Inner mutability improvements

src/fs.rs

@@ -1,6 +1,7 @@
 //! Experimental Filesystem version using closures.
 
 use core::ffi::{c_int, c_void};
+use core::marker::PhantomData;
 use core::ptr::addr_of;
 use core::ptr::addr_of_mut;
 use core::{
@@ -72,6 +73,19 @@ pub struct Allocation<Storage: driver::Storage> {
     state: ll::lfs_t,
 }
 
+/// # Safety
+///
+/// All operations are done on `&mut Allocation, and the reference is held
+/// during the entire lifetime of the filesystem, so once the reference is
+/// available again, the filesystem is closed
+unsafe impl<Storage: driver::Storage> Sync for Allocation<Storage> {}
+/// # Safety
+///
+/// All operations are done on `&mut Allocation, and the reference is held
+/// during the entire lifetime of the filesystem, so once the reference is
+/// available again, the filesystem is closed
+unsafe impl<Storage: driver::Storage> Send for Allocation<Storage> {}
+
 // pub fn check_storage_requirements(
 
 impl<Storage: driver::Storage> Default for Allocation<Storage> {
@@ -613,6 +627,7 @@ pub struct File<'a, 'b, S: driver::Storage> {
     // We must store a raw pointer here since the FFI retains a copy of a pointer
     // to the field alloc.state, so we cannot assert unique mutable access.
     alloc: RefCell<*mut FileAllocation<S>>,
+    phantom: PhantomData<RefCell<&'b mut FileAllocation<S>>>,
     fs: &'b Filesystem<'a, S>,
 }
 
@@ -803,7 +818,7 @@ impl OpenOptions {
     pub unsafe fn open<'a, 'b, S: driver::Storage>(
         &self,
         fs: &'b Filesystem<'a, S>,
-        alloc: &mut FileAllocation<S>,
+        alloc: &'b mut FileAllocation<S>,
         path: &Path,
     ) -> Result<File<'a, 'b, S>> {
         alloc.config.buffer = alloc.cache.get() as *mut _;
@@ -820,6 +835,7 @@ impl OpenOptions {
 
         let file = File {
             alloc: RefCell::new(alloc),
+            phantom: PhantomData,
             fs,
         };
 
@@ -1544,4 +1560,21 @@ mod tests {
         })
         .unwrap();
     }
+
+    #[allow(unreachable_code)]
+    fn _filesystem_is_sync() {
+        fn assert_is_sync<T: Sync, R>(_: &T) -> R {
+            todo!()
+        }
+        fn assert_is_send<T: Send, R>(_: &T) -> R {
+            todo!()
+        }
+
+        assert_is_sync::<Allocation<TestStorage>, ()>(todo!());
+        assert_is_send::<&mut Allocation<TestStorage>, ()>(todo!());
+        assert_is_send::<RefCell<&mut Allocation<TestStorage>>, ()>(todo!());
+
+        let mut test_storage = TestStorage::new();
+        Filesystem::mount_and_then(&mut test_storage, |fs| assert_is_send(fs)).unwrap()
+    }
 }