[PATCH 5.10 266/717] SUNRPC: rpc_wake_up() should wake up tasks in the correct order

Greg Kroah-Hartman
2020-12-28T15:03:53Z

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

[ Upstream commit e4c72201b6ec3173dfe13fa2e2335a3ad78d4921 ]

Currently, we wake up the tasks by priority queue ordering, which means
that we ignore the batching that is supposed to help with QoS issues.

Fixes: c049f8ea9a0d ("SUNRPC: Remove the bh-safe lock requirement on the rpc_wait_queue->lock")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/sunrpc/sched.c | 65 +++++++++++++++++++++++++---------------------
1 file changed, 35 insertions(+), 30 deletions(-)

diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c
index f06d7c315017c..cf702a5f7fe5d 100644
--- a/net/sunrpc/sched.c
+++ b/net/sunrpc/sched.c
@@ -675,6 +675,23 @@ struct rpc_task *rpc_wake_up_next(struct rpc_wait_queue *queue)
}
EXPORT_SYMBOL_GPL(rpc_wake_up_next);

+/**
+ * rpc_wake_up_locked - wake up all rpc_tasks
+ * @queue: rpc_wait_queue on which the tasks are sleeping
+ *
+ */
+static void rpc_wake_up_locked(struct rpc_wait_queue *queue)
+{
+ struct rpc_task *task;
+
+ for (;;) {
+ task = __rpc_find_next_queued(queue);
+ if (task == NULL)
+ break;
+ rpc_wake_up_task_queue_locked(queue, task);
+ }
+}
+
/**
* rpc_wake_up - wake up all rpc_tasks
* @queue: rpc_wait_queue on which the tasks are sleeping
@@ -683,25 +700,28 @@ EXPORT_SYMBOL_GPL(rpc_wake_up_next);
*/
void rpc_wake_up(struct rpc_wait_queue *queue)
{
- struct list_head *head;
-
spin_lock(&queue->lock);
- head = &queue->tasks[queue->maxpriority];
+ rpc_wake_up_locked(queue);
+ spin_unlock(&queue->lock);
+}
+EXPORT_SYMBOL_GPL(rpc_wake_up);
+
+/**
+ * rpc_wake_up_status_locked - wake up all rpc_tasks and set their status value.
+ * @queue: rpc_wait_queue on which the tasks are sleeping
+ * @status: status value to set
+ */
+static void rpc_wake_up_status_locked(struct rpc_wait_queue *queue, int status)
+{
+ struct rpc_task *task;
+
for (;;) {
- while (!list_empty(head)) {
- struct rpc_task *task;
- task = list_first_entry(head,
- struct rpc_task,
- u.tk_wait.list);
- rpc_wake_up_task_queue_locked(queue, task);
- }
- if (head == &queue->tasks[0])
+ task = __rpc_find_next_queued(queue);
+ if (task == NULL)
break;
- head--;
+ rpc_wake_up_task_queue_set_status_locked(queue, task, status);
}
- spin_unlock(&queue->lock);
}
-EXPORT_SYMBOL_GPL(rpc_wake_up);

/**
* rpc_wake_up_status - wake up all rpc_tasks and set their status value.
@@ -712,23 +732,8 @@ EXPORT_SYMBOL_GPL(rpc_wake_up);
*/
void rpc_wake_up_status(struct rpc_wait_queue *queue, int status)
{
- struct list_head *head;
-
spin_lock(&queue->lock);
- head = &queue->tasks[queue->maxpriority];
- for (;;) {
- while (!list_empty(head)) {
- struct rpc_task *task;
- task = list_first_entry(head,
- struct rpc_task,
- u.tk_wait.list);
- task->tk_status = status;
- rpc_wake_up_task_queue_locked(queue, task);
- }
- if (head == &queue->tasks[0])
- break;
- head--;
- }
+ rpc_wake_up_status_locked(queue, status);
spin_unlock(&queue->lock);
}
EXPORT_SYMBOL_GPL(rpc_wake_up_status);
--
2.27.0