Re: [PATCH] rust: helpers: add is_vmalloc_addr wrapper for NOMMU builds

[Danilo Krummrich <dakr@kernel.org>]

On 5/22/26 8:54 PM, Shivam Kalra via B4 Relay wrote:
> From: Shivam Kalra <shivamkalra98@zohomail.in>
> 
> Commit 47ac2a4b5cd8 ("rust: kvec: implement shrink_to for KVVec")
> introduced a call to bindings::is_vmalloc_addr(). However, this
> fails to compile on architectures where CONFIG_MMU is disabled,
> resulting in the following build error:
> 
>     error[E0425]: cannot find function is_vmalloc_addr in crate bindings
> 
> When CONFIG_MMU is not set, is_vmalloc_addr() is defined as a
> static inline function in <linux/mm.h> that unconditionally
> returns false. Because bindgen skips static inline functions
> when generating bindings, the symbol is completely missing from
> the Rust bindings crate.
> 
> Fix this by providing a C helper wrapper, rust_helper_is_vmalloc_addr(),
> in rust/helpers/vmalloc.c. This ensures the function is reliably
> exposed to Rust regardless of the MMU configuration. On NOMMU builds,
> this allows KVVec::shrink_to() to successfully compile and correctly
> route all allocations through the kmalloc realloc path.
> 
> Fixes: 47ac2a4b5cd8 ("rust: kvec: implement shrink_to for KVVec")
> Reported-by: kernel test robot <lkp@intel.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202605220811.LRplxeBR-lkp@intel.com/
> Signed-off-by: Shivam Kalra <shivamkalra98@zohomail.in>

Reviewed-by: Danilo Krummrich <dakr@kernel.org>