[PATCH linux-next] mm/page_alloc: avoid overcounting bulk alloc in watermark check

[shengminghu512]

From: Shengming Hu <hu.shengming@xxxxxxxxxx>

alloc_pages_bulk_noprof() only fills NULL slots and already tracks how many
entries are pre-populated via nr_populated.

The fast watermark check was adding nr_pages unconditionally, which can
overestimate the demand. Use (nr_pages - nr_populated) instead, as an 
upper bound on the remaining pages this call can still allocate without
scanning the whole array.

Signed-off-by: Shengming Hu <hu.shengming@xxxxxxxxxx>
---
 mm/page_alloc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 5fd9e4a03..90b978802 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5130,7 +5130,7 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
 
 		cond_accept_memory(zone, 0, alloc_flags);
 retry_this_zone:
-		mark = wmark_pages(zone, alloc_flags & ALLOC_WMARK_MASK) + nr_pages;
+		mark = wmark_pages(zone, alloc_flags & ALLOC_WMARK_MASK) + nr_pages - nr_populated;
 		if (zone_watermark_fast(zone, 0,  mark,
 				zonelist_zone_idx(ac.preferred_zoneref),
 				alloc_flags, gfp)) {
-- 
2.25.1