Return-Path: Received: from fieldses.org ([173.255.197.46]:54458 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751980AbdLVOZx (ORCPT ); Fri, 22 Dec 2017 09:25:53 -0500 Date: Fri, 22 Dec 2017 09:25:53 -0500 From: "J. Bruce Fields" To: "Reshetova, Elena" Cc: "linux-nfs@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "jlayton@kernel.org" , "trond.myklebust@primarydata.com" , "anna.schumaker@netapp.com" , "peterz@infradead.org" , "keescook@chromium.org" Subject: Re: [PATCH 1/4] lockd: convert nlm_host.h_count from atomic_t to refcount_t Message-ID: <20171222142553.GA9630@fieldses.org> References: <1511954146-11793-1-git-send-email-elena.reshetova@intel.com> <1511954146-11793-2-git-send-email-elena.reshetova@intel.com> <20171221202350.GE31467@fieldses.org> <2236FBA76BA1254E88B949DDB74E612B802CFB57@IRSMSX102.ger.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <2236FBA76BA1254E88B949DDB74E612B802CFB57@IRSMSX102.ger.corp.intel.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Fri, Dec 22, 2017 at 09:29:15AM +0000, Reshetova, Elena wrote: > > On Wed, Nov 29, 2017 at 01:15:43PM +0200, Elena Reshetova wrote: > > atomic_t variables are currently used to implement reference > > counters with the following properties: > > - counter is initialized to 1 using atomic_set() > > - a resource is freed upon counter reaching zero > > - once counter reaches zero, its further > > increments aren't allowed > > - counter schema uses basic atomic operations > > (set, inc, inc_not_zero, dec_and_test, etc.) > > >Whoops, I forgot that this doesn't apply to h_count. > > >Well, it's confusing, because h_count is actually used in two different > >ways: depending on whether a nlm_host represents a client or server, it > >may have the above properties or not. > > > So, what happens when it is not having the above properties? Is the object > being reused or? The object isn't destroyed when the counter hits zero--zero is just taken as a hint to some garbage collection algorithm that it would be OK to destroy it. So decrementing to or incrementing from zero is OK. --b.