cp: fix the result of inodes are not the same when preserve links is flagged (uutils#5064)

Should fix:
```
rm -rf a b c
touch a
ln -s a b
mkdir c
./target/debug/coreutils cp --preserve=links -R -H a b c
a_inode=$(ls -i c/a|sed 's,c/.*,,')
b_inode=$(ls -i c/b|sed 's,c/.*,,')
echo "$a_inode" = "$b_inode"
```

Author: tommady

src/uu/cp/src/copydir.rs

@@ -8,7 +8,7 @@
 //! See the [`copy_directory`] function for more information.
 #[cfg(windows)]
 use std::borrow::Cow;
-use std::collections::HashSet;
+use std::collections::{HashMap, HashSet};
 use std::env;
 use std::fs;
 use std::io;
@@ -24,8 +24,8 @@ use uucore::uio_error;
 use walkdir::{DirEntry, WalkDir};
 
 use crate::{
-    aligned_ancestors, context_for, copy_attributes, copy_file, copy_link, preserve_hardlinks,
-    CopyResult, Error, Options,
+    aligned_ancestors, context_for, copy_attributes, copy_file, copy_link, CopyResult, Error,
+    Options,
 };
 
 /// Ensure a Windows path starts with a `\\?`.
@@ -200,7 +200,7 @@ fn copy_direntry(
     options: &Options,
     symlinked_files: &mut HashSet<FileInformation>,
     preserve_hard_links: bool,
-    hard_links: &mut Vec<(String, u64)>,
+    copied_files: &mut HashMap<FileInformation, PathBuf>,
 ) -> CopyResult<()> {
     let Entry {
         source_absolute,
@@ -240,30 +240,27 @@ fn copy_direntry(
     // If the source is not a directory, then we need to copy the file.
     if !source_absolute.is_dir() {
         if preserve_hard_links {
-            let dest = local_to_target.as_path().to_path_buf();
-            let found_hard_link = preserve_hardlinks(hard_links, &source_absolute, &dest)?;
-            if !found_hard_link {
-                match copy_file(
-                    progress_bar,
-                    &source_absolute,
-                    local_to_target.as_path(),
-                    options,
-                    symlinked_files,
-                    false,
-                ) {
-                    Ok(_) => Ok(()),
-                    Err(err) => {
-                        if source_absolute.is_symlink() {
-                            // silent the error with a symlink
-                            // In case we do --archive, we might copy the symlink
-                            // before the file itself
-                            Ok(())
-                        } else {
-                            Err(err)
-                        }
+            match copy_file(
+                progress_bar,
+                &source_absolute,
+                local_to_target.as_path(),
+                options,
+                symlinked_files,
+                copied_files,
+                false,
+            ) {
+                Ok(_) => Ok(()),
+                Err(err) => {
+                    if source_absolute.is_symlink() {
+                        // silent the error with a symlink
+                        // In case we do --archive, we might copy the symlink
+                        // before the file itself
+                        Ok(())
+                    } else {
+                        Err(err)
                     }
-                }?;
-            }
+                }
+            }?;
         } else {
             // At this point, `path` is just a plain old file.
             // Terminate this function immediately if there is any
@@ -277,6 +274,7 @@ fn copy_direntry(
                 local_to_target.as_path(),
                 options,
                 symlinked_files,
+                copied_files,
                 false,
             ) {
                 Ok(_) => {}
@@ -310,6 +308,7 @@ pub(crate) fn copy_directory(
     target: &Path,
     options: &Options,
     symlinked_files: &mut HashSet<FileInformation>,
+    copied_files: &mut HashMap<FileInformation, PathBuf>,
     source_in_command_line: bool,
 ) -> CopyResult<()> {
     if !options.recursive {
@@ -324,6 +323,7 @@ pub(crate) fn copy_directory(
             target,
             options,
             symlinked_files,
+            copied_files,
             source_in_command_line,
         );
     }
@@ -372,7 +372,6 @@ pub(crate) fn copy_directory(
     };
     let target = tmp.as_path();
 
-    let mut hard_links: Vec<(String, u64)> = vec![];
     let preserve_hard_links = options.preserve_hard_links();
 
     // Collect some paths here that are invariant during the traversal
@@ -397,7 +396,7 @@ pub(crate) fn copy_directory(
                     options,
                     symlinked_files,
                     preserve_hard_links,
-                    &mut hard_links,
+                    copied_files,
                 )?;
             }
             // Print an error message, but continue traversing the directory.

