diff options
| author | Brendan Jackman <jackmanb@google.com> | 2025-02-25 18:45:09 +0000 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2025-03-16 22:06:44 -0700 |
| commit | ebc29409c2966bd6a6215b27fc654de7f55ce099 (patch) | |
| tree | a282e8dea7709f6a34df28265da632a508a31d3d /mm/page_alloc.c | |
| parent | 88fb7794f69375b08ff5432d8b5bc79eeb3e1dbe (diff) | |
mm/page_alloc: warn on nr_reserved_highatomic underflow
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@cmpxchg.org/T/#m3da87e6cc3348a4640aa298137bc9f8f61b76c84
Link: https://lkml.kernel.org/r/20250225-warn-underflow-v1-1-3dc542941d3a@google.com
Signed-off-by: Brendan Jackman <jackmanb@google.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/page_alloc.c')
| -rw-r--r-- | mm/page_alloc.c | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 945437d7ac44..3c5624380b6c 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3095,6 +3095,7 @@ static bool unreserve_highatomic_pageblock(const struct alloc_context *ac, 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_pageblock(const struct alloc_context *ac, * 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; /* |