rclone/vendor/github.com/hanwen/go-fuse/v2/fs

Objective

A high-performance FUSE API that minimizes pitfalls with writing correct filesystems.

Decisions

• Nodes contain references to their children. This is useful because most filesystems will need to construct tree-like structures.

• Nodes contain references to their parents. As a result, we can derive the path for each Inode, and there is no need for a separate PathFS.

• Nodes can be "persistent", meaning their lifetime is not under control of the kernel. This is useful for constructing FS trees in advance, rather than driven by LOOKUP.

• The NodeID for FS tree node must be defined on creation and are immutable. By contrast, reusing NodeIds (eg. rsc/bazil FUSE, as well as old go-fuse/fuse/nodefs) needs extra synchronization to avoid races with notify and FORGET, and makes handling the inode Generation more complicated.

• The mode of an Inode is defined on creation. Files cannot change type during their lifetime. This also prevents the common error of forgetting to return the filetype in Lookup/GetAttr.

• The NodeID (used for communicating with kernel) is equal to Attr.Ino (value shown in Stat and Lstat return values.).

• No global treelock, to ensure scalability.

• Support for hard links. libfuse doesn't support this in the high-level API. Extra care for race conditions is needed when looking up the same file through different paths.

• do not issue Notify{Entry,Delete} as part of AddChild/RmChild/MvChild: because NodeIDs are unique and immutable, there is no confusion about which nodes are invalidated, and the notification doesn't have to happen under lock.

• Directory reading uses the DirStream. Semantics for rewinding directory reads, and adding files after opening (but before reading) are handled automatically. No support for directory seeks.

• Method names are based on syscall names. Where there is no syscall (eg. "open directory"), we bias towards writing everything together (Opendir)

To do/To decide

• Symlink []byte vs string.