Re: [Xen-devel] [PATCH] xen-blkfront: use bitmap_set() and bitmap_clear()

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Sat, Jan 21, 2012 at 12:15:26AM +0900, Akinobu Mita wrote:
> Use bitmap_set and bitmap_clear rather than modifying individual bits
> in a memory region.
> 
> Signed-off-by: Akinobu Mita <akinobu.mita@xxxxxxxxx>
> Cc: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
> Cc: virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx
> ---
>  drivers/block/xen-blkfront.c |    7 +++----
>  1 files changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
> index 2f22874..619868d 100644
> --- a/drivers/block/xen-blkfront.c
> +++ b/drivers/block/xen-blkfront.c
> @@ -43,6 +43,7 @@
>  #include <linux/slab.h>
>  #include <linux/mutex.h>
>  #include <linux/scatterlist.h>
> +#include <linux/bitmap.h>
>  
>  #include <xen/xen.h>
>  #include <xen/xenbus.h>
> @@ -177,8 +178,7 @@ static int xlbd_reserve_minors(unsigned int minor, 
> unsigned int nr)
>  
>       spin_lock(&minor_lock);
>       if (find_next_bit(minors, end, minor) >= end) {
> -             for (; minor < end; ++minor)
> -                     __set_bit(minor, minors);
> +             bitmap_set(minors, minor, nr);

Hm, I would have thought the last argument should have been 'end'?

Did you test this patch with a large amount of minors?

>               rc = 0;
>       } else
>               rc = -EBUSY;
> @@ -193,8 +193,7 @@ static void xlbd_release_minors(unsigned int minor, 
> unsigned int nr)
>  
>       BUG_ON(end > nr_minors);
>       spin_lock(&minor_lock);
> -     for (; minor < end; ++minor)
> -             __clear_bit(minor, minors);
> +     bitmap_clear(minors,  minor, nr);

Ditto.
>       spin_unlock(&minor_lock);
>  }
>  
> -- 
> 1.7.4.4
> 
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