcode: u8,
+    ) -> Result<usize, IoUringError> {
+        self.ring.check_destroyed()?;
+        let id = self.ring.id();
+        let pr = self.ring.pending_results.acquire();
+        {
+            let mut pw = self.ring.cached_read_writes.pop().unwrap_or_default();
+            pw.opcode = opcode;
+            pw.id = id.id;
+            pw.has_timeout = timeout.is_some();
+            pw.fd = fd.raw();
+            pw.buf = buf.as_ptr() as _;
+            pw.len = buf.len();
+            pw.data = Some(ReadWriteTaskData {
+                _fd: fd.clone(),
+                _buf: buf,
+                res: pr.clone(),
+            });
+            self.ring.schedule(pw);
+            if let Some(time) = timeout {
+                self.schedule_timeout(time);
+            }
+        }
+        Ok(pr.await.map(|v| v as usize)).merge()
+    }
+}
+
+struct ReadWriteTaskData {
+    _fd: Rc<OwnedFd>,
+    _buf: Buf,
+    res: PendingResult,
+}
+
+#[derive(Default)]
+pub struct ReadWriteTask {
+    id: u64,
+    has_timeout: bool,
+    fd: c::c_int,
+    buf: usize,
+    len: usize,
+    data: Option<ReadWriteTaskData>,
+    opcode: u8,
+}
+
+unsafe impl Task for ReadWriteTask {
+    fn id(&self) -> u64 {
+        self.id
+    }
+
+    fn complete(mut self: Box<Self>, ring: &IoUringData, res: i32) {
+        if let Some(data) = self.data.take() {
+            data.res.complete(res);
+        }
+        ring.cached_read_writes.push(self);
+    }
+
+    fn encode(&self, sqe: &mut io_uring_sqe) {
+        sqe.opcode = self.opcode;
+        sqe.fd = self.fd as _;
+        sqe.u1.off = !0;
+        sqe.u2.addr = self.buf as _;
+        sqe.u3.rw_flags = 0;
+        sqe.len = self.len as _;
+    }
+
+    fn has_timeout(&self) -> bool {
+        self.has_timeout
+    }
+}