NFSv4: Fix a hang in OPEN related to server reboot

commit 56e0d71ef12f026d96213e45a662bde6bbff4676 upstream.

If the server fails to return the attributes as part of an OPEN
reply, and then reboots, we can end up hanging. The reason is that
the client attempts to send a GETATTR in order to pick up the
missing OPEN call, but fails to release the slot first, causing
reboot recovery to deadlock.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Fixes: 2e80dbe7ac51a ("NFSv4.1: Close callback races for OPEN, LAYOUTGET...")
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 201ca3f2c4bac14986220fcdf6a6c37b734ffa96..8ba6c0d4d499a10f8097c0551fdda40f2b22f705 100644 (file)
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -2300,8 +2300,10 @@ static int _nfs4_proc_open(struct nfs4_opendata *data)
                if (status != 0)
                        return status;
        }
-       if (!(o_res->f_attr->valid & NFS_ATTR_FATTR))
+       if (!(o_res->f_attr->valid & NFS_ATTR_FATTR)) {
+               nfs4_sequence_free_slot(&o_res->seq_res);
                nfs4_proc_getattr(server, &o_res->fh, o_res->f_attr, o_res->f_label);
+       }
        return 0;
 }