[PATCH 005 of 16] knfsd: nfsd: oops exporting nonexistent directory

[NeilBrown <neilb@suse.de>]

Export a directory that does not exist:
	exportfs -orw,fsid=0,insecure,no_subtree_check client:/home/NFS4

Try to mount from client with nfs4. Mount hangs (I'm not sure why -
that's another issue).

While client is hung, back on server

	mkdir /home/NFS4

The server panics in dput. I traced the problem back to svc_export_parse()
calling path_release() even though path_lookup() failed (it happens
to fill in the nameidata structure with a negative dentry - so the test
after out: succeeds).

After patching, an recreating the problem, the client mount still takes
some time before finally exiting with a message "couldn't read
superblock".

Here is a simple patch to resolve this issue:

Signed-Off-By: Frank Filz <ffilzlnx@us.ibm.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Signed-off-by: Neil Brown <neilb@suse.de>

### Diffstat output
 ./fs/nfsd/export.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff ./fs/nfsd/export.c~current~ ./fs/nfsd/export.c
--- ./fs/nfsd/export.c~current~	2006-04-03 15:12:08.000000000 +1000
+++ ./fs/nfsd/export.c	2006-04-03 15:12:08.000000000 +1000
@@ -422,7 +422,7 @@ static int svc_export_parse(struct cache
 	if ((len=qword_get(&mesg, buf, PAGE_SIZE)) <= 0)
 		goto out;
 	err = path_lookup(buf, 0, &nd);
-	if (err) goto out;
+	if (err) goto out_no_path;
 
 	exp.h.flags = 0;
 	exp.ex_client = dom;
@@ -475,6 +475,7 @@ static int svc_export_parse(struct cache
  out:
 	if (nd.dentry)
 		path_release(&nd);
+ out_no_path:
 	if (dom)
 		auth_domain_put(dom);
 	kfree(buf);