[PATCH 1/4] mm: migrate: move migration validation into numa_migrate_prep()

[Baolin Wang <baolin.wang@linux.alibaba.com>]

Now there are 3 places will validate if a page can mirate or not, and
some validations are performed later, which will waste some CPU to call
numa_migrate_prep().

Thus we can move all the migration validation into numa_migrate_prep(),
which is more maintainable as well as saving some CPU resources. Another
benefit is that it can serve as a preparation for supporting batch migration
in do_numa_page() in future.

Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
---
 mm/memory.c  | 19 +++++++++++++++++++
 mm/migrate.c | 19 -------------------
 2 files changed, 19 insertions(+), 19 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index d003076b218d..bee9b1e86ef0 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4747,6 +4747,25 @@ int numa_migrate_prep(struct page *page, struct vm_area_struct *vma,
 		*flags |= TNF_FAULT_LOCAL;
 	}
 
+	/*
+	 * 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_lru(page) &&
+	    (vma->vm_flags & VM_EXEC))
+		return NUMA_NO_NODE;
+
+	/*
+	 * 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_lru(page) && PageDirty(page))
+		return NUMA_NO_NODE;
+
+	/* Do not migrate THP mapped by multiple processes */
+	if (PageTransHuge(page) && total_mapcount(page) > 1)
+		return NUMA_NO_NODE;
+
 	return mpol_misplaced(page, vma, addr);
 }
 
diff --git a/mm/migrate.c b/mm/migrate.c
index e21d5a7e7447..9cc98fb1d6ec 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2485,10 +2485,6 @@ static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page)
 
 	VM_BUG_ON_PAGE(order && !PageTransHuge(page), page);
 
-	/* Do not migrate THP mapped by multiple processes */
-	if (PageTransHuge(page) && total_mapcount(page) > 1)
-		return 0;
-
 	/* Avoid migrating to a node that is nearly full */
 	if (!migrate_balanced_pgdat(pgdat, nr_pages)) {
 		int z;
@@ -2533,21 +2529,6 @@ int migrate_misplaced_page(struct page *page, struct vm_area_struct *vma,
 	LIST_HEAD(migratepages);
 	int nr_pages = thp_nr_pages(page);
 
-	/*
-	 * 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_lru(page) &&
-	    (vma->vm_flags & VM_EXEC))
-		goto out;
-
-	/*
-	 * 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_lru(page) && PageDirty(page))
-		goto out;
-
 	isolated = numamigrate_isolate_page(pgdat, page);
 	if (!isolated)
 		goto out;
-- 
2.39.3