Re: [PATCH] iommufd: take dma_resv lock before dma_buf_unpin() in release path

[Jason Gunthorpe]

On Tue, May 26, 2026 at 11:10:34AM +0000, Ankit Soni wrote:
> dma_buf_unpin() requires the caller to hold the exporter's dma_resv
> lock:
> 
>   void dma_buf_unpin(struct dma_buf_attachment *attach)
>   {
>           ...
>           dma_resv_assert_held(dmabuf->resv);
>           ...
>   }
> 
> iopt_release_pages() calls dma_buf_unpin() without taking that lock,
> so every iommufd_ioas_destroy()/iommufd_ioas_unmap() that releases
> the last reference on a DMABUF-backed iopt_pages triggers a WARN.
> This was hit while running tools/testing/selftests/iommu/iommufd:

Any idea why this is comming up now? Did I run the tests without some
kind of debug option to turn on that assertion maybe?

Jason