pNFS: Always free the session slot on error in nfs4_layoutget_handle_exception

Right now, we can call nfs_commit_inode() while holding the session slot,
which could lead to NFSv4 deadlocks. Ensure we only keep the slot if
the server returned a layout that we have to process.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index ed45090..2c8c269 100644 (file)
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -8650,6 +8650,8 @@ nfs4_layoutget_handle_exception(struct rpc_task *task,
 
        dprintk("--> %s tk_status => %d\n", __func__, -task->tk_status);
 
+       nfs4_sequence_free_slot(&lgp->res.seq_res);
+
        switch (nfs4err) {
        case 0:
                goto out;
@@ -8714,7 +8716,6 @@ nfs4_layoutget_handle_exception(struct rpc_task *task,
                goto out;
        }
 
-       nfs4_sequence_free_slot(&lgp->res.seq_res);
        err = nfs4_handle_exception(server, nfs4err, exception);
        if (!status) {
                if (exception->retry)
@@ -8786,20 +8787,22 @@ nfs4_proc_layoutget(struct nfs4_layoutget *lgp, long *timeout)
        if (IS_ERR(task))
                return ERR_CAST(task);
        status = rpc_wait_for_completion_task(task);
-       if (status == 0) {
+       if (status != 0)
+               goto out;
+
+       /* if layoutp->len is 0, nfs4_layoutget_prepare called rpc_exit */
+       if (task->tk_status < 0 || lgp->res.layoutp->len == 0) {
                status = nfs4_layoutget_handle_exception(task, lgp, &exception);
                *timeout = exception.timeout;
-       }
-
+       } else
+               lseg = pnfs_layout_process(lgp);
+out:
        trace_nfs4_layoutget(lgp->args.ctx,
                        &lgp->args.range,
                        &lgp->res.range,
                        &lgp->res.stateid,
                        status);
 
-       /* if layoutp->len is 0, nfs4_layoutget_prepare called rpc_exit */
-       if (status == 0 && lgp->res.layoutp->len)
-               lseg = pnfs_layout_process(lgp);
        rpc_put_task(task);
        dprintk("<-- %s status=%d\n", __func__, status);
        if (status)