fix(core,fuse): a node written under its stand-in after landing updates its landed row

crates/pdfs-core/src/db/nodes.rs

@@ -900,8 +900,25 @@ fn adopt_children_tx(tx: &Transaction<'_>, uid: &str, lid: i64) -> Result<()> {
 }
 
 fn upsert_node_tx(tx: &Transaction<'_>, node: &Node) -> Result<()> {
-    let json = serde_json::to_string(node)?;
     let uid = node.uid.to_string();
+    // A node written under its stand-in after it landed is its row, which has
+    // the uid Drive gave it by now: written under the stand-in, it would bring
+    // the placeholder row back beside it.
+    if let Some(lid) = local_lid(&uid) {
+        let landed: Option<String> = tx
+            .query_row(
+                "SELECT uid FROM nodes WHERE lid = ?1 AND uid IS NOT ?2",
+                params![lid, uid],
+                |row| row.get(0),
+            )
+            .optional()?;
+        if let Some(real) = landed.as_deref().and_then(parse_node_uid) {
+            let mut node = node.clone();
+            node.uid = real;
+            return upsert_node_tx(tx, &node);
+        }
+    }
+    let json = serde_json::to_string(node)?;
     let parent_uid = node.parent_uid.as_ref().map(|u| u.to_string());
 
     let prior: Option<PriorRow> = tx

crates/pdfs-core/src/db/tests.rs

@@ -3964,6 +3964,43 @@ fn a_landed_folder_rewrites_no_row_or_op_below_it() {
     );
 }
 
+/// A node the mount still holds under its stand-in, written after it landed,
+/// updates the landed row: written under the stand-in, it brought the
+/// placeholder row back beside it.
+#[test]
+fn a_stand_in_written_after_landing_updates_the_landed_row() {
+    let db = Db::open_in_memory().unwrap();
+    db.upsert_node(&folder("root", None, "My Files")).unwrap();
+    let lid = db
+        .add_local_row(&uid("root").to_string(), "a.txt", false, 1)
+        .unwrap();
+    let local = local_uid(lid);
+    let mut node = file("x", "root", "a.txt", 3);
+    node.uid = NodeUid::new(VolumeId::from("local"), LinkId::from(lid.to_string()));
+    db.upsert_node(&node).unwrap();
+    db.land_placeholder_row(&local, &uid("a").to_string())
+        .unwrap();
+
+    node.name = "b.txt".into();
+    db.upsert_node(&node).unwrap();
+
+    let rows: Vec<(i64, String, String)> = {
+        let conn = db.conn.lock();
+        let mut stmt = conn
+            .prepare("SELECT lid, uid, name FROM nodes WHERE uid != ?1")
+            .unwrap();
+        stmt.query_map([uid("root").to_string()], |r| {
+            Ok((r.get(0)?, r.get(1)?, r.get(2)?))
+        })
+        .unwrap()
+        .collect::<rusqlite::Result<_>>()
+        .unwrap()
+    };
+    assert_eq!(rows, [(lid, uid("a").to_string(), "b.txt".to_string())]);
+    let landed = db.node_by_uid(&uid("a").to_string()).unwrap().unwrap();
+    assert_eq!((landed.uid, landed.name), (uid("a"), "b.txt".to_string()));
+}
+
 /// A create queued inside a folder made here is sent under the folder's real
 /// uid once it lands. Landing where it was sent is no move.
 #[test]

