Linux-kernel mailing list archive 1998-31,: Re: page_alloc strange mask += mask

# Re: page_alloc strange mask += mask

Linus Torvalds (torvalds@transmeta.com)
Mon, 3 Aug 1998 10:30:12 -0700 (PDT)

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On Mon, 3 Aug 1998, Andrea Arcangeli wrote:
>
> Continuing my trail in the mm internals I didn' t understood this point
> (and a lot of other things of course ;-). Using mask += mask some low bits
> got lost by the mask. Was that intentional?

It was very much intentional. The mask should go like

11111111111111111111000000000000
11111111111111111110000000000000
11111111111111111100000000000000
....

and your patch makes it

11111111111111111111000000000000
11111111111111111110000000000001
11111111111111111100000000000011
...

which probably happens to work because the low bits aren't really
significant as they have been masked out by the earlier passes, but it's
not correct.

Linus

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