[SCTP]: Convert bind_addr_list locking to RCU

Since the sctp_sockaddr_entry is now RCU enabled as part of
the patch to synchronize sctp_localaddr_list, it makes sense to
change all handling of these entries to RCU.  This includes the
sctp_bind_addrs structure and it's list of bound addresses.

This list is currently protected by an external rw_lock and that
looks like an overkill.  There are only 2 writers to the list:
bind()/bindx() calls, and BH processing of ASCONF-ACK chunks.
These are already seriealized via the socket lock, so they will
not step on each other.  These are also relatively rare, so we
should be good with RCU.

The readers are varied and they are easily converted to RCU.

Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Sridhar Samdurala <sri@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 28 insertions, 70 deletions

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index a3acf78d06ba..772fbfb4bfda 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -367,14 +367,10 @@ SCTP_STATIC int sctp_do_bind(struct sock *sk, union sctp_addr *addr, int len)
 	if (!bp->port)
 		bp->port = inet_sk(sk)->num;
 
-	/* Add the address to the bind address list.  */
-	sctp_local_bh_disable();
-	sctp_write_lock(&ep->base.addr_lock);
-
-	/* Use GFP_ATOMIC since BHs are disabled.  */
+	/* Add the address to the bind address list.
+	 * Use GFP_ATOMIC since BHs will be disabled.
+	 */
 	ret = sctp_add_bind_addr(bp, addr, 1, GFP_ATOMIC);
-	sctp_write_unlock(&ep->base.addr_lock);
-	sctp_local_bh_enable();
 
 	/* Copy back into socket for getsockname() use. */
 	if (!ret) {
@@ -544,15 +540,12 @@ static int sctp_send_asconf_add_ip(struct sock		*sk,
 		if (i < addrcnt)
 			continue;
 
-		/* Use the first address in bind addr list of association as
-		 * Address Parameter of ASCONF CHUNK.
+		/* Use the first valid address in bind addr list of
+		 * association as Address Parameter of ASCONF CHUNK.
 		 */
-		sctp_read_lock(&asoc->base.addr_lock);
 		bp = &asoc->base.bind_addr;
 		p = bp->address_list.next;
 		laddr = list_entry(p, struct sctp_sockaddr_entry, list);
-		sctp_read_unlock(&asoc->base.addr_lock);
-
 		chunk = sctp_make_asconf_update_ip(asoc, &laddr->a, addrs,
 						   addrcnt, SCTP_PARAM_ADD_IP);
 		if (!chunk) {
@@ -567,8 +560,6 @@ static int sctp_send_asconf_add_ip(struct sock		*sk,
 		/* Add the new addresses to the bind address list with
 		 * use_as_src set to 0.
 		 */
-		sctp_local_bh_disable();
-		sctp_write_lock(&asoc->base.addr_lock);
 		addr_buf = addrs;
 		for (i = 0; i < addrcnt; i++) {
 			addr = (union sctp_addr *)addr_buf;
@@ -578,8 +569,6 @@ static int sctp_send_asconf_add_ip(struct sock		*sk,
 						    GFP_ATOMIC);
 			addr_buf += af->sockaddr_len;
 		}
-		sctp_write_unlock(&asoc->base.addr_lock);
-		sctp_local_bh_enable();
 	}
 
 out:
@@ -651,13 +640,7 @@ static int sctp_bindx_rem(struct sock *sk, struct sockaddr *addrs, int addrcnt)
 		 * socket routing and failover schemes. Refer to comments in
 		 * sctp_do_bind(). -daisy
 		 */
-		sctp_local_bh_disable();
-		sctp_write_lock(&ep->base.addr_lock);
-
-		retval = sctp_del_bind_addr(bp, sa_addr);
-
-		sctp_write_unlock(&ep->base.addr_lock);
-		sctp_local_bh_enable();
+		retval = sctp_del_bind_addr(bp, sa_addr, call_rcu);
 
 		addr_buf += af->sockaddr_len;
 err_bindx_rem:
@@ -748,14 +731,16 @@ static int sctp_send_asconf_del_ip(struct sock		*sk,
 		 * make sure that we do not delete all the addresses in the
 		 * association.
 		 */
-		sctp_read_lock(&asoc->base.addr_lock);
 		bp = &asoc->base.bind_addr;
 		laddr = sctp_find_unmatch_addr(bp, (union sctp_addr *)addrs,
 					       addrcnt, sp);
-		sctp_read_unlock(&asoc->base.addr_lock);
 		if (!laddr)
 			continue;
 
