On Wed, Mar 24, 2021 at 03:37:02PM +0300, Dmitry Osipenko wrote:
> 24.03.2021 08:44, Minchan Kim пишет:
> > On Tue, Mar 23, 2021 at 09:47:27PM -0700, John Hubbard wrote:
> >> On 3/23/21 8:27 PM, Minchan Kim wrote:
> >> ...
> >>>>> +static int __init cma_sysfs_init(void)
> >>>>> +{
> >>>>> + unsigned int i;
> >>>>> +
> >>>>> + cma_kobj_root = kobject_create_and_add("cma", mm_kobj);
> >>>>> + if (!cma_kobj_root)
> >>>>> + return -ENOMEM;
> >>>>> +
> >>>>> + for (i = 0; i < cma_area_count; i++) {
> >>>>> + int err;
> >>>>> + struct cma *cma;
> >>>>> + struct cma_kobject *cma_kobj;
> >>>>> +
> >>>>> + cma_kobj = kzalloc(sizeof(*cma_kobj), GFP_KERNEL);
> >>>>> + if (!cma_kobj) {
> >>>>> + kobject_put(cma_kobj_root);
> >>>>> + return -ENOMEM;
> >>>>
> >>>> This leaks little cma_kobj's all over the floor. :)
> >>>
> >>> I thought kobject_put(cma_kobj_root) should deal with it. No?
> >>>
> >> If this fails when i > 0, there will be cma_kobj instances that
> >> were stashed in the cma_areas[] array. But this code only deletes
> >> the most recently allocated cma_kobj, not anything allocated on
> >> previous iterations of the loop.
> >
> > Oh, I misunderstood that destroying of root kobject will release
> > children recursively. Seems not true. Go back to old version.
> >
> >
> > index 16c81c9cb9b7..418951a3f138 100644
> > --- a/mm/cma_sysfs.c
> > +++ b/mm/cma_sysfs.c
> > @@ -80,20 +80,19 @@ static struct kobj_type cma_ktype = {
> > static int __init cma_sysfs_init(void)
> > {
> > unsigned int i;
> > + int err;
> > + struct cma *cma;
> > + struct cma_kobject *cma_kobj;
> >
> > cma_kobj_root = kobject_create_and_add("cma", mm_kobj);
> > if (!cma_kobj_root)
> > return -ENOMEM;
> >
> > for (i = 0; i < cma_area_count; i++) {
> > - int err;
> > - struct cma *cma;
> > - struct cma_kobject *cma_kobj;
> > -
> > cma_kobj = kzalloc(sizeof(*cma_kobj), GFP_KERNEL);
> > if (!cma_kobj) {
> > - kobject_put(cma_kobj_root);
> > - return -ENOMEM;
> > + err = -ENOMEM;
> > + goto out;
> > }
> >
> > cma = &cma_areas[i];
> > @@ -103,11 +102,21 @@ static int __init cma_sysfs_init(void)
> > cma_kobj_root, "%s", cma->name);
> > if (err) {
> > kobject_put(&cma_kobj->kobj);
> > - kobject_put(cma_kobj_root);
> > - return err;
> > + goto out;
> > }
> > }
> >
> > return 0;
> > +out:
> > + while (--i >= 0) {
> > + cma = &cma_areas[i];
> > +
> > + kobject_put(&cma->kobj->kobj);
> > + kfree(cma->kobj);
> > + cma->kobj = NULL;
> > + }
> > + kobject_put(cma_kobj_root);
> > +
> > + return err;
> > }
> > subsys_initcall(cma_sysfs_init);
>
> Since we don't care about the order in which kobjects are put, I'd write it in this way, which I think looks cleaner:
>
Hmm, preference matter. That kinds of goto error handling for unwinding is
familiar in kernel code and simple enough for me. I don't think readbility
is bad enough to need another cleanup function at this moment.
> static void cma_sysfs_cleanup(struct kobject *cma_kobj_root)
> {
> struct cma *cma = cma_areas;
> unsigned int i;
>
> for (i = 0; i < cma_area_count; i++, cma++) {
> if (!cma->kobj)
> break;
>
> kobject_put(&cma->kobj->kobj);
> }
>
> kobject_put(cma_kobj_root);
> }
>
> static int __init cma_sysfs_init(void)
> {
> struct kobject *cma_kobj_root;
> unsigned int i;
>
> cma_kobj_root = kobject_create_and_add("cma", mm_kobj);
> if (!cma_kobj_root)
> return -ENOMEM;
>
> for (i = 0; i < cma_area_count; i++) {
> struct cma_kobject *cma_kobj;
> struct cma *cma;
> int err;
>
> cma_kobj = kzalloc(sizeof(*cma_kobj), GFP_KERNEL);
> if (!cma_kobj) {
> cma_sysfs_cleanup(cma_kobj_root);
> return -ENOMEM;
> }
>
> cma = &cma_areas[i];
> cma->kobj = cma_kobj;
> cma_kobj->cma = cma;
> err = kobject_init_and_add(&cma_kobj->kobj, &cma_ktype,
> cma_kobj_root, "%s", cma->name);
> if (err) {
> cma_sysfs_cleanup(cma_kobj_root);
> return err;
> }
> }
>
> return 0;
> }
> subsys_initcall(cma_sysfs_init);
