Re: get_order() broken !

[David Howells]

Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:

> Yeah, I think the recent get_order() changes to change it to use ilog2() 
> are just crap. I actually looked at it when it went in, but I assumed that 
> it had been tested. I don't think it has.

It had, it's just that the testing totally failed to show up the problem; that
and I think my userspace testing went wrong because I made the wrong
assumptions about what the answer should be.

However, having discussed it with Ben, HPA and David Woodhouse and others I've
come up with a patch (sent separately) that should fix it by using:

	ilog2((n) - 1) + 1 

as the basis for the calculation as this should round up the result.  I've
encapsulated this as a function called ilog2_up() and fixed the docs to make
it cleared how ilog2() and co actually work.

David
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