> > +#ifndef CONFIG_FRONTSWAP
> > +/* all inline routines become no-ops and all externs are ignored */
> > +#define frontswap_enabled (0)
> > +#endif
> > +
> > +static inline int frontswap_test(struct swap_info_struct *sis, pgoff_t
> > offset)
> > +{
> > + int ret = 0;
> > +
> > + if (frontswap_enabled && sis->frontswap_map)
> > + ret = test_bit(offset % BITS_PER_LONG,
> > + &sis->frontswap_map[offset/BITS_PER_LONG]);
>
> if (sis->frontswap_map)
> ret = test_bit(offset, sis->frontswap_map);
>
> (since sis->frontswap_map can't be non-NULL without
> frontswap_enabled being true, and since test_bit() itself already
> does what you open-coded here.
Hi Jan --
Thanks for the review!
> since test_bit() itself already does what you open-coded here
Good catch. Will change. Either is correct and I suspect the
compiler may end up generating the same code, but your code
is much more succinct.
> (since sis->frontswap_map can't be non-NULL without
> frontswap_enabled being true
As noted in the comment immediately preceding, the frontswap_enabled
check serves a second purpose: When CONFIG_FRONTSWAP is
disabled, this entire inline function devolves to a compile-time
constant (0), which avoids a handful of ifdef's in the
core swap subsystem. (This approach was originally suggested
for cleancache by Jeremy Fitzhardinge.)
Also, though this patch never unsets frontswap_enabled, it is
a global and some future tmem backend might unset it, so
it's probably best to leave the extra test anyway.
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href