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

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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




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