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It would re-allocate a folio if the swap cache was not ready now. We save the new folio to avoid page allocating again. Signed-off-by: Zhaoyu Liu --- mm/swap_state.c | 58 ++++++++++++++++++++++++++----------------------- 1 file changed, 31 insertions(+), 27 deletions(-) diff --git a/mm/swap_state.c b/mm/swap_state.c index a1726e49a5eb..65370d148175 100644 --- a/mm/swap_state.c +++ b/mm/swap_state.c @@ -435,6 +435,8 @@ struct folio *__read_swap_cache_async(swp_entry_t entry= , gfp_t gfp_mask, { struct swap_info_struct *si; struct folio *folio; + struct folio *new_folio =3D NULL; + struct folio *result =3D NULL; void *shadow =3D NULL; =20 *new_page_allocated =3D false; @@ -463,16 +465,19 @@ struct folio *__read_swap_cache_async(swp_entry_t ent= ry, gfp_t gfp_mask, * else swap_off will be aborted if we return NULL. */ if (!swap_swapcount(si, entry) && swap_slot_cache_enabled) - goto fail_put_swap; + goto put_and_return; =20 /* - * Get a new folio to read into from swap. Allocate it now, - * before marking swap_map SWAP_HAS_CACHE, when -EEXIST will - * cause any racers to loop around until we add it to cache. + * Get a new folio to read into from swap. Allocate it now if + * new_folio not exist, before marking swap_map SWAP_HAS_CACHE, + * when -EEXIST will cause any racers to loop around until we + * add it to cache. */ - folio =3D folio_alloc_mpol(gfp_mask, 0, mpol, ilx, numa_node_id()); - if (!folio) - goto fail_put_swap; + if (!new_folio) { + new_folio =3D folio_alloc_mpol(gfp_mask, 0, mpol, ilx, numa_node_id()); + if (!new_folio) + goto put_and_return; + } =20 /* * Swap entry may have been freed since our caller observed it. @@ -480,10 +485,8 @@ struct folio *__read_swap_cache_async(swp_entry_t entr= y, gfp_t gfp_mask, err =3D swapcache_prepare(entry); if (!err) break; - - folio_put(folio); - if (err !=3D -EEXIST) - goto fail_put_swap; + else if (err !=3D -EEXIST) + goto put_and_return; =20 /* * Protect against a recursive call to __read_swap_cache_async() @@ -494,7 +497,7 @@ struct folio *__read_swap_cache_async(swp_entry_t entry= , gfp_t gfp_mask, * __read_swap_cache_async() in the writeback path. */ if (skip_if_exists) - goto fail_put_swap; + goto put_and_return; =20 /* * We might race against __delete_from_swap_cache(), and @@ -509,36 +512,37 @@ struct folio *__read_swap_cache_async(swp_entry_t ent= ry, gfp_t gfp_mask, /* * The swap entry is ours to swap in. Prepare the new folio. */ + __folio_set_locked(new_folio); + __folio_set_swapbacked(new_folio); =20 - __folio_set_locked(folio); - __folio_set_swapbacked(folio); - - if (mem_cgroup_swapin_charge_folio(folio, NULL, gfp_mask, entry)) + if (mem_cgroup_swapin_charge_folio(new_folio, NULL, gfp_mask, entry)) goto fail_unlock; =20 /* May fail (-ENOMEM) if XArray node allocation failed. */ - if (add_to_swap_cache(folio, entry, gfp_mask & GFP_RECLAIM_MASK, &shadow)) + if (add_to_swap_cache(new_folio, entry, gfp_mask & GFP_RECLAIM_MASK, &sha= dow)) goto fail_unlock; =20 mem_cgroup_swapin_uncharge_swap(entry); =20 if (shadow) - workingset_refault(folio, shadow); + workingset_refault(new_folio, shadow); =20 - /* Caller will initiate read into locked folio */ - folio_add_lru(folio); + /* Caller will initiate read into locked new_folio */ + folio_add_lru(new_folio); *new_page_allocated =3D true; + folio =3D new_folio; got_folio: - put_swap_device(si); - return folio; + result =3D folio; + goto put_and_return; =20 fail_unlock: - put_swap_folio(folio, entry); - folio_unlock(folio); - folio_put(folio); -fail_put_swap: + put_swap_folio(new_folio, entry); + folio_unlock(new_folio); +put_and_return: put_swap_device(si); - return NULL; + if (!(*new_page_allocated) && new_folio) + folio_put(new_folio); + return result; } =20 /* --=20 2.25.1