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/crosvm_plugin/src/lib.rs b/crosvm_plugin/src/lib.rs
index 05c19bf..e9d135c 100644
--- a/crosvm_plugin/src/lib.rs
+++ b/crosvm_plugin/src/lib.rs
@@ -17,7 +17,7 @@
 
 use std::env;
 use std::fs::File;
-use std::io::{Read, Write};
+use std::io::{IoSlice, Read, Write};
 use std::mem::{size_of, swap};
 use std::os::raw::{c_int, c_void};
 use std::os::unix::io::{AsRawFd, FromRawFd, IntoRawFd, RawFd};
@@ -290,7 +290,7 @@ impl crosvm {
             .write_to_vec(&mut self.request_buffer)
             .map_err(proto_error_to_int)?;
         self.socket
-            .send_with_fds(self.request_buffer.as_slice(), fds)
+            .send_with_fds(&[IoSlice::new(self.request_buffer.as_slice())], fds)
             .map_err(|e| -e.errno())?;
 
         let mut datagram_fds = [0; MAX_DATAGRAM_FD];