ext4: use ext4_da_writepages() for all modes

Rename ext4_da_writepages() to ext4_writepages() and use it for all
modes.  We still need to iterate over all the pages in the case of
data=journalling, but in the case of nodelalloc/data=ordered (which is
what file systems mounted using ext3 backwards compatibility will use)
this will allow us to use a much more efficient I/O submission path.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/include/trace/events/ext4.h b/include/trace/events/ext4.h
index 832a412..72f523e 100644
--- a/include/trace/events/ext4.h
+++ b/include/trace/events/ext4.h
@@ -281,7 +281,7 @@
 	TP_ARGS(inode, pos, len, copied)
 );
 
-TRACE_EVENT(ext4_da_writepages,
+TRACE_EVENT(ext4_writepages,
 	TP_PROTO(struct inode *inode, struct writeback_control *wbc),
 
 	TP_ARGS(inode, wbc),
@@ -379,7 +379,7 @@
 		  __entry->flags)
 );
 
-TRACE_EVENT(ext4_da_writepages_result,
+TRACE_EVENT(ext4_writepages_result,
 	TP_PROTO(struct inode *inode, struct writeback_control *wbc,
 			int ret, int pages_written),