[RFC PATCH 3/9 v2] mm/memcontrol: Refactor page_counter charging in try_charge_memcg

[Joshua Hahn <joshua.hahnjy@gmail.com>]

In preparation for adding charging and uncharging of a new page_counter
toptier to try_charge_memcg, refactor the code so that it is easier to
roll back partial charges when any one of the three page_counters
fail to charge.

No functional changes intended.

Signed-off-by: Joshua Hahn <joshua.hahnjy@gmail.com>
---
 mm/memcontrol.c | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 7de23ecd7cef6..8f7bedb55dbb1 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2385,18 +2385,22 @@ static int try_charge_memcg(struct mem_cgroup *memcg, gfp_t gfp_mask,
 
 retry:
 	reclaim_options = MEMCG_RECLAIM_MAY_SWAP;
-	if (!do_memsw_account() ||
-	    page_counter_try_charge(&memcg->memsw, nr_pages, &counter)) {
-		if (page_counter_try_charge(&memcg->memory, nr_pages, &counter))
-			goto done_restock;
-		if (do_memsw_account())
-			page_counter_uncharge(&memcg->memsw, nr_pages);
-		mem_over_limit = mem_cgroup_from_counter(counter, memory);
-	} else {
+
+	if (do_memsw_account() &&
+	    !page_counter_try_charge(&memcg->memsw, nr_pages, &counter)) {
 		mem_over_limit = mem_cgroup_from_counter(counter, memsw);
 		reclaim_options &= ~MEMCG_RECLAIM_MAY_SWAP;
+		goto reclaim;
 	}
 
+	if (page_counter_try_charge(&memcg->memory, nr_pages, &counter))
+		goto done_restock;
+
+	if (do_memsw_account())
+		page_counter_uncharge(&memcg->memsw, nr_pages);
+	mem_over_limit = mem_cgroup_from_counter(counter, memory);
+
+reclaim:
 	/*
 	 * Prevent unbounded recursion when reclaim operations need to
 	 * allocate memory. This might exceed the limits temporarily,
-- 
2.52.0