From a91a95edbc945a5a6a2c020e64fab982c2dc7225 Mon Sep 17 00:00:00 2001
From: Jake Bailey <5341706+jakebailey@users.noreply.github.com>
Date: Fri, 6 Nov 2026 22:35:02 +0000
Subject: [PATCH] Fall back to inotify when fanotify rejects mounts with EXDEV
 (#65325)

---
 tsc/internal/fswatch/fanotify_linux.go      |  2 +-
 tsc/internal/fswatch/fanotify_linux_test.go | 16 +++++++++-------
 2 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/tsc/internal/fswatch/fanotify_linux.go b/tsc/internal/fswatch/fanotify_linux.go
index 899e64ad3051b..677c69cc6f67c 100644
--- a/tsc/internal/fswatch/fanotify_linux.go
+++ b/tsc/internal/fswatch/fanotify_linux.go
@@ -366,7 +366,7 @@ func (b *fanotifyBackend) markDir(w *dirWatch, path string, markPath string) err
 }
 
 func maybeWrapUnsupportedFilesystem(err error) error {
-	if errors.Is(err, unix.EOPNOTSUPP) || errors.Is(err, unix.ENOTSUP) || errors.Is(err, unix.ENODEV) {
+	if errors.Is(err, unix.EOPNOTSUPP) || errors.Is(err, unix.ENOTSUP) || errors.Is(err, unix.ENODEV) || errors.Is(err, unix.EXDEV) {
 		return fmt.Errorf("%w: %w", err, ErrFilesystemUnsupported)
 	}
 	return err
diff --git a/tsc/internal/fswatch/fanotify_linux_test.go b/tsc/internal/fswatch/fanotify_linux_test.go
index 7dfe9f5825bbb..0bf7672c36754 100644
--- a/tsc/internal/fswatch/fanotify_linux_test.go
+++ b/tsc/internal/fswatch/fanotify_linux_test.go
@@ -127,13 +127,15 @@ func TestLinuxFanotifyMaybeWrapUnsupportedFilesystem(t *testing.T) {
 	// Errnos that indicate the filesystem cannot support fanotify FID-based
 	// watching are tagged with ErrFilesystemUnsupported so higher layers can
 	// fall back to inotify (issue #63646).
-	for _, errno := range []error{unix.EOPNOTSUPP, unix.ENODEV} {
-		wrapped := maybeWrapUnsupportedFilesystem(fmt.Errorf("name_to_handle_at: %w", errno))
-		if !errors.Is(wrapped, ErrFilesystemUnsupported) {
-			t.Errorf("expected %v to be tagged ErrFilesystemUnsupported", errno)
-		}
-		if !errors.Is(wrapped, errno) {
-			t.Errorf("expected wrapped error to still unwrap to %v", errno)
+	for _, errno := range []error{unix.EOPNOTSUPP, unix.ENODEV, unix.EXDEV} {
+		for _, err := range []error{errno, fmt.Errorf("name_to_handle_at: %w", errno)} {
+			wrapped := maybeWrapUnsupportedFilesystem(err)
+			if !errors.Is(wrapped, ErrFilesystemUnsupported) {
+				t.Errorf("expected %v to be tagged ErrFilesystemUnsupported", err)
+			}
+			if !errors.Is(wrapped, errno) {
+				t.Errorf("expected wrapped error to still unwrap to %v", errno)
+			}
 		}
 	}