Implement the foreground option for the mount command

Inspired by cberner/fuser#179 (comment)
The program exits when ctrl-c is pressed or when the filesystem is
unmounted (e.g. fusermount -u <mountpoint>)

Note that this issue zargony/fuse-rs#151
prevents using the destroy callback for notifying us that the filesystem
was unmounted, so we use the drop callback as a workaround.

Signed-off-by: Ariel Miculas <[email protected]>

exe/Cargo.toml

@@ -9,6 +9,7 @@ anyhow = "*"
 nix = "*"
 clap = { version = "4.0.18", features = ["derive"] }
 daemonize = "0.4"
+ctrlc = "3.2.0"
 format = { path = "../format" }
 builder = { path = "../builder" }
 oci = { path = "../oci" }

exe/src/main.rs

@@ -7,7 +7,7 @@ use builder::build_initial_rootfs;
 use daemonize::Daemonize;
 use extractor::extract_rootfs;
 use oci::Image;
-use reader::mount;
+use reader::{mount, spawn_mount};
 
 #[derive(Parser)]
 #[command(author, version, about)]
@@ -35,6 +35,8 @@ struct Mount {
  oci_dir: String,
  tag: String,
  mountpoint: String,
+ #[arg(short, long)]
+ foreground: bool,
 }
 
 #[derive(Args)]
@@ -55,17 +57,33 @@ fn main() -> anyhow::Result<()> {
  image.add_tag(b.tag, desc).map_err(|e| e.into())
  }
  SubCommand::Mount(m) => {
- // TODO: add --foreground option?
  let oci_dir = Path::new(&m.oci_dir);
  let image = Image::new(oci_dir)?;
  let mountpoint = Path::new(&m.mountpoint);
- let stdout = File::create("/tmp/puzzlefs.out")?;
- let stderr = File::create("/tmp/puzzlefs.err")?;
- let daemonize = Daemonize::new().stdout(stdout).stderr(stderr);
 
- match daemonize.start() {
- Ok(_) => mount(&image, &m.tag, mountpoint)?,
- Err(e) => eprintln!("Error, {}", e),
+ if m.foreground {
+ let (send, recv) = std::sync::mpsc::channel();
+ let send_ctrlc = send.clone();
+
+ ctrlc::set_handler(move || {
+ println!("puzzlefs unmounted");
+ send_ctrlc.send(()).unwrap();
+ })
+ .unwrap();
+
+ let fuse_thread_finished = send;
+ let _guard = spawn_mount(&image, &m.tag, mountpoint, Some(fuse_thread_finished))?;
+ // This blocks until either ctrl-c is pressed or the filesystem is unmounted
+ let () = recv.recv().unwrap();
+ } else {
+ let stdout = File::create("/tmp/puzzlefs.out")?;
+ let stderr = File::create("/tmp/puzzlefs.err")?;
+ let daemonize = Daemonize::new().stdout(stdout).stderr(stderr);
+
+ match daemonize.start() {
+ Ok(_) => mount(&image, &m.tag, mountpoint)?,
+ Err(e) => eprintln!("Error, {}", e),
+ }
  }
 
  Ok(())

reader/src/fuse.rs

@@ -16,6 +16,7 @@ use super::puzzlefs::{file_read, Inode, InodeMode, PuzzleFS};
 
 pub struct Fuse<'a> {
  pfs: PuzzleFS<'a>,
+ sender: Option<std::sync::mpsc::Sender<()>>,
  // TODO: LRU cache inodes or something. I had problems fiddling with the borrow checker for the
  // cache, so for now we just do each lookup every time.
 }
@@ -36,8 +37,8 @@ fn mode_to_fuse_type(inode: &Inode) -> Result<FileType> {
 }
 
 impl<'a> Fuse<'a> {
- pub fn new(pfs: PuzzleFS<'a>) -> Fuse<'a> {
- Fuse { pfs }
+ pub fn new(pfs: PuzzleFS<'a>, sender: Option<std::sync::mpsc::Sender<()>>) -> Fuse<'a> {
+ Fuse { pfs, sender }
  }
 
  fn _lookup(&mut self, parent: u64, name: &OsStr) -> Result<FileAttr> {
@@ -106,6 +107,17 @@ impl<'a> Fuse<'a> {
  }
 }
 
+impl Drop for Fuse<'_> {
+ fn drop(&mut self) {
+ // This code should be in the destroy function inside the Filesystem implementation
+ // Unfortunately, destroy is not getting called: https://github.com/zargony/fuse-rs/issues/151
+ // This is fixed in fuser, which we're not using right now: https://github.com/cberner/fuser/issues/153
+ if let Some(sender) = &self.sender {
+ sender.send(()).unwrap();
+ }
+ }
+}
+
 impl Filesystem for Fuse<'_> {
  fn init(&mut self, _req: &Request) -> std::result::Result<(), c_int> {
  Ok(())
@@ -463,7 +475,7 @@ mod tests {
  let rootfs_desc = build_test_fs(Path::new("../builder/test/test-1"), &image).unwrap();
  image.add_tag("test".to_string(), rootfs_desc).unwrap();
  let mountpoint = tempdir().unwrap();
- let _bg = crate::spawn_mount(&image, "test", Path::new(mountpoint.path())).unwrap();
+ let _bg = crate::spawn_mount(&image, "test", Path::new(mountpoint.path()), None).unwrap();
  let ents = fs::read_dir(mountpoint.path())
  .unwrap()
  .collect::<io::Result<Vec<fs::DirEntry>>>()

reader/src/lib.rs

@@ -16,7 +16,7 @@ pub use walk::WalkPuzzleFS;
 
 pub fn mount(image: &Image, tag: &str, mountpoint: &Path) -> Result<()> {
  let pfs = PuzzleFS::open(image, tag)?;
- let fuse = Fuse::new(pfs);
+ let fuse = Fuse::new(pfs, None);
  fuse_ffi::mount(fuse, &mountpoint, &[])?;
  Ok(())
 }
@@ -25,8 +25,9 @@ pub fn spawn_mount<'a>(
  image: &'a Image,
  tag: &str,
  mountpoint: &Path,
+ sender: Option<std::sync::mpsc::Sender<()>>,
 ) -> Result<fuse_ffi::BackgroundSession<'a>> {
  let pfs = PuzzleFS::open(image, tag)?;
- let fuse = Fuse::new(pfs);
+ let fuse = Fuse::new(pfs, sender);
  unsafe { Ok(fuse_ffi::spawn_mount(fuse, &mountpoint, &[])?) }
 }