In the quest to remove all stack VLA usage from the kernel[1], this moves
the math for cookies calculation into macros and allocates a fixed size
array for the maximum number of cookies and adds a runtime sanity check.
(Note that the size was always fixed, but just hidden from the compiler.)
Cc: Jens Axboe <axboe@kernel.dk> Cc: linux-block@vger.kernel.org Signed-off-by: Kees Cook <keescook@chromium.org> Signed-off-by: David S. Miller <davem@davemloft.net>