[dm-devel] [PATCH v2] dm zoned: Silence a static checker warning

[Damien Le Moal]

On 2019/04/10 16:48, Dan Carpenter wrote:
> My static checker complains about this line from dmz_get_zoned_device()
> 
> 	aligned_capacity = dev->capacity & ~(blk_queue_zone_sectors(q) - 1);
> 
> The problem is that "aligned_capacity" and "dev->capacity" are sector_t
> type (which is a u64) but blk_queue_zone_sectors(q) returns a u32 so the
> higher 32 bits in "aligned_capacity" are always cleared to zero.  This
> patch adds a cast to u64 to address this issue.
> 
> Fixes: 114e025968b5 ("dm zoned: ignore last smaller runt zone")
> Signed-off-by: Dan Carpenter <dan.carpenter at oracle.com>
> ---
> v2: In v1 I changed blk_queue_zone_sectors() to return a sector_t type,
> but in v2 I just add a cast.  The v2 fix would end up going through
> different maintainers and reviewers so the CC list has grown...
> 
> Original discussion: https://marc.info/?l=kernel-janitors&m=155487663405737&w=2
> 
>  drivers/md/dm-zoned-target.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/md/dm-zoned-target.c b/drivers/md/dm-zoned-target.c
> index 8865c1709e16..b6cb44fa946d 100644
> --- a/drivers/md/dm-zoned-target.c
> +++ b/drivers/md/dm-zoned-target.c
> @@ -643,7 +643,8 @@ static int dmz_get_zoned_device(struct dm_target *ti, char *path)
>  
>  	q = bdev_get_queue(dev->bdev);
>  	dev->capacity = i_size_read(dev->bdev->bd_inode) >> SECTOR_SHIFT;
> -	aligned_capacity = dev->capacity & ~(blk_queue_zone_sectors(q) - 1);
> +	aligned_capacity = dev->capacity &
> +				~((u64)blk_queue_zone_sectors(q) - 1);

sector_t is an u64 only if CONFIG_LBDAF is defined (I think this option is going
away though). Otherwise it is an unsigned long which would be u32 on 32 bits
arch. Not a problem in terms of arithmetic, but why not cast to sector_t directly ?

>  	if (ti->begin ||
>  	    ((ti->len != dev->capacity) && (ti->len != aligned_capacity))) {
>  		ti->error = "Partial mapping not supported";
> 
-- 
Damien Le Moal
Western Digital Research