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 4C7C6C282CB for ; Mon, 4 Feb 2019 11:11:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0ED53207E0 for ; Mon, 4 Feb 2019 11:11:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1549278717; bh=R5w5dNQg7o66DlSlqbyePCGoVB5X5ZkLty23U61zXeo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=RGDDAzPlFW/yH86e74Kp6t7G2eMgdIV8nUWnvN/0R3zfzYs0wabLAdtzyX1X9aCqr FQVfdxMhSBRc4bGtO2suluyncOzxNdvU5P1EO8vm2Qp2lrz0UEUzaLlxfUUkCc3yV3 46yhOkQupj5VAHfhmBHmWiPtWmhNfDnOL5SarZE0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729513AbfBDKit (ORCPT ); Mon, 4 Feb 2019 05:38:49 -0500 Received: from mail.kernel.org ([198.145.29.99]:36114 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728870AbfBDKiq (ORCPT ); Mon, 4 Feb 2019 05:38:46 -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 0A7262070C; Mon, 4 Feb 2019 10:38:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1549276725; bh=R5w5dNQg7o66DlSlqbyePCGoVB5X5ZkLty23U61zXeo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=zGZTk7vfb7G+s8ffvMurWhFiBpp/h+3QF2y+DjnnTwqrTsbyOxCp5m9izncQABd4I fGyQQNihqD6WPi1Sak8wXdbJnSybMLqrjh/XaMJxLM1aK3Hxoe0mWnMOhKFrCavLSj sfoQn7+vuTU9HCXa1mupj18ZrghFH2w+rixmwupc= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Pavel Shilovsky , Steve French Subject: [PATCH 3.18 08/31] CIFS: Fix possible hang during async MTU reads and writes Date: Mon, 4 Feb 2019 11:36:23 +0100 Message-Id: <20190204103559.731466635@linuxfoundation.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190204103557.903263774@linuxfoundation.org> References: <20190204103557.903263774@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 3.18-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);