+		/* We do not need RCU protection throughout this loop
+		 * because this is done under a socket lock from the
+		 * setsockopt call.
+		 */
 		chunk = sctp_make_asconf_update_ip(asoc, laddr, addrs, addrcnt,
 						   SCTP_PARAM_DEL_IP);
 		if (!chunk) {
@@ -766,23 +751,16 @@ static int sctp_send_asconf_del_ip(struct sock		*sk,
 		/* Reset use_as_src flag for the addresses in the bind address
 		 * list that are to be deleted.
 		 */
-		sctp_local_bh_disable();
-		sctp_write_lock(&asoc->base.addr_lock);
 		addr_buf = addrs;
 		for (i = 0; i < addrcnt; i++) {
 			laddr = (union sctp_addr *)addr_buf;
 			af = sctp_get_af_specific(laddr->v4.sin_family);
-			list_for_each(pos1, &bp->address_list) {
-				saddr = list_entry(pos1,
-						   struct sctp_sockaddr_entry,
-						   list);
+			list_for_each_entry(saddr, &bp->address_list, list) {
 				if (sctp_cmp_addr_exact(&saddr->a, laddr))
 					saddr->use_as_src = 0;
 			}
 			addr_buf += af->sockaddr_len;
 		}
-		sctp_write_unlock(&asoc->base.addr_lock);
-		sctp_local_bh_enable();
 
 		/* Update the route and saddr entries for all the transports
 		 * as some of the addresses in the bind address list are
@@ -4057,11 +4035,9 @@ static int sctp_getsockopt_local_addrs_num_old(struct sock *sk, int len,
 					       int __user *optlen)
 {
 	sctp_assoc_t id;
-	struct list_head *pos;
 	struct sctp_bind_addr *bp;
 	struct sctp_association *asoc;
 	struct sctp_sockaddr_entry *addr;
-	rwlock_t *addr_lock;
 	int cnt = 0;
 
 	if (len < sizeof(sctp_assoc_t))
@@ -4078,17 +4054,13 @@ static int sctp_getsockopt_local_addrs_num_old(struct sock *sk, int len,
 	 */
 	if (0 == id) {
 		bp = &sctp_sk(sk)->ep->base.bind_addr;
-		addr_lock = &sctp_sk(sk)->ep->base.addr_lock;
 	} else {
 		asoc = sctp_id2assoc(sk, id);
 		if (!asoc)
 			return -EINVAL;
 		bp = &asoc->base.bind_addr;
-		addr_lock = &asoc->base.addr_lock;
 	}
 
-	sctp_read_lock(addr_lock);
-
 	/* If the endpoint is bound to 0.0.0.0 or ::0, count the valid
 	 * addresses from the global local address list.
 	 */
@@ -4115,12 +4087,14 @@ static int sctp_getsockopt_local_addrs_num_old(struct sock *sk, int len,
 		goto done;
 	}
 
-	list_for_each(pos, &bp->address_list) {
+	/* Protection on the bound address list is not needed,
+	 * since in the socket option context we hold the socket lock,
+	 * so there is no way that the bound address list can change.
+	 */
+	list_for_each_entry(addr, &bp->address_list, list) {
 		cnt ++;
 	}
-
 done:
-	sctp_read_unlock(addr_lock);
 	return cnt;
 }
 
@@ -4204,7 +4178,6 @@ static int sctp_getsockopt_local_addrs_old(struct sock *sk, int len,
 {
 	struct sctp_bind_addr *bp;
 	struct sctp_association *asoc;
-	struct list_head *pos;
 	int cnt = 0;
 	struct sctp_getaddrs_old getaddrs;
 	struct sctp_sockaddr_entry *addr;
@@ -4212,7 +4185,6 @@ static int sctp_getsockopt_local_addrs_old(struct sock *sk, int len,
 	union sctp_addr temp;
 	struct sctp_sock *sp = sctp_sk(sk);
 	int addrlen;
-	rwlock_t *addr_lock;
 	int err = 0;
 	void *addrs;
 	void *buf;
@@ -4234,13 +4206,11 @@ static int sctp_getsockopt_local_addrs_old(struct sock *sk, int len,
 	 */
 	if (0 == getaddrs.assoc_id) {
 		bp = &sctp_sk(sk)->ep->base.bind_addr;
-		addr_lock = &sctp_sk(sk)->ep->base.addr_lock;
 	} else {
 		asoc = sctp_id2assoc(sk, getaddrs.assoc_id);
 		if (!asoc)
 			return -EINVAL;
 		bp = &asoc->base.bind_addr;
-		addr_lock = &asoc->base.addr_lock;
 	}
 
 	to = getaddrs.addrs;
@@ -4254,8 +4224,6 @@ static int sctp_getsockopt_local_addrs_old(struct sock *sk, int len,
 	if (!addrs)
 		return -ENOMEM;
 
