[PATCH 08/20] tcmu: remove commands_lock

[Mike Christie <mchristi@redhat.com>]

No need for the commands_lock. The cmdr_lock is already held during
idr addition and deletion, so just grab it during traversal.

Note: This also fixes 2 issues.

There was no reason to use spin_lock_irq. We only were locking
against the submitting, completion and timer context. The first two
are done in process context (even though tcmu_irqcontrol is named
irq it is run from the write() calls context) and the timer was in
softirq, so we just needed to do _bh locking.

We should have been using either one tcmu_handle_completions
to prevent the case where tcmu_handle_completions could be
interrupted a timer softirq while the commands_lock is held.

Signed-off-by: Mike Christie <mchristi@redhat.com>
---
 drivers/target/target_core_user.c | 13 +++----------
 1 file changed, 3 insertions(+), 10 deletions(-)

diff --git a/drivers/target/target_core_user.c b/drivers/target/target_core_user.c
index 53a0446..9add6a3 100644
--- a/drivers/target/target_core_user.c
+++ b/drivers/target/target_core_user.c
@@ -141,7 +141,6 @@ struct tcmu_dev {
 	struct radix_tree_root data_blocks;
 
 	struct idr commands;
-	spinlock_t commands_lock;
 
 	struct timer_list timeout;
 	unsigned int cmd_time_out;
@@ -1076,10 +1075,7 @@ static unsigned int tcmu_handle_completions(struct tcmu_dev *udev)
 		}
 		WARN_ON(tcmu_hdr_get_op(entry->hdr.len_op) != TCMU_OP_CMD);
 
-		spin_lock(&udev->commands_lock);
 		cmd = idr_remove(&udev->commands, entry->hdr.cmd_id);
-		spin_unlock(&udev->commands_lock);
-
 		if (!cmd) {
 			pr_err("cmd_id not found, ring is broken\n");
 			set_bit(TCMU_DEV_BIT_BROKEN, &udev->flags);
@@ -1175,7 +1171,6 @@ static struct se_device *tcmu_alloc_device(struct se_hba *hba, const char *name)
 
 	INIT_LIST_HEAD(&udev->timedout_entry);
 	idr_init(&udev->commands);
-	spin_lock_init(&udev->commands_lock);
 
 	setup_timer(&udev->timeout, tcmu_device_timedout,
 		(unsigned long)udev);
@@ -1404,16 +1399,14 @@ static void tcmu_dev_kref_release(struct kref *kref)
 	spin_unlock_bh(&timed_out_udevs_lock);
 
 	/* Upper layer should drain all requests before calling this */
-	spin_lock_irq(&udev->commands_lock);
+	mutex_lock(&udev->cmdr_lock);
 	idr_for_each_entry(&udev->commands, cmd, i) {
 		if (tcmu_check_and_free_pending_cmd(cmd) != 0)
 			all_expired = false;
 	}
 	idr_destroy(&udev->commands);
-	spin_unlock_irq(&udev->commands_lock);
 	WARN_ON(!all_expired);
 
-	mutex_lock(&udev->cmdr_lock);
 	tcmu_blocks_release(&udev->data_blocks, 0, udev->dbi_max + 1);
 	mutex_unlock(&udev->cmdr_lock);
 
@@ -2066,9 +2059,9 @@ static void check_timedout_devices(void)
 		list_del_init(&udev->timedout_entry);
 		spin_unlock_bh(&timed_out_udevs_lock);
 
-		spin_lock(&udev->commands_lock);
+		mutex_lock(&udev->cmdr_lock);
 		idr_for_each(&udev->commands, tcmu_check_expired_cmd, NULL);
-		spin_unlock(&udev->commands_lock);
+		mutex_unlock(&udev->cmdr_lock);
 
 		spin_lock_bh(&timed_out_udevs_lock);
 	}
-- 
2.7.2