linux/fs/lockd/host.c
Trond Myklebust 28df955a2a NLM: Fix reclaim races
Currently it is possible for a task to remove its locks at the same time as
the NLM recovery thread is trying to recover them. This quickly leads to an
Oops.
Protect the locks using an rw semaphore while they are being recovered.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
2006-06-09 09:40:27 -04:00

351 lines
8.7 KiB
C

/*
* linux/fs/lockd/host.c
*
* Management for NLM peer hosts. The nlm_host struct is shared
* between client and server implementation. The only reason to
* do so is to reduce code bloat.
*
* Copyright (C) 1996, Olaf Kirch <okir@monad.swb.de>
*/
#include <linux/types.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/in.h>
#include <linux/sunrpc/clnt.h>
#include <linux/sunrpc/svc.h>
#include <linux/lockd/lockd.h>
#include <linux/lockd/sm_inter.h>
#include <linux/mutex.h>
#define NLMDBG_FACILITY NLMDBG_HOSTCACHE
#define NLM_HOST_MAX 64
#define NLM_HOST_NRHASH 32
#define NLM_ADDRHASH(addr) (ntohl(addr) & (NLM_HOST_NRHASH-1))
#define NLM_HOST_REBIND (60 * HZ)
#define NLM_HOST_EXPIRE ((nrhosts > NLM_HOST_MAX)? 300 * HZ : 120 * HZ)
#define NLM_HOST_COLLECT ((nrhosts > NLM_HOST_MAX)? 120 * HZ : 60 * HZ)
#define NLM_HOST_ADDR(sv) (&(sv)->s_nlmclnt->cl_xprt->addr)
static struct nlm_host * nlm_hosts[NLM_HOST_NRHASH];
static unsigned long next_gc;
static int nrhosts;
static DEFINE_MUTEX(nlm_host_mutex);
static void nlm_gc_hosts(void);
/*
* Find an NLM server handle in the cache. If there is none, create it.
*/
struct nlm_host *
nlmclnt_lookup_host(struct sockaddr_in *sin, int proto, int version)
{
return nlm_lookup_host(0, sin, proto, version);
}
/*
* Find an NLM client handle in the cache. If there is none, create it.
*/
struct nlm_host *
nlmsvc_lookup_host(struct svc_rqst *rqstp)
{
return nlm_lookup_host(1, &rqstp->rq_addr,
rqstp->rq_prot, rqstp->rq_vers);
}
/*
* Common host lookup routine for server & client
*/
struct nlm_host *
nlm_lookup_host(int server, struct sockaddr_in *sin,
int proto, int version)
{
struct nlm_host *host, **hp;
u32 addr;
int hash;
dprintk("lockd: nlm_lookup_host(%08x, p=%d, v=%d)\n",
(unsigned)(sin? ntohl(sin->sin_addr.s_addr) : 0), proto, version);
hash = NLM_ADDRHASH(sin->sin_addr.s_addr);
/* Lock hash table */
mutex_lock(&nlm_host_mutex);
if (time_after_eq(jiffies, next_gc))
nlm_gc_hosts();
for (hp = &nlm_hosts[hash]; (host = *hp) != 0; hp = &host->h_next) {
if (host->h_proto != proto)
continue;
if (host->h_version != version)
continue;
if (host->h_server != server)
continue;
if (nlm_cmp_addr(&host->h_addr, sin)) {
if (hp != nlm_hosts + hash) {
*hp = host->h_next;
host->h_next = nlm_hosts[hash];
nlm_hosts[hash] = host;
}
nlm_get_host(host);
mutex_unlock(&nlm_host_mutex);
return host;
}
}
/* Ooops, no host found, create it */
dprintk("lockd: creating host entry\n");
if (!(host = (struct nlm_host *) kmalloc(sizeof(*host), GFP_KERNEL)))
goto nohost;
memset(host, 0, sizeof(*host));
addr = sin->sin_addr.s_addr;
sprintf(host->h_name, "%u.%u.%u.%u", NIPQUAD(addr));
host->h_addr = *sin;
host->h_addr.sin_port = 0; /* ouch! */
host->h_version = version;
host->h_proto = proto;
host->h_rpcclnt = NULL;
mutex_init(&host->h_mutex);
host->h_nextrebind = jiffies + NLM_HOST_REBIND;
