unsigned char s_rd_only;
It is still initialized to 0 in fs/super.c but has no real use anymore
because it is obsoleted by MS_RDONLY.
include/linux/fs.h: unsigned char s_rd_only;
fs/super.c: s->s_rd_only = 0;
fs/super.c: sb->s_rd_only = 0;
Uwe