The patch titled
Subject: mm: page_alloc: simplify pageblock migratetype check in __free_one_page()
has been added to the -mm tree. Its filename is
mm-page_alloc-simplify-pageblock-migratetype-check-in-__free_one_page.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-page_alloc-simplify-pageblock-migratetype-check-in-__free_one_page.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-page_alloc-simplify-pageblock-migratetype-check-in-__free_one_page.patch
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------------------------------------------------------
From: Zi Yan <ziy@xxxxxxxxxx>
Subject: mm: page_alloc: simplify pageblock migratetype check in __free_one_page()
Move pageblock migratetype check code in the while loop to simplify the
logic. It also saves redundant buddy page checking code.
Link: https://lkml.kernel.org/r/20220401230804.1658207-1-zi.yan@xxxxxxxx
Link: https://lore.kernel.org/linux-mm/27ff69f9-60c5-9e59-feb2-295250077551@xxxxxxx/
Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
Suggested-by: Vlastimil Babka <vbabka@xxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 46 +++++++++++++++++-----------------------------
1 file changed, 17 insertions(+), 29 deletions(-)
--- a/mm/page_alloc.c~mm-page_alloc-simplify-pageblock-migratetype-check-in-__free_one_page
+++ a/mm/page_alloc.c
@@ -1054,7 +1054,6 @@ static inline void __free_one_page(struc
int migratetype, fpi_t fpi_flags)
{
struct capture_control *capc = task_capc(zone);
- unsigned int max_order = pageblock_order;
unsigned long buddy_pfn;
unsigned long combined_pfn;
struct page *buddy;
@@ -1070,8 +1069,7 @@ static inline void __free_one_page(struc
VM_BUG_ON_PAGE(pfn & ((1 << order) - 1), page);
VM_BUG_ON_PAGE(bad_range(zone, page), page);
-continue_merging:
- while (order < max_order) {
+ while (order < MAX_ORDER - 1) {
if (compaction_capture(capc, page, order, migratetype)) {
__mod_zone_freepage_state(zone, -(1 << order),
migratetype);
@@ -1082,6 +1080,22 @@ continue_merging:
if (!page_is_buddy(page, buddy, order))
goto done_merging;
+
+ if (unlikely(order >= pageblock_order)) {
+ /*
+ * We want to prevent merge between freepages on pageblock
+ * without fallbacks and normal pageblock. Without this,
+ * pageblock isolation could cause incorrect freepage or CMA
+ * accounting or HIGHATOMIC accounting.
+ */
+ int buddy_mt = get_pageblock_migratetype(buddy);
+
+ if (migratetype != buddy_mt
+ && (!migratetype_is_mergeable(migratetype) ||
+ !migratetype_is_mergeable(buddy_mt)))
+ goto done_merging;
+ }
+
/*
* Our buddy is free or it is CONFIG_DEBUG_PAGEALLOC guard page,
* merge with it and move up one order.
@@ -1095,32 +1109,6 @@ continue_merging:
pfn = combined_pfn;
order++;
}
- if (order < MAX_ORDER - 1) {
- /* If we are here, it means order is >= pageblock_order.
- * We want to prevent merge between freepages on pageblock
- * without fallbacks and normal pageblock. Without this,
- * pageblock isolation could cause incorrect freepage or CMA
- * accounting or HIGHATOMIC accounting.
- *
- * We don't want to hit this code for the more frequent
- * low-order merging.
- */
- int buddy_mt;
-
- buddy_pfn = __find_buddy_pfn(pfn, order);
- buddy = page + (buddy_pfn - pfn);
-
- if (!page_is_buddy(page, buddy, order))
- goto done_merging;
- buddy_mt = get_pageblock_migratetype(buddy);
-
- if (migratetype != buddy_mt
- && (!migratetype_is_mergeable(migratetype) ||
- !migratetype_is_mergeable(buddy_mt)))
- goto done_merging;
- max_order = order + 1;
- goto continue_merging;
- }
done_merging:
set_buddy_order(page, order);
_
Patches currently in -mm which might be from ziy@xxxxxxxxxx are
mm-migrate-use-thp_order-instead-of-hpage_pmd_order-for-new-page-allocation.patch
mm-page_alloc-simplify-pageblock-migratetype-check-in-__free_one_page.patch
mm-wrap-__find_buddy_pfn-with-a-necessary-buddy-page-validation.patch
