Re: [PATCH 2/2] mm, vmalloc: use well-defined find_last_bit() func

[Wanpeng Li <liwanp@linux.vnet.ibm.com>]

On Fri, Aug 02, 2013 at 10:57:01AM +0900, Joonsoo Kim wrote:
>Our intention in here is to find last_bit within the region to flush.
>There is well-defined function, find_last_bit() for this purpose and
>it's performance may be slightly better than current implementation.
>So change it.
>
>Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>

Reviewed-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>

>
>diff --git a/mm/vmalloc.c b/mm/vmalloc.c
>index d23c432..93d3182 100644
>--- a/mm/vmalloc.c
>+++ b/mm/vmalloc.c
>@@ -1016,15 +1016,16 @@ void vm_unmap_aliases(void)
>
> 		rcu_read_lock();
> 		list_for_each_entry_rcu(vb, &vbq->free, free_list) {
>-			int i;
>+			int i, j;
>
> 			spin_lock(&vb->lock);
> 			i = find_first_bit(vb->dirty_map, VMAP_BBMAP_BITS);
>-			while (i < VMAP_BBMAP_BITS) {
>+			if (i < VMAP_BBMAP_BITS) {
> 				unsigned long s, e;
>-				int j;
>-				j = find_next_zero_bit(vb->dirty_map,
>-					VMAP_BBMAP_BITS, i);
>+
>+				j = find_last_bit(vb->dirty_map,
>+							VMAP_BBMAP_BITS);
>+				j = j + 1; /* need exclusive index */
>
> 				s = vb->va->va_start + (i << PAGE_SHIFT);
> 				e = vb->va->va_start + (j << PAGE_SHIFT);
>@@ -1034,10 +1035,6 @@ void vm_unmap_aliases(void)
> 					start = s;
> 				if (e > end)
> 					end = e;
>-
>-				i = j;
>-				i = find_next_bit(vb->dirty_map,
>-							VMAP_BBMAP_BITS, i);
> 			}
> 			spin_unlock(&vb->lock);
> 		}
>-- 
>1.7.9.5
>
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