dd: ignore a failed cache drop while copying

Signed-off-by: Zhiwei Liang <zhiwei.liang@zliang.me>

Author: ChihweiLHBird

src/uu/dd/src/bufferedoutput.rs

@@ -41,8 +41,8 @@ impl<'a> BufferedOutput<'a> {
         Ok(Self { inner, buf })
     }
 
-    pub(crate) fn discard_cache(&self, offset: u64, len: u64) {
-        self.inner.discard_cache(offset, len);
+    pub(crate) fn discard_cache(&self, offset: u64, len: u64) -> std::io::Result<()> {
+        self.inner.discard_cache(offset, len)
     }
 
     /// Flush the partial block stored in the internal buffer.

src/uu/dd/src/dd.rs

@@ -53,7 +53,6 @@ use uucore::display::Quotable;
 use uucore::error::{FromIo, UResult};
 #[cfg(unix)]
 use uucore::error::{USimpleError, set_exit_code};
-#[cfg(any(target_os = "linux", target_os = "android", target_os = "freebsd"))]
 use uucore::show_if_err;
 use uucore::{format_usage, show_error};
 
@@ -495,28 +494,22 @@ impl Input<'_> {
     ///
     /// `offset` and `len` specify a contiguous portion of the input.
     /// This function informs the kernel that the specified portion of
-    /// the input file is no longer needed. If not possible, then this
-    /// function prints an error message to stderr and sets the exit
-    /// status code to 1.
-    #[cfg_attr(
-        not(any(target_os = "linux", target_os = "android", target_os = "freebsd")),
-        allow(clippy::unused_self, unused_variables)
+    /// the input file is no longer needed. If not possible, the error is
+    /// returned and the caller decides whether to report it; only the
+    /// `count=0` path in [`flush_caches_full_length`] does.
+    #[cfg(any(target_os = "linux", target_os = "android", target_os = "freebsd"))]
+    fn discard_cache(&self, offset: u64, len: u64) -> io::Result<()> {
+        self.src.discard_cache(offset, len)
+    }
+
+    // TODO: Is there a way to discard filesystem cache on other targets?
+    #[cfg(not(any(target_os = "linux", target_os = "android", target_os = "freebsd")))]
+    #[allow(
+        clippy::unnecessary_wraps,
+        reason = "platform stub; keeps one signature for every caller"
     )]
-    fn discard_cache(&self, offset: u64, len: u64) {
-        #[cfg(any(target_os = "linux", target_os = "android", target_os = "freebsd"))]
-        {
-            let file = self
-                .settings
-                .infile
-                .clone()
-                .unwrap_or_else(|| translate!("dd-standard-input"));
-            show_if_err!(
-                self.src.discard_cache(offset, len).map_err_context(
-                    || translate!("dd-error-failed-discard-cache", "file" => file)
-                )
-            );
-        }
-        // TODO: Is there a way to discard filesystem cache on other targets?
+    fn discard_cache(&self, _offset: u64, _len: u64) -> io::Result<()> {
+        Ok(())
     }
 
     /// Fills a given buffer.
@@ -948,28 +941,22 @@ impl<'a> Output<'a> {
     ///
     /// `offset` and `len` specify a contiguous portion of the output.
     /// This function informs the kernel that the specified portion of
-    /// the output file is no longer needed. If not possible, then
-    /// this function prints an error message to stderr and sets the
-    /// exit status code to 1.
-    #[cfg_attr(
-        not(any(target_os = "linux", target_os = "android", target_os = "freebsd")),
-        allow(clippy::unused_self, unused_variables)
+    /// the output file is no longer needed. If not possible, the error is
+    /// returned and the caller decides whether to report it; only the
+    /// `count=0` path in [`flush_caches_full_length`] does.
+    #[cfg(any(target_os = "linux", target_os = "android", target_os = "freebsd"))]
+    fn discard_cache(&self, offset: u64, len: u64) -> io::Result<()> {
+        self.dst.discard_cache(offset, len)
+    }
+
+    // TODO: Is there a way to discard filesystem cache on other targets?
+    #[cfg(not(any(target_os = "linux", target_os = "android", target_os = "freebsd")))]
+    #[allow(
+        clippy::unnecessary_wraps,
+        reason = "platform stub; keeps one signature for every caller"
     )]
-    fn discard_cache(&self, offset: u64, len: u64) {
-        #[cfg(any(target_os = "linux", target_os = "android", target_os = "freebsd"))]
-        {
-            let file = self
-                .settings
-                .outfile
-                .clone()
-                .unwrap_or_else(|| translate!("dd-standard-output"));
-            show_if_err!(
-                self.dst.discard_cache(offset, len).map_err_context(
-                    || translate!("dd-error-failed-discard-cache", "file" => file)
-                )
-            );
-        }
-        // TODO Is there a way to discard filesystem cache on other targets?
+    fn discard_cache(&self, _offset: u64, _len: u64) -> io::Result<()> {
+        Ok(())
     }
 
