target: Drop iSCSI use of mutex around max_cmd_sn increment

In a performance profile, taking a mutex in iscsit_increment_maxcmdsn()
shows up very high.  However taking a mutex around "sess->max_cmd_sn += 1"
seems pretty silly: we're not serializing against other contexts in
any useful way.

I did a quick audit and there don't appear to be any other places that
use max_cmd_sn within the mutex more than once, so this lock can't be
providing any useful serialization.

(Get correct values for logging - fix whitespace damage)

Signed-off-by: Roland Dreier <roland@purestorage.com>
Signed-off-by: Spencer Baugh <sbaugh@catern.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

diff --git a/drivers/target/iscsi/iscsi_target.c b/drivers/target/iscsi/iscsi_target.c
index 986518c..e55f49c 100644 (file)
--- a/drivers/target/iscsi/iscsi_target.c
+++ b/drivers/target/iscsi/iscsi_target.c
@@ -2555,7 +2555,7 @@ static int iscsit_send_conn_drop_async_message(
        cmd->stat_sn            = conn->stat_sn++;
        hdr->statsn             = cpu_to_be32(cmd->stat_sn);
        hdr->exp_cmdsn          = cpu_to_be32(conn->sess->exp_cmd_sn);
-       hdr->max_cmdsn          = cpu_to_be32(conn->sess->max_cmd_sn);
+       hdr->max_cmdsn          = cpu_to_be32((u32) atomic_read(&conn->sess->max_cmd_sn));
        hdr->async_event        = ISCSI_ASYNC_MSG_DROPPING_CONNECTION;
        hdr->param1             = cpu_to_be16(cmd->logout_cid);
        hdr->param2             = cpu_to_be16(conn->sess->sess_ops->DefaultTime2Wait);
@@ -2627,7 +2627,7 @@ iscsit_build_datain_pdu(struct iscsi_cmd *cmd, struct iscsi_conn *conn,
                hdr->statsn             = cpu_to_be32(0xFFFFFFFF);
 
        hdr->exp_cmdsn          = cpu_to_be32(conn->sess->exp_cmd_sn);
-       hdr->max_cmdsn          = cpu_to_be32(conn->sess->max_cmd_sn);
+       hdr->max_cmdsn          = cpu_to_be32((u32) atomic_read(&conn->sess->max_cmd_sn));
        hdr->datasn             = cpu_to_be32(datain->data_sn);
        hdr->offset             = cpu_to_be32(datain->offset);
 
@@ -2838,7 +2838,7 @@ iscsit_build_logout_rsp(struct iscsi_cmd *cmd, struct iscsi_conn *conn,
 
        iscsit_increment_maxcmdsn(cmd, conn->sess);
        hdr->exp_cmdsn          = cpu_to_be32(conn->sess->exp_cmd_sn);
-       hdr->max_cmdsn          = cpu_to_be32(conn->sess->max_cmd_sn);
+       hdr->max_cmdsn          = cpu_to_be32((u32) atomic_read(&conn->sess->max_cmd_sn));
 
        pr_debug("Built Logout Response ITT: 0x%08x StatSN:"
                " 0x%08x Response: 0x%02x CID: %hu on CID: %hu\n",
@@ -2901,7 +2901,7 @@ iscsit_build_nopin_rsp(struct iscsi_cmd *cmd, struct iscsi_conn *conn,
                iscsit_increment_maxcmdsn(cmd, conn->sess);
 
        hdr->exp_cmdsn          = cpu_to_be32(conn->sess->exp_cmd_sn);
-       hdr->max_cmdsn          = cpu_to_be32(conn->sess->max_cmd_sn);
+       hdr->max_cmdsn          = cpu_to_be32((u32) atomic_read(&conn->sess->max_cmd_sn));
 
        pr_debug("Built NOPIN %s Response ITT: 0x%08x, TTT: 0x%08x,"
                " StatSN: 0x%08x, Length %u\n", (nopout_response) ?
@@ -3048,7 +3048,7 @@ static int iscsit_send_r2t(
        hdr->ttt                = cpu_to_be32(r2t->targ_xfer_tag);
        hdr->statsn             = cpu_to_be32(conn->stat_sn);
        hdr->exp_cmdsn          = cpu_to_be32(conn->sess->exp_cmd_sn);
-       hdr->max_cmdsn          = cpu_to_be32(conn->sess->max_cmd_sn);
+       hdr->max_cmdsn          = cpu_to_be32((u32) atomic_read(&conn->sess->max_cmd_sn));
        hdr->r2tsn              = cpu_to_be32(r2t->r2t_sn);
        hdr->data_offset        = cpu_to_be32(r2t->offset);
        hdr->data_length        = cpu_to_be32(r2t->xfer_len);
@@ -3201,7 +3201,7 @@ void iscsit_build_rsp_pdu(struct iscsi_cmd *cmd, struct iscsi_conn *conn,
 
