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The error returns for various cases detected by get_prefetchable_mr() get confused as it flows back to userspace. Properly label each error path and flow the error code properly back to the system call. Link: https://lore.kernel.org/r/20210928170846.GA1721590@nvidia.com Suggested-by: Li Zhijian <lizhijian@cn.fujitsu.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>