From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752341AbbIQR6d (ORCPT ); Thu, 17 Sep 2015 13:58:33 -0400 Received: from bedivere.hansenpartnership.com ([66.63.167.143]:34655 "EHLO bedivere.hansenpartnership.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751777AbbIQR6b (ORCPT ); Thu, 17 Sep 2015 13:58:31 -0400 Message-ID: <1442512709.4073.24.camel@HansenPartnership.com> Subject: Re: DEFINE_IDA causing memory leaks? (was Re: [PATCH 1/2] virtio: fix memory leak of virtio ida cache layers) From: James Bottomley To: Tejun Heo Cc: "Michael S. Tsirkin" , Suman Anna , Ohad Ben-Cohen , linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-scsi@vger.kernel.org, open-iscsi@googlegroups.com Date: Thu, 17 Sep 2015 10:58:29 -0700 In-Reply-To: <20150917171529.GA15447@htj.duckdns.org> References: <1442449758-14594-1-git-send-email-s-anna@ti.com> <1442449758-14594-2-git-send-email-s-anna@ti.com> <20150917082425-mutt-send-email-mst@redhat.com> <1442499344.4073.0.camel@HansenPartnership.com> <20150917190538-mutt-send-email-mst@redhat.com> <1442508517.4073.13.camel@HansenPartnership.com> <20150917171529.GA15447@htj.duckdns.org> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.12.11 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2015-09-17 at 13:15 -0400, Tejun Heo wrote: > Hello, > > On Thu, Sep 17, 2015 at 09:48:37AM -0700, James Bottomley wrote: > > Well, there's an easy fix for that. We could have ida_remove() actually > > free the bitmap and not cache it if it's the last layer. That way ida > > would naturally empty and we wouldn't need a destructor. Tejun, would > > that work? > > Yeah, that definitely is one way to go about it. It kinda muddles the > purpose of ida_destroy() tho. I suppose we can rename it to > idr_remove_all() and then do the same to idr. I'm not particularly > objecting to all that but what's wrong with just calling idr_destroy() > on exit paths? If missing the call in modules is an issue, maybe we > can just annotate idr/ida with debugobj? The argument is that we shouldn't have to explicitly destroy a statically initialized object, so DEFINE_IDA(someida); Should just work without having to explicitly do ida_destory(someida); somewhere in the exit code. It's about usage patterns. Michael's argument is that if we can't follow the no destructor pattern for DEFINE_IDA() then we shouldn't have it at all, because it's confusing kernel design patterns. The pattern we would have would be struct ida someida: ida_init(&someida); ... ida_destroy(&someida); so the object explicitly has a constructor matched to a destructor. James