vfio: Split up vfio_group_get_device_fd()

The split follows the pairing with the destroy functions:

 - vfio_group_get_device_fd() destroyed by close()

 - vfio_device_open() destroyed by vfio_device_fops_release()

 - vfio_device_assign_container() destroyed by
   vfio_group_try_dissolve_container()

The next patch will put a lock around vfio_device_assign_container().

Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Tested-by: Matthew Rosato <mjrosato@linux.ibm.com>
Link: https://lore.kernel.org/r/3-v2-d035a1842d81+1bf-vfio_group_locking_jgg@nvidia.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index 12d4b3efd4639ec6f1dba511ef563f8ee62ba7ad..21db0e8d0d4004d91fd5330d77257e4be8ac78c1 100644 (file)
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -1064,12 +1064,9 @@ static bool vfio_assert_device_open(struct vfio_device *device)
        return !WARN_ON_ONCE(!READ_ONCE(device->open_count));
 }
 
-static int vfio_group_get_device_fd(struct vfio_group *group, char *buf)
+static int vfio_device_assign_container(struct vfio_device *device)
 {
-       struct vfio_device *device;
-       struct file *filep;
-       int fdno;
-       int ret = 0;
+       struct vfio_group *group = device->group;
 
        if (0 == atomic_read(&group->container_users) ||
            !group->container->iommu_driver)
@@ -1078,13 +1075,22 @@ static int vfio_group_get_device_fd(struct vfio_group *group, char *buf)
        if (group->type == VFIO_NO_IOMMU && !capable(CAP_SYS_RAWIO))
                return -EPERM;
 
-       device = vfio_device_get_from_name(group, buf);
-       if (IS_ERR(device))
-               return PTR_ERR(device);
+       atomic_inc(&group->container_users);
+       return 0;
+}
+
+static struct file *vfio_device_open(struct vfio_device *device)
+{
+       struct file *filep;
+       int ret;
+
+       ret = vfio_device_assign_container(device);
+       if (ret)
+               return ERR_PTR(ret);
 
        if (!try_module_get(device->dev->driver->owner)) {
                ret = -ENODEV;
-               goto err_device_put;
+               goto err_unassign_container;
        }
 
        mutex_lock(&device->dev_set->lock);
@@ -1100,15 +1106,11 @@ static int vfio_group_get_device_fd(struct vfio_group *group, char *buf)
         * We can't use anon_inode_getfd() because we need to modify
         * the f_mode flags directly to allow more than just ioctls
         */
-       fdno = ret = get_unused_fd_flags(O_CLOEXEC);
-       if (ret < 0)
-               goto err_close_device;
-
        filep = anon_inode_getfile("[vfio-device]", &vfio_device_fops,
                                   device, O_RDWR);
        if (IS_ERR(filep)) {
                ret = PTR_ERR(filep);
-               goto err_fd;
+               goto err_close_device;
        }
 
        /*
@@ -1118,17 +1120,15 @@ static int vfio_group_get_device_fd(struct vfio_group *group, char *buf)
         */
        filep->f_mode |= (FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE);
 
-       atomic_inc(&group->container_users);
-
-       fd_install(fdno, filep);
-
-       if (group->type == VFIO_NO_IOMMU)
+       if (device->group->type == VFIO_NO_IOMMU)
                dev_warn(device->dev, "vfio-noiommu device opened by user "
                         "(%s:%d)\n", current->comm, task_pid_nr(current));
-       return fdno;
+       /*
+        * On success the ref of device is moved to the file and
+        * put in vfio_device_fops_release()
+        */
+       return filep;
 
-err_fd:
-       put_unused_fd(fdno);
 err_close_device:
        mutex_lock(&device->dev_set->lock);
        if (device->open_count == 1 && device->ops->close_device)
@@ -1137,7 +1137,40 @@ err_undo_count:
        device->open_count--;
        mutex_unlock(&device->dev_set->lock);
        module_put(device->dev->driver->owner);
-err_device_put:
+err_unassign_container:
+       vfio_group_try_dissolve_container(device->group);
+       return ERR_PTR(ret);
+}
+
+static int vfio_group_get_device_fd(struct vfio_group *group, char *buf)
+{
+       struct vfio_device *device;
+       struct file *filep;
+       int fdno;
+       int ret;
+
+       device = vfio_device_get_from_name(group, buf);
+       if (IS_ERR(device))
+               return PTR_ERR(device);
+
+       fdno = get_unused_fd_flags(O_CLOEXEC);
+       if (fdno < 0) {
+               ret = fdno;
+               goto err_put_device;
+       }
+
+       filep = vfio_device_open(device);
+       if (IS_ERR(filep)) {
+               ret = PTR_ERR(filep);
+               goto err_put_fdno;
+       }
+
+       fd_install(fdno, filep);
+       return fdno;
+
+err_put_fdno:
+       put_unused_fd(fdno);
+err_put_device:
        vfio_device_put(device);
        return ret;
 }