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SubjectRe: PATCH] fbmem.c, kernel 2.3.25


On Wed, 3 Nov 1999, Arjan van de Ven wrote:

> In article <Pine.GSO.4.10.9911030310570.320-100000@weyl.math.psu.edu> you wrote:
>
> > <flame>
> > Gentlemen, could we _stop_ this "I don't understand what I've done, but
> > compiler is happy now" sort of patches? Trivial check would show that
> > vm_pgoff is not in bytes, it's in pages (AFAICS it's a part of LFS patch).
> > Result of this voodoo debugging is the code that passes compiler without
> > warnings but is badly broken. If you don't understand what happens - take
> > time to figure it out. Sheesh... Shutting the compiler up != fixing. It
> > hides the problem and makes it very hard to fix - I've seen similar beasts
> > that stayed around for 3-4 years.
> > </flame>
>
> Ok. Maybe the person who knows he's breaking a _lot_ of interfaces, should
> take the trouble of sending a mail to l-k explaining what he/she has done,
> and what a good fix would look like. (*)
>
> Greetings,
> Arjan van de Ven
>
>
> (*) This is not always possible, for example the VFS changes in early 2.3
> are such a case.

Might be a good idea. Ask the author - it's not mine ;-) Looks like a part
of LFS stuff, so may be it's Matti. As for the fix... Well, it appeared in
25-pre1 and grep in patch gives:
- unsigned long vm_offset;
+ unsigned long vm_pgoff; /* offset in PAGE_SIZE units, *not* PAGE_CACHE_SIZE */
Methink the rest is obvious. Quick look at the patch confirms that we have
switched from offsets in bytes to offsets in pages. Especially if you look
at the place where the thing is set - replacement of
...
vma->vm_offset = off;
with
...
off >= PAGE_SHIFT;
...
vma->vm_pgoff = off;
speaks for itself.


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