host->h_expires = jiffies + NLM_HOST_EXPIRE;
atomic_set(&host->h_count, 1);
init_waitqueue_head(&host->h_gracewait);
init_rwsem(&host->h_rwsem);
host->h_state = 0; /* pseudo NSM state */
host->h_nsmstate = 0; /* real NSM state */
host->h_server = server;
host->h_next = nlm_hosts[hash];
nlm_hosts[hash] = host;
INIT_LIST_HEAD(&host->h_lockowners);
spin_lock_init(&host->h_lock);
INIT_LIST_HEAD(&host->h_granted);
INIT_LIST_HEAD(&host->h_reclaim);
if (++nrhosts > NLM_HOST_MAX)
next_gc = 0;
nohost:
mutex_unlock(&nlm_host_mutex);
return host;
}
struct nlm_host *
nlm_find_client(void)
{
/* find a nlm_host for a client for which h_killed == 0.
* and return it
*/
int hash;
mutex_lock(&nlm_host_mutex);
for (hash = 0 ; hash < NLM_HOST_NRHASH; hash++) {
struct nlm_host *host, **hp;
for (hp = &nlm_hosts[hash]; (host = *hp) != 0; hp = &host->h_next) {
if (host->h_server &&
host->h_killed == 0) {
nlm_get_host(host);
mutex_unlock(&nlm_host_mutex);
return host;
}
}
}
mutex_unlock(&nlm_host_mutex);
return NULL;
}
/*
* Create the NLM RPC client for an NLM peer
*/
struct rpc_clnt *
nlm_bind_host(struct nlm_host *host)
{
struct rpc_clnt *clnt;
struct rpc_xprt *xprt;
dprintk("lockd: nlm_bind_host(%08x)\n",
(unsigned)ntohl(host->h_addr.sin_addr.s_addr));
/* Lock host handle */
mutex_lock(&host->h_mutex);
/* If we've already created an RPC client, check whether
* RPC rebind is required
*/
if ((clnt = host->h_rpcclnt) != NULL) {
xprt = clnt->cl_xprt;
if (time_after_eq(jiffies, host->h_nextrebind)) {
rpc_force_rebind(clnt);
host->h_nextrebind = jiffies + NLM_HOST_REBIND;
dprintk("lockd: next rebind in %ld jiffies\n",
host->h_nextrebind - jiffies);
}
} else {
xprt = xprt_create_proto(host->h_proto, &host->h_addr, NULL);
if (IS_ERR(xprt))
goto forgetit;
xprt_set_timeout(&xprt->timeout, 5, nlmsvc_timeout);
xprt->resvport = 1; /* NLM requires a reserved port */
/* Existing NLM servers accept AUTH_UNIX only */
clnt = rpc_new_client(xprt, host->h_name, &nlm_program,
host->h_version, RPC_AUTH_UNIX);
if (IS_ERR(clnt))
goto forgetit;
clnt->cl_autobind = 1; /* turn on pmap queries */
clnt->cl_softrtry = 1; /* All queries are soft */
host->h_rpcclnt = clnt;
}
mutex_unlock(&host->h_mutex);
return clnt;
forgetit:
printk("lockd: couldn't create RPC handle for %s\n", host->h_name);
mutex_unlock(&host->h_mutex);
return NULL;
}
/*
* Force a portmap lookup of the remote lockd port
*/
void
nlm_rebind_host(struct nlm_host *host)
{
dprintk("lockd: rebind host %s\n", host->h_name);
if (host->h_rpcclnt && time_after_eq(jiffies, host->h_nextrebind)) {
rpc_force_rebind(host->h_rpcclnt);
host->h_nextrebind = jiffies + NLM_HOST_REBIND;
}
}
/*
* Increment NLM host count
*/
struct nlm_host * nlm_get_host(struct nlm_host *host)
{
if (host) {
dprintk("lockd: get host %s\n", host->h_name);
atomic_inc(&host->h_count);
host->h_expires = jiffies + NLM_HOST_EXPIRE;
}
return host;
}
/*
* Release NLM host after use
*/
void nlm_release_host(struct nlm_host *host)
{
if (host != NULL) {
dprintk("lockd: release host %s\n", host->h_name);
BUG_ON(atomic_read(&host->h_count) < 0);
if (atomic_dec_and_test(&host->h_count)) {
BUG_ON(!list_empty(&host->h_lockowners));
BUG_ON(!list_empty(&host->h_granted));
BUG_ON(!list_empty(&host->h_reclaim));
}
}
}
/*
* Shut down the hosts module.
