[RFC PATCH 20/24] erofs: introduce readdir alternative to C

Yiyang Wu
2024-09-16T13:57:18Z

This patch introduce erofs_readdir_rust as an alternative
for erofs_readdir written in Rust.

Signed-off-by: Yiyang Wu <toolmanp@tlmp.cc>
---
fs/erofs/Makefile | 2 +-
fs/erofs/dir.c | 2 ++
fs/erofs/dir_rs.rs | 57 ++++++++++++++++++++++++++++++++++++++++
fs/erofs/internal.h | 1 +
fs/erofs/rust_bindings.h | 1 +
5 files changed, 62 insertions(+), 1 deletion(-)
create mode 100644 fs/erofs/dir_rs.rs

diff --git a/fs/erofs/Makefile b/fs/erofs/Makefile
index 0f748f3e0ff6..e086487971b6 100644
--- a/fs/erofs/Makefile
+++ b/fs/erofs/Makefile
@@ -9,4 +9,4 @@ erofs-$(CONFIG_EROFS_FS_ZIP_DEFLATE) += decompressor_deflate.o
erofs-$(CONFIG_EROFS_FS_ZIP_ZSTD) += decompressor_zstd.o
erofs-$(CONFIG_EROFS_FS_BACKED_BY_FILE) += fileio.o
erofs-$(CONFIG_EROFS_FS_ONDEMAND) += fscache.o
-erofs-$(CONFIG_EROFS_FS_RUST) += super_rs.o inode_rs.o namei_rs.o rust_helpers.o
+erofs-$(CONFIG_EROFS_FS_RUST) += super_rs.o inode_rs.o namei_rs.o dir_rs.o rust_helpers.o
diff --git a/fs/erofs/dir.c b/fs/erofs/dir.c
index c3b90abdee37..0f5df8a4169b 100644
--- a/fs/erofs/dir.c
+++ b/fs/erofs/dir.c
@@ -6,6 +6,7 @@
*/
#include "internal.h"

+#ifndef CONFIG_EROFS_FS_RUST
static int erofs_fill_dentries(struct inode *dir, struct dir_context *ctx,
void *dentry_blk, struct erofs_dirent *de,
unsigned int nameoff0, unsigned int maxsize)
@@ -92,6 +93,7 @@ static int erofs_readdir(struct file *f, struct dir_context *ctx)
erofs_put_metabuf(&buf);
return err < 0 ? err : 0;
}
+#endif

const struct file_operations erofs_dir_fops = {
.llseek = generic_file_llseek,
diff --git a/fs/erofs/dir_rs.rs b/fs/erofs/dir_rs.rs
new file mode 100644
index 000000000000..d965e6076242
--- /dev/null
+++ b/fs/erofs/dir_rs.rs
@@ -0,0 +1,57 @@
+// Copyright 2024 Yiyang Wu
+// SPDX-License-Identifier: MIT or GPL-2.0-or-later
+
+//! EROFS Rust Kernel Module Helpers Implementation
+//! This is only for experimental purpose. Feedback is always welcome.
+
+#[allow(dead_code)]
+#[allow(missing_docs)]
+pub(crate) mod rust;
+use core::ffi::*;
+use core::ptr::NonNull;
+
+use kernel::bindings::{dir_context, file};
+use kernel::container_of;
+
+use rust::{
+ erofs_sys::{inode::*, *},
+ kinode::*,
+ ksuperblock::*,
+};
+
+/// Exported as a replacement of erofs_readdir.
+#[no_mangle]
+pub unsafe extern "C" fn erofs_readdir_rust(
+ f: NonNull<file>,
+ mut ctx: NonNull<dir_context>,
+) -> c_int {
+ // SAFETY: inode is always initialized in file.
+ let k_inode = unsafe { f.as_ref().f_inode };
+ // SAFETY: We are sure that the inode is a Kernel Inode since alloc_inode is called
+ let erofs_inode = unsafe { &*container_of!(k_inode, KernelInode, k_inode) };
+ // SAFETY: The super_block is always initialized when calling iget5_locked.
+ let sb = unsafe { (*k_inode).i_sb };
+ let sbi = erofs_sbi(NonNull::new(sb).unwrap());
+ // SAFETY: ctx is nonnull.
+ let offset = unsafe { ctx.as_ref().pos };
+ match sbi
+ .filesystem
+ .fill_dentries(erofs_inode, offset as Off, &mut |dir, pos| unsafe {
+ // inline expansion from dir_emit
+ ctx.as_ref().actor.unwrap()(
+ ctx.as_ptr(),
+ dir.name.as_ptr().cast(),
+ dir.name.len() as i32,
+ pos as i64,
+ dir.desc.nid as u64,
+ dir.desc.file_type as u32,
+ );
+ ctx.as_mut().pos = pos as i64;
+ }) {
+ Ok(_) => {
+ unsafe { ctx.as_mut().pos = erofs_inode.info().file_size() as i64 }
+ 0
+ }
+ Err(e) => (i32::from(e)) as c_int,
+ }
+}
diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
index 1d9dfae285d5..6f57bb866637 100644
--- a/fs/erofs/internal.h
+++ b/fs/erofs/internal.h
@@ -444,6 +444,7 @@ int erofs_iget5_set(struct inode *inode, void *opaque);
#define erofs_iget erofs_iget_rust
#define erofs_get_parent erofs_get_parent_rust
#define erofs_lookup erofs_lookup_rust
+#define erofs_readdir erofs_readdir_rust
#else
struct inode *erofs_iget(struct super_block *sb, erofs_nid_t nid);
#endif
diff --git a/fs/erofs/rust_bindings.h b/fs/erofs/rust_bindings.h
index b35014aa5cae..8b71d65e2c0b 100644
--- a/fs/erofs/rust_bindings.h
+++ b/fs/erofs/rust_bindings.h
@@ -23,4 +23,5 @@ extern struct inode *erofs_iget_rust(struct super_block *sb, erofs_nid_t nid);
extern struct dentry *erofs_lookup_rust(struct inode *inode, struct dentry *dentry,
unsigned int flags);
extern struct dentry *erofs_get_parent_rust(struct dentry *dentry);
+extern int erofs_readdir_rust(struct file *file, struct dir_context *ctx);
#endif
--
2.46.0