[PATCH 3/7] mm/page_alloc: Split out buddy removal code from rmqueue into separate helper

Mel Gorman
2022-06-13T17:32:18Z

This is a preparation page to allow the buddy removal code to be reused in
a later patch.

No functional change.

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Tested-by: Minchan Kim <minchan@kernel.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Reviewed-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
---
mm/page_alloc.c | 81 ++++++++++++++++++++++++++++---------------------
1 file changed, 47 insertions(+), 34 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index febd97f4a2fc..44d198af4b35 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3637,6 +3637,43 @@ static inline void zone_statistics(struct zone *preferred_zone, struct zone *z,
#endif
}

+static __always_inline
+struct page *rmqueue_buddy(struct zone *preferred_zone, struct zone *zone,
+ unsigned int order, unsigned int alloc_flags,
+ int migratetype)
+{
+ struct page *page;
+ unsigned long flags;
+
+ do {
+ page = NULL;
+ spin_lock_irqsave(&zone->lock, flags);
+ /*
+ * order-0 request can reach here when the pcplist is skipped
+ * due to non-CMA allocation context. HIGHATOMIC area is
+ * reserved for high-order atomic allocation, so order-0
+ * request should skip it.
+ */
+ if (order > 0 && alloc_flags & ALLOC_HARDER)
+ page = __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC);
+ if (!page) {
+ page = __rmqueue(zone, order, migratetype, alloc_flags);
+ if (!page) {
+ spin_unlock_irqrestore(&zone->lock, flags);
+ return NULL;
+ }
+ }
+ __mod_zone_freepage_state(zone, -(1 << order),
+ get_pcppage_migratetype(page));
+ spin_unlock_irqrestore(&zone->lock, flags);
+ } while (check_new_pages(page, order));
+
+ __count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order);
+ zone_statistics(preferred_zone, zone, 1);
+
+ return page;
+}
+
/* Remove page from the per-cpu list, caller must protect the list */
static inline
struct page *__rmqueue_pcplist(struct zone *zone, unsigned int order,
@@ -3717,9 +3754,14 @@ struct page *rmqueue(struct zone *preferred_zone,
gfp_t gfp_flags, unsigned int alloc_flags,
int migratetype)
{
- unsigned long flags;
struct page *page;

+ /*
+ * We most definitely don't want callers attempting to
+ * allocate greater than order-1 page units with __GFP_NOFAIL.
+ */
+ WARN_ON_ONCE((gfp_flags & __GFP_NOFAIL) && (order > 1));
+
if (likely(pcp_allowed_order(order))) {
/*
* MIGRATE_MOVABLE pcplist could have the pages on CMA area and
@@ -3733,35 +3775,10 @@ struct page *rmqueue(struct zone *preferred_zone,
}
}

- /*
- * We most definitely don't want callers attempting to
- * allocate greater than order-1 page units with __GFP_NOFAIL.
- */
- WARN_ON_ONCE((gfp_flags & __GFP_NOFAIL) && (order > 1));
-
- do {
- page = NULL;
- spin_lock_irqsave(&zone->lock, flags);
- /*
- * order-0 request can reach here when the pcplist is skipped
- * due to non-CMA allocation context. HIGHATOMIC area is
- * reserved for high-order atomic allocation, so order-0
- * request should skip it.
- */
- if (order > 0 && alloc_flags & ALLOC_HARDER)
- page = __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC);
- if (!page) {
- page = __rmqueue(zone, order, migratetype, alloc_flags);
- if (!page)
- goto failed;
- }
- __mod_zone_freepage_state(zone, -(1 << order),
- get_pcppage_migratetype(page));
- spin_unlock_irqrestore(&zone->lock, flags);
- } while (check_new_pages(page, order));
-
- __count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order);
- zone_statistics(preferred_zone, zone, 1);
+ page = rmqueue_buddy(preferred_zone, zone, order, alloc_flags,
+ migratetype);
+ if (unlikely(!page))
+ return NULL;

out:
/* Separate test+clear to avoid unnecessary atomics */
@@ -3772,10 +3789,6 @@ struct page *rmqueue(struct zone *preferred_zone,

VM_BUG_ON_PAGE(page && bad_range(zone, page), page);
return page;
-
-failed:
- spin_unlock_irqrestore(&zone->lock, flags);
- return NULL;
}

#ifdef CONFIG_FAIL_PAGE_ALLOC
--
2.35.3