mm: rename mem_cgroup_migrate to mem_cgroup_replace_page

After v4.3's commit 0610c25daa3e ("memcg: fix dirty page migration")
mem_cgroup_migrate() doesn't have much to offer in page migration: convert
migrate_misplaced_transhuge_page() to set_page_memcg() instead.

Then rename mem_cgroup_migrate() to mem_cgroup_replace_page(), since its
remaining callers are replace_page_cache_page() and shmem_replace_page():
both of whom passed lrucare true, so just eliminate that argument.

Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/memcontrol.h

@@ -297,8 +297,7 @@ void mem_cgroup_cancel_charge(struct page *page, struct mem_cgroup *memcg);
 void mem_cgroup_uncharge(struct page *page);
 void mem_cgroup_uncharge_list(struct list_head *page_list);
 
-void mem_cgroup_migrate(struct page *oldpage, struct page *newpage,
-			bool lrucare);
+void mem_cgroup_replace_page(struct page *oldpage, struct page *newpage);
 
 struct lruvec *mem_cgroup_zone_lruvec(struct zone *, struct mem_cgroup *);
 struct lruvec *mem_cgroup_page_lruvec(struct page *, struct zone *);
@@ -537,9 +536,7 @@ static inline void mem_cgroup_uncharge_list(struct list_head *page_list)
 {
 }
 
-static inline void mem_cgroup_migrate(struct page *oldpage,
-				      struct page *newpage,
-				      bool lrucare)
+static inline void mem_cgroup_replace_page(struct page *old, struct page *new)
 {
 }
 

mm/filemap.c

@@ -551,7 +551,7 @@ int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
 			__inc_zone_page_state(new, NR_SHMEM);
 		spin_unlock_irqrestore(&mapping->tree_lock, flags);
 		mem_cgroup_end_page_stat(memcg);
-		mem_cgroup_migrate(old, new, true);
+		mem_cgroup_replace_page(old, new);
 		radix_tree_preload_end();
 		if (freepage)
 			freepage(old);

mm/memcontrol.c

@@ -4531,9 +4531,8 @@ static int mem_cgroup_move_account(struct page *page,
 		goto out;
 
 	/*
-	 * Prevent mem_cgroup_migrate() from looking at page->mem_cgroup
-	 * of its source page while we change it: page migration takes
-	 * both pages off the LRU, but page cache replacement doesn't.
+	 * Prevent mem_cgroup_replace_page() from looking at
+	 * page->mem_cgroup of its source page while we change it.
 	 */
 	if (!trylock_page(page))
 		goto out;
@@ -5495,7 +5494,7 @@ void mem_cgroup_uncharge_list(struct list_head *page_list)
 }
 
 /**
- * mem_cgroup_migrate - migrate a charge to another page
+ * mem_cgroup_replace_page - migrate a charge to another page
  * @oldpage: currently charged page
  * @newpage: page to transfer the charge to
  * @lrucare: either or both pages might be on the LRU already
@@ -5504,16 +5503,13 @@ void mem_cgroup_uncharge_list(struct list_head *page_list)
  *
  * Both pages must be locked, @newpage->mapping must be set up.
  */
-void mem_cgroup_migrate(struct page *oldpage, struct page *newpage,
-			bool lrucare)
+void mem_cgroup_replace_page(struct page *oldpage, struct page *newpage)
 {
 	struct mem_cgroup *memcg;
 	int isolated;
 
 	VM_BUG_ON_PAGE(!PageLocked(oldpage), oldpage);
 	VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
-	VM_BUG_ON_PAGE(!lrucare && PageLRU(oldpage), oldpage);
-	VM_BUG_ON_PAGE(!lrucare && PageLRU(newpage), newpage);
 	VM_BUG_ON_PAGE(PageAnon(oldpage) != PageAnon(newpage), newpage);
 	VM_BUG_ON_PAGE(PageTransHuge(oldpage) != PageTransHuge(newpage),
 		       newpage);
@@ -5525,25 +5521,16 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage,
 	if (newpage->mem_cgroup)
 		return;
 
-	/*
-	 * Swapcache readahead pages can get migrated before being
-	 * charged, and migration from compaction can happen to an
-	 * uncharged page when the PFN walker finds a page that
-	 * reclaim just put back on the LRU but has not released yet.
-	 */
+	/* Swapcache readahead pages can get replaced before being charged */
 	memcg = oldpage->mem_cgroup;
 	if (!memcg)
 		return;
 
-	if (lrucare)
-		lock_page_lru(oldpage, &isolated);
-
+	lock_page_lru(oldpage, &isolated);
 	oldpage->mem_cgroup = NULL;
+	unlock_page_lru(oldpage, isolated);
 
-	if (lrucare)
-		unlock_page_lru(oldpage, isolated);
-
-	commit_charge(newpage, memcg, lrucare);
+	commit_charge(newpage, memcg, true);
 }
 
 /*

mm/migrate.c

@@ -30,7 +30,6 @@
 #include <linux/mempolicy.h>
 #include <linux/vmalloc.h>
 #include <linux/security.h>
-#include <linux/memcontrol.h>
 #include <linux/syscalls.h>
 #include <linux/hugetlb.h>
 #include <linux/hugetlb_cgroup.h>
@@ -1831,8 +1830,8 @@ fail_putback:
 	}
 
 	mlock_migrate_page(new_page, page);
-	mem_cgroup_migrate(page, new_page, false);
-
+	set_page_memcg(new_page, page_memcg(page));
+	set_page_memcg(page, NULL);
 	page_remove_rmap(page);
 
 	spin_unlock(ptl);

mm/shmem.c

@@ -1023,7 +1023,7 @@ static int shmem_replace_page(struct page **pagep, gfp_t gfp,
 		 */
 		oldpage = newpage;
 	} else {
-		mem_cgroup_migrate(oldpage, newpage, true);
+		mem_cgroup_replace_page(oldpage, newpage);
 		lru_cache_add_anon(newpage);
 		*pagep = newpage;
 	}