Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751588AbaGJKdJ (ORCPT ); Thu, 10 Jul 2014 06:33:09 -0400 Received: from mail-vc0-f179.google.com ([209.85.220.179]:36769 "EHLO mail-vc0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750778AbaGJKdH (ORCPT ); Thu, 10 Jul 2014 06:33:07 -0400 MIME-Version: 1.0 In-Reply-To: <9b76360fb30745d3941b6d56bdae268f@BY2PR03MB299.namprd03.prod.outlook.com> References: <1404866789-26910-1-git-send-email-kys@microsoft.com> <1404866812-26950-1-git-send-email-kys@microsoft.com> <1404866812-26950-6-git-send-email-kys@microsoft.com> <20140709084415.GF6012@infradead.org> <9b76360fb30745d3941b6d56bdae268f@BY2PR03MB299.namprd03.prod.outlook.com> Date: Thu, 10 Jul 2014 12:33:05 +0200 Message-ID: Subject: Re: [PATCH 6/8] Drivers: scsi: storvsc: Implement an abort handler From: Richard Weinberger To: KY Srinivasan Cc: Christoph Hellwig , "linux-kernel@vger.kernel.org" , "devel@linuxdriverproject.org" , "ohering@suse.com" , "jbottomley@parallels.com" , "jasowang@redhat.com" , "apw@canonical.com" , "linux-scsi@vger.kernel.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 9, 2014 at 8:51 PM, KY Srinivasan wrote: > > >> -----Original Message----- >> From: Christoph Hellwig [mailto:hch@infradead.org] >> Sent: Wednesday, July 9, 2014 1:44 AM >> To: KY Srinivasan >> Cc: linux-kernel@vger.kernel.org; devel@linuxdriverproject.org; >> ohering@suse.com; jbottomley@parallels.com; jasowang@redhat.com; >> apw@canonical.com; linux-scsi@vger.kernel.org >> Subject: Re: [PATCH 6/8] Drivers: scsi: storvsc: Implement an abort handler >> >> On Tue, Jul 08, 2014 at 05:46:50PM -0700, K. Y. Srinivasan wrote: >> > Implement a simple abort handler. The host does not support "Abort"; >> > just ensure that all inflight I/Os have been accounted for. >> >> The abort handler should abort a single command, not wait for all of them. >> What issue do you see that this tries to address? > > On Azure, we sometimes have unbounded I/O latencies and some distributions (such as SLES12) based on recent kernels are invoking > the "Abort Handler". Unfortunately, our scsi emulation on the host does not support aborting a command. > The issue I have seen is that the upper level scsi code attempts error recovery when the command times out and finally frees up the command. > The host subsequently responds to the command that has timed out and since the memory has been freed up, we end up touching freed memory > in this driver. Since the host is also doing error recovery, by just delaying the error handler in the guest until we can account for all the in-flight commands, > we can get around the problem. I see strange issues in Azure and maybe they are related to this. Some Linux machines crash in a way that no disk IO is possible (thus, no SSH for me) but they still respond to ping. It happens rather seldom (every few weeks). Do you see similar symptoms? -- Thanks, //richard -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/