From: Zhang Xiaoxu zhangxiaoxu5@huawei.com
commit 5483b904bf336948826594610af4c9bbb0d9e3aa upstream.
When find a task from wait queue to wake up, a non-privileged task may be found out, rather than the privileged. This maybe lead a deadlock same as commit dfe1fe75e00e ("NFSv4: Fix deadlock between nfs4_evict_inode() and nfs4_opendata_get_inode()"):
Privileged delegreturn task is queued to privileged list because all the slots are assigned. If there has no enough slot to wake up the non-privileged batch tasks(session less than 8 slot), then the privileged delegreturn task maybe lost waked up because the found out task can't get slot since the session is on draining.
So we should treate the privileged task as the emergency task, and execute it as for as we can.
Reported-by: Hulk Robot hulkci@huawei.com Fixes: 5fcdfacc01f3 ("NFSv4: Return delegations synchronously in evict_inode") Cc: stable@vger.kernel.org Signed-off-by: Zhang Xiaoxu zhangxiaoxu5@huawei.com Signed-off-by: Trond Myklebust trond.myklebust@hammerspace.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- net/sunrpc/sched.c | 9 +++++++++ 1 file changed, 9 insertions(+)
--- a/net/sunrpc/sched.c +++ b/net/sunrpc/sched.c @@ -614,6 +614,15 @@ static struct rpc_task *__rpc_find_next_ struct rpc_task *task;
/* + * Service the privileged queue. + */ + q = &queue->tasks[RPC_NR_PRIORITY - 1]; + if (queue->maxpriority > RPC_PRIORITY_PRIVILEGED && !list_empty(q)) { + task = list_first_entry(q, struct rpc_task, u.tk_wait.list); + goto out; + } + + /* * Service a batch of tasks from a single owner. */ q = &queue->tasks[queue->priority];