Re: 2.6.19 file content corruption on ext3

[Linus Torvalds]

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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