Refactor Session to allow callers to mount it themselves

This is a minor refactor of `Session`, with the aim of allowing callers
to create an unmounted session and mount it themselves (using the AsFd
implementation to get the FD).

One use case for this is when mounting inside containers, when you need
to call setns(2) before mounting.

Fixes #300

Author: colinmarc

examples/notify_inval_entry.rs

@@ -162,9 +162,9 @@ fn main() {
         timeout: Duration::from_secs_f32(opts.timeout),
     };
 
-    let session = fuser::Session::new(fs, opts.mount_point, &options).unwrap();
+    let (session, mount) = fuser::Session::new(fs, opts.mount_point, &options).unwrap();
     let notifier = session.notifier();
-    let _bg = session.spawn().unwrap();
+    let _bg = fuser::BackgroundSession::new(session, mount);
 
     loop {
         let mut fname = fname.lock().unwrap();

examples/notify_inval_inode.rs

@@ -200,9 +200,9 @@ fn main() {
         lookup_cnt,
     };
 
-    let session = fuser::Session::new(fs, opts.mount_point, &options).unwrap();
+    let (session, mount) = fuser::Session::new(fs, opts.mount_point, &options).unwrap();
     let notifier = session.notifier();
-    let _bg = session.spawn().unwrap();
+    let _bg = fuser::BackgroundSession::new(session, mount);
 
     loop {
         let mut s = fdata.lock().unwrap();

examples/poll.rs

@@ -337,8 +337,8 @@ fn main() {
     let fs = FSelFS { data: data.clone() };
 
     let mntpt = std::env::args().nth(1).unwrap();
-    let session = fuser::Session::new(fs, mntpt, &options).unwrap();
-    let bg = session.spawn().unwrap();
+    let (session, mount) = fuser::Session::new(fs, mntpt, &options).unwrap();
+    let bg = fuser::BackgroundSession::new(session, mount).unwrap();
 
     producer(&data, &bg.notifier());
 }

src/lib.rs

@@ -39,7 +39,7 @@ pub use reply::{
     ReplyStatfs, ReplyWrite,
 };
 pub use request::Request;
-pub use session::{BackgroundSession, Session, SessionUnmounter};
+pub use session::{BackgroundSession, Session, Unmounter};
 #[cfg(feature = "abi-7-28")]
 use std::cmp::max;
 #[cfg(feature = "abi-7-13")]
@@ -1008,7 +1008,8 @@ pub fn mount<FS: Filesystem, P: AsRef<Path>>(
 }
 
 /// Mount the given filesystem to the given mountpoint. This function will
-/// not return until the filesystem is unmounted.
+/// not return until the filesystem is unmounted. This function requires
+/// CAP_SYS_ADMIN to run.
 ///
 /// NOTE: This will eventually replace mount(), once the API is stable
 pub fn mount2<FS: Filesystem, P: AsRef<Path>>(
@@ -1017,7 +1018,9 @@ pub fn mount2<FS: Filesystem, P: AsRef<Path>>(
     options: &[MountOption],
 ) -> io::Result<()> {
     check_option_conflicts(options, false)?;
-    Session::new(filesystem, mountpoint.as_ref(), options).and_then(|mut se| se.run())
+    let (mut session, _mount) = Session::new(filesystem, mountpoint, options)?;
+
+    session.run()
 }
 
 /// Mount the given filesystem using fusermount(1). The binary must exist on
@@ -1028,7 +1031,9 @@ pub fn fusermount(
     options: &[MountOption],
 ) -> io::Result<()> {
     check_option_conflicts(options, true)?;
-    Session::new_fusermount(filesystem, mountpoint, options).and_then(|mut se| se.run())
+    let (mut session, _mount) = Session::new_fusermount(filesystem, mountpoint, options)?;
+
+    session.run()
 }
 
 /// Mount the given filesystem to the given mountpoint. This function spawns
@@ -1066,7 +1071,9 @@ pub fn spawn_mount2<'a, FS: Filesystem + Send + 'static + 'a, P: AsRef<Path>>(
     options: &[MountOption],
 ) -> io::Result<BackgroundSession> {
     check_option_conflicts(options, false)?;
-    Session::new(filesystem, mountpoint.as_ref(), options).and_then(|se| se.spawn())
+
+    let (session, mount) = Session::new(filesystem, mountpoint, options)?;
+    BackgroundSession::new(session, mount)
 }
 
 /// Mount the given filesystem to the given mountpoint. This function spawns
@@ -1084,5 +1091,7 @@ pub fn spawn_fusermount<'a, FS: Filesystem + Send + 'static + 'a>(
     options: &[MountOption],
 ) -> io::Result<BackgroundSession> {
     check_option_conflicts(options, true)?;
-    Session::new_fusermount(filesystem, mountpoint, options).and_then(|se| se.spawn())
+
+    let (session, mount) = Session::new(filesystem, mountpoint, options)?;
+    BackgroundSession::new(session, mount)
 }