Re: [PATCH -next] mm：fix build error of defined but not used

["HORIGUCHI NAOYA(堀口 直也)" <naoya.horiguchi@nec.com>]

On Thu, Jun 09, 2022 at 01:00:28PM +0800, Guan Jing wrote:
> If CONFIG_HUGETLB_PAGE is not set and CONFIG_FS_DAX=y.
> Use command "make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu-" to
> build, will fail:
> 
> mm/memory-failure.c:568:13: error: ‘collect_procs_fsdax’ defined
> but not used [-Werror=unused-function]
> 	static void collect_procs_fsdax(struct page *page,
>              ^~~~~~~~~~~~~~~~~~~
> cc1: all warnings being treated as errors
> make[1]: *** [mm/memory-failure.o] Error 1
> make[1]: *** Waiting for unfinished jobs....
> make: *** [mm] Error 2
> make: *** Waiting for unfinished jobs....
> 
> so extending "#ifdef CONFIG_HUGETLB_PAG" to cover
> collect_procs_fsdax() would be a simple resolution.

Thank you for reporting. I think that collect_procs_fsdax() seems to not
depend on hugetlb, so probably mf_dax_kill_procs() should be defined outside
"#ifdef CONFIG_HUGETLB_PAGE"?

Thanks,
Naoya Horiguchi

> 
> Reported-by: Hulk Robot <hulkci@huawei.com>
> Fixes: 143ac5cd7289 ("mm: introduce mf_dax_kill_procs() for fsdax case")
> Signed-off-by: Guan Jing <guanjing6@huawei.com>
> ---
>  mm/memory-failure.c | 56 ++++++++++++++++++++++-----------------------
>  1 file changed, 28 insertions(+), 28 deletions(-)
> 
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 545f402c4890..952f117e4584 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -561,34 +561,6 @@ static void collect_procs_file(struct page *page, struct list_head *to_kill,
>  	i_mmap_unlock_read(mapping);
>  }
>  
> -#ifdef CONFIG_FS_DAX
> -/*
> - * Collect processes when the error hit a fsdax page.
> - */
> -static void collect_procs_fsdax(struct page *page,
> -		struct address_space *mapping, pgoff_t pgoff,
> -		struct list_head *to_kill)
> -{
> -	struct vm_area_struct *vma;
> -	struct task_struct *tsk;
> -
> -	i_mmap_lock_read(mapping);
> -	read_lock(&tasklist_lock);
> -	for_each_process(tsk) {
> -		struct task_struct *t = task_early_kill(tsk, true);
> -
> -		if (!t)
> -			continue;
> -		vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
> -			if (vma->vm_mm == t->mm)
> -				add_to_kill(t, page, pgoff, vma, to_kill);
> -		}
> -	}
> -	read_unlock(&tasklist_lock);
> -	i_mmap_unlock_read(mapping);
> -}
> -#endif /* CONFIG_FS_DAX */
> -
>  /*
>   * Collect the processes who have the corrupted page mapped to kill.
>   */
> @@ -1540,6 +1512,34 @@ static int try_to_split_thp_page(struct page *page, const char *msg)
>  }
>  
>  #ifdef CONFIG_HUGETLB_PAGE
> +#ifdef CONFIG_FS_DAX
> +/*
> + * Collect processes when the error hit a fsdax page.
> + */
> +static void collect_procs_fsdax(struct page *page,
> +		struct address_space *mapping, pgoff_t pgoff,
> +		struct list_head *to_kill)
> +{
> +	struct vm_area_struct *vma;
> +	struct task_struct *tsk;
> +
> +	i_mmap_lock_read(mapping);
> +	read_lock(&tasklist_lock);
> +	for_each_process(tsk) {
> +		struct task_struct *t = task_early_kill(tsk, true);
> +
> +		if (!t)
> +			continue;
> +		vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
> +			if (vma->vm_mm == t->mm)
> +				add_to_kill(t, page, pgoff, vma, to_kill);
> +		}
> +	}
> +	read_unlock(&tasklist_lock);
> +	i_mmap_unlock_read(mapping);
> +}
> +#endif /* CONFIG_FS_DAX */
> +
>  /*
>   * Called from hugetlb code with hugetlb_lock held.
>   *
> -- 
> 2.17.1