NLM: Convert lockd to use kthreads

Have lockd_up start lockd using kthread_run. With this change,
lockd_down now blocks until lockd actually exits, so there's no longer
need for the waitqueue code at the end of lockd_down. This also means
that only one lockd can be running at a time which simplifies the code
within lockd's main loop.

This also adds a check for kthread_should_stop in the main loop of
nlmsvc_retry_blocked and after that function returns. There's no sense
continuing to retry blocks if lockd is coming down anyway.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

1 files changed, 58 insertions, 74 deletions

diff --git a/fs/lockd/svc.c b/fs/lockd/svc.c
index 1ed8bd4de941..66b5c98c7ff5 100644
--- a/fs/lockd/svc.c
+++ b/fs/lockd/svc.c
@@ -25,6 +25,7 @@
 #include <linux/smp.h>
 #include <linux/smp_lock.h>
 #include <linux/mutex.h>
+#include <linux/kthread.h>
 #include <linux/freezer.h>
 
 #include <linux/sunrpc/types.h>
@@ -48,14 +49,11 @@ EXPORT_SYMBOL(nlmsvc_ops);
 
 static DEFINE_MUTEX(nlmsvc_mutex);
 static unsigned int             nlmsvc_users;
-static pid_t                    nlmsvc_pid;
+static struct task_struct       *nlmsvc_task;
 static struct svc_serv          *nlmsvc_serv;
 int                             nlmsvc_grace_period;
 unsigned long                   nlmsvc_timeout;
 
-static DECLARE_COMPLETION(lockd_start_done);
-static DECLARE_WAIT_QUEUE_HEAD(lockd_exit);
-
 /*
  * These can be set at insmod time (useful for NFS as root filesystem),
  * and also changed through the sysctl interface.  -- Jamie Lokier, Aug 2003
@@ -111,35 +109,30 @@ static inline void clear_grace_period(void)
 /*
  * This is the lockd kernel thread
  */
-static void
-lockd(struct svc_rqst *rqstp)
+static int
+lockd(void *vrqstp)
 {
         int             err = 0;
+        struct svc_rqst *rqstp = vrqstp;
         unsigned long grace_period_expire;
 
-        /* Lock module and set up kernel thread */
-        /* lockd_up is waiting for us to startup, so will
-         * be holding a reference to this module, so it
-         * is safe to just claim another reference
-         */
-        __module_get(THIS_MODULE);
-        lock_kernel();
-
-        /*
-         * Let our maker know we're running.
-         */
-        nlmsvc_pid = current->pid;
-        nlmsvc_serv = rqstp->rq_server;
-        complete(&lockd_start_done);
-
-        daemonize("lockd");
+        /* try_to_freeze() is called from svc_recv() */
         set_freezable();
 
-        /* Process request with signals blocked, but allow SIGKILL.  */
+        /* Allow SIGKILL to tell lockd to drop all of its locks */
         allow_signal(SIGKILL);
 
         dprintk("NFS locking service started (ver " LOCKD_VERSION ").\n");
 
+        /*
+         * FIXME: it would be nice if lockd didn't spend its entire life
+         * running under the BKL. At the very least, it would be good to
+         * have someone clarify what it's intended to protect here. I've
+         * seen some handwavy posts about posix locking needing to be
+         * done under the BKL, but it's far from clear.
+         */
+        lock_kernel();
+
         if (!nlm_timeout)
                 nlm_timeout = LOCKD_DFLT_TIMEO;
         nlmsvc_timeout = nlm_timeout * HZ;
@@ -148,10 +141,9 @@ lockd(struct svc_rqst *rqstp)
 
         /*
          * The main request loop. We don't terminate until the last
-         * NFS mount or NFS daemon has gone away, and we've been sent a
-         * signal, or else another process has taken over our job.
+         * NFS mount or NFS daemon has gone away.
          */
-        while ((nlmsvc_users || !signalled()) && nlmsvc_pid == current->pid) {
+        while (!kthread_should_stop()) {
                 long timeout = MAX_SCHEDULE_TIMEOUT;
                 RPC_IFDEBUG(char buf[RPC_MAX_ADDRBUFLEN]);
 
@@ -161,6 +153,7 @@ lockd(struct svc_rqst *rqstp)
                                 nlmsvc_invalidate_all();
                                 grace_period_expire = set_grace_period();
                         }
+                        continue;
                 }
 
                 /*
@@ -195,28 +188,19 @@ lockd(struct svc_rqst *rqstp)
         }
 
         flush_signals(current);
+        if (nlmsvc_ops)
+                nlmsvc_invalidate_all();
+        nlm_shutdown_hosts();
 
