Re: [PATCH] xen-blkfront: use bitmap_set() and bitmap_clear()
From: Akinobu Mita
Date: Fri Jan 20 2012 - 10:42:11 EST
2012/1/21 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'?
'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 correct.
> Did you test this patch with a large amount of minors?
Sorry I didn't do runtime test.
>> 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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