From: Wedson Almeida Filho <walmeida@xxxxxxxxxxxxx>
Allow Rust file systems to attach extra [typed] data to each inode. If
no data is needed, use the regular inode kmem_cache, otherwise we create
a new one.
Signed-off-by: Wedson Almeida Filho <walmeida@xxxxxxxxxxxxx>
---
rust/helpers.c | 7 +++
rust/kernel/fs.rs | 128 +++++++++++++++++++++++++++++++++++---
rust/kernel/mem_cache.rs | 2 -
samples/rust/rust_rofs.rs | 9 ++-
4 files changed, 131 insertions(+), 15 deletions(-)
diff --git a/rust/helpers.c b/rust/helpers.c
index bc19f3b7b93e..7b12a6d4cf5c 100644
--- a/rust/helpers.c
+++ b/rust/helpers.c
@@ -222,6 +222,13 @@ void rust_helper_kunmap_local(const void *vaddr)
}
EXPORT_SYMBOL_GPL(rust_helper_kunmap_local);
+void *rust_helper_alloc_inode_sb(struct super_block *sb,
+ struct kmem_cache *cache, gfp_t gfp)
+{
+ return alloc_inode_sb(sb, cache, gfp);
+}
+EXPORT_SYMBOL_GPL(rust_helper_alloc_inode_sb);
+
void rust_helper_i_uid_write(struct inode *inode, uid_t uid)
{
i_uid_write(inode, uid);
diff --git a/rust/kernel/fs.rs b/rust/kernel/fs.rs
index b1ad5c110dbb..b07203758674 100644
--- a/rust/kernel/fs.rs
+++ b/rust/kernel/fs.rs
@@ -9,8 +9,12 @@
use crate::error::{code::*, from_result, to_result, Error, Result};
use crate::folio::{LockedFolio, UniqueFolio};
use crate::types::{ARef, AlwaysRefCounted, Either, ForeignOwnable, Opaque, ScopeGuard};
-use crate::{bindings, init::PinInit, str::CStr, time::Timespec, try_pin_init, ThisModule};
-use core::{marker::PhantomData, marker::PhantomPinned, mem::ManuallyDrop, pin::Pin, ptr};
+use crate::{
+ bindings, container_of, init::PinInit, mem_cache::MemCache, str::CStr, time::Timespec,
+ try_pin_init, ThisModule,
+};
+use core::mem::{size_of, ManuallyDrop, MaybeUninit};
+use core::{marker::PhantomData, marker::PhantomPinned, pin::Pin, ptr};
use macros::{pin_data, pinned_drop};
#[cfg(CONFIG_BUFFER_HEAD)]
@@ -35,6 +39,9 @@ pub trait FileSystem {
/// Data associated with each file system instance (super-block).
type Data: ForeignOwnable + Send + Sync;
+ /// Type of data associated with each inode.
+ type INodeData: Send + Sync;
+
/// The name of the file system type.
const NAME: &'static CStr;
@@ -165,6 +172,7 @@ fn try_from(v: u32) -> Result<Self> {
pub struct Registration {
#[pin]
fs: Opaque<bindings::file_system_type>,
+ inode_cache: Option<MemCache>,
#[pin]
_pin: PhantomPinned,
}
@@ -182,6 +190,14 @@ impl Registration {
pub fn new<T: FileSystem + ?Sized>(module: &'static ThisModule) -> impl PinInit<Self, Error> {
try_pin_init!(Self {
_pin: PhantomPinned,
+ inode_cache: if size_of::<T::INodeData>() == 0 {
+ None
+ } else {
+ Some(MemCache::try_new::<INodeWithData<T::INodeData>>(
+ T::NAME,
+ Some(Self::inode_init_once_callback::<T>),
+ )?)
+ },
fs <- Opaque::try_ffi_init(|fs_ptr: *mut bindings::file_system_type| {
// SAFETY: `try_ffi_init` guarantees that `fs_ptr` is valid for write.
unsafe { fs_ptr.write(bindings::file_system_type::default()) };
@@ -239,6 +255,16 @@ pub fn new<T: FileSystem + ?Sized>(module: &'static ThisModule) -> impl PinInit<
unsafe { T::Data::from_foreign(ptr) };
}
}
+
+ unsafe extern "C" fn inode_init_once_callback<T: FileSystem + ?Sized>(
+ outer_inode: *mut core::ffi::c_void,
+ ) {
+ let ptr = outer_inode.cast::<INodeWithData<T::INodeData>>();
+
+ // SAFETY: This is only used in `new`, so we know that we have a valid `INodeWithData`
+ // instance whose inode part can be initialised.
+ unsafe { bindings::inode_init_once(ptr::addr_of_mut!((*ptr).inode)) };
+ }
}
#[pinned_drop]
@@ -280,6 +306,15 @@ pub fn super_block(&self) -> &SuperBlock<T> {
unsafe { &*(*self.0.get()).i_sb.cast() }
}
+ /// Returns the data associated with the inode.
