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=-6.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, 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 131DAC282CB for ; Mon, 4 Feb 2019 10:40:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CA4652070C for ; Mon, 4 Feb 2019 10:40:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1549276800; bh=wDiZCf4UOt3KFowd2RTqJe374vWRZY/KVFXFq5Ir8u0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=MsriIUb0PxGntWwH1MORMKHLv9gfqCt2+OS+VseqeNf5n8wQV8qbKnbMNEnMlqIDH GTfBjZVUO4UFFBtqa/z0Yyi0/rSwnIm+kAuHgDFENyQsKvGUa9DCYkZsMa9OF1GkGy ihkkH75+1k3E37sdr3vZIRoqfcGsydeWRZcVDAIg= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729872AbfBDKjy (ORCPT ); Mon, 4 Feb 2019 05:39:54 -0500 Received: from mail.kernel.org ([198.145.29.99]:37910 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729837AbfBDKjy (ORCPT ); Mon, 4 Feb 2019 05:39:54 -0500 Received: from localhost (5356596B.cm-6-7b.dynamic.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 5D4F72075B; Mon, 4 Feb 2019 10:39:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1549276793; bh=wDiZCf4UOt3KFowd2RTqJe374vWRZY/KVFXFq5Ir8u0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Q6rf417x1QCakN7WeQReYb6JdbfacvgAoNeYg8nFNViQDFDWmsApYG2CKhwgqKzva 6lGTRRlaLuLwbCDb6XlhvKQMsNZq97Z9PD1OzbA5DlCYYcR+rcDmX23MTdCFfEU60F d/ynHjxSsuuvRpZRZMNv6y1Fm5VLG5XxL/700/Ao= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Pavel Shilovsky , Steve French Subject: [PATCH 4.4 17/65] CIFS: Fix possible hang during async MTU reads and writes Date: Mon, 4 Feb 2019 11:36:10 +0100 Message-Id: <20190204103613.304866636@linuxfoundation.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190204103610.583715954@linuxfoundation.org> References: <20190204103610.583715954@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review X-Patchwork-Hint: ignore MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Pavel Shilovsky commit acc58d0bab55a50e02c25f00bd6a210ee121595f upstream. When doing MTU i/o we need to leave some credits for possible reopen requests and other operations happening in parallel. Currently we leave 1 credit which is not enough even for reopen only: we need at least 2 credits if durable handle reconnect fails. Also there may be other operations at the same time including compounding ones which require 3 credits at a time each. Fix this by leaving 8 credits which is big enough to cover most scenarios. Was able to reproduce this when server was configured to give out fewer credits than usual. The proper fix would be to reconnect a file handle first and then obtain credits for an MTU request but this leads to bigger code changes and should happen in other patches. Cc: Signed-off-by: Pavel Shilovsky Signed-off-by: Steve French Signed-off-by: Greg Kroah-Hartman --- fs/cifs/smb2ops.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) --- a/fs/cifs/smb2ops.c +++ b/fs/cifs/smb2ops.c @@ -143,14 +143,14 @@ smb2_wait_mtu_credits(struct TCP_Server_ scredits = server->credits; /* can deadlock with reopen */ - if (scredits == 1) { + if (scredits <= 8) { *num = SMB2_MAX_BUFFER_SIZE; *credits = 0; break; } - /* leave one credit for a possible reopen */ - scredits--; + /* leave some credits for reopen and other ops */ + scredits -= 8; *num = min_t(unsigned int, size, scredits * SMB2_MAX_BUFFER_SIZE);