[PATCH] NFSv4: deal with v4.0 servers that request confirmation on reclaim-type opens

[Scott Mayhew <smayhew@redhat.com>]

There are some NFS v4.0 servers that request confirmation on
reclaim-type opens even though it is disallowed by RFC 7530.

The Linux NFS client used to cope with those okay due to
1) nfs4_opendata_alloc() setting the filehandle in the args for the
OPEN_CONFIRM to point to the filehandle in the OPEN results, and
2) nfs4_open_prepare() copying the filehandle from the OPEN args to the
OPEN results when doing an open by filehandle

The latter part was removed by commit 4e2fcac77390 ("nfsv4: Use correct
inode in _nfs4_opendata_to_nfs4_state()")... and since there's no GETFH
in the OPEN compound when doing a reclaim-type open, if one of these
servers does request confirmation we wind up sending a zero filehandle
in the PUTFH of the OPEN_CONFIRM compound and the OPEN_CONFIRM fails
with NFS4ERR_BADHANDLE, causing the reclaim to fail.

Add the copying of the filehandle back to nfs4_open_prepare() and
log a warning in the event that the client does get a reply to
OPEN(CLAIM_PREVIOUS) that has NFS4_OPEN_RESULT_CONFIRM set.

Signed-off-by: Scott Mayhew <smayhew@redhat.com>
---
 fs/nfs/nfs4proc.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 867457d6dfbe..5e521a506da3 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -2323,6 +2323,7 @@ static void nfs4_open_prepare(struct rpc_task *task, void *calldata)
 		/* Fall through */
 	case NFS4_OPEN_CLAIM_FH:
 		task->tk_msg.rpc_proc = &nfs4_procedures[NFSPROC4_CLNT_OPEN_NOATTR];
+		nfs_copy_fh(&data->o_res.fh, data->o_arg.fh);
 	}
 	data->timestamp = jiffies;
 	if (nfs4_setup_sequence(data->o_arg.server->nfs_client,
@@ -2470,8 +2471,14 @@ static int _nfs4_recover_proc_open(struct nfs4_opendata *data)
 
 	nfs_fattr_map_and_free_names(NFS_SERVER(dir), &data->f_attr);
 
-	if (o_res->rflags & NFS4_OPEN_RESULT_CONFIRM)
+	if (o_res->rflags & NFS4_OPEN_RESULT_CONFIRM) {
+		if (data->o_arg.claim == NFS4_OPEN_CLAIM_PREVIOUS)
+			pr_err_ratelimited("NFS: Broken NFSv4 server %s is "
+					"requesting open confirmation for "
+					"OPEN(CLAIM_PREVIOUS)\n",
+					NFS_SERVER(dir)->nfs_client->cl_hostname);
 		status = _nfs4_proc_open_confirm(data);
+	}
 
 	return status;
 }
-- 
2.17.1