Messages in this thread | | | Date | Mon, 25 Jun 2007 08:25:21 -0400 | From | Chris Mason <> | Subject | Re: [RFC] fsblock |
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On Mon, Jun 25, 2007 at 04:58:48PM +1000, Nick Piggin wrote: > > >Using buffer heads instead allows the FS to send file data down inside > >the transaction code, without taking the page lock. So, locking wrt > >data=ordered is definitely going to be tricky. > > > >The best long term option may be making the locking order > >transaction -> page lock, and change writepage to punt to some other > >queue when it needs to start a transaction. > > Yeah, that's what I would like, and I think it would come naturally > if we move away from these "pass down a single, locked page APIs" > in the VM, and let the filesystem do the locking and potentially > batching of larger ranges.
Definitely.
> > write_begin/write_end is a step in that direction (and it helps > OCFS and GFS quite a bit). I think there is also not much reason > for writepage sites to require the page to lock the page and clear > the dirty bit themselves (which has seems ugly to me).
If we keep the page mapping information with the page all the time (ie writepage doesn't have to call get_block ever), it may be possible to avoid sending down a locked page. But, I don't know the delayed allocation internals well enough to say for sure if that is true.
Either way, writepage is the easiest of the bunch because it can be deferred.
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