From mboxrd@z Thu Jan 1 00:00:00 1970 From: James Bottomley Subject: Re: DEFINE_IDA causing memory leaks? (was Re: [PATCH 1/2] virtio: fix memory leak of virtio ida cache layers) Date: Thu, 17 Sep 2015 07:15:44 -0700 Message-ID: <1442499344.4073.0.camel@HansenPartnership.com> 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> Reply-To: open-iscsi-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Return-path: In-Reply-To: <20150917082425-mutt-send-email-mst-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> List-Post: , List-Help: , List-Archive: , List-Unsubscribe: , To: "Michael S. Tsirkin" Cc: Suman Anna , Ohad Ben-Cohen , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, virtualization-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, linux-scsi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, open-iscsi-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org, Tejun Heo List-Id: linux-scsi@vger.kernel.org On Thu, 2015-09-17 at 08:33 +0300, Michael S. Tsirkin wrote: > On Wed, Sep 16, 2015 at 07:29:17PM -0500, Suman Anna wrote: > > The virtio core uses a static ida named virtio_index_ida for > > assigning index numbers to virtio devices during registration. > > The ida core may allocate some internal idr cache layers and > > an ida bitmap upon any ida allocation, and all these layers are > > truely freed only upon the ida destruction. The virtio_index_ida > > is not destroyed at present, leading to a memory leak when using > > the virtio core as a module and atleast one virtio device is > > registered and unregistered. > > > > Fix this by invoking ida_destroy() in the virtio core module > > exit. > > > > Cc: "Michael S. Tsirkin" > > Signed-off-by: Suman Anna > > Interesting. > Will the same apply to e.g. sd_index_ida in drivers/scsi/sd.c > or iscsi_sess_ida in drivers/scsi/scsi_transport_iscsi.c? > > If no, why not? > > One doesn't generally expect to have to free global variables. > Maybe we should forbid DEFINE_IDA in modules? > > James, could you comment on this please? ida is Tejun's baby (cc'd). However, it does look like without ida_destroy() you will leave a cached ida->bitmap dangling because we're trying to be a bit clever in ida_remove() so we cache the bitmap to relieve ida_pre_get() of the burden if we would otherwise free it. I don't understand why you'd want to forbid DEFINE_IDA ... all it does is pre-initialise a usually static ida structure. The initialised structure will have a NULL bitmap cache that's allocated in the first ida_pre_get() ... that all seems to work as expected and no different from a dynamically allocated struct ida. Or are you thinking because ida_destory() doesn't set bitmap to NULL, it damages the reuse? In which case I'm not sure there's much benefit to making it reusable, but I suppose we could by adding a memset into ida_destroy(). James > > --- > > drivers/virtio/virtio.c | 1 + > > 1 file changed, 1 insertion(+) > > > > diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c > > index b1877d73fa56..7062bb0975a5 100644 > > --- a/drivers/virtio/virtio.c > > +++ b/drivers/virtio/virtio.c > > @@ -412,6 +412,7 @@ static int virtio_init(void) > > static void __exit virtio_exit(void) > > { > > bus_unregister(&virtio_bus); > > + ida_destroy(&virtio_index_ida); > > } > > core_initcall(virtio_init); > > module_exit(virtio_exit); > > -- > > 2.5.0 > -- > To unsubscribe from this list: send the line "unsubscribe linux-scsi" in > the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- You received this message because you are subscribed to the Google Groups "open-iscsi" group. To unsubscribe from this group and stop receiving emails from it, send an email to open-iscsi+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To post to this group, send email to open-iscsi-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org Visit this group at http://groups.google.com/group/open-iscsi. For more options, visit https://groups.google.com/d/optout.