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Date: Thu, 25 Apr 2013 16:24:14 -0600
From: Alex Williamson <alex.williamson@...hat.com>
To: alex.williamson@...hat.com
Cc: linux-kernel@...r.kernel.org, kvm@...r.kernel.org, mst@...hat.com
Subject: [PATCH 1/2] vfio: Convert container->group_lock to rwsem
All current users are writers, maintaining current mutual exclusion.
This lets us add read users next.
Signed-off-by: Alex Williamson <alex.williamson@...hat.com>
---
drivers/vfio/vfio.c | 21 +++++++++++----------
1 file changed, 11 insertions(+), 10 deletions(-)
diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index 21eddd9..073788e 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -24,6 +24,7 @@
#include <linux/list.h>
#include <linux/module.h>
#include <linux/mutex.h>
+#include <linux/rwsem.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/string.h>
@@ -57,7 +58,7 @@ struct vfio_iommu_driver {
struct vfio_container {
struct kref kref;
struct list_head group_list;
- struct mutex group_lock;
+ struct rw_semaphore group_lock;
struct vfio_iommu_driver *iommu_driver;
void *iommu_data;
};
@@ -738,7 +739,7 @@ static long vfio_ioctl_check_extension(struct vfio_container *container,
return ret;
}
-/* hold container->group_lock */
+/* hold write lock on container->group_lock */
static int __vfio_container_attach_groups(struct vfio_container *container,
struct vfio_iommu_driver *driver,
void *data)
@@ -769,7 +770,7 @@ static long vfio_ioctl_set_iommu(struct vfio_container *container,
struct vfio_iommu_driver *driver;
long ret = -ENODEV;
- mutex_lock(&container->group_lock);
+ down_write(&container->group_lock);
/*
* The container is designed to be an unprivileged interface while
@@ -780,7 +781,7 @@ static long vfio_ioctl_set_iommu(struct vfio_container *container,
* the container is deprivileged and returns to an unset state.
*/
if (list_empty(&container->group_list) || container->iommu_driver) {
- mutex_unlock(&container->group_lock);
+ up_write(&container->group_lock);
return -EINVAL;
}
@@ -827,7 +828,7 @@ static long vfio_ioctl_set_iommu(struct vfio_container *container,
mutex_unlock(&vfio.iommu_drivers_lock);
skip_drivers_unlock:
- mutex_unlock(&container->group_lock);
+ up_write(&container->group_lock);
return ret;
}
@@ -882,7 +883,7 @@ static int vfio_fops_open(struct inode *inode, struct file *filep)
return -ENOMEM;
INIT_LIST_HEAD(&container->group_list);
- mutex_init(&container->group_lock);
+ init_rwsem(&container->group_lock);
kref_init(&container->kref);
filep->private_data = container;
@@ -961,7 +962,7 @@ static void __vfio_group_unset_container(struct vfio_group *group)
struct vfio_container *container = group->container;
struct vfio_iommu_driver *driver;
- mutex_lock(&container->group_lock);
+ down_write(&container->group_lock);
driver = container->iommu_driver;
if (driver)
@@ -979,7 +980,7 @@ static void __vfio_group_unset_container(struct vfio_group *group)
container->iommu_data = NULL;
}
- mutex_unlock(&container->group_lock);
+ up_write(&container->group_lock);
vfio_container_put(container);
}
@@ -1039,7 +1040,7 @@ static int vfio_group_set_container(struct vfio_group *group, int container_fd)
container = f.file->private_data;
WARN_ON(!container); /* fget ensures we don't race vfio_release */
- mutex_lock(&container->group_lock);
+ down_write(&container->group_lock);
driver = container->iommu_driver;
if (driver) {
@@ -1057,7 +1058,7 @@ static int vfio_group_set_container(struct vfio_group *group, int container_fd)
atomic_inc(&group->container_users);
unlock_out:
- mutex_unlock(&container->group_lock);
+ up_write(&container->group_lock);
fdput(f);
return ret;
}
--
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