Re: Review of Thomas's >2GB ext2fs proposal

[Thomas Bushnell BSG]

"Neal H. Walfield" <neal@cs.uml.edu> writes:

> It is not a memory leak as it can still be reclaim.  It will be
> reclaimed (because it has no references) when the mapping cache is
> full.  Or, and perhaps this is a better approach, we add a check in
> the release function to see if the kernel has a copy and if not, drop
> it at that point.
>
> > (I think the solution is to have a proper interlock when you drop the
> > last reference, but this is very tricky to get right.)
> 
> I am not sure what you envision here.

What I envision is a check when you release the last reference to drop
it if the kernel doesn't have a copy.  I meant to say that such things
can be tricky, whether it is depends on the details and what locking
structure you have.

What happens if the mapping cache never fills because the kernel
always pages things out in time?  The problem here is that you still
have the data around taking up a real memory page; the kernel
requested a pageout and you haven't freed the page.