From mboxrd@z Thu Jan  1 00:00:00 1970
From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Subject: Re: [PATCH] xen-blkfront: use bitmap_set() and bitmap_clear()
Date: Fri, 20 Jan 2012 11:09:38 -0500
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To: Akinobu Mita <akinobu.mita@gmail.com>
Cc: akpm@linux-foundation.org, xen-devel@lists.xensource.com, linux-kernel@vger.kernel.org, Jeremy Fitzhardinge Jeremy Fitzhardinge <jeremy@goop.org>, virtualization@lists.linux-foundation.org
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On Sat, Jan 21, 2012 at 12:41:56AM +0900, Akinobu Mita wrote:
> 2012/1/21 Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>:
> > 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@gmail.com>
> >> Cc: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
> >> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> >> Cc: xen-devel@lists.xensource.com
> >> Cc: virtualization@lists.linux-foundation.org
> >> ---
> >> =A0drivers/block/xen-blkfront.c | =A0 =A07 +++----
> >> =A01 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 @@
> >> =A0#include <linux/slab.h>
> >> =A0#include <linux/mutex.h>
> >> =A0#include <linux/scatterlist.h>
> >> +#include <linux/bitmap.h>
> >>
> >> =A0#include <xen/xen.h>
> >> =A0#include <xen/xenbus.h>
> >> @@ -177,8 +178,7 @@ static int xlbd_reserve_minors(unsigned int minor,=
 unsigned int nr)
> >>
> >> =A0 =A0 =A0 spin_lock(&minor_lock);
> >> =A0 =A0 =A0 if (find_next_bit(minors, end, minor) >=3D end) {
> >> - =A0 =A0 =A0 =A0 =A0 =A0 for (; minor < end; ++minor)
> >> - =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 __set_bit(minor, minors);
> >> + =A0 =A0 =A0 =A0 =A0 =A0 bitmap_set(minors, minor, nr);
> >
> > Hm, I would have thought the last argument should have been 'end'?
> =

> 'end' is the index of the last bit to clear.  But the last argument of
> bitmap_clear() is the number of bits to clear.  So I think 'nr' is correc=
t.

Ah, I see it.
> =

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

> Sorry I didn't do runtime test.

Please do.