+ pub fn data(&self) -> &T::INodeData {
+ let outerp = container_of!(self.0.get(), INodeWithData<T::INodeData>, inode);
+ // SAFETY: `self` is guaranteed to be valid by the existence of a shared reference
+ // (`&self`) to it. Additionally, we know `T::INodeData` is always initialised in an
+ // `INode`.
+ unsafe { &*(*outerp).data.as_ptr() }
+ }
+
/// Returns the size of the inode contents.
pub fn size(&self) -> i64 {
// SAFETY: `self` is guaranteed to be valid by the existence of a shared reference.
@@ -300,15 +335,29 @@ unsafe fn dec_ref(obj: ptr::NonNull<Self>) {
}
}
+struct INodeWithData<T> {
+ data: MaybeUninit<T>,
+ inode: bindings::inode,
+}
+
/// An inode that is locked and hasn't been initialised yet.
#[repr(transparent)]
pub struct NewINode<T: FileSystem + ?Sized>(ARef<INode<T>>);
impl<T: FileSystem + ?Sized> NewINode<T> {
/// Initialises the new inode with the given parameters.
- pub fn init(self, params: INodeParams) -> Result<ARef<INode<T>>> {
- // SAFETY: This is a new inode, so it's safe to manipulate it mutably.
- let inode = unsafe { &mut *self.0 .0.get() };
+ pub fn init(self, params: INodeParams<T::INodeData>) -> Result<ARef<INode<T>>> {
+ let outerp = container_of!(self.0 .0.get(), INodeWithData<T::INodeData>, inode);
+
+ // SAFETY: This is a newly-created inode. No other references to it exist, so it is
+ // safe to mutably dereference it.
+ let outer = unsafe { &mut *outerp.cast_mut() };
+
+ // N.B. We must always write this to a newly allocated inode because the free callback
+ // expects the data to be initialised and drops it.
+ outer.data.write(params.value);
+
+ let inode = &mut outer.inode;
let mode = match params.typ {
INodeType::Dir => {
@@ -424,7 +473,7 @@ pub enum INodeType {
/// Required inode parameters.
///
/// This is used when creating new inodes.
-pub struct INodeParams {
+pub struct INodeParams<T> {
/// The access mode. It's a mask that grants execute (1), write (2) and read (4) access to
/// everyone, the owner group, and the owner.
pub mode: u16,
@@ -459,6 +508,9 @@ pub struct INodeParams {
/// Last access time.
pub atime: Timespec,
+
+ /// Value to attach to this node.
+ pub value: T,
}
/// A file system super block.
@@ -735,8 +787,12 @@ impl<T: FileSystem + ?Sized> Tables<T> {
}
const SUPER_BLOCK: bindings::super_operations = bindings::super_operations {
- alloc_inode: None,
- destroy_inode: None,
+ alloc_inode: if size_of::<T::INodeData>() != 0 {
+ Some(Self::alloc_inode_callback)
+ } else {
+ None
+ },
+ destroy_inode: Some(Self::destroy_inode_callback),
free_inode: None,
dirty_inode: None,
write_inode: None,
@@ -766,6 +822,61 @@ impl<T: FileSystem + ?Sized> Tables<T> {
shutdown: None,
};
+ unsafe extern "C" fn alloc_inode_callback(
+ sb: *mut bindings::super_block,
+ ) -> *mut bindings::inode {
+ // SAFETY: The callback contract guarantees that `sb` is valid for read.
+ let super_type = unsafe { (*sb).s_type };
+
+ // SAFETY: This callback is only used in `Registration`, so `super_type` is necessarily
+ // embedded in a `Registration`, which is guaranteed to be valid because it has a
+ // superblock associated to it.
+ let reg = unsafe { &*container_of!(super_type, Registration, fs) };
+
+ // SAFETY: `sb` and `cache` are guaranteed to be valid by the callback contract and by
+ // the existence of a superblock respectively.
+ let ptr = unsafe {
+ bindings::alloc_inode_sb(sb, MemCache::ptr(®.inode_cache), bindings::GFP_KERNEL)
+ }
+ .cast::<INodeWithData<T::INodeData>>();
+ if ptr.is_null() {
+ return ptr::null_mut();
+ }
+ ptr::addr_of_mut!((*ptr).inode)
+ }
+
+ unsafe extern "C" fn destroy_inode_callback(inode: *mut bindings::inode) {
+ // SAFETY: By the C contract, `inode` is a valid pointer.
+ let is_bad = unsafe { bindings::is_bad_inode(inode) };
+
+ // SAFETY: The inode is guaranteed to be valid by the callback contract. Additionally, the
+ // superblock is also guaranteed to still be valid by the inode existence.
