[PATCH] knfsd: fix recently introduced problem with shutting down a busy NFS server

When the last thread of nfsd exits, it shuts down all related sockets.  It
currently uses svc_close_socket to do this, but that only is immediately
effective if the socket is not SK_BUSY.

If the socket is busy - i.e.  if a request has arrived that has not yet been
processes - svc_close_socket is not effective and the shutdown process spins.

So create a new svc_force_close_socket which removes the SK_BUSY flag is set
and then calls svc_close_socket.

Also change some open-codes loops in svc_destroy to use
list_for_each_entry_safe.

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 25 insertions, 14 deletions

diff --git a/include/linux/sunrpc/svcsock.h b/include/linux/sunrpc/svcsock.h
index cccea0a0feb4..7909687557bf 100644
--- a/include/linux/sunrpc/svcsock.h
+++ b/include/linux/sunrpc/svcsock.h
@@ -66,7 +66,7 @@ struct svc_sock {
  * Function prototypes.
  */
 int             svc_makesock(struct svc_serv *, int, unsigned short, int flags);
-void            svc_close_socket(struct svc_sock *);
+void            svc_force_close_socket(struct svc_sock *);
 int             svc_recv(struct svc_rqst *, long);
 int             svc_send(struct svc_rqst *);
 void            svc_drop(struct svc_rqst *);
diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
index 8353829bc5c6..f960b138236f 100644
--- a/net/sunrpc/svc.c
+++ b/net/sunrpc/svc.c
@@ -367,6 +367,7 @@ void
 svc_destroy(struct svc_serv *serv)
 {
         struct svc_sock *svsk;
+        struct svc_sock *tmp;
 
         dprintk("svc: svc_destroy(%s, %d)\n",
                                 serv->sv_program->pg_name,
@@ -382,21 +383,17 @@ svc_destroy(struct svc_serv *serv)
 
         del_timer_sync(&serv->sv_temptimer);
 
-        while (!list_empty(&serv->sv_tempsocks)) {
-                svsk = list_entry(serv->sv_tempsocks.next,
-                                  struct svc_sock,
-                                  sk_list);
-                svc_close_socket(svsk);
-        }
+        list_for_each_entry_safe(svsk, tmp, &serv->sv_tempsocks, sk_list)
+                svc_force_close_socket(svsk);
+
         if (serv->sv_shutdown)
                 serv->sv_shutdown(serv);
 
-        while (!list_empty(&serv->sv_permsocks)) {
-                svsk = list_entry(serv->sv_permsocks.next,
-                                  struct svc_sock,
-                                  sk_list);
-                svc_close_socket(svsk);
-        }
+        list_for_each_entry_safe(svsk, tmp, &serv->sv_permsocks, sk_list)
+                svc_force_close_socket(svsk);
+
+        BUG_ON(!list_empty(&serv->sv_permsocks));
+        BUG_ON(!list_empty(&serv->sv_tempsocks));
 
         cache_clean_deferred(serv);
 
diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
index e957ce55fd91..f6e1eb1ea720 100644
--- a/net/sunrpc/svcsock.c
+++ b/net/sunrpc/svcsock.c
@@ -82,6 +82,7 @@ static void		svc_delete_socket(struct svc_sock *svsk);
 static void             svc_udp_data_ready(struct sock *, int);
 static int              svc_udp_recvfrom(struct svc_rqst *);
 static int              svc_udp_sendto(struct svc_rqst *);
+static void             svc_close_socket(struct svc_sock *svsk);
 
 static struct svc_deferred_req *svc_deferred_dequeue(struct svc_sock *svsk);
 static int svc_deferred_recv(struct svc_rqst *rqstp);
@@ -1787,7 +1788,7 @@ svc_delete_socket(struct svc_sock *svsk)
         spin_unlock_bh(&serv->sv_lock);
 }
 
-void svc_close_socket(struct svc_sock *svsk)
+static void svc_close_socket(struct svc_sock *svsk)
 {
         set_bit(SK_CLOSE, &svsk->sk_flags);
         if (test_and_set_bit(SK_BUSY, &svsk->sk_flags))
@@ -1800,6 +1801,19 @@ void svc_close_socket(struct svc_sock *svsk)
         svc_sock_put(svsk);
 }
 
+void svc_force_close_socket(struct svc_sock *svsk)
+{
+        set_bit(SK_CLOSE, &svsk->sk_flags);
+        if (test_bit(SK_BUSY, &svsk->sk_flags)) {
+                /* Waiting to be processed, but no threads left,
+                 * So just remove it from the waiting list
+                 */
+                list_del_init(&svsk->sk_ready);
+                clear_bit(SK_BUSY, &svsk->sk_flags);
+        }
+        svc_close_socket(svsk);
+}
+
 /**
  * svc_makesock - Make a socket for nfsd and lockd
  * @serv: RPC server structure