]> git.proxmox.com Git - mirror_ubuntu-kernels.git/commit
mm, memcg: rework remote charging API to support nesting
authorRoman Gushchin <guro@fb.com>
Sat, 17 Oct 2020 23:13:40 +0000 (16:13 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Sun, 18 Oct 2020 16:27:09 +0000 (09:27 -0700)
commitb87d8cefe43c7f22e8aa13919c1dfa2b4b4b4e01
tree711ab7c4fe9c8a79a6a5ba1d144c9d1c9adec5a3
parent7404840d87557c4092bf0272bce5e0354c774bf9
mm, memcg: rework remote charging API to support nesting

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@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Dan Schatzberg <dschatzberg@fb.com>
Link: https://lkml.kernel.org/r/20200821212056.3769116-1-guro@fb.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
fs/buffer.c
fs/notify/fanotify/fanotify.c
fs/notify/inotify/inotify_fsnotify.c
include/linux/sched/mm.h
mm/memcontrol.c