linux-kernel - [Patch v3 3/3] iommu: avoid taking iova_rbtree

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Message-Id: <20191218043951.10534-4-xiyou.wangcong@gmail.com>
Date:   Tue, 17 Dec 2019 20:39:51 -0800
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     iommu@...ts.linux-foundation.org
Cc:     robin.murphy@....com, linux-kernel@...r.kernel.org,
        joro@...tes.org, Cong Wang <xiyou.wangcong@...il.com>,
        John Garry <john.garry@...wei.com>
Subject: [Patch v3 3/3] iommu: avoid taking iova_rbtree_lock twice

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.

Cc: Joerg Roedel <joro@...tes.org>
Cc: John Garry <john.garry@...wei.com>
Signed-off-by: Cong Wang <xiyou.wangcong@...il.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 184d4c0e20b5..f46f8f794678 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);
-- 
2.21.0