Messages in this thread | | | Subject | Re: DEFINE_IDA causing memory leaks? (was Re: [PATCH 1/2] virtio: fix memory leak of virtio ida cache layers) | From | James Bottomley <> | Date | Thu, 17 Sep 2015 07:15:44 -0700 |
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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" <mst@redhat.com> > > Signed-off-by: Suman Anna <s-anna@ti.com> > > 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@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >
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