[PATCH] rust: file: optimize rust symbol generation for FileDescriptorReservation

[PATCH] rust: file: optimize rust symbol generation for FileDescriptorReservation

[Kunwu Chan]

From: Kunwu Chan <kunwu.chan@hotmail.com>

When build the kernel using the llvm-18.1.3-rust-1.85.0-x86_64
with ARCH=arm64, the following symbols are generated:

$ nm vmlinux | grep ' _R'.*FileDescriptorReservation | rustfilt
ffff8000805b6ef0 T <kernel::fs::file::FileDescriptorReservation>
						::fd_install
ffff8000805b6e60 T <kernel::fs::file::FileDescriptorReservation>
						::get_unused_fd_flags
ffff8000805b6f08 T <kernel::fs::file::FileDescriptorReservation
					 as core::ops::drop::Drop>::drop

These Rust symbols are trivial wrappers around the C functions
fd_install, put_unused_fd and put_task_struct.It
doesn't make sense to go through a trivial wrapper for these
functions, so mark them inline.

After doing so, the above symbol will not in output.

Signed-off-by: Kunwu Chan <kunwu.chan@hotmail.com>
Co-developed-by: Grace Deng <Grace.Deng006@Gmail.com>
Signed-off-by: Grace Deng <Grace.Deng006@Gmail.com>
---
 rust/kernel/fs/file.rs | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/rust/kernel/fs/file.rs b/rust/kernel/fs/file.rs
index e03dbe14d62a..3dda2bfca1a6 100644
--- a/rust/kernel/fs/file.rs
+++ b/rust/kernel/fs/file.rs
@@ -392,6 +392,7 @@ pub struct FileDescriptorReservation {
 
 impl FileDescriptorReservation {
     /// Creates a new file descriptor reservation.
+    #[inline]
     pub fn get_unused_fd_flags(flags: u32) -> Result<Self> {
         // SAFETY: FFI call, there are no safety requirements on `flags`.
         let fd: i32 = unsafe { bindings::get_unused_fd_flags(flags) };
@@ -413,6 +414,7 @@ pub fn reserved_fd(&self) -> u32 {
     ///
     /// The previously reserved file descriptor is bound to `file`. This method consumes the
     /// [`FileDescriptorReservation`], so it will not be usable after this call.
+    #[inline]
     pub fn fd_install(self, file: ARef<File>) {
         // SAFETY: `self.fd` was previously returned by `get_unused_fd_flags`. We have not yet used
         // the fd, so it is still valid, and `current` still refers to the same task, as this type
@@ -433,6 +435,7 @@ pub fn fd_install(self, file: ARef<File>) {
 }
 
 impl Drop for FileDescriptorReservation {
+    #[inline]
     fn drop(&mut self) {
         // SAFETY: By the type invariants of this type, `self.fd` was previously returned by
         // `get_unused_fd_flags`. We have not yet used the fd, so it is still valid, and `current`
-- 
2.43.0

Re: [PATCH] rust: file: optimize rust symbol generation for FileDescriptorReservation

[Alice Ryhl]

On Thu, Mar 13, 2025 at 04:45:25PM +0800, Kunwu Chan wrote:
> From: Kunwu Chan <kunwu.chan@hotmail.com>
> 
> When build the kernel using the llvm-18.1.3-rust-1.85.0-x86_64
> with ARCH=arm64, the following symbols are generated:
> 
> $ nm vmlinux | grep ' _R'.*FileDescriptorReservation | rustfilt
> ffff8000805b6ef0 T <kernel::fs::file::FileDescriptorReservation>
> 						::fd_install
> ffff8000805b6e60 T <kernel::fs::file::FileDescriptorReservation>
> 						::get_unused_fd_flags
> ffff8000805b6f08 T <kernel::fs::file::FileDescriptorReservation
> 					 as core::ops::drop::Drop>::drop
> 
> These Rust symbols are trivial wrappers around the C functions
> fd_install, put_unused_fd and put_task_struct.It
> doesn't make sense to go through a trivial wrapper for these
> functions, so mark them inline.
> 
> After doing so, the above symbol will not in output.
> 
> Signed-off-by: Kunwu Chan <kunwu.chan@hotmail.com>
> Co-developed-by: Grace Deng <Grace.Deng006@Gmail.com>
> Signed-off-by: Grace Deng <Grace.Deng006@Gmail.com>

A few notes:

* Your own Signed-off-by must always be last.
* You're missing Link: and Suggested-by: tags.
* There are some grammar issues, e.g. a missing space before "It" and
  the phrase "will not in output" is not good.
* Let's also add the marker to `reserved_fd` to be on the safe side.
* I think it is easier to read the symbols if you list each sybmol on
  one line like this:

ffff8000805b6ef0 T <kernel::fs::file::FileDescriptorReservation>::fd_install
ffff8000805b6e60 T <kernel::fs::file::FileDescriptorReservation>::get_unused_fd_flags
ffff8000805b6f08 T <kernel::fs::file::FileDescriptorReservation as core::ops::drop::Drop>::drop

Alice

Re: [PATCH] rust: file: optimize rust symbol generation for FileDescriptorReservation

[Kunwu Chan]

