Commit 8e0c8d23 authored by Jeff Layton's avatar Jeff Layton Committed by Chuck Lever
Browse files

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: default avatarJeff Layton <jlayton@kernel.org>
Signed-off-by: default avatarChuck Lever <chuck.lever@oracle.com>
parent 3a6adfca

include/linux/sunrpc/svc.h

+1 −0
Original line number Diff line number Diff line
@@ -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);

net/sunrpc/svc.c

+7 −19
Original line number Diff line number Diff line
@@ -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];