implemented direct mounting without libfuse or fusermount

Author: Vociferix

Cargo.toml

@@ -59,6 +59,7 @@ libfuse2 = ["libfuse"]
 libfuse3 = ["libfuse"]
 serializable = ["serde"]
 macfuse-4-compat = []
+direct-mount = ["nix/resource", "nix/signal"]
 # abi-7-xx feature flags are deprecated and don't do anything.
 abi-7-20 = []
 abi-7-21 = []

build.rs

@@ -1,7 +1,7 @@
 fn main() {
     // Register rustc cfg for switching between mount implementations.
     println!(
-        "cargo::rustc-check-cfg=cfg(fuser_mount_impl, values(\"pure-rust\", \"libfuse2\", \"libfuse3\", \"macos-no-mount\"))"
+        "cargo::rustc-check-cfg=cfg(fuser_mount_impl, values(\"direct-mount\", \"pure-rust\", \"libfuse2\", \"libfuse3\", \"macos-no-mount\"))"
     );
 
     let target_os =
@@ -12,7 +12,11 @@ fn main() {
         "linux" | "freebsd" | "dragonfly" | "openbsd" | "netbsd"
     ) && cfg!(not(feature = "libfuse"))
     {
-        println!("cargo::rustc-cfg=fuser_mount_impl=\"pure-rust\"");
+        if cfg!(feature = "direct-mount") {
+            println!("cargo::rustc-cfg=fuser_mount_impl=\"direct-mount\"");
+        } else {
+            println!("cargo::rustc-cfg=fuser_mount_impl=\"pure-rust\"");
+        }
     } else if target_os == "macos" {
         if cfg!(feature = "macos-no-mount") {
             println!("cargo::rustc-cfg=fuser_mount_impl=\"macos-no-mount\"");

fuser-tests/src/commands/bsd_mount.rs

@@ -8,13 +8,24 @@ use crate::ansi::green;
 use crate::canonical_temp_dir::CanonicalTempDir;
 use crate::cargo::cargo_build_example;
 use crate::command_utils::command_success;
+use crate::features::Feature;
 use crate::mount_util::wait_for_fuse_mount;
 
 pub(crate) async fn run_bsd_mount_tests() -> anyhow::Result<()> {
+    // Run tests using pure-rust (fusermount) implementation
+    run_bsd_mount_tests_with_features(&[]).await?;
+
+    // Run tests using direct-mount (direct mount syscall) implementation
+    run_bsd_mount_tests_with_features(&[Feature::DirectMount]).await?;
+
+    Ok(())
+}
+
+async fn run_bsd_mount_tests_with_features(features: &[Feature]) -> anyhow::Result<()> {
     let mount_dir = CanonicalTempDir::new()?;
     let mount_path = mount_dir.path();
 
-    let hello_exe = cargo_build_example("hello", &[]).await?;
+    let hello_exe = cargo_build_example("hello", features).await?;
 
     eprintln!("Starting hello filesystem...");
     let mut fuse_process = Command::new(&hello_exe)

fuser-tests/src/commands/mount.rs

@@ -44,6 +44,25 @@ async fn run_mount_tests_inner(libfuse: Libfuse) -> anyhow::Result<()> {
     run_test(&[], Unmount::Auto, libfuse.fusermount(), 1, false).await?;
     test_no_user_allow_other(&[], &libfuse).await?;
 
+    // Tests without libfuse feature (direct mount syscall implementation)
+    run_test(
+        &[Feature::DirectMount],
+        Unmount::Manual,
+        Fusermount::False,
+        1,
+        false,
+    )
+    .await?;
+    run_test(
+        &[Feature::DirectMount],
+        Unmount::Auto,
+        Fusermount::False,
+        1,
+        false,
+    )
+    .await?;
+    test_no_user_allow_other(&[Feature::DirectMount], &libfuse).await?;
+
     // Tests with libfuse
     run_test(
         &[libfuse.feature()],
@@ -65,6 +84,22 @@ async fn run_mount_tests_inner(libfuse: Libfuse) -> anyhow::Result<()> {
     // Multi-threaded tests
     run_test(&[], Unmount::Auto, libfuse.fusermount(), 2, false).await?;
     run_test(&[], Unmount::Auto, libfuse.fusermount(), 2, true).await?;
+    run_test(
+        &[Feature::DirectMount],
+        Unmount::Auto,
+        Fusermount::False,
+        2,
+        false,
+    )
+    .await?;
+    run_test(
+        &[Feature::DirectMount],
+        Unmount::Auto,
+        Fusermount::False,
+        2,
+        true,
+    )
+    .await?;
 
     if let Libfuse::Libfuse3 = libfuse {
         run_allow_root_test()

fuser-tests/src/features.rs

@@ -11,6 +11,8 @@ pub(crate) enum Feature {
     Libfuse2,
     /// Use libfuse3 for mounting.
     Libfuse3,
+    /// Use mount syscall directly for mounting.
+    DirectMount,
 }
 
 impl Feature {
@@ -20,6 +22,7 @@ impl Feature {
             Feature::Experimental => "experimental",
             Feature::Libfuse2 => "libfuse2",
             Feature::Libfuse3 => "libfuse3",
+            Feature::DirectMount => "direct-mount",
         }
     }
 }