On Fri, Aug 21, 2020 at 2:21 PM Roman Gushchin <guro@xxxxxx> wrote: > > Currently the remote memcg charging API consists of two functions: > memalloc_use_memcg() and memalloc_unuse_memcg(), which set and clear > the memcg value, which overwrites the memcg of the current task. > > memalloc_use_memcg(target_memcg); > <...> > memalloc_unuse_memcg(); > > It works perfectly for allocations performed from a normal context, > however an attempt to call it from an interrupt context or just nest > two remote charging blocks will lead to an incorrect accounting. > On exit from the inner block the active memcg will be cleared > instead of being restored. > > memalloc_use_memcg(target_memcg); > > memalloc_use_memcg(target_memcg_2); > <...> > memalloc_unuse_memcg(); > > Error: allocation here are charged to the memcg of the current > process instead of target_memcg. > > memalloc_unuse_memcg(); > > This patch extends the remote charging API by switching to a single > function: struct mem_cgroup *set_active_memcg(struct mem_cgroup *memcg), > which sets the new value and returns the old one. So a remote charging > block will look like: > > old_memcg = set_active_memcg(target_memcg); > <...> > set_active_memcg(old_memcg); > > This patch is heavily based on the patch by Johannes Weiner, > which can be found here: https://lkml.org/lkml/2020/5/28/806 . > > Signed-off-by: Roman Gushchin <guro@xxxxxx> > Cc: Johannes Weiner <hannes@xxxxxxxxxxx> > Cc: Shakeel Butt <shakeelb@xxxxxxxxxx> > Cc: Dan Schatzberg <dschatzberg@xxxxxx> Reviewed-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
