[PATCH AUTOSEL 4.9 09/74] mm/cma_debug.c: fix the break condition in cma_maxchunk_get()

[Sasha Levin]

From: Yue Hu <huyue2@xxxxxxxxxx>

[ Upstream commit f0fd50504a54f5548eb666dc16ddf8394e44e4b7 ]

If not find zero bit in find_next_zero_bit(), it will return the size
parameter passed in, so the start bit should be compared with bitmap_maxno
rather than cma->count.  Although getting maxchunk is working fine due to
zero value of order_per_bit currently, the operation will be stuck if
order_per_bit is set as non-zero.

Link: http://lkml.kernel.org/r/20190319092734.276-1-zbestahu@xxxxxxxxx
Signed-off-by: Yue Hu <huyue2@xxxxxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Joe Perches <joe@xxxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Dmitry Safonov <d.safonov@xxxxxxxxxxxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 mm/cma_debug.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/cma_debug.c b/mm/cma_debug.c
index f8e4b60db1672..da50dab56b700 100644
--- a/mm/cma_debug.c
+++ b/mm/cma_debug.c
@@ -57,7 +57,7 @@ static int cma_maxchunk_get(void *data, u64 *val)
 	mutex_lock(&cma->lock);
 	for (;;) {
 		start = find_next_zero_bit(cma->bitmap, bitmap_maxno, end);
-		if (start >= cma->count)
+		if (start >= bitmap_maxno)
 			break;
 		end = find_next_bit(cma->bitmap, bitmap_maxno, start);
 		maxchunk = max(end - start, maxchunk);
-- 
2.20.1