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Message-Id: <20240514131711.379322-16-wedsonaf@gmail.com>
Date: Tue, 14 May 2024 10:16:56 -0300
From: Wedson Almeida Filho <wedsonaf@...il.com>
To: Alexander Viro <viro@...iv.linux.org.uk>,
Christian Brauner <brauner@...nel.org>,
Matthew Wilcox <willy@...radead.org>,
Dave Chinner <david@...morbit.com>
Cc: Kent Overstreet <kent.overstreet@...il.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
linux-fsdevel@...r.kernel.org,
rust-for-linux@...r.kernel.org,
linux-kernel@...r.kernel.org,
Wedson Almeida Filho <walmeida@...rosoft.com>
Subject: [RFC PATCH v2 15/30] rust: fs: introduce `inode::Operations::lookup`
From: Wedson Almeida Filho <walmeida@...rosoft.com>
Allow Rust file systems to create inodes that are children of a
directory inode when they're looked up by name.
Signed-off-by: Wedson Almeida Filho <walmeida@...rosoft.com>
---
rust/kernel/error.rs | 1 -
rust/kernel/fs/dentry.rs | 1 -
rust/kernel/fs/inode.rs | 58 ++++++++++++++++++++++++-----
samples/rust/rust_rofs.rs | 77 +++++++++++++++++++++++++++++----------
4 files changed, 105 insertions(+), 32 deletions(-)
diff --git a/rust/kernel/error.rs b/rust/kernel/error.rs
index bb13bd4a7fa6..15628d2fa3b2 100644
--- a/rust/kernel/error.rs
+++ b/rust/kernel/error.rs
@@ -129,7 +129,6 @@ pub fn to_errno(self) -> core::ffi::c_int {
}
/// Returns the error encoded as a pointer.
- #[allow(dead_code)]
pub(crate) fn to_ptr<T>(self) -> *mut T {
// SAFETY: `self.0` is a valid error due to its invariant.
unsafe { bindings::ERR_PTR(self.0.into()) as *mut _ }
diff --git a/rust/kernel/fs/dentry.rs b/rust/kernel/fs/dentry.rs
index 6a36a48cd28b..c93debb70ea3 100644
--- a/rust/kernel/fs/dentry.rs
+++ b/rust/kernel/fs/dentry.rs
@@ -43,7 +43,6 @@ impl<T: FileSystem + ?Sized> DEntry<T> {
///
/// * `ptr` must be valid for at least the lifetime of the returned reference.
/// * `ptr` has the correct file system type, or `T` is [`super::UnspecifiedFS`].
- #[allow(dead_code)]
pub(crate) unsafe fn from_raw<'a>(ptr: *mut bindings::dentry) -> &'a Self {
// SAFETY: The safety requirements guarantee that the reference is and remains valid.
unsafe { &*ptr.cast::<Self>() }
diff --git a/rust/kernel/fs/inode.rs b/rust/kernel/fs/inode.rs
index 3d65b917af0e..c314d036c87e 100644
--- a/rust/kernel/fs/inode.rs
+++ b/rust/kernel/fs/inode.rs
@@ -6,9 +6,9 @@
//!
//! C headers: [`include/linux/fs.h`](srctree/include/linux/fs.h)
-use super::{file, sb::SuperBlock, FileSystem, Offset, UnspecifiedFS};
-use crate::error::Result;
-use crate::types::{ARef, AlwaysRefCounted, Lockable, Opaque};
+use super::{dentry, dentry::DEntry, file, sb::SuperBlock, FileSystem, Offset, UnspecifiedFS};
+use crate::error::{code::*, Result};
+use crate::types::{ARef, AlwaysRefCounted, Lockable, Locked, Opaque};
use crate::{bindings, block, time::Timespec};
use core::mem::ManuallyDrop;
use core::{marker::PhantomData, ptr};
@@ -22,6 +22,14 @@
pub trait Operations {
/// File system that these operations are compatible with.
type FileSystem: FileSystem + ?Sized;
+
+ /// Returns the inode corresponding to the directory entry with the given name.
+ fn lookup(
+ _parent: &Locked<&INode<Self::FileSystem>, ReadSem>,
+ _dentry: dentry::Unhashed<'_, Self::FileSystem>,
+ ) -> Result<Option<ARef<DEntry<Self::FileSystem>>>> {
+ Err(ENOTSUPP)
+ }
}
/// A node (inode) in the file index.
@@ -118,12 +126,7 @@ pub fn init(mut self, params: Params) -> Result<ARef<INode<T>>> {
// SAFETY: This is a new inode, so it's safe to manipulate it mutably.
let inode = unsafe { self.0.as_mut() };
let mode = match params.typ {
- Type::Dir => {
- // SAFETY: `simple_dir_inode_operations` never changes, it's safe to reference it.
- inode.i_op = unsafe { &bindings::simple_dir_inode_operations };
-
- bindings::S_IFDIR
- }
+ Type::Dir => bindings::S_IFDIR,
};
inode.i_mode = (params.mode & 0o777) | u16::try_from(mode)?;
@@ -148,6 +151,14 @@ pub fn init(mut self, params: Params) -> Result<ARef<INode<T>>> {
Ok(unsafe { ARef::from_raw(manual.0.cast::<INode<T>>()) })
}
+ /// Sets the inode operations on this new inode.
+ pub fn set_iops(&mut self, iops: Ops<T>) -> &mut Self {
+ // SAFETY: By the type invariants, it's ok to modify the inode.
+ let inode = unsafe { self.0.as_mut() };
+ inode.i_op = iops.0;
+ self
+ }
+
/// Sets the file operations on this new inode.
pub fn set_fops(&mut self, fops: file::Ops<T>) -> &mut Self {
// SAFETY: By the type invariants, it's ok to modify the inode.
