cp: add support of cp --debug

src/uu/cp/src/cp.rs

@@ -229,10 +229,79 @@ pub struct Options {
     backup_suffix: String,
     target_dir: Option<PathBuf>,
     update: UpdateMode,
+    debug: bool,
     verbose: bool,
     progress_bar: bool,
 }
 
+/// Enum representing various debug states of the offload and reflink actions.
+#[derive(Debug)]
+#[allow(dead_code)] // All of them are used on Linux
+enum OffloadReflinkDebug {
+    Unknown,
+    No,
+    Yes,
+    Avoided,
+    Unsupported,
+}
+
+/// Enum representing various debug states of the sparse detection.
+#[derive(Debug)]
+#[allow(dead_code)] // silent for now until we use them
+enum SparseDebug {
+    Unknown,
+    No,
+    Zeros,
+    SeekHole,
+    SeekHoleZeros,
+    Unsupported,
+}
+
+/// Struct that contains the debug state for each action in a file copy operation.
+#[derive(Debug)]
+struct CopyDebug {
+    offload: OffloadReflinkDebug,
+    reflink: OffloadReflinkDebug,
+    sparse_detection: SparseDebug,
+}
+
+impl OffloadReflinkDebug {
+    fn to_string(&self) -> &'static str {
+        match self {
+            Self::No => "no",
+            Self::Yes => "yes",
+            Self::Avoided => "avoided",
+            Self::Unsupported => "unsupported",
+            Self::Unknown => "unknown",
+        }
+    }
+}
+
+impl SparseDebug {
+    fn to_string(&self) -> &'static str {
+        match self {
+            Self::No => "no",
+            Self::Zeros => "zeros",
+            Self::SeekHole => "SEEK_HOLE",
+            Self::SeekHoleZeros => "SEEK_HOLE + zeros",
+            Self::Unsupported => "unsupported",
+            Self::Unknown => "unknown",
+        }
+    }
+}
+
+/// This function prints the debug information of a file copy operation if
+/// no hard link or symbolic link is required, and data copy is required.
+/// It prints the debug information of the offload, reflink, and sparse detection actions.
+fn show_debug(copy_debug: &CopyDebug) {
+    println!(
+        "copy offload: {}, reflink: {}, sparse detection: {}",
+        copy_debug.offload.to_string(),
+        copy_debug.reflink.to_string(),
+        copy_debug.sparse_detection.to_string(),
+    );
+}
+
 const ABOUT: &str = help_about!("cp.md");
 const USAGE: &str = help_usage!("cp.md");
 const AFTER_HELP: &str = help_section!("after help", "cp.md");
@@ -269,6 +338,7 @@ mod options {
     pub const STRIP_TRAILING_SLASHES: &str = "strip-trailing-slashes";
     pub const SYMBOLIC_LINK: &str = "symbolic-link";
     pub const TARGET_DIRECTORY: &str = "target-directory";
+    pub const DEBUG: &str = "debug";
     pub const VERBOSE: &str = "verbose";
 }
 
@@ -361,6 +431,12 @@ pub fn uu_app() -> Command {
                 .help("remove any trailing slashes from each SOURCE argument")
                 .action(ArgAction::SetTrue),
         )
+        .arg(
+            Arg::new(options::DEBUG)
+                .long(options::DEBUG)
+                .help("explain how a file is copied. Implies -v")
+                .action(ArgAction::SetTrue),
+        )
         .arg(
             Arg::new(options::VERBOSE)
                 .short('v')
@@ -831,7 +907,8 @@ impl Options {
             one_file_system: matches.get_flag(options::ONE_FILE_SYSTEM),
             parents: matches.get_flag(options::PARENTS),
             update: update_mode,
-            verbose: matches.get_flag(options::VERBOSE),
+            debug: matches.get_flag(options::DEBUG),
+            verbose: matches.get_flag(options::VERBOSE) || matches.get_flag(options::DEBUG),
             strip_trailing_slashes: matches.get_flag(options::STRIP_TRAILING_SLASHES),
             reflink_mode: {
                 if let Some(reflink) = matches.get_one::<String>(options::REFLINK) {
@@ -1745,7 +1822,7 @@ fn copy_helper(
     } else if source_is_symlink {
         copy_link(source, dest, symlinked_files)?;
     } else {
-        copy_on_write(
+        let copy_debug = copy_on_write(
             source,
             dest,
             options.reflink_mode,
@@ -1754,6 +1831,10 @@ fn copy_helper(
             #[cfg(any(target_os = "linux", target_os = "android", target_os = "macos"))]
             source_is_fifo,
         )?;
+
+        if !options.attributes_only && options.debug {
+            show_debug(&copy_debug);
+        }
     }
 
     Ok(())

src/uu/cp/src/platform/linux.rs

@@ -13,7 +13,7 @@ use quick_error::ResultExt;
 
 use uucore::mode::get_umask;
 
-use crate::{CopyResult, ReflinkMode, SparseMode};
+use crate::{CopyDebug, CopyResult, OffloadReflinkDebug, ReflinkMode, SparseDebug, SparseMode};
 