        iscsit_increment_maxcmdsn(cmd, conn->sess);
        hdr->exp_cmdsn          = cpu_to_be32(conn->sess->exp_cmd_sn);
-       hdr->max_cmdsn          = cpu_to_be32(conn->sess->max_cmd_sn);
+       hdr->max_cmdsn          = cpu_to_be32((u32) atomic_read(&conn->sess->max_cmd_sn));
 
        pr_debug("Built SCSI Response, ITT: 0x%08x, StatSN: 0x%08x,"
                " Response: 0x%02x, SAM Status: 0x%02x, CID: %hu\n",
@@ -3320,7 +3320,7 @@ iscsit_build_task_mgt_rsp(struct iscsi_cmd *cmd, struct iscsi_conn *conn,
 
        iscsit_increment_maxcmdsn(cmd, conn->sess);
        hdr->exp_cmdsn          = cpu_to_be32(conn->sess->exp_cmd_sn);
-       hdr->max_cmdsn          = cpu_to_be32(conn->sess->max_cmd_sn);
+       hdr->max_cmdsn          = cpu_to_be32((u32) atomic_read(&conn->sess->max_cmd_sn));
 
        pr_debug("Built Task Management Response ITT: 0x%08x,"
                " StatSN: 0x%08x, Response: 0x%02x, CID: %hu\n",
@@ -3575,7 +3575,7 @@ iscsit_build_text_rsp(struct iscsi_cmd *cmd, struct iscsi_conn *conn,
         */
        cmd->maxcmdsn_inc = 0;
        hdr->exp_cmdsn = cpu_to_be32(conn->sess->exp_cmd_sn);
-       hdr->max_cmdsn = cpu_to_be32(conn->sess->max_cmd_sn);
+       hdr->max_cmdsn = cpu_to_be32((u32) atomic_read(&conn->sess->max_cmd_sn));
 
        pr_debug("Built Text Response: ITT: 0x%08x, TTT: 0x%08x, StatSN: 0x%08x,"
                " Length: %u, CID: %hu F: %d C: %d\n", cmd->init_task_tag,
@@ -3653,7 +3653,7 @@ iscsit_build_reject(struct iscsi_cmd *cmd, struct iscsi_conn *conn,
        cmd->stat_sn            = conn->stat_sn++;
        hdr->statsn             = cpu_to_be32(cmd->stat_sn);
        hdr->exp_cmdsn          = cpu_to_be32(conn->sess->exp_cmd_sn);
-       hdr->max_cmdsn          = cpu_to_be32(conn->sess->max_cmd_sn);
+       hdr->max_cmdsn          = cpu_to_be32((u32) atomic_read(&conn->sess->max_cmd_sn));
 
 }
 EXPORT_SYMBOL(iscsit_build_reject);

diff --git a/drivers/target/iscsi/iscsi_target_configfs.c b/drivers/target/iscsi/iscsi_target_configfs.c
index 05f1664..48f708b 100644 (file)
--- a/drivers/target/iscsi/iscsi_target_configfs.c
+++ b/drivers/target/iscsi/iscsi_target_configfs.c
@@ -656,6 +656,7 @@ static ssize_t lio_target_nacl_show_info(
        struct iscsi_conn *conn;
        struct se_session *se_sess;
        ssize_t rb = 0;
+       u32 max_cmd_sn;
 
        spin_lock_bh(&se_nacl->nacl_sess_lock);
        se_sess = se_nacl->nacl_sess;
@@ -703,11 +704,12 @@ static ssize_t lio_target_nacl_show_info(
                                " Values]-----------------------\n");
                rb += sprintf(page+rb, "  CmdSN/WR  :  CmdSN/WC  :  ExpCmdSN"
                                "  :  MaxCmdSN  :     ITT    :     TTT\n");
+               max_cmd_sn = (u32) atomic_read(&sess->max_cmd_sn);
                rb += sprintf(page+rb, " 0x%08x   0x%08x   0x%08x   0x%08x"
                                "   0x%08x   0x%08x\n",
                        sess->cmdsn_window,
-                       (sess->max_cmd_sn - sess->exp_cmd_sn) + 1,
-                       sess->exp_cmd_sn, sess->max_cmd_sn,
+                       (max_cmd_sn - sess->exp_cmd_sn) + 1,
+                       sess->exp_cmd_sn, max_cmd_sn,
                        sess->init_task_tag, sess->targ_xfer_tag);
                rb += sprintf(page+rb, "----------------------[iSCSI"
                                " Connections]-------------------------\n");

