df: refactor filter_mount_list() to be more flat

Use a `for` loop in the `filter_mount_list()` function to make the
filtering logic easier to read.

src/uu/df/src/df.rs

@@ -161,64 +161,79 @@ impl Filesystem {
  }
 }
 
+/// Keep only the specified subset of [`MountInfo`] instances.
+///
+/// If `paths` is non-empty, this function excludes any [`MountInfo`]
+/// that is not mounted at the specified path.
+///
+/// The `opt` argument specifies a variety of ways of excluding
+/// [`MountInfo`] instances; see [`Options`] for more information.
+///
+/// Finally, if there are duplicate entries, the one with the shorter
+/// path is kept.
 fn filter_mount_list(vmi: Vec<MountInfo>, paths: &[String], opt: &Options) -> Vec<MountInfo> {
- vmi.into_iter()
- .filter_map(|mi| {
- if (mi.remote && opt.show_local_fs)
- || (mi.dummy && !opt.show_all_fs && !opt.show_listed_fs)
- || !opt.fs_selector.should_select(&mi.fs_type)
- {
- None
- } else {
- if paths.is_empty() {
- // No path specified
- return Some((mi.dev_id.clone(), mi));
- }
- if paths.contains(&mi.mount_dir) {
- // One or more paths have been provided
- Some((mi.dev_id.clone(), mi))
- } else {
- // Not a path we want to see
- None
- }
- }
- })
- .fold(
- HashMap::<String, Cell<MountInfo>>::new(),
- |mut acc, (id, mi)| {
- #[allow(clippy::map_entry)]
- {
- if acc.contains_key(&id) {
- let seen = acc[&id].replace(mi.clone());
- let target_nearer_root = seen.mount_dir.len() > mi.mount_dir.len();
- // With bind mounts, prefer items nearer the root of the source
- let source_below_root = !seen.mount_root.is_empty()
- && !mi.mount_root.is_empty()
- && seen.mount_root.len() < mi.mount_root.len();
- // let "real" devices with '/' in the name win.
- if (!mi.dev_name.starts_with('/') || seen.dev_name.starts_with('/'))
- // let points towards the root of the device win.
- && (!target_nearer_root || source_below_root)
- // let an entry over-mounted on a new device win...
- && (seen.dev_name == mi.dev_name
- /* ... but only when matching an existing mnt point,
- to avoid problematic replacement when given
- inaccurate mount lists, seen with some chroot
- environments for example. */
- || seen.mount_dir != mi.mount_dir)
- {
- acc[&id].replace(seen);
- }
- } else {
- acc.insert(id, Cell::new(mi));
- }
- acc
- }
- },
- )
- .into_iter()
- .map(|ent| ent.1.into_inner())
- .collect::<Vec<_>>()
+ let mut mount_info_by_id = HashMap::<String, Cell<MountInfo>>::new();
+ for mi in vmi {
+ // Don't show remote filesystems if `--local` has been given.
+ if mi.remote && opt.show_local_fs {
+ continue;
+ }
+
+ // Don't show pseudo filesystems unless `--all` has been given.
+ if mi.dummy && !opt.show_all_fs && !opt.show_listed_fs {
+ continue;
+ }
+
+ // Don't show filesystems if they have been explicitly excluded.
+ if !opt.fs_selector.should_select(&mi.fs_type) {
+ continue;
+ }
+
+ // Don't show filesystems other than the ones specified on the
+ // command line, if any.
+ if !paths.is_empty() && !paths.contains(&mi.mount_dir) {
+ continue;
+ }
+
+ // If the device ID has not been encountered yet, just store it.
+ let id = mi.dev_id.clone();
+ #[allow(clippy::map_entry)]
+ if !mount_info_by_id.contains_key(&id) {
+ mount_info_by_id.insert(id, Cell::new(mi));
+ continue;
+ }
+
+ // Otherwise, if we have seen the current device ID before,
+ // then check if we need to update it or keep the previously
+ // seen one.
+ let seen = mount_info_by_id[&id].replace(mi.clone());
+ let target_nearer_root = seen.mount_dir.len() > mi.mount_dir.len();
+ // With bind mounts, prefer items nearer the root of the source
+ let source_below_root = !seen.mount_root.is_empty()
+ && !mi.mount_root.is_empty()
+ && seen.mount_root.len() < mi.mount_root.len();
+ // let "real" devices with '/' in the name win.
+ if (!mi.dev_name.starts_with('/') || seen.dev_name.starts_with('/'))
+ // let points towards the root of the device win.
+ && (!target_nearer_root || source_below_root)
+ // let an entry over-mounted on a new device win...
+ && (seen.dev_name == mi.dev_name
+ /* ... but only when matching an existing mnt point,
+ to avoid problematic replacement when given
+ inaccurate mount lists, seen with some chroot
+ environments for example. */
+ || seen.mount_dir != mi.mount_dir)
+ {
+ mount_info_by_id[&id].replace(seen);
+ }
+ }
+
+ // Take ownership of the `MountInfo` instances and collect them
+ // into a `Vec`.
+ mount_info_by_id
+ .into_values()
+ .map(|m| m.into_inner())
+ .collect()
 }
 
 /// Convert `value` to a human readable string based on `base`.