src/uu/cp/src/cp.rs

@@ -9,7 +9,7 @@
 use quick_error::quick_error;
 use std::borrow::Cow;
 use std::cmp::Ordering;
-use std::collections::HashSet;
+use std::collections::{HashMap, HashSet};
 use std::env;
 #[cfg(not(windows))]
 use std::ffi::CString;
@@ -1106,67 +1106,6 @@ fn parse_path_args(
     Ok((paths, target))
 }
 
-/// Get the inode information for a file.
-fn get_inode(file_info: &FileInformation) -> u64 {
-    #[cfg(unix)]
-    let result = file_info.inode();
-    #[cfg(windows)]
-    let result = file_info.file_index();
-    result
-}
-
-#[cfg(target_os = "redox")]
-fn preserve_hardlinks(
-    hard_links: &mut Vec<(String, u64)>,
-    source: &std::path::Path,
-    dest: &std::path::Path,
-    found_hard_link: &mut bool,
-) -> CopyResult<()> {
-    // Redox does not currently support hard links
-    Ok(())
-}
-
-/// Hard link a pair of files if needed _and_ record if this pair is a new hard link.
-#[cfg(not(target_os = "redox"))]
-fn preserve_hardlinks(
-    hard_links: &mut Vec<(String, u64)>,
-    source: &std::path::Path,
-    dest: &std::path::Path,
-) -> CopyResult<bool> {
-    let info = FileInformation::from_path(source, false)
-        .context(format!("cannot stat {}", source.quote()))?;
-    let inode = get_inode(&info);
-    let nlinks = info.number_of_links();
-    let mut found_hard_link = false;
-    #[allow(clippy::explicit_iter_loop)]
-    for (link, link_inode) in hard_links.iter() {
-        if *link_inode == inode {
-            // Consider the following files:
-            //
-            // * `src/f` - a regular file
-            // * `src/link` - a hard link to `src/f`
-            // * `dest/src/f` - a different regular file
-            //
-            // In this scenario, if we do `cp -a src/ dest/`, it is
-            // possible that the order of traversal causes `src/link`
-            // to get copied first (to `dest/src/link`). In that case,
-            // in order to make sure `dest/src/link` is a hard link to
-            // `dest/src/f` and `dest/src/f` has the contents of
-            // `src/f`, we delete the existing file to allow the hard
-            // linking.
-            if file_or_link_exists(dest) && file_or_link_exists(Path::new(link)) {
-                std::fs::remove_file(dest)?;
-            }
-            std::fs::hard_link(link, dest).unwrap();
-            found_hard_link = true;
-        }
-    }
-    if !found_hard_link && nlinks > 1 {
-        hard_links.push((dest.to_str().unwrap().to_string(), inode));
-    }
-    Ok(found_hard_link)
-}
-
 /// When handling errors, we don't always want to show them to the user. This function handles that.
 fn show_error_if_needed(error: &Error) {
     match error {
@@ -1195,14 +1134,19 @@ pub fn copy(sources: &[PathBuf], target: &Path, options: &Options) -> CopyResult
     let target_type = TargetType::determine(sources, target);
     verify_target_type(target, &target_type)?;
 
-    let preserve_hard_links = options.preserve_hard_links();
-
-    let mut hard_links: Vec<(String, u64)> = vec![];
-
     let mut non_fatal_errors = false;
     let mut seen_sources = HashSet::with_capacity(sources.len());
     let mut symlinked_files = HashSet::new();
 
+    // to remember the copied files for further usage.
+    // the FileInformation implemented the Hash trait by using
+    // 1. inode number
+    // 2. device number
+    // the combination of a file's inode number and device number is unique throughout all the file systems.
+    //
+    // key is the source file's information and the value is the destination filepath.
+    let mut copied_files: HashMap<FileInformation, PathBuf> = HashMap::with_capacity(sources.len());
+
     let progress_bar = if options.progress_bar {
         let pb = ProgressBar::new(disk_usage(sources, options.recursive)?)
             .with_style(
@@ -1222,28 +1166,19 @@ pub fn copy(sources: &[PathBuf], target: &Path, options: &Options) -> CopyResult
         if seen_sources.contains(source) {
             // FIXME: compare sources by the actual file they point to, not their path. (e.g. dir/file == dir/../dir/file in most cases)
             show_warning!("source {} specified more than once", source.quote());
-        } else {
-            let found_hard_link = if preserve_hard_links && !source.is_dir() {
-                let dest = construct_dest_path(source, target, &target_type, options)?;
-                preserve_hardlinks(&mut hard_links, source, &dest)?
-            } else {
-                false
-            };
-            if !found_hard_link {
-                if let Err(error) = copy_source(
-                    &progress_bar,
-                    source,
-                    target,
-                    &target_type,
-                    options,
-                    &mut symlinked_files,
-                ) {
-                    show_error_if_needed(&error);
-                    non_fatal_errors = true;
-                }
-            }
-            seen_sources.insert(source);
+        } else if let Err(error) = copy_source(
+            &progress_bar,
+            source,
+            target,
+            &target_type,
+            options,
+            &mut symlinked_files,
+            &mut copied_files,
+        ) {
+            show_error_if_needed(&error);
+            non_fatal_errors = true;
         }
+        seen_sources.insert(source);
     }
 
