Commit 912b74d2 authored by Jason Gunthorpe's avatar Jason Gunthorpe Committed by Alex Williamson
Browse files

vfio: Remove the vfio_group->users and users_comp 



Kevin points out that the users is really just tracking if
group->opened_file is set, so we can simplify this code to a wait_queue
that looks for !opened_file under the group_rwsem.

Signed-off-by: default avatarJason Gunthorpe <jgg@nvidia.com>
Reviewed-by: default avatarKevin Tian <kevin.tian@intel.com>
Link: https://lore.kernel.org/r/1-v1-917e3647f123+b1a-vfio_group_users_jgg@nvidia.com


Signed-off-by: default avatarAlex Williamson <alex.williamson@redhat.com>
parent 9c799c22

drivers/vfio/vfio.h

+1 −2
Original line number Diff line number Diff line
@@ -48,8 +48,6 @@ struct vfio_group { 
	 * reaches 0 then the iommu_group is invalid.

	 */

	refcount_t			drivers;

	refcount_t			users;

	struct completion		users_comp;

	unsigned int			container_users;

	struct iommu_group		*iommu_group;

	struct vfio_container		*container;
@@ -61,6 +59,7 @@ struct vfio_group { 
	struct rw_semaphore		group_rwsem;

	struct kvm			*kvm;

	struct file			*opened_file;

	struct swait_queue_head		opened_file_wait;

	struct blocking_notifier_head	notifier;

};

drivers/vfio/vfio_main.c

+19 −26
Original line number Diff line number Diff line
@@ -186,10 +186,9 @@ static struct vfio_group *vfio_group_alloc(struct iommu_group *iommu_group, 
	cdev_init(&group->cdev, &vfio_group_fops);

	group->cdev.owner = THIS_MODULE;



	refcount_set(&group->users, 1);

	refcount_set(&group->drivers, 1);

	init_completion(&group->users_comp);

	init_rwsem(&group->group_rwsem);

	init_swait_queue_head(&group->opened_file_wait);

	INIT_LIST_HEAD(&group->device_list);

	mutex_init(&group->device_lock);

	group->iommu_group = iommu_group;
@@ -245,12 +244,6 @@ static struct vfio_group *vfio_create_group(struct iommu_group *iommu_group, 
	return ret;

}



static void vfio_group_put(struct vfio_group *group)

{

	if (refcount_dec_and_test(&group->users))

		complete(&group->users_comp);

}



static void vfio_device_remove_group(struct vfio_device *device)

{

	struct vfio_group *group = device->group;
@@ -270,10 +263,6 @@ static void vfio_device_remove_group(struct vfio_device *device) 
	 * cdev_device_add() will fail due to the name aready existing.

	 */

	cdev_device_del(&group->cdev, &group->dev);

	mutex_unlock(&vfio.group_lock);



	/* Matches the get from vfio_group_alloc() */

	vfio_group_put(group);



	/*

	 * Before we allow the last driver in the group to be unplugged the
@@ -281,7 +270,13 @@ static void vfio_device_remove_group(struct vfio_device *device) 
	 * is because the group->iommu_group pointer should only be used so long

	 * as a device driver is attached to a device in the group.

	 */

	wait_for_completion(&group->users_comp);

	while (group->opened_file) {

		mutex_unlock(&vfio.group_lock);

		swait_event_idle_exclusive(group->opened_file_wait,

					   !group->opened_file);

		mutex_lock(&vfio.group_lock);

	}

	mutex_unlock(&vfio.group_lock);



	/*

	 * These data structures all have paired operations that can only be
@@ -906,15 +901,18 @@ static int vfio_group_fops_open(struct inode *inode, struct file *filep) 


	down_write(&group->group_rwsem);



	/* users can be zero if this races with vfio_device_remove_group() */

	if (!refcount_inc_not_zero(&group->users)) {

	/*

	 * drivers can be zero if this races with vfio_device_remove_group(), it

	 * will be stable at 0 under the group rwsem

	 */

	if (refcount_read(&group->drivers) == 0) {

		ret = -ENODEV;

		goto err_unlock;

		goto out_unlock;

	}



	if (group->type == VFIO_NO_IOMMU && !capable(CAP_SYS_RAWIO)) {

		ret = -EPERM;

		goto err_put;

		goto out_unlock;

	}



	/*
@@ -922,16 +920,12 @@ static int vfio_group_fops_open(struct inode *inode, struct file *filep) 
	 */

	if (group->opened_file) {

		ret = -EBUSY;

		goto err_put;

		goto out_unlock;

	}

	group->opened_file = filep;

	filep->private_data = group;



	up_write(&group->group_rwsem);

	return 0;

err_put:

	vfio_group_put(group);

err_unlock:

	ret = 0;

out_unlock:

	up_write(&group->group_rwsem);

	return ret;

}
@@ -952,8 +946,7 @@ static int vfio_group_fops_release(struct inode *inode, struct file *filep) 
		vfio_group_detach_container(group);

	group->opened_file = NULL;

	up_write(&group->group_rwsem);



	vfio_group_put(group);

	swake_up_one(&group->opened_file_wait);



	return 0;

}