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vfio: Remove the vfio_group->users and users_comp

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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: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Link: https://lore.kernel.org/r/1-v1-917e3647f123+b1a-vfio_group_users_jgg@nvidia.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
This commit is contained in:
Jason Gunthorpe 2022-09-29 11:59:24 -03:00 committed by Alex Williamson
parent 9c799c224d
commit 912b74d26c
2 changed files with 20 additions and 28 deletions
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3
drivers/vfio/vfio.h
View File

@ -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;
};

45
drivers/vfio/vfio_main.c
View File

@ -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 @@ err_put:
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;
}