From f835be1355dd887437d0f6f728a0091583f97f30 Mon Sep 17 00:00:00 2001
From: Bart Van Assche <bart.vanassche@sandisk.com>
Date: Sun, 3 May 2015 09:09:38 +0200
Subject: [PATCH] scst_sysfs: Do not suspend I/O for LUN management

The previous patches make it safe to remove a LUN from
sess_tgt_dev_list while I/O is in progress. Hence this patch
that allows LUN management without suspending I/O.

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
---
 scst/src/scst_lib.c   | 28 ++++++++++++++++++++++++++++
 scst/src/scst_sysfs.c |  9 +--------
 scst/src/scst_targ.c  |  1 +
 3 files changed, 30 insertions(+), 8 deletions(-)

diff --git a/scst/src/scst_lib.c b/scst/src/scst_lib.c
index dfb888fa7..8123abe69 100644
--- a/scst/src/scst_lib.c
+++ b/scst/src/scst_lib.c
@@ -4308,6 +4308,23 @@ out:
 	return acg_dev;
 }
 
+static int scst_tgt_devs_cmds(struct list_head *tgt_dev_list)
+{
+	struct scst_tgt_dev *tgt_dev;
+	int res = 0;
+
+	list_for_each_entry(tgt_dev, tgt_dev_list, extra_tgt_dev_list_entry)
+		res += atomic_read(&tgt_dev->tgt_dev_cmd_count);
+
+	return res;
+}
+
+static void scst_wait_for_tgt_devs(struct list_head *tgt_dev_list)
+{
+	while (scst_tgt_devs_cmds(tgt_dev_list) > 0)
+		mdelay(100);
+}
+
 int scst_acg_del_lun(struct scst_acg *acg, uint64_t lun,
 	bool gen_scst_report_luns_changed)
 {
@@ -4329,6 +4346,12 @@ int scst_acg_del_lun(struct scst_acg *acg, uint64_t lun,
 	if (gen_scst_report_luns_changed)
 		scst_report_luns_changed(acg);
 
+	mutex_unlock(&scst_mutex);
+
+	scst_wait_for_tgt_devs(&tgt_dev_list);
+
+	mutex_lock(&scst_mutex);
+
 	list_for_each_entry_safe(tgt_dev, tt, &tgt_dev_list,
 				 extra_tgt_dev_list_entry) {
 		scst_free_tgt_dev(tgt_dev);
@@ -4377,6 +4400,11 @@ int scst_acg_repl_lun(struct scst_acg *acg, struct kobject *parent,
 			}
 		}
 	}
+	mutex_unlock(&scst_mutex);
+
+	scst_wait_for_tgt_devs(&tgt_dev_list);
+
+	mutex_lock(&scst_mutex);
 	list_for_each_entry_safe(tgt_dev, tt, &tgt_dev_list,
 				 extra_tgt_dev_list_entry) {
 		scst_free_tgt_dev(tgt_dev);
diff --git a/scst/src/scst_sysfs.c b/scst/src/scst_sysfs.c
index e47da42c4..2165aace7 100644
--- a/scst/src/scst_sysfs.c
+++ b/scst/src/scst_sysfs.c
@@ -1374,13 +1374,9 @@ static int __scst_process_luns_mgmt_store(char *buffer,
 		goto out;
 	}
 
-	res = scst_suspend_activity(SCST_SUSPEND_TIMEOUT_USER);
-	if (res != 0)
-		goto out;
-
 	res = mutex_lock_interruptible(&scst_mutex);
 	if (res != 0)
-		goto out_resume;
+		goto out;
 
 	/* Check if tgt and acg not already freed while we were coming here */
 	if (scst_check_tgt_acg_ptrs(tgt, acg) != 0)
@@ -1488,9 +1484,6 @@ static int __scst_process_luns_mgmt_store(char *buffer,
 out_unlock:
 	mutex_unlock(&scst_mutex);
 
-out_resume:
-	scst_resume_activity();
-
 out:
 	TRACE_EXIT_RES(res);
 	return res;
diff --git a/scst/src/scst_targ.c b/scst/src/scst_targ.c
index d8cf6e33c..77e9ee343 100644
--- a/scst/src/scst_targ.c
+++ b/scst/src/scst_targ.c
@@ -3971,6 +3971,7 @@ static int scst_pre_xmit_response1(struct scst_cmd *cmd)
 		 * Those counters protect from not getting too long processing
 		 * latency, so we should decrement them after cmd completed.
 		 */
+		smp_mb__before_atomic_dec();
 		atomic_dec(&cmd->tgt_dev->tgt_dev_cmd_count);
 #ifdef CONFIG_SCST_PER_DEVICE_CMD_COUNT_LIMIT
 		atomic_dec(&cmd->dev->dev_cmd_count);