Revert "fs: nfs: fix missing refcnt by replacing folio_set_private by folio_attach_private"

This reverts commit 03e02b9.

As was pointed out during code review, there is no need to use
folio_attach_private()/folio_detach_private() when a refcount to the
folio is already carried by the struct nfs_page.

Signed-off-by: Trond Myklebust <[email protected]>

Author: Trond Myklebust

fs/nfs/write.c

@@ -772,7 +772,8 @@ static void nfs_inode_add_request(struct nfs_page *req)
 	nfs_lock_request(req);
 	spin_lock(&mapping->i_private_lock);
 	set_bit(PG_MAPPED, &req->wb_flags);
-	folio_attach_private(folio, req);
+	folio_set_private(folio);
+	folio->private = req;
 	spin_unlock(&mapping->i_private_lock);
 	atomic_long_inc(&nfsi->nrequests);
 	/* this a head request for a page group - mark it as having an
@@ -796,7 +797,8 @@ static void nfs_inode_remove_request(struct nfs_page *req)
 
 		spin_lock(&mapping->i_private_lock);
 		if (likely(folio)) {
-			folio_detach_private(folio);
+			folio->private = NULL;
+			folio_clear_private(folio);
 			clear_bit(PG_MAPPED, &req->wb_head->wb_flags);
 		}
 		spin_unlock(&mapping->i_private_lock);