6.15-stable review patch. If anyone has any objections, please let me know.
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From: Harry Yoo harry.yoo@oracle.com
commit 694d6b99923eb05a8fd188be44e26077d19f0e21 upstream.
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 Reviewed-by: Sergey Senozhatsky senozhatsky@chromium.org Cc: Minchan Kim minchan@kernel.org Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/zsmalloc.c | 3 +++ 1 file changed, 3 insertions(+)
--- a/mm/zsmalloc.c +++ b/mm/zsmalloc.c @@ -1053,6 +1053,9 @@ 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;