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@xxxxxxxxxx>
---
include/linux/sunrpc/svc.h | 1 +
net/sunrpc/svc.c | 26 +++++++-------------------
2 files changed, 8 insertions(+), 19 deletions(-)
diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
index 23617da0e565..d0433e1642b3 100644
--- 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 2b4b1276d4e8..f80d94cbb8b1 100644
--- 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];
--
2.45.2
