change close_rc()'s API (#414)

* change close_rc() to return Result<bool>

* update doc

* add enum CloseResult

Co-authored-by: Hippolyte Barraud <[email protected]>

glommio/src/io/dma_file.rs

@@ -25,6 +25,16 @@ use std::{
 
 pub(super) type Result<T> = crate::Result<T, ()>;
 
+/// Close result of [`DmaFile::close_rc()`]. Indicates which operation is
+/// performed on close.
+#[derive(Debug)]
+pub enum CloseResult {
+    /// The file is closed.
+    Closed,
+    /// There are other references existing, only removed this one.
+    Unreferenced,
+}
+
 pub(crate) fn align_up(v: u64, align: u64) -> u64 {
     (v + align - 1) & !(align - 1)
 }
@@ -403,15 +413,13 @@ impl DmaFile {
         self.file.path()
     }
 
-    /// Convenience method that closes a DmaFile wrapped inside an Rc
-    pub async fn close_rc(self: Rc<DmaFile>) -> Result<()> {
+    /// Convenience method that closes a DmaFile wrapped inside an Rc.
+    ///
+    /// Returns [CloseResult] to indicate which operation was performed.
+    pub async fn close_rc(self: Rc<DmaFile>) -> Result<CloseResult> {
         match Rc::try_unwrap(self) {
-            Err(file) => Err(io::Error::new(
-                io::ErrorKind::Other,
-                format!("{} references to file still held", Rc::strong_count(&file)),
-            )
-            .into()),
-            Ok(file) => file.close().await,
+            Err(_) => Ok(CloseResult::Unreferenced),
+            Ok(file) => file.close().await.map(|_| CloseResult::Closed),
         }
     }
 }

glommio/src/io/dma_file_stream.rs

@@ -408,10 +408,7 @@ impl DmaStreamReader {
         let to_cancel = handles.len();
         let cancelled = stream::iter(handles).then(|f| f).count().await;
         assert_eq!(to_cancel, cancelled);
-
-        // the file may be used by other processes so failing to close it is not an
-        // issue.
-        let _ = self.file.close_rc().await;
+        self.file.close_rc().await.unwrap();
 
         let mut state = self.state.borrow_mut();
         match state.error.take() {

glommio/src/io/immutable_file.rs

@@ -429,10 +429,9 @@ impl ImmutableFile {
     }
 
     /// Closes this [`ImmutableFile`]
-    /// Note that this method returns an error if other entities hold references
-    /// to the underlying file, such as read streams.
     pub async fn close(self) -> Result<()> {
-        self.stream_builder.file.close_rc().await
+        self.stream_builder.file.close_rc().await?;
+        Ok(())
     }
 
     /// Creates a [`DmaStreamReaderBuilder`] from this `ImmutableFile`.

glommio/src/io/mod.rs

@@ -163,7 +163,7 @@ pub use self::{
     },
     bulk_io::{IoVec, ReadManyResult},
     directory::Directory,
-    dma_file::DmaFile,
+    dma_file::{CloseResult, DmaFile},
     dma_file_stream::{
         DmaStreamReader,
         DmaStreamReaderBuilder,