Virtualization - Jan 2012 - [PATCH] xen-blkfront: use bitmap_set() and bitmap_clear()

Use bitmap_set and bitmap_clear rather than modifying individual bits
in a memory region.

Signed-off-by: Akinobu Mita <akinobu.mita at gmail.com>
Cc: Jeremy Fitzhardinge <jeremy.fitzhardinge at citrix.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk at oracle.com>
Cc: xen-devel at lists.xensource.com
Cc: virtualization at lists.linux-foundation.org
---
 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);
 		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);
 	spin_unlock(&minor_lock);
 }
 
-- 
1.7.4.4

I used Jeremy Fitzhardinge's old email address...

2012/1/21 Akinobu Mita <akinobu.mita at
gmail.com>:
> Use bitmap_set and bitmap_clear rather than modifying individual bits
> in a memory region.
>
> Signed-off-by: Akinobu Mita <akinobu.mita at gmail.com>
> Cc: Jeremy Fitzhardinge <jeremy.fitzhardinge at citrix.com>
Cc: Jeremy Fitzhardinge <jeremy at goop.org>
> Cc: Konrad Rzeszutek Wilk <konrad.wilk at oracle.com>
> Cc: xen-devel at lists.xensource.com
> Cc: virtualization at lists.linux-foundation.org
> ---
> ?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);
> ? ? ? ? ? ? ? ?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);
> ? ? ? ?spin_unlock(&minor_lock);
> ?}
>
> --
> 1.7.4.4
>

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 at gmail.com>
> Cc: Jeremy Fitzhardinge <jeremy.fitzhardinge at citrix.com>
> Cc: Konrad Rzeszutek Wilk <konrad.wilk at oracle.com>
> Cc: xen-devel at lists.xensource.com
> Cc: virtualization at lists.linux-foundation.org
> ---
>  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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