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SubjectRe: knfsd and submounts
Hi Matthew.

>>>> Emulate Sun NFS daemon
>>>> CONFIG_NFSD_SUN
>>>> If you would like for the server to allow clients to access
>>>> directories that are mount points on the local filesystem
>>>> (this is how nfsd behaves on Sun systems), say yes here. If
>>>> unsure, say N.

>> Plainly, the CONFIG_NFSD_SUN does something other than what the
>> Configure.help says it does. I'm not sure what, but it *doesn't*
>> allow submounts to be viewed as part of the total exported
>> filesystem; only the physical partition is exported, and not any
>> of the other partitions mounted on the exported partition (I
>> know, we export directories, by for clarity's sake...)

> That isn't what the Configure.help entry claims to do though.
> Let me illustrate:

> On the server we have two filesystems, / and /usr. On the /
> filesystem, we have a /usr directory which has a file `foo' in
> it. But the /usr filesystem is mounted on top of the directory
> which contains foo, so on the server one sees the contents of
> the /usr filesystem, which does not include the file `foo'. The
> question is, when one exports /, does one get to see /usr/foo or
> not? And that is what CONFIG_NFSD_SUN decides. The only place
> this is mentioned is in fs/nfsd/vfs.c:

> #ifndef CONFIG_NFSD_SUN
> if (dentry->d_mounts != dentry) {
> return nfserr_perm;
> }
> #endif

> That is, the behavior with CONFIG_NFSD_SUN set to No is to check
> if this is a mountpoint and if it is, return a permission error.
> If CONFIG_NFSD_SUN is turned on, one can see `under' a mount
> point on the server.

I have to admit thaat I was under the saame misunderstanding
regaarding thaat option...

> Would someone care to knock up a better description for this
> config option and submit it as a patch to Linus? The current
> text is evidently confusing.

Perhaps I can suggest the enclosed patch - if you like it, you can
forward it to Linus...

Best wishes from Riley.

+----------------------------------------------------------------------+
| There is something frustrating about the quality and speed of Linux |
| development, ie., the quality is too high and the speed is too high, |
| in other words, I can implement this XXXX feature, but I bet someone |
| else has already done so and is just about to release their patch. |
+----------------------------------------------------------------------+
* ftp://ftp.MemAlpha.cx/pub/rhw/Linux
* http://www.MemAlpha.cx/kernel.versions.html
--- Configure.help~ Mon Jun 14 03:54:06 1999
+++ Configure.help Tue Jun 29 01:32:42 1999
@@ -7163,9 +7163,21 @@

Emulate Sun NFS daemon
CONFIG_NFSD_SUN
- If you would like for the server to allow clients to access
- directories that are mount points on the local filesystem (this is
- how nfsd behaves on Sun systems), say yes here. If unsure, say N.
+ If you say Y here, then when this system is used as an NFS server,
+ the behaviour of nfsd on Sun systems will be emulated. If you say
+ N here, then a cleaner (and potentially more secure) behavioural
+ style will be used. If unsure, say N.
+
+ To clarify the behaviour of Sun systems in this respect, imagine a
+ system where the /home/ftp partition has a subdirectory pub with a
+ file in it called pub/.message and where a second partition has
+ been munted over /home/ftp/pub and has thus hidden the pub/.message
+ file.
+
+ With the Sun systems behaviour, that hidden pub/.message file will
+ be visible to NFS clients that mount the /home/ftp partition from
+ your server, UNLESS they also mount the /home/ftp/pub partition on
+ top of it.

OS/2 HPFS filesystem support (read only)
CONFIG_HPFS_FS
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