linux-kernel - [PATCH 2/7] iommu/iova: cut down judgement times

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Date:   Wed, 22 Mar 2017 14:27:42 +0800
From:   Zhen Lei <thunder.leizhen@...wei.com>
To:     Joerg Roedel <joro@...tes.org>,
        iommu <iommu@...ts.linux-foundation.org>,
        Robin Murphy <robin.murphy@....com>,
        David Woodhouse <dwmw2@...radead.org>,
        Sudeep Dutt <sudeep.dutt@...el.com>,
        Ashutosh Dixit <ashutosh.dixit@...el.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
CC:     Zefan Li <lizefan@...wei.com>, Xinwei Hu <huxinwei@...wei.com>,
        "Tianhong Ding" <dingtianhong@...wei.com>,
        Hanjun Guo <guohanjun@...wei.com>,
        Zhen Lei <thunder.leizhen@...wei.com>
Subject: [PATCH 2/7] iommu/iova: cut down judgement times

Below judgement can only be satisfied at the last time, which produced 2N
judgements(suppose N times failed, 0 or 1 time successed) in vain.

if ((pfn >= iova->pfn_lo) && (pfn <= iova->pfn_hi)) {
	return iova;
}

Signed-off-by: Zhen Lei <thunder.leizhen@...wei.com>
---
 drivers/iommu/iova.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
index 8ba8b496..1c49969 100644
--- a/drivers/iommu/iova.c
+++ b/drivers/iommu/iova.c
@@ -312,15 +312,12 @@ 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;
-- 
2.5.0