+ let super_type = unsafe { (*(*inode).i_sb).s_type };
+
+ // SAFETY: This callback is only used in `Registration`, so `super_type` is necessarily
+ // embedded in a `Registration`, which is guaranteed to be valid because it has a
+ // superblock associated to it.
+ let reg = unsafe { &*container_of!(super_type, Registration, fs) };
+ let ptr = container_of!(inode, INodeWithData<T::INodeData>, inode).cast_mut();
+
+ if !is_bad {
+ // SAFETY: The code either initialises the data or marks the inode as bad. Since the
+ // inode is not bad, the data is initialised, and thus safe to drop.
+ unsafe { ptr::drop_in_place((*ptr).data.as_mut_ptr()) };
+ }
+
+ if size_of::<T::INodeData>() == 0 {
+ // SAFETY: When the size of `INodeData` is zero, we don't use a separate mem_cache, so
+ // it is allocated from the regular mem_cache, which is what `free_inode_nonrcu` uses
+ // to free the inode.
+ unsafe { bindings::free_inode_nonrcu(inode) };
+ } else {
+ // The callback contract guarantees that the inode was previously allocated via the
+ // `alloc_inode_callback` callback, so it is safe to free it back to the cache.
+ unsafe { bindings::kmem_cache_free(MemCache::ptr(®.inode_cache), ptr.cast()) };
+ }
+ }
+
unsafe extern "C" fn statfs_callback(
dentry: *mut bindings::dentry,
buf: *mut bindings::kstatfs,
@@ -1120,6 +1231,7 @@ fn init(module: &'static ThisModule) -> impl PinInit<Self, Error> {
/// struct MyFs;
/// impl fs::FileSystem for MyFs {
/// type Data = ();
+/// type INodeData =();
/// const NAME: &'static CStr = c_str!("myfs");
/// fn super_params(_: &NewSuperBlock<Self>) -> Result<SuperParams<Self::Data>> {
/// todo!()
diff --git a/rust/kernel/mem_cache.rs b/rust/kernel/mem_cache.rs
index 05e5f2bc9781..bf6ce2d2d3e1 100644
--- a/rust/kernel/mem_cache.rs
+++ b/rust/kernel/mem_cache.rs
@@ -20,7 +20,6 @@ impl MemCache {
/// Allocates a new `kmem_cache` for type `T`.
///
/// `init` is called by the C code when entries are allocated.
- #[allow(dead_code)]
pub(crate) fn try_new<T>(
name: &'static CStr,
init: Option<unsafe extern "C" fn(*mut core::ffi::c_void)>,
@@ -43,7 +42,6 @@ pub(crate) fn try_new<T>(
/// Returns the pointer to the `kmem_cache` instance, or null if it's `None`.
///
/// This is a helper for functions like `alloc_inode_sb` where the cache is optional.
- #[allow(dead_code)]
pub(crate) fn ptr(c: &Option<Self>) -> *mut bindings::kmem_cache {
match c {
Some(m) => m.ptr.as_ptr(),
diff --git a/samples/rust/rust_rofs.rs b/samples/rust/rust_rofs.rs
index 093425650f26..dfe745439842 100644
--- a/samples/rust/rust_rofs.rs
+++ b/samples/rust/rust_rofs.rs
@@ -53,6 +53,7 @@ struct Entry {
struct RoFs;
impl fs::FileSystem for RoFs {
type Data = ();
+ type INodeData = &'static Entry;
const NAME: &'static CStr = c_str!("rust-fs");
fn super_params(_sb: &NewSuperBlock<Self>) -> Result<SuperParams<Self::Data>> {
@@ -79,6 +80,7 @@ fn init_root(sb: &SuperBlock<Self>) -> Result<ARef<INode<Self>>> {
atime: UNIX_EPOCH,
ctime: UNIX_EPOCH,
mtime: UNIX_EPOCH,
+ value: &ENTRIES[0],
}),
}
}
@@ -122,6 +124,7 @@ fn lookup(parent: &INode<Self>, name: &[u8]) -> Result<ARef<INode<Self>>> {
atime: UNIX_EPOCH,
ctime: UNIX_EPOCH,
mtime: UNIX_EPOCH,
+ value: e,
}),
};
}
@@ -131,11 +134,7 @@ fn lookup(parent: &INode<Self>, name: &[u8]) -> Result<ARef<INode<Self>>> {
}
fn read_folio(inode: &INode<Self>, mut folio: LockedFolio<'_>) -> Result {
- let data = match inode.ino() {
- 2 => ENTRIES[2].contents,
- 3 => ENTRIES[3].contents,
- _ => return Err(EINVAL),
- };
+ let data = inode.data().contents;
let pos = usize::try_from(folio.pos()).unwrap_or(usize::MAX);
let copied = if pos >= data.len() {
--
2.34.1
