From patchwork Tue Jun 30 10:47:07 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Bodo Stroesser X-Patchwork-Id: 213641 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=-10.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU, 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 ADECBC433E3 for ; Tue, 30 Jun 2020 10:47:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 83D7A207E8 for ; Tue, 30 Jun 2020 10:47:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=ts.fujitsu.com header.i=@ts.fujitsu.com header.b="kZrVo/5i" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732660AbgF3Kru (ORCPT ); Tue, 30 Jun 2020 06:47:50 -0400 Received: from mail1.bemta26.messagelabs.com ([85.158.142.113]:15403 "EHLO mail1.bemta26.messagelabs.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732583AbgF3Krr (ORCPT ); Tue, 30 Jun 2020 06:47:47 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ts.fujitsu.com; s=200619tsfj; t=1593514060; i=@ts.fujitsu.com; bh=pYNo6yKo57bY/EY4E2BdwIp9O/+3AvXWNSsi/zzHTFg=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References; b=kZrVo/5i1YACpZU/NkIsnLPSS0X6MYaCXl7OcZ20iwIP3jRXotZoDqJrYJd95uu6v /UtTU/XEkgYtOVfpk6Eu3xV6hd3E/hiaJggoBifFohkVYd8mt72sU5U1jrTN8/yeoZ 3CSCVt8JYGCQmMKMFL4QlAj/cXeAFN0cK8/IhWab9Wjd7Kuy/9H1QAXgGkOxBFOQEx Y17Y7G/iU3moUf9BUKa+pjQze/rwhfHVrt+kkDS6b2wvgbf7pRyKXwErkhFR9EcYfe otxkp2aPlj38c9/WwnX2TYzi5ACRN+G43gMWaID23FHkJWhwRVQYfetQBM+V4JsVG/ O8lD/WzaoOxMw== Received: from [100.113.4.241] (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256 bits)) by server-2.bemta.az-b.eu-central-1.aws.symcld.net id 30/2D-49188-C481BFE5; Tue, 30 Jun 2020 10:47:40 +0000 X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFvrDLMWRWlGSWpSXmKPExsViZ8MxVddb4ne cwevbVhbd13ewWSw//o/J4u+kG6wWrUvfMjmweHx8eovF4/MmuQCmKNbMvKT8igTWjKdb37EV rFStePTlDFMD42H5LkZODiGByYwSu7YWdjFyAdnTGSWm/H/JBJJgEzCQWDHpPgtIQkRgDaPEy jvzmEESzAJ6EtP+rWMHsYUF/CS23HnECmKzCKhK7HrznQ3E5hWwk5jec4kFxJYQkJfoODAZzO YUsJdYe/g0C8RmO4m1m2eyTWDkXsDIsIrRMqkoMz2jJDcxM0fX0MBA19DQWNdU18jEUC+xSjd JL7VUNzk1r6QoESirl1herFdcmZuck6KXl1qyiREYKCmFrB93MB56/UHvEKMkB5OSKO+9f7/i hPiS8lMqMxKLM+KLSnNSiw8xynBwKEnwPhX/HSckWJSanlqRlpkDDFqYtAQHj5II736QNG9xQ WJucWY6ROoUo6KUOO9KMaCEAEgiozQPrg0WKZcYZaWEeRkZGBiEeApSi3IzS1DlXzGKczAqCf MmgIznycwrgZv+CmgxE9Dia1q/QBaXJCKkpBqY5t879Xvrjz01Wv4xSekfzTx9myQKf2V2mz5 Ubz16TrDg7L0V+jG/Ts2YdGmrxNIYvdNHjq/h6e9kXP16l4/g1i6bIPmd1+dueHhSUk7i+KNM 7fc8NzyU6l9bPuZbdE4k285QaA7D7MuidzyPMy9ar5Ejnn/uf+t3/fqlL6rrO9qkCxOC1G+md l6p2Jp3Oqnfe/MLvSNiKmwN/k4KcxsE5WIO1HQq3eM5ZyJx3N9Hgm39tl3dzpsTVlrdN53Zk3 b2iEryJ3XnPwGqy5SY937hstvMMffAyr/BS2bemTm1cF4jR5SRitpllxydjZs5i+fWVi3VqTu xb67f1qBpHdOK1x+4Fm2pxyG20ciMY4eKEktxRqKhFnNRcSIA8evLdQ8DAAA= X-Env-Sender: bstroesser@ts.fujitsu.com X-Msg-Ref: server-24.tower-238.messagelabs.com!1593514059!1349444!1 X-Originating-IP: [62.60.8.149] X-SYMC-ESS-Client-Auth: outbound-route-from=pass X-StarScan-Received: X-StarScan-Version: 9.50.2; banners=-,-,- X-VirusChecked: Checked Received: (qmail 27593 invoked from network); 30 Jun 2020 10:47:39 -0000 Received: from unknown (HELO mailhost2.uk.fujitsu.com) (62.60.8.149) by server-24.tower-238.messagelabs.com with ECDHE-RSA-AES256-GCM-SHA384 encrypted SMTP; 30 Jun 2020 10:47:39 -0000 Received: from x-serv01 ([172.17.38.52]) by mailhost2.uk.fujitsu.com (8.14.5/8.14.5) with SMTP id 05UAlYOx004488; Tue, 30 Jun 2020 11:47:35 +0100 Received: from VTC.emeia.fujitsu.local (unknown [172.17.38.7]) by x-serv01 (Postfix) with ESMTP id 77FEA20AD8; Tue, 30 Jun 2020 12:47:33 +0200 (CEST) From: Bodo Stroesser To: "Martin K. Petersen" , Mike Christie , linux-scsi@vger.kernel.org, target-devel@vger.kernel.org Cc: Bodo Stroesser Subject: [RFC PATCH 6/8] scsi: target: tcmu: Fix and simplify timeout handling Date: Tue, 30 Jun 2020 12:47:07 +0200 Message-Id: <20200630104709.23066-7-bstroesser@ts.fujitsu.com> X-Mailer: git-send-email 2.12.3 In-Reply-To: <20200630104709.23066-1-bstroesser@ts.fujitsu.com> References: <20200630104709.23066-1-bstroesser@ts.fujitsu.com> Sender: linux-scsi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org During cmd timeout handling in check_timedout_devices() due to a race it can happen, that tcmu_set_next_deadline() does not start a timer as expected: 1) Either tcmu_check_expired_ring_cmd() checks the inflight_queue or tcmu_check_expired_queue_cmd() checks the qfull_queue while jiffies has the value X 2) At the end of the check the queue contains one remaining command with deadline X (time_after(X, X) is false and thus the command is not handled as being timed out). 