@@ -221,7 +232,11 @@ pub const fn new<U: Operations<FileSystem = T> + ?Sized>() -> Self {
struct Table<T: Operations + ?Sized>(PhantomData<T>);
impl<T: Operations + ?Sized> Table<T> {
const TABLE: bindings::inode_operations = bindings::inode_operations {
- lookup: None,
+ lookup: if T::HAS_LOOKUP {
+ Some(Self::lookup_callback)
+ } else {
+ None
+ },
get_link: None,
permission: None,
get_inode_acl: None,
@@ -247,6 +262,29 @@ impl<T: Operations + ?Sized> Table<T> {
fileattr_get: None,
get_offset_ctx: None,
};
+
+ extern "C" fn lookup_callback(
+ parent_ptr: *mut bindings::inode,
+ dentry_ptr: *mut bindings::dentry,
+ _flags: u32,
+ ) -> *mut bindings::dentry {
+ // SAFETY: The C API guarantees that `parent_ptr` is a valid inode.
+ let parent = unsafe { INode::from_raw(parent_ptr) };
+
+ // SAFETY: The C API guarantees that `dentry_ptr` is a valid dentry.
+ let dentry = unsafe { DEntry::from_raw(dentry_ptr) };
+
+ // SAFETY: The C API guarantees that the inode's rw semaphore is locked at least in
+ // read mode. It does not expect callees to unlock it, so we make the locked object
+ // manually dropped to avoid unlocking it.
+ let locked = ManuallyDrop::new(unsafe { Locked::new(parent) });
+
+ match T::lookup(&locked, dentry::Unhashed(dentry)) {
+ Err(e) => e.to_ptr(),
+ Ok(None) => ptr::null_mut(),
+ Ok(Some(ret)) => ManuallyDrop::new(ret).0.get(),
+ }
+ }
}
Self(&Table::<U>::TABLE, PhantomData)
}
diff --git a/samples/rust/rust_rofs.rs b/samples/rust/rust_rofs.rs
index f4be5908369c..2a87e524e0e1 100644
--- a/samples/rust/rust_rofs.rs
+++ b/samples/rust/rust_rofs.rs
@@ -2,9 +2,11 @@
//! Rust read-only file system sample.
-use kernel::fs::{dentry, file, file::File, inode, inode::INode, sb::SuperBlock, Offset};
+use kernel::fs::{
+ dentry, dentry::DEntry, file, file::File, inode, inode::INode, sb::SuperBlock, Offset,
+};
use kernel::prelude::*;
-use kernel::{c_str, fs, time::UNIX_EPOCH, types::Either, types::Locked, user};
+use kernel::{c_str, fs, time::UNIX_EPOCH, types::ARef, types::Either, types::Locked, user};
kernel::module_fs! {
type: RoFs,
@@ -39,8 +41,36 @@ struct Entry {
];
const DIR_FOPS: file::Ops<RoFs> = file::Ops::new::<RoFs>();
+const DIR_IOPS: inode::Ops<RoFs> = inode::Ops::new::<RoFs>();
struct RoFs;
+
+impl RoFs {
+ fn iget(sb: &SuperBlock<Self>, e: &'static Entry) -> Result<ARef<INode<Self>>> {
+ let mut new = match sb.get_or_create_inode(e.ino)? {
+ Either::Left(existing) => return Ok(existing),
+ Either::Right(new) => new,
+ };
+
+ match e.etype {
+ inode::Type::Dir => new.set_iops(DIR_IOPS).set_fops(DIR_FOPS),
+ };
+
+ new.init(inode::Params {
+ typ: e.etype,
+ mode: 0o555,
+ size: ENTRIES.len().try_into()?,
+ blocks: 1,
+ nlink: 2,
+ uid: 0,
+ gid: 0,
+ atime: UNIX_EPOCH,
+ ctime: UNIX_EPOCH,
+ mtime: UNIX_EPOCH,
+ })
+ }
+}
+
impl fs::FileSystem for RoFs {
const NAME: &'static CStr = c_str!("rust_rofs");
@@ -50,28 +80,35 @@ fn fill_super(sb: &mut SuperBlock<Self>) -> Result {
}
fn init_root(sb: &SuperBlock<Self>) -> Result<dentry::Root<Self>> {
- let inode = match sb.get_or_create_inode(1)? {
- Either::Left(existing) => existing,
- Either::Right(mut new) => {
- new.set_fops(DIR_FOPS);
- new.init(inode::Params {
- typ: inode::Type::Dir,
- mode: 0o555,
- size: ENTRIES.len().try_into()?,
- blocks: 1,
- nlink: 2,
- uid: 0,
- gid: 0,
- atime: UNIX_EPOCH,
- ctime: UNIX_EPOCH,
- mtime: UNIX_EPOCH,
- })?
- }
- };
+ let inode = Self::iget(sb, &ENTRIES[0])?;
dentry::Root::try_new(inode)
}
}
+#[vtable]
+impl inode::Operations for RoFs {
+ type FileSystem = Self;
+
+ fn lookup(
+ parent: &Locked<&INode<Self>, inode::ReadSem>,
+ dentry: dentry::Unhashed<'_, Self>,
+ ) -> Result<Option<ARef<DEntry<Self>>>> {
+ if parent.ino() != 1 {
+ return dentry.splice_alias(None);
+ }
+
+ let name = dentry.name();
+ for e in &ENTRIES {
+ if name == e.name {
+ let inode = Self::iget(parent.super_block(), e)?;
+ return dentry.splice_alias(Some(inode));
+ }
+ }
+
+ dentry.splice_alias(None)
+ }
+}
+
#[vtable]
impl file::Operations for RoFs {
type FileSystem = Self;
--
2.34.1
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