nilfs2: fix 64-bit division operations in nilfs_bmap_find_target_in_group()

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 udiv_u64() for the division.

For finding the index into the group, switch to using a bitwise &
operation since that's more efficient. With this change however,
NILFS_BMAP_GROUP_DIV must be a power of two, so add a compile-time
assertion for that.

Fixes: 998a59d371c2 ("treewide: fix missed i_ino format specifier conversions")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202603100602.KPxiClIO-lkp@intel.com/
Reviewed-by: Viacheslav Dubeyko <slava@dubeyko.com>
Acked-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Link: https://patch.msgid.link/20260316-iino-u64-v3-2-d1076b8f7a20@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/fs/nilfs2/bmap.c b/fs/nilfs2/bmap.c
index 824f2bd91c167965ec3a660202b6e6c5f1fe007e..5f0f1f283af0208e1879e2e84b0b5b9629fd6b8a 100644 (file)
--- a/fs/nilfs2/bmap.c
+++ b/fs/nilfs2/bmap.c
@@ -450,18 +450,25 @@ __u64 nilfs_bmap_find_target_seq(const struct nilfs_bmap *bmap, __u64 key)
                return NILFS_BMAP_INVALID_PTR;
 }
 
-#define NILFS_BMAP_GROUP_DIV   8
+#define NILFS_BMAP_GROUP_DIV   8       /* must be power of 2 */
+
 __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 index;
+
+       BUILD_BUG_ON_NOT_POWER_OF_2(NILFS_BMAP_GROUP_DIV);
+
+       group = div_u64(bmap->b_inode->i_ino, entries_per_group);
+       index = bmap->b_inode->i_ino & (NILFS_BMAP_GROUP_DIV - 1);
 
        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;
 static struct lock_class_key nilfs_bmap_mdt_lock_key;