This is a note to let you know that I've just added the patch titled
SUNRPC: always treat sv_nrpools==1 as "not pooled"
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
sunrpc-always-treat-sv_nrpools-1-as-not-pooled.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 26784b95960569776f9f0e1163e9865a6e4c5022
Author: NeilBrown <neilb@xxxxxxx>
Date: Mon Nov 29 15:51:25 2021 +1100
SUNRPC: always treat sv_nrpools==1 as "not pooled"
[ Upstream commit 93aa619eb0b42eec2f3a9b4d9db41f5095390aec ]
Currently 'pooled' services hold a reference on the pool_map, and
'unpooled' services do not.
svc_destroy() uses the presence of ->svo_function (via
svc_serv_is_pooled()) to determine if the reference should be dropped.
There is no direct correlation between being pooled and the use of
svo_function, though in practice, lockd is the only non-pooled service,
and the only one not to use svo_function.
This is untidy and would cause problems if we changed lockd to use
svc_set_num_threads(), which requires the use of ->svo_function.
So change the test for "is the service pooled" to "is sv_nrpools > 1".
This means that when svc_pool_map_get() returns 1, it must NOT take a
reference to the pool.
We discard svc_serv_is_pooled(), and test sv_nrpools directly.
Signed-off-by: NeilBrown <neilb@xxxxxxx>
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
index 8fbfea9f2a04c..fee7a22578b64 100644
--- a/net/sunrpc/svc.c
+++ b/net/sunrpc/svc.c
@@ -37,8 +37,6 @@
static void svc_unregister(const struct svc_serv *serv, struct net *net);
-#define svc_serv_is_pooled(serv) ((serv)->sv_ops->svo_function)
-
#define SVC_POOL_DEFAULT SVC_POOL_GLOBAL
/*
@@ -240,8 +238,10 @@ svc_pool_map_init_pernode(struct svc_pool_map *m)
/*
* Add a reference to the global map of cpus to pools (and
- * vice versa). Initialise the map if we're the first user.
- * Returns the number of pools.
+ * vice versa) if pools are in use.
+ * Initialise the map if we're the first user.
+ * Returns the number of pools. If this is '1', no reference
+ * was taken.
*/
static unsigned int
svc_pool_map_get(void)
@@ -253,6 +253,7 @@ svc_pool_map_get(void)
if (m->count++) {
mutex_unlock(&svc_pool_map_mutex);
+ WARN_ON_ONCE(m->npools <= 1);
return m->npools;
}
@@ -268,29 +269,36 @@ svc_pool_map_get(void)
break;
}
- if (npools < 0) {
+ if (npools <= 0) {
/* default, or memory allocation failure */
npools = 1;
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 m->npools;
+ return npools;
}
/*
- * Drop a reference to the global map of cpus to pools.
+ * Drop a reference to the global map of cpus to pools, if
+ * pools were in use, i.e. if npools > 1.
* 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.
*/
static void
-svc_pool_map_put(void)
+svc_pool_map_put(int npools)
{
struct svc_pool_map *m = &svc_pool_map;
+ if (npools <= 1)
+ return;
mutex_lock(&svc_pool_map_mutex);
if (!--m->count) {
@@ -359,21 +367,18 @@ svc_pool_for_cpu(struct svc_serv *serv, int cpu)
struct svc_pool_map *m = &svc_pool_map;
unsigned int pidx = 0;
- /*
- * An uninitialised map happens in a pure client when
- * lockd is brought up, so silently treat it the
- * same as SVC_POOL_GLOBAL.
- */
- if (svc_serv_is_pooled(serv)) {
- switch (m->mode) {
- case SVC_POOL_PERCPU:
- pidx = m->to_pool[cpu];
- break;
- case SVC_POOL_PERNODE:
- pidx = m->to_pool[cpu_to_node(cpu)];
- break;
- }
+ if (serv->sv_nrpools <= 1)
+ return serv->sv_pools;
+
+ switch (m->mode) {
+ case SVC_POOL_PERCPU:
+ pidx = m->to_pool[cpu];
+ break;
+ case SVC_POOL_PERNODE:
+ pidx = m->to_pool[cpu_to_node(cpu)];
+ break;
}
+
return &serv->sv_pools[pidx % serv->sv_nrpools];
}
@@ -526,7 +531,7 @@ svc_create_pooled(struct svc_program *prog, unsigned int bufsize,
goto out_err;
return serv;
out_err:
- svc_pool_map_put();
+ svc_pool_map_put(npools);
return NULL;
}
EXPORT_SYMBOL_GPL(svc_create_pooled);
@@ -561,8 +566,7 @@ svc_destroy(struct kref *ref)
cache_clean_deferred(serv);
- if (svc_serv_is_pooled(serv))
- svc_pool_map_put();
+ svc_pool_map_put(serv->sv_nrpools);
kfree(serv->sv_pools);
kfree(serv);
