[PATCH net-next 02/12] net/smc: switch connections to alternate link

Karsten Graul
2020-05-04T12:19:16Z

Add smc_switch_conns() to switch all connections from a link that is
going down. Find an other link to switch the connections to, and
switch each connection to the new link. smc_switch_cursor() updates the
cursors of a connection to the state of the last successfully sent CDC
message. When there is no link to switch to, terminate the link group.
Call smc_switch_conns() when a link is going down.
And with the possibility that links of connections can switch adapt CDC
and TX functions to detect and handle link switches.

Signed-off-by: Karsten Graul <kgraul@linux.ibm.com>
Reviewed-by: Ursula Braun <ubraun@linux.ibm.com>
---
net/smc/smc_cdc.c | 18 ++++++-
net/smc/smc_cdc.h | 1 +
net/smc/smc_core.c | 132 ++++++++++++++++++++++++++++++++++++++++++++-
net/smc/smc_core.h | 2 +
net/smc/smc_llc.c | 6 +--
net/smc/smc_tx.c | 12 ++++-
6 files changed, 162 insertions(+), 9 deletions(-)

diff --git a/net/smc/smc_cdc.c b/net/smc/smc_cdc.c
index c5e33296e55c..3ca986066f32 100644
--- a/net/smc/smc_cdc.c
+++ b/net/smc/smc_cdc.c
@@ -56,11 +56,11 @@ static void smc_cdc_tx_handler(struct smc_wr_tx_pend_priv *pnd_snd,
}

int smc_cdc_get_free_slot(struct smc_connection *conn,
+ struct smc_link *link,
struct smc_wr_buf **wr_buf,
struct smc_rdma_wr **wr_rdma_buf,
struct smc_cdc_tx_pend **pend)
{
- struct smc_link *link = conn->lnk;
int rc;

rc = smc_wr_tx_get_free_slot(link, smc_cdc_tx_handler, wr_buf,
@@ -119,13 +119,27 @@ static int smcr_cdc_get_slot_and_msg_send(struct smc_connection *conn)
{
struct smc_cdc_tx_pend *pend;
struct smc_wr_buf *wr_buf;
+ struct smc_link *link;
+ bool again = false;
int rc;

- rc = smc_cdc_get_free_slot(conn, &wr_buf, NULL, &pend);
+again:
+ link = conn->lnk;
+ rc = smc_cdc_get_free_slot(conn, link, &wr_buf, NULL, &pend);
if (rc)
return rc;

spin_lock_bh(&conn->send_lock);
+ if (link != conn->lnk) {
+ /* link of connection changed, try again one time*/
+ spin_unlock_bh(&conn->send_lock);
+ smc_wr_tx_put_slot(link,
+ (struct smc_wr_tx_pend_priv *)pend);
+ if (again)
+ return -ENOLINK;
+ again = true;
+ goto again;
+ }
rc = smc_cdc_msg_send(conn, wr_buf, pend);
spin_unlock_bh(&conn->send_lock);
return rc;
diff --git a/net/smc/smc_cdc.h b/net/smc/smc_cdc.h
index 861dc24c588c..42246b4bdcc9 100644
--- a/net/smc/smc_cdc.h
+++ b/net/smc/smc_cdc.h
@@ -304,6 +304,7 @@ struct smc_cdc_tx_pend {
};

int smc_cdc_get_free_slot(struct smc_connection *conn,
+ struct smc_link *link,
struct smc_wr_buf **wr_buf,
struct smc_rdma_wr **wr_rdma_buf,
struct smc_cdc_tx_pend **pend);
diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c
index 32a6cadc5c1f..21bc1ec07e99 100644
--- a/net/smc/smc_core.c
+++ b/net/smc/smc_core.c
@@ -432,6 +432,135 @@ static int smc_lgr_create(struct smc_sock *smc, struct smc_init_info *ini)
return rc;
}