diff --git a/drivers/target/iscsi/iscsi_target_device.c b/drivers/target/iscsi/iscsi_target_device.c
index 5fabcd3..07d2ef6 100644 (file)
--- a/drivers/target/iscsi/iscsi_target_device.c
+++ b/drivers/target/iscsi/iscsi_target_device.c
@@ -47,7 +47,7 @@ void iscsit_determine_maxcmdsn(struct iscsi_session *sess)
         * core_set_queue_depth_for_node().
         */
        sess->cmdsn_window = se_nacl->queue_depth;
-       sess->max_cmd_sn = (sess->max_cmd_sn + se_nacl->queue_depth) - 1;
+       atomic_set(&sess->max_cmd_sn, (u32) atomic_read(&sess->max_cmd_sn) + se_nacl->queue_depth - 1);
 }
 
 void iscsit_increment_maxcmdsn(struct iscsi_cmd *cmd, struct iscsi_session *sess)
@@ -57,9 +57,6 @@ void iscsit_increment_maxcmdsn(struct iscsi_cmd *cmd, struct iscsi_session *sess
 
        cmd->maxcmdsn_inc = 1;
 
-       mutex_lock(&sess->cmdsn_mutex);
-       sess->max_cmd_sn += 1;
-       pr_debug("Updated MaxCmdSN to 0x%08x\n", sess->max_cmd_sn);
-       mutex_unlock(&sess->cmdsn_mutex);
+       pr_debug("Updated MaxCmdSN to 0x%08x\n", atomic_inc_return(&sess->max_cmd_sn));
 }
 EXPORT_SYMBOL(iscsit_increment_maxcmdsn);

diff --git a/drivers/target/iscsi/iscsi_target_login.c b/drivers/target/iscsi/iscsi_target_login.c
index 3d0fe4f..bd192f8 100644 (file)
--- a/drivers/target/iscsi/iscsi_target_login.c
+++ b/drivers/target/iscsi/iscsi_target_login.c
@@ -330,7 +330,7 @@ static int iscsi_login_zero_tsih_s1(
         * The FFP CmdSN window values will be allocated from the TPG's
         * Initiator Node's ACL once the login has been successfully completed.
         */
-       sess->max_cmd_sn        = be32_to_cpu(pdu->cmdsn);
+       atomic_set(&sess->max_cmd_sn, be32_to_cpu(pdu->cmdsn));
 
        sess->sess_ops = kzalloc(sizeof(struct iscsi_sess_ops), GFP_KERNEL);
        if (!sess->sess_ops) {

diff --git a/drivers/target/iscsi/iscsi_target_nego.c b/drivers/target/iscsi/iscsi_target_nego.c
index 8c02fa3..74d041e 100644 (file)
--- a/drivers/target/iscsi/iscsi_target_nego.c
+++ b/drivers/target/iscsi/iscsi_target_nego.c
@@ -340,7 +340,6 @@ static int iscsi_target_check_first_request(
 static int iscsi_target_do_tx_login_io(struct iscsi_conn *conn, struct iscsi_login *login)
 {
        u32 padding = 0;
-       struct iscsi_session *sess = conn->sess;
        struct iscsi_login_rsp *login_rsp;
 
        login_rsp = (struct iscsi_login_rsp *) login->rsp;
@@ -352,7 +351,7 @@ static int iscsi_target_do_tx_login_io(struct iscsi_conn *conn, struct iscsi_log
        login_rsp->itt                  = login->init_task_tag;
        login_rsp->statsn               = cpu_to_be32(conn->stat_sn++);
        login_rsp->exp_cmdsn            = cpu_to_be32(conn->sess->exp_cmd_sn);
-       login_rsp->max_cmdsn            = cpu_to_be32(conn->sess->max_cmd_sn);
+       login_rsp->max_cmdsn            = cpu_to_be32((u32) atomic_read(&conn->sess->max_cmd_sn));
 
