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, 3 insertions, 3 deletions

diff --git a/mm/filemap.c b/mm/filemap.c
index 9af4af660ef1..f268cfffbc6e 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -842,7 +842,7 @@ static int __add_to_page_cache_locked(struct page *page,
 
 	if (!huge) {
 		error = mem_cgroup_try_charge(page, current->mm,
-					      gfp_mask, &memcg, false);
+					      gfp_mask, &memcg);
 		if (error)
 			return error;
 	}
@@ -878,14 +878,14 @@ unlock:
 		goto error;
 
 	if (!huge)
-		mem_cgroup_commit_charge(page, memcg, false, false);
+		mem_cgroup_commit_charge(page, memcg, false);
 	trace_mm_filemap_add_to_page_cache(page);
 	return 0;
 error:
 	page->mapping = NULL;
 	/* Leave page->index set: truncation relies upon it */
 	if (!huge)
-		mem_cgroup_cancel_charge(page, memcg, false);
+		mem_cgroup_cancel_charge(page, memcg);
 	put_page(page);
 	return xas_error(&xas);
 }