linux-kernel - [PATCH 18/26] target/iscsi: Allocate session IDs from an IDA

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Date:   Thu, 21 Jun 2018 14:28:27 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     linux-kernel@...r.kernel.org
Cc:     Matthew Wilcox <willy@...radead.org>,
        "Nicholas A. Bellinger" <nab@...ux-iscsi.org>,
        Bart Van Assche <bart.vanassche@....com>,
        Hannes Reinecke <hare@...e.com>,
        Kees Cook <keescook@...omium.org>,
        Varun Prakash <varun@...lsio.com>,
        Sagi Grimberg <sagi@...mberg.me>,
        Philippe Ombredanne <pombredanne@...b.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "David S. Miller" <davem@...emloft.net>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        linux-scsi@...r.kernel.org, target-devel@...r.kernel.org
Subject: [PATCH 18/26] target/iscsi: Allocate session IDs from an IDA

Since the session is never looked up by ID, we can use the more
space-efficient IDA instead of the IDR.  I think I found a bug where
we never reuse session ID 0, but there may be a good reason for it,
so I've merely documented it in this patch.  Not reusing session ID 0
doesn't even leak memory.

Signed-off-by: Matthew Wilcox <willy@...radead.org>
---
 drivers/target/iscsi/iscsi_target.c       | 10 ++--------
 drivers/target/iscsi/iscsi_target.h       |  4 +---
 drivers/target/iscsi/iscsi_target_login.c | 20 ++++++--------------
 3 files changed, 9 insertions(+), 25 deletions(-)

diff --git a/drivers/target/iscsi/iscsi_target.c b/drivers/target/iscsi/iscsi_target.c
index 8e223799347a..94bad43c41ff 100644
--- a/drivers/target/iscsi/iscsi_target.c
+++ b/drivers/target/iscsi/iscsi_target.c
@@ -57,9 +57,8 @@ static DEFINE_SPINLOCK(tiqn_lock);
 static DEFINE_MUTEX(np_lock);
 
 static struct idr tiqn_idr;
-struct idr sess_idr;
+DEFINE_IDA(sess_ida);
 struct mutex auth_id_lock;
-spinlock_t sess_idr_lock;
 
 struct iscsit_global *iscsit_global;
 
@@ -700,9 +699,7 @@ static int __init iscsi_target_init_module(void)
 
 	spin_lock_init(&iscsit_global->ts_bitmap_lock);
 	mutex_init(&auth_id_lock);
-	spin_lock_init(&sess_idr_lock);
 	idr_init(&tiqn_idr);
-	idr_init(&sess_idr);
 
 	ret = target_register_template(&iscsi_ops);
 	if (ret)
@@ -4375,10 +4372,7 @@ int iscsit_close_session(struct iscsi_session *sess)
 	pr_debug("Decremented number of active iSCSI Sessions on"
 		" iSCSI TPG: %hu to %u\n", tpg->tpgt, tpg->nsessions);
 
-	spin_lock(&sess_idr_lock);
-	idr_remove(&sess_idr, sess->session_index);
-	spin_unlock(&sess_idr_lock);
-
+	ida_free(&sess_ida, sess->session_index);
 	kfree(sess->sess_ops);
 	sess->sess_ops = NULL;
 	spin_unlock_bh(&se_tpg->session_lock);
diff --git a/drivers/target/iscsi/iscsi_target.h b/drivers/target/iscsi/iscsi_target.h
index 42de1843aa40..48bac0acf8c7 100644
--- a/drivers/target/iscsi/iscsi_target.h
+++ b/drivers/target/iscsi/iscsi_target.h
@@ -55,9 +55,7 @@ extern struct kmem_cache *lio_ooo_cache;
 extern struct kmem_cache *lio_qr_cache;
 extern struct kmem_cache *lio_r2t_cache;
 
-extern struct idr sess_idr;
+extern struct ida sess_ida;
 extern struct mutex auth_id_lock;
-extern spinlock_t sess_idr_lock;
-
 
 #endif   /*** ISCSI_TARGET_H ***/
diff --git a/drivers/target/iscsi/iscsi_target_login.c b/drivers/target/iscsi/iscsi_target_login.c
index 99501785cdc1..561d2ad38989 100644
--- a/drivers/target/iscsi/iscsi_target_login.c
+++ b/drivers/target/iscsi/iscsi_target_login.c
@@ -336,22 +336,16 @@ static int iscsi_login_zero_tsih_s1(
 	timer_setup(&sess->time2retain_timer,
 		    iscsit_handle_time2retain_timeout, 0);
 
-	idr_preload(GFP_KERNEL);
-	spin_lock_bh(&sess_idr_lock);
-	ret = idr_alloc(&sess_idr, NULL, 0, 0, GFP_NOWAIT);
-	if (ret >= 0)
-		sess->session_index = ret;
-	spin_unlock_bh(&sess_idr_lock);
-	idr_preload_end();
-
+	ret = ida_alloc(&sess_ida, GFP_KERNEL);
 	if (ret < 0) {
-		pr_err("idr_alloc() for sess_idr failed\n");
+		pr_err("Session ID allocation failed %d\n", ret);
 		iscsit_tx_login_rsp(conn, ISCSI_STATUS_CLS_TARGET_ERR,
 				ISCSI_LOGIN_STATUS_NO_RESOURCES);
 		kfree(sess);
 		return -ENOMEM;
 	}
 
+	sess->session_index = ret;
 	sess->creation_time = get_jiffies_64();
 	/*
 	 * The FFP CmdSN window values will be allocated from the TPG's
@@ -1163,11 +1157,9 @@ void iscsi_target_login_sess_out(struct iscsi_conn *conn,
 		goto old_sess_out;
 	if (conn->sess->se_sess)
 		transport_free_session(conn->sess->se_sess);
-	if (conn->sess->session_index != 0) {
-		spin_lock_bh(&sess_idr_lock);
-		idr_remove(&sess_idr, conn->sess->session_index);
-		spin_unlock_bh(&sess_idr_lock);
-	}
+	/* Um, 0 is a valid ID.  I suppose we never free it? */
+	if (conn->sess->session_index != 0)
+		ida_free(&sess_ida, conn->sess->session_index);
 	kfree(conn->sess->sess_ops);
 	kfree(conn->sess);
 	conn->sess = NULL;
-- 
2.17.1