On Sat, 3 Dec 2022, Ira Weiny wrote:
> On Sat, Dec 03, 2022 at 09:58:58AM +0000, Yongqiang Liu wrote:
> > We should always call dax_region_put() whenever devm_create_dev_dax()
> > succeed or fail to avoid refcount leak of dax_region. Move the return
> > value check after dax_region_put().
> I think dax_region_put is called from dax_region_unregister() automatically on
> tear down.
Hi Ira,
Note the reference dax_region_unregister() will be putting is the one
devm_create_dev_dax() takes by kref_get(&dax_region->kref). I think
dax_hmem_probe() needs to put its reference in the error case, as in the
successful case.
Consider, devm_create_dev_dax() has error paths that return without
involving dax_region_unregister(), prior to kref_get() and device_add().
dax_hmem_probe() is clearly responsible for freeing the region in those
cases.
dax_hmem_probe() drops its own reference in the successful case because
(per the comment) "child dev_dax instances now own the lifetime of the
dax_region". That ownership is the reference that the error-case
dax_region_unregister() is dropping. dax_hmem_probe()'s initial reference
also needs to be dropped in the error case, as in the successful case.
> > Fixes: c01044cc8191 ("ACPI: HMAT: refactor hmat_register_target_device to
> > hmem_register_device")
>
> I'm also not sure how this patch is related to this fix.
>
> Ira
>
> > Signed-off-by: Yongqiang Liu <liuyongqian...@huawei.com>
> > ---
> > drivers/dax/hmem/hmem.c | 5 ++---
> > 1 file changed, 2 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/dax/hmem/hmem.c b/drivers/dax/hmem/hmem.c
> > index 1bf040dbc834..09f5cd7b6c8e 100644
> > --- a/drivers/dax/hmem/hmem.c
> > +++ b/drivers/dax/hmem/hmem.c
> > @@ -36,12 +36,11 @@ static int dax_hmem_probe(struct platform_device *pdev)
> > .size = region_idle ? 0 : resource_size(res),
> > };
> > dev_dax = devm_create_dev_dax(&data);
> > - if (IS_ERR(dev_dax))
> > - return PTR_ERR(dev_dax);
> >
> > /* child dev_dax instances now own the lifetime of the dax_region */
This comment should probably be updated now. :)
--
Paul Cassella
> > dax_region_put(dax_region);
> > - return 0;
> > +
> > + return IS_ERR(dev_dax) ? PTR_ERR(dev_dax) : 0;
> > }
> >
> > static int dax_hmem_remove(struct platform_device *pdev)
> > --
> > 2.25.1
> >
> >
>
