Commit 0abd1557e21c added rcu_dereference() for dereferencing ip->i_gl
in gfs2_permission. This now causes lockdep to complain when
gfs2_permission is called in non-RCU context:
WARNING: suspicious RCU usage in gfs2_permission
Switch to rcu_dereference_check() and check for the MAY_NOT_BLOCK flag
to shut up lockdep when we know that dereferencing ip->i_gl is safe.
Fixes: 0abd1557e21c ("gfs2: fix an oops in gfs2_permission")
Reported-by: syzbot+3e5130844b0c0e2b4948@syzkaller.appspotmail.com
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
074d7306a4