linux-kernel - [PATCH 2/2] mm, vmalloc: use well-defined find_last

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Message-Id: <1375408621-16563-2-git-send-email-iamjoonsoo.kim@lge.com>
Date:	Fri,  2 Aug 2013 10:57:01 +0900
From:	Joonsoo Kim <iamjoonsoo.kim@....com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Zhang Yanfei <zhangyanfei@...fujitsu.com>,
	Joonsoo Kim <js1304@...il.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: [PATCH 2/2] mm, vmalloc: use well-defined find_last_bit() func

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@....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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