On Wed, Jan 21, 2026 at 09:59:59AM +0100, Christian König wrote: > On 1/20/26 15:07, Leon Romanovsky wrote: > > From: Leon Romanovsky <[email protected]> > > > > 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 just to > > provide allow_peer2peer. > > > > Document this behavior by creating a dedicated export for the > > dma_buf_unsupported_invalidate_mappings() function. This function is > > intended solely for the RDMA non-ODP case and must not be used by any > > other dma-buf importer. > > > > This makes it possible to rely on a valid .invalidate_mappings() > > callback to determine whether an importer supports revocation. > > > > Signed-off-by: Leon Romanovsky <[email protected]> > > --- > > drivers/dma-buf/dma-buf.c | 14 ++++++++++++++ > > drivers/infiniband/core/umem_dmabuf.c | 11 +---------- > > include/linux/dma-buf.h | 4 +++- > > 3 files changed, 18 insertions(+), 11 deletions(-) > > > > diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c > > index cd3b60ce4863..c4fa35034b92 100644 > > --- a/drivers/dma-buf/dma-buf.c > > +++ b/drivers/dma-buf/dma-buf.c > > @@ -1238,6 +1238,20 @@ void dma_buf_unmap_attachment_unlocked(struct > > dma_buf_attachment *attach, > > } > > EXPORT_SYMBOL_NS_GPL(dma_buf_unmap_attachment_unlocked, "DMA_BUF"); > > > > +/* > > + * This function shouldn't be used by anyone except RDMA non-ODP case. > > + * The reason to it is UAPI mistake where dma-buf was exported to the > > + * userspace without knowing that .invalidate_mappings() can be called > > + * for pinned memory too. > > + * > > + * This warning shouldn't be seen in real production scenario. > > + */ > > +void dma_buf_unsupported_invalidate_mappings(struct dma_buf_attachment > > *attach) > > +{ > > + pr_warn("Invalidate callback should not be called when memory is > > pinned\n"); > > +} > > +EXPORT_SYMBOL_FOR_MODULES(dma_buf_unsupported_invalidate_mappings, > > "ib_uverbs"); > > + > > Well that is exactly the opposite of what I had in mind. > > The RDMA non-ODP case should explicitly not provide an invalidate_mappings > callback, but only the dma_buf_attach_ops with allow_peer2peer set to true. > > This is done to explicitly note that RDMA non-ODP can't do invalidation's.
We want to achieve two goals: 1. Provide a meaningful warning to developers, rather than failing later because dma_buf_move_notify() was called on this problematic imported dma-buf. 2. Require all users to supply a valid .invalidate_mapping(). If I allow empty .invalidate_mapping(), this check will go too: 932 struct dma_buf_attachment * 933 dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct device *dev, 934 const struct dma_buf_attach_ops *importer_ops, 935 void *importer_priv) ... 943 if (WARN_ON(importer_ops && !importer_ops->invalidate_mappings)) 944 return ERR_PTR(-EINVAL); And it is important part of dma-buf. Thanks
