From patchwork Fri Nov 6 19:33:17 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Lee Duncan X-Patchwork-Id: 321800 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-12.5 required=3.0 tests=BAYES_00, DKIM_ADSP_CUSTOM_MED,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 02DCCC2D0A3 for ; Fri, 6 Nov 2020 19:33:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 989CC20867 for ; Fri, 6 Nov 2020 19:33:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727982AbgKFTdm (ORCPT ); Fri, 6 Nov 2020 14:33:42 -0500 Received: from mx2.suse.de ([195.135.220.15]:40638 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726415AbgKFTdl (ORCPT ); Fri, 6 Nov 2020 14:33:41 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id F0ED1AC1D; Fri, 6 Nov 2020 19:33:39 +0000 (UTC) Received: by localhost (Postfix, from userid 1000) id 02BA653FE57; Fri, 6 Nov 2020 11:33:37 -0800 (PST) From: Lee Duncan To: linux-scsi@vger.kernel.org Cc: michael.christie@oracle.com, open-iscsi@googlegroups.com, Lee Duncan Subject: [PATCH v2] SCSI: libiscsi: fix NOP race condition Date: Fri, 6 Nov 2020 11:33:17 -0800 Message-Id: <20201106193317.16993-1-leeman.duncan@gmail.com> X-Mailer: git-send-email 2.26.2 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org From: Lee Duncan iSCSI NOPs are sometimes "lost", mistakenly sent to the user-land iscsid daemon instead of handled in the kernel, as they should be, resulting in a message from the daemon like: > iscsid: Got nop in, but kernel supports nop handling. This can occur because of the new forward- and back-locks, and the fact that an iSCSI NOP response can occur before processing of the NOP send is complete. This can result in "conn->ping_task" being NULL in iscsi_nop_out_rsp(), when the pointer is actually in the process of being set. To work around this, we add a new state to the "ping_task" pointer. In addition to NULL (not assigned) and a pointer (assigned), we add the state "being set", which is signaled with an INVALID pointer (using "-1"). Changes since V1: - expanded using READ_ONCE()/WRITE_ONCE() to the whole path Signed-off-by: Lee Duncan Reviewed-by: Mike Christie --- drivers/scsi/libiscsi.c | 23 +++++++++++++++-------- include/scsi/libiscsi.h | 3 +++ 2 files changed, 18 insertions(+), 8 deletions(-) diff --git a/drivers/scsi/libiscsi.c b/drivers/scsi/libiscsi.c index 1e9c3171fa9f..f9314f1393fb 100644 --- a/drivers/scsi/libiscsi.c +++ b/drivers/scsi/libiscsi.c @@ -533,8 +533,8 @@ static void iscsi_complete_task(struct iscsi_task *task, int state) if (conn->task == task) conn->task = NULL; - if (conn->ping_task == task) - conn->ping_task = NULL; + if (READ_ONCE(conn->ping_task) == task) + WRITE_ONCE(conn->ping_task, NULL); /* release get from queueing */ __iscsi_put_task(task); @@ -738,6 +738,9 @@ __iscsi_conn_send_pdu(struct iscsi_conn *conn, struct iscsi_hdr *hdr, task->conn->session->age); } + if (unlikely(READ_ONCE(conn->ping_task) == INVALID_SCSI_TASK)) + WRITE_ONCE(conn->ping_task, task); + if (!ihost->workq) { if (iscsi_prep_mgmt_task(conn, task)) goto free_task; @@ -941,8 +944,11 @@ static int iscsi_send_nopout(struct iscsi_conn *conn, struct iscsi_nopin *rhdr) struct iscsi_nopout hdr; struct iscsi_task *task; - if (!rhdr && conn->ping_task) - return -EINVAL; + if (!rhdr) { + if (READ_ONCE(conn->ping_task)) + return -EINVAL; + WRITE_ONCE(conn->ping_task, INVALID_SCSI_TASK); + } memset(&hdr, 0, sizeof(struct iscsi_nopout)); hdr.opcode = ISCSI_OP_NOOP_OUT | ISCSI_OP_IMMEDIATE; @@ -957,11 +963,12 @@ static int iscsi_send_nopout(struct iscsi_conn *conn, struct iscsi_nopin *rhdr) task = __iscsi_conn_send_pdu(conn, (struct iscsi_hdr *)&hdr, NULL, 0); if (!task) { + if (!rhdr) + WRITE_ONCE(conn->ping_task, NULL); iscsi_conn_printk(KERN_ERR, conn, "Could not send nopout\n"); return -EIO; } else if (!rhdr) { /* only track our nops */ - conn->ping_task = task; conn->last_ping = jiffies; } @@ -984,7 +991,7 @@ static int iscsi_nop_out_rsp(struct iscsi_task *task, struct iscsi_conn *conn = task->conn; int rc = 0; - if (conn->ping_task != task) { + if (READ_ONCE(conn->ping_task) != task) { /* * If this is not in response to one of our * nops then it must be from userspace. @@ -1923,7 +1930,7 @@ static void iscsi_start_tx(struct iscsi_conn *conn) */ static int iscsi_has_ping_timed_out(struct iscsi_conn *conn) { - if (conn->ping_task && + if (READ_ONCE(conn->ping_task) && time_before_eq(conn->last_recv + (conn->recv_timeout * HZ) + (conn->ping_timeout * HZ), jiffies)) return 1; @@ -2058,7 +2065,7 @@ enum blk_eh_timer_return iscsi_eh_cmd_timed_out(struct scsi_cmnd *sc) * Checking the transport already or nop from a cmd timeout still * running */ - if (conn->ping_task) { + if (READ_ONCE(conn->ping_task)) { task->have_checked_conn = true; rc = BLK_EH_RESET_TIMER; goto done; diff --git a/include/scsi/libiscsi.h b/include/scsi/libiscsi.h index c25fb86ffae9..b3bbd10eb3f0 100644 --- a/include/scsi/libiscsi.h +++ b/include/scsi/libiscsi.h @@ -132,6 +132,9 @@ struct iscsi_task { void *dd_data; /* driver/transport data */ }; +/* invalid scsi_task pointer */ +#define INVALID_SCSI_TASK (struct iscsi_task *)-1l + static inline int iscsi_task_has_unsol_data(struct iscsi_task *task) { return task->unsol_r2t.data_length > task->unsol_r2t.sent;