Messages in this thread | | | Subject | Re: [PATCH] bitmap: Support for pages > BITS_PER_LONG. | From | James Bottomley <> | Date | Thu, 19 Jan 2006 21:28:30 -0600 |
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On Wed, 2006-01-18 at 19:11 -0800, Paul Jackson wrote: > Could you look Mundt's patch, and see if it looks ok?
Not being on lkml, this was harder than it sounds, but I eventually found the actual patch on marc. However, no, it doesn't look right.
This:
> + /* find space in the bitmap */ > + for (j = 0; j < span; j++) > + if ((bitmap[index + j] & (mask << offset))) {
Is wrong. You're looking for an unset span of order bits at a given offset. So you get the byte offset for the first, then all the following bitmap[n] need to be zero until you need to do an offset in reverse for the last bit. i.e. (assuming BITS_PER_LONG=32) for a span of 126 at offset 1, you check
bitmap[0] & 0xfffffffe == 0 bitmap[1] & 0xffffffff == 0 bitmap[2] & 0xffffffff == 0 bitmap[3] & 0x7fffffff == 0
and so on.
> + space = 0; > + break; > + } > + > + /* keep looking */ > + if (unlikely(!space)) > + continue; > + > + for (j = 0; j < span; j++) > + /* set region in bitmap */ > + bitmap[index + j] |= (mask << offset);
Likewise, you'd have to or in what you checked above.
James
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