 // From /usr/include/linux/fs.h:
 // #define FICLONE		_IOW(0x94, 9, int)
@@ -145,24 +145,51 @@ pub(crate) fn copy_on_write(
     sparse_mode: SparseMode,
     context: &str,
     source_is_fifo: bool,
-) -> CopyResult<()> {
+) -> CopyResult<CopyDebug> {
+    let mut copy_debug = CopyDebug {
+        offload: OffloadReflinkDebug::Unknown,
+        reflink: OffloadReflinkDebug::Unsupported,
+        sparse_detection: SparseDebug::No,
+    };
+
     let result = match (reflink_mode, sparse_mode) {
-        (ReflinkMode::Never, SparseMode::Always) => sparse_copy(source, dest),
-        (ReflinkMode::Never, _) => std::fs::copy(source, dest).map(|_| ()),
-        (ReflinkMode::Auto, SparseMode::Always) => sparse_copy(source, dest),
+        (ReflinkMode::Never, SparseMode::Always) => {
+            copy_debug.sparse_detection = SparseDebug::Zeros;
+            copy_debug.offload = OffloadReflinkDebug::Avoided;
+            copy_debug.reflink = OffloadReflinkDebug::No;
+            sparse_copy(source, dest)
+        }
+        (ReflinkMode::Never, _) => {
+            copy_debug.sparse_detection = SparseDebug::No;
+            copy_debug.reflink = OffloadReflinkDebug::No;
+            std::fs::copy(source, dest).map(|_| ())
+        }
+        (ReflinkMode::Auto, SparseMode::Always) => {
+            copy_debug.offload = OffloadReflinkDebug::Avoided;
+            copy_debug.sparse_detection = SparseDebug::Zeros;
+            copy_debug.reflink = OffloadReflinkDebug::Unsupported;
+            sparse_copy(source, dest)
+        }
 
         (ReflinkMode::Auto, _) => {
+            copy_debug.sparse_detection = SparseDebug::No;
+            copy_debug.reflink = OffloadReflinkDebug::Unsupported;
             if source_is_fifo {
                 copy_fifo_contents(source, dest).map(|_| ())
             } else {
                 clone(source, dest, CloneFallback::FSCopy)
             }
         }
-        (ReflinkMode::Always, SparseMode::Auto) => clone(source, dest, CloneFallback::Error),
+        (ReflinkMode::Always, SparseMode::Auto) => {
+            copy_debug.sparse_detection = SparseDebug::No;
+            copy_debug.reflink = OffloadReflinkDebug::Yes;
+
+            clone(source, dest, CloneFallback::Error)
+        }
         (ReflinkMode::Always, _) => {
             return Err("`--reflink=always` can be used only with --sparse=auto".into())
         }
     };
     result.context(context)?;
-    Ok(())
+    Ok(copy_debug)
 }

src/uu/cp/src/platform/macos.rs

@@ -11,7 +11,7 @@ use std::path::Path;
 
 use quick_error::ResultExt;
 
-use crate::{CopyResult, ReflinkMode, SparseMode};
+use crate::{CopyDebug, CopyResult, OffloadReflinkDebug, ReflinkMode, SparseDebug, SparseMode};
 
 /// Copies `source` to `dest` using copy-on-write if possible.
 ///
@@ -24,10 +24,15 @@ pub(crate) fn copy_on_write(
     sparse_mode: SparseMode,
     context: &str,
     source_is_fifo: bool,
-) -> CopyResult<()> {
+) -> CopyResult<CopyDebug> {
     if sparse_mode != SparseMode::Auto {
         return Err("--sparse is only supported on linux".to_string().into());
     }
+    let mut copy_debug = CopyDebug {
+        offload: OffloadReflinkDebug::Unknown,
+        reflink: OffloadReflinkDebug::Unsupported,
+        sparse_detection: SparseDebug::Unsupported,
+    };
 
     // Extract paths in a form suitable to be passed to a syscall.
     // The unwrap() is safe because they come from the command-line and so contain non nul
@@ -72,6 +77,7 @@ pub(crate) fn copy_on_write(
                 return Err(format!("failed to clone {source:?} from {dest:?}: {error}").into())
             }
             _ => {
+                copy_debug.reflink = OffloadReflinkDebug::Yes;
                 if source_is_fifo {
                     let mut src_file = File::open(source)?;
                     let mut dst_file = File::create(dest)?;
@@ -83,5 +89,5 @@ pub(crate) fn copy_on_write(
         };
     }
 
-    Ok(())
+    Ok(copy_debug)
 }

src/uu/cp/src/platform/other.rs

@@ -8,7 +8,7 @@ use std::path::Path;
 
 use quick_error::ResultExt;
 
-use crate::{CopyResult, ReflinkMode, SparseMode};
+use crate::{CopyDebug, CopyResult, OffloadReflinkDebug, ReflinkMode, SparseDebug, SparseMode};
 
 /// Copies `source` to `dest` for systems without copy-on-write
 pub(crate) fn copy_on_write(
@@ -17,7 +17,7 @@ pub(crate) fn copy_on_write(
     reflink_mode: ReflinkMode,
     sparse_mode: SparseMode,
     context: &str,
-) -> CopyResult<()> {
+) -> CopyResult<CopyDebug> {
     if reflink_mode != ReflinkMode::Never {
         return Err("--reflink is only supported on linux and macOS"
             .to_string()
@@ -26,8 +26,12 @@ pub(crate) fn copy_on_write(
     if sparse_mode != SparseMode::Auto {
         return Err("--sparse is only supported on linux".to_string().into());
     }
-
+    let copy_debug = CopyDebug {
+        offload: OffloadReflinkDebug::Unsupported,
+        reflink: OffloadReflinkDebug::Unsupported,
+        sparse_detection: SparseDebug::Unsupported,
+    };
     fs::copy(source, dest).context(context)?;
 
-    Ok(())
+    Ok(copy_debug)
 }