f2fs: move ext_lock out of struct extent_info

Move ext_lock out of struct extent_info, then in the following patches we can
use variables with struct extent_info type as a parameter to pass pure data.

Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 985ed02..0811d65 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -258,9 +258,9 @@
 	if (is_inode_flag_set(fi, FI_NO_EXTENT))
 		return 0;
 
-	read_lock(&fi->ext.ext_lock);
+	read_lock(&fi->ext_lock);
 	if (fi->ext.len == 0) {
-		read_unlock(&fi->ext.ext_lock);
+		read_unlock(&fi->ext_lock);
 		return 0;
 	}
 
@@ -284,10 +284,10 @@
 			bh_result->b_size = UINT_MAX;
 
 		stat_inc_read_hit(inode->i_sb);
-		read_unlock(&fi->ext.ext_lock);
+		read_unlock(&fi->ext_lock);
 		return 1;
 	}
-	read_unlock(&fi->ext.ext_lock);
+	read_unlock(&fi->ext_lock);
 	return 0;
 }
 
@@ -309,7 +309,7 @@
 	fofs = start_bidx_of_node(ofs_of_node(dn->node_page), fi) +
 							dn->ofs_in_node;
 
-	write_lock(&fi->ext.ext_lock);
+	write_lock(&fi->ext_lock);
 
 	start_fofs = fi->ext.fofs;
 	end_fofs = fi->ext.fofs + fi->ext.len - 1;
@@ -366,7 +366,7 @@
 		need_update = true;
 	}
 end_update:
-	write_unlock(&fi->ext.ext_lock);
+	write_unlock(&fi->ext_lock);
 	if (need_update)
 		sync_inode_page(dn);
 	return;