Re: does btrfs-receive use/compare the checksums from the btrfs-send side?

[Christoph Anton Mitterer <calestyo@scientia.net>]

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On Mon, 2016-08-29 at 16:25 +0800, Qu Wenruo wrote:
> Send will generate checksum for each command.
What does "command" mean here? Or better said how much data is secured
with one CRC32?


> For send stream, it's CRC32 for the whole command.
And this is verified then on the receiving end?


Wouldn't it be useful (if this technically possibly) to use the
checksums directly from the sent blocks? That way one could also catch
any errors on the receiving side, that occurred after the checksum from
the receive was verified (e.g. memory errors).

And couldn't one do something similar locally, when btrfs copies
blocks?

At least something like this would seem to me like the most native way:
- One want's checksum protection
- One copies data
- One has already checksums for that data

=> thus that should be used, as it's the most canonical version of a
   checksum for that data... anything that is newly calculated could
   in the best case just be good, and in the worst add new errors
   (unnoticed),... e.g. when memory is broken and the new checksum is
   calculated over that.


Cheers,
Chris.

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