Colin Ian King reported the following problem (slightly edited) Author: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> Date: Mon Mar 29 11:12:24 2021 +1100 mm/page_alloc: add a bulk page allocator ... Static analysis on linux-next with Coverity has found a potential uninitialized variable issue in function __alloc_pages_bulk with the following commit: ... Uninitialized scalar variable (UNINIT) 15. uninit_use_in_call: Using uninitialized value alloc_flags when calling prepare_alloc_pages. 5056 if (!prepare_alloc_pages(gfp, 0, preferred_nid, nodemask, &ac, &alloc_gfp, &alloc_flags)) The problem is that prepare_alloc_flags only updates alloc_flags which must have a valid initial value. The appropriate initial value is ALLOC_WMARK_LOW to avoid the bulk allocator pushing a zone below the low watermark without waking kswapd assuming the GFP mask allows kswapd to be woken. This is a second fix to the mmotm patch mm-page_alloc-add-a-bulk-page-allocator.patch . It will cause a mild conflict with a later patch due to renaming of an adjacent variable that is trivially resolved. I can post a full series with the fixes merged if that is preferred. Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> --- mm/page_alloc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 92d55f80c289..dabef0b910c9 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -4990,7 +4990,7 @@ unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid, struct list_head *pcp_list; struct alloc_context ac; gfp_t alloc_gfp; - unsigned int alloc_flags; + unsigned int alloc_flags = ALLOC_WMARK_LOW; int allocated = 0; if (WARN_ON_ONCE(nr_pages <= 0))
