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When the >> reservation is larger than the linked length, the tail >> [mapped_len, reserved size] is never returned to the allocator and >> is leaked, contrary to the documented contract. > > That's not what really happens in practice though - note that > free_iova() doesn't even take a size, only a pfn with which to look up > the corresponding rbtree entry. At worst, for sizes small enough for the > rcaches, a larger IOVA may be put in a cache for a smaller size, which > although wasteful, is otherwise pretty much benign. > > This isn't to say that the allocator behaviour might not eventually > change in future, but for now I can only assume that dma_iova_destroy() > doing this is intentional, because I pointed it out at least 3 times > over the course of the original review from RFC to eventual merge, and > Leon made a point of refusing to do anything about it :/ > Got it, I checked the code, the current code behavior does not cause a leak. Leon proposed a new modification, will send V2. And I believe is a cleanup rather than a fix. Regards, Honglei > Thanks, > Robin. > >> Free the whole reservation using dma_iova_size(), mirroring >> dma_iova_free(). The unmap step still operates on @mapped_len only, and >> the same iotlb_gather is reused so a single IOTLB flush is performed. >> >> Fixes: 433a76207dcf ("dma-mapping: Implement link/unlink ranges API") >> Cc: stable@vger.kernel.org >> Signed-off-by: Honglei Huang >> --- >>   drivers/iommu/dma-iommu.c | 5 ++++- >>   1 file changed, 4 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c >> index 9abaec0703e..bb29c82d1c8 100644 >> --- a/drivers/iommu/dma-iommu.c >> +++ b/drivers/iommu/dma-iommu.c >> @@ -2096,8 +2096,11 @@ static void __iommu_dma_iova_unlink(struct >> device *dev, >>       if (!iotlb_gather.queued) >>           iommu_iotlb_sync(domain, &iotlb_gather); >> -    if (free_iova) >> +    if (free_iova) { >> +        /* Free the whole reservation, not just the linked @size. */ >> +        size = iova_align(iovad, dma_iova_size(state) + iova_start_pad); >>           iommu_dma_free_iova(domain, addr, size, &iotlb_gather); >> +    } >>   } >>   /** >> >> base-commit: dc59e4fea9d83f03bad6bddf3fa2e52491777482 >