mm: memcontrol: drop @compound parameter from memcg charging API

The memcg charging API carries a boolean @compound parameter that tells
whether the page we're dealing with is a hugepage.
mem_cgroup_commit_charge() has another boolean @lrucare that indicates
whether the page needs LRU locking or not while charging.  The majority of
callsites know those parameters at compile time, which results in a lot of
naked "false, false" argument lists.  This makes for cryptic code and is a
breeding ground for subtle mistakes.

Thankfully, the huge page state can be inferred from the page itself and
doesn't need to be passed along.  This is safe because charging completes
before the page is published and somebody may split it.

Simplify the callsites by removing @compound, and let memcg infer the
state by using hpage_nr_pages() unconditionally.  That function does
PageTransHuge() to identify huge pages, which also helpfully asserts that
nobody passes in tail pages by accident.

The following patches will introduce a new charging API, best not to carry
over unnecessary weight.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Alex Shi <alex.shi@linux.alibaba.com>
Reviewed-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Balbir Singh <bsingharora@gmail.com>
Link: http://lkml.kernel.org/r/20200508183105.225460-4-hannes@cmpxchg.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 8 insertions, 14 deletions

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index bfe9533bb67e..fc400002c7be 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -359,15 +359,12 @@ enum mem_cgroup_protection mem_cgroup_protected(struct mem_cgroup *root,
 						struct mem_cgroup *memcg);
 
 int mem_cgroup_try_charge(struct page *page, struct mm_struct *mm,
-			  gfp_t gfp_mask, struct mem_cgroup **memcgp,
-			  bool compound);
+			  gfp_t gfp_mask, struct mem_cgroup **memcgp);
 int mem_cgroup_try_charge_delay(struct page *page, struct mm_struct *mm,
-			  gfp_t gfp_mask, struct mem_cgroup **memcgp,
-			  bool compound);
+			  gfp_t gfp_mask, struct mem_cgroup **memcgp);
 void mem_cgroup_commit_charge(struct page *page, struct mem_cgroup *memcg,
-			      bool lrucare, bool compound);
-void mem_cgroup_cancel_charge(struct page *page, struct mem_cgroup *memcg,
-		bool compound);
+			      bool lrucare);
+void mem_cgroup_cancel_charge(struct page *page, struct mem_cgroup *memcg);
 void mem_cgroup_uncharge(struct page *page);
 void mem_cgroup_uncharge_list(struct list_head *page_list);
 
@@ -849,8 +846,7 @@ static inline enum mem_cgroup_protection mem_cgroup_protected(
 
 static inline int mem_cgroup_try_charge(struct page *page, struct mm_struct *mm,
 					gfp_t gfp_mask,
-					struct mem_cgroup **memcgp,
-					bool compound)
+					struct mem_cgroup **memcgp)
 {
 	*memcgp = NULL;
 	return 0;
@@ -859,8 +855,7 @@ static inline int mem_cgroup_try_charge(struct page *page, struct mm_struct *mm,
 static inline int mem_cgroup_try_charge_delay(struct page *page,
 					      struct mm_struct *mm,
 					      gfp_t gfp_mask,
-					      struct mem_cgroup **memcgp,
-					      bool compound)
+					      struct mem_cgroup **memcgp)
 {
 	*memcgp = NULL;
 	return 0;
@@ -868,13 +863,12 @@ static inline int mem_cgroup_try_charge_delay(struct page *page,
 
 static inline void mem_cgroup_commit_charge(struct page *page,
 					    struct mem_cgroup *memcg,
-					    bool lrucare, bool compound)
+					    bool lrucare)
 {
 }
 
 static inline void mem_cgroup_cancel_charge(struct page *page,
-					    struct mem_cgroup *memcg,
-					    bool compound)
+					    struct mem_cgroup *memcg)
 {
 }