From patchwork Fri Jan 3 19:26:11 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Gabriel Krisman Bertazi X-Patchwork-Id: 11317357 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id DDECA1395 for ; Fri, 3 Jan 2020 19:26:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BE1F7222C4 for ; Fri, 3 Jan 2020 19:26:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728537AbgACT0S (ORCPT ); Fri, 3 Jan 2020 14:26:18 -0500 Received: from bhuna.collabora.co.uk ([46.235.227.227]:43182 "EHLO bhuna.collabora.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728513AbgACT0S (ORCPT ); Fri, 3 Jan 2020 14:26:18 -0500 Received: from [127.0.0.1] (localhost [127.0.0.1]) (Authenticated sender: krisman) with ESMTPSA id CBFC828F6C5 From: Gabriel Krisman Bertazi To: Khazhismel Kumykov Cc: lduncan@suse.com, Chris Leech , jejb@linux.ibm.com, "Martin K. Petersen" , "'Khazhismel Kumykov' via open-iscsi" , linux-scsi@vger.kernel.org, Bharath Ravi , kernel@collabora.com, Mike Christie , Bart Van Assche , Dave Clausen , Nick Black , Vaibhav Nagarnaik , Anatol Pomazau , Tahsin Erdogan , Frank Mayhar , Junho Ryu Subject: [PATCH v4] iscsi: Perform connection failure entirely in kernel space Organization: Collabora References: <20191226204746.2197233-1-krisman@collabora.com> <85ftgx7mlr.fsf@collabora.com> Date: Fri, 03 Jan 2020 14:26:11 -0500 In-Reply-To: (Khazhismel Kumykov's message of "Thu, 2 Jan 2020 13:24:39 -0500") Message-ID: <85r20g2vfw.fsf_-_@collabora.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Sender: linux-scsi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org Khazhismel Kumykov writes: >> >> + if (!list_empty(&conn->conn_list_err)) >> > Does this check need to be under connlock? >> >> My understanding is that it is not necessary, since it is serialized >> against the conn removal itself, through the rx_mutex, it seemed safe to >> do the verification lockless. >> >> It can only race with the insertion, in which case, it will be safely >> removed from the dispatch list here, under rx_mutex, and the worker will >> detect and skipped it. > > My worry is the splice, which is under only connlock, not rx_mutex, which > might lead to UB if we're checking empty while modifying the list_head ? Hi, Please consider the v4 below with the lock added. -- >8 -- From: Bharath Ravi Connection failure processing depends on a daemon being present to (at least) stop the connection and start recovery. This is a problem on a multipath scenario, where if the daemon failed for whatever reason, the SCSI path is never marked as down, multipath won't perform the failover and IO to the device will be forever waiting for that connection to come back. This patch performs the connection failure entirely inside the kernel. This way, the failover can happen and pending IO can continue even if the daemon is dead. Once the daemon comes alive again, it can execute recovery procedures if applicable. Changes since v3: - Protect list_empty with connlock on session destroy Changes since v2: - Don't hold rx_mutex for too long at once Changes since v1: - Remove module parameter. - Always do kernel-side stop work. - Block recovery timeout handler if system is dying. - send a CONN_TERM stop if the system is dying. Cc: Mike Christie Cc: Lee Duncan Cc: Bart Van Assche Reviewed-by: Lee Duncan Co-developed-by: Dave Clausen Signed-off-by: Dave Clausen Co-developed-by: Nick Black Signed-off-by: Nick Black Co-developed-by: Vaibhav Nagarnaik Signed-off-by: Vaibhav Nagarnaik Co-developed-by: Anatol Pomazau Signed-off-by: Anatol Pomazau Co-developed-by: Tahsin Erdogan Signed-off-by: Tahsin Erdogan Co-developed-by: Frank Mayhar Signed-off-by: Frank Mayhar Co-developed-by: Junho Ryu Signed-off-by: Junho Ryu Co-developed-by: Khazhismel Kumykov Signed-off-by: Khazhismel Kumykov Signed-off-by: Bharath Ravi Co-developed-by: Gabriel Krisman Bertazi Signed-off-by: Gabriel Krisman Bertazi Reviewed-by: Khazhismel Kumykov --- drivers/scsi/scsi_transport_iscsi.c | 68 +++++++++++++++++++++++++++++ include/scsi/scsi_transport_iscsi.h | 1 + 2 files changed, 69 insertions(+) diff --git a/drivers/scsi/scsi_transport_iscsi.c b/drivers/scsi/scsi_transport_iscsi.c index 271afea654e2..ba6cfaf71aef 100644 --- a/drivers/scsi/scsi_transport_iscsi.c +++ b/drivers/scsi/scsi_transport_iscsi.c @@ -86,6 +86,12 @@ struct iscsi_internal { struct transport_container session_cont; }; +/* Worker to perform connection failure on unresponsive connections + * completely in kernel space. + */ +static void stop_conn_work_fn(struct work_struct *work); +static DECLARE_WORK(stop_conn_work, stop_conn_work_fn); + static atomic_t iscsi_session_nr; /* sysfs session id for next new session */ static struct workqueue_struct *iscsi_eh_timer_workq; @@ -1611,6 +1617,7 @@ static DEFINE_MUTEX(rx_queue_mutex); static LIST_HEAD(sesslist); static DEFINE_SPINLOCK(sesslock); static LIST_HEAD(connlist); +static LIST_HEAD(connlist_err); static DEFINE_SPINLOCK(connlock); static uint32_t iscsi_conn_get_sid(struct iscsi_cls_conn *conn) @@ -2247,6 +2254,7 @@ iscsi_create_conn(struct iscsi_cls_session *session, int dd_size, uint32_t cid) mutex_init(&conn->ep_mutex); INIT_LIST_HEAD(&conn->conn_list); + INIT_LIST_HEAD(&conn->conn_list_err); conn->transport = transport; conn->cid = cid; @@ -2293,6 +2301,7 @@ int iscsi_destroy_conn(struct iscsi_cls_conn *conn) spin_lock_irqsave(&connlock, flags); list_del(&conn->conn_list); + list_del(&conn->conn_list_err); spin_unlock_irqrestore(&connlock, flags); transport_unregister_device(&conn->dev); @@ -2407,6 +2416,51 @@ int iscsi_offload_mesg(struct Scsi_Host *shost, } EXPORT_SYMBOL_GPL(iscsi_offload_mesg); +static void stop_conn_work_fn(struct work_struct *work) +{ + struct iscsi_cls_conn *conn, *tmp; + unsigned long flags; + LIST_HEAD(recovery_list); + + spin_lock_irqsave(&connlock, flags); + if (list_empty(&connlist_err)) { + spin_unlock_irqrestore(&connlock, flags); + return; + } + list_splice_init(&connlist_err, &recovery_list); + spin_unlock_irqrestore(&connlock, flags); + + list_for_each_entry_safe(conn, tmp, &recovery_list, conn_list_err) { + uint32_t sid = iscsi_conn_get_sid(conn); + struct iscsi_cls_session *session; + + mutex_lock(&rx_queue_mutex); + + session = iscsi_session_lookup(sid); + if (session) { + if (system_state != SYSTEM_RUNNING) { + session->recovery_tmo = 0; + conn->transport->stop_conn(conn, + STOP_CONN_TERM); + } else { + conn->transport->stop_conn(conn, + STOP_CONN_RECOVER); + } + } + + list_del_init(&conn->conn_list_err); + + mutex_unlock(&rx_queue_mutex); + + /* we don't want to hold rx_queue_mutex for too long, + * for instance if many conns failed at the same time, + * since this stall other iscsi maintenance operations. + * Give other users a chance to proceed. + */ + cond_resched(); + } +} + void iscsi_conn_error_event(struct iscsi_cls_conn *conn, enum iscsi_err error) { struct nlmsghdr *nlh; @@ -2414,6 +2468,12 @@ void iscsi_conn_error_event(struct iscsi_cls_conn *conn, enum iscsi_err error) struct iscsi_uevent *ev; struct iscsi_internal *priv; int len = nlmsg_total_size(sizeof(*ev)); + unsigned long flags; + + spin_lock_irqsave(&connlock, flags); + list_add(&conn->conn_list_err, &connlist_err); + spin_unlock_irqrestore(&connlock, flags); + queue_work(system_unbound_wq, &stop_conn_work); priv = iscsi_if_transport_lookup(conn->transport); if (!priv) @@ -2743,11 +2803,19 @@ static int iscsi_if_destroy_conn(struct iscsi_transport *transport, struct iscsi_uevent *ev) { struct iscsi_cls_conn *conn; + unsigned long flags; conn = iscsi_conn_lookup(ev->u.d_conn.sid, ev->u.d_conn.cid); if (!conn) return -EINVAL; + spin_lock_irqsave(&connlock, flags); + if (!list_empty(&conn->conn_list_err)) { + spin_unlock_irqrestore(&connlock, flags); + return -EAGAIN; + } + spin_unlock_irqrestore(&connlock, flags); + ISCSI_DBG_TRANS_CONN(conn, "Destroying transport conn\n"); if (transport->destroy_conn) transport->destroy_conn(conn); diff --git a/include/scsi/scsi_transport_iscsi.h b/include/scsi/scsi_transport_iscsi.h index 325ae731d9ad..2129dc9e2dec 100644 --- a/include/scsi/scsi_transport_iscsi.h +++ b/include/scsi/scsi_transport_iscsi.h @@ -190,6 +190,7 @@ extern void iscsi_ping_comp_event(uint32_t host_no, struct iscsi_cls_conn { struct list_head conn_list; /* item in connlist */ + struct list_head conn_list_err; /* item in connlist_err */ void *dd_data; /* LLD private data */ struct iscsi_transport *transport; uint32_t cid; /* connection id */