From ae6468b4b9debaff88c91a3fa02d0a010b7a6322 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Pawe=C5=82=20Gronowski?= <pawel.gronowski@docker.com>
Date: Thu, 18 Jan 2024 14:23:32 +0100
Subject: [PATCH] c8d/mount: Use ref-counted mounter by default
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All commonly used filesystems should use ref-counted mounter, so make it
the default instead of having to whitelist them.

Signed-off-by: Paweł Gronowski <pawel.gronowski@docker.com>
---
 daemon/snapshotter/mount.go | 38 +++++++++----------------------------
 1 file changed, 9 insertions(+), 29 deletions(-)

diff --git a/daemon/snapshotter/mount.go b/daemon/snapshotter/mount.go
index 23c74baa74..68c727174f 100644
--- a/daemon/snapshotter/mount.go
+++ b/daemon/snapshotter/mount.go
@@ -13,9 +13,6 @@ import (
 	"github.com/moby/sys/mountinfo"
 )
 
-// List of known filesystems that can't be re-mounted or have shared layers
-var refCountedFileSystems = []string{"fuse-overlayfs", "overlayfs", "stargz", "zfs"}
-
 // Mounter handles mounting/unmounting things coming in from a snapshotter
 // with optional reference counting if needed by the filesystem
 type Mounter interface {
@@ -27,34 +24,17 @@ type Mounter interface {
 	Mounted(containerID string) (string, error)
 }
 
-// inSlice tests whether a string is contained in a slice of strings or not.
-// Comparison is case sensitive
-func inSlice(slice []string, s string) bool {
-	for _, ss := range slice {
-		if s == ss {
-			return true
-		}
-	}
-	return false
-}
-
 // NewMounter creates a new mounter for the provided snapshotter
-func NewMounter(home string, snapshotter string, idMap idtools.IdentityMapping) Mounter {
-	mnter := mounter{
-		home:        home,
-		snapshotter: snapshotter,
-		idMap:       idMap,
+func NewMounter(home string, snapshotter string, idMap idtools.IdentityMapping) *refCountMounter {
+	return &refCountMounter{
+		base: mounter{
+			home:        home,
+			snapshotter: snapshotter,
+			idMap:       idMap,
+		},
+		rc:     graphdriver.NewRefCounter(checker()),
+		locker: locker.New(),
 	}
-
-	if inSlice(refCountedFileSystems, snapshotter) {
-		return &refCountMounter{
-			base:   mnter,
-			rc:     graphdriver.NewRefCounter(checker()),
-			locker: locker.New(),
-		}
-	}
-
-	return &mnter
 }
 
 type refCountMounter struct {