macfuse macfuse-5.1.0

General

• Update build process to use Xcode 26.1 (macOS 26.1 SDK)

• Update demo file systems

  • Update LoopbackFS demo file systems and add a libfuse3 variant (LoopbackFS-libfuse3-C)
  • Add new HelloFS demo file system (HelloFS-Framework-Swift). It serves as a minimal "Hello World" example — in just 40 lines of code.
  • For more information, see the demo repository.

Kernel Extension (Kernel Backend)

• Update kernel extension to version 5.1.0

• Add support for the VNOP_MONITOR file system callback

  The VNOP_MONITOR callback is available since macOS 15 and notifies file systems when the number of watchers for a file system item changes. This allows distributed file systems to subscribe only to events for items that are actively being watched, improving efficiency and reducing unnecessary event handling.

  • When the VNOP_MONITOR callback is invoked, the kernel extension sends a FUSE_MONITOR message (struct fuse_monitor_in) to the file system server running in user space
  • The FUSE_MONITOR_BEGIN flag is set when a new watcher starts monitoring the item
  • The FUSE_MONITOR_END flag is set when a watcher stops monitoring the item

• Fix a bug in VNOP_LINK that can cause a deadlock in case a file system uses the same nodeid to represent both the original file system item and its link. In this case, trying to lock the link in VNOP_LINK resulted in a deadlock. For more information, see macfuse/macfuse#1120.

• Fix a bug in VNOP_MNOMAP that can cause a deadlock. The VNOP_WRITE callback might end up calling the VNOP_MNOMAP callback. Attempting to lock the already locked file system item in the VNOP_MNOMAP callback caused the deadlock.

• Fix f_mntfromname (fsname mount option) being truncated at 90 bytes. f_mntfromname supports names of up to 1024 bytes (including the terminating \0 character). For more information, see macfuse/macfuse#1123.

FSModule (FSKit Backend)

• Add support for mounting "non-local" volumes (typically distributed file systems) on macOS 26. Mounting "local" volumes (typically physically attached storage) is supported on macOS 15.4 and later macOS versions.

• Add support for mount option local. macOS is more aggressive in dealing with "local" volumes. Treat this option as experimental.

• Add support for mount option volname=NAME, where NAME is a string. You can use the volname option to specify a name for the volume being mounted.

libfuse

• Add new monitor callback handler and implement support for the new FUSE_MONITOR message. For more information, see "Kernel Extension".

libfuse3

• Add support for mounting file systems using the FSKit backend. By default, the kernel backend is used to mount volumes. When specifying the mount option -o backend=fskit, libfuse3 will use the FSKit backend to mount the file system. For more information, see FUSE Backends.

• Add new monitor callback handler and implement support for the new FUSE_MONITOR message. For more information, see "Kernel Extension".

• Add utimens API extension for macOS. When FUSE_DARWIN_ENABLE_EXTENSIONS is set to 1 , the utimens handler is called with three time stamps — the file's access, modification, and backup time stamps. By default, the handler is called with the file's access and modification time stamps.

• Fix a bug in the statfs API extension for macOS and add missing fuse_lib_statfs$DARWIN() handler

• Fix a bug in the threadid module that prevented several file system callback handlers from being invoked when using the module

• Adapt fuse_clone_chan_fd_default() for macOS. On macOS, there is no need to associate new FUSE device file descriptors with the original ones.

• Rename crtime (creation time) btime (birth time). This change does not affect ABI stability, but it requires code updates when compiling a file system with this release and the macOS API extensions being enabled.

Framework

• Improve Swift support

  • Enable Clang module support to improve interoperability with Swift
  • Drop the GM type name prefix in Swift
  • Make UserFileSystem.MoveOptions more idiomatic for Swift
  • Add FileAttributeKey extension defining additional framework-specific attribute keys
  • These changes have no affect on ABI stability, but they require code updates when compiling a file system with this release

• Turn NSObject categories UserFileSystemLifecycle, UserFileSystemOperations, and UserFileSystemResourceForks into actual protocols

• Remove unsupported exchangedata() callback handler. exchangedata() has been superseded by renamex_np() and has been unsupported since macOS 11. This change deprecates the corresponding delegate method.

  - (BOOL)exchangeDataOfItemAtPath:(NSString *)path
                    withItemAtPath:(NSString *)otherPath
                             error:(NSError * _Nullable * _Nonnull)error
  

System Settings

• Fix a layout bug on macOS 26 and modernize layout