[dm-devel] [PATCH v2] dm-switch: Remove unnecessary condition in conditional

[Mikulas Patocka]

On Thu, 29 Oct 2015, Tomohiro Kusumi wrote:

> > 2015-10-28 8:03 GMT+09:00 Mikulas Patocka:
> > On Wed, 28 Oct 2015, Tomohiro Kusumi wrote:
> >
> > > It's always (sctx->nr_regions == nr_regions) considering
> > > the assignment right before this conditional, and this
> > > function is only used by .ctr.
> >
> > The variable sctx->nr_regions has type unsigned long and the variable
> > nr_regions has type sector_t.
> >
> > Thus the variables may be different when overflow happens.
> >
> > It could be changed to "if (nr_regions >= ULONG_MAX)".
> 
> Sorry about that.
> Changed the conditional to "if (nr_regions >= ULONG_MAX)",
> and brought the assignment of nr_regions after sector_div()
> and the sanity check which looks more sane.
> 
> Signed-off-by: Tomohiro Kusumi <kusumi.tomohiro at gmail.com>
> Reviewed-by: Mikulas Patocka <mpatocka at redhat.com>

Acked-by: Mikulas Patocka <mpatocka at redhat.com>

> ---
>  drivers/md/dm-switch.c |    4 ++--
>  1 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/md/dm-switch.c b/drivers/md/dm-switch.c
> index 50fca46..e1b6722 100644
> --- a/drivers/md/dm-switch.c
> +++ b/drivers/md/dm-switch.c
> @@ -99,11 +99,11 @@ static int alloc_region_table(struct dm_target *ti, unsigned nr_paths)
>  	if (sector_div(nr_regions, sctx->region_size))
>  		nr_regions++;
>  
> -	sctx->nr_regions = nr_regions;
> -	if (sctx->nr_regions != nr_regions || sctx->nr_regions >= ULONG_MAX) {
> +	if (nr_regions >= ULONG_MAX) {
>  		ti->error = "Region table too large";
>  		return -EINVAL;
>  	}
> +	sctx->nr_regions = nr_regions;
>  
>  	nr_slots = nr_regions;
>  	if (sector_div(nr_slots, sctx->region_entries_per_slot))
> -- 
> 1.7.1
>