[PATCH 6/7] nfsd: Map -ESTALE from case probe to NFS3ERR_STALE

[Chuck Lever <cel@kernel.org>]

From: Chuck Lever <chuck.lever@oracle.com>

The PATHCONF switch in nfsd3_proc_pathconf() recognizes -EOPNOTSUPP
(filesystem does not expose case state) and maps -EACCES / -EPERM to
nfserr_stale, but lets every other errno fall through to
nfserr_serverfault. -ESTALE escapes the same way even though RFC 1813
lists NFS3ERR_STALE as a permitted PATHCONF status, so a probe of an
NFS-backed re-export whose parent dentry has been invalidated returns
SERVERFAULT and tells the client the server is broken when the handle
itself simply went stale.

Add an explicit -ESTALE arm that maps to nfserr_stale.

Fixes: a8de9c3b40e4 ("nfsd: Report export case-folding via NFSv3 PATHCONF")
Reported-by: sashiko-bot <sashiko-bot@kernel.org>
Closes: https://sashiko.dev/#/patchset/20260507-case-sensitivity-v14-0-e62cc8200435@oracle.com?part=13
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 fs/nfsd/nfs3proc.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/nfsd/nfs3proc.c b/fs/nfsd/nfs3proc.c
index 12b9172c6be1..aeda7a802bdf 100644
--- a/fs/nfsd/nfs3proc.c
+++ b/fs/nfsd/nfs3proc.c
@@ -745,6 +745,9 @@ nfsd3_proc_pathconf(struct svc_rqst *rqstp)
 			 */
 			resp->status = nfserr_stale;
 			break;
+		case -ESTALE:
+			resp->status = nfserr_stale;
+			break;
 		default:
 			resp->status = nfserr_serverfault;
 			break;
-- 
2.54.0