The quilt patch titled
Subject: mm/page_alloc: warn on nr_reserved_highatomic underflow
has been removed from the -mm tree. Its filename was
mm-page_alloc-warn-on-nr_reserved_highatomic-underflow.patch
This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: Brendan Jackman <jackmanb@xxxxxxxxxx>
Subject: mm/page_alloc: warn on nr_reserved_highatomic underflow
Date: Tue, 25 Feb 2025 18:45:09 +0000
As documented in the comment this underflow should not happen. The
locking has indeed changed here since the comment was written, see the
migratetype hygiene patches[0]. However, those changes made the locking
_safer_, so the underflow _really_ shouldn't happen now. So upgrade the
comment to a warning.
[0] https://lore.kernel.org/all/20240320180429.678181-7-hannes@xxxxxxxxxxx/T/#m3da87e6cc3348a4640aa298137bc9f8f61b76c84
Link: https://lkml.kernel.org/r/20250225-warn-underflow-v1-1-3dc542941d3a@xxxxxxxxxx
Signed-off-by: Brendan Jackman <jackmanb@xxxxxxxxxx>
Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
--- a/mm/page_alloc.c~mm-page_alloc-warn-on-nr_reserved_highatomic-underflow
+++ a/mm/page_alloc.c
@@ -3095,6 +3095,7 @@ static bool unreserve_highatomic_pageblo
if (!page)
continue;
+ size = max(pageblock_nr_pages, 1UL << order);
/*
* It should never happen but changes to
* locking could inadvertently allow a per-cpu
@@ -3102,8 +3103,8 @@ static bool unreserve_highatomic_pageblo
* while unreserving so be safe and watch for
* underflows.
*/
- size = max(pageblock_nr_pages, 1UL << order);
- size = min(size, zone->nr_reserved_highatomic);
+ if (WARN_ON_ONCE(size > zone->nr_reserved_highatomic))
+ size = zone->nr_reserved_highatomic;
zone->nr_reserved_highatomic -= size;
/*
_
Patches currently in -mm which might be from jackmanb@xxxxxxxxxx are
scripts-gdb-add-lx_per_cpu_ptr.patch