+static int smc_write_space(struct smc_connection *conn)
+{
+ int buffer_len = conn->peer_rmbe_size;
+ union smc_host_cursor prod;
+ union smc_host_cursor cons;
+ int space;
+
+ smc_curs_copy(&prod, &conn->local_tx_ctrl.prod, conn);
+ smc_curs_copy(&cons, &conn->local_rx_ctrl.cons, conn);
+ /* determine rx_buf space */
+ space = buffer_len - smc_curs_diff(buffer_len, &cons, &prod);
+ return space;
+}
+
+static int smc_switch_cursor(struct smc_sock *smc)
+{
+ struct smc_connection *conn = &smc->conn;
+ union smc_host_cursor cons, fin;
+ int rc = 0;
+ int diff;
+
+ smc_curs_copy(&conn->tx_curs_sent, &conn->tx_curs_fin, conn);
+ smc_curs_copy(&fin, &conn->local_tx_ctrl_fin, conn);
+ /* set prod cursor to old state, enforce tx_rdma_writes() */
+ smc_curs_copy(&conn->local_tx_ctrl.prod, &fin, conn);
+ smc_curs_copy(&cons, &conn->local_rx_ctrl.cons, conn);
+
+ if (smc_curs_comp(conn->peer_rmbe_size, &cons, &fin) < 0) {
+ /* cons cursor advanced more than fin, and prod was set
+ * fin above, so now prod is smaller than cons. Fix that.
+ */
+ diff = smc_curs_diff(conn->peer_rmbe_size, &fin, &cons);
+ smc_curs_add(conn->sndbuf_desc->len,
+ &conn->tx_curs_sent, diff);
+ smc_curs_add(conn->sndbuf_desc->len,
+ &conn->tx_curs_fin, diff);
+
+ smp_mb__before_atomic();
+ atomic_add(diff, &conn->sndbuf_space);
+ smp_mb__after_atomic();
+
+ smc_curs_add(conn->peer_rmbe_size,
+ &conn->local_tx_ctrl.prod, diff);
+ smc_curs_add(conn->peer_rmbe_size,
+ &conn->local_tx_ctrl_fin, diff);
+ }
+ /* recalculate, value is used by tx_rdma_writes() */
+ atomic_set(&smc->conn.peer_rmbe_space, smc_write_space(conn));
+
+ if (smc->sk.sk_state != SMC_INIT &&
+ smc->sk.sk_state != SMC_CLOSED) {
+ /* tbd: call rc = smc_cdc_get_slot_and_msg_send(conn); */
+ if (!rc) {
+ schedule_delayed_work(&conn->tx_work, 0);
+ smc->sk.sk_data_ready(&smc->sk);
+ }
+ }
+ return rc;
+}
+
+struct smc_link *smc_switch_conns(struct smc_link_group *lgr,
+ struct smc_link *from_lnk, bool is_dev_err)
+{
+ struct smc_link *to_lnk = NULL;
+ struct smc_connection *conn;
+ struct smc_sock *smc;
+ struct rb_node *node;
+ int i, rc = 0;
+
+ /* link is inactive, wake up tx waiters */
+ smc_wr_wakeup_tx_wait(from_lnk);
+
+ for (i = 0; i < SMC_LINKS_PER_LGR_MAX; i++) {
+ if (lgr->lnk[i].state != SMC_LNK_ACTIVE ||
+ i == from_lnk->link_idx)
+ continue;
+ if (is_dev_err && from_lnk->smcibdev == lgr->lnk[i].smcibdev &&
+ from_lnk->ibport == lgr->lnk[i].ibport) {
+ continue;
+ }
+ to_lnk = &lgr->lnk[i];
+ break;
+ }
+ if (!to_lnk) {
+ smc_lgr_terminate_sched(lgr);
+ return NULL;
+ }
+again:
+ read_lock_bh(&lgr->conns_lock);
+ for (node = rb_first(&lgr->conns_all); node; node = rb_next(node)) {
+ conn = rb_entry(node, struct smc_connection, alert_node);
+ if (conn->lnk != from_lnk)
+ continue;
+ smc = container_of(conn, struct smc_sock, conn);
+ /* conn->lnk not yet set in SMC_INIT state */
+ if (smc->sk.sk_state == SMC_INIT)
+ continue;
+ if (smc->sk.sk_state == SMC_CLOSED ||
+ smc->sk.sk_state == SMC_PEERCLOSEWAIT1 ||
+ smc->sk.sk_state == SMC_PEERCLOSEWAIT2 ||
+ smc->sk.sk_state == SMC_APPFINCLOSEWAIT ||
+ smc->sk.sk_state == SMC_APPCLOSEWAIT1 ||
+ smc->sk.sk_state == SMC_APPCLOSEWAIT2 ||
+ smc->sk.sk_state == SMC_PEERFINCLOSEWAIT ||
+ smc->sk.sk_state == SMC_PEERABORTWAIT ||
+ smc->sk.sk_state == SMC_PROCESSABORT) {
+ spin_lock_bh(&conn->send_lock);
+ conn->lnk = to_lnk;
+ spin_unlock_bh(&conn->send_lock);
+ continue;
+ }
+ sock_hold(&smc->sk);
+ read_unlock_bh(&lgr->conns_lock);
+ /* avoid race with smcr_tx_sndbuf_nonempty() */
+ spin_lock_bh(&conn->send_lock);
+ conn->lnk = to_lnk;
+ rc = smc_switch_cursor(smc);
+ spin_unlock_bh(&conn->send_lock);
+ sock_put(&smc->sk);
+ if (rc) {
+ smcr_link_down_cond_sched(to_lnk);
+ return NULL;
+ }
+ goto again;
+ }
+ read_unlock_bh(&lgr->conns_lock);
+ return to_lnk;
+}
+
static void smcr_buf_unuse(struct smc_buf_desc *rmb_desc,
struct smc_link_group *lgr)
{
@@ -943,8 +1072,7 @@ static void smcr_link_down(struct smc_link *lnk)
return;

