[Devel] [PATCH 1/3] target: Invoke release_cmd() callback without holding a spinlock

[Andrei Vagin]

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From: Bart Van Assche <bart.vanassche at sandisk.com>

Here is a backport of the mainline commit:
ML: 9ff9d15eddd13ecdd41876c5e1f31ddbb127101c

This patch fixes the following kernel warning because it avoids that
IRQs are disabled while ft_release_cmd() is invoked (fc_seq_set_resp()
invokes spin_unlock_bh()):

WARNING: CPU: 3 PID: 117 at kernel/softirq.c:150 __local_bh_enable_ip+0xaa/0x110()
Call Trace:
 [<ffffffff814f71eb>] dump_stack+0x4f/0x7b
 [<ffffffff8105e56a>] warn_slowpath_common+0x8a/0xc0
 [<ffffffff8105e65a>] warn_slowpath_null+0x1a/0x20
 [<ffffffff81062b2a>] __local_bh_enable_ip+0xaa/0x110
 [<ffffffff814ff229>] _raw_spin_unlock_bh+0x39/0x40
 [<ffffffffa03a7f94>] fc_seq_set_resp+0xe4/0x100 [libfc]
 [<ffffffffa02e604a>] ft_free_cmd+0x4a/0x90 [tcm_fc]
 [<ffffffffa02e6972>] ft_release_cmd+0x12/0x20 [tcm_fc]
 [<ffffffffa042bd66>] target_release_cmd_kref+0x56/0x90 [target_core_mod]
 [<ffffffffa042caf0>] target_put_sess_cmd+0xc0/0x110 [target_core_mod]
 [<ffffffffa042cb81>] transport_release_cmd+0x41/0x70 [target_core_mod]
 [<ffffffffa042d975>] transport_generic_free_cmd+0x35/0x420 [target_core_mod]

Signed-off-by: Bart Van Assche <bart.vanassche at sandisk.com>
Acked-by: Joern Engel <joern at logfs.org>
Reviewed-by: Andy Grover <agrover at redhat.com>
Cc: Christoph Hellwig <hch at lst.de>
Cc: Hannes Reinecke <hare at suse.de>
Cc: Sagi Grimberg <sagig at mellanox.com>
Signed-off-by: Nicholas Bellinger <nab at linux-iscsi.org>
---
 drivers/target/target_core_tmr.c       |  7 ++++++-
 drivers/target/target_core_transport.c | 11 ++++++-----
 2 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/drivers/target/target_core_tmr.c b/drivers/target/target_core_tmr.c
index 7723d11..ae5c3e5 100644
--- a/drivers/target/target_core_tmr.c
+++ b/drivers/target/target_core_tmr.c
@@ -133,6 +133,9 @@ void core_tmr_abort_task(
                if (tmr->ref_task_tag != ref_tag)
                        continue;

+               if (!kref_get_unless_zero(&se_cmd->cmd_kref))
+                       continue;
+
                printk("ABORT_TASK: Found referenced %s task_tag: %u\n",
                        se_cmd->se_tfo->get_fabric_name(), ref_tag);

@@ -141,13 +144,15 @@ void core_tmr_abort_task(
                        printk("ABORT_TASK: ref_tag: %u already complete, skipping\n", ref_tag);
                        spin_unlock(&se_cmd->t_state_lock);
                        spin_unlock_irqrestore(&se_sess->sess_cmd_lock, flags);
+
+                       target_put_sess_cmd(se_cmd);
+
                        goto out;
                }
                se_cmd->transport_state |= CMD_T_ABORTED;
                spin_unlock(&se_cmd->t_state_lock);

                list_del_init(&se_cmd->se_cmd_list);
-               kref_get(&se_cmd->cmd_kref);
                spin_unlock_irqrestore(&se_sess->sess_cmd_lock, flags);

                cancel_work_sync(&se_cmd->work);
diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index b27c17b..b0aa9ac 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -2494,19 +2494,21 @@ static void target_release_cmd_kref(struct kref *kref)
 {
        struct se_cmd *se_cmd = container_of(kref, struct se_cmd, cmd_kref);
        struct se_session *se_sess = se_cmd->se_sess;
+       unsigned long flags;

+       spin_lock_irqsave(&se_sess->sess_cmd_lock, flags);
        if (list_empty(&se_cmd->se_cmd_list)) {
-               spin_unlock(&se_sess->sess_cmd_lock);
+               spin_unlock_irqrestore(&se_sess->sess_cmd_lock, flags);
                se_cmd->se_tfo->release_cmd(se_cmd);
                return;
        }
        if (se_sess->sess_tearing_down && se_cmd->cmd_wait_set) {
-               spin_unlock(&se_sess->sess_cmd_lock);
+               spin_unlock_irqrestore(&se_sess->sess_cmd_lock, flags);
                complete(&se_cmd->cmd_wait_comp);
                return;
        }
        list_del(&se_cmd->se_cmd_list);
-       spin_unlock(&se_sess->sess_cmd_lock);
+       spin_unlock_irqrestore(&se_sess->sess_cmd_lock, flags);

        se_cmd->se_tfo->release_cmd(se_cmd);
 }
@@ -2522,8 +2524,7 @@ int target_put_sess_cmd(struct se_cmd *se_cmd)
                se_cmd->se_tfo->release_cmd(se_cmd);
                return 1;
        }
-       return kref_put_spinlock_irqsave(&se_cmd->cmd_kref, target_release_cmd_kref,
-                       &se_sess->sess_cmd_lock);
+       return kref_put(&se_cmd->cmd_kref, target_release_cmd_kref);
 }
 EXPORT_SYMBOL(target_put_sess_cmd);

--
1.8.3.1