[Samba] acl_xattr vs acl_tdb

simo idra at samba.org
Fri Mar 26 10:51:07 MDT 2010


On Fri, 2010-03-26 at 09:43 -0700, Jeremy Allison wrote:
> On Fri, Mar 26, 2010 at 12:40:49PM -0400, simo wrote:
> > On Fri, 2010-03-26 at 12:28 -0400, simo wrote:
> > > On Fri, 2010-03-26 at 10:53 -0400, simo wrote:
> > > > On Fri, 2010-03-26 at 13:06 +0000, Miguel Medalha wrote:
> > > > > > If I remember correctly XFS used to have a size limit of 64KiB per
> > > > > > xattr.
> > > > > >    
> > > > > 
> > > > > What about ext3 & ext4?
> > > > 
> > > > Always IIRC, they should be limited by the inode size, which is 4KiB,
> > > > but this information is old, and should be verified for ext4.
> > > 
> > > Ok I just checked.
> > > On ext4 the total size of *all* xattrs can't be larger than 4k and some.
> > > 
> > > There is only 1 block you can allocate beyond the file inode.
> > > 
> > > So careful on the amount of data you store in ext4 attrs. If you think
> > > you'll have fatty Windows ACLs to store I guess XFS is a better choice
> > > right now.
> > 
> > Ah just to add insult to injury, remember that the xattr space is shared
> > with selinux labels *and* posix ACLs contents.
> > 
> > So it is a tight spot indeed.
> 
> And don't forget the DOS attributes as well :-).

pesky dos attributes :-)

and yes if you think it is too tight a space it is time to open RFE bugs
in your favorite upstream distribution to ask ext4 developers to please
add more space.

It is possible, although it may hurt performance on big xattrs I think
it is better to loose some in perf. than not being able to save an
ACL ...

Simo.

-- 
Simo Sorce
Samba Team GPL Compliance Officer <simo at samba.org>
Principal Software Engineer at Red Hat, Inc. <simo at redhat.com>



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