NFS: Add basic functionality for tracking folios in struct nfs_page

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

fs/nfs/pagelist.c

@@ -500,9 +500,10 @@ nfs_create_subreq(struct nfs_page *req,
 {
 	struct nfs_page *last;
 	struct nfs_page *ret;
+	struct page *page = nfs_page_to_page(req, pgbase);
 
-	ret = __nfs_create_request(req->wb_lock_context, req->wb_page,
-			pgbase, offset, count);
+	ret = __nfs_create_request(req->wb_lock_context, page, pgbase, offset,
+				   count);
 	if (!IS_ERR(ret)) {
 		/* find the last request */
 		for (last = req->wb_head;

include/linux/nfs_page.h

@@ -25,6 +25,7 @@
 enum {
 	PG_BUSY = 0,		/* nfs_{un}lock_request */
 	PG_MAPPED,		/* page private set for buffered io */
+	PG_FOLIO,		/* Tracking a folio (unset for O_DIRECT) */
 	PG_CLEAN,		/* write succeeded */
 	PG_COMMIT_TO_DS,	/* used by pnfs layouts */
 	PG_INODE_REF,		/* extra ref held by inode when in writeback */
@@ -41,7 +42,10 @@ enum {
 struct nfs_inode;
 struct nfs_page {
 	struct list_head	wb_list;	/* Defines state of page: */
-	struct page		*wb_page;	/* page to read in/write out */
+	union {
+		struct page	*wb_page;	/* page to read in/write out */
+		struct folio	*wb_folio;
+	};
 	struct nfs_lock_context	*wb_lock_context;	/* lock context info */
 	pgoff_t			wb_index;	/* Offset >> PAGE_SHIFT */
 	unsigned int		wb_offset,	/* Offset & ~PAGE_MASK */
@@ -153,6 +157,38 @@ extern	int nfs_page_set_headlock(struct nfs_page *req);
 extern void nfs_page_clear_headlock(struct nfs_page *req);
 extern bool nfs_async_iocounter_wait(struct rpc_task *, struct nfs_lock_context *);
 
+/**
+ * nfs_page_to_folio - Retrieve a struct folio for the request
+ * @req: pointer to a struct nfs_page
+ *
+ * If a folio was assigned to @req, then return it, otherwise return NULL.
+ */
+static inline struct folio *nfs_page_to_folio(const struct nfs_page *req)
+{
+	if (test_bit(PG_FOLIO, &req->wb_flags))
+		return req->wb_folio;
+	return NULL;
+}
+
+/**
+ * nfs_page_to_page - Retrieve a struct page for the request
+ * @req: pointer to a struct nfs_page
+ * @pgbase: folio byte offset
+ *
+ * Return the page containing the byte that is at offset @pgbase relative
+ * to the start of the folio.
+ * Note: The request starts at offset @req->wb_pgbase.
+ */
+static inline struct page *nfs_page_to_page(const struct nfs_page *req,
+					    size_t pgbase)
+{
+	struct folio *folio = nfs_page_to_folio(req);
+
+	if (folio == NULL)
+		return req->wb_page;
+	return folio_page(folio, pgbase >> PAGE_SHIFT);
+}
+
 /*
  * Lock the page of an asynchronous request
  */