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svc: Change sk_inuse to a kref
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Change the atomic_t reference count to a kref and move it to the
transport indepenent svc_xprt structure. Change the reference count
wrapper names to be generic.

Signed-off-by: Tom Tucker <tom@opengridcomputing.com>
Acked-by: Neil Brown <neilb@suse.de>
Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
Reviewed-by: Greg Banks <gnb@sgi.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
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Tom Tucker authored and J. Bruce Fields committed Feb 1, 2008
1 parent d7c9f1e commit e1b3157
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Showing 4 changed files with 87 additions and 76 deletions.
8 changes: 8 additions & 0 deletions include/linux/sunrpc/svc_xprt.h
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,7 @@
#define SUNRPC_SVC_XPRT_H

#include <linux/sunrpc/svc.h>
#include <linux/module.h>

struct svc_xprt_ops {
struct svc_xprt *(*xpo_create)(struct svc_serv *,
Expand All @@ -34,11 +35,18 @@ struct svc_xprt_class {
struct svc_xprt {
struct svc_xprt_class *xpt_class;
struct svc_xprt_ops *xpt_ops;
struct kref xpt_ref;
};

int svc_reg_xprt_class(struct svc_xprt_class *);
void svc_unreg_xprt_class(struct svc_xprt_class *);
void svc_xprt_init(struct svc_xprt_class *, struct svc_xprt *);
int svc_create_xprt(struct svc_serv *, char *, unsigned short, int);
void svc_xprt_put(struct svc_xprt *xprt);

static inline void svc_xprt_get(struct svc_xprt *xprt)
{
kref_get(&xprt->xpt_ref);
}

#endif /* SUNRPC_SVC_XPRT_H */
1 change: 0 additions & 1 deletion include/linux/sunrpc/svcsock.h
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Original file line number Diff line number Diff line change
Expand Up @@ -24,7 +24,6 @@ struct svc_sock {

struct svc_pool * sk_pool; /* current pool iff queued */
struct svc_serv * sk_server; /* service for this socket */
atomic_t sk_inuse; /* use count */
unsigned long sk_flags;
#define SK_BUSY 0 /* enqueued/receiving */
#define SK_CONN 1 /* conn pending */
Expand Down
16 changes: 16 additions & 0 deletions net/sunrpc/svc_xprt.c
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Original file line number Diff line number Diff line change
Expand Up @@ -70,6 +70,21 @@ void svc_unreg_xprt_class(struct svc_xprt_class *xcl)
}
EXPORT_SYMBOL_GPL(svc_unreg_xprt_class);

static void svc_xprt_free(struct kref *kref)
{
struct svc_xprt *xprt =
container_of(kref, struct svc_xprt, xpt_ref);
struct module *owner = xprt->xpt_class->xcl_owner;
xprt->xpt_ops->xpo_free(xprt);
module_put(owner);
}

void svc_xprt_put(struct svc_xprt *xprt)
{
kref_put(&xprt->xpt_ref, svc_xprt_free);
}
EXPORT_SYMBOL_GPL(svc_xprt_put);

/*
* Called by transport drivers to initialize the transport independent
* portion of the transport instance.
Expand All @@ -79,6 +94,7 @@ void svc_xprt_init(struct svc_xprt_class *xcl, struct svc_xprt *xprt)
memset(xprt, 0, sizeof(*xprt));
xprt->xpt_class = xcl;
xprt->xpt_ops = xcl->xcl_ops;
kref_init(&xprt->xpt_ref);
}
EXPORT_SYMBOL_GPL(svc_xprt_init);

Expand Down
138 changes: 63 additions & 75 deletions net/sunrpc/svcsock.c
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Original file line number Diff line number Diff line change
Expand Up @@ -66,8 +66,8 @@
* after a clear, the socket must be read/accepted
* if this succeeds, it must be set again.
* SK_CLOSE can set at any time. It is never cleared.
* sk_inuse contains a bias of '1' until SK_DEAD is set.
* so when sk_inuse hits zero, we know the socket is dead
* xpt_ref contains a bias of '1' until SK_DEAD is set.
* so when xprt_ref hits zero, we know the transport is dead
* and no-one is using it.
* SK_DEAD can only be set while SK_BUSY is held which ensures
* no other thread will be using the socket or will try to
Expand Down Expand Up @@ -285,7 +285,7 @@ svc_sock_enqueue(struct svc_sock *svsk)
"svc_sock_enqueue: server %p, rq_sock=%p!\n",
rqstp, rqstp->rq_sock);
rqstp->rq_sock = svsk;
atomic_inc(&svsk->sk_inuse);
svc_xprt_get(&svsk->sk_xprt);
rqstp->rq_reserved = serv->sv_max_mesg;
atomic_add(rqstp->rq_reserved, &svsk->sk_reserved);
BUG_ON(svsk->sk_pool != pool);
Expand Down Expand Up @@ -316,7 +316,7 @@ svc_sock_dequeue(struct svc_pool *pool)
list_del_init(&svsk->sk_ready);

dprintk("svc: socket %p dequeued, inuse=%d\n",
svsk->sk_sk, atomic_read(&svsk->sk_inuse));
svsk->sk_sk, atomic_read(&svsk->sk_xprt.xpt_ref.refcount));

return svsk;
}
Expand Down Expand Up @@ -359,19 +359,6 @@ void svc_reserve(struct svc_rqst *rqstp, int space)
}
}

