Re: Mass-Hardlinking Oops

Claudio Martins
2009-10-13T00:31:25Z

On Monday 12 October 2009, Chris Mason wrote:
> On Mon, Oct 12, 2009 at 02:17:11PM -0400, jim owens wrote:
> > John Dong wrote:
> > >I don't think that's a good counterargument for why this is not a =
bug.
> >
> > it is not a "bug". hard links are not a required feature of all
> > filesystems nor is a defined large number required for those with
> > hard links.
> >
> > >Can't think of any off the top of my head for Linux, but
> > >definitely in OS X Time Machine can easily create 200+ hardlinks.
> >
> > so 311 is 50% than the app uses... plenty of growth.
>
> Just to clarify again, the max link count on btrfs is 2^32. The lowe=
r
> limit is only in place on links to the same file in the same director=
y.
>

Hi Chris and all,

I've made a quick test and managed to create many more links to the sa=
me file=20
in the *same* directory on other filsystems:=20

XFS can do at least 100000, probably more;=20
Reiserfs did 64535;
ext3 managed to do 32000;
ext4 did 65000.

While I agree it might be a bit stupid to create so many hardlinks to =
the=20
same file on the same directory, this issue can be seen as one of "back=
ward=20
compatibility" with other widely used and established Linux filesystems=
=2E=20

Despite it being stupid or not, the fact is that I've seen some crazy s=
tuff=20
along the years working with Unix, so people will expect this kind of t=
hings=20
to *not* break when they switch from their old filesystems to shiny new=
=20
btrfs.

The fact being that this limit is way lower than on other filesystems =
(we're=20
talking 2 orders of magnitude, at best!), I too suggest that the limit =
should=20
be increased. Not being critical, it might be done when some other feat=
ures=20
require a format change but, nonetheless, should be done for the sake o=
f=20
avoiding breakage on existing systems.

Best regards, and thanks for your hard work.

Cl=C3=A1udio

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