On 11/05/2015 01:33 AM, Dave Chinner wrote:
Des xfs rely on this model for correctness? If so, I'd say we've got a
problem
No, it doesn't. The XFS integrity model doesn't trust the IO layers
to tell the truth about IO ordering and completion or for it's
developers to fully understand how IO layer ordering works. :P
That's good, because the storage developers simplified the model so that
fs developers would be able to get and use it.
i.e. we wait for full completions of all dependent IO before issuing
flushes or log writes that use REQ_FLUSH|REQ_FUA semantics to ensure
the dependent IOs are fully caught by the cache flushes...
... which is what you are supposed to do, that's how it works.
--
Jens Axboe
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