panic on 4.20 server exporting xfs filesystem

[Christoph Hellwig]

On Wed, Mar 04, 2015 at 11:08:49PM -0500, J. Bruce Fields wrote:
> Ah-hah:
> 
> 	static void
> 	nfsd4_cb_layout_fail(struct nfs4_layout_stateid *ls)
> 	{
> 		...
> 		nfsd4_cb_layout_fail(ls);
> 
> That'd do it!
> 
> Haven't tried to figure out why exactly that's getting called, and why
> only rarely.  Some intermittent problem with the callback path, I guess.
> 
> Anyway, I think that solves most of the mystery....

Ooops, that was a nasty git merge error in the last rebase, see the fix
below.  But I really wonder if we need to make the usage of pnfs explicit
after all, othterwise we'll always hand out layouts on any XFS-exported
filesystems, which can't be used and will eventually need to be recalled.

---
>From ad592590cce9f7441c3cd21d030f3a986d8759d7 Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <hch at lst.de>
Date: Thu, 5 Mar 2015 06:12:29 -0700
Subject: nfsd: don't recursively call nfsd4_cb_layout_fail

Due to a merge error when creating c5c707f9 ("nfsd: implement pNFS
layout recalls"), we recursivelt call nfsd4_cb_layout_fail from itself,
leading to stack overflows.

Signed-off-by: Christoph Hellwig <hch at lst.de>
---
 fs/nfsd/nfs4layouts.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/fs/nfsd/nfs4layouts.c b/fs/nfsd/nfs4layouts.c
index 3c1bfa1..1028a06 100644
--- a/fs/nfsd/nfs4layouts.c
+++ b/fs/nfsd/nfs4layouts.c
@@ -587,8 +587,6 @@ nfsd4_cb_layout_fail(struct nfs4_layout_stateid *ls)
 
 	rpc_ntop((struct sockaddr *)&clp->cl_addr, addr_str, sizeof(addr_str));
 
-	nfsd4_cb_layout_fail(ls);
-
 	printk(KERN_WARNING
 		"nfsd: client %s failed to respond to layout recall. "
 		"  Fencing..\n", addr_str);
-- 
1.9.1