The copy-on-writeback solution that took too much memory, and the wait-on-writeback solution that causes too much latency are two extreme solutions to this problem.
Wouldn't an intermediate solution such as copy-on-page-modify be better? That way, when a page that's under writeback needs to be modified, a copy is made, that copy is modified, and the modified page can be marked for writeback as well.
Another solution could be to copy only the checksum value instead of the whole page.
I'm probably missing something here, and I'd like to know what that is :)
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