[Pvfs2-developers] Re: setting xattrs on pvfs2 root

[Murali Vilayannur]

Sam,

> That's only on mount though, right?
On every getattr, sadly :(

>Could we remove the sticky bit
> while mounted so that extended attributes can be added?  The kernel
> doesn't check if xattrs already exist on a root dir when the file is
> mounted, does it?

hmm. we sorta rely on the sticky bit for 2 things,
- users cannot create files under directories owned by others
- users cannot delete files/directories owned by others.
So we cannot remove it since we got a lot of permission checks for free..
So in many ways we mimic'ed /tmp/
Anyways, the patch that I sent should take care of these issues.
We shall push the onus onto admins like robr said and it is not an
unusual request anyways.

>
> For the sticky bit thing -- could we set something on the server
> maintaining the root dir to specify whether to add the sticky bit
> when we mount?  The config file could have a sticky bit enable/
> disable option.

I think servers should not know about these issues like what we have today.
sticky bit is an in-memory thing for pvfs2. servers do not know about it at all.
anyways, I think we should move away from this sticky bit and let admins deal
with the fallout..
what do you think?
thanks,
Murali
>
> -sam
>
> > I will send out a patch to do this trick *if* folks are willing to
> > live with no top-level
> > files or dirs...
> > Murali
> >
> > On 6/28/07, Sam Lang <slang at mcs.anl.gov> wrote:
> >>
> >> Hi Murali,
> >>
> >> Can't we just have people remove the sticky bit so they can set
> >> xattrs?
> >>
> >> -sam
> >>
> >> On Jun 28, 2007, at 12:37 PM, Murali Vilayannur wrote:
> >>
> >> > Phil,
> >> > Umm.. The problem is that we mark the root directory as sticky
> >> so that
> >> > users can create files/directories at the top level instead of
> >> having
> >> > admins create directories owned by a user under top level. The
> >> kernel
> >> > does not allow setxattr on inodes marked sticky..
> >> >
> >> > if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) {
> >> >                if (!S_ISREG(inode->i_mode) &&
> >> >                    (!S_ISDIR(inode->i_mode) || inode->i_mode &
> >> > S_ISVTX)) <--
> >> >                        return -EPERM;
> >> >        }
> >> > Thats why we don't even have a chance to subvirt those checks..
> >> > What do you guys suggest? Shall we step back and make the root
> >> > directory non-sticky by default? That way admins will need to
> >> > explicitly create user directories etc and chown them.
> >> > I think a rerun of ltp may also be required if we do this change.
> >> > comments?
> >> > Murali
> >> >
> >> > On 6/28/07, Phil Carns <pcarns at wastedcycles.org> wrote:
> >> >> This is with 2.6 (both very recent and relatively old
> >> version).  Many
> >> >> thanks for looking at it.
> >> >>
> >> >> -Phil
> >> >>
> >> >> Murali Vilayannur wrote:
> >> >> > hi Phil,
> >> >> > Are you using 2.4. kernel versions? or 2.6?
> >> >> > If xattrs dont work, ACLs also won't work.
> >> >> > I will dig into this and let you know what I find out..
> >> >> > thanks,
> >> >> > Murali
> >> >> >
> >> >> > On 6/28/07, Phil Carns <pcarns at wastedcycles.org> wrote:
> >> >> >> I am interested in this because it would be nice to be able
> >> to set
> >> >> >> tuning options at the root directory level without modifying
> >> >> the server
> >> >> >> side configuration files.  I also wonder if this issue would
> >> cause
> >> >> >> problems for ACLs on the root directory.
> >> >> >>
> >> >> >> -Phil
> >> >> >>
> >> >> >> Murali Vilayannur wrote:
> >> >> >> > Hey Phil,
> >> >> >> > Sorry I forgot to get back to you on this..
> >> >> >> > No I don't think this would work.
> >> >> >> > It is a kernel module issue that I hadnt tracked down fully..
> >> >> >> > Do you need this feature?
> >> >> >> > thanks,
> >> >> >> > Murali
> >> >> >> >
> >> >> >> > On 6/27/07, Phil Carns <pcarns at wastedcycles.org> wrote:
> >> >> >> >> Just pinging on this one again- has any one else bumped into
> >> >> this
> >> >> >> >> problem?
> >> >> >> >>
> >> >> >> >> -Phil
> >> >> >> >>
> >> >> >> >> Phil Carns wrote:
> >> >> >> >> > It looks like pvfs2 does not allow you to set xattrs on
> >> >> the root
> >> >> >> >> > directory.  Is this expected?
> >> >> >> >> >
> >> >> >> >> > # checking the mount options:
> >> >> >> >> >
> >> >> >> >> >  > mount -t pvfs2
> >> >> >> >> > tcp://localhost:3334/pvfs2-fs on /mnt/pvfs2 type pvfs2
> >> >> >> (rw,user_xattr)
> >> >> >> >> >
> >> >> >> >> > # confirming that xattrs can be set on a normal directory:
> >> >> >> >> >
> >> >> >> >> >  > setfattr -n user.pvfs2.num_dfiles -v "1" /mnt/pvfs2/
> >> dir1
> >> >> >> >> >  > getfattr -n user.pvfs2.num_dfiles /mnt/pvfs2/dir1
> >> >> >> >> > getfattr: Removing leading '/' from absolute path names
> >> >> >> >> > # file: mnt/pvfs2/dir1
> >> >> >> >> > user.pvfs2.num_dfiles="1"
> >> >> >> >> >
> >> >> >> >> > # trying to set xattrs on the root directory:
> >> >> >> >> >
> >> >> >> >> >  > setfattr -n user.pvfs2.num_dfiles -v "1" /mnt/pvfs2
> >> >> >> >> > setfattr: /mnt/pvfs2: Operation not permitted
> >> >> >> >> >  > getfattr -n user.pvfs2.num_dfiles /mnt/pvfs2
> >> >> >> >> > /mnt/pvfs2: user.pvfs2.num_dfiles: No such attribute
> >> >> >> >> >
> >> >> >> >> > All of the above is run as root.  I don't think it is
> >> >> anything
> >> >> >> special
> >> >> >> >> > about the num_dfiles attribute either; it looks like I
> >> >> can't set any
> >> >> >> >> > xattrs on the root directory.  It always responds with
> >> >> "Operation
> >> >> >> not
> >> >> >> >> > permitted".
> >> >> >> >> >
> >> >> >> >> > -Phil
> >> >> >> >> >
> >> >> >> >>
> >> >> >> >> _______________________________________________
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> >> >> developers
> >> >> >> >>
> >> >> >>
> >> >> >>
> >> >>
> >> >>
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