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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@redhat.com>
This commit is contained in:
Alex Williamson 2013-04-25 16:12:38 -06:00
parent aa2cba51a0
commit 9587f44aa6
1 changed files with 11 additions and 10 deletions
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21
drivers/vfio/vfio.c
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@ -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;
}