Re: Is there a "make hole" (truncate in middle) syscall?

From: Mike Fedyk
Date: Thu Dec 04 2003 - 21:04:31 EST

On Fri, Dec 05, 2003 at 01:42:13AM +0200, Szakacsits Szabolcs wrote:
> On Thu, 4 Dec 2003, Andy Isaacson wrote:
> > I'm curious -- does NTFS implement sparse files?
> Since Win2000 (NTFS 3.0+). Also many recently discussed features like
> file/directory/volume level compression/encryption, undelete, power of 2
> block sizes between 512-64kB, etc.

That gives us some possibilities for 2.7:
o undelete

Ext2 has undelete support, but that information is overwritten on unlink by
ext3, so ext3 won't work with the undelete utilities. How do the other
filesystems fare in this regard?

o per file compression

Ext2/3 has a flag for it, but support hasn't been implemented.

o per file encryption (can use a user space helper for policy)

Reiser4 plans to have a plugin that will support this.
What about the others?

o make hole support

And my personal favorite:
o pagecache coherent defrag (on live filesystems)

Andrew Morton wrote a patch for this a while back but since there were no
userspace utilities, and it was ext3 specific, it wasn't merged, and nothing
AFAIK has happened with it since.
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