-	sctp_read_lock(addr_lock);
-
 	/* If the endpoint is bound to 0.0.0.0 or ::0, get the valid
 	 * addresses from the global local address list.
 	 */
@@ -4271,8 +4239,11 @@ static int sctp_getsockopt_local_addrs_old(struct sock *sk, int len,
 	}
 
 	buf = addrs;
-	list_for_each(pos, &bp->address_list) {
-		addr = list_entry(pos, struct sctp_sockaddr_entry, list);
+	/* Protection on the bound address list is not needed since
+	 * in the socket option context we hold a socket lock and
+	 * thus the bound address list can't change.
+	 */
+	list_for_each_entry(addr, &bp->address_list, list) {
 		memcpy(&temp, &addr->a, sizeof(temp));
 		sctp_get_pf_specific(sk->sk_family)->addr_v4map(sp, &temp);
 		addrlen = sctp_get_af_specific(temp.sa.sa_family)->sockaddr_len;
@@ -4284,8 +4255,6 @@ static int sctp_getsockopt_local_addrs_old(struct sock *sk, int len,
 	}
 
 copy_getaddrs:
-	sctp_read_unlock(addr_lock);
-
 	/* copy the entire address list into the user provided space */
 	if (copy_to_user(to, addrs, bytes_copied)) {
 		err = -EFAULT;
@@ -4307,7 +4276,6 @@ static int sctp_getsockopt_local_addrs(struct sock *sk, int len,
 {
 	struct sctp_bind_addr *bp;
 	struct sctp_association *asoc;
-	struct list_head *pos;
 	int cnt = 0;
 	struct sctp_getaddrs getaddrs;
 	struct sctp_sockaddr_entry *addr;
@@ -4315,7 +4283,6 @@ static int sctp_getsockopt_local_addrs(struct sock *sk, int len,
 	union sctp_addr temp;
 	struct sctp_sock *sp = sctp_sk(sk);
 	int addrlen;
-	rwlock_t *addr_lock;
 	int err = 0;
 	size_t space_left;
 	int bytes_copied = 0;
@@ -4336,13 +4303,11 @@ static int sctp_getsockopt_local_addrs(struct sock *sk, int len,
 	 */
 	if (0 == getaddrs.assoc_id) {
 		bp = &sctp_sk(sk)->ep->base.bind_addr;
-		addr_lock = &sctp_sk(sk)->ep->base.addr_lock;
 	} else {
 		asoc = sctp_id2assoc(sk, getaddrs.assoc_id);
 		if (!asoc)
 			return -EINVAL;
 		bp = &asoc->base.bind_addr;
-		addr_lock = &asoc->base.addr_lock;
 	}
 
 	to = optval + offsetof(struct sctp_getaddrs,addrs);
@@ -4352,8 +4317,6 @@ static int sctp_getsockopt_local_addrs(struct sock *sk, int len,
 	if (!addrs)
 		return -ENOMEM;
 
-	sctp_read_lock(addr_lock);
-
 	/* If the endpoint is bound to 0.0.0.0 or ::0, get the valid
 	 * addresses from the global local address list.
 	 */
@@ -4365,21 +4328,24 @@ static int sctp_getsockopt_local_addrs(struct sock *sk, int len,
 						space_left, &bytes_copied);
 			if (cnt < 0) {
 				err = cnt;
-				goto error_lock;
+				goto out;
 			}
 			goto copy_getaddrs;
 		}
 	}
 
 	buf = addrs;
-	list_for_each(pos, &bp->address_list) {
-		addr = list_entry(pos, struct sctp_sockaddr_entry, list);
+	/* Protection on the bound address list is not needed since
+	 * in the socket option context we hold a socket lock and
+	 * thus the bound address list can't change.
+	 */
+	list_for_each_entry(addr, &bp->address_list, list) {
 		memcpy(&temp, &addr->a, sizeof(temp));
 		sctp_get_pf_specific(sk->sk_family)->addr_v4map(sp, &temp);
 		addrlen = sctp_get_af_specific(temp.sa.sa_family)->sockaddr_len;
 		if (space_left < addrlen) {
 			err =  -ENOMEM; /*fixme: right error?*/
-			goto error_lock;
+			goto out;
 		}
 		memcpy(buf, &temp, addrlen);
 		buf += addrlen;
@@ -4389,8 +4355,6 @@ static int sctp_getsockopt_local_addrs(struct sock *sk, int len,
 	}
 
 copy_getaddrs:
-	sctp_read_unlock(addr_lock);
-
 	if (copy_to_user(to, addrs, bytes_copied)) {
 		err = -EFAULT;
 		goto out;
@@ -4401,12 +4365,6 @@ copy_getaddrs:
 	}
 	if (put_user(bytes_copied, optlen))
 		err = -EFAULT;
-
-	goto out;
-
-error_lock:
-	sctp_read_unlock(addr_lock);
-
 out:
 	kfree(addrs);
 	return err;