smc_ib_modify_qp_reset(lnk);
- to_lnk = NULL;
- /* tbd: call to_lnk = smc_switch_conns(lgr, lnk, true); */
+ to_lnk = smc_switch_conns(lgr, lnk, true);
if (!to_lnk) { /* no backup link available */
smcr_link_clear(lnk);
return;
diff --git a/net/smc/smc_core.h b/net/smc/smc_core.h
index 7fe53feb9dc4..584f11230c4f 100644
--- a/net/smc/smc_core.h
+++ b/net/smc/smc_core.h
@@ -380,6 +380,8 @@ void smcr_link_clear(struct smc_link *lnk);
int smcr_buf_map_lgr(struct smc_link *lnk);
int smcr_buf_reg_lgr(struct smc_link *lnk);
int smcr_link_reg_rmb(struct smc_link *link, struct smc_buf_desc *rmb_desc);
+struct smc_link *smc_switch_conns(struct smc_link_group *lgr,
+ struct smc_link *from_lnk, bool is_dev_err);
void smcr_link_down_cond(struct smc_link *lnk);
void smcr_link_down_cond_sched(struct smc_link *lnk);

diff --git a/net/smc/smc_llc.c b/net/smc/smc_llc.c
index 7675ccd6f3c3..8d2368accbad 100644
--- a/net/smc/smc_llc.c
+++ b/net/smc/smc_llc.c
@@ -933,7 +933,7 @@ static void smc_llc_delete_asym_link(struct smc_link_group *lgr)
return; /* no asymmetric link */
if (!smc_link_downing(&lnk_asym->state))
return;
- /* tbd: lnk_new = smc_switch_conns(lgr, lnk_asym, false); */
+ lnk_new = smc_switch_conns(lgr, lnk_asym, false);
smc_wr_tx_wait_no_pending_sends(lnk_asym);
if (!lnk_new)
goto out_free;
@@ -1195,7 +1195,7 @@ static void smc_llc_process_cli_delete_link(struct smc_link_group *lgr)
smc_llc_send_message(lnk, &qentry->msg); /* response */

if (smc_link_downing(&lnk_del->state)) {
- /* tbd: call smc_switch_conns(lgr, lnk_del, false); */
+ smc_switch_conns(lgr, lnk_del, false);
smc_wr_tx_wait_no_pending_sends(lnk_del);
}
smcr_link_clear(lnk_del);
@@ -1245,7 +1245,7 @@ static void smc_llc_process_srv_delete_link(struct smc_link_group *lgr)
goto out; /* asymmetric link already deleted */

if (smc_link_downing(&lnk_del->state)) {
- /* tbd: call smc_switch_conns(lgr, lnk_del, false); */
+ smc_switch_conns(lgr, lnk_del, false);
smc_wr_tx_wait_no_pending_sends(lnk_del);
}
if (!list_empty(&lgr->list)) {
diff --git a/net/smc/smc_tx.c b/net/smc/smc_tx.c
index 417204572a69..54ba0443847e 100644
--- a/net/smc/smc_tx.c
+++ b/net/smc/smc_tx.c
@@ -482,12 +482,13 @@ static int smc_tx_rdma_writes(struct smc_connection *conn,
static int smcr_tx_sndbuf_nonempty(struct smc_connection *conn)
{
struct smc_cdc_producer_flags *pflags = &conn->local_tx_ctrl.prod_flags;
+ struct smc_link *link = conn->lnk;
struct smc_rdma_wr *wr_rdma_buf;
struct smc_cdc_tx_pend *pend;
struct smc_wr_buf *wr_buf;
int rc;

- rc = smc_cdc_get_free_slot(conn, &wr_buf, &wr_rdma_buf, &pend);
+ rc = smc_cdc_get_free_slot(conn, link, &wr_buf, &wr_rdma_buf, &pend);
if (rc < 0) {
if (rc == -EBUSY) {
struct smc_sock *smc =
@@ -505,10 +506,17 @@ static int smcr_tx_sndbuf_nonempty(struct smc_connection *conn)
}

spin_lock_bh(&conn->send_lock);
+ if (link != conn->lnk) {
+ /* link of connection changed, tx_work will restart */
+ smc_wr_tx_put_slot(link,
+ (struct smc_wr_tx_pend_priv *)pend);
+ rc = -ENOLINK;
+ goto out_unlock;
+ }
if (!pflags->urg_data_present) {
rc = smc_tx_rdma_writes(conn, wr_rdma_buf);
if (rc) {
- smc_wr_tx_put_slot(conn->lnk,
+ smc_wr_tx_put_slot(link,
(struct smc_wr_tx_pend_priv *)pend);
goto out_unlock;
}
--
2.17.1