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=-20.2 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 F0A81C4338F for ; Wed, 4 Aug 2021 08:08:46 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 71B7860E96 for ; Wed, 4 Aug 2021 08:08:46 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 71B7860E96 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=nongnu.org Received: from localhost ([::1]:43658 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mBBxF-00048G-GS for qemu-devel@archiver.kernel.org; Wed, 04 Aug 2021 04:08:45 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:58934) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mBBvv-0002bu-CC for qemu-devel@nongnu.org; Wed, 04 Aug 2021 04:07:23 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:58664) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mBBvs-0006XB-JH for qemu-devel@nongnu.org; Wed, 04 Aug 2021 04:07:23 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1628064439; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=sDxbm940JsOSf0x2EP+cydrrvDNg+Ve2z3WOQXX3otU=; b=W1bpCPcks21EalkXIALoQpr6FqPgnvuCekazEweP5KyQgb9UsiulN4SIWqCzk+IMA+CfaU tFc+q5Mp02Buk/f8/2JIfWfWu/saAVprqi2zr6FfCVBqZTAEwbqZlDkYY3DxB29z38iwko n71xoY+GKvBaIk6tnA90vCQ96rDRFkg= Received: from mail-wm1-f71.google.com (mail-wm1-f71.google.com [209.85.128.71]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-460-OkVBjttqOq2-SwYyvKZw4A-1; Wed, 04 Aug 2021 04:07:18 -0400 X-MC-Unique: OkVBjttqOq2-SwYyvKZw4A-1 Received: by mail-wm1-f71.google.com with SMTP id o26-20020a05600c511ab0290252d0248251so488575wms.1 for ; Wed, 04 Aug 2021 01:07:18 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-transfer-encoding :content-language; bh=sDxbm940JsOSf0x2EP+cydrrvDNg+Ve2z3WOQXX3otU=; b=nPAAb8bkf3ublBn+bhwBtK/MF3Npzm6m4tV1QImhgpXewedqctT9iU+bCzSmKx/Dsd UDs683fD0U/y7BcW6Br31NTLCFE4xviHKwAGWymLcbhheZLI3ZZ6rAVtl2XjuC8y0pfw in8yPcTbgOqiZlYnGW2WbU7pAK//2WflKy0I3u1zFcuaBn5tUWUIhGPSA7FPYZJxcadG 3GBnO+X7B2rRyezu+Sd3GLtj1oaK+piZ+zowhoTTqHugDpItkTzNdKQEkOeoY2o+vzAJ iZUk+JBz9tvcckfbb2RW6N+T9anP2YAMavyZxkiPBpbPP/Qv3koKL2W+B7aOx9cu85wf ZW3Q== X-Gm-Message-State: AOAM531+NUvPFeF0mL00myaCk+XY9Y0XAmTpowhse0vuVyFSWr+Mb9dm EgVWwWMPbSkt8eknbgkChLpp0+n0AlGILf9jsClTrQ6CfOCtQFSmZjSD+KtHIF/5klEtl0mI8+9 NPsCgHy5hy3wxrxE= X-Received: by 2002:adf:db07:: with SMTP id s7mr28364333wri.106.1628064437348; Wed, 04 Aug 2021 01:07:17 -0700 (PDT) X-Google-Smtp-Source: ABdhPJzYSrPke5hOp+2BuTc1qi731TvimMwIS5Y3vWnnxtHUTcGTsoCFPooL3u+fF38VKY63K28E8A== X-Received: by 2002:adf:db07:: with SMTP id s7mr28364295wri.106.1628064437016; Wed, 04 Aug 2021 01:07:17 -0700 (PDT) Received: from dresden.str.redhat.com ([2a02:908:1e46:160:b272:8083:d5:bc7d]) by smtp.gmail.com with ESMTPSA id f194sm5169607wmf.23.2021.08.04.01.07.16 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 04 Aug 2021 01:07:16 -0700 (PDT) Subject: Re: [PATCH for-6.1? v2 5/7] job: Add job_cancel_requested() To: Kevin Wolf References: <20210726144613.954844-1-mreitz@redhat.com> <20210726144613.954844-6-mreitz@redhat.com> From: Max Reitz Message-ID: <13d07f4b-9659-4576-1757-a7d75f7e16c2@redhat.com> Date: Wed, 4 Aug 2021 10:07:15 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mreitz@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Received-SPF: pass client-ip=170.10.133.124; envelope-from=mreitz@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -34 X-Spam_score: -3.5 X-Spam_bar: --- X-Spam_report: (-3.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.699, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Vladimir Sementsov-Ogievskiy , John Snow , qemu-devel@nongnu.org, qemu-block@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 03.08.21 16:25, Kevin Wolf wrote: > Am 26.07.2021 um 16:46 hat Max Reitz geschrieben: >> Most callers of job_is_cancelled() actually want to know whether the job >> is on its way to immediate termination. For example, we refuse to pause >> jobs that are cancelled; but this only makes sense for jobs that are >> really actually cancelled. >> >> A mirror job that is cancelled during READY with force=false should >> absolutely be allowed to pause. This "cancellation" (which is actually >> a kind of completion) may take an indefinite amount of time, and so >> should