Re: [PATCH] Btrfs: take block group fragmentation into account for allocation

[Jens Axboe <jens.axboe@oracle.com>]

On Sun, Mar 08 2009, Yien Zheng wrote:
> I tried applying this patch, but the fragmentation_percent function is
> giving me:
> 
> WARNING: "__udivdi3"
> [/home/partition6/yien/git/linux-git/fs/btrfs/btrfs.ko] undefined!
> 
> when I compile, and the module fails to load, even though the build
> completes.  I've traced it to the calculation of max_fragments:
> 
> max_fragments = (block_group->key.offset -
> 		btrfs_block_group_used(&block_group->item)) /
> 		block_group->fragment_size;
> 
> It seems that accessing block_group in here is causing a reference to
> __udivdi3 somehow.  Any idea what's going on here?

You can't to 64-bit divides on 32-bit archs. Make that

max_fragments = block_group->key.offset - btrfs_block_group_used(&block_group->item);
do_div(max_fragments, block_group->fragment_size);

and it should work.

-- 
Jens Axboe