On 2025/3/13 18:47, Alice Ryhl wrote:
> On Thu, Mar 13, 2025 at 04:45:25PM +0800, Kunwu Chan wrote:
>> From: Kunwu Chan <kunwu.chan@hotmail.com>
>>
>> When build the kernel using the llvm-18.1.3-rust-1.85.0-x86_64
>> with ARCH=arm64, the following symbols are generated:
>>
>> $ nm vmlinux | grep ' _R'.*FileDescriptorReservation | rustfilt
>> ffff8000805b6ef0 T <kernel::fs::file::FileDescriptorReservation>
>> 						::fd_install
>> ffff8000805b6e60 T <kernel::fs::file::FileDescriptorReservation>
>> 						::get_unused_fd_flags
>> ffff8000805b6f08 T <kernel::fs::file::FileDescriptorReservation
>> 					 as core::ops::drop::Drop>::drop
>>
>> These Rust symbols are trivial wrappers around the C functions
>> fd_install, put_unused_fd and put_task_struct.It
>> doesn't make sense to go through a trivial wrapper for these
>> functions, so mark them inline.
>>
>> After doing so, the above symbol will not in output.
>>
>> Signed-off-by: Kunwu Chan <kunwu.chan@hotmail.com>
>> Co-developed-by: Grace Deng <Grace.Deng006@Gmail.com>
>> Signed-off-by: Grace Deng <Grace.Deng006@Gmail.com>
> A few notes:
>
> * Your own Signed-off-by must always be last.
> * You're missing Link: and Suggested-by: tags.

Thanks for the reply.

I'll change my own Signed-off-by be last and add Link and Suggested-by 
as the following:

Link: https://github.com/Rust-for-Linux/linux/issues/1145
Suggested-by: Alice Ryhl <aliceryhl@google.com>
Co-developed-by: Grace Deng <Grace.Deng006@Gmail.com>
Signed-off-by: Grace Deng <Grace.Deng006@Gmail.com>
Signed-off-by: Kunwu Chan <kunwu.chan@hotmail.com>

> * There are some grammar issues, e.g. a missing space before "It" and
>    the phrase "will not in output" is not good.
I'll  add a space before "It" and remove the last line.
> * Let's also add the marker to `reserved_fd` to be on the safe side.
Sure, I'll make 'reserved_fd ' inline in v2.
> * I think it is easier to read the symbols if you list each sybmol on
>    one line like this:
>
> ffff8000805b6ef0 T <kernel::fs::file::FileDescriptorReservation>::fd_install
> ffff8000805b6e60 T <kernel::fs::file::FileDescriptorReservation>::get_unused_fd_flags
> ffff8000805b6f08 T <kernel::fs::file::FileDescriptorReservation as core::ops::drop::Drop>::drop

If in one line, checkpatch.pl will report a warning:

WARNING:Prefer a maximum 75 chars per line (possible unwrapped commit 
description?)

If no need to  bother with the warning, I'll change it to one line in v2.

>
> Alice



-- 
Thanks,
   Kunwu.Chan(Tao.chan)

Re: [PATCH] rust: file: optimize rust symbol generation for FileDescriptorReservation

[Alice Ryhl]

On Fri, Mar 14, 2025 at 3:34 AM Kunwu Chan <kunwu.chan@linux.dev> wrote:
> > * I think it is easier to read the symbols if you list each sybmol on
> >    one line like this:
> >
> > ffff8000805b6ef0 T <kernel::fs::file::FileDescriptorReservation>::fd_install
> > ffff8000805b6e60 T <kernel::fs::file::FileDescriptorReservation>::get_unused_fd_flags
> > ffff8000805b6f08 T <kernel::fs::file::FileDescriptorReservation as core::ops::drop::Drop>::drop
>
> If in one line, checkpatch.pl will report a warning:
>
> WARNING:Prefer a maximum 75 chars per line (possible unwrapped commit
> description?)
>
> If no need to  bother with the warning, I'll change it to one line in v2.

You could do this:
... T <kernel::fs::file::FileDescriptorReservation>::fd_install
but if it's still too long I'd just ignore it.

Alice

Re: [PATCH] rust: file: optimize rust symbol generation for FileDescriptorReservation

[Kunwu Chan]

On 2025/3/14 17:21, Alice Ryhl wrote:
> On Fri, Mar 14, 2025 at 3:34 AM Kunwu Chan <kunwu.chan@linux.dev> wrote:
>>> * I think it is easier to read the symbols if you list each sybmol on
>>>     one line like this:
>>>
>>> ffff8000805b6ef0 T <kernel::fs::file::FileDescriptorReservation>::fd_install
>>> ffff8000805b6e60 T <kernel::fs::file::FileDescriptorReservation>::get_unused_fd_flags
>>> ffff8000805b6f08 T <kernel::fs::file::FileDescriptorReservation as core::ops::drop::Drop>::drop
>> If in one line, checkpatch.pl will report a warning:
>>
>> WARNING:Prefer a maximum 75 chars per line (possible unwrapped commit
>> description?)
>>
>> If no need to  bother with the warning, I'll change it to one line in v2.
> You could do this:
> ... T <kernel::fs::file::FileDescriptorReservation>::fd_install
> but if it's still too long I'd just ignore it.

Thanks, I'll change it in v2.

>
> Alice

-- 
Thanks,
   Kunwu.Chan