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

[Danilo Krummrich]

Hi Wedson,

On 5/14/24 15:16, Wedson Almeida Filho wrote:
> 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

This branch indicates that this patch series might have a few more dependencies
that are not upstream yet, e.g. [1].

Do you intend to send them in a separate series (soon)? In case they were already
submitted somewhere and I just failed to find them, please be so kind an provide
me with a pointer.

[1] https://github.com/wedsonaf/linux/commit/96ef0376887f4194ebad608f9943eb41108cf255

- Danilo

> ---
>
> 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@xxxxxxxxx/
>
> ---
>
> 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