On Thu, 2017-06-01 at 18:17 +0000, Bart Van Assche wrote:
> Hello Nic,
>
> This morning I started testing your for-next branch (commit b968ec8ff101
> with no changes). After a few seconds a kernel crash was triggered (see below).
> In the many tests I ran during the past two years of the ib_srpt driver I had
> not encountered any crash triggered by ib_srpt so this must be a recently
> introduced regression in the target core. This regression most likely has been
> introduced by one of these patches:
>
> b968ec8ff101 target/configfs: Kill se_lun->lun_link_magic
> baacb554a73b target/configfs: Kill se_device->dev_link_magic
> ba438d7c8d39 target: Avoid target_shutdown_sessions loop during queue_depth change
Alas, the local list and unprotected list_del_init() ba438d7c8d won't
work for all fabric cases.
Here's the updated version to restore original behavior for se_node_acl
delete, but still avoid the endless loop with the iscsi-target specific
case where se_node_acl->queue_depth changes.
Care to verify on ib_srpt, or just a report and never confirm..?
>From 9fdc33be4ef60ba87c8bf8a4dab6e756ec3b06e6 Mon Sep 17 00:00:00 2001
From: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
Date: Thu, 1 Jun 2017 08:57:15 +0200
Subject: [PATCH-v2] target: Avoid target_shutdown_sessions loop during
queue_depth change
When target_shutdown_sessions() is invoked to shutdown all active
sessions associated with a se_node_acl when se_node_acl->queue_depth
is changed via core_tpg_set_initiator_node_queue_depth(), it's
possible that new connections reconnect immediately after explicit
shutdown occurs via target_shutdown_sessions().
Which means it's possible for the newly reconnected session with
the proper queue_depth can be shutdown multiple times when
target_shutdown_sessions() loops to drain all active sessions
for all cases.
This was regression was introduced by:
commit bc6e6bb470eda42f44bcac96c261cff1216577b3
Author: Christoph Hellwig <hch@xxxxxx>
Date: Mon May 2 15:45:19 2016 +0200
target: consolidate and fix session shutdown
To avoid this case, instead change target_shutdown_sessions() to
pass 'do_restart' and avoid the looping drain of sessions when
invoked via core_tpg_set_initiator_node_queue_depth(), but still
loop during normal se_node_acl delete until all associated
sessions have been shutdown.
(v2 - go back to the original version instead of a local list,
in order to protect list_del_init(&sess->sess_acl_list) from
transport_deregister_session_configfs.
Also use safe list walking in target_shutdown_sessions - nab)
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Mike Christie <mchristi@xxxxxxxxxx>
Cc: Hannes Reinecke <hare@xxxxxxxx>
Signed-off-by: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
---
drivers/target/target_core_tpg.c | 16 ++++++++++------
1 file changed, 10 insertions(+), 6 deletions(-)
diff --git a/drivers/target/target_core_tpg.c b/drivers/target/target_core_tpg.c
index 3691373..1b2b60e 100644
--- a/drivers/target/target_core_tpg.c
+++ b/drivers/target/target_core_tpg.c
@@ -336,14 +336,14 @@ struct se_node_acl *core_tpg_add_initiator_node_acl(
return acl;
}
-static void target_shutdown_sessions(struct se_node_acl *acl)
+static void target_shutdown_sessions(struct se_node_acl *acl, bool do_restart)
{
- struct se_session *sess;
+ struct se_session *sess, *sess_tmp;
unsigned long flags;
restart:
spin_lock_irqsave(&acl->nacl_sess_lock, flags);
- list_for_each_entry(sess, &acl->acl_sess_list, sess_acl_list) {
+ list_for_each_entry_safe(sess, sess_tmp, &acl->acl_sess_list, sess_acl_list) {
if (sess->sess_tearing_down)
continue;
@@ -352,7 +352,11 @@ static void target_shutdown_sessions(struct se_node_acl *acl)
if (acl->se_tpg->se_tpg_tfo->close_session)
acl->se_tpg->se_tpg_tfo->close_session(sess);
- goto restart;
+
+ if (do_restart)
+ goto restart;
+
+ spin_lock_irqsave(&acl->nacl_sess_lock, flags);
}
spin_unlock_irqrestore(&acl->nacl_sess_lock, flags);
}
@@ -367,7 +371,7 @@ void core_tpg_del_initiator_node_acl(struct se_node_acl *acl)
list_del(&acl->acl_list);
mutex_unlock(&tpg->acl_node_mutex);
- target_shutdown_sessions(acl);
+ target_shutdown_sessions(acl, true);
target_put_nacl(acl);
/*
@@ -414,7 +418,7 @@ int core_tpg_set_initiator_node_queue_depth(
/*
* Shutdown all pending sessions to force session reinstatement.
*/
- target_shutdown_sessions(acl);
+ target_shutdown_sessions(acl, false);
pr_debug("Successfully changed queue depth to: %d for Initiator"
" Node: %s on %s Target Portal Group: %u\n", acl->queue_depth,
--
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