On Wed, 21 Feb 2024 22:10:28 +1300 Barry Song <21cnbao@xxxxxxxxx> wrote: > From: Barry Song <v-songbaohua@xxxxxxxx> > > The code is quite hard to read, we are still writing swap_map after > errors happen. Though the written value is as before, > > has_cache = count & SWAP_HAS_CACHE; > count &= ~SWAP_HAS_CACHE; > [snipped] > WRITE_ONCE(p->swap_map[offset], count | has_cache); > > It would be better to entirely drop the WRITE_ONCE for both > performance and readability. > > ... > > --- a/mm/swapfile.c > +++ b/mm/swapfile.c > @@ -3320,6 +3320,9 @@ static int __swap_duplicate(swp_entry_t entry, unsigned char usage) > } else > err = -ENOENT; /* unused swap entry */ > > + if (err) > + goto unlock_out; > + > WRITE_ONCE(p->swap_map[offset], count | has_cache); > > unlock_out: I agree, but why add the goto? --- a/mm/swapfile.c~mm-swapfile-__swap_duplicate-drop-redundant-write_once-on-swap_map-for-err-cases-fix +++ a/mm/swapfile.c @@ -3335,10 +3335,8 @@ static int __swap_duplicate(swp_entry_t } else err = -ENOENT; /* unused swap entry */ - if (err) - goto unlock_out; - - WRITE_ONCE(p->swap_map[offset], count | has_cache); + if (!err) + WRITE_ONCE(p->swap_map[offset], count | has_cache); unlock_out: unlock_cluster_or_swap_info(p, ci); _
