mirror of
https://github.com/rclone/rclone.git
synced 2024-12-03 22:12:02 +01:00
61 lines
2.1 KiB
Markdown
61 lines
2.1 KiB
Markdown
|
|
||
|
|
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.
|