Subject: Re: UBC problems
To: Steven M. Bellovin <>
From: Chuck Silvers <>
List: tech-kern
Date: 01/15/2005 07:47:34
On Sat, Jan 15, 2005 at 10:36:39AM -0500, Steven M. Bellovin wrote:
> In message <>, Chuck Silvers writes:
> >hi,
> >
> >
> >> -I now believe that the best way to deal with this would be to
> >>  have UBC reads just return zero filled pages if the file is
> >>  not backed with real data, and let upper layers (above the
> >>  trap handler) check whether the read is legal. Just commenting
> >>  out the range check in genfs_getpages() isn't enough,
> >>  unfortunately. That's a pretty complex matter...
> >
> >creating pages for offsets past EOF is to be avoided in general, since
> >it's pretty nonsensical.  I checked in a different fix for this issue,
> >update uvm_bio.c.
> >
> I don't understand -- are you trying to bar files with holes in them?  
> That's been part of Unix since the beginning.

no, seeking past EOF and write()ing still works.  we just don't want to
allow read operations for offsets past EOF.