+ mm-zswap-stop-lru-list-shrinking-when-encounter-warm-region.patch added to mm-unstable branch

+ mm-zswap-stop-lru-list-shrinking-when-encounter-warm-region.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: mm/zswap: stop lru list shrinking when encounter warm region
has been added to the -mm mm-unstable branch.  Its filename is
     mm-zswap-stop-lru-list-shrinking-when-encounter-warm-region.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-zswap-stop-lru-list-shrinking-when-encounter-warm-region.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: Chengming Zhou <zhouchengming@bytedance.com>
Subject: mm/zswap: stop lru list shrinking when encounter warm region
Date: Sun, 04 Feb 2024 03:06:01 +0000

When the shrinker encounter an existing folio in swap cache, it means we
are shrinking into the warmer region.  We should terminate shrinking if
we're in the dynamic shrinker context.

This patch add LRU_STOP to support this, to avoid overshrinking.

Link: https://lkml.kernel.org/r/20240201-b4-zswap-invalidate-entry-v2-3-99d4084260a0@bytedance.com
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Nhat Pham <nphamcs@gmail.com>
Reviewed-by: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/list_lru.h |    2 ++
 mm/list_lru.c            |    3 +++
 mm/zswap.c               |    4 +++-
 3 files changed, 8 insertions(+), 1 deletion(-)

--- a/include/linux/list_lru.h~mm-zswap-stop-lru-list-shrinking-when-encounter-warm-region
+++ a/include/linux/list_lru.h
@@ -24,6 +24,8 @@ enum lru_status {
 	LRU_SKIP,		/* item cannot be locked, skip */
 	LRU_RETRY,		/* item not freeable. May drop the lock
 				   internally, but has to return locked. */
+	LRU_STOP,		/* stop lru list walking. May drop the lock
+				   internally, but has to return locked. */
 };
 
 struct list_lru_one {
--- a/mm/list_lru.c~mm-zswap-stop-lru-list-shrinking-when-encounter-warm-region
+++ a/mm/list_lru.c
@@ -243,6 +243,9 @@ restart:
 			 */
 			assert_spin_locked(&nlru->lock);
 			goto restart;
+		case LRU_STOP:
+			assert_spin_locked(&nlru->lock);
+			goto out;
 		default:
 			BUG();
 		}
--- a/mm/zswap.c~mm-zswap-stop-lru-list-shrinking-when-encounter-warm-region
+++ a/mm/zswap.c
@@ -1315,8 +1315,10 @@ static enum lru_status shrink_memcg_cb(s
 		 * into the warmer region. We should terminate shrinking (if we're in the dynamic
 		 * shrinker context).
 		 */
-		if (writeback_result == -EEXIST && encountered_page_in_swapcache)
+		if (writeback_result == -EEXIST && encountered_page_in_swapcache) {
+			ret = LRU_STOP;
 			*encountered_page_in_swapcache = true;
+		}
 	} else {
 		zswap_written_back_pages++;
 	}
_

Patches currently in -mm which might be from zhouchengming@bytedance.com are

mm-zswap-dont-return-lru_skip-if-we-have-dropped-lru-lock.patch
mm-zswap-make-sure-each-swapfile-always-have-zswap-rb-tree.patch
mm-zswap-split-zswap-rb-tree.patch
mm-zswap-fix-race-between-lru-writeback-and-swapoff.patch
mm-list_lru-remove-list_lru_putback.patch
mm-zswap-add-more-comments-in-shrink_memcg_cb.patch
mm-zswap-invalidate-zswap-entry-when-swap-entry-free.patch
mm-zswap-stop-lru-list-shrinking-when-encounter-warm-region.patch
mm-zswap-remove-duplicate_entry-debug-value.patch
mm-zswap-only-support-zswap_exclusive_loads_enabled.patch
mm-zswap-zswap-entry-doesnt-need-refcount-anymore.patch