[RFC PATCH v2 00/30] Rust abstractions for VFS

[Wedson Almeida Filho <wedsonaf@gmail.com>]

This series introduces Rust abstractions that allow read-only file systems to
be written in Rust.

There are three file systems implementations using these abstractions
abstractions: ext2, tarfs, and puzzlefs. The first two are part of this series.

Rust file system modules can be declared with the `module_fs` macro and are
required to implement the following functions (which are part of the
`FileSystem` trait):

    fn fill_super(
        sb: &mut SuperBlock<Self, sb::New>,
        mapper: Option<inode::Mapper>,
    ) -> Result<Self::Data>;

    fn init_root(sb: &SuperBlock<Self>) -> Result<dentry::Root<Self>>;

They can optionally implement the following:

    fn read_xattr(
        _dentry: &DEntry<Self>,
        _inode: &INode<Self>,
        _name: &CStr,
        _outbuf: &mut [u8],
    ) -> Result<usize>;

    fn statfs(_dentry: &DEntry<Self>) -> Result<Stat>;

They may also choose the type of the data they can attach to superblocks and/or
inodes.

Lastly, file systems can implement inode, file, and address space operations
and attach them to inodes when they're created, similar to how C does it. They
can get a ro address space operations table from an implementation of iomap
operations, to be used with generic ro file operations.

A git tree is available here:
    git://github.com/wedsonaf/linux.git vfs-v2

Web:
    https://github.com/wedsonaf/linux/commits/vfs-v2

---

Changes in v2:

- Rebased to latest rust-next tree
- Removed buffer heads
- Added iomap support
- Removed `_pin` field from `Registration` as it's not needed anymore
- Renamed sample filesystem to match the module's name
- Using typestate instead of a separate type for superblock/new-superblock
- Created separate submodules for superblocks, inodes, dentries, and files
- Split out operations from FileSystem to inode/file/address_space ops, similar to how C does it
- Removed usages of folio_set_error
- Removed UniqueFolio, for now reading blocks from devices via the pagecache
- Changed map() to return the entire folio if not in highmem
- Added support for unlocking the folio asynchronously
- Added `from_raw` to all new ref-counted types
- Added explicit types in calls to cast()
- Added typestate to folio
- Added support for implementing get_link
- Fixed data race when reading inode->i_state
- Added nofs scope support during allocation
- Link to v1: https://lore.kernel.org/rust-for-linux/20231018122518.128049-1-wedsonaf@gmail.com/

---

Wedson Almeida Filho (30):
  rust: fs: add registration/unregistration of file systems
  rust: fs: introduce the `module_fs` macro
  samples: rust: add initial ro file system sample
  rust: fs: introduce `FileSystem::fill_super`
  rust: fs: introduce `INode<T>`
  rust: fs: introduce `DEntry<T>`
  rust: fs: introduce `FileSystem::init_root`
  rust: file: move `kernel::file` to `kernel::fs::file`
  rust: fs: generalise `File` for different file systems
  rust: fs: add empty file operations
  rust: fs: introduce `file::Operations::read_dir`
  rust: fs: introduce `file::Operations::seek`
  rust: fs: introduce `file::Operations::read`
  rust: fs: add empty inode operations
  rust: fs: introduce `inode::Operations::lookup`
  rust: folio: introduce basic support for folios
  rust: fs: add empty address space operations
  rust: fs: introduce `address_space::Operations::read_folio`
  rust: fs: introduce `FileSystem::read_xattr`
  rust: fs: introduce `FileSystem::statfs`
  rust: fs: introduce more inode types
  rust: fs: add per-superblock data
  rust: fs: allow file systems backed by a block device
  rust: fs: allow per-inode data
  rust: fs: export file type from mode constants
  rust: fs: allow populating i_lnk
  rust: fs: add `iomap` module
  rust: fs: add memalloc_nofs support
  tarfs: introduce tar fs
  WIP: fs: ext2: add rust ro ext2 implementation

 fs/Kconfig                        |   2 +
 fs/Makefile                       |   2 +
 fs/rust-ext2/Kconfig              |  13 +
 fs/rust-ext2/Makefile             |   8 +
 fs/rust-ext2/defs.rs              | 173 +++++++
 fs/rust-ext2/ext2.rs              | 551 +++++++++++++++++++++
 fs/tarfs/Kconfig                  |  15 +
 fs/tarfs/Makefile                 |   8 +
 fs/tarfs/defs.rs                  |  80 +++
 fs/tarfs/tar.rs                   | 394 +++++++++++++++
 rust/bindings/bindings_helper.h   |  11 +
 rust/helpers.c                    | 182 +++++++
 rust/kernel/block.rs              |  10 +-
 rust/kernel/error.rs              |   8 +-
 rust/kernel/file.rs               | 251 ----------
 rust/kernel/folio.rs              | 305 ++++++++++++
 rust/kernel/fs.rs                 | 492 +++++++++++++++++++
 rust/kernel/fs/address_space.rs   |  90 ++++
 rust/kernel/fs/dentry.rs          | 136 ++++++
 rust/kernel/fs/file.rs            | 607 +++++++++++++++++++++++
 rust/kernel/fs/inode.rs           | 780 ++++++++++++++++++++++++++++++
 rust/kernel/fs/iomap.rs           | 281 +++++++++++
 rust/kernel/fs/sb.rs              | 194 ++++++++
 rust/kernel/lib.rs                |   6 +-
 rust/kernel/mem_cache.rs          |   2 -
 rust/kernel/user.rs               |   1 -
 samples/rust/Kconfig              |  10 +
 samples/rust/Makefile             |   1 +
 samples/rust/rust_rofs.rs         | 202 ++++++++
 scripts/generate_rust_analyzer.py |   2 +-
 30 files changed, 4555 insertions(+), 262 deletions(-)
 create mode 100644 fs/rust-ext2/Kconfig
 create mode 100644 fs/rust-ext2/Makefile
 create mode 100644 fs/rust-ext2/defs.rs
 create mode 100644 fs/rust-ext2/ext2.rs
 create mode 100644 fs/tarfs/Kconfig
 create mode 100644 fs/tarfs/Makefile
 create mode 100644 fs/tarfs/defs.rs
 create mode 100644 fs/tarfs/tar.rs
 delete mode 100644 rust/kernel/file.rs
 create mode 100644 rust/kernel/folio.rs
 create mode 100644 rust/kernel/fs.rs
 create mode 100644 rust/kernel/fs/address_space.rs
 create mode 100644 rust/kernel/fs/dentry.rs
 create mode 100644 rust/kernel/fs/file.rs
 create mode 100644 rust/kernel/fs/inode.rs
 create mode 100644 rust/kernel/fs/iomap.rs
 create mode 100644 rust/kernel/fs/sb.rs
 create mode 100644 samples/rust/rust_rofs.rs


base-commit: 183ea65d1fcd71039cf4d111a22d69c337bfd344
-- 
2.34.1