cat: do not splice() on FUSE

Author: oech3

.vscode/cspell.dictionaries/workspace.wordlist.txt

@@ -367,6 +367,7 @@ uutils
 
 # * function names
 execfn
+fstatfs
 getcwd
 setpipe
 

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, might_fuse, pipe, 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(might_fuse(&handle.reader)),
                 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(might_fuse(&handle.reader)),
                 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

@@ -62,6 +62,16 @@ pub fn splice_exact(source: &impl AsFd, target: &impl AsFd, len: usize) -> std::
     Ok(())
 }
 
+/// check that source is FUSE
+/// we fallback to read() at FUSE <https://github.com/uutils/coreutils/issues/9609>
+#[inline]
+#[cfg(any(target_os = "linux", target_os = "android"))]
+pub fn might_fuse(source: &impl AsFd) -> bool {
+    rustix::fs::fstatfs(source)
+        .map(|stats| stats.f_type == 0x6573_5546) // FUSE magic number, too many platform specific clippy warning with const
+        .unwrap_or(true)
+}
+
 /// Return verified /dev/null
 ///
 /// `splice` to /dev/null is faster than `read` when we skip or count the non-seekable input