From: Wedson Almeida Filho <walmeida@xxxxxxxxxxxxx>
This allows file systems to customise their behaviour when callers want
to read from a file.
Signed-off-by: Wedson Almeida Filho <walmeida@xxxxxxxxxxxxx>
---
rust/kernel/fs/file.rs | 35 ++++++++++++++++++++++++++++++++++-
rust/kernel/user.rs | 1 -
samples/rust/rust_rofs.rs | 6 +++++-
3 files changed, 39 insertions(+), 3 deletions(-)
diff --git a/rust/kernel/fs/file.rs b/rust/kernel/fs/file.rs
index 77eb6d230568..2ba456a1eee1 100644
--- a/rust/kernel/fs/file.rs
+++ b/rust/kernel/fs/file.rs
@@ -12,6 +12,7 @@
bindings,
error::{code::*, from_result, Error, Result},
types::{ARef, AlwaysRefCounted, Locked, Opaque},
+ user,
};
use core::{marker::PhantomData, mem::ManuallyDrop, ptr};
use macros::vtable;
@@ -324,6 +325,15 @@ pub trait Operations {
/// File system that these operations are compatible with.
type FileSystem: FileSystem + ?Sized;
+ /// Reads data from this file into the caller's buffer.
+ fn read(
+ _file: &File<Self::FileSystem>,
+ _buffer: &mut user::Writer,
+ _offset: &mut Offset,
+ ) -> Result<usize> {
+ Err(EINVAL)
+ }
+
/// Seeks the file to the given offset.
fn seek(_file: &File<Self::FileSystem>, _offset: Offset, _whence: Whence) -> Result<Offset> {
Err(EINVAL)
@@ -356,7 +366,11 @@ impl<T: Operations + ?Sized> Table<T> {
} else {
None
},
- read: None,
+ read: if T::HAS_READ {
+ Some(Self::read_callback)
+ } else {
+ None
+ },
write: None,
read_iter: None,
write_iter: None,
@@ -407,6 +421,25 @@ impl<T: Operations + ?Sized> Table<T> {
})
}
+ unsafe extern "C" fn read_callback(
+ file_ptr: *mut bindings::file,
+ ptr: *mut core::ffi::c_char,
+ len: usize,
+ offset: *mut bindings::loff_t,
+ ) -> isize {
+ from_result(|| {
+ // SAFETY: The C API guarantees that `file` is valid for the duration of the
+ // callback. Since this callback is specifically for filesystem T, we know `T`
+ // is the right filesystem.
+ let file = unsafe { File::from_raw(file_ptr) };
+ let mut writer = user::Writer::new(ptr, len);
+
+ // SAFETY: The C API guarantees that `offset` is valid for read and write.
+ let read = T::read(file, &mut writer, unsafe { &mut *offset })?;
+ Ok(isize::try_from(read)?)
+ })
+ }
+
unsafe extern "C" fn read_dir_callback(
file_ptr: *mut bindings::file,
ctx_ptr: *mut bindings::dir_context,
diff --git a/rust/kernel/user.rs b/rust/kernel/user.rs
index 35a673ebcd58..20fb887f4640 100644
--- a/rust/kernel/user.rs
+++ b/rust/kernel/user.rs
@@ -11,7 +11,6 @@ pub struct Writer {
}
impl Writer {
- #[allow(dead_code)]
pub(crate) fn new(ptr: *mut i8, len: usize) -> Self {
Self {
ptr: ptr.cast::<u8>(),
diff --git a/samples/rust/rust_rofs.rs b/samples/rust/rust_rofs.rs
index abec084360da..f4be5908369c 100644
--- a/samples/rust/rust_rofs.rs
+++ b/samples/rust/rust_rofs.rs
@@ -4,7 +4,7 @@
use kernel::fs::{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};
+use kernel::{c_str, fs, time::UNIX_EPOCH, types::Either, types::Locked, user};
kernel::module_fs! {
type: RoFs,
@@ -80,6 +80,10 @@ fn seek(file: &File<Self>, offset: Offset, whence: file::Whence) -> Result<Offse
file::generic_seek(file, offset, whence)
}
+ fn read(_: &File<Self>, _: &mut user::Writer, _: &mut Offset) -> Result<usize> {
+ Err(EISDIR)
+ }
+
fn read_dir(
_file: &File<Self>,
inode: &Locked<&INode<Self>, inode::ReadSem>,
--
2.34.1
