TWxSoftware/twx-linux
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

mm/page_alloc: warn on nr_reserved_highatomic underflow

Browse Source 
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>
This commit is contained in:
Brendan Jackman
2025-02-25 18:45:09 +00:00
committed by Andrew Morton
parent 88fb7794f6
commit ebc29409c2
1 changed files with 3 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files
mm/page_alloc.c
+3 -2
View File
@@ -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;
/*