[PATCH RFC v2 1/2] mm: memcontrol: make shrink_all_memory() memcg aware

[Andrea Righi <andrea.righi@canonical.com>]

Allow to specify a memcg when calling shrink_all_memory() to reclaim
some memory from a specific cgroup.

Moreover, make shrink_all_memory() always available and do not depend on
having CONFIG_HIBERNATION enabled.

This is required by the opportunistic memory reclaim feature.

Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
---
 include/linux/swap.h | 9 ++++++++-
 mm/vmscan.c          | 6 +++---
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/include/linux/swap.h b/include/linux/swap.h
index 661046994db4..1490b09a6e6c 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -368,7 +368,14 @@ extern unsigned long mem_cgroup_shrink_node(struct mem_cgroup *mem,
 						gfp_t gfp_mask, bool noswap,
 						pg_data_t *pgdat,
 						unsigned long *nr_scanned);
-extern unsigned long shrink_all_memory(unsigned long nr_pages);
+extern unsigned long
+__shrink_all_memory(unsigned long nr_pages, struct mem_cgroup *memcg);
+
+static inline unsigned long shrink_all_memory(unsigned long nr_pages)
+{
+	return __shrink_all_memory(nr_pages, NULL);
+}
+
 extern int vm_swappiness;
 extern int remove_mapping(struct address_space *mapping, struct page *page);
 
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 466fc3144fff..ac04d5e16c42 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -3986,7 +3986,6 @@ void wakeup_kswapd(struct zone *zone, gfp_t gfp_flags, int order,
 	wake_up_interruptible(&pgdat->kswapd_wait);
 }
 
-#ifdef CONFIG_HIBERNATION
 /*
  * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
  * freed pages.
@@ -3995,7 +3994,8 @@ void wakeup_kswapd(struct zone *zone, gfp_t gfp_flags, int order,
  * LRU order by reclaiming preferentially
  * inactive > active > active referenced > active mapped
  */
-unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
+unsigned long
+__shrink_all_memory(unsigned long nr_to_reclaim, struct mem_cgroup *memcg)
 {
 	struct scan_control sc = {
 		.nr_to_reclaim = nr_to_reclaim,
@@ -4006,6 +4006,7 @@ unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
 		.may_unmap = 1,
 		.may_swap = 1,
 		.hibernation_mode = 1,
+		.target_mem_cgroup = memcg,
 	};
 	struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
 	unsigned long nr_reclaimed;
@@ -4023,7 +4024,6 @@ unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
 
 	return nr_reclaimed;
 }
-#endif /* CONFIG_HIBERNATION */
 
 /*
  * This kswapd start function will be called by init and node-hot-add.
-- 
2.27.0