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The zerocopy path ultimately calls iov_iter_get_pages, which defines the step function for ITER_KVECs as simply, return -EFAULT. Taking the non-zerocopy path for ITER_KVECs avoids the unnecessary fallback. See https://lore.kernel.org/lkml/20150401023311.GL29656@ZenIV.linux.org.uk/T/#u for a discussion of why zerocopy for vmalloc data is not a good idea. Discovered while testing NBD traffic encrypted with ktls. Fixes: c46234ebb4d1 ("tls: RX path for ktls") Signed-off-by: Doron Roberts-Kedes <doronrk@fb.com> Signed-off-by: David S. Miller <davem@davemloft.net>