[PATCH TOOLS] rust: use libc::Ioctl type for ioctl() request argument

[PATCH TOOLS] rust: use libc::Ioctl type for ioctl() request argument

[Thomas Bertschinger]

The second argument to ioctl() can be defined as a different type by
different libc implementations, and can be a different size on different
architectures depending on what type it is defined as. For example,
glibc defines it as `unsigned long` which may have a different size on
32-bit vs. 64-bit architectures, and musl libc defines it as `int`.

The Rust libc crate exposes a type `libc::Ioctl` which is defined as the
appropriate integer type for the given libc implementation. Using this
type for the request argument to `libc::ioctl()` ensures code will
compile correctly regardless of architecture and libc implementation.

Also, because ioctl request numbers are defined to be 32 bits
(regardless of the fact that `unsigned long` might sometimes take 64
bits on some architectures), this patch changes the Rust representation
of the bcachefs ioctl numbers to u32 instead of u64.

Signed-off-by: Thomas Bertschinger <tahbertschinger@gmail.com>
---
 bch_bindgen/src/libbcachefs_wrapper.h | 4 ++--
 src/wrappers/handle.rs                | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/bch_bindgen/src/libbcachefs_wrapper.h b/bch_bindgen/src/libbcachefs_wrapper.h
index bc4658f..128592c 100644
--- a/bch_bindgen/src/libbcachefs_wrapper.h
+++ b/bch_bindgen/src/libbcachefs_wrapper.h
@@ -33,5 +33,5 @@ MARK_FIX_753(blk_mode_t, BLK_OPEN_READ);
 MARK_FIX_753(blk_mode_t, BLK_OPEN_WRITE);
 MARK_FIX_753(blk_mode_t, BLK_OPEN_EXCL);
 
-MARK_FIX_753(__u64, BCH_IOCTL_SUBVOLUME_CREATE);
-MARK_FIX_753(__u64, BCH_IOCTL_SUBVOLUME_DESTROY);
+MARK_FIX_753(__u32, BCH_IOCTL_SUBVOLUME_CREATE);
+MARK_FIX_753(__u32, BCH_IOCTL_SUBVOLUME_DESTROY);
diff --git a/src/wrappers/handle.rs b/src/wrappers/handle.rs
index 48148a8..60bdedb 100644
--- a/src/wrappers/handle.rs
+++ b/src/wrappers/handle.rs
@@ -22,7 +22,7 @@ impl BcachefsHandle {
 
 /// I/O control commands that can be sent to a bcachefs filesystem
 /// Those are non-exhaustive 
-#[repr(u64)]
+#[repr(u32)]
 #[non_exhaustive]
 pub enum BcachefsIoctl {
     SubvolumeCreate = BCH_IOCTL_SUBVOLUME_CREATE,
@@ -47,7 +47,7 @@ impl BcachefsHandle {
     /// Type-safe [`libc::ioctl`] for bcachefs filesystems
     pub fn ioctl(&self, request: BcachefsIoctl, payload: &BcachefsIoctlPayload) -> Result<(), Errno> {
         let payload_ptr: *const libc::c_void = payload.into();
-        let ret = unsafe { libc::ioctl(self.inner.ioctl_fd, request as u64, payload_ptr) };
+        let ret = unsafe { libc::ioctl(self.inner.ioctl_fd, request as libc::Ioctl, payload_ptr) };
 
         if ret == -1 {
             Err(errno::errno())
-- 
2.43.0

Re: [PATCH TOOLS] rust: use libc::Ioctl type for ioctl() request argument

[Kent Overstreet]

On Tue, Feb 20, 2024 at 08:24:20PM -0700, Thomas Bertschinger wrote:
> The second argument to ioctl() can be defined as a different type by
> different libc implementations, and can be a different size on different
> architectures depending on what type it is defined as. For example,
> glibc defines it as `unsigned long` which may have a different size on
> 32-bit vs. 64-bit architectures, and musl libc defines it as `int`.
> 
> The Rust libc crate exposes a type `libc::Ioctl` which is defined as the
> appropriate integer type for the given libc implementation. Using this
> type for the request argument to `libc::ioctl()` ensures code will
> compile correctly regardless of architecture and libc implementation.
> 
> Also, because ioctl request numbers are defined to be 32 bits
> (regardless of the fact that `unsigned long` might sometimes take 64
> bits on some architectures), this patch changes the Rust representation
> of the bcachefs ioctl numbers to u32 instead of u64.
> 
> Signed-off-by: Thomas Bertschinger <tahbertschinger@gmail.com>

this is applied