On Tue, 19 Dec 2006, Nick Piggin wrote:
>
> We never want to drop dirty data! (ignoring the truncate case, which is
> handled privately by truncate anyway)
Bzzt.
SURE we do.
We absolutely do want to drop dirty data in the writeout path.
How do you think dirty data ever _becomes_ clean data?
In other words, yes, we _do_ want to test-and-clear all the pgtable bits
_and_ the PG_dirty bit. We want to do it for:
- writeout
- truncate
- possibly a "drop" event (which could be a case for a journal entry that
becomes stale due to being replaced or something - kind of "truncate"
on metadata)
because both of those events _literally_ turn dirty state into clean
state.
In no other circumstance do we ever want to clear a dirty bit, as far as I
can tell.
Linus
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