this branch contains Wedson's work on VFS in Rust [0,1], rebased onto a current rust-next

[0] https://lore.kernel.org/rust-for-linux/[email protected]/

[1] https://github.com/wedsonaf/linux/tree/vfs-v2

some notes on what was changed during rebase:

• a672c7393a49 rust: introduce InPlaceModule
• 9add409b5346 samples: rust: add in-place initialisation sample
  • old Vec -> KVec
• 96ef0376887f rust: init: introduce Opaque::try_ffi_init
• 6fe57e020b4d rust: alloc: introduce resize and resize_with
  • skipped
  • VecExt has been removed in 405966efc789888c3e1a53cd09d2c2b338064438
  • VecExt::resize is already implemented as Vec::extend_with (thoughextend_with takes number of elements to add rather than new len)
  • VecExt::resize_with just takes a fn instead of a value to fill with
• 9eed0fe3ec36 rust: alloc: introduce new_slice and new_uninit_slice
  • BoxExt has been removed in e8c6ccdbcaaf31f26c0fffd4073edd0b0147cdc6
  • Box<MaybeUninit<T>>::assume_init() had to be implemented for Box<[MaybeUninit<T>]> as well
• ecc54b2bbd08 rust: kernel: update offset_of to not require unsafe blocks
• 300ab577d33e rust: alloc: add GFP_NOFS
• 98f6c0bb7175 rust: time: introduce time module
  • also adds Timespec::seconds, Timespec::nanoseconds, which are now required for "rust: fs: introduce FileSystem::init_root"
• 475d59e88d66 rust: types: add little-endian type
• 695c58302286 rust: types: introduce FromBytes trait
• d74848eb4d8c rust: mem_cache: introduce MemCache
• f60e1c65ab72 rust: str: modify CString to use Box<[u8]> instead of Vec
• 802339f9b993 rust: str: implement ForeignOwnable for CString
• c5f5fc72c583 rust: str: implement TryFrom<Box<[u8]>> for CString
• 0d384e0ea01a rust: str: add conversion from &[u8] to CString
• 8dca84ec304a rust: user: add helper for copy_to_user
  • skipped; already implemented (uaccess::UserSliceWriter::write instead of user::Writer::write_all)
• 64c812a93704 rust: types: introduce Locked type
• 4a2a0b0247d9 rust: block: introduce block::Device
  • empty block module already exists
• 5b9c88f6229c rust: file: add Rust abstraction for struct file
• 183ea65d1fcd rust: error: add errors used in file systems
• 79c843449bdc rust: fs: add registration/unregistration of file systems
• be077708fb7e rust: fs: introduce the module_fs macro
• 28204e1530ef samples: rust: add initial ro file system sample
• bee3cb6a63b0 rust: fs: introduce FileSystem::fill_super
• f631cc27f1cb rust: fs: introduce INode<T>
  • Device::inode: block_device.bd_inode has been removed (203c1ce0bb063d1620698e39637b64f2d09c1368); use bdev_inode.vfs_inode instead (like df65f1660b6141f0b051d2439cc99222a6ae865b does)
  • adds struct bdev_inode to bindings_helper.h
• eb0c65e362a3 rust: fs: introduce DEntry<T>
• aae9bc801c8b rust: fs: introduce FileSystem::init_root
  • inodes now store time sec/nsec separately; added Timespec::seconds, Timespec::nanoseconds (3aa63a569c64e708df547a8913c84e64a06e7853)
• a0e1f1c0832b rust: file: move kernel::file to kernel::fs::file
• 30e88c831ef9 rust: fs: generalise File for different file systems
• e0bc2ed31f8e rust: fs: add empty file operations
  • file_operations.mmap_supported_flags has been removed; file_operations.fop_flags has been added (210a03c9d51aa0e6e6f06980116e3256da8d4c48)
• 40089b3eb6c0 rust: fs: introduce file::Operations::read_dir
• 5dc2f72eef50 rust: fs: introduce file::Operations::seek
• adfb28ec5cee rust: fs: introduce file::Operations::read
• beee27f2516c rust: fs: add empty inode operations
  • compilation fails already in original commit (?) since inode Ops field 0 is never read
• fe47514c8ae0 rust: fs: introduce inode::Operations::lookup
• 6e278ed7b428 rust: folio: introduce basic support for folios
• 6e5f4e38240e rust: fs: add empty address space operations
• b971ade00965 rust: fs: introduce address_space::Operations::read_folio
• 31af11a7e054 rust: fs: introduce FileSystem::read_xattr
• 35b2b956c1a8 rust: fs: introduce FileSystem::statfs
• bc914f6b2431 rust: fs: introduce more inode types
  • add helpers/{delayed_call,kdev_t}.c
• 28e8d78ba103 rust: fs: add per-superblock data
• bc4f26414cf7 rust: fs: allow file systems backed by a block device
• e296beaeceac rust: fs: allow per-inode data
• c2e8edfe650d rust: fs: export file type from mode constants
• 4a8a26b867be rust: fs: allow populating i_lnk
• b682a749d3f2 rust: fs: add iomap module
• 1a4faa0efe06 rust: fs: add memalloc_nofs support
• 54b312e1340d tarfs: introduce tar fs
  • Vec -> KVec, Box -> KBox
  • kernel::user::Writer -> kernel::uaccess::UserSliceWriter
  • name.resize(name_len, ...) -> name.extend_with(name_len - name.len(), ...)
• 5bb3588bb138 WIP: fs: ext2: add rust ro ext2 implementation
  • Vec -> KVec, Box -> KBox
  • kernel::user::Writer -> kernel::uaccess::UserSliceWriter