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authorChris Leech <cleech@redhat.com>2017-02-27 16:58:36 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-03-26 12:13:19 +0200
commit246760c61d9c4c0114ba5bd324df4ae17468e238 (patch)
tree40842e61e51c057a32186598fcc1d35b53c0a6d5
parent82bd06aba880215dadd3e33dc3d583d32df9dbbb (diff)
scsi: libiscsi: add lock around task lists to fix list corruption regression
commit 6f8830f5bbab16e54f261de187f3df4644a5b977 upstream. There's a rather long standing regression from the commit "libiscsi: Reduce locking contention in fast path" Depending on iSCSI target behavior, it's possible to hit the case in iscsi_complete_task where the task is still on a pending list (!list_empty(&task->running)). When that happens the task is removed from the list while holding the session back_lock, but other task list modification occur under the frwd_lock. That leads to linked list corruption and eventually a panicked system. Rather than back out the session lock split entirely, in order to try and keep some of the performance gains this patch adds another lock to maintain the task lists integrity. Major enterprise supported kernels have been backing out the lock split for while now, thanks to the efforts at IBM where a lab setup has the most reliable reproducer I've seen on this issue. This patch has been tested there successfully. Signed-off-by: Chris Leech <cleech@redhat.com> Fixes: 659743b02c41 ("[SCSI] libiscsi: Reduce locking contention in fast path") Reported-by: Prashantha Subbarao <psubbara@us.ibm.com> Reviewed-by: Guilherme G. Piccoli <gpiccoli@linux.vnet.ibm.com> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/scsi/libiscsi.c26
-rw-r--r--include/scsi/libiscsi.h1
2 files changed, 26 insertions, 1 deletions
diff --git a/drivers/scsi/libiscsi.c b/drivers/scsi/libiscsi.c
index 6bffd91b973a..c1ccf1ee99ea 100644
--- a/drivers/scsi/libiscsi.c
+++ b/drivers/scsi/libiscsi.c
@@ -560,8 +560,12 @@ static void iscsi_complete_task(struct iscsi_task *task, int state)
WARN_ON_ONCE(task->state == ISCSI_TASK_FREE);
task->state = state;
- if (!list_empty(&task->running))
+ spin_lock_bh(&conn->taskqueuelock);
+ if (!list_empty(&task->running)) {
+ pr_debug_once("%s while task on list", __func__);
list_del_init(&task->running);
+ }
+ spin_unlock_bh(&conn->taskqueuelock);
if (conn->task == task)
conn->task = NULL;
@@ -783,7 +787,9 @@ __iscsi_conn_send_pdu(struct iscsi_conn *conn, struct iscsi_hdr *hdr,
if (session->tt->xmit_task(task))
goto free_task;
} else {
+ spin_lock_bh(&conn->taskqueuelock);
list_add_tail(&task->running, &conn->mgmtqueue);
+ spin_unlock_bh(&conn->taskqueuelock);
iscsi_conn_queue_work(conn);
}
@@ -1474,8 +1480,10 @@ void iscsi_requeue_task(struct iscsi_task *task)
* this may be on the requeue list already if the xmit_task callout
* is handling the r2ts while we are adding new ones
*/
+ spin_lock_bh(&conn->taskqueuelock);
if (list_empty(&task->running))
list_add_tail(&task->running, &conn->requeue);
+ spin_unlock_bh(&conn->taskqueuelock);
iscsi_conn_queue_work(conn);
}
EXPORT_SYMBOL_GPL(iscsi_requeue_task);
@@ -1512,22 +1520,26 @@ static int iscsi_data_xmit(struct iscsi_conn *conn)
