linux-kernel - [RFC PATCH 2/3] vfio/type1: Replace obvious read lock instances

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Message-ID: <157919868571.21002.6651113746893305820.stgit@gimli.home>
Date:   Thu, 16 Jan 2020 11:18:05 -0700
From:   Alex Williamson <alex.williamson@...hat.com>
To:     yan.y.zhao@...el.com
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [RFC PATCH 2/3] vfio/type1: Replace obvious read lock instances

Replace some instances where no internal state is changed to read locks.

Signed-off-by: Alex Williamson <alex.williamson@...hat.com>
---
 drivers/vfio/vfio_iommu_type1.c |   12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 7ae58350af5b..e78067cc74b3 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -830,10 +830,10 @@ static unsigned long vfio_pgsize_bitmap(struct vfio_iommu *iommu)
 	struct vfio_domain *domain;
 	unsigned long bitmap = ULONG_MAX;
 
-	down_write(&iommu->lock);
+	down_read(&iommu->lock);
 	list_for_each_entry(domain, &iommu->domain_list, next)
 		bitmap &= domain->domain->pgsize_bitmap;
-	up_write(&iommu->lock);
+	up_read(&iommu->lock);
 
 	/*
 	 * In case the IOMMU supports page sizes smaller than PAGE_SIZE
@@ -2115,14 +2115,14 @@ static int vfio_domains_have_iommu_cache(struct vfio_iommu *iommu)
 	struct vfio_domain *domain;
 	int ret = 1;
 
-	down_write(&iommu->lock);
+	down_read(&iommu->lock);
 	list_for_each_entry(domain, &iommu->domain_list, next) {
 		if (!(domain->prot & IOMMU_CACHE)) {
 			ret = 0;
 			break;
 		}
 	}
-	up_write(&iommu->lock);
+	up_read(&iommu->lock);
 
 	return ret;
 }
@@ -2156,7 +2156,7 @@ static int vfio_iommu_iova_build_caps(struct vfio_iommu *iommu,
 	size_t size;
 	int iovas = 0, i = 0, ret;
 
-	down_write(&iommu->lock);
+	down_read(&iommu->lock);
 
 	list_for_each_entry(iova, &iommu->iova_list, list)
 		iovas++;
@@ -2190,7 +2190,7 @@ static int vfio_iommu_iova_build_caps(struct vfio_iommu *iommu,
 
 	kfree(cap_iovas);
 out_unlock:
-	up_write(&iommu->lock);
+	up_read(&iommu->lock);
 	return ret;
 }