/*
* Release a socket after use.
*/
static inline void
svc_sock_put(struct svc_sock *svsk)
{
if (atomic_dec_and_test(&svsk->sk_inuse)) {
BUG_ON(!test_bit(SK_DEAD, &svsk->sk_flags));
module_put(svsk->sk_xprt.xpt_class->xcl_owner);
svsk->sk_xprt.xpt_ops->xpo_free(&svsk->sk_xprt);
}
}

static void
svc_sock_release(struct svc_rqst *rqstp)
{
Expand All @@ -398,7 +385,7 @@ svc_sock_release(struct svc_rqst *rqstp)
svc_reserve(rqstp, 0);
rqstp->rq_sock = NULL;

svc_sock_put(svsk);
svc_xprt_put(&svsk->sk_xprt);
}

/*
Expand Down Expand Up @@ -1127,50 +1114,6 @@ static struct svc_xprt *svc_tcp_accept(struct svc_xprt *xprt)
return NULL;
}

/*
* Make sure that we don't have too many active connections. If we
* have, something must be dropped.
*
* There's no point in trying to do random drop here for DoS
* prevention. The NFS clients does 1 reconnect in 15 seconds. An
* attacker can easily beat that.
*
* The only somewhat efficient mechanism would be if drop old
* connections from the same IP first. But right now we don't even
* record the client IP in svc_sock.
*/
static void svc_check_conn_limits(struct svc_serv *serv)
{
if (serv->sv_tmpcnt > (serv->sv_nrthreads+3)*20) {
struct svc_sock *svsk = NULL;
spin_lock_bh(&serv->sv_lock);
if (!list_empty(&serv->sv_tempsocks)) {
if (net_ratelimit()) {
/* Try to help the admin */
printk(KERN_NOTICE "%s: too many open TCP "
"sockets, consider increasing the "
"number of nfsd threads\n",
serv->sv_name);
}
/*
* Always select the oldest socket. It's not fair,
* but so is life
*/
svsk = list_entry(serv->sv_tempsocks.prev,
struct svc_sock,
sk_list);
set_bit(SK_CLOSE, &svsk->sk_flags);
atomic_inc(&svsk->sk_inuse);
}
spin_unlock_bh(&serv->sv_lock);

if (svsk) {
svc_sock_enqueue(svsk);
svc_sock_put(svsk);
}
}
}

/*
* Receive data from a TCP socket.
*/
Expand Down Expand Up @@ -1496,6 +1439,50 @@ svc_sock_update_bufs(struct svc_serv *serv)
spin_unlock_bh(&serv->sv_lock);
}

/*
* Make sure that we don't have too many active connections. If we
* have, something must be dropped.
*
* There's no point in trying to do random drop here for DoS
* prevention. The NFS clients does 1 reconnect in 15 seconds. An
* attacker can easily beat that.
*
* The only somewhat efficient mechanism would be if drop old
* connections from the same IP first. But right now we don't even
* record the client IP in svc_sock.
*/
static void svc_check_conn_limits(struct svc_serv *serv)
{
if (serv->sv_tmpcnt > (serv->sv_nrthreads+3)*20) {
struct svc_sock *svsk = NULL;
spin_lock_bh(&serv->sv_lock);
if (!list_empty(&serv->sv_tempsocks)) {
if (net_ratelimit()) {
/* Try to help the admin */
printk(KERN_NOTICE "%s: too many open TCP "
"sockets, consider increasing the "
"number of nfsd threads\n",
serv->sv_name);
}
/*
* Always select the oldest socket. It's not fair,
* but so is life
*/
svsk = list_entry(serv->sv_tempsocks.prev,
struct svc_sock,
sk_list);
set_bit(SK_CLOSE, &svsk->sk_flags);
svc_xprt_get(&svsk->sk_xprt);
}
spin_unlock_bh(&serv->sv_lock);

