cat: fix usage on FUSE

Author: oech3

src/uu/cat/src/splice.rs

@@ -7,7 +7,7 @@ use super::{CatResult, FdReadable, InputHandle};
 use rustix::io::{read, write};
 use std::os::{fd::AsFd, unix::io::AsRawFd};
 
-use uucore::pipes::{MAX_ROOTLESS_PIPE_SIZE, pipe, splice, splice_exact};
+use uucore::pipes::{MAX_ROOTLESS_PIPE_SIZE, pipe, send_one_byte, splice, splice_exact};
 
 const BUF_SIZE: usize = 1024 * 16;
 
@@ -30,15 +30,15 @@ pub(super) fn write_fast_using_splice<R: FdReadable, S: AsRawFd + AsFd>(
         loop {
             match splice(&handle.reader, &write_fd, MAX_ROOTLESS_PIPE_SIZE) {
                 Ok(1..) => {}
-                Ok(0) => return Ok(false),
+                Ok(0) => return Ok(send_one_byte(&handle.reader, &write_fd)),
                 Err(_) => return Ok(true),
             }
         }
     } else if let Ok((pipe_rd, pipe_wr)) = pipe() {
         // both of in/output are not pipe. needs broker to use splice() with additional costs
         loop {
             match splice(&handle.reader, &pipe_wr, MAX_ROOTLESS_PIPE_SIZE) {
-                Ok(0) => return Ok(false),
+                Ok(0) => return Ok(send_one_byte(&handle.reader, &write_fd)),
                 Ok(n) => {
                     if splice_exact(&pipe_rd, write_fd, n).is_err() {
                         // If the first splice manages to copy to the intermediate

src/uucore/src/lib/features/pipes.rs

@@ -50,6 +50,18 @@ pub fn splice(source: &impl AsFd, target: &impl AsFd, len: usize) -> std::io::Re
     )?)
 }
 
+/// check that splice reached to end of file
+/// try to send 1 byte and return true if succeed
+/// a workaround for kernel's bug with FUSE reporting wrong size
+/// https://github.com/uutils/coreutils/issues/9609
+#[inline]
+#[cfg(any(target_os = "linux", target_os = "android"))]
+pub fn send_one_byte(source: &impl AsFd, target: &impl AsFd) -> bool {
+    use rustix::io::{read, write};
+    let mut b = [0u8; 1];
+    read(source, &mut b).is_ok_and(|n| n > 0 && write(target, &b).is_ok())
+}
+
 /// Splice wrapper which fully finishes the write.
 ///
 /// Exactly `len` bytes are moved from `source` into `target`.