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Date: Wed, 22 Jul 2015 15:08:16 -0700
From: Spencer Baugh <sbaugh@...ern.com>
To: "Nicholas A. Bellinger" <nab@...ux-iscsi.org>,
Sagi Grimberg <sagig@...lanox.com>,
Christoph Hellwig <hch@....de>,
Bart Van Assche <bart.vanassche@...disk.com>,
Alexei Potashnik <alexei@...estorage.com>,
Andy Grover <agrover@...hat.com>,
Christophe Vu-Brugier <cvubrugier@...tmail.fm>,
Roland Dreier <roland@...estorage.com>,
Joern Engel <joern@...fs.org>,
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
James Bottomley <JBottomley@...n.com>,
Evgenii Lepikhin <johnlepikhin@...il.com>,
Hannes Reinecke <hare@...e.de>,
Al Viro <viro@...iv.linux.org.uk>,
linux-scsi@...r.kernel.org (open list:TARGET SUBSYSTEM),
target-devel@...r.kernel.org (open list:TARGET SUBSYSTEM),
linux-kernel@...r.kernel.org (open list)
Cc: Joern Engel <joern@...estorage.com>,
Spencer Baugh <Spencer.baugh@...estorage.com>,
Spencer Baugh <sbaugh@...ern.com>
Subject: [PATCH] target: Drop iSCSI use of mutex around max_cmd_sn increment
From: Roland Dreier <roland@...estorage.com>
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.
Signed-off-by: Roland Dreier <roland@...estorage.com>
Signed-off-by: Spencer Baugh <sbaugh@...ern.com>
---
drivers/target/iscsi/iscsi_target.c | 18 +++++++++---------
drivers/target/iscsi/iscsi_target_configfs.c | 4 ++--
drivers/target/iscsi/iscsi_target_device.c | 8 +++-----
drivers/target/iscsi/iscsi_target_login.c | 2 +-
drivers/target/iscsi/iscsi_target_nego.c | 9 +++------
drivers/target/iscsi/iscsi_target_tmr.c | 2 +-
drivers/target/iscsi/iscsi_target_util.c | 7 ++++---
include/target/iscsi/iscsi_target_core.h | 2 +-
8 files changed, 24 insertions(+), 28 deletions(-)
diff --git a/drivers/target/iscsi/iscsi_target.c b/drivers/target/iscsi/iscsi_target.c
index ebb1ece..635ec06c 100644
--- 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 c1898c8..29d5930 100644
--- a/drivers/target/iscsi/iscsi_target_configfs.c
+++ b/drivers/target/iscsi/iscsi_target_configfs.c
@@ -706,8 +706,8 @@ static ssize_t lio_target_nacl_show_info(
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,
+ ((u32) atomic_read(&sess->max_cmd_sn) - sess->exp_cmd_sn) + 1,
+ sess->exp_cmd_sn, (u32) atomic_read(&sess->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..a526904 100644
--- 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 +57,7 @@ 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);
+ atomic_inc(&sess->max_cmd_sn);
+ pr_debug("Updated MaxCmdSN to 0x%08x\n", atomic_read(&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
--- 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
--- 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
--- 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
--- 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 34117b8..11abe3a 100644
--- a/include/target/iscsi/iscsi_target_core.h
+++ b/include/target/iscsi/iscsi_target_core.h
@@ -635,7 +635,7 @@ 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 */
--
2.5.0.rc3
--
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