Re: [RFC PATCH v2 16/19] RDMA/uverbs: Add back pointer to system file object

Jason Gunthorpe
2019-08-12T13:00:40Z

On Fri, Aug 09, 2019 at 03:58:30PM -0700, ira.weiny@intel.com wrote:
> From: Ira Weiny <ira.weiny@intel.com>
>
> In order for MRs to be tracked against the open verbs context the ufile
> needs to have a pointer to hand to the GUP code.
>
> No references need to be taken as this should be valid for the lifetime
> of the context.
>
> Signed-off-by: Ira Weiny <ira.weiny@intel.com>
> drivers/infiniband/core/uverbs.h | 1 +
> drivers/infiniband/core/uverbs_main.c | 1 +
> 2 files changed, 2 insertions(+)
>
> diff --git a/drivers/infiniband/core/uverbs.h b/drivers/infiniband/core/uverbs.h
> index 1e5aeb39f774..e802ba8c67d6 100644
> +++ b/drivers/infiniband/core/uverbs.h
> @@ -163,6 +163,7 @@ struct ib_uverbs_file {
> struct page *disassociate_page;
>
> struct xarray idr;
> + struct file *sys_file; /* backpointer to system file object */
> };

The 'struct file' has a lifetime strictly shorter than the
ib_uverbs_file, which is kref'd on its own lifetime. Having a back
pointer like this is confouding as it will be invalid for some of the
lifetime of the struct.

Jason