On Thu, Jul 27, 2023 at 12:23:08AM -0700, Nicolin Chen wrote:
The complication of the mutex and refcount will be amplified after we introduce the replace support for access. So, add a preparatory change of a constitutive helper iommufd_access_change_ioas(), to take care of the existing iommufd_access_attach() and iommufd_access_detach().
Also, update the unprotect routine in iommufd_access_destroy_object() to calling the new iommufd_access_change_ioas() helper.
Suggested-by: Jason Gunthorpe jgg@nvidia.com Signed-off-by: Nicolin Chen nicolinc@nvidia.com
drivers/iommu/iommufd/device.c | 112 ++++++++++++++++++++------------- 1 file changed, 69 insertions(+), 43 deletions(-)
diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c index 7a3e8660b902..d9680a247e1c 100644 --- a/drivers/iommu/iommufd/device.c +++ b/drivers/iommu/iommufd/device.c @@ -684,17 +684,69 @@ void iommufd_device_detach(struct iommufd_device *idev) } EXPORT_SYMBOL_NS_GPL(iommufd_device_detach, IOMMUFD); +static int iommufd_access_change_ioas(struct iommufd_access *access,
struct iommufd_ioas *new_ioas)
+{
- u32 iopt_access_list_id = access->iopt_access_list_id;
- struct iommufd_ioas *cur_ioas = access->ioas;
- int rc;
- lockdep_assert_held(&access->ioas_lock);
- /* We are racing with a concurrent detach, bail */
- if (cur_ioas != access->ioas_unpin)
return -EBUSY;
- if (IS_ERR(new_ioas))
return PTR_ERR(new_ioas);
- if (cur_ioas == new_ioas) {
/* Do not forget to put since we allow a duplication */
iommufd_put_object(&new_ioas->obj);
return 0;
- }
- /*
* Set ioas to NULL to block any further iommufd_access_pin_pages().
* iommufd_access_unpin_pages() can continue using access->ioas_unpin.
*/
- access->ioas = NULL;
- if (new_ioas) {
rc = iopt_add_access(&new_ioas->iopt, access);
if (rc) {
iommufd_put_object(&new_ioas->obj);
access->ioas = cur_ioas;
return rc;
}
iommufd_ref_to_users(&new_ioas->obj);
Kevin's suggestion to just open code the refcount_inc here
And have a wrapper func that does:
iommufd_access_change_ioas_id(struct iommufd_access *access, u32 id) { struct iommufd_ioas *ioas = iommufd_get_ioas(ictx, ioas_id); int rc;
if (IS_ERR(ioas)) return PTR_ERR(ioas); rc = iommufd_access_change_ioas(access, ioas); iommufd_put_object(&ioas->obj); return rc; }
Does looks cleaner
Then we delete iommufd_ref_to_users() as there are no users (once all the branches are merged).
Logic looks OK otherwise
Jason