3) After tcmu_check_expired_xxxxx_cmd() a timer interrupt happens and jiffies is incremented to X+1. 4) Now tcmu_set_next_deadline() is called, but it skips the command, since time_after(X+1, X) is true. Therefore tcmu_set_next_deadline() finds no new deadline and stops the timer, which it shouldn't. Since commands that time out are removed from inflight_queue or qfull_queue, we don't need the check with time_after() in tcmu_set_next_deadline(), but can use the deadline from the first cmd in the queue. Additionally I replaced the remaining time_after() calls in tcmu_check_expired_xxxxx_cmd() with time_after_eq(), because it is not useful to set the timeout to deadline, but then check for jiffies being greater than deadline. Next I simplified the end of tcmu_handle_completions() and changed the check for no more pending commands from "mb->cmd_tail == mb->cmd_head" to "idr_is_empty(&udev->commands)" because the old check doesn't work correctly if paddings or in the future TMRs are in the ring. Finally tcmu_set_next_deadline() was shifted in the source as preparation for later implementation of tmr_notify callback. Signed-off-by: Bodo Stroesser --- drivers/target/target_core_user.c | 59 +++++++++++++++------------------------ 1 file changed, 23 insertions(+), 36 deletions(-) diff --git a/drivers/target/target_core_user.c b/drivers/target/target_core_user.c index f10d8d182ed9..89f38355a2ab 100644 --- a/drivers/target/target_core_user.c +++ b/drivers/target/target_core_user.c @@ -1129,6 +1129,18 @@ tcmu_queue_cmd(struct se_cmd *se_cmd) return scsi_ret; } +static void tcmu_set_next_deadline(struct list_head *queue, + struct timer_list *timer) +{ + struct tcmu_cmd *cmd; + + if (!list_empty(queue)) { + cmd = list_first_entry(queue, struct tcmu_cmd, queue_entry); + mod_timer(timer, cmd->deadline); + } else + del_timer(timer); +} + static void tcmu_handle_completion(struct tcmu_cmd *cmd, struct tcmu_cmd_entry *entry) { struct se_cmd *se_cmd = cmd->se_cmd; @@ -1196,25 +1208,6 @@ static void tcmu_handle_completion(struct tcmu_cmd *cmd, struct tcmu_cmd_entry * tcmu_free_cmd(cmd); } -static void tcmu_set_next_deadline(struct list_head *queue, - struct timer_list *timer) -{ - struct tcmu_cmd *tcmu_cmd, *tmp_cmd; - unsigned long deadline = 0; - - list_for_each_entry_safe(tcmu_cmd, tmp_cmd, queue, queue_entry) { - if (!time_after(jiffies, tcmu_cmd->deadline)) { - deadline = tcmu_cmd->deadline; - break; - } - } - - if (deadline) - mod_timer(timer, deadline); - else - del_timer(timer); -} - static unsigned int tcmu_handle_completions(struct tcmu_dev *udev) { struct tcmu_mailbox *mb; @@ -1267,22 +1260,16 @@ static unsigned int tcmu_handle_completions(struct tcmu_dev *udev) handled++; } - if (mb->cmd_tail == mb->cmd_head) { - /* no more pending commands */ - del_timer(&udev->cmd_timer); - - if (list_empty(&udev->qfull_queue)) { - /* - * no more pending or waiting commands so try to - * reclaim blocks if needed. - */ - if (atomic_read(&global_db_count) > - tcmu_global_max_blocks) - schedule_delayed_work(&tcmu_unmap_work, 0); - } - } else if (udev->cmd_time_out) { - tcmu_set_next_deadline(&udev->inflight_queue, &udev->cmd_timer); + if (atomic_read(&global_db_count) > tcmu_global_max_blocks && + idr_is_empty(&udev->commands) && list_empty(&udev->qfull_queue)) { + /* + * Allocated blocks exceeded global block limit, currently no + * more pending or waiting commands so try to reclaim blocks. + */ + schedule_delayed_work(&tcmu_unmap_work, 0); } + if (udev->cmd_time_out) + tcmu_set_next_deadline(&udev->inflight_queue, &udev->cmd_timer); return handled; } @@ -1291,7 +1278,7 @@ static void tcmu_check_expired_ring_cmd(struct tcmu_cmd *cmd) { struct se_cmd *se_cmd; - if (!time_after(jiffies, cmd->deadline)) + if (!time_after_eq(jiffies, cmd->deadline)) return; set_bit(TCMU_CMD_BIT_EXPIRED, &cmd->flags); @@ -1310,7 +1297,7 @@ static void tcmu_check_expired_queue_cmd(struct tcmu_cmd *cmd) { struct se_cmd *se_cmd; - if (!time_after(jiffies, cmd->deadline)) + if (!time_after_eq(jiffies, cmd->deadline)) return; pr_debug("Timing out queued cmd %p on dev %s.\n",