+ mm-zsmalloc-fix-release-order-of-locks-in-zs_page_migrate.patch added to mm-new branch

The patch titled
     Subject: mm/zsmalloc: fix release order of locks in zs_page_migrate()
has been added to the -mm mm-new branch.  Its filename is
     mm-zsmalloc-fix-release-order-of-locks-in-zs_page_migrate.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-zsmalloc-fix-release-order-of-locks-in-zs_page_migrate.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

The mm-new branch of mm.git is not included in linux-next

If a few days of testing in mm-new is successful, the patch will me moved
into mm.git's mm-unstable branch, which is included in linux-next

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------------------------------------------------------
From: Richard Chang <[email protected]>
Subject: mm/zsmalloc: fix release order of locks in zs_page_migrate()
Date: Tue, 28 Jul 2026 05:53:33 +0000

In zs_page_migrate(), locks are acquired in the following order:
  1. write_lock(&pool->lock)
  2. spin_lock(&class->lock)
  3. zspage_write_trylock(zspage)

However, upon successful page migration, they were being released in
forward acquisition (FIFO) order:
  1. write_unlock(&pool->lock)
  2. spin_unlock(&class->lock)
  3. zspage_write_unlock(zspage)

Fix the unlocking order to release locks in strict reverse (LIFO)
order of acquisition:
  3. zspage_write_unlock(zspage)
  2. spin_unlock(&class->lock)
  1. write_unlock(&pool->lock)

Releasing locks in reverse order of acquisition adheres to standard
kernel locking hygiene, prevents potential lock ordering and lockdep
inconsistencies.

Link: https://lore.kernel.org/[email protected]
Signed-off-by: Richard Chang <[email protected]>
Reviewed-by: Sergey Senozhatsky <[email protected]>
Tested-by: Sergey Senozhatsky <[email protected]>
Cc: Martin Liu <[email protected]>
Cc: Minchan Kim <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
---

 mm/zsmalloc.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/mm/zsmalloc.c~mm-zsmalloc-fix-release-order-of-locks-in-zs_page_migrate
+++ a/mm/zsmalloc.c
@@ -1926,9 +1926,9 @@ static int zs_page_migrate(struct page *
 	 * Since we complete the data copy and set up new zspage structure,
 	 * it's okay to release migration_lock.
 	 */
-	write_unlock(&pool->lock);
-	spin_unlock(&class->lock);
 	zspage_write_unlock(zspage);
+	spin_unlock(&class->lock);
+	write_unlock(&pool->lock);
 
 	zpdesc_get(newzpdesc);
 	if (zpdesc_zone(newzpdesc) != zpdesc_zone(zpdesc)) {
_

Patches currently in -mm which might be from [email protected] are

mm-vmscan-abort-proactive-reclaim-early-when-freezing-for-suspend.patch
mm-zsmalloc-fix-release-order-of-locks-in-zs_page_migrate.patch