From patchwork Fri May 29 22:14:42 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Douglas Gilbert X-Patchwork-Id: 213846 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=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, 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 9D815C433DF for ; Fri, 29 May 2020 22:14:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7DDED20897 for ; Fri, 29 May 2020 22:14:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726943AbgE2WOw (ORCPT ); Fri, 29 May 2020 18:14:52 -0400 Received: from smtp.infotech.no ([82.134.31.41]:33540 "EHLO smtp.infotech.no" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725808AbgE2WOw (ORCPT ); Fri, 29 May 2020 18:14:52 -0400 Received: from localhost (localhost [127.0.0.1]) by smtp.infotech.no (Postfix) with ESMTP id 6D4F020418F; Sat, 30 May 2020 00:14:51 +0200 (CEST) X-Virus-Scanned: by amavisd-new-2.6.6 (20110518) (Debian) at infotech.no Received: from smtp.infotech.no ([127.0.0.1]) by localhost (smtp.infotech.no [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id dM3OZ+jHoiRk; Sat, 30 May 2020 00:14:45 +0200 (CEST) Received: from xtwo70.bingwo.ca (host-23-251-188-50.dyn.295.ca [23.251.188.50]) by smtp.infotech.no (Postfix) with ESMTPA id C514F20415B; Sat, 30 May 2020 00:14:44 +0200 (CEST) From: Douglas Gilbert To: linux-scsi@vger.kernel.org Cc: martin.petersen@oracle.com, jejb@linux.vnet.ibm.com, hare@suse.de, bvanassche@acm.org Subject: [PATCH 1/1] scsi: scsi_forget_host() shuffle Date: Fri, 29 May 2020 18:14:42 -0400 Message-Id: <20200529221442.8404-1-dgilbert@interlog.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Sender: linux-scsi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org This patch leaves me a bit uneasy but it does cure the crash that occurs in this function. xarray iterators are pretty safe _unless_ something deletes the parent node holding the collection. The problem seems to be these nested loops do not _explicitly_ remove the starget object. That is done magically at the sdev level on the removal of the last sdev in a starget. And that is half an iteration too soon! Hence the shuffle which isn't a great solution. The magical starget removal is wrong IMO and this will burn us elsewhere, I suspect. Thes patch is on top of Hannes Reinecke's "[PATCHv4 0/5] scsi: use xarray for devices and targets" patchset. Signed-off-by: Douglas Gilbert --- drivers/scsi/scsi_scan.c | 47 +++++++++++++++++++++++++++++++--------- 1 file changed, 37 insertions(+), 10 deletions(-) diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c index 0a344653487d..e378f03d0297 100644 --- a/drivers/scsi/scsi_scan.c +++ b/drivers/scsi/scsi_scan.c @@ -1858,25 +1858,52 @@ void scsi_scan_host(struct Scsi_Host *shost) } EXPORT_SYMBOL(scsi_scan_host); +static void scsi_forget_host_inner(struct Scsi_Host *shost, + struct scsi_target *starg, + unsigned long *flagsp) +{ + struct scsi_device *sdev; + struct scsi_device *prev_sdev = NULL; + unsigned long lun_id; + + xa_for_each(&starg->__devices, lun_id, sdev) { + if (sdev->sdev_state == SDEV_DEL) + continue; + if (!prev_sdev) { + prev_sdev = sdev; + continue; + } + spin_unlock_irqrestore(shost->host_lock, *flagsp); + __scsi_remove_device(prev_sdev); + spin_lock_irqsave(shost->host_lock, *flagsp); + prev_sdev = sdev; + } + if (prev_sdev) { + spin_unlock_irqrestore(shost->host_lock, *flagsp); + __scsi_remove_device(prev_sdev); + spin_lock_irqsave(shost->host_lock, *flagsp); + } +} + +/* N.B. Keeping iteration one step ahead of destruction point */ void scsi_forget_host(struct Scsi_Host *shost) { struct scsi_target *starget; - struct scsi_device *sdev; + struct scsi_target *prev_starget = NULL; unsigned long flags; - unsigned long tid = 0; + unsigned long tid; spin_lock_irqsave(shost->host_lock, flags); xa_for_each(&shost->__targets, tid, starget) { - unsigned long lun_id = 0; - - xa_for_each(&starget->__devices, lun_id, sdev) { - if (sdev->sdev_state == SDEV_DEL) - continue; - spin_unlock_irqrestore(shost->host_lock, flags); - __scsi_remove_device(sdev); - spin_lock_irqsave(shost->host_lock, flags); + if (!prev_starget) { + prev_starget = starget; + continue; } + scsi_forget_host_inner(shost, prev_starget, &flags); + prev_starget = starget; } + if (prev_starget) + scsi_forget_host_inner(shost, prev_starget, &flags); spin_unlock_irqrestore(shost->host_lock, flags); }