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=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 BD14BC282C7 for ; Tue, 29 Jan 2019 11:48:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8A63C20882 for ; Tue, 29 Jan 2019 11:48:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1548762518; bh=vPhOnKxnmz9Ow6jt8BCzni8kgWzcgThBnVOoq+PqC8o=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=HQGCCc0E1tdQodE7rI9XEurk4QOA3ibEqeI6E6PObgqjYCOLihAGn01UYb3QK7Bqt ymO6BTpmwGdh6TgShQg5BAh6ycxpANklzoD0Rc/VzcDjccLEWgtkScwsZQCUGPIdx0 JmDWwlAsZdA4JhpaoigrEd/2BHG3s/Y3NTE0zfNA= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731362AbfA2Lsh (ORCPT ); Tue, 29 Jan 2019 06:48:37 -0500 Received: from mail.kernel.org ([198.145.29.99]:39484 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731349AbfA2Lsf (ORCPT ); Tue, 29 Jan 2019 06:48:35 -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 2C1102086C; Tue, 29 Jan 2019 11:48:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1548762514; bh=vPhOnKxnmz9Ow6jt8BCzni8kgWzcgThBnVOoq+PqC8o=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=YcSkRknrt4HTo7nBkvDDUFWnAlF/AVfHOq0R86Zkt4tunWSN1zaQxtJ0SSBpRAOWJ vhK011A2kbfB28VWd86xbc89ZonkNaxZlo2upaMHwEV6yXRLfD9KH2tBqo0ZFg9ahn AXfZCX1ENUxTYwNfvJhOZLiN52O4F2ocie/YPhV0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Pavel Shilovsky , Steve French Subject: [PATCH 4.14 30/68] CIFS: Fix possible hang during async MTU reads and writes Date: Tue, 29 Jan 2019 12:35:52 +0100 Message-Id: <20190129113134.115975097@linuxfoundation.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190129113131.751891514@linuxfoundation.org> References: <20190129113131.751891514@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: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.14-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 @@ -153,14 +153,14 @@ 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);