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

[Dan Carpenter <dan.carpenter@oracle.com>]

On Wed, Apr 10, 2019 at 07:56:14AM +0000, Damien Le Moal wrote:
> 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@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 ?
> 

I would have prefered to do that but I didn't have strong feelings
either way.  I am always slight annoyed when people don't just copy and
paste my code when I tell them how to fix a patch so I decided to go
with your version...  :P

regards,
dan carpenter