Hi Cai,

On Wed,  9 Feb 2022 10:35:59 +0800 Cai Huoqing <cai.huoqing@linux.dev> wrote:
>
> Avoid the error-unused variable 'migration' when
> CONFIG_TRANSPARENT_HUGEPAGE and CONFIG_ARCH_ENABLE_THP_MIGRATION
> are not enabled.
> 
> Signed-off-by: Cai Huoqing <cai.huoqing@linux.dev>
> ---
>  fs/proc/task_mmu.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index bc2f46033231..b055ff29204d 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -1441,7 +1441,7 @@ static int pagemap_pmd_range(pmd_t *pmdp, unsigned long addr, unsigned long end,
>  	spinlock_t *ptl;
>  	pte_t *pte, *orig_pte;
>  	int err = 0;
> -	bool migration = false;
> +	bool migration __maybe_unused = false;
>  
>  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
>  	ptl = pmd_trans_huge_lock(pmdp, vma);
> -- 
> 2.25.1
> 

This has already been fixed in Andrew's patch set by moving the "#ifdef
CONFIG_TRANSPARENT_HUGEPAGE" above the "migration" declaration.

-- 
Cheers,
Stephen Rothwell