        pr_debug("Sending Login Response, Flags: 0x%02x, ITT: 0x%08x,"
                " ExpCmdSN; 0x%08x, MaxCmdSN: 0x%08x, StatSN: 0x%08x, Length:"
@@ -367,10 +366,8 @@ static int iscsi_target_do_tx_login_io(struct iscsi_conn *conn, struct iscsi_log
                return -1;
 
        login->rsp_length               = 0;
-       mutex_lock(&sess->cmdsn_mutex);
-       login_rsp->exp_cmdsn            = cpu_to_be32(sess->exp_cmd_sn);
-       login_rsp->max_cmdsn            = cpu_to_be32(sess->max_cmd_sn);
-       mutex_unlock(&sess->cmdsn_mutex);
+       login_rsp->exp_cmdsn            = cpu_to_be32(login_rsp->exp_cmdsn);
+       login_rsp->max_cmdsn            = cpu_to_be32(login_rsp->max_cmdsn);
 
        return 0;
 }

diff --git a/drivers/target/iscsi/iscsi_target_tmr.c b/drivers/target/iscsi/iscsi_target_tmr.c
index cf59c39..11320df 100644 (file)
--- a/drivers/target/iscsi/iscsi_target_tmr.c
+++ b/drivers/target/iscsi/iscsi_target_tmr.c
@@ -50,7 +50,7 @@ u8 iscsit_tmr_abort_task(
                pr_err("Unable to locate RefTaskTag: 0x%08x on CID:"
                        " %hu.\n", hdr->rtt, conn->cid);
                return (iscsi_sna_gte(be32_to_cpu(hdr->refcmdsn), conn->sess->exp_cmd_sn) &&
-                       iscsi_sna_lte(be32_to_cpu(hdr->refcmdsn), conn->sess->max_cmd_sn)) ?
+                       iscsi_sna_lte(be32_to_cpu(hdr->refcmdsn), (u32) atomic_read(&conn->sess->max_cmd_sn))) ?
                        ISCSI_TMF_RSP_COMPLETE : ISCSI_TMF_RSP_NO_TASK;
        }
        if (ref_cmd->cmd_sn != be32_to_cpu(hdr->refcmdsn)) {

diff --git a/drivers/target/iscsi/iscsi_target_util.c b/drivers/target/iscsi/iscsi_target_util.c
index a2bff07..7df4fac 100644 (file)
--- a/drivers/target/iscsi/iscsi_target_util.c
+++ b/drivers/target/iscsi/iscsi_target_util.c
@@ -233,6 +233,7 @@ struct iscsi_r2t *iscsit_get_holder_for_r2tsn(
 
 static inline int iscsit_check_received_cmdsn(struct iscsi_session *sess, u32 cmdsn)
 {
+       u32 max_cmdsn;
        int ret;
 
        /*
@@ -241,10 +242,10 @@ static inline int iscsit_check_received_cmdsn(struct iscsi_session *sess, u32 cm
         * or order CmdSNs due to multiple connection sessions and/or
         * CRC failures.
         */
-       if (iscsi_sna_gt(cmdsn, sess->max_cmd_sn)) {
+       max_cmdsn = atomic_read(&sess->max_cmd_sn);
+       if (iscsi_sna_gt(cmdsn, max_cmdsn)) {
                pr_err("Received CmdSN: 0x%08x is greater than"
-                      " MaxCmdSN: 0x%08x, ignoring.\n", cmdsn,
-                      sess->max_cmd_sn);
+                      " MaxCmdSN: 0x%08x, ignoring.\n", cmdsn, max_cmdsn);
                ret = CMDSN_MAXCMDSN_OVERRUN;
 
        } else if (cmdsn == sess->exp_cmd_sn) {

diff --git a/include/target/iscsi/iscsi_target_core.h b/include/target/iscsi/iscsi_target_core.h
index ab46585..d4616ef 100644 (file)
--- a/include/target/iscsi/iscsi_target_core.h
+++ b/include/target/iscsi/iscsi_target_core.h
@@ -637,7 +637,7 @@ struct iscsi_session {
        /* session wide counter: expected command sequence number */
        u32                     exp_cmd_sn;
        /* session wide counter: maximum allowed command sequence number */
-       u32                     max_cmd_sn;
+       atomic_t                max_cmd_sn;
        struct list_head        sess_ooo_cmdsn_list;
 
        /* LIO specific session ID */