From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CE715C433EF for ; Thu, 7 Oct 2021 07:19:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B35E2610FB for ; Thu, 7 Oct 2021 07:19:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240339AbhJGHVV (ORCPT ); Thu, 7 Oct 2021 03:21:21 -0400 Received: from mail.kernel.org ([198.145.29.99]:45280 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232512AbhJGHVU (ORCPT ); Thu, 7 Oct 2021 03:21:20 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 23AC96101E; Thu, 7 Oct 2021 07:19:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1633591167; bh=KKqVxcZ+QAOzW+phGrvFAsuLInJucEfq92yEOpG6WQ4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=qxd83c0Wg+rBywZnrCBO5uy9em4f0fxoiKZ+mHv9zmxhHisWiTt3dWjTw+09SyPdK h1Zymeuh9+XDc5nJy9lEjqUNKC0CkMgu4+TGpxmrA85P9YRiDk25SyIi/emGAsk2h/ O+M4tV0u7XB03ShplumtC25duKm/GZQdVZwnLakY= Date: Thu, 7 Oct 2021 09:19:25 +0200 From: Greg Kroah-Hartman To: Ming Lei Cc: "Martin K . Petersen" , linux-scsi@vger.kernel.org, Changhui Zhong , Yi Zhang Subject: Re: [PATCH V3] scsi: core: put LLD module refcnt after SCSI device is released Message-ID: References: <20210930124415.1160754-1-ming.lei@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org On Thu, Oct 07, 2021 at 03:12:52PM +0800, Ming Lei wrote: > On Tue, Oct 05, 2021 at 03:35:40PM +0200, Greg Kroah-Hartman wrote: > > On Thu, Sep 30, 2021 at 08:44:15PM +0800, Ming Lei wrote: > > > SCSI host release is triggered when SCSI device is freed, and we have to > > > make sure that LLD module won't be unloaded before SCSI host instance is > > > released because shost->hostt is required in host release handler. > > > > > > So make sure to put LLD module refcnt after SCSI device is released. > > > > What is a "LLD"? > > Lower level driver, which is used often as one scsi term. > > > > > > Fix one kernel panic of 'BUG: unable to handle page fault for address' > > > reported by Changhui and Yi. > > > > > > Reported-by: Changhui Zhong > > > Reported-by: Yi Zhang > > > Cc: Greg Kroah-Hartman > > > Signed-off-by: Ming Lei > > > --- > > > drivers/scsi/scsi.c | 4 +++- > > > drivers/scsi/scsi_sysfs.c | 12 ++++++++++++ > > > include/scsi/scsi_device.h | 1 + > > > 3 files changed, 16 insertions(+), 1 deletion(-) > > > > > > diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c > > > index b241f9e3885c..291ecc33b1fe 100644 > > > --- a/drivers/scsi/scsi.c > > > +++ b/drivers/scsi/scsi.c > > > @@ -553,8 +553,10 @@ EXPORT_SYMBOL(scsi_device_get); > > > */ > > > void scsi_device_put(struct scsi_device *sdev) > > > { > > > - module_put(sdev->host->hostt->module); > > > + struct module *mod = sdev->host->hostt->module; > > > + > > > put_device(&sdev->sdev_gendev); > > > + module_put(mod); > > > } > > > EXPORT_SYMBOL(scsi_device_put); > > > > > > diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c > > > index 86793259e541..9ada26814011 100644 > > > --- a/drivers/scsi/scsi_sysfs.c > > > +++ b/drivers/scsi/scsi_sysfs.c > > > @@ -449,9 +449,16 @@ static void scsi_device_dev_release_usercontext(struct work_struct *work) > > > struct scsi_vpd *vpd_pg80 = NULL, *vpd_pg83 = NULL; > > > struct scsi_vpd *vpd_pg0 = NULL, *vpd_pg89 = NULL; > > > unsigned long flags; > > > + struct module *mod; > > > + bool put_mod = false; > > > > > > sdev = container_of(work, struct scsi_device, ew.work); > > > > > > + if (sdev->put_lld_mod_ref) { > > > > Why do you need this flag at all? > > > > Shouldn't you just always grab/release the module? Why would you not > > want to? > > try_module_get() may fail in scsi_device_dev_release() in case that > unloading is started, then we don't need to put it in > scsi_device_dev_release_usercontext(), so this flag is required. If grabing the module reference failed then you CAN NOT call into it so you have a problem here that you seem to be papering over. Just set the module pointer to NULL and then you don't need to test it when calling module_put, right? thanks, greg k-h