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 > > > > >