linux-kernel - [PATCH 1/1] vfio: put off the allocation of "minor" in vfio_create

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Date:	Thu, 20 Nov 2014 19:25:02 +0800
From:	Zhen Lei <thunder.leizhen@...wei.com>
To:	Alex Williamson <alex.williamson@...hat.com>,
	KVM <kvm@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
CC:	Zefan Li <lizefan@...wei.com>, Xinwei Hu <huxinwei@...wei.com>,
	"Tianhong Ding" <dingtianhong@...wei.com>,
	Kefeng Wang <wangkefeng.wang@...wei.com>,
	Zhen Lei <thunder.leizhen@...wei.com>
Subject: [PATCH 1/1] vfio: put off the allocation of "minor" in vfio_create_group

The next code fragment "list_for_each_entry" is not depend on "minor". With this
patch, the free of "minor" in "list_for_each_entry" can be reduced, and there is
no functional change.

Signed-off-by: Zhen Lei <thunder.leizhen@...wei.com>
---
 drivers/vfio/vfio.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index f018d8d..737eb468 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -225,22 +225,21 @@ static struct vfio_group *vfio_create_group(struct iommu_group *iommu_group)

 	mutex_lock(&vfio.group_lock);

-	minor = vfio_alloc_group_minor(group);
-	if (minor < 0) {
-		vfio_group_unlock_and_free(group);
-		return ERR_PTR(minor);
-	}
-
 	/* Did we race creating this group? */
 	list_for_each_entry(tmp, &vfio.group_list, vfio_next) {
 		if (tmp->iommu_group == iommu_group) {
 			vfio_group_get(tmp);
-			vfio_free_group_minor(minor);
 			vfio_group_unlock_and_free(group);
 			return tmp;
 		}
 	}

+	minor = vfio_alloc_group_minor(group);
+	if (minor < 0) {
+		vfio_group_unlock_and_free(group);
+		return ERR_PTR(minor);
+	}
+
 	dev = device_create(vfio.class, NULL,
 			    MKDEV(MAJOR(vfio.group_devt), minor),
 			    group, "%d", iommu_group_id(iommu_group));
--
1.8.0


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