[PATCH 1/4] pagevec: Allow pagevecs to be different sizes

["Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>]

Declaring a pagevec continues to create a pagevec which is the same size,
but functions which manipulate pagevecs no longer rely on this.

Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
 include/linux/pagevec.h | 20 ++++++++++++++++----
 mm/swap.c               |  8 ++++++++
 2 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/include/linux/pagevec.h b/include/linux/pagevec.h
index 875a3f0d9dd2..ee5d3c4da8da 100644
--- a/include/linux/pagevec.h
+++ b/include/linux/pagevec.h
@@ -18,9 +18,15 @@ struct page;
 struct address_space;
 
 struct pagevec {
-	unsigned char nr;
-	bool percpu_pvec_drained;
-	struct page *pages[PAGEVEC_SIZE];
+	union {
+		struct {
+			unsigned char sz;
+			unsigned char nr;
+			bool percpu_pvec_drained;
+			struct page *pages[PAGEVEC_SIZE];
+		};
+		void *__p[PAGEVEC_SIZE + 1];
+	};
 };
 
 void __pagevec_release(struct pagevec *pvec);
@@ -41,6 +47,7 @@ static inline unsigned pagevec_lookup_tag(struct pagevec *pvec,
 
 static inline void pagevec_init(struct pagevec *pvec)
 {
+	pvec->sz = PAGEVEC_SIZE;
 	pvec->nr = 0;
 	pvec->percpu_pvec_drained = false;
 }
@@ -50,6 +57,11 @@ static inline void pagevec_reinit(struct pagevec *pvec)
 	pvec->nr = 0;
 }
 
+static inline unsigned pagevec_size(struct pagevec *pvec)
+{
+	return pvec->sz;
+}
+
 static inline unsigned pagevec_count(struct pagevec *pvec)
 {
 	return pvec->nr;
@@ -57,7 +69,7 @@ static inline unsigned pagevec_count(struct pagevec *pvec)
 
 static inline unsigned pagevec_space(struct pagevec *pvec)
 {
-	return PAGEVEC_SIZE - pvec->nr;
+	return pvec->sz - pvec->nr;
 }
 
 /*
diff --git a/mm/swap.c b/mm/swap.c
index 2ee3522a7170..d093fb30f038 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -52,6 +52,7 @@ struct lru_rotate {
 };
 static DEFINE_PER_CPU(struct lru_rotate, lru_rotate) = {
 	.lock = INIT_LOCAL_LOCK(lock),
+	.pvec.sz = PAGEVEC_SIZE,
 };
 
 /*
@@ -70,6 +71,13 @@ struct lru_pvecs {
 };
 static DEFINE_PER_CPU(struct lru_pvecs, lru_pvecs) = {
 	.lock = INIT_LOCAL_LOCK(lock),
+	.lru_add.sz = PAGEVEC_SIZE,
+	.lru_deactivate_file.sz = PAGEVEC_SIZE,
+	.lru_deactivate.sz = PAGEVEC_SIZE,
+	.lru_lazyfree.sz = PAGEVEC_SIZE,
+#ifdef CONFIG_SMP
+	.activate_page.sz = PAGEVEC_SIZE,
+#endif
 };
 
 /*
-- 
2.28.0