Re: RESVSP problems

David Chinner
2007-05-08T00:59:41Z

On Mon, May 07, 2007 at 08:58:32PM +0200, Å?ukasz Fibinger wrote:
> On Monday 07 of May 2007, you wrote:
> > You've probably hit:
> > http://oss.sgi.com/bugzilla/show_bug.cgi?id=418
> > unwritten extents remain unwritten after mmap() modifies them
> >
> > Bug dchinner about it... ;-)
>
> Dave, consider it a bugging from my humble self :-)

Yeah, yeah ;)

I'm waiting to see what happens with Nick's patches in .22 before
going any further. If they are not merged into .22, then I think we
should push the XFS specific fix in....

> > yeah... ISTR that the arguments are funky. I can't remember if it's a
> > bug or not. :) FWIW, allocsp just writes zeros to the file, so you
> > could do it just as well from userspace w/ no fancy ioctls... ALLOCSP
> > is a bit pointless if you ask me... though maybe someone knows why it's
> > there :)
>
> Let me say that I have noticed that using ALLOCSP seems to create less extents
> than posix_fallocate/manual zeroing.

Yes, that's likely ;)

There's work currently active to make posix_fallocate() do the same thing
as ALLOCSP (i.e. call into the filesystem and let it do smart stuff), but
that's a ways off yet...

Cheers,

Dave.
--
Dave Chinner
Principal Engineer
SGI Australian Software Group