From ad042e5c9de540ec3ea61188e950a6c955f00938 Mon Sep 17 00:00:00 2001
From: Ben Kunkle <ben@zed.dev>
Date: Tue, 19 May 2026 16:14:50 -0400
Subject: [PATCH] fs: Don't opt into polling for `virtiofs` based file systems
 (#57184)

Technically we don't know if a `virtiofs` file system supports `inotify`
or not, but it seems like it's mostly used inside virtual machines
provided by:
- OrbStack (`inotify` works)
- Docker Desktop (`inotify` works)
- Lima (`inotify` works with flag)
- Colima (`inotify` works with flag)
- QEMU + virtiofs setup (`inotify` doesn't work without extra setup)

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)
- [x] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable

Closes #57103

Closes FR-9

Release Notes:

- Fixed an issue where file system watching would default to the polling
backend inside of `OrbStack` VMs on MacOS
---
 crates/fs/src/fs_watcher.rs | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/crates/fs/src/fs_watcher.rs b/crates/fs/src/fs_watcher.rs
index 2c8078f1324..34758afe044 100644
--- a/crates/fs/src/fs_watcher.rs
+++ b/crates/fs/src/fs_watcher.rs
@@ -235,6 +235,10 @@ fn detect_requires_poll_watcher_linux(path: &Path) -> bool {
     const FUSE_SUPER_MAGIC: u64 = 0x6573_5546;
 
     let fs_type = (stat.f_type as u64) & 0xFFFF_FFFF;
+    if fs_type == FUSE_SUPER_MAGIC && is_virtiofs(path) {
+        return false;
+    }
+
     if fs_type == V9FS_MAGIC
         || fs_type == NFS_SUPER_MAGIC
         || fs_type == CIFS_MAGIC
@@ -261,6 +265,37 @@ fn detect_requires_poll_watcher_linux(path: &Path) -> bool {
     false
 }
 
+#[cfg(target_os = "linux")]
+fn is_virtiofs(path: &Path) -> bool {
+    let Ok(mountinfo) = std::fs::read_to_string("/proc/self/mountinfo") else {
+        return false;
+    };
+
+    let mut best_mount = None;
+    for line in mountinfo.lines() {
+        let fields = line.split(' ').collect::<Vec<_>>();
+        let Some(separator) = fields.iter().position(|field| *field == "-") else {
+            continue;
+        };
+        let (Some(mount_point), Some(fs_type)) = (fields.get(4), fields.get(separator + 1)) else {
+            continue;
+        };
+
+        let mount_point = mount_point
+            .replace("\\040", " ")
+            .replace("\\011", "\t")
+            .replace("\\012", "\n")
+            .replace("\\134", "\\");
+        if path.starts_with(&mount_point)
+            && best_mount.is_none_or(|(length, _)| mount_point.len() > length)
+        {
+            best_mount = Some((mount_point.len(), *fs_type));
+        }
+    }
+
+    best_mount.is_some_and(|(_, fs_type)| fs_type == "virtiofs" || fs_type == "fuse.virtiofs")
+}
+
 #[cfg(target_os = "linux")]
 fn is_wsl_drvfs_path(path: &Path) -> bool {
     if std::env::var_os("WSL_DISTRO_NAME").is_none() {