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Date:   Wed, 20 Dec 2017 13:24:29 +0300
From:   Andrey Ryabinin <aryabinin@...tuozzo.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        cgroups@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Andrey Ryabinin <aryabinin@...tuozzo.com>
Subject: [PATCH 2/2] mm/memcg: Consolidate mem_cgroup_resize_[memsw]_limit() functions.

mem_cgroup_resize_limit() and mem_cgroup_resize_memsw_limit() are almost
identical functions. Instead of having two of them, we could pass an
additional argument to mem_cgroup_resize_limit() and by using it,
consolidate all the code in a single function.

Signed-off-by: Andrey Ryabinin <aryabinin@...tuozzo.com>
---
 mm/memcontrol.c | 77 +++++++++++++--------------------------------------------
 1 file changed, 17 insertions(+), 60 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 09ee052cf684..b263500626fe 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2459,9 +2459,17 @@ static inline int mem_cgroup_move_swap_account(swp_entry_t entry,
 
 static DEFINE_MUTEX(memcg_limit_mutex);
 
-static int mem_cgroup_resize_limit(struct mem_cgroup *memcg,
+static bool invalid_mem_limit(struct mem_cgroup *memcg, bool memsw,
+			      unsigned long limit)
+{
+	return (!memsw && limit > memcg->memsw.limit) ||
+		(memsw && limit < memcg->memory.limit);
+}
+
+static int mem_cgroup_resize_limit(struct mem_cgroup *memcg, bool memsw,
 				   unsigned long limit)
 {
+	struct page_counter *counter = memsw ? &memcg->memsw : &memcg->memory;
 	unsigned long curusage;
 	unsigned long oldusage;
 	bool enlarge = false;
@@ -2476,7 +2484,7 @@ static int mem_cgroup_resize_limit(struct mem_cgroup *memcg,
 	retry_count = MEM_CGROUP_RECLAIM_RETRIES *
 		      mem_cgroup_count_children(memcg);
 
-	curusage = oldusage = page_counter_read(&memcg->memory);
+	curusage = oldusage = page_counter_read(counter);
 
 	do {
 		if (signal_pending(current)) {
@@ -2485,75 +2493,24 @@ static int mem_cgroup_resize_limit(struct mem_cgroup *memcg,
 		}
 
 		mutex_lock(&memcg_limit_mutex);
-		if (limit > memcg->memsw.limit) {
+		if (invalid_mem_limit(memcg, memsw, limit)) {
 			mutex_unlock(&memcg_limit_mutex);
 			ret = -EINVAL;
 			break;
 		}
-		if (limit > memcg->memory.limit)
-			enlarge = true;
-		ret = page_counter_limit(&memcg->memory, limit);
-		mutex_unlock(&memcg_limit_mutex);
-
-		if (!ret)
-			break;
-
-		try_to_free_mem_cgroup_pages(memcg, curusage - limit,
-					GFP_KERNEL, true);
-
-		curusage = page_counter_read(&memcg->memory);
-		/* Usage is reduced ? */
-		if (curusage >= oldusage)
-			retry_count--;
-		else
-			oldusage = curusage;
-	} while (retry_count);
-
-	if (!ret && enlarge)
-		memcg_oom_recover(memcg);
-
-	return ret;
-}
 
-static int mem_cgroup_resize_memsw_limit(struct mem_cgroup *memcg,
-					 unsigned long limit)
-{
-	unsigned long curusage;
-	unsigned long oldusage;
-	bool enlarge = false;
-	int retry_count;
-	int ret;
-
-	/* see mem_cgroup_resize_res_limit */
-	retry_count = MEM_CGROUP_RECLAIM_RETRIES *
-		      mem_cgroup_count_children(memcg);
-
-	curusage = oldusage = page_counter_read(&memcg->memsw);
-
-	do {
-		if (signal_pending(current)) {
-			ret = -EINTR;
-			break;
-		}
-
-		mutex_lock(&memcg_limit_mutex);
-		if (limit < memcg->memory.limit) {
-			mutex_unlock(&memcg_limit_mutex);
-			ret = -EINVAL;
-			break;
-		}
-		if (limit > memcg->memsw.limit)
+		if (limit > counter->limit)
 			enlarge = true;
-		ret = page_counter_limit(&memcg->memsw, limit);
+		ret = page_counter_limit(counter, limit);
 		mutex_unlock(&memcg_limit_mutex);
 
 		if (!ret)
 			break;
 
 		try_to_free_mem_cgroup_pages(memcg, curusage - limit,
-					GFP_KERNEL, false);
+					GFP_KERNEL, !memsw);
 
-		curusage = page_counter_read(&memcg->memsw);
+		curusage = page_counter_read(counter);
 		/* Usage is reduced ? */
 		if (curusage >= oldusage)
 			retry_count--;
@@ -3233,10 +3190,10 @@ static ssize_t mem_cgroup_write(struct kernfs_open_file *of,
 		}
 		switch (MEMFILE_TYPE(of_cft(of)->private)) {
 		case _MEM:
-			ret = mem_cgroup_resize_limit(memcg, nr_pages);
+			ret = mem_cgroup_resize_limit(memcg, false, nr_pages);
 			break;
 		case _MEMSWAP:
-			ret = mem_cgroup_resize_memsw_limit(memcg, nr_pages);
+			ret = mem_cgroup_resize_limit(memcg, true, nr_pages);
 			break;
 		case _KMEM:
 			ret = memcg_update_kmem_limit(memcg, nr_pages);
-- 
2.13.6

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