11:07 a.m.
From: Eric Blake <eblake(a)redhat.com>
CI shows our async handle fails to build on FreeBSD and MacOS (where
epoll() is not available as a syscall, and therefore not available as
a Rust crate). We can instead accomplish the same level-probing
effects by doing a zero-timeout poll with mio (which defers under the
hood to epoll on Linux, and kqueue on BSD).
Fixes: 223a9965 ("rust: async: Create an async friendly handle type")
CC: Tage Johansson <tage.j.lists(a)posteo.net>
Signed-off-by: Eric Blake <eblake(a)redhat.com>
---
rust/Cargo.toml | 3 ++-
rust/src/async_handle.rs | 40 +++++++++++++++++++++++-----------------
2 files changed, 25 insertions(+), 18 deletions(-)
diff --git a/rust/Cargo.toml b/rust/Cargo.toml
index 0879b34..678848a 100644
--- a/rust/Cargo.toml
+++ b/rust/Cargo.toml
@@ -49,9 +49,10 @@ thiserror = "1.0.40"
log = { version = "0.4.19", optional = true }
libc = "0.2.147"
tokio = { optional = true, version = "1.29.1", default-features = false,
features = ["rt", "sync", "net"] }
-epoll = "4.3.3"
+mio = { optional = true, version = "0.8.0" }
[features]
+tokio = ["dep:tokio", "dep:mio"]
default = ["log", "tokio"]
[dev-dependencies]
diff --git a/rust/src/async_handle.rs b/rust/src/async_handle.rs
index 6793ce9..8f3e8df 100644
--- a/rust/src/async_handle.rs
+++ b/rust/src/async_handle.rs
@@ -35,9 +35,11 @@ use crate::sys;
use crate::Handle;
use crate::{Error, FatalErrorKind, Result};
use crate::{AIO_DIRECTION_BOTH, AIO_DIRECTION_READ, AIO_DIRECTION_WRITE};
-use epoll::Events;
+use mio::unix::SourceFd;
+use mio::{Events, Interest as MioInterest, Poll, Token};
use std::sync::Arc;
use std::sync::Mutex;
+use std::time::Duration;
use tokio::io::{unix::AsyncFd, Interest, Ready as IoReady};
use tokio::sync::Notify;
use tokio::task;
@@ -176,13 +178,8 @@ async fn polling_task(handle_data: &HandleData) ->
Result<(), FatalErrorKind> {
} = handle_data;
let fd = handle.aio_get_fd().map_err(Error::to_fatal)?;
let tokio_fd = AsyncFd::new(fd)?;
- let epfd = epoll::create(false)?;
- epoll::ctl(
- epfd,
- epoll::ControlOptions::EPOLL_CTL_ADD,
- fd,
- epoll::Event::new(Events::EPOLLIN | Events::EPOLLOUT, 42),
- )?;
+ let mut events = Events::with_capacity(1);
+ let mut poll = Poll::new()?;
// The following loop does approximately the following things:
//
@@ -248,19 +245,28 @@ async fn polling_task(handle_data: &HandleData) ->
Result<(), FatalErrorKind> {
}
drop(pending_cmds_lock);
- // Use epoll to check the current read/write availability on the fd.
+ // Use mio poll to check the current read/write availability on the fd.
// This is needed because Tokio supports only edge-triggered
// notifications but Libnbd requires level-triggered notifications.
- let mut revent = epoll::Event { data: 0, events: 0 };
// Setting timeout to 0 means that it will return immediately.
- epoll::wait(epfd, 0, std::slice::from_mut(&mut revent))?;
- let revents = Events::from_bits(revent.events).unwrap();
- if !revents.contains(Events::EPOLLIN) {
- ready_guard.clear_ready_matching(IoReady::READABLE);
- }
- if !revents.contains(Events::EPOLLOUT) {
- ready_guard.clear_ready_matching(IoReady::WRITABLE);
+ // mio states that it is OS-dependent on whether a single event
+ // can be both readable and writable, but we survive just fine
+ // if we only see one direction even when both are available.
+ poll.registry().register(
+ &mut SourceFd(&fd),
+ Token(0),
+ MioInterest::READABLE | MioInterest::WRITABLE,
+ )?;
+ poll.poll(&mut events, Some(Duration::ZERO))?;
+ for event in &events {
+ if !event.is_readable() {
+ ready_guard.clear_ready_matching(IoReady::READABLE);
+ }
+ if !event.is_writable() {
+ ready_guard.clear_ready_matching(IoReady::WRITABLE);
+ }
}
ready_guard.retain_ready();
+ poll.registry().deregister(&mut SourceFd(&fd))?;
}
}
base-commit: 9afb980d05d6144129c899285e44779757a380e8
prerequisite-patch-id: 8d1779610795021ed5a3d0973ddf9ef854cd6a24
prerequisite-patch-id: 1f0f333311f11ac9b1ff0be08f5aa0a9904ba4de
prerequisite-patch-id: dc4af7343c57a4f99dc82918c07470030e542747
prerequisite-patch-id: 8e8f7a043c80d6c24e883967f5bd952a64db1228
prerequisite-patch-id: ba7b3482e2e16f76b5f285daeeda30b31a841912
prerequisite-patch-id: 219a9595e550a8caf43d466dcb2b044114e1b7bf
prerequisite-patch-id: 3de46c9673221bff1d897970aa983b3f8e6cab74
prerequisite-patch-id: 4235d5e174fce05b9a947b3b838bebf968f0fa6a
prerequisite-patch-id: 07773355d5718e0593c4030a8f035fc11fea3715
prerequisite-patch-id: f023deea8b706706e3c2980403064d90a254af3c
prerequisite-patch-id: dd415a31fa127d90bcc7d993a2659e39d7d4cae8
prerequisite-patch-id: 618cc5f574207f36818ef803f2e586314c2458f5
prerequisite-patch-id: 8639c6cc4fec58f4761771c5d8a9476d538c6251
prerequisite-patch-id: 9bc660aed54a6266b014993ff0f388a26ac2982a
prerequisite-patch-id: a334eeb471214d13ea2f47604b0a5b6d86b869b6
--
2.42.0