The patch titled Subject: mm/zsmalloc: do not pass __GFP_MOVABLE if CONFIG_COMPACTION=n has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-zsmalloc-do-not-pass-__gfp_movable-if-config_compaction=n.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

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

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------------------------------------------------------ From: Harry Yoo harry.yoo@oracle.com Subject: mm/zsmalloc: do not pass __GFP_MOVABLE if CONFIG_COMPACTION=n Date: Fri, 4 Jul 2025 19:30:53 +0900

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).

Link: https://lkml.kernel.org/r/20250704103053.6913-1-harry.yoo@oracle.com Fixes: 48b4800a1c6a ("zsmalloc: page migration support") Signed-off-by: Harry Yoo harry.yoo@oracle.com Acked-by: David Hildenbrand david@redhat.com Cc: Minchan Kim minchan@kernel.org Cc: Sergey Senozhatsky senozhatsky@chromium.org Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

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

--- a/mm/zsmalloc.c~mm-zsmalloc-do-not-pass-__gfp_movable-if-config_compaction=n +++ a/mm/zsmalloc.c @@ -1043,6 +1043,9 @@ static struct zspage *alloc_zspage(struc if (!zspage) return NULL;

+ if (!IS_ENABLED(CONFIG_COMPACTION)) + gfp &= ~__GFP_MOVABLE; + zspage->magic = ZSPAGE_MAGIC; zspage->pool = pool; zspage->class = class->index; _

Patches currently in -mm which might be from harry.yoo@oracle.com are

lib-alloc_tag-do-not-acquire-non-existent-lock-in-alloc_tag_top_users.patch lib-alloc_tag-do-not-acquire-non-existent-lock-in-alloc_tag_top_users-v3.patch mm-zsmalloc-do-not-pass-__gfp_movable-if-config_compaction=n.patch