mm: code cleanup for MADV_FREE

Some comments for MADV_FREE is revised and added to help people understand
the MADV_FREE code, especially the page flag, PG_swapbacked.  This makes
page_is_file_cache() isn't consistent with its comments.  So the function
is renamed to page_is_file_lru() to make them consistent again.  All these
are put in one patch as one logical change.

Suggested-by: David Hildenbrand <david@redhat.com>
Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
Suggested-by: David Rientjes <rientjes@google.com>
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: David Rientjes <rientjes@google.com>
Acked-by: Michal Hocko <mhocko@kernel.org>
Acked-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Rik van Riel <riel@surriel.com>
Link: http://lkml.kernel.org/r/20200317100342.2730705-1-ying.huang@intel.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 8 insertions, 8 deletions

diff --git a/mm/migrate.c b/mm/migrate.c
index 1a205503be3f..c1412e04975e 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -193,7 +193,7 @@ void putback_movable_pages(struct list_head *l)
 			put_page(page);
 		} else {
 			mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON +
-					page_is_file_cache(page), -hpage_nr_pages(page));
+					page_is_file_lru(page), -hpage_nr_pages(page));
 			putback_lru_page(page);
 		}
 	}
@@ -1219,7 +1219,7 @@ out:
 		 */
 		if (likely(!__PageMovable(page)))
 			mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON +
-					page_is_file_cache(page), -hpage_nr_pages(page));
+					page_is_file_lru(page), -hpage_nr_pages(page));
 	}
 
 	/*
@@ -1592,7 +1592,7 @@ static int add_page_for_migration(struct mm_struct *mm, unsigned long addr,
 		err = 1;
 		list_add_tail(&head->lru, pagelist);
 		mod_node_page_state(page_pgdat(head),
-			NR_ISOLATED_ANON + page_is_file_cache(head),
+			NR_ISOLATED_ANON + page_is_file_lru(head),
 			hpage_nr_pages(head));
 	}
 out_putpage:
@@ -1955,7 +1955,7 @@ static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page)
 		return 0;
 	}
 
-	page_lru = page_is_file_cache(page);
+	page_lru = page_is_file_lru(page);
 	mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON + page_lru,
 				hpage_nr_pages(page));
 
@@ -1991,7 +1991,7 @@ int migrate_misplaced_page(struct page *page, struct vm_area_struct *vma,
 	 * Don't migrate file pages that are mapped in multiple processes
 	 * with execute permissions as they are probably shared libraries.
 	 */
-	if (page_mapcount(page) != 1 && page_is_file_cache(page) &&
+	if (page_mapcount(page) != 1 && page_is_file_lru(page) &&
 	    (vma->vm_flags & VM_EXEC))
 		goto out;
 
@@ -1999,7 +1999,7 @@ int migrate_misplaced_page(struct page *page, struct vm_area_struct *vma,
 	 * Also do not migrate dirty pages as not all filesystems can move
 	 * dirty pages in MIGRATE_ASYNC mode which is a waste of cycles.
 	 */
-	if (page_is_file_cache(page) && PageDirty(page))
+	if (page_is_file_lru(page) && PageDirty(page))
 		goto out;
 
 	isolated = numamigrate_isolate_page(pgdat, page);
@@ -2014,7 +2014,7 @@ int migrate_misplaced_page(struct page *page, struct vm_area_struct *vma,
 		if (!list_empty(&migratepages)) {
 			list_del(&page->lru);
 			dec_node_page_state(page, NR_ISOLATED_ANON +
-					page_is_file_cache(page));
+					page_is_file_lru(page));
 			putback_lru_page(page);
 		}
 		isolated = 0;
@@ -2044,7 +2044,7 @@ int migrate_misplaced_transhuge_page(struct mm_struct *mm,
 	pg_data_t *pgdat = NODE_DATA(node);
 	int isolated = 0;
 	struct page *new_page = NULL;
-	int page_lru = page_is_file_cache(page);
+	int page_lru = page_is_file_lru(page);
 	unsigned long start = address & HPAGE_PMD_MASK;
 
 	new_page = alloc_pages_node(node,