On Tue 26-06-18 12:07:57, Shakeel Butt wrote: > On Tue, Jun 26, 2018 at 11:55 AM Johannes Weiner <hannes@xxxxxxxxxxx> wrote: > > > > On Tue, Jun 26, 2018 at 11:00:53AM -0700, Shakeel Butt wrote: > > > On Mon, Jun 25, 2018 at 10:49 PM Amir Goldstein <amir73il@xxxxxxxxx> wrote: > > > > > > > ... > > > > > > > > The verb 'unuse' takes an argument memcg and 'uses' it - too weird. > > > > You can use 'override'/'revert' verbs like override_creds or just call > > > > memalloc_use_memcg(old_memcg) since there is no reference taken > > > > anyway in use_memcg and no reference released in unuse_memcg. > > > > > > > > Otherwise looks good to me. > > > > > > > > > > Thanks for your feedback. Just using memalloc_use_memcg(old_memcg) and > > > ignoring the return seems more simple. I will wait for feedback from > > > other before changing anything. > > > > We're not nesting calls to memalloc_use_memcg(), right? So we don't > > have to return old_memcg and don't have to pass anything to unuse, it > > can always set current->active_memcg to NULL. > > For buffer_head, the allocation is done with GFP_NOFS. So, I think > there is no chance of nesting. The fsnotify uses GFP_KERNEL but based > on my limited understanding of fsnotify, there should not be any > nesting i.e. the allocation triggering reclaim which trigger fsnotify > events. Though I would like Amir or Jan to confirm there is no nesting > possible. You are correct. Fsnotify events are generated only as a result of some syscall, not due to reclaim or stuff like that. Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
