api: forget and batch forget must not reply

Otherwise, the kernel would fail the reply write syscall with ENOENT and we
cannot tell whether it's because fuse connection is closed or not.

Signed-off-by: Peng Tao <[email protected]>

Author: bergwolf

src/api/server/sync_io.rs

@@ -39,6 +39,14 @@ impl<F: FileSystem + Sync> Server<F> {
         let in_header: InHeader = r.read_obj().map_err(Error::DecodeMessage)?;
         let mut ctx = SrvContext::<F, S>::new(in_header, r, w);
         if ctx.in_header.len > (MAX_BUFFER_SIZE + BUFFER_HEADER_SIZE) {
+            if in_header.opcode == Opcode::Forget as u32
+                || in_header.opcode == Opcode::BatchForget as u32
+            {
+                // Forget and batch-forget do not require reply.
+                return Err(Error::InvalidMessage(io::Error::from_raw_os_error(
+                    libc::EOVERFLOW,
+                )));
+            }
             return ctx.reply_error_explicit(io::Error::from_raw_os_error(libc::ENOMEM));
         }
 
@@ -1007,10 +1015,14 @@ impl<F: FileSystem + Sync> Server<F> {
 
         if let Some(size) = (count as usize).checked_mul(size_of::<ForgetOne>()) {
             if size > MAX_BUFFER_SIZE as usize {
-                return ctx.reply_error_explicit(io::Error::from_raw_os_error(libc::ENOMEM));
+                return Err(Error::InvalidMessage(io::Error::from_raw_os_error(
+                    libc::EOVERFLOW,
+                )));
             }
         } else {
-            return ctx.reply_error_explicit(io::Error::from_raw_os_error(libc::EOVERFLOW));
+            return Err(Error::InvalidMessage(io::Error::from_raw_os_error(
+                libc::EOVERFLOW,
+            )));
         }
 
         let mut requests = Vec::with_capacity(count as usize);

src/lib.rs

@@ -74,6 +74,8 @@ pub enum Error {
     /// The `size` field of the `SetxattrIn` message does not match the length
     /// of the decoded value.
     InvalidXattrSize((u32, usize)),
+    /// Invalid message that the server cannot handle properly.
+    InvalidMessage(io::Error),
 }
 
 impl error::Error for Error {}
@@ -92,6 +94,7 @@ impl fmt::Display for Error {
                 "The `size` field of the `SetxattrIn` message does not match the length of the \
                  decoded value: size = {size}, value.len() = {len}"
             ),
+            InvalidMessage(err) => write!(f, "cannot process fuse message: {err}"),
         }
     }
 }