     if let Some(pb) = progress_bar {
@@ -1295,11 +1230,20 @@ fn copy_source(
     target_type: &TargetType,
     options: &Options,
     symlinked_files: &mut HashSet<FileInformation>,
+    copied_files: &mut HashMap<FileInformation, PathBuf>,
 ) -> CopyResult<()> {
     let source_path = Path::new(&source);
     if source_path.is_dir() {
         // Copy as directory
-        copy_directory(progress_bar, source, target, options, symlinked_files, true)
+        copy_directory(
+            progress_bar,
+            source,
+            target,
+            options,
+            symlinked_files,
+            copied_files,
+            true,
+        )
     } else {
         // Copy as file
         let dest = construct_dest_path(source_path, target, target_type, options)?;
@@ -1309,6 +1253,7 @@ fn copy_source(
             dest.as_path(),
             options,
             symlinked_files,
+            copied_files,
             true,
         );
         if options.parents {
@@ -1570,6 +1515,24 @@ fn handle_existing_dest(
         OverwriteMode::Clobber(ClobberMode::RemoveDestination) => {
             fs::remove_file(dest)?;
         }
+        OverwriteMode::Clobber(ClobberMode::Standard) => {
+            // Consider the following files:
+            //
+            // * `src/f` - a regular file
+            // * `src/link` - a hard link to `src/f`
+            // * `dest/src/f` - a different regular file
+            //
+            // In this scenario, if we do `cp -a src/ dest/`, it is
+            // possible that the order of traversal causes `src/link`
+            // to get copied first (to `dest/src/link`). In that case,
+            // in order to make sure `dest/src/link` is a hard link to
+            // `dest/src/f` and `dest/src/f` has the contents of
+            // `src/f`, we delete the existing file to allow the hard
+            // linking.
+            if options.preserve_hard_links() {
+                fs::remove_file(dest)?;
+            }
+        }
         _ => (),
     };
 
@@ -1643,6 +1606,7 @@ fn copy_file(
     dest: &Path,
     options: &Options,
     symlinked_files: &mut HashSet<FileInformation>,
+    copied_files: &mut HashMap<FileInformation, PathBuf>,
     source_in_command_line: bool,
 ) -> CopyResult<()> {
     if (options.update == UpdateMode::ReplaceIfOlder || options.update == UpdateMode::ReplaceNone)
@@ -1686,6 +1650,19 @@ fn copy_file(
         handle_existing_dest(source, dest, options, source_in_command_line)?;
     }
 
+    if options.preserve_hard_links() {
+        // if we encounter a matching device/inode pair in the source tree
+        // we can arrange to create a hard link between the corresponding names
+        // in the destination tree.
+        if let Some(new_source) = copied_files.get(
+            &FileInformation::from_path(source, options.dereference(source_in_command_line))
+                .context(format!("cannot stat {}", source.quote()))?,
+        ) {
+            std::fs::hard_link(new_source, dest)?;
+            return Ok(());
+        };
+    }
+
     if options.verbose {
         if let Some(pb) = progress_bar {
             // Suspend (hide) the progress bar so the println won't overlap with the progress bar.
@@ -1873,6 +1850,11 @@ fn copy_file(
 
     copy_attributes(source, dest, &options.attributes)?;
 
+    copied_files.insert(
+        FileInformation::from_path(source, options.dereference(source_in_command_line))?,
+        dest.to_path_buf(),
+    );
+
     if let Some(progress_bar) = progress_bar {
         progress_bar.inc(fs::metadata(source)?.len());
     }