[PATCH] lib/iommu-helper: skip to next segment

[PATCH] lib/iommu-helper: skip to next segment

[Sebastian Ott]

When a large enough area in the iommu bitmap is found but would
span a boundary we continue the search starting from the next
bit position. For large allocations this can lead to several
useless invocations of bitmap_find_next_zero_area() and
iommu_is_span_boundary().

Continue the search from the start of the next segment (which is
the next bit position such that we'll not cross the same segment
boundary again).

Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Reviewed-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
---
 lib/iommu-helper.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/lib/iommu-helper.c b/lib/iommu-helper.c
index c27e269..a816f3a 100644
--- a/lib/iommu-helper.c
+++ b/lib/iommu-helper.c
@@ -29,8 +29,7 @@ again:
 	index = bitmap_find_next_zero_area(map, size, start, nr, align_mask);
 	if (index < size) {
 		if (iommu_is_span_boundary(index, nr, shift, boundary_size)) {
-			/* we could do more effectively */
-			start = index + 1;
+			start = ALIGN(shift + index, boundary_size) - shift;
 			goto again;
 		}
 		bitmap_set(map, index, nr);
-- 
2.3.0