dm-crypt: support relaxed memory alignment #413
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Many storage devices can handle DMA for data that is not aligned to the sector block size. The block and filesystem layers have introduced updates to allow that kind of memory alignment flexibility when possible. dm-crypt, however, currently constrains itself to aligned memory because it sends a single scatterlist element for the in/out list to the encrypt and decrypt algorithms. This forces applications that have unaligned data to copy through a bounce buffer, increasing CPU and memory utilization. Use multiple scatterlist elements to relax the memory alignment requirement. To keep this simple, this more flexible constraint is enabled only for certain encryption and initialization vector types, specifically the ones that don't have additional use for the request base scatterlist elements beyond holding decrypted data. Signed-off-by: Keith Busch <kbusch@kernel.org>
In the unlikely case where the base bio uses a highly fragmented vector, the four inline scatterlist elements may not be enough, so allocate a temporary scatterlist when needed. Signed-off-by: Keith Busch <kbusch@kernel.org>
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Upstream branch: c2f2b01 |
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Pull request for series with
subject: dm-crypt: support relaxed memory alignment
version: 1
url: https://patchwork.kernel.org/project/linux-block/list/?series=1029436