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lib/iommu-helper: skip to next segment 

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).

Link: http://lkml.kernel.org/r/alpine.LFD.2.20.1606081910070.3211@schleppi
Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Reviewed-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Sebastian Ott 2016-08-02 14:04:13 -07:00 committed by Linus Torvalds
parent 4cad35a7ca
commit f003a1f182
1 changed files with 1 additions and 2 deletions
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3
lib/iommu-helper.c
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@ -29,8 +29,7 @@ unsigned long iommu_area_alloc(unsigned long *map, unsigned long size,
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);