[PATCH 1/4] memcg: simplify page cache charging.

[KAMEZAWA Hiroyuki]

From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>

This patch is a clean up. No functional/logical changes.

Because of commit ef6a3c6311, FUSE uses replace_page_cache() instead
of add_to_page_cache(). Then, mem_cgroup_cache_charge() is not
called against FUSE's pages from splice.

So, Now, mem_cgroup_cache_charge() doesn't receive a page on LRU
unless it's not SwapCache.
For checking, WARN_ON_ONCE(PageLRU(page)) is added.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
---
 mm/memcontrol.c |   31 +++++++++----------------------
 1 files changed, 9 insertions(+), 22 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index a9e92a6..947c62c 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2710,6 +2710,7 @@ int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,
 				gfp_t gfp_mask)
 {
 	struct mem_cgroup *memcg = NULL;
+	enum charge_type type = MEM_CGROUP_CHARGE_TYPE_CACHE;
 	int ret;
 
 	if (mem_cgroup_disabled())
@@ -2719,31 +2720,17 @@ int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,
 
 	if (unlikely(!mm))
 		mm = &init_mm;
+	if (!page_is_file_cache(page))
+		type = MEM_CGROUP_CHARGE_TYPE_SHMEM;
 
-	if (page_is_file_cache(page)) {
-		ret = __mem_cgroup_try_charge(mm, gfp_mask, 1, &memcg, true);
-		if (ret || !memcg)
-			return ret;
-
-		/*
-		 * FUSE reuses pages without going through the final
-		 * put that would remove them from the LRU list, make
-		 * sure that they get relinked properly.
-		 */
-		__mem_cgroup_commit_charge_lrucare(page, memcg,
-					MEM_CGROUP_CHARGE_TYPE_CACHE);
-		return ret;
-	}
-	/* shmem */
-	if (PageSwapCache(page)) {
+	if (!PageSwapCache(page)) {
+		ret = mem_cgroup_charge_common(page, mm, gfp_mask, type);
+		WARN_ON_ONCE(PageLRU(page));
+	} else { /* page is swapcache/shmem */
 		ret = mem_cgroup_try_charge_swapin(mm, page, gfp_mask, &memcg);
 		if (!ret)
-			__mem_cgroup_commit_charge_swapin(page, memcg,
-					MEM_CGROUP_CHARGE_TYPE_SHMEM);
-	} else
-		ret = mem_cgroup_charge_common(page, mm, gfp_mask,
-					MEM_CGROUP_CHARGE_TYPE_SHMEM);
-
+			__mem_cgroup_commit_charge_swapin(page, memcg, type);
+	}
 	return ret;
 }
 
-- 
1.7.4.1


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