Commit 048a9883 authored by Alexey Dobriyan's avatar Alexey Dobriyan Committed by Andrew Morton
Browse files

include/linux/math.h: fix mult_frac() multiple argument evaluation bug 

mult_frac() evaluates _all_ arguments multiple times in the body.

Clarify comment while I'm at it.

Link: https://lkml.kernel.org/r/f9f9fdbb-ec8e-4f5e-a998-2a58627a1a43@p183


Signed-off-by: default avatarAlexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent d7a0fe9e

include/linux/math.h

+11 −11
Original line number Diff line number Diff line
@@ -118,17 +118,17 @@ __STRUCT_FRACT(s32) 
__STRUCT_FRACT(u32)

#undef __STRUCT_FRACT



/*

 * Multiplies an integer by a fraction, while avoiding unnecessary

 * overflow or loss of precision.

 */

#define mult_frac(x, numer, denom)(			\

{							\

	typeof(x) quot = (x) / (denom);			\

	typeof(x) rem  = (x) % (denom);			\

	(quot * (numer)) + ((rem * (numer)) / (denom));	\

}							\

)

/* Calculate "x * n / d" without unnecessary overflow or loss of precision. */

#define mult_frac(x, n, d)	\

({				\

	typeof(x) x_ = (x);	\

	typeof(n) n_ = (n);	\

	typeof(d) d_ = (d);	\

				\

	typeof(x_) q = x_ / d_;	\

	typeof(x_) r = x_ % d_;	\

	q * n_ + r * n_ / d_;	\

})



#define sector_div(a, b) do_div(a, b)