FAILED: patch "[PATCH] mm/zsmalloc: do not pass __GFP_MOVABLE if CONFIG_COMPACTION=n" failed to apply to 5.4-stable tree

The patch below does not apply to the 5.4-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.4.y
git checkout FETCH_HEAD
git cherry-pick -x 694d6b99923eb05a8fd188be44e26077d19f0e21
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2025072811-ethanol-arbitrary-a664@gregkh' --subject-prefix 'PATCH 5.4.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 694d6b99923eb05a8fd188be44e26077d19f0e21 Mon Sep 17 00:00:00 2001
From: Harry Yoo <[email protected]>
Date: Fri, 4 Jul 2025 19:30:53 +0900
Subject: [PATCH] mm/zsmalloc: do not pass __GFP_MOVABLE if CONFIG_COMPACTION=n

Commit 48b4800a1c6a ("zsmalloc: page migration support") added support for migrating zsmalloc pages using the movable_operations migration framework. However, the commit did not take into account that zsmalloc supports migration only when CONFIG_COMPACTION is enabled. Tracing shows that zsmalloc was still passing the __GFP_MOVABLE flag even when compaction is not supported.

This can result in unmovable pages being allocated from movable page blocks (even without stealing page blocks), ZONE_MOVABLE and CMA area.

Possible user visible effects:
- Some ZONE_MOVABLE memory can be not actually movable
- CMA allocation can fail because of this
- Increased memory fragmentation due to ignoring the page mobility grouping feature
I'm not really sure who uses kernels without compaction support, though :(

To fix this, clear the __GFP_MOVABLE flag when
!IS_ENABLED(CONFIG_COMPACTION).

index 999b513c7fdf..f3e2215f95eb 100644
@@ -1043,6 +1043,9 @@ static struct zspage *alloc_zspage(struct zs_pool *pool,
 	if (!zspage)
 		return NULL;
 
+	if (!IS_ENABLED(CONFIG_COMPACTION))
+		gfp &= ~__GFP_MOVABLE;
+
 	zspage->magic = ZSPAGE_MAGIC;
 	zspage->pool = pool;
 	zspage->class = class->index;

From: Miaohe Lin <[email protected]>

[ Upstream commit f0231305acd53375c6cf736971bf5711105dd6bb ]

We always memset the zspage allocated via cache_alloc_zspage. So it's more convenient to use kmem_cache_zalloc in cache_alloc_zspage than caller do it manually.

Stable-dep-of: 694d6b99923e ("mm/zsmalloc: do not pass __GFP_MOVABLE if CONFIG_COMPACTION=n")

---
 mm/zsmalloc.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

index 6b100f02ee43..eae16c6b6fc6 100644
@@ -357,7 +357,7 @@ static void cache_free_handle(struct zs_pool *pool, unsigned long handle)
 
 static struct zspage *cache_alloc_zspage(struct zs_pool *pool, gfp_t flags)
 {
-	return kmem_cache_alloc(pool->zspage_cachep,
+	return kmem_cache_zalloc(pool->zspage_cachep,
 			flags & ~(__GFP_HIGHMEM|__GFP_MOVABLE));
 }
 

@@ -1067,7 +1067,6 @@ static struct zspage *alloc_zspage(struct zs_pool *pool,
 	if (!zspage)
 		return NULL;
 
-	memset(zspage, 0, sizeof(struct zspage));
 	zspage->magic = ZSPAGE_MAGIC;
 	migrate_lock_init(zspage);
 

2.39.5

From: Harry Yoo <[email protected]>

[ Upstream commit 694d6b99923eb05a8fd188be44e26077d19f0e21 ]

Commit 48b4800a1c6a ("zsmalloc: page migration support") added support for migrating zsmalloc pages using the movable_operations migration framework. However, the commit did not take into account that zsmalloc supports migration only when CONFIG_COMPACTION is enabled. Tracing shows that zsmalloc was still passing the __GFP_MOVABLE flag even when compaction is not supported.

This can result in unmovable pages being allocated from movable page blocks (even without stealing page blocks), ZONE_MOVABLE and CMA area.

Possible user visible effects:
- Some ZONE_MOVABLE memory can be not actually movable
- CMA allocation can fail because of this
- Increased memory fragmentation due to ignoring the page mobility grouping feature
I'm not really sure who uses kernels without compaction support, though :(

To fix this, clear the __GFP_MOVABLE flag when
!IS_ENABLED(CONFIG_COMPACTION).

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

index eae16c6b6fc6..b379deb0a10c 100644
@@ -1067,6 +1067,9 @@ static struct zspage *alloc_zspage(struct zs_pool *pool,
 	if (!zspage)
 		return NULL;
 
+	if (!IS_ENABLED(CONFIG_COMPACTION))
+		gfp &= ~__GFP_MOVABLE;
+
 	zspage->magic = ZSPAGE_MAGIC;
 	migrate_lock_init(zspage);
 

2.39.5