On Tue, Sep 23, 2025 at 02:09:36PM -0300, Jason Gunthorpe wrote:

On Sat, Sep 20, 2025 at 06:47:27PM -0600, Keith Busch wrote:

quoted

One other thing to note, this was runing on arm64 platform using smmu
configured with 64k pages. If your iommu granule is 4k instead, we
wouldn't use the blk_dma_map_direct path.

I spent some time looking to see if I could guess what this is and
came up empty. It seems most likely we are leaking a dma mapping
tracking somehow? The DMA API side is pretty simple here though..

Yeah, nothing stood out to me here either.
 

Not sure the 64k/4k itself is a cause, but triggering the non-iova
flow is probably the issue.

Can you check the output of this debugfs:

I don't have a system in this state at the moment, so we checked
previous logs on machines running older kernels. It's extermely
uncommon, but this error was happening prior to this series, so I don't
think this introduced any new problem here. I'll keeping looking, but I
don't think we'll make much progress if I can't find a more reliable
reproducer.

Thanks!