linux-kernel - Re: [PATCH v5 5/8] dma-buf: Make .invalidate

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Message-ID: <20260130125545.GN10992@unreal>
Date: Fri, 30 Jan 2026 14:55:45 +0200
From: Leon Romanovsky <leon@...nel.org>
To: Christian König <christian.koenig@....com>
Cc: Sumit Semwal <sumit.semwal@...aro.org>,
	Alex Deucher <alexander.deucher@....com>,
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
	Gerd Hoffmann <kraxel@...hat.com>,
	Dmitry Osipenko <dmitry.osipenko@...labora.com>,
	Gurchetan Singh <gurchetansingh@...omium.org>,
	Chia-I Wu <olvaffe@...il.com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	Lucas De Marchi <lucas.demarchi@...el.com>,
	Thomas Hellström <thomas.hellstrom@...ux.intel.com>,
	Rodrigo Vivi <rodrigo.vivi@...el.com>,
	Jason Gunthorpe <jgg@...pe.ca>, Kevin Tian <kevin.tian@...el.com>,
	Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
	Robin Murphy <robin.murphy@....com>,
	Felix Kuehling <Felix.Kuehling@....com>,
	Alex Williamson <alex@...zbot.org>,
	Ankit Agrawal <ankita@...dia.com>,
	Vivek Kasireddy <vivek.kasireddy@...el.com>,
	linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org,
	linaro-mm-sig@...ts.linaro.org, linux-kernel@...r.kernel.org,
	amd-gfx@...ts.freedesktop.org, virtualization@...ts.linux.dev,
	intel-xe@...ts.freedesktop.org, linux-rdma@...r.kernel.org,
	iommu@...ts.linux.dev, kvm@...r.kernel.org
Subject: Re: [PATCH v5 5/8] dma-buf: Make .invalidate_mapping() truly optional

On Fri, Jan 30, 2026 at 09:30:05AM +0100, Christian König wrote:
> On 1/24/26 20:14, Leon Romanovsky wrote:
> > From: Leon Romanovsky <leonro@...dia.com>
> > 
> > The .invalidate_mapping() callback is documented as optional, yet it
> > effectively became mandatory whenever importer_ops were provided. This
> > led to cases where RDMA non-ODP code had to supply an empty stub.
> > 
> > Relax the checks in the dma-buf core so the callback can be omitted,
> > allowing RDMA code to drop the unnecessary function.
> > 
> > Removing the stub allows the next patch to tell that RDMA does not support
> > .invalidate_mapping() by checking for a NULL op.
> > 
> > Signed-off-by: Leon Romanovsky <leonro@...dia.com>
> > ---
> >  drivers/dma-buf/dma-buf.c             |  6 ++----
> >  drivers/infiniband/core/umem_dmabuf.c | 13 -------------
> >  2 files changed, 2 insertions(+), 17 deletions(-)
> > 
> > diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
> > index cd68c1c0bfd7..1629312d364a 100644
> > --- a/drivers/dma-buf/dma-buf.c
> > +++ b/drivers/dma-buf/dma-buf.c
> > @@ -947,9 +947,6 @@ dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct device *dev,
> >  	if (WARN_ON(!dmabuf || !dev))
> >  		return ERR_PTR(-EINVAL);
> >  
> > -	if (WARN_ON(importer_ops && !importer_ops->invalidate_mappings))
> > -		return ERR_PTR(-EINVAL);
> > -
> >  	attach = kzalloc(sizeof(*attach), GFP_KERNEL);
> >  	if (!attach)
> >  		return ERR_PTR(-ENOMEM);
> > @@ -1260,7 +1257,8 @@ void dma_buf_invalidate_mappings(struct dma_buf *dmabuf)
> >  	dma_resv_assert_held(dmabuf->resv);
> >  
> >  	list_for_each_entry(attach, &dmabuf->attachments, node)
> > -		if (attach->importer_ops)
> > +		if (attach->importer_ops &&
> > +		    attach->importer_ops->invalidate_mappings)
> >  			attach->importer_ops->invalidate_mappings(attach);
> >  }
> >  EXPORT_SYMBOL_NS_GPL(dma_buf_invalidate_mappings, "DMA_BUF");
> > diff --git a/drivers/infiniband/core/umem_dmabuf.c b/drivers/infiniband/core/umem_dmabuf.c
> > index d77a739cfe7a..256e34c15e6b 100644
> > --- a/drivers/infiniband/core/umem_dmabuf.c
> > +++ b/drivers/infiniband/core/umem_dmabuf.c
> > @@ -129,9 +129,6 @@ ib_umem_dmabuf_get_with_dma_device(struct ib_device *device,
> >  	if (check_add_overflow(offset, (unsigned long)size, &end))
> >  		return ret;
> >  
> > -	if (unlikely(!ops || !ops->invalidate_mappings))
> 
> You should probably keep "if (unlikely(!ops)).." here.

The unlikely is useless in this path.

> 
> Apart from that the patch looks good to me.
> 
> Regards,
> Christian.
> 
> > -		return ret;
> > -
> >  	dmabuf = dma_buf_get(fd);
> >  	if (IS_ERR(dmabuf))
> >  		return ERR_CAST(dmabuf);
> > @@ -184,18 +181,8 @@ struct ib_umem_dmabuf *ib_umem_dmabuf_get(struct ib_device *device,
> >  }
> >  EXPORT_SYMBOL(ib_umem_dmabuf_get);
> >  
> > -static void
> > -ib_umem_dmabuf_unsupported_move_notify(struct dma_buf_attachment *attach)
> > -{
> > -	struct ib_umem_dmabuf *umem_dmabuf = attach->importer_priv;
> > -
> > -	ibdev_warn_ratelimited(umem_dmabuf->umem.ibdev,
> > -			       "Invalidate callback should not be called when memory is pinned\n");
> > -}
> > -
> >  static struct dma_buf_attach_ops ib_umem_dmabuf_attach_pinned_ops = {
> >  	.allow_peer2peer = true,
> > -	.invalidate_mappings = ib_umem_dmabuf_unsupported_move_notify,
> >  };
> >  
> >  struct ib_umem_dmabuf *
> > 
>