Add a `Descriptor` type that allows callers to asynchronously wait for
the descriptor to become readable or writable. This is meant to be a
temporary solution so that we slowly convert code over to async rather
than having to do it all at once.
BUG=b:195468578
TEST=unit tests
Change-Id: Ib3ccefe09c25e222afe872d4e6d076e1e3b57b39
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/3329741
Reviewed-by: Daniel Verkamp <dverkamp@chromium.org>
Tested-by: kokoro <noreply+kokoro@google.com>
Commit-Queue: Chirantan Ekbote <chirantan@chromium.org>
Rather than exposing fallocate directly, add separate functions for each
of the high level operations. This should make it easier to add
cross-platform support as well as avoid the need to force callers to
deal with libc flags.
BUG=b:195468578
TEST=unit tests
Change-Id: I2aa6affa5cd87b299065b83bfc9bd400565308b2
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/3276119
Reviewed-by: Daniel Verkamp <dverkamp@chromium.org>
Tested-by: kokoro <noreply+kokoro@google.com>
Commit-Queue: Chirantan Ekbote <chirantan@chromium.org>
Based on the previous proposal in [1].
* The Executor is now completely platform-agnostic and only relies on
the platform to provide a type that implements the `PlatformState`
trait.
* The crate provides concrete high-level types rather than forcing users
to deal with trait objects and async-trait. Currently, only File and
Event are supported. Support for timers, sockets, and pipes will be
added in subsequent changes.
* Each high-level type delegates the implementation to a
platform-specific type and exists mainly as a place to hold
documentation and tests.
* On Unix the io_driver module provides async versions of various
IO-related syscalls, which are used by the platform-specific File and
Event types to implement the required behavior.
* io-uring support can be disabled at compile time. When uring support
is enabled, we make a runtime check to decide whether or not to use
it. The actual io-uring driver is currently unimplemented and will be
added in a subsequent change.
One non-trivial downside of this change is that the futures returned by
the various async methods are !Send and !Sync, which means that they can
only be awaited from the same thread on which they were started. In
practice this should be fine since current crosvm (and Chrome OS) code
doesn't really make use of sending futures to different threads. This
can also be mitigated by using `Executor::spawn_local` and a
`oneshot::channel` to isolate the !Send future from the outer async
fn (as long as the output of the future is Send). See the crate
documentation and the `outer_future_is_send` test in `src/executor.rs`
for more details.
[1]: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/3062166
BUG=b:195468578
TEST=unit tests
Change-Id: I1aad0885e67a957149e2ec3b4d9df215d9b20d81
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/3222223
Reviewed-by: Daniel Verkamp <dverkamp@chromium.org>
Tested-by: kokoro <noreply+kokoro@google.com>
Commit-Queue: Chirantan Ekbote <chirantan@chromium.org>
