[PATCH 4.14 050/217] pNFS: Always free the session slot on error in nfs4_layoutget_handle_exception

Greg Kroah-Hartman
2018-08-23T08:22:18Z

From: Trond Myklebust <trond.myklebust@hammerspace.com>

[ Upstream commit 2dbf8dffbf35fd8f611083b9d9fe74fdccf912a3 ]

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>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/nfs/nfs4proc.c | 17 ++++++++++-------
1 file changed, 10 insertions(+), 7 deletions(-)

--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -8429,6 +8429,8 @@ nfs4_layoutget_handle_exception(struct r

dprintk("--> %s tk_status => %d\n", __func__, -task->tk_status);

+ nfs4_sequence_free_slot(&lgp->res.seq_res);
+
switch (nfs4err) {
case 0:
goto out;
@@ -8493,7 +8495,6 @@ nfs4_layoutget_handle_exception(struct r
goto out;
}

- nfs4_sequence_free_slot(&lgp->res.seq_res);
err = nfs4_handle_exception(server, nfs4err, exception);
if (!status) {
if (exception->retry)
@@ -8619,20 +8620,22 @@ nfs4_proc_layoutget(struct nfs4_layoutge
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)