target: Convert se_portal_group->tpg_lun_list[] to RCU hlist

This patch converts the fixed size se_portal_group->tpg_lun_list[]
to use modern RCU with hlist_head in order to support an arbitary
number of se_lun ports per target endpoint.

It includes dropping core_tpg_alloc_lun() from core_dev_add_lun(),
and calling it directly from target_fabric_make_lun() to allocate
a new se_lun.  And add a new target_fabric_port_release() configfs
item callback to invoke kfree_rcu() to release memory during
se_lun->lun_group shutdown.

Also now that se_node_acl->lun_entry_hlist is using RCU, convert
existing tpg_lun_lock to struct mutex so core_tpg_add_node_to_devs()
can perform RCU updater logic without releasing ->tpg_lun_mutex.

Also, drop core_tpg_clear_object_luns() and it's single consumer
in iscsi-target, which is duplicating TPG LUN shutdown logic and
is current code results in a NOP.

Finally, sbp-target and xen-scsiback fabric driver conversions are
included, which are required due to the non-standard way they use
->tpg_lun_hlist.

Reviewed-by: Hannes Reinecke <hare@suse.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Sagi Grimberg <sagig@mellanox.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Chris Boot <bootc@bootc.net>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

2 files changed, 43 insertions, 56 deletions

diff --git a/drivers/target/sbp/sbp_target.c b/drivers/target/sbp/sbp_target.c
index 5d7755edc668..47fb12fbaf47 100644
--- a/drivers/target/sbp/sbp_target.c
+++ b/drivers/target/sbp/sbp_target.c
@@ -108,13 +108,13 @@ static struct sbp_session *sbp_session_find_by_guid(
 }
 
 static struct sbp_login_descriptor *sbp_login_find_by_lun(
-                struct sbp_session *session, struct se_lun *lun)
+                struct sbp_session *session, u32 unpacked_lun)
 {
         struct sbp_login_descriptor *login, *found = NULL;
 
         spin_lock_bh(&session->lock);
         list_for_each_entry(login, &session->login_list, link) {
-                if (login->lun == lun)
+                if (login->login_lun == unpacked_lun)
                         found = login;
         }
         spin_unlock_bh(&session->lock);
@@ -124,7 +124,7 @@ static struct sbp_login_descriptor *sbp_login_find_by_lun(
 
 static int sbp_login_count_all_by_lun(
                 struct sbp_tpg *tpg,
-                struct se_lun *lun,
+                u32 unpacked_lun,
                 int exclusive)
 {
         struct se_session *se_sess;
@@ -138,7 +138,7 @@ static int sbp_login_count_all_by_lun(
 
                 spin_lock_bh(&sess->lock);
                 list_for_each_entry(login, &sess->login_list, link) {
-                        if (login->lun != lun)
+                        if (login->login_lun != unpacked_lun)
                                 continue;
 
                         if (!exclusive || login->exclusive)
@@ -174,23 +174,23 @@ static struct sbp_login_descriptor *sbp_login_find_by_id(
         return found;
 }
 
-static struct se_lun *sbp_get_lun_from_tpg(struct sbp_tpg *tpg, int lun)
+static u32 sbp_get_lun_from_tpg(struct sbp_tpg *tpg, u32 login_lun, int *err)
 {
         struct se_portal_group *se_tpg = &tpg->se_tpg;
         struct se_lun *se_lun;
 
-        if (lun >= TRANSPORT_MAX_LUNS_PER_TPG)
-                return ERR_PTR(-EINVAL);
-
-        spin_lock(&se_tpg->tpg_lun_lock);
-        se_lun = se_tpg->tpg_lun_list[lun];
-
-        if (se_lun->lun_status != TRANSPORT_LUN_STATUS_ACTIVE)
-                se_lun = ERR_PTR(-ENODEV);
-
-        spin_unlock(&se_tpg->tpg_lun_lock);
+        rcu_read_lock();
+        hlist_for_each_entry_rcu(se_lun, &se_tpg->tpg_lun_hlist, link) {
+                if (se_lun->unpacked_lun == login_lun) {
+                        rcu_read_unlock();
+                        *err = 0;
+                        return login_lun;
+                }
+        }
+        rcu_read_unlock();
 
