On 03 Apr 2013 20:36:00 +0100 J. Bruce Fields <bfields@xxxxxxxxxxxx> wrote:
> On Thu, Mar 21, 2013 at 05:41:35PM +0100, Bodo Stroesser wrote:
> > On 21 Mar 2013 00:34:00 +0100 NeilBrown <neilb@xxxxxxx> wrote:
> > > This applies only to SLES11-SP1 (2.6.32+) right?
> > > In mainline the request won't be dropped because the cache item isn't assumed
> > > to still be valid.
> >
> > I agree, there will be no drop in mainline.
> >
> > But in mainline there will be a useless upcall. That upcall might even be
> > processed by the reader, if cache_clean isn't faster then the reader.
> > The answer from the reader will again replace the current cache entry
> > (which is just a few microseconds old) by a new one. The new one must be
> > allocated, the replaced one must later be cleaned. The single item cache
> > is invalidated again.
> >
> > In worst case, the unnecessary replacement also could trigger the next
> > round of the game ...
> >
> > So in my opinion it would be better to add the patch you suggested below
> > to mainline also.
> >
> > >
> > > So we need to make sure that sunrpc_cache_pipe_upcall doesn't make an upcall
> > > on a cache item that has been replaced. I'd rather not use the CACHE_CLEAN
> > > bit (whether renamed or not) as it has a well defined meaning "has been
> > > removed from cache" and I'd rather not blur that meaning.
> > > We already have a state that means "this has been replace"- ->expiry_time is
> > > 0.
> > > So how about adding
> > > if (h->expiry_time == 0)
> > > return -EAGAIN;
> > > to sunrpc_cache_pipe_upcall() in SLES11-SP1.
> > >
> > > Does that work for you?
> >
> > Yes, that looks good. My test with this fix is running successfully
> > since 5 hours. I'll let it run until Monday.
>
> Apologies, I've completely lost track of this thread: do we know what
> mainline needs now?
>
> --b.
>
There is no reason for apologies. The thread meanwhile seems to be a bit
confusing :-)
Current state is:
- Neil Brown has created two series of patches. One for SLES11-SP1 and a
second one for -SP2
- AFAICS, the series for -SP2 will match with mainline also.
- Today I found and fixed the (hopefully) last problem in the -SP1 series.
My test using this patchset will run until Monday.
- Provided the test on SP1 succeeds, probably on Tuesday I'll start to test
the patches for SP2 (and mainline). If it runs fine, we'll have a tested
patchset not later than Mon 15th.
Bodo
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