Re: [PATCH 1/2] nilfs2: fix 64-bit division operations in nilfs_bmap_find_target_in_group()

[Viacheslav Dubeyko]

On Tue, 2026-03-10 at 07:43 -0400, Jeff Layton wrote:
> With the change to make inode->i_ino a u64, the build started failing
> on
> 32-bit ARM with:
> 
>     ERROR: modpost: "__aeabi_uldivmod" [fs/nilfs2/nilfs2.ko]
> undefined!
> 
> Fix this by using the 64-bit division interfaces in
> nilfs_bmap_find_target_in_group().
> 
> Fixes: 998a59d371c2 ("treewide: fix missed i_ino format specifier
> conversions")
> Reported-by: kernel test robot <lkp@xxxxxxxxx>
> Closes:
> https://lore.kernel.org/oe-kbuild-all/202603100602.KPxiClIO-lkp@xxxxxxxxx/
> Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
> ---
>  fs/nilfs2/bmap.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/nilfs2/bmap.c b/fs/nilfs2/bmap.c
> index
> 824f2bd91c167965ec3a660202b6e6c5f1fe007e..4ce9a93149a5af13bc215cc1877
> a757e2c6cf49b 100644
> --- a/fs/nilfs2/bmap.c
> +++ b/fs/nilfs2/bmap.c
> @@ -455,11 +455,14 @@ __u64 nilfs_bmap_find_target_in_group(const
> struct nilfs_bmap *bmap)
>  {
>  	struct inode *dat = nilfs_bmap_get_dat(bmap);
>  	unsigned long entries_per_group =
> nilfs_palloc_entries_per_group(dat);
> -	unsigned long group = bmap->b_inode->i_ino /
> entries_per_group;
> +	unsigned long group;
> +	u32 rem;
> +
> +	group = div_u64(bmap->b_inode->i_ino, entries_per_group);
> +	div_u64_rem(bmap->b_inode->i_ino, NILFS_BMAP_GROUP_DIV,
> &rem);
>  
>  	return group * entries_per_group +
> -		(bmap->b_inode->i_ino % NILFS_BMAP_GROUP_DIV) *
> -		(entries_per_group / NILFS_BMAP_GROUP_DIV);
> +	       rem * (entries_per_group / NILFS_BMAP_GROUP_DIV);
>  }
>  
>  static struct lock_class_key nilfs_bmap_dat_lock_key;

Makes sense. :) Maybe, rem is not very good variable name, but the
whole logic looks good.

Reviewed-by: Viacheslav Dubeyko <slava@xxxxxxxxxxx>

Thanks,
Slava.