From 7ba7b4b981b5dec2e0d3beeb7076ea3256a4a99b Mon Sep 17 00:00:00 2001
From: Josh Robson Chase <josh@robsonchase.com>
Date: Wed, 6 May 2026 15:29:09 -0400
Subject: [PATCH] fs: Pre-filter the event kind before acquiring global lock
 and cloning callback handlers (#55683)

In #54481, the `handle_event` function was altered to check for an
`Access` event after the callbacks were acquired via a global state
lock. The lock/Vec-collect has enough overhead (or maybe there's enough
lock contention?) that the handler isn't performant enough to keep up
with the volume of inotify events, and its queue fills up, resulting in
[a rescan event getting
emitted](https://github.com/notify-rs/notify/blob/79007aefb41d9f853d00656eb768600e3ea41ee0/notify/src/inotify.rs#L304-L306),
which presumably results in *more* access events for the file as it's
rescanned, which further serve to fill up the inotify queue.

Moving the check for an `Access` event and returning before doing
anything remotely expensive seems to resolve the issues I've been having
lately. Not sure if it addresses the original issue in #53480 though.

Longer-term, it might be prudent to do the event handler's heavy-lifting
in a separate thread with its own event queue, and let the handler
passed to the `notify` crate be just a dumb `tx` sender.

Self-Review Checklist:

- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
- [ ] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable

Related to #53480
Fixes #55829

Release Notes:

- Fixed inotify event queue overflows on linux
---
 crates/fs/src/fs_watcher.rs | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/crates/fs/src/fs_watcher.rs b/crates/fs/src/fs_watcher.rs
index 6db36992dece57d307b2b0a1f2a4c31c76c94cd5..f99d5d0b70eb775455397b44176eb26efe5c370e 100644
--- a/crates/fs/src/fs_watcher.rs
+++ b/crates/fs/src/fs_watcher.rs
@@ -1,4 +1,4 @@
-use notify::EventKind;
+use notify::{Event, EventKind};
 use parking_lot::Mutex;
 use std::{
     collections::{BTreeMap, HashMap},
@@ -458,6 +458,16 @@ fn handle_poll_event(event: Result<notify::Event, notify::Error>) {
 }
 
 fn handle_event(mode: WatcherMode, event: Result<notify::Event, notify::Error>) {
+    if matches!(
+        event,
+        Ok(Event {
+            kind: EventKind::Access(_),
+            ..
+        })
+    ) {
+        return;
+    }
+
     log::trace!("global handle event for {mode:?}: {event:?}");
 
     let callbacks = {
@@ -472,9 +482,6 @@ fn handle_event(mode: WatcherMode, event: Result<notify::Event, notify::Error>)
 
     match event {
         Ok(event) => {
-            if matches!(event.kind, EventKind::Access(_)) {
-                return;
-            }
             for callback in callbacks {
                 callback(Ok(&event));
             }