Messages in this thread |  | | Date | Thu, 20 Sep 2001 15:48:06 +0200 | From | Stephan von Krawczynski <> | Subject | Fw: Re: [PATCH] fix page aging (2.4.9-ac12) |
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On Thu, 20 Sep 2001 15:32:26 +0200 Daniel Phillips <phillips@bonn-fries.net> wrote:
> > Perhaps the following would be better, just in case anyone sets > > PAGE_AGE_DECL to something other than 1. > > > > static inline void age_page_down(struct page *page) > > { > > unsigned long age = page->age; > > if (age > PAGE_AGE_DECL) > > age -= PAGE_AGE_DECL; > > else > > age = 0; > > page->age = age; > > } > > > static inline void age_page_down(struct page *page) > { > page->age = max((int) (age - PAGE_AGE_DECL), 0); > } > > ;-)
Aehm, Daniel. Just for a hint of what I know about C:
IF age is unsigned long (like declared above) and PAGE_AGE_DECL is a define, then age-PAGE_AGE_DECL is of type unsigned long, which means it will not go below 0 but instead be huge positive, so your cast (int) before will not do any good, and you will not end up with 0 but somewhere above the clouds. So you just made Linus' max/min/cast point of view _very_ clear, I guess it was something like "people don't really think about using max/min and related problems".
;-))
I guess you meant:
page->age = max(((int)age - (int)PAGE_AGE_DECL),0);
Written without actually caring about the real definition of PAGE_AGE_DECL.
Regards, Stephan
PS: please anyone don't tell me what gnu c actually thinks about this, I don't care, I read K&R. And, of course, the whole thing is not worth discussing, it just hit me ...
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