knfsd: convert knfsd to kthread API

This patch is rather large, but I couldn't figure out a way to break it
up that would remain bisectable. It does several things:

- change svc_thread_fn typedef to better match what kthread_create expects
- change svc_pool_map_set_cpumask to be more kthread friendly. Make it
  take a task arg and and get rid of the "oldmask"
- have svc_set_num_threads call kthread_create directly
- eliminate __svc_create_thread

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

3 files changed, 64 insertions, 83 deletions

diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
index 6339cb70a08d..9e2156813710 100644
--- a/fs/nfsd/nfssvc.c
+++ b/fs/nfsd/nfssvc.c
@@ -21,6 +21,7 @@
 #include <linux/smp_lock.h>
 #include <linux/freezer.h>
 #include <linux/fs_struct.h>
+#include <linux/kthread.h>
 
 #include <linux/sunrpc/types.h>
 #include <linux/sunrpc/stats.h>
@@ -46,7 +47,7 @@
 #define SHUTDOWN_SIGS   (sigmask(SIGKILL) | sigmask(SIGHUP) | sigmask(SIGINT) | sigmask(SIGQUIT))
 
 extern struct svc_program       nfsd_program;
-static void                     nfsd(struct svc_rqst *rqstp);
+static int                      nfsd(void *vrqstp);
 struct timeval                  nfssvc_boot;
 static atomic_t                 nfsd_busy;
 static unsigned long            nfsd_last_call;
@@ -407,18 +408,19 @@ update_thread_usage(int busy_threads)
 /*
  * This is the NFS server kernel thread
  */
-static void
-nfsd(struct svc_rqst *rqstp)
+static int
+nfsd(void *vrqstp)
 {
+        struct svc_rqst *rqstp = (struct svc_rqst *) vrqstp;
         struct fs_struct *fsp;
-        int             err;
         sigset_t shutdown_mask, allowed_mask;
+        int err, preverr = 0;
+        unsigned int signo;
 
         /* Lock module and set up kernel thread */
         mutex_lock(&nfsd_mutex);
-        daemonize("nfsd");
 
-        /* After daemonize() this kernel thread shares current->fs
+        /* At this point, the thread shares current->fs
          * with the init process. We need to create files with a
          * umask of 0 instead of init's umask. */
         fsp = copy_fs_struct(current->fs);
@@ -433,14 +435,18 @@ nfsd(struct svc_rqst *rqstp)
         siginitsetinv(&shutdown_mask, SHUTDOWN_SIGS);
         siginitsetinv(&allowed_mask, ALLOWED_SIGS);
 
+        /*
+         * thread is spawned with all signals set to SIG_IGN, re-enable
+         * the ones that matter
+         */
+        for (signo = 1; signo <= _NSIG; signo++) {
+                if (!sigismember(&shutdown_mask, signo))
+                        allow_signal(signo);
+        }
 
         nfsdstats.th_cnt++;
-
-        rqstp->rq_task = current;
-
         mutex_unlock(&nfsd_mutex);
 
-
         /*
          * We want less throttling in balance_dirty_pages() so that nfs to
          * localhost doesn't cause nfsd to lock up due to all the client's
@@ -462,15 +468,25 @@ nfsd(struct svc_rqst *rqstp)
                  */
                 while ((err = svc_recv(rqstp, 60*60*HZ)) == -EAGAIN)
                         ;
-                if (err < 0)
+                if (err == -EINTR)
                         break;
+                else if (err < 0) {
+                        if (err != preverr) {
+                                printk(KERN_WARNING "%s: unexpected error "
+                                        "from svc_recv (%d)\n", __func__, -err);
+                                preverr = err;
+                        }
+                        schedule_timeout_uninterruptible(HZ);
+                        continue;
+                }
+
                 update_thread_usage(atomic_read(&nfsd_busy));
                 atomic_inc(&nfsd_busy);
 
                 /* Lock the export hash tables for reading. */
                 exp_readlock();
 
-                /* Process request with signals blocked.  */
+                /* Process request with signals blocked. */
                 sigprocmask(SIG_SETMASK, &allowed_mask, NULL);
 
                 svc_process(rqstp);
@@ -481,14 +497,10 @@ nfsd(struct svc_rqst *rqstp)
                 atomic_dec(&nfsd_busy);
         }
 
-        if (err != -EINTR)
-                printk(KERN_WARNING "nfsd: terminating on error %d\n", -err);
-
         /* Clear signals before calling svc_exit_thread() */
         flush_signals(current);
 
         mutex_lock(&nfsd_mutex);
-
         nfsdstats.th_cnt --;
 
 out:
@@ -498,6 +510,7 @@ out:
         /* Release module */
         mutex_unlock(&nfsd_mutex);
         module_put_and_exit(0);
+        return 0;
 }
 
 static __be32 map_new_errors(u32 vers, __be32 nfserr)
diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
index 4b54c5fdcfd9..011d6d8100d8 100644
--- a/include/linux/sunrpc/svc.h
+++ b/include/linux/sunrpc/svc.h
@@ -22,7 +22,7 @@
 /*
  * This is the RPC server thread function prototype
  */
-typedef void            (*svc_thread_fn)(struct svc_rqst *);
+typedef int             (*svc_thread_fn)(void *);
 
 /*
  *
diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
index 7bffaff2a3ab..03a9f1a9e75c 100644
--- a/net/sunrpc/svc.c
+++ b/net/sunrpc/svc.c
@@ -18,6 +18,7 @@
 #include <linux/mm.h>
 #include <linux/interrupt.h>
 #include <linux/module.h>
+#include <linux/kthread.h>
 
