This patch addresses build issues with bch_bindgen on architectures
where the natural alignment of u64 is 4 instead of 8, such as i686 and
ppc64. The issue arises from rustc's refusing to compile structs with a
"packed" attribute that have members with an explicit "align(N)"
attribute.
rust-bindgen generally does not place "align(N)" attributes on types
when it is redundant with the type's natural alignment. There are a few
types in bcachefs with "__aligned(8)" in C where the type's natural
alignment is 8 except on architectures like those mentioned above where
it is 4. rust-bindgen places the "align(8)" attribute on these types,
for those architectures. The affected types include:
- bch_csum
- bch_sb_layout
- bch_ioctl_data_progress
bch_ioctl_data_progress, and all types that depend on it, are not used
on the Rust side currently and bindings are only generated for them
because they are covered by `.allowlist_type("bch_.*")` in
bch_bindgen/build.rs. This patch resolves the build failure for this
type by excluding it from bch_bindgen. If/when accessing this type in
Rust is needed, a decision can be made then about how to represent its
layout in Rust.
bch_csum and bch_sb_layout, and types that depend on them, are currently
used in Rust so they can't be excluded. This patch addresses these types
by stripping off the "packed" attribute in Rust on types that embed
these types, since that attribute happens to not be necessary for proper
layout.
Signed-off-by: Thomas Bertschinger <tahbertschinger@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
This updates rust-bindgen to version 0.69.4 which includes the patch
199bee441ad0: "try to avoid #[repr(packed)] when align is needed". With
this patch, bindgen generates code that is both ABI-correct and can be
compiled by rustc, for 3 bcachefs types:
- bkey
- bch_extent_crc32
- bch_extent_ptr
This allows us to remove the custom treatment for these three types.
Signed-off-by: Thomas Bertschinger <tahbertschinger@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
This function allows to obtain a handle to send various `ioctl`s to the underlying bcachefs filesystem.
We need also its counterpart to clean up.
Signed-off-by: Ryan Lahfa <bcachefs@lahfa.xyz>
bcachefs-tools has been using a patched bindgen to work around a
limitation of rustc that prevents compiling structs with
both #[repr(packed(N)] and #[repr(align(N)] attributes. The patch:
e8168ceda507 "codegen: Don't generate conflicting packed() and align()
representation hints." discards the "align" attribute in cases where
bindgen produces a type with both.
This may be correct for some types, but it turns out that for each
bcachefs type with this problem, keeping the "align" attribute and
discarding the "packed" attribute generates a type with the same ABI as
the original C type.
This can be tested automatically by running:
$ cargo test --manifest-path bch_bindgen/Cargo.toml
in the bcachefs-tools tree.
There has been pressure recently to start using upstream bindgen; both
externally, from distribution maintainers who want to build
bcachefs-tools with standard dependencies, and internally, in order to
enable using Rust for bcachefs in-kernel.
This patch updates bcachefs-tools to use upstream bindgen. It works
around the rustc limitation with a post-processing step in the bindgen
build that adjusts the attributes to include "#[repr(C, align(N))]" and
exclude #[repr(packed(N)] only for the 4 types that need it. It also
updates bch_bindgen to format the code with prettyplease so that this
will work even in environments with rustfmt installed.
Some types that had been manually implemented in
bch_bindgen/src/bcachefs.rs are now automatically generated by bindgen,
so that they will be covered by the ABI compatibility testing mentioned
above.
I intentionally targeted the post-processing to the exact 4 types with
the issue currently, so that any changes to bcachefs that result in this
issue appearing for a new type will require manual intervention. I
figured any such changes should require careful consideration.
Ideally, bindgen can be updated to handle situations where "align(N)"
is needed and "packed(N)" can be safely discarded. If a patch for this
is accepted into bindgen, the post-processing hack can be removed.
I update the minimum Rust version to 1.70 as this is needed to build
recent versions of some dependencies.
Signed-off-by: Thomas Bertschinger <tahbertschinger@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
This moves the Rust sources out of rust_src/ and into the top level.
Running the bcachefs executable out of the development tree is now:
$ ./target/release/bcachefs command
or
$ cargo run --profile release -- command
instead of "./bcachefs command".
Building and installing is still:
$ make && make install
Signed-off-by: Thomas Bertschinger <tahbertschinger@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