* Note that this routine is called only at server shutdown time.
*/
void
nlm_shutdown_hosts(void)
{
struct nlm_host *host;
int i;
dprintk("lockd: shutting down host module\n");
mutex_lock(&nlm_host_mutex);
/* First, make all hosts eligible for gc */
dprintk("lockd: nuking all hosts...\n");
for (i = 0; i < NLM_HOST_NRHASH; i++) {
for (host = nlm_hosts[i]; host; host = host->h_next)
host->h_expires = jiffies - 1;
}
/* Then, perform a garbage collection pass */
nlm_gc_hosts();
mutex_unlock(&nlm_host_mutex);
/* complain if any hosts are left */
if (nrhosts) {
printk(KERN_WARNING "lockd: couldn't shutdown host module!\n");
dprintk("lockd: %d hosts left:\n", nrhosts);
for (i = 0; i < NLM_HOST_NRHASH; i++) {
for (host = nlm_hosts[i]; host; host = host->h_next) {
dprintk(" %s (cnt %d use %d exp %ld)\n",
host->h_name, atomic_read(&host->h_count),
host->h_inuse, host->h_expires);
}
}
}
}
/*
* Garbage collect any unused NLM hosts.
* This GC combines reference counting for async operations with
* mark & sweep for resources held by remote clients.
*/
static void
nlm_gc_hosts(void)
{
struct nlm_host **q, *host;
struct rpc_clnt *clnt;
int i;
dprintk("lockd: host garbage collection\n");
for (i = 0; i < NLM_HOST_NRHASH; i++) {
for (host = nlm_hosts[i]; host; host = host->h_next)
host->h_inuse = 0;
}
/* Mark all hosts that hold locks, blocks or shares */
nlmsvc_mark_resources();
for (i = 0; i < NLM_HOST_NRHASH; i++) {
q = &nlm_hosts[i];
while ((host = *q) != NULL) {
if (atomic_read(&host->h_count) || host->h_inuse
|| time_before(jiffies, host->h_expires)) {
dprintk("nlm_gc_hosts skipping %s (cnt %d use %d exp %ld)\n",
host->h_name, atomic_read(&host->h_count),
host->h_inuse, host->h_expires);
q = &host->h_next;
continue;
}
dprintk("lockd: delete host %s\n", host->h_name);
*q = host->h_next;
/* Don't unmonitor hosts that have been invalidated */
if (host->h_monitored && !host->h_killed)
nsm_unmonitor(host);
if ((clnt = host->h_rpcclnt) != NULL) {
if (atomic_read(&clnt->cl_users)) {
printk(KERN_WARNING
"lockd: active RPC handle\n");
clnt->cl_dead = 1;
} else {
rpc_destroy_client(host->h_rpcclnt);
}
}
kfree(host);
nrhosts--;
}
}
next_gc = jiffies + NLM_HOST_COLLECT;
}