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SubjectRe: [PATCH] netfilter: replace horrible hack with ksize()
On Thu, 6 Mar 2008, Pekka J Enberg wrote:
> > > - if (newlen >= ct->ext->real_len) {
> > > + if (newlen >= ksize(ct->ext)) {
> >
> > This needs to look at the currently allocated size, otherwise
> > it will always realloc when adding new extensions after having
> > used up ksize(ct->ext) space.
>
> Lets say you
>
> p = kmalloc(8, ...);
>
> Then ksize(p) will return the currently allocated size which is 32 bytes
> when page size is 4 KB, and not 8 bytes. So it should be equivalent of
> what the current code does.
>
> What am I missing here?

Ok, it's not equivalent. We have two sizes: object size (8 bytes) and
buffer size (32 bytes) here. In netfilter, ->real_len is same as object
size, not buffer size as ksize() is.

But now I am officially even more confused, why does the netfilter code
decided whether to reallocate based on _object size_ and not _buffer size_
(as krealloc() does, for example)?

Pekka


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