From 4190fe22ef3ea96a65fcd7bb9a5d9dbe43c0b10e Mon Sep 17 00:00:00 2001
From: Sergei Patiakin <sergei.patiakin@gmail.com>
Date: Thu, 17 Apr 2025 22:06:20 +0200
Subject: [PATCH] fix: df: filter filesystem types after mount point resolution
 (#7452)

Closes: #6194
---
 src/uu/df/src/df.rs      | 84 +++++++++++++---------------------------
 tests/by-util/test_df.rs |  6 +++
 2 files changed, 33 insertions(+), 57 deletions(-)

diff --git a/src/uu/df/src/df.rs b/src/uu/df/src/df.rs
index 71c580a15..9e2bb6920 100644
--- a/src/uu/df/src/df.rs
+++ b/src/uu/df/src/df.rs
@@ -12,7 +12,7 @@ use blocks::HumanReadable;
 use clap::builder::ValueParser;
 use table::HeaderMode;
 use uucore::display::Quotable;
-use uucore::error::{UError, UResult, USimpleError};
+use uucore::error::{UError, UResult, USimpleError, get_exit_code};
 use uucore::fsext::{MountInfo, read_fs_list};
 use uucore::parser::parse_size::ParseSizeError;
 use uucore::{format_usage, help_about, help_section, help_usage, show};
@@ -222,7 +222,10 @@ fn is_included(mi: &MountInfo, opt: &Options) -> bool {
     }
 
     // Don't show pseudo filesystems unless `--all` has been given.
-    if mi.dummy && !opt.show_all_fs {
+    // The "lofs" filesystem is a loopback
+    // filesystem present on Solaris and FreeBSD systems. It
+    // is similar to a symbolic link.
+    if (mi.dummy || mi.fs_type == "lofs") && !opt.show_all_fs {
         return false;
     }
 
@@ -285,28 +288,6 @@ fn is_best(previous: &[MountInfo], mi: &MountInfo) -> bool {
     true
 }
 
-/// Keep only the specified subset of [`MountInfo`] instances.
-///
-/// 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>, opt: &Options) -> Vec<MountInfo> {
-    let mut result = vec![];
-    for mi in vmi {
-        // TODO The running time of the `is_best()` function is linear
-        // in the length of `result`. That makes the running time of
-        // this loop quadratic in the length of `vmi`. This could be
-        // improved by a more efficient implementation of `is_best()`,
-        // but `vmi` is probably not very long in practice.
-        if is_included(&mi, opt) && is_best(&result, &mi) {
-            result.push(mi);
-        }
-    }
-    result
-}
-
 /// Get all currently mounted filesystems.
 ///
 /// `opt` excludes certain filesystems from consideration and allows for the synchronization of filesystems before running; see
@@ -323,11 +304,17 @@ fn get_all_filesystems(opt: &Options) -> UResult<Vec<Filesystem>> {
         }
     }
 
-    // The list of all mounted filesystems.
-    //
-    // Filesystems excluded by the command-line options are
-    // not considered.
-    let mounts: Vec<MountInfo> = filter_mount_list(read_fs_list()?, opt);
+    let mut mounts = vec![];
+    for mi in read_fs_list()? {
+        // TODO The running time of the `is_best()` function is linear
+        // in the length of `result`. That makes the running time of
+        // this loop quadratic in the length of `vmi`. This could be
+        // improved by a more efficient implementation of `is_best()`,
+        // but `vmi` is probably not very long in practice.
+        if is_included(&mi, opt) && is_best(&mounts, &mi) {
+            mounts.push(mi);
+        }
+    }
 
     // Convert each `MountInfo` into a `Filesystem`, which contains
     // both the mount information and usage information.
@@ -358,29 +345,19 @@ where
     P: AsRef<Path>,
 {
     // The list of all mounted filesystems.
-    //
-    // Filesystems marked as `dummy` or of type "lofs" are not
-    // considered. The "lofs" filesystem is a loopback
-    // filesystem present on Solaris and FreeBSD systems. It
-    // is similar to a symbolic link.
-    let mounts: Vec<MountInfo> = filter_mount_list(read_fs_list()?, opt)
-        .into_iter()
-        .filter(|mi| mi.fs_type != "lofs" && !mi.dummy)
-        .collect();
+    let mounts: Vec<MountInfo> = read_fs_list()?;
 
     let mut result = vec![];
 
-    // this happens if the file system type doesn't exist
-    if mounts.is_empty() {
-        show!(USimpleError::new(1, "no file systems processed"));
-        return Ok(result);
-    }
-
     // Convert each path into a `Filesystem`, which contains
     // both the mount information and usage information.
     for path in paths {
         match Filesystem::from_path(&mounts, path) {
-            Ok(fs) => result.push(fs),
+            Ok(fs) => {
+                if is_included(&fs.mount_info, opt) {
+                    result.push(fs);
+                }
+            }
             Err(FsError::InvalidPath) => {
                 show!(USimpleError::new(
                     1,
@@ -402,6 +379,11 @@ where
             }
         }
     }
+    if get_exit_code() == 0 && result.is_empty() {
+        show!(USimpleError::new(1, "no file systems processed"));
+        return Ok(result);
+    }
+
     Ok(result)
 }
 
@@ -853,16 +835,4 @@ mod tests {
             assert!(is_included(&m, &opt));
         }
     }
-
-    mod filter_mount_list {
-
-        use crate::{Options, filter_mount_list};
-
-        #[test]
-        fn test_empty() {
-            let opt = Options::default();
-            let mount_infos = vec![];
-            assert!(filter_mount_list(mount_infos, &opt).is_empty());
-        }
-    }
 }
diff --git a/tests/by-util/test_df.rs b/tests/by-util/test_df.rs
index 95131e556..d9d632961 100644
--- a/tests/by-util/test_df.rs
+++ b/tests/by-util/test_df.rs
@@ -303,6 +303,12 @@ fn test_type_option_with_file() {
         .fails()
         .stderr_contains("no file systems processed");
 
+    // Assume the mount point at /dev has a different filesystem type to the mount point at /
+    new_ucmd!()
+        .args(&["-t", fs_type, "/dev"])
+        .fails()
+        .stderr_contains("no file systems processed");
+
     let fs_types = new_ucmd!()
         .arg("--output=fstype")
         .succeeds()