Colin Ian King reported the following problem (slightly edited)
Author: Mel Gorman <mgor...@techsingularity.net>
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 <mgor...@techsingularity.net>
---
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))
