memcg: simplify page cache charging

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

Because of commit ef6a3c6311 ("mm: add replace_page_cache_page()
function") , 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() gets pages that are not on the LRU
with the exception of PageSwapCache pages.  For checking,
WARN_ON_ONCE(PageLRU(page)) is added.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Miklos Szeredi <mszeredi@suse.cz>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Ying Han <yinghan@google.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 9 insertions, 22 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 7bc30707d0c6..71bac4d720d7 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2790,6 +2790,7 @@ 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())
@@ -2799,31 +2800,17 @@ 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;
 }