-        return se_lun;
+        *err = -ENODEV;
+        return login_lun;
 }
 
 static struct sbp_session *sbp_session_create(
@@ -294,17 +294,16 @@ static void sbp_management_request_login(
 {
         struct sbp_tport *tport = agent->tport;
         struct sbp_tpg *tpg = tport->tpg;
-        struct se_lun *se_lun;
-        int ret;
-        u64 guid;
         struct sbp_session *sess;
         struct sbp_login_descriptor *login;
         struct sbp_login_response_block *response;
-        int login_response_len;
+        u64 guid;
+        u32 unpacked_lun;
+        int login_response_len, ret;
 
-        se_lun = sbp_get_lun_from_tpg(tpg,
-                        LOGIN_ORB_LUN(be32_to_cpu(req->orb.misc)));
-        if (IS_ERR(se_lun)) {
+        unpacked_lun = sbp_get_lun_from_tpg(tpg,
+                        LOGIN_ORB_LUN(be32_to_cpu(req->orb.misc)), &ret);
+        if (ret) {
                 pr_notice("login to unknown LUN: %d\n",
                         LOGIN_ORB_LUN(be32_to_cpu(req->orb.misc)));
 
@@ -325,11 +324,11 @@ static void sbp_management_request_login(
         }
 
         pr_notice("mgt_agent LOGIN to LUN %d from %016llx\n",
-                se_lun->unpacked_lun, guid);
+                unpacked_lun, guid);
 
         sess = sbp_session_find_by_guid(tpg, guid);
         if (sess) {
-                login = sbp_login_find_by_lun(sess, se_lun);
+                login = sbp_login_find_by_lun(sess, unpacked_lun);
                 if (login) {
                         pr_notice("initiator already logged-in\n");
 
@@ -357,7 +356,7 @@ static void sbp_management_request_login(
          * reject with access_denied if any logins present
          */
         if (LOGIN_ORB_EXCLUSIVE(be32_to_cpu(req->orb.misc)) &&
-                        sbp_login_count_all_by_lun(tpg, se_lun, 0)) {
+                        sbp_login_count_all_by_lun(tpg, unpacked_lun, 0)) {
                 pr_warn("refusing exclusive login with other active logins\n");
 
                 req->status.status = cpu_to_be32(
@@ -370,7 +369,7 @@ static void sbp_management_request_login(
          * check exclusive bit in any existing login descriptor
          * reject with access_denied if any exclusive logins present
          */
-        if (sbp_login_count_all_by_lun(tpg, se_lun, 1)) {
+        if (sbp_login_count_all_by_lun(tpg, unpacked_lun, 1)) {
                 pr_warn("refusing login while another exclusive login present\n");
 
                 req->status.status = cpu_to_be32(
@@ -383,7 +382,7 @@ static void sbp_management_request_login(
          * check we haven't exceeded the number of allowed logins
          * reject with resources_unavailable if we have
          */
-        if (sbp_login_count_all_by_lun(tpg, se_lun, 0) >=
+        if (sbp_login_count_all_by_lun(tpg, unpacked_lun, 0) >=
                         tport->max_logins_per_lun) {
                 pr_warn("max number of logins reached\n");
 
@@ -439,7 +438,7 @@ static void sbp_management_request_login(
         }
 
         login->sess = sess;
-        login->lun = se_lun;
+        login->login_lun = unpacked_lun;
         login->status_fifo_addr = sbp2_pointer_to_addr(&req->orb.status_fifo);
         login->exclusive = LOGIN_ORB_EXCLUSIVE(be32_to_cpu(req->orb.misc));
         login->login_id = atomic_inc_return(&login_id);
@@ -601,7 +600,7 @@ static void sbp_management_request_logout(
         }
 
         pr_info("mgt_agent LOGOUT from LUN %d session %d\n",
-                login->lun->unpacked_lun, login->login_id);
+                login->login_lun, login->login_id);
 
         if (req->node_addr != login->sess->node_id) {
                 pr_warn("logout from different node ID\n");
@@ -1227,7 +1226,7 @@ static void sbp_handle_command(struct sbp_target_request *req)
                 goto err;
         }
 
