Excerpts from liubo's message of 2011-03-31 05:45:20 -0400:
>
> While compile btrfs modules on 32bit box, I encounter the following:
>
> WARNING: "__umoddi3" [fs/btrfs/btrfs.ko] undefined!
>
> The WARNING comes from that __btrfs_map_block does not use do_div() for
> relative operations, this will cause problems on 32bit box, for values
> with "u64" type should use do_div() instead of a direct "%".
Which kernel tree was this against? I had rebased the for-linus and
for-linus-unmerged branch to get rid of it.
Sorry for the confusion.
-chris
>
> Signed-off-by: Liu Bo <liubo2009@xxxxxxxxxxxxxx>
> ---
> fs/btrfs/volumes.c | 23 +++++++++++++++--------
> 1 files changed, 15 insertions(+), 8 deletions(-)
>
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index 41afd50..7b23d0f 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -3076,16 +3076,19 @@ again:
> multi->stripes[i].dev = map->stripes[stripe_index].dev;
>
> if (map->type & BTRFS_BLOCK_GROUP_RAID0) {
> - u64 stripes;
> - int last_stripe = (stripe_nr_end - 1) %
> - map->num_stripes;
> + u64 stripes = stripe_nr_end - 1;
> + int last_stripe = do_div(stripes,
> + map->num_stripes);
> int j;
>
> for (j = 0; j < map->num_stripes; j++) {
> - if ((stripe_nr_end - 1 - j) %
> - map->num_stripes == stripe_index)
> + stripes = stripe_nr_end - 1 - j;
> +
> + if (do_div(stripes, map->num_stripes) ==
> + stripe_index)
> break;
> }
> +
> stripes = stripe_nr_end - 1 - j;
> do_div(stripes, map->num_stripes);
> multi->stripes[i].length = map->stripe_len *
> @@ -3100,18 +3103,22 @@ again:
> multi->stripes[i].length -=
> stripe_end_offset;
> } else if (map->type & BTRFS_BLOCK_GROUP_RAID10) {
> - u64 stripes;
> + u64 stripes = stripe_nr_end - 1;
> int j;
> int factor = map->num_stripes /
> map->sub_stripes;
> - int last_stripe = (stripe_nr_end - 1) % factor;
> + int last_stripe = do_div(stripes, factor);
> +
> last_stripe *= map->sub_stripes;
>
> for (j = 0; j < factor; j++) {
> - if ((stripe_nr_end - 1 - j) % factor ==
> + stripes = stripe_nr_end - 1 - j;
> +
> + if (do_div(stripes, factor) ==
> stripe_index / map->sub_stripes)
> break;
> }
> +
> stripes = stripe_nr_end - 1 - j;
> do_div(stripes, factor);
> multi->stripes[i].length = map->stripe_len *
--
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