| Message ID | 20211104142545.40797-1-mlombard@redhat.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | target: iscsi: simplify the connection closing mechanism | expand |
Please ignore this. I realized this could introduce a race condition. Will send a V2 when ready. Maurizio On Thu, Nov 04, 2021 at 03:25:45PM +0100, Maurizio Lombardi wrote: > When the connection reinstatement is performed, the target driver > executes a complex scheme of complete()/wait_for_completion() that is not > really needed. > > Considering that: > > 1) The callers of iscsit_connection_reinstatement_rcfr() and > iscsit_cause_connection_reinstatement() hold a reference > to the conn structure. > > 2) iscsit_close_connection() will sleep when calling > iscsit_check_conn_usage_count() until the conn structure's refcount > reaches zero. > > we can optimize the driver the following way: > > * The threads that must sleep until the connection is closed > will all wait for the "conn_wait_comp" completion, > iscsit_close_connection() will then call complete_all() to wake them up. > No need to have multiple completion structures. > > * The conn_post_wait_comp completion is not necessary and can be removed > because iscsit_close_connection() sleeps until all the other threads > release the conn structure. > (see the iscsit_check_conn_usage_count() function) > > Signed-off-by: Maurizio Lombardi <mlombard@redhat.com> > --- > drivers/target/iscsi/iscsi_target.c | 31 +++++------------------ > drivers/target/iscsi/iscsi_target_erl0.c | 6 +---- > drivers/target/iscsi/iscsi_target_login.c | 2 -- > drivers/target/iscsi/iscsi_target_util.c | 3 --- > include/target/iscsi/iscsi_target_core.h | 4 --- > 5 files changed, 8 insertions(+), 38 deletions(-) > > diff --git a/drivers/target/iscsi/iscsi_target.c b/drivers/target/iscsi/iscsi_target.c > index 2c54c5d8412d..7df10cfcba2a 100644 > --- a/drivers/target/iscsi/iscsi_target.c > +++ b/drivers/target/iscsi/iscsi_target.c > @@ -4223,34 +4223,17 @@ int iscsit_close_connection( > > spin_unlock_bh(&sess->conn_lock); > > - /* > - * If connection reinstatement is being performed on this connection, > - * up the connection reinstatement semaphore that is being blocked on > - * in iscsit_cause_connection_reinstatement(). > - */ > spin_lock_bh(&conn->state_lock); > - if (atomic_read(&conn->sleep_on_conn_wait_comp)) { > - spin_unlock_bh(&conn->state_lock); > - complete(&conn->conn_wait_comp); > - wait_for_completion(&conn->conn_post_wait_comp); > - spin_lock_bh(&conn->state_lock); > - } > - > - /* > - * If connection reinstatement is being performed on this connection > - * by receiving a REMOVECONNFORRECOVERY logout request, up the > - * connection wait rcfr semaphore that is being blocked on > - * an iscsit_connection_reinstatement_rcfr(). > - */ > - if (atomic_read(&conn->connection_wait_rcfr)) { > - spin_unlock_bh(&conn->state_lock); > - complete(&conn->conn_wait_rcfr_comp); > - wait_for_completion(&conn->conn_post_wait_comp); > - spin_lock_bh(&conn->state_lock); > - } > atomic_set(&conn->connection_reinstatement, 1); > spin_unlock_bh(&conn->state_lock); > > + /* > + * If connection reinstatement is being performed on this connection, > + * up the connection reinstatement semaphore that is being blocked on > + * in iscsit_cause_connection_reinstatement() or > + * in iscsit_connection_reinstatement_rcfr() > + */ > + complete_all(&conn->conn_wait_comp); > /* > * If any other processes are accessing this connection pointer we > * must wait until they have completed. > diff --git a/drivers/target/iscsi/iscsi_target_erl0.c b/drivers/target/iscsi/iscsi_target_erl0.c > index 102c9cbf59f3..584e0a0b517d 100644 > --- a/drivers/target/iscsi/iscsi_target_erl0.c > +++ b/drivers/target/iscsi/iscsi_target_erl0.c > @@ -839,8 +839,7 @@ void iscsit_connection_reinstatement_rcfr(struct iscsi_conn *conn) > send_sig(SIGINT, conn->rx_thread, 1); > > sleep: > - wait_for_completion(&conn->conn_wait_rcfr_comp); > - complete(&conn->conn_post_wait_comp); > + wait_for_completion(&conn->conn_wait_comp); > } > > void iscsit_cause_connection_reinstatement(struct iscsi_conn *conn, int sleep) > @@ -871,12 +870,9 @@ void iscsit_cause_connection_reinstatement(struct iscsi_conn *conn, int sleep) > spin_unlock_bh(&conn->state_lock); > return; > } > - > - atomic_set(&conn->sleep_on_conn_wait_comp, 1); > spin_unlock_bh(&conn->state_lock); > > wait_for_completion(&conn->conn_wait_comp); > - complete(&conn->conn_post_wait_comp); > } > EXPORT_SYMBOL(iscsit_cause_connection_reinstatement); > > diff --git a/drivers/target/iscsi/iscsi_target_login.c b/drivers/target/iscsi/iscsi_target_login.c > index 1a9c50401bdb..982c23459272 100644 > --- a/drivers/target/iscsi/iscsi_target_login.c > +++ b/drivers/target/iscsi/iscsi_target_login.c > @@ -1096,9 +1096,7 @@ static struct iscsi_conn *iscsit_alloc_conn(struct iscsi_np *np) > INIT_LIST_HEAD(&conn->conn_cmd_list); > INIT_LIST_HEAD(&conn->immed_queue_list); > INIT_LIST_HEAD(&conn->response_queue_list); > - init_completion(&conn->conn_post_wait_comp); > init_completion(&conn->conn_wait_comp); > - init_completion(&conn->conn_wait_rcfr_comp); > init_completion(&conn->conn_waiting_on_uc_comp); > init_completion(&conn->conn_logout_comp); > init_completion(&conn->rx_half_close_comp); > diff --git a/drivers/target/iscsi/iscsi_target_util.c b/drivers/target/iscsi/iscsi_target_util.c > index 6dd5810e2af1..d7b1f9110d49 100644 > --- a/drivers/target/iscsi/iscsi_target_util.c > +++ b/drivers/target/iscsi/iscsi_target_util.c > @@ -824,9 +824,6 @@ struct iscsi_conn *iscsit_get_conn_from_cid_rcfr(struct iscsi_session *sess, u16 > list_for_each_entry(conn, &sess->sess_conn_list, conn_list) { > if (conn->cid == cid) { > iscsit_inc_conn_usage_count(conn); > - spin_lock(&conn->state_lock); > - atomic_set(&conn->connection_wait_rcfr, 1); > - spin_unlock(&conn->state_lock); > spin_unlock_bh(&sess->conn_lock); > return conn; > } > diff --git a/include/target/iscsi/iscsi_target_core.h b/include/target/iscsi/iscsi_target_core.h > index 1eccb2ac7d02..aeb8932507c2 100644 > --- a/include/target/iscsi/iscsi_target_core.h > +++ b/include/target/iscsi/iscsi_target_core.h > @@ -542,12 +542,8 @@ struct iscsi_conn { > atomic_t connection_exit; > atomic_t connection_recovery; > atomic_t connection_reinstatement; > - atomic_t connection_wait_rcfr; > - atomic_t sleep_on_conn_wait_comp; > atomic_t transport_failed; > - struct completion conn_post_wait_comp; > struct completion conn_wait_comp; > - struct completion conn_wait_rcfr_comp; > struct completion conn_waiting_on_uc_comp; > struct completion conn_logout_comp; > struct completion tx_half_close_comp; > -- > 2.27.0 >
diff --git a/drivers/target/iscsi/iscsi_target.c b/drivers/target/iscsi/iscsi_target.c index 2c54c5d8412d..7df10cfcba2a 100644 --- a/drivers/target/iscsi/iscsi_target.c +++ b/drivers/target/iscsi/iscsi_target.c @@ -4223,34 +4223,17 @@ int iscsit_close_connection( spin_unlock_bh(&sess->conn_lock); - /* - * If connection reinstatement is being performed on this connection, - * up the connection reinstatement semaphore that is being blocked on - * in iscsit_cause_connection_reinstatement(). - */ spin_lock_bh(&conn->state_lock); - if (atomic_read(&conn->sleep_on_conn_wait_comp)) { - spin_unlock_bh(&conn->state_lock); - complete(&conn->conn_wait_comp); - wait_for_completion(&conn->conn_post_wait_comp); - spin_lock_bh(&conn->state_lock); - } - - /* - * If connection reinstatement is being performed on this connection - * by receiving a REMOVECONNFORRECOVERY logout request, up the - * connection wait rcfr semaphore that is being blocked on - * an iscsit_connection_reinstatement_rcfr(). - */ - if (atomic_read(&conn->connection_wait_rcfr)) { - spin_unlock_bh(&conn->state_lock); - complete(&conn->conn_wait_rcfr_comp); - wait_for_completion(&conn->conn_post_wait_comp); - spin_lock_bh(&conn->state_lock); - } atomic_set(&conn->connection_reinstatement, 1); spin_unlock_bh(&conn->state_lock); + /* + * If connection reinstatement is being performed on this connection, + * up the connection reinstatement semaphore that is being blocked on + * in iscsit_cause_connection_reinstatement() or + * in iscsit_connection_reinstatement_rcfr() + */ + complete_all(&conn->conn_wait_comp); /* * If any other processes are accessing this connection pointer we * must wait until they have completed. diff --git a/drivers/target/iscsi/iscsi_target_erl0.c b/drivers/target/iscsi/iscsi_target_erl0.c