On Mon, 18 Dec 2006, Linus Torvalds wrote: > 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.
i admit this may not be entirely relevant, but it seems like a good place to bring up an old problem: when a disk dies with lots of queued writes it can totally bring a system to its knees... even after the disk is removed. i wrote up something about this a while ago: http://lkml.org/lkml/2005/8/18/243 so there's another reason to "clear a dirty bit"... well, in fact -- drop the pages entirely. -dean - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
