Directed kmem charging

The Linux kernel's memory cgroup allows limiting the memory usage of the jobs running on the system to provide isolation between the jobs. All the kernel memory allocated in the context of the job and marked with __GFP_ACCOUNT will also be included in the memory usage and be limited by the job's limit.

The kernel memory can only be charged to the memcg of the process in whose context kernel memory was allocated. However there are cases where the allocated kernel memory should be charged to the memcg different from the current processes's memcg. This patch series contains two such concrete use-cases i.e. fsnotify and buffer_head.

The fsnotify event objects can consume a lot of system memory for large or unlimited queues if there is either no or slow listener. The events are allocated in the context of the event producer. However they should be charged to the event consumer. Similarly the buffer_head objects can be allocated in a memcg different from the memcg of the page for which buffer_head objects are being allocated.

To solve this issue, this patch series introduces mechanism to charge kernel memory to a given memcg. In case of fsnotify events, the memcg of the consumer can be used for charging and for buffer_head, the memcg of the page can be charged. For directed charging, the caller can use the scope API memalloc_[un]use_memcg() to specify the memcg to charge for all the __GFP_ACCOUNT allocations within the scope.

Shakeel Butt (2):
fs: fsnotify: account fsnotify metadata to kmemcg fs, mm: account buffer_head to kmemcg

 fs/buffer.c                          | 15 ++++++-
 fs/notify/dnotify/dnotify.c          |  5 ++-
 fs/notify/fanotify/fanotify.c        | 17 ++++++--
 fs/notify/fanotify/fanotify_user.c   |  5 ++-
 fs/notify/group.c                    |  4 ++
 fs/notify/inotify/inotify_fsnotify.c | 15 ++++++-
 fs/notify/inotify/inotify_user.c     |  5 ++-
 include/linux/fsnotify_backend.h     | 12 ++++--
 include/linux/memcontrol.h           | 14 +++++++
 include/linux/sched.h                |  3 ++
 include/linux/sched/mm.h             | 41 +++++++++++++++++++
 kernel/fork.c                        |  3 ++
 mm/memcontrol.c                      | 60 ++++++++++++++++++++++++++--
 13 files changed, 182 insertions(+), 17 deletions(-)

2.18.0.rc2.346.g013aa6912e-goog