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From:   Ben Luo <luoben@linux.alibaba.com>
To:     alex.williamson@redhat.com, cohuck@redhat.com
Cc:     linux-kernel@vger.kernel.org
Subject: [PATCH] vfio/type1: avoid redundant PageReserved checking
Date:   Tue, 27 Aug 2019 20:49:48 +0800
Message-Id: <3e892a6bdaa069a6e79c50208bd01cab8c9588ac.1566910119.git.luoben@linux.alibaba.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

currently, if the page is not a tail of compound page, it will be
checked twice for the same thing.

Signed-off-by: Ben Luo <luoben@linux.alibaba.com>
---
 drivers/vfio/vfio_iommu_type1.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 054391f..cbe0d88 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -291,11 +291,10 @@ static int vfio_lock_acct(struct vfio_dma *dma, long npage, bool async)
 static bool is_invalid_reserved_pfn(unsigned long pfn)
 {
 	if (pfn_valid(pfn)) {
-		bool reserved;
 		struct page *tail = pfn_to_page(pfn);
 		struct page *head = compound_head(tail);
-		reserved = !!(PageReserved(head));
 		if (head != tail) {
+			bool reserved = !!(PageReserved(head));
 			/*
 			 * "head" is not a dangling pointer
 			 * (compound_head takes care of that)
@@ -310,7 +309,7 @@ static bool is_invalid_reserved_pfn(unsigned long pfn)
 			if (PageTail(tail))
 				return reserved;
 		}
-		return PageReserved(tail);
+		return !!(PageReserved(tail));
 	}
 
 	return true;
-- 
1.8.3.1