[PATCH v2 5/7] mm/mglru: make LRU folio prefetch helper an inline function

["Barry Song (Xiaomi)" <baohua@kernel.org>]

`prefetchw_prev_lru_folio()` is currently implemented as a macro with a
potentially unused argument. This makes the helper harder to read and can
also trigger checkpatch warnings about unused macro arguments.

Make it a `static inline` function and remove the unnecessary `_field`
argument. The helper always prefetches the previous folio's `flags`, so
there is no need to make the field configurable.

Signed-off-by: Barry Song (Xiaomi) <baohua@kernel.org>
Tested-by: Xueyuan Chen <xueyuan.chen21@gmail.com>
---
 mm/vmscan.c | 26 +++++++++++++++-----------
 1 file changed, 15 insertions(+), 11 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 2b33d3f44682..81f95a968447 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -182,17 +182,21 @@ struct scan_control {
 };
 
 #ifdef ARCH_HAS_PREFETCHW
-#define prefetchw_prev_lru_folio(_folio, _base, _field)			\
-	do {								\
-		if ((_folio)->lru.prev != _base) {			\
-			struct folio *prev;				\
-									\
-			prev = lru_to_folio(&(_folio->lru));		\
-			prefetchw(&prev->_field);			\
-		}							\
-	} while (0)
+static inline void prefetchw_prev_lru_folio(struct folio *folio,
+		struct list_head *base)
+{
+	if (folio->lru.prev != base) {
+		struct folio *prev;
+
+		prev = lru_to_folio(&folio->lru);
+		prefetchw(&prev->flags);
+	}
+}
 #else
-#define prefetchw_prev_lru_folio(_folio, _base, _field) do { } while (0)
+static inline void prefetchw_prev_lru_folio(struct folio *folio,
+		struct list_head *base)
+{
+}
 #endif
 
 /*
@@ -1695,7 +1699,7 @@ static unsigned long isolate_lru_folios(unsigned long nr_to_scan,
 		struct folio *folio;
 
 		folio = lru_to_folio(src);
-		prefetchw_prev_lru_folio(folio, src, flags);
+		prefetchw_prev_lru_folio(folio, src);
 
 		nr_pages = folio_nr_pages(folio);
 		total_scan += nr_pages;
-- 
2.34.1