crates/pdfs-fuse/src/lib.rs

@@ -169,10 +169,6 @@ const DRAIN_BACKOFF_MAX: Duration = Duration::from_secs(300);
 /// directly on a new write or a reconnect, so this only bounds how late a
 /// backoff can fire.
 const DRAIN_IDLE_POLL: Duration = Duration::from_secs(30);
-/// How long a write whose create just landed waits for the drain to repoint
-/// its inode (`Core::landed_uid`): 200 polls of 10 ms, two seconds in all.
-const LANDED_UID_POLLS: u32 = 200;
-const LANDED_UID_POLL: Duration = Duration::from_millis(10);
 /// How long the mount waits before asking again for a node it has just created
 /// when Drive does not list it yet (`Core::fetch_minted_node`).
 const MINTED_READ_BACK_DELAYS: [Duration; 2] = [Duration::from_millis(250), Duration::from_secs(1)];
@@ -3430,9 +3426,9 @@ impl Core {
                     break 'queued attached.superseded;
                 }
                 drop(pending);
-                // The create landed while this handle was open. Its uid is the
-                // one the drain has just given the inode.
-                let Some(real) = self.landed_uid(ino) else {
+                // The create landed while this handle was open, and its row
+                // already has the uid Drive gave it.
+                let Some(real) = self.landed_row_uid(ino) else {
                     error!(%uid, staged = %path.display(),
                            "queued create vanished under a write; bytes kept in staging");
                     return Err(Errno::EIO);
@@ -3511,23 +3507,6 @@ impl Core {
         Ok(())
     }
 
-    /// The real uid the drain gave `ino` when its queued create landed.
-    ///
-    /// Called by a write that found the create already retired. The drain
-    /// repoints the inode right after it drops `pending`, with no network in
-    /// between, so a short wait covers the gap; `None` means the inode is gone
-    /// or never stopped being a placeholder.
-    fn landed_uid(&self, ino: u64) -> Option<NodeUid> {
-        for _ in 0..LANDED_UID_POLLS {
-            let uid = self.state().entries.get(&ino).map(|e| e.uid.clone())?;
-            if !is_local_uid(&uid) {
-                return Some(uid);
-            }
-            std::thread::sleep(LANDED_UID_POLL);
-        }
-        None
-    }
-
     /// Queue the new content of a path-based truncate — `> file`, or any
     /// `setattr(size=…)` arriving without a write handle.
     ///

docs/MILESTONE-3.0.0-STATUS.md

@@ -36,7 +36,7 @@ Tracks `docs/MILESTONE-3.0.0.md`. Update it with every commit that moves a phase
          places each node under its parent's row as it is now.
    - [x] Queries over children, subtrees and ancestors by `parent_lid`, and no rewrite of the
          children's `parent_uid` when a folder lands (R3), nor of the ops made inside it (R2).
-   - [ ] No more placeholders: a node made here goes by its local id until it lands. In four
+   - [x] No more placeholders: a node made here goes by its local id until it lands. In four
          parts:
      - [x] 6a: a node made here goes by `local~<lid>`, a function of its row, instead of a
            minted `local~<ms>-<n>`; schema 41 rewrites the old placeholders (nodes, ops, pins).
@@ -48,10 +48,13 @@ Tracks `docs/MILESTONE-3.0.0.md`. Update it with every commit that moves a phase
            now. The row keeps its stand-in in `nodes.uid` rather than `NULL`: it is as stable,
            and `NULL` would have changed some 40 node queries for no change in behaviour. Pins
            stay keyed by uid and move with the row in the landing transaction (B148).
-     - [ ] 6d: in memory, `pending`, `hidden` and `creating` by lid; `is_local_uid` checks
-           become `remote_uid().is_none()`; a write or rename after landing queues under the
-           stand-in, so `landed_uid`, `follow_landed_create`, `landed_row_uid` and the
-           `rewrite_op_target` fallback go.
+     - [x] 6d: a node written under its stand-in after it landed updates its landed row
+           instead of bringing the placeholder row back, so a write that finds its create
+           landed takes the uid from the row and no longer polls the tree for up to 2 s
+           (`landed_uid` is gone). In memory, `pending`, the uploads and the tree stay keyed by
+           the uid Drive knows: ops are matched by lid in the database (6b), `hidden` and
+           `creating` only ever hold remote uids, and `landed_row_uid` is the one place at the
+           mount's edge where a stand-in a handle still holds becomes the real uid.
    - [ ] An executor that runs ops in dependency order, many at once.
 3. **Speed (§7)**: run independent ops in parallel, batch trashes and moves; measure 1,000 files
    and 100 folders on Wi-Fi against LAN (target: within 10 %).