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).

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>

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 999b513c7fdff040c8755709918d756a8ef5b4bb..f3e2215f95eb6e676873a7f0a56258484690add0 100644 (file)
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -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;