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=-13.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 34167C433B4 for ; Fri, 23 Apr 2021 13:59:37 +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 74B0D61261 for ; Fri, 23 Apr 2021 13:59:36 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 74B0D61261 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:51714 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lZwLH-0002Lk-Cy for qemu-devel@archiver.kernel.org; Fri, 23 Apr 2021 09:59:35 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:43214) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lZwKU-0001oG-VX for qemu-devel@nongnu.org; Fri, 23 Apr 2021 09:58:46 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:49796) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lZwKT-000115-Dj for qemu-devel@nongnu.org; Fri, 23 Apr 2021 09:58:46 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1619186324; 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: in-reply-to:in-reply-to:references:references; bh=v07IoICeAJQMsfrCPEyIXiLlT9uBgi40d0NbZq3lww8=; b=DHCJUFKfdhrVGx7WGfG6vDJj0ISocAUHAbPaLjk74+Ww4QgKK3k6rX2MK9kC7oMmYLdUgR 6KYPOKkWa2fxaSVRLQsAHM03kewQQsdnb2F/giwLHR8qleLaAbH0UGmkDTZh0bT2YFfyFV l21mGhohNCzCPbsyBQ7YB4INcaSl1ik= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-557-jK6SNaIzNVm1e_2hQ4bJTQ-1; Fri, 23 Apr 2021 09:58:42 -0400 X-MC-Unique: jK6SNaIzNVm1e_2hQ4bJTQ-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 951DE83DD2E; Fri, 23 Apr 2021 13:58:41 +0000 (UTC) Received: from merkur.fritz.box (ovpn-114-199.ams2.redhat.com [10.36.114.199]) by smtp.corp.redhat.com (Postfix) with ESMTPS id A70846090F; Fri, 23 Apr 2021 13:58:40 +0000 (UTC) Date: Fri, 23 Apr 2021 15:58:39 +0200 From: Kevin Wolf To: Vladimir Sementsov-Ogievskiy Subject: Re: [PATCH v2 1/2] block: Add BDRV_O_NO_SHARE for blk_new_open() Message-ID: References: <20210422164344.283389-1-kwolf@redhat.com> <20210422164344.283389-2-kwolf@redhat.com> <23f7a203-8b94-4bde-a06d-3ade7924eddf@virtuozzo.com> MIME-Version: 1.0 In-Reply-To: <23f7a203-8b94-4bde-a06d-3ade7924eddf@virtuozzo.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=kwolf@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=216.205.24.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, 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: qemu-devel@nongnu.org, qemu-block@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Am 23.04.2021 um 11:43 hat Vladimir Sementsov-Ogievskiy geschrieben: > 22.04.2021 19:43, Kevin Wolf wrote: > > Normally, blk_new_open() just shares all permissions. This was fine > > originally when permissions only protected against uses in the same > > process because no other part of the code would actually get to access > > the block nodes opened with blk_new_open(). However, since we use it for > > file locking now, unsharing permissions becomes desirable. > > > > Add a new BDRV_O_NO_SHARE flag that is used in blk_new_open() to unshare > > any permissions that can be unshared. > > > > Signed-off-by: Kevin Wolf > > --- > > include/block/block.h | 1 + > > block/block-backend.c | 19 +++++++++++++------ > > 2 files changed, 14 insertions(+), 6 deletions(-) > > > > diff --git a/include/block/block.h b/include/block/block.h > > index b3f6e509d4..735db05a39 100644 > > --- a/include/block/block.h > > +++ b/include/block/block.h > > @@ -101,6 +101,7 @@ typedef struct HDGeometry { > > uint32_t cylinders; > > } HDGeometry; > > +#define BDRV_O_NO_SHARE 0x0001 /* don't share permissons */ > > #define BDRV_O_RDWR 0x0002 > > #define BDRV_O_RESIZE 0x0004 /* request permission for resizing the node */ > > #define BDRV_O_SNAPSHOT 0x0008 /* open the file read only and save writes in a snapshot */ > > diff --git a/block/block-backend.c b/block/block-backend.c > > index 413af51f3b..61a10ea860 100644 > > --- a/block/block-backend.c > > +++ b/block/block-backend.c > > @@ -398,15 +398,19 @@ BlockBackend *blk_new_open(const char *filename, const char *reference, > > BlockBackend *blk; > > BlockDriverState *bs; > > uint64_t perm = 0; > > + uint64_t shared = BLK_PERM_ALL; > > - /* blk_new_open() is mainly used in .bdrv_create implementations and the > > - * tools where sharing isn't a concern because the BDS stays private, so we > > - * just request permission according to the flags. > > + /* > > + * blk_new_open() is mainly used in .bdrv_create implementations and the > > + * tools where sharing isn't a major concern because the BDS stays private > > + * and the file is generally not supposed to be used by a second process, > > + * so we just request permission according to the flags. > > * > > * The exceptions are xen_disk and blockdev_init(); in these cases, the > > * caller of blk_new_open() doesn't make use of the permissions, but they > > * shouldn't hurt either. We can still share everything here because the > > - * guest devices will add their own blockers if they can't share. */ > > + * guest devices will add their own blockers if they can't share. > > + */ > > Probably old comment "We can still share everything" is a bit in > conflict with commit message (and new logic). I read that paragraph as referring to xen_disk and blockdev_init() only, which still don't pass BDRV_O_NO_SHARE after this series. The comment explains why they don't have to pass it. Kevin