On Fri, Feb 07, 2020 at 02:25:27PM +0000, Trond Myklebust wrote: > On Thu, 2020-02-06 at 11:33 -0500, J. Bruce Fields wrote: > > On Tue, Jan 14, 2020 at 11:57:38AM -0500, Trond Myklebust wrote: > > > If the cache entry never gets initialised, we want the garbage > > > collector to be able to evict it. Otherwise if the upcall daemon > > > fails to initialise the entry, we end up never expiring it. > > > > Could you tell us more about what motivated this? > > > > It's causing failures on pynfs server-reboot tests. I haven't pinned > > down the cause yet, but it looks like it could be a regression to the > > behavior Kinglong Mee describes in detail in his original patch. > > > > Can you point me to the tests that are failing? I'm basically doing ./nfs4.1/testserver.py myserver:/path reboot --serverhelper=examples/server_helper.sh --serverhelperarg=myserver For all I know at this point, the change could be exposing a pynfs-side bug. > The motivation here is to allow the garbage collector to do its job of > evicting cache entries after they are supposed to have timed out. Understood. I was curious whether this was found by code inspection or because you'd run across a case where the leak was causing a practical problem. --b. > The fact that uninitialised cache entries are given an infinite > lifetime, and are never evicted is a de facto memory leak if, for > instance, the mountd daemon ignores the cache request, or the downcall > in expkey_parse() or svc_export_parse() fails without being able to > update the request. > > The threads that are waiting for the cache replies already have a > mechanism for dealing with timeouts (with cache_wait_req() and > deferred requests), so the question is what is so special about > uninitialised requests that we have to leak them in order to avoid a > problem with reboot?