 #include <linux/sunrpc/types.h>
 #include <linux/sunrpc/xdr.h>
@@ -291,15 +292,14 @@ svc_pool_map_put(void)
 
 
 /*
- * Set the current thread's cpus_allowed mask so that it
+ * Set the given thread's cpus_allowed mask so that it
  * will only run on cpus in the given pool.
- *
- * Returns 1 and fills in oldmask iff a cpumask was applied.
  */
-static inline int
-svc_pool_map_set_cpumask(unsigned int pidx, cpumask_t *oldmask)
+static inline void
+svc_pool_map_set_cpumask(struct task_struct *task, unsigned int pidx)
 {
         struct svc_pool_map *m = &svc_pool_map;
+        unsigned int node = m->pool_to[pidx];
 
         /*
          * The caller checks for sv_nrpools > 1, which
@@ -307,26 +307,17 @@ svc_pool_map_set_cpumask(unsigned int pidx, cpumask_t *oldmask)
          */
         BUG_ON(m->count == 0);
 
-        switch (m->mode)
-        {
-        default:
-                return 0;
+        switch (m->mode) {
         case SVC_POOL_PERCPU:
         {
-                unsigned int cpu = m->pool_to[pidx];
-
-                *oldmask = current->cpus_allowed;
-                set_cpus_allowed_ptr(current, &cpumask_of_cpu(cpu));
-                return 1;
+                set_cpus_allowed_ptr(task, &cpumask_of_cpu(node));
+                break;
         }
         case SVC_POOL_PERNODE:
         {
-                unsigned int node = m->pool_to[pidx];
                 node_to_cpumask_ptr(nodecpumask, node);
-
-                *oldmask = current->cpus_allowed;
-                set_cpus_allowed_ptr(current, nodecpumask);
-                return 1;
+                set_cpus_allowed_ptr(task, nodecpumask);
+                break;
         }
         }
 }
@@ -579,47 +570,6 @@ out_enomem:
 EXPORT_SYMBOL(svc_prepare_thread);
 
 /*
- * Create a thread in the given pool.  Caller must hold BKL or another lock to
- * serialize access to the svc_serv struct. On a NUMA or SMP machine, with a
- * multi-pool serv, the thread will be restricted to run on the cpus belonging
- * to the pool.
- */
-static int
-__svc_create_thread(svc_thread_fn func, struct svc_serv *serv,
-                    struct svc_pool *pool)
-{
-        struct svc_rqst *rqstp;
-        int             error = -ENOMEM;
-        int             have_oldmask = 0;
-        cpumask_t       uninitialized_var(oldmask);
-
-        rqstp = svc_prepare_thread(serv, pool);
-        if (IS_ERR(rqstp)) {
-                error = PTR_ERR(rqstp);
-                goto out;
-        }
-
-        if (serv->sv_nrpools > 1)
-                have_oldmask = svc_pool_map_set_cpumask(pool->sp_id, &oldmask);
-
-        error = kernel_thread((int (*)(void *)) func, rqstp, 0);
-
-        if (have_oldmask)
-                set_cpus_allowed(current, oldmask);
-
-        if (error < 0)
-                goto out_thread;
-        svc_sock_update_bufs(serv);
-        error = 0;
-out:
-        return error;
-
-out_thread:
-        svc_exit_thread(rqstp);
-        goto out;
-}
-
-/*
  * Choose a pool in which to create a new thread, for svc_set_num_threads
  */
 static inline struct svc_pool *
@@ -688,7 +638,9 @@ found_pool:
 int
 svc_set_num_threads(struct svc_serv *serv, struct svc_pool *pool, int nrservs)
 {
-        struct task_struct *victim;
+        struct svc_rqst *rqstp;
+        struct task_struct *task;
+        struct svc_pool *chosen_pool;
         int error = 0;
         unsigned int state = serv->sv_nrthreads-1;
 
@@ -704,18 +656,34 @@ svc_set_num_threads(struct svc_serv *serv, struct svc_pool *pool, int nrservs)
         /* create new threads */
         while (nrservs > 0) {
                 nrservs--;
+                chosen_pool = choose_pool(serv, pool, &state);
+
+                rqstp = svc_prepare_thread(serv, chosen_pool);
+                if (IS_ERR(rqstp)) {
+                        error = PTR_ERR(rqstp);
+                        break;
+                }
+
                 __module_get(serv->sv_module);
-                error = __svc_create_thread(serv->sv_function, serv,
-                                            choose_pool(serv, pool, &state));
-                if (error < 0) {
+                task = kthread_create(serv->sv_function, rqstp, serv->sv_name);
+                if (IS_ERR(task)) {
+                        error = PTR_ERR(task);
                         module_put(serv->sv_module);
+                        svc_exit_thread(rqstp);
                         break;
                 }
+
+                rqstp->rq_task = task;
+                if (serv->sv_nrpools > 1)
+                        svc_pool_map_set_cpumask(task, chosen_pool->sp_id);
+
+                svc_sock_update_bufs(serv);
+                wake_up_process(task);
         }
         /* destroy old threads */
         while (nrservs < 0 &&
-               (victim = choose_victim(serv, pool, &state)) != NULL) {
-                send_sig(serv->sv_kill_signal, victim, 1);
+               (task = choose_victim(serv, pool, &state)) != NULL) {
+                send_sig(serv->sv_kill_signal, task, 1);
                 nrservs++;
         }