lift sb_start_write() out of ->write()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/coredump.c b/fs/coredump.c
index c647965..288e5c9 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -629,9 +629,11 @@
 		goto close_fail;
 	if (displaced)
 		put_files_struct(displaced);
+	file_start_write(cprm.file);
 	retval = binfmt->core_dump(&cprm);
 	if (retval)
 		current->signal->group_exit_code |= 0x80;
+	file_end_write(cprm.file);
 
 	if (ispipe && core_pipe_limit)
 		wait_for_dump_helpers(cprm.file);