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An Anonymous Coward writes:

Deep in the mailing list for the device-mapper project is this email exchange [redhat.com], after a patch to bring a request-based dm-crypt implementation was shot down by maintainers, among them Christoph Hellwig: "NAK for more request based stacking or DM drivers. They are a major pain to deal with... No, you will NOT remove the bio based path. That would break all kinds of perfectly valid setups."

The argument in favor of request-based dm-crypt was to utilize hardware encryption engines, but this was deemed too flimsy an argument to risk ruining the rest of the users of device-mapper. But then, Mark Brown reveals that Qualcomm had already implemented an "out-of-tree implementation" [googlesource.com] of this in a Board Support Package: "Android now wants to encrypt phones and tablets by default, and have been seeing substantial performance hits as a result; we can try to get people to share performance data from productionish systems, but it might be difficult."

In response to that, notable block storage kernel developer Jens Axboe replied, "Well, shame on them for developing out-of-tree, looks like they are reaping all the benefits of that."

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