-        unpacked_lun = req->login->lun->unpacked_lun;
+        unpacked_lun = req->login->login_lun;
         sbp_calc_data_length_direction(req, &data_length, &data_dir);
 
         pr_debug("sbp_handle_command ORB:0x%llx unpacked_lun:%d data_len:%d data_dir:%d\n",
@@ -1826,25 +1825,21 @@ static int sbp_check_stop_free(struct se_cmd *se_cmd)
 
 static int sbp_count_se_tpg_luns(struct se_portal_group *tpg)
 {
-        int i, count = 0;
-
-        spin_lock(&tpg->tpg_lun_lock);
-        for (i = 0; i < TRANSPORT_MAX_LUNS_PER_TPG; i++) {
-                struct se_lun *se_lun = tpg->tpg_lun_list[i];
-
-                if (se_lun->lun_status == TRANSPORT_LUN_STATUS_FREE)
-                        continue;
+        struct se_lun *lun;
+        int count = 0;
 
+        rcu_read_lock();
+        hlist_for_each_entry_rcu(lun, &tpg->tpg_lun_hlist, link)
                 count++;
-        }
-        spin_unlock(&tpg->tpg_lun_lock);
+        rcu_read_unlock();
 
         return count;
 }
 
 static int sbp_update_unit_directory(struct sbp_tport *tport)
 {
-        int num_luns, num_entries, idx = 0, mgt_agt_addr, ret, i;
+        struct se_lun *lun;
+        int num_luns, num_entries, idx = 0, mgt_agt_addr, ret;
         u32 *data;
 
         if (tport->unit_directory.data) {
@@ -1906,28 +1901,20 @@ static int sbp_update_unit_directory(struct sbp_tport *tport)
         /* unit unique ID (leaf is just after LUNs) */
         data[idx++] = 0x8d000000 | (num_luns + 1);
 
-        spin_lock(&tport->tpg->se_tpg.tpg_lun_lock);
-        for (i = 0; i < TRANSPORT_MAX_LUNS_PER_TPG; i++) {
-                struct se_lun *se_lun = tport->tpg->se_tpg.tpg_lun_list[i];
+        rcu_read_lock();
+        hlist_for_each_entry_rcu(lun, &tport->tpg->se_tpg.tpg_lun_hlist, link) {
                 struct se_device *dev;
                 int type;
 
-                if (se_lun->lun_status == TRANSPORT_LUN_STATUS_FREE)
-                        continue;
-
-                spin_unlock(&tport->tpg->se_tpg.tpg_lun_lock);
-
-                dev = se_lun->lun_se_dev;
+                dev = lun->lun_se_dev;
                 type = dev->transport->get_device_type(dev);
 
                 /* logical_unit_number */
                 data[idx++] = 0x14000000 |
                         ((type << 16) & 0x1f0000) |
-                        (se_lun->unpacked_lun & 0xffff);
-
-                spin_lock(&tport->tpg->se_tpg.tpg_lun_lock);
+                        (lun->unpacked_lun & 0xffff);
         }
-        spin_unlock(&tport->tpg->se_tpg.tpg_lun_lock);
+        rcu_read_unlock();
 
         /* unit unique ID leaf */
         data[idx++] = 2 << 16;
diff --git a/drivers/target/sbp/sbp_target.h b/drivers/target/sbp/sbp_target.h
index e1b0b84f7379..73bcb1208832 100644
--- a/drivers/target/sbp/sbp_target.h
+++ b/drivers/target/sbp/sbp_target.h
@@ -125,7 +125,7 @@ struct sbp_login_descriptor {
         struct sbp_session *sess;
         struct list_head link;
 
-        struct se_lun *lun;
+        u32 login_lun;
 
         u64 status_fifo_addr;
         int exclusive;