[PATCH -V2 4/5] swap: remove get/put_swap_device() in __swap_duplicate()

From: Huang Ying
Date: Mon May 22 2023 - 03:10:35 EST


__swap_duplicate() is called by

- swap_shmem_alloc(): the page lock of the swap cache is held.

- copy_nonpresent_pte() -> swap_duplicate() and try_to_unmap_one() ->
swap_duplicate(): the page table lock is held.

- __read_swap_cache_async() -> swapcache_prepare(): enclosed with
get/put_swap_device() in __read_swap_cache_async() already.

So, it's safe to remove get/put_swap_device() in __swap_duplicate().

Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx>
Cc: Yang Shi <shy828301@xxxxxxxxx>
Cc: Yu Zhao <yuzhao@xxxxxxxxxx>
---
mm/swapfile.c | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index e9cce775fb25..4dbaea64635d 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -3264,9 +3264,7 @@ static int __swap_duplicate(swp_entry_t entry, unsigned char usage)
unsigned char has_cache;
int err;

- p = get_swap_device(entry);
- if (!p)
- return -EINVAL;
+ p = swp_swap_info(entry);

offset = swp_offset(entry);
ci = lock_cluster_or_swap_info(p, offset);
@@ -3313,7 +3311,6 @@ static int __swap_duplicate(swp_entry_t entry, unsigned char usage)

unlock_out:
unlock_cluster_or_swap_info(p, ci);
- put_swap_device(p);
return err;
}

--
2.39.2