Re: [PATCH 7/8] smb: client: compress: add compress/common.h

[Nathan Chancellor <nathan@kernel.org>]

Hi Enzo,

On Mon, Apr 13, 2026 at 04:07:12PM -0300, Enzo Matsumiya wrote:
> Add compress/common.h to aggregate helpers and definitions that will be
> shared with other compression algorithms.
> 
> Also add a few build time checks for proper support.
> 
> Changes:
> - update affected call paths in compress/lz77.c
> 
> Signed-off-by: Enzo Matsumiya <ematsumiya@suse.de>
> ---
...
> diff --git a/fs/smb/client/compress/common.h b/fs/smb/client/compress/common.h
> new file mode 100644
> index 000000000000..b5ccf5debd22
> --- /dev/null
> +++ b/fs/smb/client/compress/common.h
...
> +/*
> + * Build time checks/asserts.
> + * These are assumptions/expectations for all algorithms implemented.
> + */
> +#ifndef __LITTLE_ENDIAN /* TODO */
> +# error "SMB3 compression is only supported on little endian architectures"
> +#endif /* !__LITTLE_ENDIAN */
> +
> +#if BITS_PER_LONG < 64 /* TODO */
> +# error "SMB3 compression is only supported on 64-bit architectures"
> +#endif /* BITS_PER_LONG < 64 */
> +
> +/* Build time double checks (probably unnecessary) */
> +static_assert(sizeof(u16) == 2);
> +static_assert(sizeof(u32) == 4);
> +static_assert(sizeof(u64) == 8);
> +static_assert(sizeof(size_t) == 8);

Steve pushed this change into -next as commit 20a248d5e77a ("smb:
client: compress: add compress/common.h"), where it breaks the build for
many 32-bit architectures for obvious reasons:

  $ make -skj"$(nproc)" ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- mrproper allmodconfig fs/smb/
  In file included from fs/smb/client/compress/lz77.c:14:
  fs/smb/client/compress/common.h:34:3: error: #error "SMB3 compression is only supported on 64-bit architectures"
     34 | # error "SMB3 compression is only supported on 64-bit architectures"
        |   ^~~~~
  In file included from include/linux/init.h:5,
                   from include/linux/printk.h:6,
                   from include/asm-generic/bug.h:31,
                   from arch/arm/include/asm/bug.h:60,
                   from include/linux/bug.h:5,
                   from include/linux/slab.h:15,
                   from fs/smb/client/compress/lz77.c:9:
  include/linux/build_bug.h:80:41: error: static assertion failed: "sizeof(size_t) == 8"
     80 | #define __static_assert(expr, msg, ...) _Static_assert(expr, msg)
        |                                         ^~~~~~~~~~~~~~
  include/linux/build_bug.h:79:34: note: in expansion of macro '__static_assert'
     79 | #define static_assert(expr, ...) __static_assert(expr, ##__VA_ARGS__, #expr)
        |                                  ^~~~~~~~~~~~~~~
  fs/smb/client/compress/common.h:41:1: note: in expansion of macro 'static_assert'
     41 | static_assert(sizeof(size_t) == 8);
        | ^~~~~~~~~~~~~

It is unacceptable for the build to break in this manner in my opinion.
You should really use Kconfig to gate this code in a proper manner and
not emit any errors or warnings when it is unsupported.

Cheers,
Nathan