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 X-Spam-Level: X-Spam-Status: No, score=-5.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_PASS 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 46BD4C04EB8 for ; Tue, 4 Dec 2018 16:47:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0DF7920834 for ; Tue, 4 Dec 2018 16:47:55 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=broadcom.com header.i=@broadcom.com header.b="DKYNPZPF" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0DF7920834 Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=broadcom.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-block-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726420AbeLDQry (ORCPT ); Tue, 4 Dec 2018 11:47:54 -0500 Received: from mail-it1-f193.google.com ([209.85.166.193]:40925 "EHLO mail-it1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726367AbeLDQry (ORCPT ); Tue, 4 Dec 2018 11:47:54 -0500 Received: by mail-it1-f193.google.com with SMTP id h193so15444589ita.5 for ; Tue, 04 Dec 2018 08:47:53 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=broadcom.com; s=google; h=from:references:in-reply-to:mime-version:thread-index:date :message-id:subject:to:cc; bh=6MtSRmCm6aVdDzQRFtm/H2PxQChCgFBt62rSyJRDfY4=; b=DKYNPZPFhTQN7x/R7ek88o7NDH9e7soL4Tc2g0LFGsIesKfOzkWbE7MFWzxX9/+ZsY ktjccDySznGxoDQuFyL3tM4uGz9IkKM1nHVQwlhhs3+kbDssi7/CN/96mmtaqSZCH2xK n1A/yK4NaOYtyMzxo9B1sFk0L8Hl3vp0oPEXw= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:references:in-reply-to:mime-version :thread-index:date:message-id:subject:to:cc; bh=6MtSRmCm6aVdDzQRFtm/H2PxQChCgFBt62rSyJRDfY4=; b=Q5tpb3wHS8j0MKolarPKiC5g/jp2vjHYWWOPHKobTVR23mRQDeEOSV5Mp7ViQJqnKy ffujphsb34FSnqsdgS5WsbBAtew+iMCn2JwB+E5vk/1fcUmzvtvNIHu3mEX8N00Tu7FI GpmbgMf0TB09/V0z14+fwjyLv5zzqd5dJj8TuMirjKfBOOJKT4j/CjuARHpdOSNMgr8W ovte48IIt+5Ur6Ib5G0BYpkZxnMablxZHcl9DZeB3yOmSXpdpWyAAM7rBu4TRq+qo7Vu kbvqCSnjwgk3e8hZkNxLkUTx52RicpKZ+ufsdra0I6p/UlCrMI5Q//IuN0zW9dVvP6zo PM2A== X-Gm-Message-State: AA+aEWZKkyWEG/des+pduniqNG1V7B5JzeuTJWY95Bw+JBBv6BBZLa6o k0ScepBxbqZlGdP8cZsMZKVF9XAEo0CBhhlk8f4gRw== X-Google-Smtp-Source: AFSGD/UZTVaRplDEr6WiA5Mq/xqho6/OXRNRvHRDKis3E0ogU98riKidymMdmrhWYkijBDhapdOXoYcf9hF1FnGmqhE= X-Received: by 2002:a05:660c:3c7:: with SMTP id c7mr5300247itl.131.1543942073307; Tue, 04 Dec 2018 08:47:53 -0800 (PST) From: Kashyap Desai References: <7e8e1fe2-9f91-a370-a98c-43cdad1f6e8e@acm.org> In-Reply-To: <7e8e1fe2-9f91-a370-a98c-43cdad1f6e8e@acm.org> MIME-Version: 1.0 X-Mailer: Microsoft Outlook 14.0 Thread-Index: AQEyvrdX27HdOCj1DHPKEZclYJ8CJQEQPyI2pqnfvSA= Date: Tue, 4 Dec 2018 22:17:51 +0530 Message-ID: Subject: RE: [PATCH] blk-mq: Set request mapping to NULL in blk_mq_put_driver_tag To: Bart Van Assche , linux-block , Jens Axboe , Ming Lei , linux-scsi Cc: Suganath Prabu Subramani , Sreekanth Reddy , Sathya Prakash Veerichetty Content-Type: text/plain; charset="UTF-8" Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org + Linux-scsi > > diff --git a/block/blk-mq.h b/block/blk-mq.h > > index 9497b47..57432be 100644 > > --- a/block/blk-mq.h > > +++ b/block/blk-mq.h > > @@ -175,6 +175,7 @@ static inline bool > > blk_mq_get_dispatch_budget(struct blk_mq_hw_ctx *hctx) > > static inline void __blk_mq_put_driver_tag(struct blk_mq_hw_ctx *hctx, > > struct request *rq) > > { > > + hctx->tags->rqs[rq->tag] = NULL; > > blk_mq_put_tag(hctx, hctx->tags, rq->mq_ctx, rq->tag); > > rq->tag = -1; > > No SCSI driver should call scsi_host_find_tag() after a request has > finished. The above patch introduces yet another race and hence can't be > a proper fix. Bart, many scsi drivers use scsi_host_find_tag() to traverse max tag_id to find out pending IO in firmware. One of the use case is - HBA firmware recovery. In case of firmware recovery, driver may require to traverse the list and return back pending scsi command to SML for retry. I quickly grep the scsi code and found that snic_scsi, qla4xxx, fnic, mpt3sas are using API scsi_host_find_tag for the same purpose. Without this patch, we hit very basic kernel panic due to page fault. This is not an issue in non-mq code path. Non-mq path use blk_map_queue_find_tag() and that particular API does not provide stale requests. Kashyap > > Bart.