index 102c9cbf59f3..584e0a0b517d 100644 --- a/drivers/target/iscsi/iscsi_target_erl0.c +++ b/drivers/target/iscsi/iscsi_target_erl0.c @@ -839,8 +839,7 @@ void iscsit_connection_reinstatement_rcfr(struct iscsi_conn *conn) send_sig(SIGINT, conn->rx_thread, 1); sleep: - wait_for_completion(&conn->conn_wait_rcfr_comp); - complete(&conn->conn_post_wait_comp); + wait_for_completion(&conn->conn_wait_comp); } void iscsit_cause_connection_reinstatement(struct iscsi_conn *conn, int sleep) @@ -871,12 +870,9 @@ void iscsit_cause_connection_reinstatement(struct iscsi_conn *conn, int sleep) spin_unlock_bh(&conn->state_lock); return; } - - atomic_set(&conn->sleep_on_conn_wait_comp, 1); spin_unlock_bh(&conn->state_lock); wait_for_completion(&conn->conn_wait_comp); - complete(&conn->conn_post_wait_comp); } EXPORT_SYMBOL(iscsit_cause_connection_reinstatement); diff --git a/drivers/target/iscsi/iscsi_target_login.c b/drivers/target/iscsi/iscsi_target_login.c index 1a9c50401bdb..982c23459272 100644 --- a/drivers/target/iscsi/iscsi_target_login.c +++ b/drivers/target/iscsi/iscsi_target_login.c @@ -1096,9 +1096,7 @@ static struct iscsi_conn *iscsit_alloc_conn(struct iscsi_np *np) INIT_LIST_HEAD(&conn->conn_cmd_list); INIT_LIST_HEAD(&conn->immed_queue_list); INIT_LIST_HEAD(&conn->response_queue_list); - init_completion(&conn->conn_post_wait_comp); init_completion(&conn->conn_wait_comp); - init_completion(&conn->conn_wait_rcfr_comp); init_completion(&conn->conn_waiting_on_uc_comp); init_completion(&conn->conn_logout_comp); init_completion(&conn->rx_half_close_comp); diff --git a/drivers/target/iscsi/iscsi_target_util.c b/drivers/target/iscsi/iscsi_target_util.c index 6dd5810e2af1..d7b1f9110d49 100644 --- a/drivers/target/iscsi/iscsi_target_util.c +++ b/drivers/target/iscsi/iscsi_target_util.c @@ -824,9 +824,6 @@ struct iscsi_conn *iscsit_get_conn_from_cid_rcfr(struct iscsi_session *sess, u16 list_for_each_entry(conn, &sess->sess_conn_list, conn_list) { if (conn->cid == cid) { iscsit_inc_conn_usage_count(conn); - spin_lock(&conn->state_lock); - atomic_set(&conn->connection_wait_rcfr, 1); - spin_unlock(&conn->state_lock); spin_unlock_bh(&sess->conn_lock); return conn; } diff --git a/include/target/iscsi/iscsi_target_core.h b/include/target/iscsi/iscsi_target_core.h index 1eccb2ac7d02..aeb8932507c2 100644 --- a/include/target/iscsi/iscsi_target_core.h +++ b/include/target/iscsi/iscsi_target_core.h @@ -542,12 +542,8 @@ struct iscsi_conn { atomic_t connection_exit; atomic_t connection_recovery; atomic_t connection_reinstatement; - atomic_t connection_wait_rcfr; - atomic_t sleep_on_conn_wait_comp; atomic_t transport_failed; - struct completion conn_post_wait_comp; struct completion conn_wait_comp; - struct completion conn_wait_rcfr_comp; struct completion conn_waiting_on_uc_comp; struct completion conn_logout_comp; struct completion tx_half_close_comp;
When the connection reinstatement is performed, the target driver executes a complex scheme of complete()/wait_for_completion() that is not really needed. Considering that: 1) The callers of iscsit_connection_reinstatement_rcfr() and iscsit_cause_connection_reinstatement() hold a reference to the conn structure. 2) iscsit_close_connection() will sleep when calling iscsit_check_conn_usage_count() until the conn structure's refcount reaches zero. we can optimize the driver the following way: * The threads that must sleep until the connection is closed will all wait for the "conn_wait_comp" completion, iscsit_close_connection() will then call complete_all() to wake them up. No need to have multiple completion structures. * The conn_post_wait_comp completion is not necessary and can be removed because iscsit_close_connection() sleeps until all the other threads release the conn structure. (see the iscsit_check_conn_usage_count() function) Signed-off-by: Maurizio Lombardi <mlombard@redhat.com> --- drivers/target/iscsi/iscsi_target.c | 31 +++++------------------ drivers/target/iscsi/iscsi_target_erl0.c | 6 +---- drivers/target/iscsi/iscsi_target_login.c | 2 -- drivers/target/iscsi/iscsi_target_util.c | 3 --- include/target/iscsi/iscsi_target_core.h | 4 --- 5 files changed, 8 insertions(+), 38 deletions(-)