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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 C9018C433DF for ; Tue, 16 Jun 2020 15:57:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A9C62207C4 for ; Tue, 16 Jun 2020 15:57:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592323042; bh=HYWquZViGbGdIcbesak3htJvfn2PAB/KpqgGhH9wMTg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=cjD8Cm2RCtJdJmyA+EdHnHSwM/VVHJApdXpdd4NU5uQGtMwMDxJZZBUw4ayU9QuSc +7riOJuk8mJXEYjnYdKweaOTwqicYNvUbs1ijF3urENRs/fROBpaQYMFkRPWBdhnTH PWkpmrZ/46WfU4QROCUsj4jfPHFaUTYrMGULWjEY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732993AbgFPP5Q (ORCPT ); Tue, 16 Jun 2020 11:57:16 -0400 Received: from mail.kernel.org ([198.145.29.99]:55462 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732659AbgFPPzY (ORCPT ); Tue, 16 Jun 2020 11:55:24 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 7B78521532; Tue, 16 Jun 2020 15:55:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592322924; bh=HYWquZViGbGdIcbesak3htJvfn2PAB/KpqgGhH9wMTg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=v3bPteUVlKdnCT9O9Rh59KldQYFsJbYfkbqc6HgQqKRMI7dik0qiYaWIe10Ahxk+V yrt1Trvtl4jThpOZUkkVhksTSr8nw3DsNHrIY4xlyi2xZL6Xf6tAcTF1AOlC6lCoBq w8I/2OBP1X5p3XPP59Mn24osT5oQcImYHq9c+Aos= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Libor Pechacek , Jiri Kosina , Jens Axboe Subject: [PATCH 5.6 156/161] block/floppy: fix contended case in floppy_queue_rq() Date: Tue, 16 Jun 2020 17:35:46 +0200 Message-Id: <20200616153113.776518867@linuxfoundation.org> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20200616153106.402291280@linuxfoundation.org> References: <20200616153106.402291280@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Jiri Kosina commit 263c61581a38d0a5ad1f5f4a9143b27d68caeffd upstream. Since the switch of floppy driver to blk-mq, the contended (fdc_busy) case in floppy_queue_rq() is not handled correctly. In case we reach floppy_queue_rq() with fdc_busy set (i.e. with the floppy locked due to another request still being in-flight), we put the request on the list of requests and return BLK_STS_OK to the block core, without actually scheduling delayed work / doing further processing of the request. This means that processing of this request is postponed until another request comes and passess uncontended. Which in some cases might actually never happen and we keep waiting indefinitely. The simple testcase is for i in `seq 1 2000`; do echo -en $i '\r'; blkid --info /dev/fd0 2> /dev/null; done run in quemu. That reliably causes blkid eventually indefinitely hanging in __floppy_read_block_0() waiting for completion, as the BIO callback never happens, and no further IO is ever submitted on the (non-existent) floppy device. This was observed reliably on qemu-emulated device. Fix that by not queuing the request in the contended case, and return BLK_STS_RESOURCE instead, so that blk core handles the request rescheduling and let it pass properly non-contended later. Fixes: a9f38e1dec107a ("floppy: convert to blk-mq") Cc: stable@vger.kernel.org Tested-by: Libor Pechacek Signed-off-by: Jiri Kosina Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- drivers/block/floppy.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) --- a/drivers/block/floppy.c +++ b/drivers/block/floppy.c @@ -2902,17 +2902,17 @@ static blk_status_t floppy_queue_rq(stru (unsigned long long) current_req->cmd_flags)) return BLK_STS_IOERR; - spin_lock_irq(&floppy_lock); - list_add_tail(&bd->rq->queuelist, &floppy_reqs); - spin_unlock_irq(&floppy_lock); - if (test_and_set_bit(0, &fdc_busy)) { /* fdc busy, this new request will be treated when the current one is done */ is_alive(__func__, "old request running"); - return BLK_STS_OK; + return BLK_STS_RESOURCE; } + spin_lock_irq(&floppy_lock); + list_add_tail(&bd->rq->queuelist, &floppy_reqs); + spin_unlock_irq(&floppy_lock); + command_status = FD_COMMAND_NONE; __reschedule_timeout(MAXTIMEOUT, "fd_request"); set_fdc(0);