On Mon, May 22, 2023 at 12:09 AM Huang Ying <ying.huang@xxxxxxxxx> wrote: > > __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) I would add a comment above this function stating that the caller needs to provide protection against swapoff, and refer to the comment above get_swap_device(). Otherwise, LGTM with David's comment. Reviewed-by: Yosry Ahmed <yosryahmed@xxxxxxxxxx> > 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 > >
