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iscsi-target: Fix potential dead-lock during node acl delete 

commit 26a99c19f810b2593410899a5b304b21b47428a6 upstream.

This patch is a iscsi-target specific bug-fix for a dead-lock
that can occur during explicit struct se_node_acl->acl_group
se_session deletion via configfs rmdir(2), when iscsi-target
time2retain timer is still active.

It changes iscsi-target to obtain se_portal_group->session_lock
internally using spin_in_locked() to check for the specific
se_node_acl configfs shutdown rmdir(2) case.

Note this patch is intended for stable, and the subsequent
v4.5-rc patch converts target_core_tpg.c to use proper
se_sess->sess_kref reference counting for both se_node_acl
deletion + se_node_acl->queue_depth se_session restart.

Reported-by:: Sagi Grimberg <sagig@mellanox.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Andy Grover <agrover@redhat.com>
Cc: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Nicholas Bellinger 2016-01-19 16:15:27 -08:00 committed by Greg Kroah-Hartman
parent 2bfa7bba55
commit bac26cabd2
1 changed files with 15 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
drivers/target/iscsi/iscsi_target_configfs.c
View File

@ -1730,7 +1730,8 @@ static void lio_tpg_release_fabric_acl(
}
/*
* Called with spin_lock_bh(struct se_portal_group->session_lock) held..
* Called with spin_lock_irq(struct se_portal_group->session_lock) held
* or not held.
*
* Also, this function calls iscsit_inc_session_usage_count() on the
* struct iscsi_session in question.
@ -1738,19 +1739,32 @@ static void lio_tpg_release_fabric_acl(
static int lio_tpg_shutdown_session(struct se_session *se_sess)
{
struct iscsi_session *sess = se_sess->fabric_sess_ptr;
struct se_portal_group *se_tpg = se_sess->se_tpg;
bool local_lock = false;
if (!spin_is_locked(&se_tpg->session_lock)) {
spin_lock_irq(&se_tpg->session_lock);
local_lock = true;
}
spin_lock(&sess->conn_lock);
if (atomic_read(&sess->session_fall_back_to_erl0) ||
atomic_read(&sess->session_logout) ||
(sess->time2retain_timer_flags & ISCSI_TF_EXPIRED)) {
spin_unlock(&sess->conn_lock);
if (local_lock)
spin_unlock_irq(&sess->conn_lock);
return 0;
}
atomic_set(&sess->session_reinstatement, 1);
spin_unlock(&sess->conn_lock);
iscsit_stop_time2retain_timer(sess);
spin_unlock_irq(&se_tpg->session_lock);
iscsit_stop_session(sess, 1, 1);
if (!local_lock)
spin_lock_irq(&se_tpg->session_lock);
return 1;
}