[RFC PATCH 6/9] mm/rmap: introduce migrate_walk_arg

[Huan Yang <link@vivo.com>]

In try_to_migrate, rmap_one as well as the done and exit hooks may
require more information from try_to_migrate to assist in performing
migration-related operations.

This patch introduces a new migrate_walk_arg structure to serve as
the arg parameter for rmap_walk_control in try_to_migrate.

Signed-off-by: Huan Yang <link@vivo.com>
---
 mm/rmap.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/mm/rmap.c b/mm/rmap.c
index 66b48ab192f5..2433e12c131d 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -2261,6 +2261,10 @@ void try_to_unmap(struct folio *folio, enum ttu_flags flags)
 	rmap_walk(folio, &rwc);
 }
 
+struct migrate_walk_arg {
+	enum ttu_flags flags;
+};
+
 /*
  * @arg: enum ttu_flags will be passed to this argument.
  *
@@ -2276,7 +2280,8 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma,
 	pte_t pteval;
 	struct page *subpage;
 	struct mmu_notifier_range range;
-	enum ttu_flags flags = (enum ttu_flags)(long)arg;
+	struct migrate_walk_arg *mwa = (struct migrate_walk_arg *)arg;
+	enum ttu_flags flags = mwa->flags;
 	unsigned long pfn;
 	unsigned long hsz = 0;
 
@@ -2575,9 +2580,13 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma,
  */
 void try_to_migrate(struct folio *folio, enum ttu_flags flags)
 {
+	struct migrate_walk_arg arg = {
+		.flags = flags,
+	};
+
 	struct rmap_walk_control rwc = {
 		.rmap_one = try_to_migrate_one,
-		.arg = (void *)flags,
+		.arg = (void *)&arg,
 		.done = folio_not_mapped,
 		.locked = flags & TTU_RMAP_LOCKED,
 		.anon_lock = folio_lock_anon_vma_read,
-- 
2.34.1