fs_util: remove dead set_readwrite_recursive after post-TraceMachina#2347 cleanup

After TraceMachina#2347 (DirectoryCache cleanup uses set_dir_writable_recursive)
and this PR (post-clonefile path uses chmod_dir_writable), the
generic set_readwrite_recursive helper has zero remaining callers.
Both replacements are intentionally narrower - set_dir_writable_recursive
chmods only directories so file inodes aren't mutated, and
chmod_dir_writable chmods only the destination root so the clone
tree stays read-only inside. Delete the old helper and its private
companion set_readwrite_one_path.

Addresses palfrey's review feedback on TraceMachina#2347 ("set_readwrite_recursive
and set_readwrite_one_path can be dropped as part of this") - sequenced
on this PR instead because both PRs had to land before the helpers
became dead.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: erneestoc

nativelink-util/src/fs_util.rs

@@ -294,21 +294,6 @@ pub async fn set_readonly_recursive(dir: &Path) -> Result<(), Error> {
     set_perms_recursive_impl(dir.to_path_buf(), set_readonly_one_path).await
 }
 
-/// Sets a directory tree to read-write for the current user recursively.
-/// This is done so we can delete directories we're evicting.
-///
-/// # Arguments
-/// * `dir` - Directory to make read-write
-///
-/// # Platform Notes
-/// - Unix: Sets permissions to 0o755 (rwxr-xr-x)
-/// - Windows: Clears `FILE_ATTRIBUTE_READONLY`
-pub async fn set_readwrite_recursive(dir: &Path) -> Result<(), Error> {
-    error_if!(!dir.exists(), "Directory does not exist: {}", dir.display());
-
-    set_perms_recursive_impl(dir.to_path_buf(), set_readwrite_one_path).await
-}
-
 /// Sets only the **directories** in a tree to writable for the current user,
 /// leaving files untouched. This is the safe variant for cleanup paths that
 /// need to delete a tree containing CAS-hardlinked files.
@@ -366,41 +351,6 @@ fn set_readonly_one_path(
     })
 }
 
-fn set_readwrite_one_path(
-    path: PathBuf,
-    metadata: Metadata,
-) -> Pin<Box<dyn Future<Output = Result<(), Error>> + Send>> {
-    Box::pin(async move {
-        // Set the file/directory to read-write for the current user
-        #[cfg(unix)]
-        {
-            use std::os::unix::fs::PermissionsExt;
-            let mut perms = metadata.permissions();
-
-            // If it's a directory, set to rwxr-xr-x (755)
-            // If it's a file, set to rw-r--r-- (644)
-            let mode = if metadata.is_dir() { 0o755 } else { 0o644 };
-            perms.set_mode(mode);
-
-            fs::set_permissions(&path, perms)
-                .await
-                .err_tip(|| format!("Failed to set permissions for: {}", path.display()))?;
-        }
-
-        #[cfg(windows)]
-        {
-            let mut perms = metadata.permissions();
-            perms.set_readonly(false);
-
-            fs::set_permissions(&path, perms)
-                .await
-                .err_tip(|| format!("Failed to set permissions for: {}", path.display()))?;
-        }
-
-        Ok(())
-    })
-}
-
 fn set_dir_writable_one_path(
     path: PathBuf,
     metadata: Metadata,

nativelink-worker/src/directory_cache.rs

@@ -451,8 +451,8 @@ impl DirectoryCache {
             // CRITICAL: only chmod directories writable, never files. Cached
             // files share an inode with FilesystemStore CAS entries via
             // hardlink (see `download_to_directory` in running_actions_manager).
-            // Calling `set_readwrite_recursive` here would chmod those files
-            // to 0o644, mutating the CAS inode's mode for every other in-flight
+            // A naive recursive chmod here would mutate those files to 0o644,
+            // changing the CAS inode's mode for every other in-flight
             // action that has hardlinked the same blob and causing EACCES on
             // exec (e.g. cc_wrapper.sh) or EPERM on open. Directory write
             // permission is sufficient on unix to unlink files inside.