Subject: Re: UBC problems
To: Steven M. Bellovin <firstname.lastname@example.org>
From: Chuck Silvers <email@example.com>
Date: 01/15/2005 07:47:34
On Sat, Jan 15, 2005 at 10:36:39AM -0500, Steven M. Bellovin wrote:
> In message <20050115151907.GA9021@spathi.chuq.com>, Chuck Silvers writes:
> >> -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.