linux-kernel - [PATCH 2/2] iommu: avoid taking iova_rbtree

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Date:   Fri, 25 Sep 2020 17:51:09 +0800
From:   John Garry <john.garry@...wei.com>
To:     <joro@...tes.org>, <robin.murphy@....com>
CC:     <iommu@...ts.linux-foundation.org>, <linux-kernel@...r.kernel.org>,
        <chenxiang66@...ilicon.com>, <linuxarm@...wei.com>,
        <xiyou.wangcong@...il.com>, <thunder.leizhen@...wei.com>,
        John Garry <john.garry@...wei.com>
Subject: [PATCH 2/2] iommu: avoid taking iova_rbtree_lock twice

From: Cong Wang <xiyou.wangcong@...il.com>

Both find_iova() and __free_iova() take iova_rbtree_lock,
there is no reason to take and release it twice inside
free_iova().

Fold them into one critical section by calling the unlock
versions instead.

Signed-off-by: Cong Wang <xiyou.wangcong@...il.com>
Reviewed-by: Robin Murphy <robin.murphy@....com>
Tested-by: Xiang Chen <chenxiang66@...ilicon.com>
Signed-off-by: John Garry <john.garry@...wei.com>
---
 drivers/iommu/iova.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
index 05e0b462e0d9..921e80f64ae5 100644
--- a/drivers/iommu/iova.c
+++ b/drivers/iommu/iova.c
@@ -390,10 +390,14 @@ EXPORT_SYMBOL_GPL(__free_iova);
 void
 free_iova(struct iova_domain *iovad, unsigned long pfn)
 {
-	struct iova *iova = find_iova(iovad, pfn);
+	unsigned long flags;
+	struct iova *iova;
 
+	spin_lock_irqsave(&iovad->iova_rbtree_lock, flags);
+	iova = private_find_iova(iovad, pfn);
 	if (iova)
-		__free_iova(iovad, iova);
+		private_free_iova(iovad, iova);
+	spin_unlock_irqrestore(&iovad->iova_rbtree_lock, flags);
 
 }
 EXPORT_SYMBOL_GPL(free_iova);
-- 
2.26.2