The page_cgroup infrastructure, currently available only for the memory
cgroup controller, can be used to store the owner of each page and
opportunely track the writeback IO. This information is encoded in
the upper 16-bits of the page_cgroup->flags.

A owner can be identified using a generic ID number and the following
interfaces are provided to store a retrieve this information:

  unsigned long page_cgroup_get_owner(struct page *page);
  int page_cgroup_set_owner(struct page *page, unsigned long id);
  int page_cgroup_copy_owner(struct page *npage, struct page *opage);

The blkio.throttle controller can use the cgroup css_id() as the owner's
ID number.

Signed-off-by: Andrea Righi <redacted>
---
 block/Kconfig               |    2 +
 block/blk-cgroup.c          |    6 ++
 include/linux/memcontrol.h  |    6 ++
 include/linux/mmzone.h      |    4 +-
 include/linux/page_cgroup.h |   33 ++++++++++-
 init/Kconfig                |    4 +
 mm/Makefile                 |    3 +-
 mm/memcontrol.c             |    6 ++
 mm/page_cgroup.c            |  129 +++++++++++++++++++++++++++++++++++++++----
 9 files changed, 176 insertions(+), 17 deletions(-)

diff --git a/block/Kconfig b/block/Kconfig
index 60be1e0..1351ea8 100644
--- a/block/Kconfig
+++ b/block/Kconfig

@@ -80,6 +80,8 @@ config BLK_DEV_INTEGRITY
 config BLK_DEV_THROTTLING
 	bool "Block layer bio throttling support"
 	depends on BLK_CGROUP=y && EXPERIMENTAL
+	select MM_OWNER
+	select PAGE_TRACKING
 	default n
 	---help---
 	Block layer bio throttling support. It can be used to limit

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index f283ae1..5c57f0a 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c

@@ -107,6 +107,12 @@ blkio_policy_search_node(const struct blkio_cgroup *blkcg, dev_t dev,
 	return NULL;
 }
 
+bool blkio_cgroup_disabled(void)
+{
+	return blkio_subsys.disabled ? true : false;
+}
+EXPORT_SYMBOL_GPL(blkio_cgroup_disabled);
+