sunrpc: add a rcu_head to svc_rqst and use kfree_rcu to free it

...also make the manipulation of sp_all_threads list use RCU-friendly
functions.

Signed-off-by: Jeff Layton <jlayton@primarydata.com>
Tested-by: Chris Worley <chris.worley@primarydata.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

3 files changed, 10 insertions, 5 deletions

diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
index 5f0ab39bf7c3..7f80a99c59e4 100644
--- a/include/linux/sunrpc/svc.h
+++ b/include/linux/sunrpc/svc.h
@@ -223,6 +223,7 @@ static inline void svc_putu32(struct kvec *iov, __be32 val)
 struct svc_rqst {
         struct list_head        rq_list;        /* idle list */
         struct list_head        rq_all;         /* all threads list */
+        struct rcu_head         rq_rcu_head;    /* for RCU deferred kfree */
         struct svc_xprt *       rq_xprt;        /* transport ptr */
 
         struct sockaddr_storage rq_addr;        /* peer address */
@@ -262,6 +263,7 @@ struct svc_rqst {
 #define RQ_SPLICE_OK    (4)                     /* turned off in gss privacy
                                                  * to prevent encrypting page
                                                  * cache pages */
+#define RQ_VICTIM       (5)                     /* about to be shut down */
         unsigned long           rq_flags;       /* flags field */
 
         void *                  rq_argp;        /* decoded arguments */
diff --git a/include/trace/events/sunrpc.h b/include/trace/events/sunrpc.h
index 5848fc235869..08a5fed50f34 100644
--- a/include/trace/events/sunrpc.h
+++ b/include/trace/events/sunrpc.h
@@ -418,7 +418,8 @@ TRACE_EVENT(xs_tcp_data_recv,
                 { (1UL << RQ_LOCAL),            "RQ_LOCAL"},            \
                 { (1UL << RQ_USEDEFERRAL),      "RQ_USEDEFERRAL"},      \
                 { (1UL << RQ_DROPME),           "RQ_DROPME"},           \
-                { (1UL << RQ_SPLICE_OK),        "RQ_SPLICE_OK"})
+                { (1UL << RQ_SPLICE_OK),        "RQ_SPLICE_OK"},        \
+                { (1UL << RQ_VICTIM),           "RQ_VICTIM"})
 
 TRACE_EVENT(svc_recv,
         TP_PROTO(struct svc_rqst *rqst, int status),
diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
index a06a891012e5..b90d1bca4349 100644
--- a/net/sunrpc/svc.c
+++ b/net/sunrpc/svc.c
@@ -616,7 +616,7 @@ svc_prepare_thread(struct svc_serv *serv, struct svc_pool *pool, int node)
         serv->sv_nrthreads++;
         spin_lock_bh(&pool->sp_lock);
         pool->sp_nrthreads++;
-        list_add(&rqstp->rq_all, &pool->sp_all_threads);
+        list_add_rcu(&rqstp->rq_all, &pool->sp_all_threads);
         spin_unlock_bh(&pool->sp_lock);
         rqstp->rq_server = serv;
         rqstp->rq_pool = pool;
@@ -684,7 +684,8 @@ found_pool:
                  * so we don't try to kill it again.
                  */
                 rqstp = list_entry(pool->sp_all_threads.next, struct svc_rqst, rq_all);
-                list_del_init(&rqstp->rq_all);
+                set_bit(RQ_VICTIM, &rqstp->rq_flags);
+                list_del_rcu(&rqstp->rq_all);
                 task = rqstp->rq_task;
         }
         spin_unlock_bh(&pool->sp_lock);
@@ -782,10 +783,11 @@ svc_exit_thread(struct svc_rqst *rqstp)
 
         spin_lock_bh(&pool->sp_lock);
         pool->sp_nrthreads--;
-        list_del(&rqstp->rq_all);
+        if (!test_and_set_bit(RQ_VICTIM, &rqstp->rq_flags))
+                list_del_rcu(&rqstp->rq_all);
         spin_unlock_bh(&pool->sp_lock);
 
-        kfree(rqstp);
+        kfree_rcu(rqstp, rq_rcu_head);
 
         /* Release the server */
         if (serv)