The patch titled
Subject: mm: swap: allocate folio only first time in __read_swap_cache_async()
has been added to the -mm mm-unstable branch. Its filename is
mm-swap-allocate-folio-only-first-time-in-__read_swap_cache_async.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-swap-allocate-folio-only-first-time-in-__read_swap_cache_async.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Zhaoyu Liu <liuzhaoyu.zackary@xxxxxxxxxxxxx>
Subject: mm: swap: allocate folio only first time in __read_swap_cache_async()
Date: Wed, 31 Jul 2024 21:31:01 +0800
It should be checked by filemap_get_folio() if SWAP_HAS_CACHE was
marked while reading a share swap page. It would re-allocate a folio
if the swap cache was not ready now. We save the new folio to avoid
page allocating again.
Link: https://lkml.kernel.org/r/20240731133101.GA2096752@bytedance
Signed-off-by: Zhaoyu Liu <liuzhaoyu.zackary@xxxxxxxxxxxxx>
Cc: Domenico Cerasuolo <cerasuolodomenico@xxxxxxxxx>
Cc: Kairui Song <kasong@xxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/swap_state.c | 60 ++++++++++++++++++++++++----------------------
1 file changed, 32 insertions(+), 28 deletions(-)
--- a/mm/swap_state.c~mm-swap-allocate-folio-only-first-time-in-__read_swap_cache_async
+++ a/mm/swap_state.c
@@ -435,6 +435,8 @@ struct folio *__read_swap_cache_async(sw
{
struct swap_info_struct *si;
struct folio *folio;
+ struct folio *new_folio = NULL;
+ struct folio *result = NULL;
void *shadow = NULL;
*new_page_allocated = false;
@@ -463,16 +465,19 @@ struct folio *__read_swap_cache_async(sw
* 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;
/*
- * 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.
- */
- folio = folio_alloc_mpol(gfp_mask, 0, mpol, ilx, numa_node_id());
- if (!folio)
- goto fail_put_swap;
+ * 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.
+ */
+ if (!new_folio) {
+ new_folio = folio_alloc_mpol(gfp_mask, 0, mpol, ilx, numa_node_id());
+ if (!new_folio)
+ goto put_and_return;
+ }
/*
* Swap entry may have been freed since our caller observed it.
@@ -480,10 +485,8 @@ struct folio *__read_swap_cache_async(sw
err = swapcache_prepare(entry, 1);
if (!err)
break;
-
- folio_put(folio);
- if (err != -EEXIST)
- goto fail_put_swap;
+ else if (err != -EEXIST)
+ goto put_and_return;
/*
* Protect against a recursive call to __read_swap_cache_async()
@@ -494,7 +497,7 @@ struct folio *__read_swap_cache_async(sw
* __read_swap_cache_async() in the writeback path.
*/
if (skip_if_exists)
- goto fail_put_swap;
+ goto put_and_return;
/*
* We might race against __delete_from_swap_cache(), and
@@ -509,36 +512,37 @@ struct folio *__read_swap_cache_async(sw
/*
* The swap entry is ours to swap in. Prepare the new folio.
*/
+ __folio_set_locked(new_folio);
+ __folio_set_swapbacked(new_folio);
- __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;
/* 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, &shadow))
goto fail_unlock;
mem_cgroup_swapin_uncharge_swap(entry);
if (shadow)
- workingset_refault(folio, shadow);
+ workingset_refault(new_folio, shadow);
- /* 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 = true;
+ folio = new_folio;
got_folio:
- put_swap_device(si);
- return folio;
+ result = folio;
+ goto put_and_return;
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;
}
/*
_
Patches currently in -mm which might be from liuzhaoyu.zackary@xxxxxxxxxxxxx are
mm-swap-allocate-folio-only-first-time-in-__read_swap_cache_async.patch
