[PATCH 4.9 02/77] NFSv4: Fix callback server shutdown

Greg Kroah-Hartman
2017-09-24T20:37:22Z

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

commit ed6473ddc704a2005b9900ca08e236ebb2d8540a upstream.

We want to use kthread_stop() in order to ensure the threads are
shut down before we tear down the nfs_callback_info in nfs_callback_down.

Tested-and-reviewed-by: Kinglong Mee <kinglongmee@gmail.com>
Reported-by: Kinglong Mee <kinglongmee@gmail.com>
Fixes: bb6aeba736ba9 ("NFSv4.x: Switch to using svc_set_num_threads()...")
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Cc: Jan Hudoba <kernel@jahu.sk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/nfs/callback.c | 24 ++++++++++++++++--------
include/linux/sunrpc/svc.h | 1 +
net/sunrpc/svc.c | 38 ++++++++++++++++++++++++++++++++++++++
3 files changed, 55 insertions(+), 8 deletions(-)

--- a/fs/nfs/callback.c
+++ b/fs/nfs/callback.c
@@ -75,7 +75,10 @@ nfs4_callback_svc(void *vrqstp)

set_freezable();

- while (!kthread_should_stop()) {
+ while (!kthread_freezable_should_stop(NULL)) {
+
+ if (signal_pending(current))
+ flush_signals(current);
/*
* Listen for a request on the socket
*/
@@ -84,6 +87,8 @@ nfs4_callback_svc(void *vrqstp)
continue;
svc_process(rqstp);
}
+ svc_exit_thread(rqstp);
+ module_put_and_exit(0);
return 0;
}

@@ -102,9 +107,10 @@ nfs41_callback_svc(void *vrqstp)

set_freezable();

- while (!kthread_should_stop()) {
- if (try_to_freeze())
- continue;
+ while (!kthread_freezable_should_stop(NULL)) {
+
+ if (signal_pending(current))
+ flush_signals(current);

prepare_to_wait(&serv->sv_cb_waitq, &wq, TASK_INTERRUPTIBLE);
spin_lock_bh(&serv->sv_cb_lock);
@@ -120,11 +126,13 @@ nfs41_callback_svc(void *vrqstp)
error);
} else {
spin_unlock_bh(&serv->sv_cb_lock);
- schedule();
+ if (!kthread_should_stop())
+ schedule();
finish_wait(&serv->sv_cb_waitq, &wq);
}
- flush_signals(current);
}
+ svc_exit_thread(rqstp);
+ module_put_and_exit(0);
return 0;
}

@@ -220,14 +228,14 @@ err_bind:
static struct svc_serv_ops nfs40_cb_sv_ops = {
.svo_function = nfs4_callback_svc,
.svo_enqueue_xprt = svc_xprt_do_enqueue,
- .svo_setup = svc_set_num_threads,
+ .svo_setup = svc_set_num_threads_sync,
.svo_module = THIS_MODULE,
};
#if defined(CONFIG_NFS_V4_1)
static struct svc_serv_ops nfs41_cb_sv_ops = {
.svo_function = nfs41_callback_svc,
.svo_enqueue_xprt = svc_xprt_do_enqueue,
- .svo_setup = svc_set_num_threads,
+ .svo_setup = svc_set_num_threads_sync,
.svo_module = THIS_MODULE,
};

--- a/include/linux/sunrpc/svc.h
+++ b/include/linux/sunrpc/svc.h
@@ -470,6 +470,7 @@ void svc_pool_map_put(void);
struct svc_serv * svc_create_pooled(struct svc_program *, unsigned int,
struct svc_serv_ops *);
int svc_set_num_threads(struct svc_serv *, struct svc_pool *, int);
+int svc_set_num_threads_sync(struct svc_serv *, struct svc_pool *, int);
int svc_pool_stats_open(struct svc_serv *serv, struct file *file);
void svc_destroy(struct svc_serv *);
void svc_shutdown_net(struct svc_serv *, struct net *);
--- a/net/sunrpc/svc.c
+++ b/net/sunrpc/svc.c
@@ -795,6 +795,44 @@ svc_set_num_threads(struct svc_serv *ser
}
EXPORT_SYMBOL_GPL(svc_set_num_threads);

+/* destroy old threads */
+static int
+svc_stop_kthreads(struct svc_serv *serv, struct svc_pool *pool, int nrservs)
+{
+ struct task_struct *task;
+ unsigned int state = serv->sv_nrthreads-1;
+
+ /* destroy old threads */
+ do {
+ task = choose_victim(serv, pool, &state);
+ if (task == NULL)
+ break;
+ kthread_stop(task);
+ nrservs++;
+ } while (nrservs < 0);
+ return 0;
+}
+
+int
+svc_set_num_threads_sync(struct svc_serv *serv, struct svc_pool *pool, int nrservs)
+{
+ if (pool == NULL) {
+ /* The -1 assumes caller has done a svc_get() */
+ nrservs -= (serv->sv_nrthreads-1);
+ } else {
+ spin_lock_bh(&pool->sp_lock);
+ nrservs -= pool->sp_nrthreads;
+ spin_unlock_bh(&pool->sp_lock);
+ }
+
+ if (nrservs > 0)
+ return svc_start_kthreads(serv, pool, nrservs);
+ if (nrservs < 0)
+ return svc_stop_kthreads(serv, pool, nrservs);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(svc_set_num_threads_sync);
+
/*
* Called from a server thread as it's exiting. Caller must hold the "service
* mutex" for the service.