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authorZhen Lei <thunder.leizhen@huawei.com>2017-09-21 18:52:42 +0300
committerJoerg Roedel <jroedel@suse.de>2017-09-27 18:09:56 +0300
commit2070f940a6d5148cf2df0d0087ff0a64d9f15237 (patch)
tree33eaa069e7e259009034651a3241ee8318ee55b9 /drivers/iommu/iova.c
parente19b205be43d11bff638cad4487008c48d21c103 (diff)
downloadlinux-2070f940a6d5148cf2df0d0087ff0a64d9f15237.tar.xz
iommu/iova: Optimise rbtree searching
Checking the IOVA bounds separately before deciding which direction to continue the search (if necessary) results in redundantly comparing both pfns twice each. GCC can already determine that the final comparison op is redundant and optimise it down to 3 in total, but we can go one further with a little tweak of the ordering (which makes the intent of the code that much cleaner as a bonus). Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Tested-by: Zhen Lei <thunder.leizhen@huawei.com> Tested-by: Nate Watterson <nwatters@codeaurora.org> [rm: rewrote commit message to clarify] Signed-off-by: Robin Murphy <robin.murphy@arm.com> Signed-off-by: Joerg Roedel <jroedel@suse.de>
Diffstat (limited to 'drivers/iommu/iova.c')
-rw-r--r--drivers/iommu/iova.c9
1 files changed, 3 insertions, 6 deletions
diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
index 33edfa794ae9..f129ff4f5c89 100644
--- a/drivers/iommu/iova.c
+++ b/drivers/iommu/iova.c
@@ -342,15 +342,12 @@ private_find_iova(struct iova_domain *iovad, unsigned long pfn)
while (node) {
struct iova *iova = rb_entry(node, struct iova, node);
- /* If pfn falls within iova's range, return iova */
- if ((pfn >= iova->pfn_lo) && (pfn <= iova->pfn_hi)) {
- return iova;
- }
-
if (pfn < iova->pfn_lo)
node = node->rb_left;
- else if (pfn > iova->pfn_lo)
+ else if (pfn > iova->pfn_hi)
node = node->rb_right;
+ else
+ return iova; /* pfn falls within iova's range */
}
return NULL;