[RFC PATCH 08/25] mm: migrate: Add copy_page_dma into migrate_page_copy.

[Zi Yan <zi.yan@xxxxxxxx>]

From: Zi Yan <ziy@xxxxxxxxxx>

Fallback to copy_highpage when it fails.

Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
---
 include/linux/migrate_mode.h   |  1 +
 include/uapi/linux/mempolicy.h |  1 +
 mm/migrate.c                   | 31 +++++++++++++++++++++----------
 3 files changed, 23 insertions(+), 10 deletions(-)

diff --git a/include/linux/migrate_mode.h b/include/linux/migrate_mode.h
index 5bc8a77..4f7f5557 100644
--- a/include/linux/migrate_mode.h
+++ b/include/linux/migrate_mode.h
@@ -23,6 +23,7 @@ enum migrate_mode {
 	MIGRATE_MODE_MASK = 3,
 	MIGRATE_SINGLETHREAD	= 0,
 	MIGRATE_MT				= 1<<4,
+	MIGRATE_DMA				= 1<<5,
 };
 
 #endif		/* MIGRATE_MODE_H_INCLUDED */
diff --git a/include/uapi/linux/mempolicy.h b/include/uapi/linux/mempolicy.h
index 890269b..49573a6 100644
--- a/include/uapi/linux/mempolicy.h
+++ b/include/uapi/linux/mempolicy.h
@@ -48,6 +48,7 @@ enum {
 #define MPOL_MF_LAZY	 (1<<3)	/* Modifies '_MOVE:  lazy migrate on fault */
 #define MPOL_MF_INTERNAL (1<<4)	/* Internal flags start here */
 
+#define MPOL_MF_MOVE_DMA (1<<5)	/* Use DMA page copy routine */
 #define MPOL_MF_MOVE_MT  (1<<6)	/* Use multi-threaded page copy routine */
 
 #define MPOL_MF_VALID	(MPOL_MF_STRICT   | 	\
diff --git a/mm/migrate.c b/mm/migrate.c
index 8a344e2..09114d3 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -553,15 +553,21 @@ int migrate_huge_page_move_mapping(struct address_space *mapping,
  * specialized.
  */
 static void __copy_gigantic_page(struct page *dst, struct page *src,
-				int nr_pages)
+				int nr_pages, enum migrate_mode mode)
 {
 	int i;
 	struct page *dst_base = dst;
 	struct page *src_base = src;
+	int rc = -EFAULT;
 
 	for (i = 0; i < nr_pages; ) {
 		cond_resched();
-		copy_highpage(dst, src);
+
+		if (mode & MIGRATE_DMA)
+			rc = copy_page_dma(dst, src, 1);
+
+		if (rc)
+			copy_highpage(dst, src);
 
 		i++;
 		dst = mem_map_next(dst, dst_base, i);
@@ -582,7 +588,7 @@ static void copy_huge_page(struct page *dst, struct page *src,
 		nr_pages = pages_per_huge_page(h);
 
 		if (unlikely(nr_pages > MAX_ORDER_NR_PAGES)) {
-			__copy_gigantic_page(dst, src, nr_pages);
+			__copy_gigantic_page(dst, src, nr_pages, mode);
 			return;
 		}
 	} else {
@@ -597,6 +603,8 @@ static void copy_huge_page(struct page *dst, struct page *src,
 
 	if (mode & MIGRATE_MT)
 		rc = copy_page_multithread(dst, src, nr_pages);
+	else if (mode & MIGRATE_DMA)
+		rc = copy_page_dma(dst, src, nr_pages);
 
 	if (rc)
 		for (i = 0; i < nr_pages; i++) {
@@ -674,8 +682,9 @@ void migrate_page_copy(struct page *newpage, struct page *page,
 {
 	if (PageHuge(page) || PageTransHuge(page))
 		copy_huge_page(newpage, page, mode);
-	else
+	else {
 		copy_highpage(newpage, page);
+	}
 
 	migrate_page_states(newpage, page);
 }
@@ -1511,7 +1520,8 @@ static int store_status(int __user *status, int start, int value, int nr)
 }
 
 static int do_move_pages_to_node(struct mm_struct *mm,
-		struct list_head *pagelist, int node, bool migrate_mt)
+		struct list_head *pagelist, int node,
+		bool migrate_mt, bool migrate_dma)
 {
 	int err;
 
@@ -1519,7 +1529,8 @@ static int do_move_pages_to_node(struct mm_struct *mm,
 		return 0;
 
 	err = migrate_pages(pagelist, alloc_new_node_page, NULL, node,
-			MIGRATE_SYNC | (migrate_mt ? MIGRATE_MT : MIGRATE_SINGLETHREAD),
+			MIGRATE_SYNC | (migrate_mt ? MIGRATE_MT : MIGRATE_SINGLETHREAD) |
+			(migrate_dma ? MIGRATE_DMA : MIGRATE_SINGLETHREAD),
 			MR_SYSCALL);
 	if (err)
 		putback_movable_pages(pagelist);
@@ -1642,7 +1653,7 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
 			start = i;
 		} else if (node != current_node) {
 			err = do_move_pages_to_node(mm, &pagelist, current_node,
-				flags & MPOL_MF_MOVE_MT);
+				flags & MPOL_MF_MOVE_MT, flags & MPOL_MF_MOVE_DMA);
 			if (err)
 				goto out;
 			err = store_status(status, start, current_node, i - start);
@@ -1666,7 +1677,7 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
 			goto out_flush;
 
 		err = do_move_pages_to_node(mm, &pagelist, current_node,
-				flags & MPOL_MF_MOVE_MT);
+				flags & MPOL_MF_MOVE_MT, flags & MPOL_MF_MOVE_DMA);
 		if (err)
 			goto out;
 		if (i > start) {
@@ -1682,7 +1693,7 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
 
 	/* Make sure we do not overwrite the existing error */
 	err1 = do_move_pages_to_node(mm, &pagelist, current_node,
-				flags & MPOL_MF_MOVE_MT);
+				flags & MPOL_MF_MOVE_MT, flags & MPOL_MF_MOVE_DMA);
 	if (!err1)
 		err1 = store_status(status, start, current_node, i - start);
 	if (!err)
@@ -1778,7 +1789,7 @@ static int kernel_move_pages(pid_t pid, unsigned long nr_pages,
 	nodemask_t task_nodes;
 
 	/* Check flags */
-	if (flags & ~(MPOL_MF_MOVE|MPOL_MF_MOVE_ALL|MPOL_MF_MOVE_MT))
+	if (flags & ~(MPOL_MF_MOVE|MPOL_MF_MOVE_ALL|MPOL_MF_MOVE_MT|MPOL_MF_MOVE_DMA))
 		return -EINVAL;
 
 	if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE))
-- 
2.7.4