[PATCH -mm -v3 04/12] mm, THP, swap: Don't allocate huge cluster for file backed swap device

[Huang, Ying]

From: Huang Ying <ying.huang@xxxxxxxxx>

It's hard to write a whole transparent huge page (THP) to a file
backed swap device during swapping out and the file backed swap device
isn't very popular.  So the huge cluster allocation for the file
backed swap device is disabled.

Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Shaohua Li <shli@xxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
---
 mm/swapfile.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index b110faf3c82a..21cbdecbc19a 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -948,9 +948,10 @@ int get_swap_pages(int n_goal, bool cluster, swp_entry_t swp_entries[])
 			spin_unlock(&si->lock);
 			goto nextsi;
 		}
-		if (cluster)
-			n_ret = swap_alloc_cluster(si, swp_entries);
-		else
+		if (cluster) {
+			if (!(si->flags & SWP_FILE))
+				n_ret = swap_alloc_cluster(si, swp_entries);
+		} else
 			n_ret = scan_swap_map_slots(si, SWAP_HAS_CACHE,
 						    n_goal, swp_entries);
 		spin_unlock(&si->lock);
-- 
2.13.2