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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1B26CC433EF for ; Thu, 14 Jul 2022 18:50:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232310AbiGNStx (ORCPT ); Thu, 14 Jul 2022 14:49:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35808 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239146AbiGNStp (ORCPT ); Thu, 14 Jul 2022 14:49:45 -0400 Received: from mail-pj1-f45.google.com (mail-pj1-f45.google.com [209.85.216.45]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6586925E89 for ; Thu, 14 Jul 2022 11:49:44 -0700 (PDT) Received: by mail-pj1-f45.google.com with SMTP id a15so3709433pjs.0 for ; Thu, 14 Jul 2022 11:49:44 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:message-id:date:mime-version:user-agent:subject :content-language:to:cc:references:from:in-reply-to :content-transfer-encoding; bh=+zKy5g2YDAb5huifDDSF/8JUexdcTAQ89IVa8OT51pw=; b=RQbojeR0Yf5yBdR2R65CI80/Tx3f0hrY0icFwCy/PnQB7RDAK6FvPXfBPhtJJlc+7l TWnmIaSftcbXVrkksIkmFm4BU0F2YVDjygk5p5MryUO17cYjD9bj2FYWl7/k3YZksEXo iEs4mZgxUe/6kc+ESz87mA1VrcufPE46v9dc0RRDTXuKovsypzXQoDoqeJythdt7+Ccp 6WsdsHqCku6qszxKYenuVFmpPhbZ4AamXt5mmunf1zOTa2jcMv7zB259zMKazuYgNzW+ z7hEHOYBCV6BMDP+cwRa9sj9IMNi5MVzJsqjDNlz2hcot32/vpofO+lmNjj3imGJdZ3O zfjw== X-Gm-Message-State: AJIora8LnJXjfqNEqkDtwHmNrpgagoRHwBy1/Mumjpe1RYU8hvmXeIdA Bpgvwrv+WMf1CnVYsvyKU4eENAYa74U= X-Google-Smtp-Source: AGRyM1sz4KJyilFWnNKZbQks9xUhq4UaX1JNjBUUZDmwzR1gvsu6St8UUpvneXWKnT2l1YX1voLzpQ== X-Received: by 2002:a17:903:191:b0:16c:3d49:b0c8 with SMTP id z17-20020a170903019100b0016c3d49b0c8mr9659827plg.95.1657824583851; Thu, 14 Jul 2022 11:49:43 -0700 (PDT) Received: from ?IPV6:2620:15c:211:201:9fab:70d1:f0e7:922b? ([2620:15c:211:201:9fab:70d1:f0e7:922b]) by smtp.gmail.com with ESMTPSA id 125-20020a620483000000b00528c4c770c5sm2051215pfe.77.2022.07.14.11.49.42 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 14 Jul 2022 11:49:43 -0700 (PDT) Message-ID: <4ba6ff46-435a-9ea4-e928-7f168162f4c0@acm.org> Date: Thu, 14 Jul 2022 11:49:41 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.10.0 Subject: Re: [PATCH v4 4/4] scsi: core: Call blk_mq_free_tag_set() earlier Content-Language: en-US To: John Garry , "Martin K . Petersen" Cc: Jaegeuk Kim , linux-scsi@vger.kernel.org, Christoph Hellwig , Ming Lei , Mike Christie , Hannes Reinecke , Li Zhijian References: <20220712221936.1199196-1-bvanassche@acm.org> <20220712221936.1199196-5-bvanassche@acm.org> <3c0f352a-0be6-7322-3556-8ce0d66ba8f3@huawei.com> <98e6554a-5d88-fcb6-d46d-a267009da014@acm.org> From: Bart Van Assche In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org On 7/14/22 05:25, John Garry wrote: > On 13/07/2022 21:04, Bart Van Assche wrote: >>>> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c >>>> index 2aca0a838ca5..295c48fdb650 100644 >>>> --- a/drivers/scsi/scsi_lib.c >>>> +++ b/drivers/scsi/scsi_lib.c >>>> @@ -1990,7 +1990,10 @@ int scsi_mq_setup_tags(struct Scsi_Host *shost) >>>>   void scsi_mq_destroy_tags(struct Scsi_Host *shost) >>>>   { >>>> +    if (!shost->tag_set.tags) >>>> +        return; >>>>       blk_mq_free_tag_set(&shost->tag_set); >>>> +    WARN_ON_ONCE(shost->tag_set.tags); >>> >>> blk_mq_free_tag_set() clears the tagset tags pointer, so I don't know >>> why you don't trust the semantics of that API - this seems like >>> paranoia. >> >> Semantics of the API? Shouldn't this rather be called an undocumented >> aspect of blk_mq_free_tag_set()? >> >> My concern is that the "set->tags = NULL" statement might be removed >> in the future from blk_mq_free_tag_set() and also that it is possible >> that scsi_mq_destroy_tags() is not updated after that change. > > Sure, so how it is possible that set->tags == NULL ever when calling > scsi_mq_setup_tags()? I'm just wondering why you even care. How about applying the patch below on top of patch 4/4? diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index 295c48fdb650..2aca0a838ca5 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -1990,10 +1990,7 @@ int scsi_mq_setup_tags(struct Scsi_Host *shost) void scsi_mq_destroy_tags(struct Scsi_Host *shost) { - if (!shost->tag_set.tags) - return; blk_mq_free_tag_set(&shost->tag_set); - WARN_ON_ONCE(shost->tag_set.tags); } Thanks, Bart.