[PATCH -V3 4/5] swap: remove get/put_swap_device() in __swap_duplicate()

Huang Ying
2023-05-29T06:14:44Z

__swap_duplicate() is called by

- swap_shmem_alloc(): the folio in swap cache is locked.

- 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@intel.com>
Reviewed-by: Yosry Ahmed <yosryahmed@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Chris Li <chrisl@kernel.org>
---
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