On Fri, 13 Mar 2026 14:45:20 -0400
Jeff Layton <[email protected]> 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 <[email protected]>
> Closes:
> https://lore.kernel.org/oe-kbuild-all/[email protected]/
> Reviewed-by: Viacheslav Dubeyko <[email protected]>
> Acked-by: Ryusuke Konishi <[email protected]>
> Signed-off-by: Jeff Layton <[email protected]>
> ---
> 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..abcf5252578ad24f694bfccf525893674bfcb4bc
> 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;
Are you sure entries_per_group can be more than 32 bits?
It looks like something that will be the same size on 32 and 64bit.
> + unsigned long group;
> + u32 index;
> +
> + group = div_u64(bmap->b_inode->i_ino, entries_per_group);
You don't need the full 64 by 64 divide.
IIRC there are both div_u64_u32() and div_u64_ulong().
> + div_u64_rem(bmap->b_inode->i_ino, NILFS_BMAP_GROUP_DIV, &index);
NILFD_BMAP_GROUP_DIV is 8 (and probably has to be a power of 2).
So:
index = bmap->b_inode->i_ino & (NILFS_BMAP_GROUP_DIV - 1);
is the same and likely much faster to calculate.
(The compiler will have done that optimisation before.)
David
>
> return group * entries_per_group +
> - (bmap->b_inode->i_ino % NILFS_BMAP_GROUP_DIV) *
> - (entries_per_group / NILFS_BMAP_GROUP_DIV);
> + index * (entries_per_group / NILFS_BMAP_GROUP_DIV);
> }
>
> static struct lock_class_key nilfs_bmap_dat_lock_key;
>
