On Fri, 2007-10-05 at 13:50 -0400, Trond Myklebust wrote: > On Fri, 2007-10-05 at 12:57 +0200, Peter Zijlstra wrote: > > In this patch I totally ignored unstable, but I'm not sure that's the > > proper thing to do, I'd need to figure out what happens to an unstable > > page when passed into pageout() - or if its passed to pageout at all. > > > > If unstable pages would be passed to pageout(), and it would properly > > convert them to writeback and clean them, then there is nothing wrong. > > Why would we want to do that? That would be a hell of a lot of work > (locking pages, setting flags, unlocking pages, ...) for absolutely no > reason. > > Unstable writes are writes which have been sent to the server, but which > haven't been written to disk on the server. A single RPC command is then > sent (COMMIT) which basically tells the server to call fsync(). After > that is successful, we can free up the pages, but we do that with no > extra manipulation of the pages themselves: no page locks, just removal > from the NFS private radix tree, and freeing up of the NFS private > structures. > > We only need to touch the pages again in the unlikely case that the > COMMIT fails because the server has rebooted. In this case we have to > resend the writes, and so the pages are marked as dirty, so we can go > through the whole writepages() rigmarole again... > > So, no. I don't see sending pages through pageout() as being at all > helpful.
Well, the thing is, we throttle pageout in throttle_vm_writeout(). As it stand we can deadlock there because it just waits for the numbers to drop, and unstable pages don't automagically dissapear. Only write_inodes() - normally called from balance_dirty_pages() will call COMMIT. So my thought was that calling pageout() on an unstable page would do the COMMIT - we're low on memory, otherwise we would not be paging, so getting rid of unstable pages seems to make sense to me. - 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/
