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 leonro@nvidia.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 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 leonro@nvidia.com
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