On Tue, Feb 17, 2009 at 01:05:34PM +0100, Peter Zijlstra wrote: > On Tue, 2009-02-17 at 12:55 +0100, Nick Piggin wrote: > > If nobody thinks it is insane, I'll resend to Andrew in a new thread. > > Right, gup_fast() seems to also respect .write properly, Phew! :) > so it would > also be used to balance that. > > I guess gup_fast() would need to use trylock_page(), and fall back to > the slow path when we start taking PG_locked on .write. Yeah, you're right there. It might also be possible to have a flag somewhere to avoid the lock if the underlying filesystem doesn't have a page_mkwrite or doesn't account dirty... which could avoid the overhead for the common case of anonymous or tmpfs memory. For gup_fast that pretty much implies an extra page flag I think. But let's not get too worried with details... I don't think put_user_pages hurts, even if it only remains as put_page loop. Just to help reader through the page refcounting. > I suppose we should start converting a few gup users over to pup before > handing the thing to Andrew, to have at least a few examples in-kernel. Could do. There are quite a few easy ones. -- To unsubscribe from this list: send the line "unsubscribe reiserfs-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
