Subject: Re: linux-next: build failure after merge of the md tree

From: NeilBrown <[email-masked]>
Date: Wed, 4 Mar 2015 13:44:18 +1100

On Tue, 3 Mar 2015 13:35:31 +1100 Stephen Rothwell <[email-masked]>
wrote:

> Hi Neil,
> 
> On Mon, 2 Mar 2015 17:11:49 +1100 Stephen Rothwell <[email-masked]> wrote:
> >
> > On Mon, 2 Mar 2015 17:03:45 +1100 NeilBrown <[email-masked]> wrote:
> > >
> > > I think
> > > +               bm_blocks = DIV_ROUND_UP(bm_blocks, 4096);
> > > 
> > > needs DIV_ROUND_UP_SECTOR_T()
> > 
> > I tried that and it was not sufficient.
> > 
> > > The first patch you identified adds that line.  The second relocates it.
> > 
> > The second also changes this:
> > 
> > bm_blocks = sector_div(bitmap->mddev->resync_max_sectors, (chunksize >> 9));
> > 
> > (added by the first) to this:
> > 
> > bm_blocks = bitmap->mddev->resync_max_sectors / (bitmap->mddev->bitmap_info.chunksize >> 9);
> > 
> > where bitmap->mddev->resync_max_sectors is a sector_t ...
> 
> So I applied this patch for today:
> 
> From: Stephen Rothwell <[email-masked]>
> Date: Tue, 3 Mar 2015 13:30:26 +1100
> Subject: [PATCH] md/bitmap: use sector_div for sector_t divisions
> 
> Signed-off-by: Stephen Rothwell <[email-masked]>
> ---
>  drivers/md/bitmap.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
> index 23f575f0cd92..d40398404ab6 100644
> --- a/drivers/md/bitmap.c
> +++ b/drivers/md/bitmap.c
> @@ -573,7 +573,8 @@ re_read:
>  	if (bitmap->cluster_slot >= 0) {
>  		long long bm_blocks;
>  
> -		bm_blocks = bitmap->mddev->resync_max_sectors / (bitmap->mddev->bitmap_info.chunksize >> 9);
> +		bm_blocks = sector_div(bitmap->mddev->resync_max_sectors,
> +				       bitmap->mddev->bitmap_info.chunksize >> 9);
>  		bm_blocks = bm_blocks << 3;
>  		bm_blocks = DIV_ROUND_UP_SECTOR_T(bm_blocks, 4096);
>  		bitmap->mddev->bitmap_info.offset += bitmap->cluster_slot * (bm_blocks << 3);

Thanks!
sector_div() leave the remainder in it's first argument, so this isn't quite
correct - you need to store resync_max_sectors in a temp variable.
So I made that change and applied you patch.

Thanks,
NeilBrown