2002-08-06 15:46:16

by Florian Weimer

[permalink] [raw]
Subject: Problems with NFS exports

I'm seeing weired errors with nfsctl():

This works:

nfsservctl(NFSCTL_EXPORT, "deneb.enyo.de", "/mnt/storage/2/backup/deneb/tmp", makedev(3, 66), ino 167772288, uid 65534, gid 65534) = 0

But a subsequent call fails:

nfsservctl(NFSCTL_EXPORT, "deneb.enyo.de", "/mnt/storage/2/backup/deneb", makedev(3, 66), ino 150995072, uid 65534, gid 65534) = -1 EINVAL (Invalid argument)

I don't understand what makes the difference (the inode values are
correct). This is kernel 2.4.18 with XFS support, and the directory
resides on an XFS file system.

Any ideas?


2002-08-07 09:21:55

by Florian Weimer

[permalink] [raw]
Subject: Re: Problems with NFS exports

Florian Weimer <[email protected]> writes:

> I'm seeing weired errors with nfsctl():
>
> This works:
>
> nfsservctl(NFSCTL_EXPORT, "deneb.enyo.de", "/mnt/storage/2/backup/deneb/tmp", makedev(3, 66), ino 167772288, uid 65534, gid 65534) = 0
>
> But a subsequent call fails:
>
> nfsservctl(NFSCTL_EXPORT, "deneb.enyo.de", "/mnt/storage/2/backup/deneb", makedev(3, 66), ino 150995072, uid 65534, gid 65534) = -1 EINVAL (Invalid argument)
>
> I don't understand what makes the difference (the inode values are
> correct). This is kernel 2.4.18 with XFS support, and the directory
> resides on an XFS file system.
>
> Any ideas?

(Full quote because of additional recipeint.)

It appears that a directory tree can only be exported once. Is this
intentional? If yes, the following patch should be applied (to
linux/fs/nfsd/export.c), so that the return value is more meaningful:

--- export.c 2002/08/07 09:22:11 1.1
+++ export.c 2002/08/07 09:22:28
@@ -219,6 +219,7 @@
goto finish;
}

+ err = -EBUSY;
if ((parent = exp_child(clp, dev, nd.dentry)) != NULL) {
dprintk("exp_export: export not valid (Rule 3).\n");
goto finish;


After this change, the userspace tools can issue are more meaningful
error message for this case.

2002-08-07 10:36:14

by NeilBrown

[permalink] [raw]
Subject: Re: Problems with NFS exports

On Wednesday August 7, [email protected] wrote:
> Florian Weimer <[email protected]> writes:
>
> > I'm seeing weired errors with nfsctl():
> >
> > This works:
> >
> > nfsservctl(NFSCTL_EXPORT, "deneb.enyo.de", "/mnt/storage/2/backup/deneb/tmp", makedev(3, 66), ino 167772288, uid 65534, gid 65534) = 0
> >
> > But a subsequent call fails:
> >
> > nfsservctl(NFSCTL_EXPORT, "deneb.enyo.de", "/mnt/storage/2/backup/deneb", makedev(3, 66), ino 150995072, uid 65534, gid 65534) = -1 EINVAL (Invalid argument)
> >
> > I don't understand what makes the difference (the inode values are
> > correct). This is kernel 2.4.18 with XFS support, and the directory
> > resides on an XFS file system.
> >
> > Any ideas?
>
> (Full quote because of additional recipeint.)
>
> It appears that a directory tree can only be exported once. Is this
> intentional? If yes, the following patch should be applied (to
> linux/fs/nfsd/export.c), so that the return value is more meaningful:

Probably better documentation in exports.5 would be just as useful.
And "BUSY" probably isn't correct ....
The rule is that you cannot export a directory and an ancestor of that
directory in the same filesystem.
/a/1 and /a/2 can both be exported, but not /a and /a/1.

Reason: exporting "/a" means exporting that directoring and all
descendants of it in the same filesystem.
If you export /a with different flags than /a/1 it is ambiguous.

And personally, I doubt that there are very many situations where it
makes sense.

It would be possible to dis-ambiguate the ambiguity but it wouldn't be
very clean, and I really am not sure that it is worth the effort.

NeilBrown


>
> --- export.c 2002/08/07 09:22:11 1.1
> +++ export.c 2002/08/07 09:22:28
> @@ -219,6 +219,7 @@
> goto finish;
> }
>
> + err = -EBUSY;
> if ((parent = exp_child(clp, dev, nd.dentry)) != NULL) {
> dprintk("exp_export: export not valid (Rule 3).\n");
> goto finish;
>
>
> After this change, the userspace tools can issue are more meaningful
> error message for this case.
> -
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2002-08-07 11:10:05

by Florian Weimer

[permalink] [raw]
Subject: Re: Problems with NFS exports

Neil Brown <[email protected]> writes:

> Probably better documentation in exports.5 would be just as useful.

Maybe.

BTW, is it possible to export a directory tree under a different path,
using the kernel NFS daemon?

> And "BUSY" probably isn't correct ....

Why not? The ressource (the directory tree) is already being used, and
therefore the export fails.

> It would be possible to dis-ambiguate the ambiguity but it wouldn't be
> very clean, and I really am not sure that it is worth the effort.

Better error messages are always a good idea. :-)

2002-08-07 11:14:12

by NeilBrown

[permalink] [raw]
Subject: Re: Problems with NFS exports

On Wednesday August 7, [email protected] wrote:
> Neil Brown <[email protected]> writes:
>
> > Probably better documentation in exports.5 would be just as useful.
>
> Maybe.
>
> BTW, is it possible to export a directory tree under a different path,
> using the kernel NFS daemon?

Uhm... symlinks work.
Which is to say, the client can mount using a 'different path', though
they can also mount using the 'true' path.



>
> > And "BUSY" probably isn't correct ....
>
> Why not? The ressource (the directory tree) is already being used, and
> therefore the export fails.

I guess... I just feel it isn't really clear what it is that is
'busy'.

NeilBrown


>
> > It would be possible to dis-ambiguate the ambiguity but it wouldn't be
> > very clean, and I really am not sure that it is worth the effort.
>
> Better error messages are always a good idea. :-)

Can't disagree there.

NeilBrown

2002-08-07 11:47:47

by Florian Weimer

[permalink] [raw]
Subject: Re: Problems with NFS exports

Neil Brown <[email protected]> writes:

>> > And "BUSY" probably isn't correct ....
>>
>> Why not? The ressource (the directory tree) is already being used, and
>> therefore the export fails.
>
> I guess... I just feel it isn't really clear what it is that is
> 'busy'.

And it implies that it is just a temporary error condition, not a
configuration issue.

Maybe EEXIST is better?