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Re: RESVSP problems

To: Å?ukasz Fibinger <lucke@xxxxx>
Subject: Re: RESVSP problems
From: David Chinner <dgc@xxxxxxx>
Date: Tue, 8 May 2007 10:59:23 +1000
Cc: Eric Sandeen <sandeen@xxxxxxxxxxx>, xfs@xxxxxxxxxxx
In-reply-to: <200705072058.32679.lucke@xxxxx>
References: <200705072004.22848.lucke@xxxxx> <463F7368.8090101@xxxxxxxxxxx> <200705072058.32679.lucke@xxxxx>
Sender: xfs-bounce@xxxxxxxxxxx
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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


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