[PATCH 05/11] zsmalloc: switch from alloc_vm_area to get_vm_area

[Christoph Hellwig <hch@xxxxxx>]

Just manually pre-fault the PTEs using apply_to_page_range.

Co-developed-by: Minchan Kim <minchan@xxxxxxxxxx>
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
 mm/zsmalloc.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index c36fdff9a37131..918c7b019b3d78 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -1122,10 +1122,16 @@ static inline int __zs_cpu_up(struct mapping_area *area)
         */
        if (area->vm)
                return 0;
-       area->vm = alloc_vm_area(PAGE_SIZE * 2, NULL);
+       area->vm = get_vm_area(PAGE_SIZE * 2, 0);
        if (!area->vm)
                return -ENOMEM;
-       return 0;
+
+       /*
+        * Populate ptes in advance to avoid pte allocation with GFP_KERNEL
+        * in non-preemtible context of zs_map_object.
+        */
+       return apply_to_page_range(&init_mm, (unsigned long)area->vm->addr,
+                       PAGE_SIZE * 2, NULL, NULL);
 }
 
 static inline void __zs_cpu_down(struct mapping_area *area)
-- 
2.28.0