     /// writes a block of data. optionally retries when first try didn't complete
@@ -1057,7 +1044,7 @@ enum BlockWriter<'a> {
 }
 
 impl BlockWriter<'_> {
-    fn discard_cache(&self, offset: u64, len: u64) {
+    fn discard_cache(&self, offset: u64, len: u64) -> io::Result<()> {
         match self {
             Self::Unbuffered(o) => o.discard_cache(offset, len),
             Self::Buffered(o) => o.discard_cache(offset, len),
@@ -1103,10 +1090,26 @@ impl BlockWriter<'_> {
 fn flush_caches_full_length(i: &Input, o: &Output) {
     // Using len=0 in posix_fadvise means "to end of file"
     if i.settings.iflags.nocache {
-        i.discard_cache(0, 0);
+        let file = i
+            .settings
+            .infile
+            .clone()
+            .unwrap_or_else(|| translate!("dd-standard-input"));
+        show_if_err!(
+            i.discard_cache(0, 0)
+                .map_err_context(|| translate!("dd-error-failed-discard-cache", "file" => file))
+        );
     }
     if i.settings.oflags.nocache {
-        o.discard_cache(0, 0);
+        let file = o
+            .settings
+            .outfile
+            .clone()
+            .unwrap_or_else(|| translate!("dd-standard-output"));
+        show_if_err!(
+            o.discard_cache(0, 0)
+                .map_err_context(|| translate!("dd-error-failed-discard-cache", "file" => file))
+        );
     }
 }
 
@@ -1246,10 +1249,10 @@ fn dd_copy(mut i: Input, o: Output) -> io::Result<()> {
         };
         if rstat_update.is_empty() {
             if input_nocache {
-                i.discard_cache(read_offset, 0);
+                let _ = i.discard_cache(read_offset, 0);
             }
             if output_nocache || output_direct {
-                o.discard_cache(write_offset.try_into().unwrap(), 0);
+                let _ = o.discard_cache(write_offset.try_into().unwrap(), 0);
             }
             break;
         }
@@ -1265,7 +1268,7 @@ fn dd_copy(mut i: Input, o: Output) -> io::Result<()> {
         if input_nocache {
             let offset = read_offset;
             let len = read_len;
-            i.discard_cache(offset, len);
+            let _ = i.discard_cache(offset, len);
         }
         read_offset += read_len;
 
@@ -1277,7 +1280,7 @@ fn dd_copy(mut i: Input, o: Output) -> io::Result<()> {
         if output_nocache {
             let offset = write_offset.try_into().unwrap();
             let len = write_len.try_into().unwrap();
-            o.discard_cache(offset, len);
+            let _ = o.discard_cache(offset, len);
         }
         write_offset += write_len;
 

tests/by-util/test_dd.rs

@@ -1899,6 +1899,26 @@ fn test_iflag_directory_fails_when_file_is_piped_via_std_in() {
         .stderr_only("dd: setting flags for 'standard input': Not a directory\n");
 }
 
+#[test]
+#[cfg(any(target_os = "linux", target_os = "android"))]
+fn test_nocache_on_a_pipe_is_silent_at_eof() {
+    new_ucmd!()
+        .args(&["iflag=nocache", "oflag=nocache", "status=none"])
+        .pipe_in("")
+        .succeeds()
+        .no_output();
+}
+
+#[test]
+#[cfg(any(target_os = "linux", target_os = "android"))]
+fn test_nocache_on_a_pipe_is_silent_while_copying() {
+    new_ucmd!()
+        .args(&["iflag=nocache", "oflag=nocache", "status=none"])
+        .pipe_in("abc")
+        .succeeds()
+        .stdout_only("abc");
+}
+
 #[test]
 fn test_stdin_stdout_not_rewound_even_when_connected_to_seekable_file() {
     let ts = TestScenario::new(util_name!());