(added Nanyong Sun to CC)
Hi Dongliang,
On Thu, Jan 20, 2022 at 11:07 PM Pavel Skripkin <paskripkin@xxxxxxxxx> wrote:
>
> Hi Dongliang,
>
> On 1/20/22 16:44, Dongliang Mu wrote:
> > The preivous commit 8fd0c1b0647a ("nilfs2: fix memory leak in
> > nilfs_sysfs_delete_device_group") only handles the memory leak in the
> > nilfs_sysfs_delete_device_group. However, the similar memory leak still
> > occurs in the nilfs_sysfs_create_device_group.
> >
> > Fix it by adding kobject_del when
> > kobject_init_and_add succeeds, but one of the following calls fails.
> >
> > Fixes: 8fd0c1b0647a ("nilfs2: fix memory leak in nilfs_sysfs_delete_device_group")
>
> Why Fixes tag points to my commit? This issue was introduced before my patch
>
As Pavel pointed out, this patch is independent of his patch.
The following one ?
5f5dec07aca7 ("nilfs2: fix memory leak in nilfs_sysfs_create_device_group")
> > Signed-off-by: Dongliang Mu <dzm91@xxxxxxxxxxx>
> > ---
> > fs/nilfs2/sysfs.c | 5 ++++-
> > 1 file changed, 4 insertions(+), 1 deletion(-)
Can you describe what memory leak issue does this patch actually fix ?
It looks like kobject_put() can call __kobject_del() unless circular
references exist.
kobject_put() -> kref_put() -> kobject_release() ->
kobject_cleanup() -> __kobject_del()
As explained in Documentation/core-api/kobject.rst,
kobject_del() can be used to drop the reference to the parent object, if
circular references are constructed.
But, at least, the parent object is NULL in this case.
I really want to understand what the real problem is.
Thanks,
Ryusuke Konishi
> >
> > diff --git a/fs/nilfs2/sysfs.c b/fs/nilfs2/sysfs.c
> > index 379d22e28ed6..0b2db2b499d5 100644
> > --- a/fs/nilfs2/sysfs.c
> > +++ b/fs/nilfs2/sysfs.c
> > @@ -995,7 +995,7 @@ int nilfs_sysfs_create_device_group(struct super_block *sb)
> >
> > err = nilfs_sysfs_create_mounted_snapshots_group(nilfs);
> > if (err)
> > - goto cleanup_dev_kobject;
> > + goto delete_dev_kobject;
> >
> > err = nilfs_sysfs_create_checkpoints_group(nilfs);
> > if (err)
> > @@ -1027,6 +1027,9 @@ int nilfs_sysfs_create_device_group(struct super_block *sb)
> > delete_mounted_snapshots_group:
> > nilfs_sysfs_delete_mounted_snapshots_group(nilfs);
> >
> > +delete_dev_kobject:
> > + kobject_del(&nilfs->ns_dev_kobj);
> > +
> > cleanup_dev_kobject:
> > kobject_put(&nilfs->ns_dev_kobj);
> > kfree(nilfs->ns_dev_subgroups);
> With regards,
> Pavel Skripkin
