hugetlb: simplify migrate_huge_page()

Since we migrate only one hugepage, don't use linked list for passing the
page around.  Directly pass the page that need to be migrated as argument.
This also removes the usage of page->lru in the migrate path.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Hillf Danton <dhillf@gmail.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
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>

1 files changed, 21 insertions, 44 deletions

diff --git a/mm/migrate.c b/mm/migrate.c
index be26d5cbe56..fdce3a29fc4 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -932,15 +932,8 @@ static int unmap_and_move_huge_page(new_page_t get_new_page,
 	if (anon_vma)
 		put_anon_vma(anon_vma);
 	unlock_page(hpage);
-
 out:
-	if (rc != -EAGAIN) {
-		list_del(&hpage->lru);
-		put_page(hpage);
-	}
-
 	put_page(new_hpage);
-
 	if (result) {
 		if (rc)
 			*result = rc;
@@ -1016,48 +1009,32 @@ out:
 	return nr_failed + retry;
 }
 
-int migrate_huge_pages(struct list_head *from,
-		new_page_t get_new_page, unsigned long private, bool offlining,
-		enum migrate_mode mode)
+int migrate_huge_page(struct page *hpage, new_page_t get_new_page,
+		      unsigned long private, bool offlining,
+		      enum migrate_mode mode)
 {
-	int retry = 1;
-	int nr_failed = 0;
-	int pass = 0;
-	struct page *page;
-	struct page *page2;
-	int rc;
-
-	for (pass = 0; pass < 10 && retry; pass++) {
-		retry = 0;
-
-		list_for_each_entry_safe(page, page2, from, lru) {
+	int pass, rc;
+
+	for (pass = 0; pass < 10; pass++) {
+		rc = unmap_and_move_huge_page(get_new_page,
+					      private, hpage, pass > 2, offlining,
+					      mode);
+		switch (rc) {
+		case -ENOMEM:
+			goto out;
+		case -EAGAIN:
+			/* try again */
 			cond_resched();
-
-			rc = unmap_and_move_huge_page(get_new_page,
-					private, page, pass > 2, offlining,
-					mode);
-
-			switch(rc) {
-			case -ENOMEM:
-				goto out;
-			case -EAGAIN:
-				retry++;
-				break;
-			case 0:
-				break;
-			default:
-				/* Permanent failure */
-				nr_failed++;
-				break;
-			}
+			break;
+		case 0:
+			goto out;
+		default:
+			rc = -EIO;
+			goto out;
 		}
 	}
-	rc = 0;
 out:
-	if (rc)
-		return rc;
-
-	return nr_failed + retry;
+	return rc;
 }
 
 #ifdef CONFIG_NUMA