sunrpc: fix up the special handling of sv_nrpools == 1

Only pooled services take a reference to the svc_pool_map. The sunrpc
code has always used the sv_nrpools value to detect whether the service
is pooled.

The problem there is that nfsd is a pooled service, but when it's
running in "global" pool_mode, it doesn't take a reference to the pool
map because it has a sv_nrpools value of 1. This means that we have
two separate codepaths for starting the server, depending on whether
it's pooled or not.

Fix this by adding a new flag to the svc_serv, that indicates whether
the serv is pooled. With this we can have the nfsd service
unconditionally take a reference, regardless of pool_mode.

Note that this is a behavior change for
/sys/module/sunrpc/parameters/pool_mode. Usually this file does not
allow you to change the pool-mode while there are nfsd threads running,
but if the pool-mode is "global" it's allowed. My assumption is that
this is a bug, since it probably should never have worked this way.

This patch changes the behavior such that you get back EBUSY even
when nfsd is running in global mode. I think this is more reasonable
behavior, and given that most people set this today using the module
parameter, it's doubtful anyone will notice.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
index 23617da0e565e7768947655447b9ff9ef5422688..d0433e1642b3e7213897e5d0feaa56213c1a4b65 100644 (file)
--- a/include/linux/sunrpc/svc.h
+++ b/include/linux/sunrpc/svc.h
@@ -85,6 +85,7 @@ struct svc_serv {
        char *                  sv_name;        /* service name */
 
        unsigned int            sv_nrpools;     /* number of thread pools */
+       bool                    sv_is_pooled;   /* is this a pooled service? */
        struct svc_pool *       sv_pools;       /* array of thread pools */
        int                     (*sv_threadfn)(void *data);
 

diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
index d9cda1e53a017ad3ede88cb458b408a22ba20d81..748060bb17af522aa4e09ed736fd3c1dcb9908ca 100644 (file)
--- a/net/sunrpc/svc.c
+++ b/net/sunrpc/svc.c
@@ -250,10 +250,8 @@ svc_pool_map_get(void)
        int npools = -1;
 
        mutex_lock(&svc_pool_map_mutex);
-
        if (m->count++) {
                mutex_unlock(&svc_pool_map_mutex);
-               WARN_ON_ONCE(m->npools <= 1);
                return m->npools;
        }
 
@@ -275,32 +273,21 @@ svc_pool_map_get(void)
                m->mode = SVC_POOL_GLOBAL;
        }
        m->npools = npools;
-
-       if (npools == 1)
-               /* service is unpooled, so doesn't hold a reference */
-               m->count--;
-
        mutex_unlock(&svc_pool_map_mutex);
        return npools;
 }
 
 /*
- * Drop a reference to the global map of cpus to pools, if
- * pools were in use, i.e. if npools > 1.
+ * Drop a reference to the global map of cpus to pools.
  * When the last reference is dropped, the map data is
- * freed; this allows the sysadmin to change the pool
- * mode using the pool_mode module option without
- * rebooting or re-loading sunrpc.ko.
+ * freed; this allows the sysadmin to change the pool.
  */
 static void
-svc_pool_map_put(int npools)
+svc_pool_map_put(void)
 {
        struct svc_pool_map *m = &svc_pool_map;
 
-       if (npools <= 1)
-               return;
        mutex_lock(&svc_pool_map_mutex);
-
        if (!--m->count) {
                kfree(m->to_pool);
                m->to_pool = NULL;
@@ -308,7 +295,6 @@ svc_pool_map_put(int npools)
                m->pool_to = NULL;
                m->npools = 0;
        }
-
        mutex_unlock(&svc_pool_map_mutex);
 }
 
@@ -553,9 +539,10 @@ struct svc_serv *svc_create_pooled(struct svc_program *prog,
        serv = __svc_create(prog, stats, bufsize, npools, threadfn);
        if (!serv)
                goto out_err;
+       serv->sv_is_pooled = true;
        return serv;
 out_err:
-       svc_pool_map_put(npools);
+       svc_pool_map_put();
        return NULL;
 }
 EXPORT_SYMBOL_GPL(svc_create_pooled);
@@ -585,7 +572,8 @@ svc_destroy(struct svc_serv **servp)
 
        cache_clean_deferred(serv);
 
-       svc_pool_map_put(serv->sv_nrpools);
+       if (serv->sv_is_pooled)
+               svc_pool_map_put();
 
        for (i = 0; i < serv->sv_nrpools; i++) {
                struct svc_pool *pool = &serv->sv_pools[i];