fusedev: commit() no longer returns IoError

Writing fuse replies back to kernel should always return `EncodeMessage`
with errors. So writing fuse replies will return unique error code
hinting an error happens when replies.

Signed-off-by: Changwei Ge <chge@linux.alibaba.com>

Author: chuanlang.gcw

src/api/server.rs

@@ -571,7 +571,7 @@ impl<F: FileSystem + Sync> Server<F> {
                 };
 
                 w.write_all(out.as_slice()).map_err(Error::EncodeMessage)?;
-                w.commit(&[&data_writer.0]).map_err(Error::IoError)?;
+                w.commit(&[&data_writer.0]).map_err(Error::EncodeMessage)?;
                 Ok(out.len as usize)
             }
             Err(e) => reply_error(e, in_header.unique, w),
@@ -976,7 +976,7 @@ impl<F: FileSystem + Sync> Server<F> {
             };
 
             w.write_all(out.as_slice()).map_err(Error::EncodeMessage)?;
-            w.commit(&[&cursor]).map_err(Error::IoError)?;
+            w.commit(&[&cursor]).map_err(Error::EncodeMessage)?;
             Ok(out.len as usize)
         }
     }

src/lib.rs

@@ -75,8 +75,6 @@ pub enum Error {
     /// The `size` field of the `SetxattrIn` message does not match the length
     /// of the decoded value.
     InvalidXattrSize((u32, usize)),
-    /// An IO related error has happened.
-    IoError(io::Error),
 }
 
 impl error::Error for Error {}
@@ -96,7 +94,6 @@ impl fmt::Display for Error {
                  decoded value: size = {}, value.len() = {}",
                 size, len
             ),
-            IoError(err) => write!(f, "fail to handle request: {}", err),
         }
     }
 }

src/transport/fusedev/mod.rs

@@ -163,7 +163,9 @@ impl<'a> Writer<'a> {
         if !buf.is_empty() {
             return writev(self.fd, buf.as_slice()).map_err(|e| {
                 error! {"fail to write to fuse device on commit: {}", e};
-                io::Error::new(io::ErrorKind::Other, format!("{}", e))
+                e.as_errno()
+                    .and_then(|r| Some(io::Error::from_raw_os_error(r as i32)))
+                    .unwrap_or_else(|| io::Error::new(io::ErrorKind::Other, format!("{}", e)))
             });
         }
         Ok(0)