NFSv4: Truncating file opens should also sync O_DIRECT writes

We don't just want to sync out buffered writes, but also O_DIRECT ones.
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

fs/nfs/inode.c

@@ -133,11 +133,12 @@ void nfs_evict_inode(struct inode *inode)
 	nfs_clear_inode(inode);
 }
 
-static int nfs_sync_inode(struct inode *inode)
+int nfs_sync_inode(struct inode *inode)
 {
 	nfs_inode_dio_wait(inode);
 	return nfs_wb_all(inode);
 }
+EXPORT_SYMBOL_GPL(nfs_sync_inode);
 
 /**
  * nfs_sync_mapping - helper to flush all mmapped dirty data to disk

fs/nfs/nfs4file.c

@@ -59,7 +59,7 @@ nfs4_file_open(struct inode *inode, struct file *filp)
 	if (openflags & O_TRUNC) {
 		attr.ia_valid |= ATTR_SIZE;
 		attr.ia_size = 0;
-		nfs_wb_all(inode);
+		nfs_sync_inode(inode);
 	}
 
 	inode = NFS_PROTO(dir)->open_context(dir, ctx, openflags, &attr, &opened);

include/linux/nfs_fs.h

@@ -512,6 +512,7 @@ extern int  nfs_updatepage(struct file *, struct page *, unsigned int, unsigned
  * Try to write back everything synchronously (but check the
  * return value!)
  */
+extern int nfs_sync_inode(struct inode *inode);
 extern int nfs_wb_all(struct inode *inode);
 extern int nfs_wb_page(struct inode *inode, struct page* page);
 extern int nfs_wb_page_cancel(struct inode *inode, struct page* page);