* only have one nop-out as a ping from us and targets should not
* overflow us with nop-ins
*/
+ spin_lock_bh(&conn->taskqueuelock);
check_mgmt:
while (!list_empty(&conn->mgmtqueue)) {
conn->task = list_entry(conn->mgmtqueue.next,
struct iscsi_task, running);
list_del_init(&conn->task->running);
+ spin_unlock_bh(&conn->taskqueuelock);
if (iscsi_prep_mgmt_task(conn, conn->task)) {
/* regular RX path uses back_lock */
spin_lock_bh(&conn->session->back_lock);
__iscsi_put_task(conn->task);
spin_unlock_bh(&conn->session->back_lock);
conn->task = NULL;
+ spin_lock_bh(&conn->taskqueuelock);
continue;
}
rc = iscsi_xmit_task(conn);
if (rc)
goto done;
+ spin_lock_bh(&conn->taskqueuelock);
}
/* process pending command queue */
@@ -1535,19 +1547,24 @@ check_mgmt:
conn->task = list_entry(conn->cmdqueue.next, struct iscsi_task,
running);
list_del_init(&conn->task->running);
+ spin_unlock_bh(&conn->taskqueuelock);
if (conn->session->state == ISCSI_STATE_LOGGING_OUT) {
fail_scsi_task(conn->task, DID_IMM_RETRY);
+ spin_lock_bh(&conn->taskqueuelock);
continue;
}
rc = iscsi_prep_scsi_cmd_pdu(conn->task);
if (rc) {
if (rc == -ENOMEM || rc == -EACCES) {
+ spin_lock_bh(&conn->taskqueuelock);
list_add_tail(&conn->task->running,
&conn->cmdqueue);
conn->task = NULL;
+ spin_unlock_bh(&conn->taskqueuelock);
goto done;
} else
fail_scsi_task(conn->task, DID_ABORT);
+ spin_lock_bh(&conn->taskqueuelock);
continue;
}
rc = iscsi_xmit_task(conn);
@@ -1558,6 +1575,7 @@ check_mgmt:
* we need to check the mgmt queue for nops that need to
* be sent to aviod starvation
*/
+ spin_lock_bh(&conn->taskqueuelock);
if (!list_empty(&conn->mgmtqueue))
goto check_mgmt;
}
@@ -1577,12 +1595,15 @@ check_mgmt:
conn->task = task;
list_del_init(&conn->task->running);
conn->task->state = ISCSI_TASK_RUNNING;
+ spin_unlock_bh(&conn->taskqueuelock);
rc = iscsi_xmit_task(conn);
if (rc)
goto done;
+ spin_lock_bh(&conn->taskqueuelock);
if (!list_empty(&conn->mgmtqueue))
goto check_mgmt;
}
+ spin_unlock_bh(&conn->taskqueuelock);
spin_unlock_bh(&conn->session->frwd_lock);
return -ENODATA;
@@ -1738,7 +1759,9 @@ int iscsi_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *sc)
goto prepd_reject;
}
} else {
+ spin_lock_bh(&conn->taskqueuelock);
list_add_tail(&task->running, &conn->cmdqueue);
+ spin_unlock_bh(&conn->taskqueuelock);
iscsi_conn_queue_work(conn);
}
@@ -2900,6 +2923,7 @@ iscsi_conn_setup(struct iscsi_cls_session *cls_session, int dd_size,
INIT_LIST_HEAD(&conn->mgmtqueue);
INIT_LIST_HEAD(&conn->cmdqueue);
INIT_LIST_HEAD(&conn->requeue);
+ spin_lock_init(&conn->taskqueuelock);
INIT_WORK(&conn->xmitwork, iscsi_xmitworker);
/* allocate login_task used for the login/text sequences */
diff --git a/include/scsi/libiscsi.h b/include/scsi/libiscsi.h
index 4d1c46aac331..c7b1dc713cdd 100644
--- a/include/scsi/libiscsi.h
+++ b/include/scsi/libiscsi.h
@@ -196,6 +196,7 @@ struct iscsi_conn {
struct iscsi_task *task; /* xmit task in progress */
/* xmit */
+ spinlock_t taskqueuelock; /* protects the next three lists */
struct list_head mgmtqueue; /* mgmt (control) xmit queue */
struct list_head cmdqueue; /* data-path cmd queue */
struct list_head requeue; /* tasks needing another run */