-        /*
-         * Check whether there's a new lockd process before
-         * shutting down the hosts and clearing the slot.
-         */
-        if (!nlmsvc_pid || current->pid == nlmsvc_pid) {
-                if (nlmsvc_ops)
-                        nlmsvc_invalidate_all();
-                nlm_shutdown_hosts();
-                nlmsvc_pid = 0;
-                nlmsvc_serv = NULL;
-        } else
-                printk(KERN_DEBUG
-                        "lockd: new process, skipping host shutdown\n");
-        wake_up(&lockd_exit);
+        unlock_kernel();
+
+        nlmsvc_task = NULL;
+        nlmsvc_serv = NULL;
 
         /* Exit the RPC thread */
         svc_exit_thread(rqstp);
 
-        /* Release module */
-        unlock_kernel();
-        module_put_and_exit(0);
+        return 0;
 }
 
 /*
@@ -261,14 +245,15 @@ static int make_socks(struct svc_serv *serv, int proto)
 int
 lockd_up(int proto) /* Maybe add a 'family' option when IPv6 is supported ?? */
 {
-        struct svc_serv *       serv;
-        int                     error = 0;
+        struct svc_serv *serv;
+        struct svc_rqst *rqstp;
+        int             error = 0;
 
         mutex_lock(&nlmsvc_mutex);
         /*
          * Check whether we're already up and running.
          */
-        if (nlmsvc_pid) {
+        if (nlmsvc_serv) {
                 if (proto)
                         error = make_socks(nlmsvc_serv, proto);
                 goto out;
@@ -295,13 +280,28 @@ lockd_up(int proto) /* Maybe add a 'family' option when IPv6 is supported ?? */
         /*
          * Create the kernel thread and wait for it to start.
          */
-        error = svc_create_thread(lockd, serv);
-        if (error) {
+        rqstp = svc_prepare_thread(serv, &serv->sv_pools[0]);
+        if (IS_ERR(rqstp)) {
+                error = PTR_ERR(rqstp);
                 printk(KERN_WARNING
-                        "lockd_up: create thread failed, error=%d\n", error);
+                        "lockd_up: svc_rqst allocation failed, error=%d\n",
+                        error);
+                goto destroy_and_out;
+        }
+
+        svc_sock_update_bufs(serv);
+        nlmsvc_serv = rqstp->rq_server;
+
+        nlmsvc_task = kthread_run(lockd, rqstp, serv->sv_name);
+        if (IS_ERR(nlmsvc_task)) {
+                error = PTR_ERR(nlmsvc_task);
+                nlmsvc_task = NULL;
+                nlmsvc_serv = NULL;
+                printk(KERN_WARNING
+                        "lockd_up: kthread_run failed, error=%d\n", error);
+                svc_exit_thread(rqstp);
                 goto destroy_and_out;
         }
-        wait_for_completion(&lockd_start_done);
 
         /*
          * Note: svc_serv structures have an initial use count of 1,
@@ -323,37 +323,21 @@ EXPORT_SYMBOL(lockd_up);
 void
 lockd_down(void)
 {
-        static int warned;
-
         mutex_lock(&nlmsvc_mutex);
         if (nlmsvc_users) {
                 if (--nlmsvc_users)
                         goto out;
-        } else
-                printk(KERN_WARNING "lockd_down: no users! pid=%d\n", nlmsvc_pid);
-
-        if (!nlmsvc_pid) {
-                if (warned++ == 0)
-                        printk(KERN_WARNING "lockd_down: no lockd running.\n"); 
-                goto out;
+        } else {
+                printk(KERN_ERR "lockd_down: no users! task=%p\n",
+                        nlmsvc_task);
+                BUG();
         }
-        warned = 0;
 
-        kill_proc(nlmsvc_pid, SIGKILL, 1);
-        /*
-         * Wait for the lockd process to exit, but since we're holding
-         * the lockd semaphore, we can't wait around forever ...
-         */
-        clear_thread_flag(TIF_SIGPENDING);
-        interruptible_sleep_on_timeout(&lockd_exit, HZ);
-        if (nlmsvc_pid) {
-                printk(KERN_WARNING 
-                        "lockd_down: lockd failed to exit, clearing pid\n");
-                nlmsvc_pid = 0;
+        if (!nlmsvc_task) {
+                printk(KERN_ERR "lockd_down: no lockd running.\n");
+                BUG();
         }
-        spin_lock_irq(&current->sighand->siglock);
-        recalc_sigpending();
-        spin_unlock_irq(&current->sighand->siglock);
+        kthread_stop(nlmsvc_task);
 out:
         mutex_unlock(&nlmsvc_mutex);
 }