behave like any job during normal operation. For example, with >> on-target-error=stop, the job should stop on write errors. (In >> contrast, force-cancelled jobs should not get write errors, as they >> should just terminate and not do further I/O.) >> >> Therefore, redefine job_is_cancelled() to only return true for jobs that >> are force-cancelled (which as of HEAD^ means any job that interprets the >> cancellation request as a request for immediate termination), and add >> job_cancel_request() as the general variant, which returns true for any >> jobs which have been requested to be cancelled, whether it be >> immediately or after an arbitrarily long completion phase. >> >> Buglink: https://gitlab.com/qemu-project/qemu/-/issues/462 >> Signed-off-by: Max Reitz >> --- >> include/qemu/job.h | 8 +++++++- >> block/mirror.c | 10 ++++------ >> job.c | 7 ++++++- >> 3 files changed, 17 insertions(+), 8 deletions(-) >> >> diff --git a/include/qemu/job.h b/include/qemu/job.h >> index 8aa90f7395..032edf3c5f 100644 >> --- a/include/qemu/job.h >> +++ b/include/qemu/job.h >> @@ -436,9 +436,15 @@ const char *job_type_str(const Job *job); >> /** Returns true if the job should not be visible to the management layer. */ >> bool job_is_internal(Job *job); >> >> -/** Returns whether the job is scheduled for cancellation. */ >> +/** Returns whether the job is being cancelled. */ >> bool job_is_cancelled(Job *job); >> >> +/** >> + * Returns whether the job is scheduled for cancellation (at an >> + * indefinite point). >> + */ >> +bool job_cancel_requested(Job *job); > I don't think non-force blockdev-cancel for mirror should actually be > considered cancellation, so what is the question that this function > answers? > > "Is this a cancelled job, or a mirror block job that is supposed to > complete soon, but only if it doesn't switch over the users to the > target on completion"? Well, technically yes, but it was more intended as “Has the user ever invoked (block-)job-cancel on this job?”. > Is this ever a reasonable question to ask, except maybe inside the > mirror implementation itself? I asked myself the same for v3, but found two places in job.c where I would like to keep it: First, there’s an assertion in job_completed_txn_abort().  All jobs other than @job have been force-cancelled, and so job_is_cancelled() would be true for them.  As for @job itself, the function is mostly called when the job’s return value is not 0, but a soft-cancelled mirror does have a return value of 0 and so would not end up in that function. But job_cancel() invokes job_completed_txn_abort() if the job has been deferred to the main loop, which mostly correlates with the job having been completed (in which case the assertion is skipped), but not 100 % (there’s a small window between setting deferred_to_main_loop and the job changing to a completed state). So I’d prefer to keep the assertion as-is functionally, i.e. to only check job->cancelled. Second, job_complete() refuses to let a job complete that has been cancelled.  This function is basically only invoked by the user (through qmp_block_job_complete()/qmp_job_complete(), or job_complete_sync(), which comes from qemu-img), so I believe that it should correspond to the external interface we have right now; i.e., if the user has invoked (block-)job-cancel at one point, job_complete() should generally return an error. > job_complete() is the only function outside of mirror that seems to use > it. But even there, it feels wrong to make a difference. Either we > accept redundant completion requests, or we don't. It doesn't really > matter how the job reconfigures the graph on completion. (Also, I feel > this should really have been part of the state machine, but I'm not sure > if we want to touch it now...) Well, yes, I don’t think it makes a difference because I don’t think anyone will first tell the job via block-job-cancel to complete without pivoting, and then change their mind and call block-job-complete after all.  (Not least because that’s an error pre-series.) Also, I’m not even sure whether completing after a soft cancel request works.  I don’t think any of our code accounts for such a case, so I’d rather avoid allowing it if there’s no need to allow it anyway. Max