if (svsk) {
svc_sock_enqueue(svsk);
svc_xprt_put(&svsk->sk_xprt);
}
}
}

/*
* Receive the next request on any socket. This code is carefully
* organised not to touch any cachelines in the shared svc_serv
Expand Down Expand Up @@ -1556,7 +1543,7 @@ svc_recv(struct svc_rqst *rqstp, long timeout)
spin_lock_bh(&pool->sp_lock);
if ((svsk = svc_sock_dequeue(pool)) != NULL) {
rqstp->rq_sock = svsk;
atomic_inc(&svsk->sk_inuse);
svc_xprt_get(&svsk->sk_xprt);
rqstp->rq_reserved = serv->sv_max_mesg;
atomic_add(rqstp->rq_reserved, &svsk->sk_reserved);
} else {
Expand Down Expand Up @@ -1605,7 +1592,8 @@ svc_recv(struct svc_rqst *rqstp, long timeout)
svc_sock_received(svsk);
} else {
dprintk("svc: server %p, pool %u, socket %p, inuse=%d\n",
rqstp, pool->sp_id, svsk, atomic_read(&svsk->sk_inuse));
rqstp, pool->sp_id, svsk,
atomic_read(&svsk->sk_xprt.xpt_ref.refcount));
len = svsk->sk_xprt.xpt_ops->xpo_recvfrom(rqstp);
dprintk("svc: got len=%d\n", len);
}
Expand Down Expand Up @@ -1702,9 +1690,10 @@ svc_age_temp_sockets(unsigned long closure)

if (!test_and_set_bit(SK_OLD, &svsk->sk_flags))
continue;
if (atomic_read(&svsk->sk_inuse) > 1 || test_bit(SK_BUSY, &svsk->sk_flags))
if (atomic_read(&svsk->sk_xprt.xpt_ref.refcount) > 1
|| test_bit(SK_BUSY, &svsk->sk_flags))
continue;
atomic_inc(&svsk->sk_inuse);
svc_xprt_get(&svsk->sk_xprt);
list_move(le, &to_be_aged);
set_bit(SK_CLOSE, &svsk->sk_flags);
set_bit(SK_DETACHED, &svsk->sk_flags);
Expand All @@ -1722,7 +1711,7 @@ svc_age_temp_sockets(unsigned long closure)

/* a thread will dequeue and close it soon */
svc_sock_enqueue(svsk);
svc_sock_put(svsk);
svc_xprt_put(&svsk->sk_xprt);
}

mod_timer(&serv->sv_temptimer, jiffies + svc_conn_age_period * HZ);
Expand Down Expand Up @@ -1767,7 +1756,6 @@ static struct svc_sock *svc_setup_socket(struct svc_serv *serv,
svsk->sk_odata = inet->sk_data_ready;
svsk->sk_owspace = inet->sk_write_space;
svsk->sk_server = serv;
atomic_set(&svsk->sk_inuse, 1);
svsk->sk_lastrecv = get_seconds();
spin_lock_init(&svsk->sk_lock);
INIT_LIST_HEAD(&svsk->sk_deferred);
Expand Down Expand Up @@ -1953,10 +1941,10 @@ svc_delete_socket(struct svc_sock *svsk)
* is about to be destroyed (in svc_destroy).
*/
if (!test_and_set_bit(SK_DEAD, &svsk->sk_flags)) {
BUG_ON(atomic_read(&svsk->sk_inuse)<2);
atomic_dec(&svsk->sk_inuse);
BUG_ON(atomic_read(&svsk->sk_xprt.xpt_ref.refcount) < 2);
if (test_bit(SK_TEMP, &svsk->sk_flags))
serv->sv_tmpcnt--;
svc_xprt_put(&svsk->sk_xprt);
}

spin_unlock_bh(&serv->sv_lock);
Expand All @@ -1969,10 +1957,10 @@ static void svc_close_socket(struct svc_sock *svsk)
/* someone else will have to effect the close */
return;

atomic_inc(&svsk->sk_inuse);
svc_xprt_get(&svsk->sk_xprt);
svc_delete_socket(svsk);
clear_bit(SK_BUSY, &svsk->sk_flags);
svc_sock_put(svsk);
svc_xprt_put(&svsk->sk_xprt);
}

void svc_force_close_socket(struct svc_sock *svsk)
Expand All @@ -1998,7 +1986,7 @@ static void svc_revisit(struct cache_deferred_req *dreq, int too_many)
struct svc_sock *svsk;

if (too_many) {
svc_sock_put(dr->svsk);
svc_xprt_put(&dr->svsk->sk_xprt);
kfree(dr);
return;
}
Expand All @@ -2010,7 +1998,7 @@ static void svc_revisit(struct cache_deferred_req *dreq, int too_many)
spin_unlock(&svsk->sk_lock);
set_bit(SK_DEFERRED, &svsk->sk_flags);
svc_sock_enqueue(svsk);
svc_sock_put(svsk);
svc_xprt_put(&svsk->sk_xprt);
}

static struct cache_deferred_req *
Expand Down Expand Up @@ -2040,7 +2028,7 @@ svc_defer(struct cache_req *req)
dr->argslen = rqstp->rq_arg.len >> 2;
memcpy(dr->args, rqstp->rq_arg.head[0].iov_base-skip, dr->argslen<<2);
}
atomic_inc(&rqstp->rq_sock->sk_inuse);
svc_xprt_get(rqstp->rq_xprt);
dr->svsk = rqstp->rq_sock;

dr->handle.revisit = svc_revisit;
Expand Down

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