fix(fuse): keep what an open file reads when its delete is queued (B186)

crates/pdfs-fuse/src/drain.rs

@@ -994,6 +994,17 @@ impl Core {
             Err(e) => return Err(e.into()),
         }
         self.retire_trash_op(op, &uid)?;
+        // A file trashed while open kept the bytes its handle reads, and a
+        // final close while the trash was queued left them to this
+        // (`docs/BUGS.md` B186).
+        if !self.is_open_anywhere(&uid) {
+            if let Some(blob) = self.pending_blob(&uid) {
+                self.release_pending(&uid, &blob);
+                self.cache.discard_staged(&blob);
+            }
+            self.cache.evict(&uid);
+            self.evict_reader(&uid);
+        }
         if let Err(e) = self.db.clear_own_sealed_rev(&uid.to_string()) {
             debug!(%uid, error = %e, "clearing the sealed-revision record failed");
         }

crates/pdfs-fuse/src/lib.rs

@@ -3902,6 +3902,11 @@ impl Core {
     /// staged bytes that never landed — which is precisely what deleting an
     /// un-uploaded file means, and the alternative (upload it, then trash it) is
     /// worse in every way.
+    ///
+    /// A file still open keeps the bytes its handle reads, the queued ones and
+    /// the cached ones, as when the trash is sent at once: a partial write
+    /// fills its gaps from them, offline too (`docs/BUGS.md` B186). The final
+    /// close or the trash landing, whichever comes last, lets go of them.
     fn queue_trash(&self, uid: &NodeUid, name: &str) -> Result<(), Errno> {
         self.require_uid_writable(uid)?;
         // The bytes below are about to be discarded, and a drain worker may be
@@ -3917,7 +3922,18 @@ impl Core {
                 error!(%uid, error = %e, "queueing trash failed");
                 Errno::EIO
             })?;
-        self.release_dropped_ops(uid, blobs);
+        let open_now = self.is_open_anywhere(uid);
+        if open_now {
+            let read_from = self.pending_blob(uid);
+            self.release_dropped_below(
+                blobs
+                    .into_iter()
+                    .filter(|blob| read_from.as_deref() != Some(Path::new(blob)))
+                    .collect(),
+            );
+        } else {
+            self.release_dropped_ops(uid, blobs);
+        }
         self.hidden.lock().insert(uid.clone());
         // Withdrawn from the tree, which every mount serves from, so no other
         // mount goes on serving a file the user just trashed (`docs/BUGS.md`
@@ -3925,8 +3941,10 @@ impl Core {
         self.for_each_state(|st| {
             st.unlink_mem(uid);
         });
-        self.cache.evict(uid);
-        self.evict_reader(uid);
+        if !open_now {
+            self.cache.evict(uid);
+            self.evict_reader(uid);
+        }
         self.wake_drain();
         debug!(%uid, name, "trashed offline; queued");
         Ok(())

crates/pdfs-fuse/src/sim/daemon.rs

@@ -423,6 +423,59 @@ mod tests {
         let _ = std::fs::remove_dir_all(&dir);
     }
 
+    #[test]
+    #[ignore = "mounts FUSE: run with `cargo test -p pdfs-fuse sim:: -- --ignored`"]
+    fn a_file_deleted_offline_while_open_still_reads_and_takes_writes() {
+        // Queuing the trash dropped the cached bytes the open handle reads,
+        // and a partial write offline failed with EIO (B186).
+        use std::io::{Read, Seek, SeekFrom, Write};
+        let drive = FakeDrive::new();
+        let dir = scratch("unlink-open-offline");
+        let daemon = Daemon::start(&dir, drive.client(1, Faults::lan())).unwrap();
+        let path = daemon.mountpoint.join("f.txt");
+
+        std::fs::write(&path, b"0123456789").unwrap();
+        assert!(wait_until(Duration::from_secs(30), || {
+            daemon.pending().is_ok_and(|items| items.is_empty())
+                && drive.tree().get("f.txt") == Some(&Entry::File(Arc::new(b"0123456789".to_vec())))
+        }));
+        daemon.client.set_online(false);
+        let mut file = std::fs::OpenOptions::new()
+            .read(true)
+            .write(true)
+            .open(&path)
+            .unwrap();
+        std::fs::remove_file(&path).unwrap();
+        file.seek(SeekFrom::End(0)).unwrap();
+        file.write_all(b"ab").unwrap();
+        let mut read = Vec::new();
+        file.seek(SeekFrom::Start(0)).unwrap();
+        file.read_to_end(&mut read).unwrap();
+        assert_eq!(read, b"0123456789ab");
+        drop(file);
+
+        daemon.client.set_online(true);
+        assert!(
+            wait_until(Duration::from_secs(30), || {
+                daemon.pending().is_ok_and(|items| items.is_empty()) && drive.tree().is_empty()
+            }),
+            "{:?} {:?}",
+            daemon.pending(),
+            drive.tree()
+        );
+        // The bytes kept for the handle went once the trash landed with it closed.
+        let cached: Vec<_> = std::fs::read_dir(dir.join("cache"))
+            .unwrap()
+            .filter_map(|e| e.ok())
+            .filter(|e| e.file_type().is_ok_and(|t| t.is_file()))
+            .map(|e| e.file_name())
+            .collect();
+        assert!(cached.is_empty(), "{cached:?}");
+
+        assert!(matches!(daemon.stop(), Ok(MountOutcome::Shutdown)));
+        let _ = std::fs::remove_dir_all(&dir);
+    }
+
     #[test]
     #[ignore = "mounts FUSE: run with `cargo test -p pdfs-fuse sim:: -- --ignored`"]
     fn a_write_opened_as_an_upload_lands_takes_the_landed_revision_as_its_base() {