Re: [PATCH v2 4/7] fsnotify: skip unattached marks

[Miklos Szeredi]

On Mon, Oct 30, 2017 at 3:00 PM, Jan Kara <jack@xxxxxxx> wrote:
> On Wed 25-10-17 10:41:36, Miklos Szeredi wrote:
>> After having gone through a ref-unref for the mark, dereferencing the group
>> (e.g. in fsnotify_compare_groups()) is wrong since the group may be
>> completely gone by that time.  So before continuing to traverse the mark
>> list, check if the mark is still attached.
>
> Are you sure this can happen? The thing is: Group reference from mark is
> dropped only in fsnotify_final_mark_destroy(). That gets called after SRCU
> period is finished from fsnotify_mark_destroy_workfn(). And SRCU period in
> which we have dropped our mark reference in fsnotify_finish_user_wait() has
> not yet ended. What am I missing?

Ah, missed that fact that mark holds a ref on the group until it's destroyed.

Yes, the patch is unnecessary in this case.

Thanks,
Miklos