[to-be-updated] mm-zswap-enable-static-key-after-runtime-pool-recovery.patch removed from -mm tree

[to-be-updated] mm-zswap-enable-static-key-after-runtime-pool-recovery.patch removed from -mm tree

[Andrew Morton]

The quilt patch titled
     Subject: mm/zswap: enable static key after runtime pool recovery
has been removed from the -mm tree.  Its filename was
     mm-zswap-enable-static-key-after-runtime-pool-recovery.patch

This patch was dropped because an updated version will be issued

------------------------------------------------------
From: Longlong Xia <xialonglong@kylinos.cn>
Subject: mm/zswap: enable static key after runtime pool recovery
Date: Sat, 5 Sep 2026 20:50:28 +0800

When CONFIG_ZSWAP_DEFAULT_ON is disabled, zswap_setup() can complete
without a pool after a failed initial pool creation.  A later compressor
parameter update can create and publish a pool, but does not enable
zswap_ever_enabled.

If users then enable zswap, zswap_store() intercepts swapout while
zswap_load() still returns -ENOENT without consulting the xarray.  The
swapin path therefore reads a stale backing swap slot because the store
skipped writing it.

Enable the static key after a successful compressor and pool update.  Do
this outside zswap_pools_lock because static key updates may sleep.

Verified with fault injection on a stock kernel (compressor builtin,
CONFIG_ZSWAP_DEFAULT_ON=n):

  1. Boot with zswap.enabled=1; pool creation fails, init completes
     pool-less (static key off).
  2. Echo an available compressor name to zswap.compressor; a pool is
     recovered but the key stays off.
  3. Enable zswap.
  4. madvise(MADV_PAGEOUT) a pattern-verified 512 MiB region, then
     fault it back in and verify.

Step 4 reads back 131072/131072 zeroed pages (zswpin=0, zswpout=131072)
without this patch; all pages intact (zswpin=131072) with it.

Link: https://lore.kernel.org/20260905125101.2970456-1-xialonglong2025@163.com
Fixes: 2d4d2b1cfb85 ("mm: zswap: add zswap_never_enabled()")
Assisted-by: Zcode:GLM-5.3
Signed-off-by: Longlong Xia <xialonglong@kylinos.cn>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Longlong Xia <xialonglong@kylinos.cn>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/zswap.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/mm/zswap.c~mm-zswap-enable-static-key-after-runtime-pool-recovery
+++ a/mm/zswap.c
@@ -586,6 +586,9 @@ static int zswap_compressor_param_set(co
 	else
 		ret = -EINVAL;
 
+	if (!ret)
+		static_branch_enable(&zswap_ever_enabled);
+
 	spin_lock_bh(&zswap_pools_lock);
 
 	if (!ret) {
_

Patches currently in -mm which might be from xialonglong@kylinos.cn are

mm-hugetlb-do-not-dissolve-gigantic-pages-without-runtime-support.patch
mm-hugetlb-warn-instead-of-silently-bailing-gigantic-pages-without-runtime-support.patch
mm-hugetlb-preserve-source-surplus-accounting-during-demotion.patch
mm-hugetlb-cap-demotion-at-currently-available-free-pages.patch
mm-zswap-publish-the-initial-pool-with-list_add_rcu.patch
mm-zswap-enable-zswap_ever_enabled-in-zswap_pool_create.patch