sys_util: Refactor IntoIovec

The original stated purpose of this trait was to reduce memory
allocations but having the `into_iovec` method return a Vec kind of
defeats that purpose.

Refactor the trait so that it can either convert a T into an iovec or
convert a &[T] into a &[iovec].  Implement the trait for VolatileSlice,
IoSlice, and IoSliceMut and update all the callers.

BUG=none
TEST=unit tests

Cq-Depend: chromium:2210272
Change-Id: I9d0d617a23030d241d50411f4a5a16e7cba4bcee
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/2208527
Reviewed-by: Daniel Verkamp <dverkamp@chromium.org>
Reviewed-by: Zach Reizner <zachr@chromium.org>
Commit-Queue: Chirantan Ekbote <chirantan@chromium.org>
Tested-by: Chirantan Ekbote <chirantan@chromium.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/src/plugin/process.rs b/src/plugin/process.rs
index 783239a..688aa85 100644
--- a/src/plugin/process.rs
+++ b/src/plugin/process.rs
@@ -5,7 +5,7 @@
 use std::collections::hash_map::{Entry, HashMap, VacantEntry};
 use std::env::set_var;
 use std::fs::File;
-use std::io::Write;
+use std::io::{IoSlice, Write};
 use std::mem::transmute;
 use std::os::unix::io::{IntoRawFd, RawFd};
 use std::os::unix::net::UnixDatagram;
@@ -730,7 +730,7 @@ impl Process {
             .map_err(Error::EncodeResponse)?;
         assert_ne!(self.response_buffer.len(), 0);
         self.request_sockets[index]
-            .send_with_fds(&self.response_buffer[..], &response_fds)
+            .send_with_fds(&[IoSlice::new(&self.response_buffer[..])], &response_fds)
             .map_err(Error::PluginSocketSend)?;
 
         Ok(())