[vdr] Patch to avoid file system buffer trashing

[Ralf Müller]

Carsten Koch wrote:

> I tried your patch today and watched the available memory (using top)
> when replaying. The number stayed the same. Excellent!

Thanks a lot.

> However, when I did FF or FR, the number decreased.
> Ralf, can you reproduce the problem?

With FF there are no decreases here - but with FR. I didn't notice that 
before (why ever). But I'm happy you found that. When jumping backward I 
missed to clear the read ahead buffer. Interestingly it doesn't help to 
clear that buffer - it may have to do with the man page description for 
POSIX_FADV_WILLNEED: "start a non blocking read". It seems this read may 
or may not be finished when I try to say that I don't need the 
previously asked read ahead buffer anymore. So as a work around I 
dropped the POSIX_FADV_WILLNEED call. This also helped for the noad patch.

I will try to release a new patch today in the afternoon/evening.

Regards
Ralf