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=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 29625C7618B for ; Thu, 25 Jul 2019 15:29:12 +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 0360821951 for ; Thu, 25 Jul 2019 15:29:12 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0360821951 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]:32880 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hqfg7-00032B-AN for qemu-devel@archiver.kernel.org; Thu, 25 Jul 2019 11:29:11 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:48294) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hqffv-0002Wm-P6 for qemu-devel@nongnu.org; Thu, 25 Jul 2019 11:29:00 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hqffu-0000lm-JE for qemu-devel@nongnu.org; Thu, 25 Jul 2019 11:28:59 -0400 Received: from mx1.redhat.com ([209.132.183.28]:56168) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hqffr-0000kD-N7; Thu, 25 Jul 2019 11:28:55 -0400 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 08CAC300CA4D; Thu, 25 Jul 2019 15:28:55 +0000 (UTC) Received: from maximlenovopc.usersys.redhat.com (unknown [10.35.206.87]) by smtp.corp.redhat.com (Postfix) with ESMTP id 9A18D1001E75; Thu, 25 Jul 2019 15:28:53 +0000 (UTC) Message-ID: <08fa9a1e04f8c92d66897b57054b0cf6fc5c3cb7.camel@redhat.com> From: Maxim Levitsky To: Max Reitz , qemu-block@nongnu.org Date: Thu, 25 Jul 2019 18:28:52 +0300 In-Reply-To: <20190724171239.8764-4-mreitz@redhat.com> References: <20190724171239.8764-1-mreitz@redhat.com> <20190724171239.8764-4-mreitz@redhat.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.42]); Thu, 25 Jul 2019 15:28:55 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [PATCH v2 03/11] block: Add bdrv_has_zero_init_truncate() 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: Kevin Wolf , qemu-devel@nongnu.org, Stefano Garzarella Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, 2019-07-24 at 19:12 +0200, Max Reitz wrote: > No .bdrv_has_zero_init() implementation returns 1 if growing the file > would add non-zero areas (at least with PREALLOC_MODE_OFF), so using it > in lieu of this new function was always safe. > > But on the other hand, it is possible that growing an image that is not > zero-initialized would still add a zero-initialized area, like when > using nonpreallocating truncation on a preallocated image. For callers > that care only about truncation, not about creation with potential > preallocation, this new function is useful. > > Alternatively, we could have added a PreallocMode parameter to > bdrv_has_zero_init(). But the only user would have been qemu-img > convert, which does not have a plain PreallocMode value right now -- it > would have to parse the creation option to obtain it. Therefore, the > simpler solution is to let bdrv_has_zero_init() inquire the > preallocation status and add the new bdrv_has_zero_init_truncate() that > presupposes PREALLOC_MODE_OFF. > > Signed-off-by: Max Reitz > --- > include/block/block.h | 1 + > include/block/block_int.h | 7 +++++++ > block.c | 21 +++++++++++++++++++++ > 3 files changed, 29 insertions(+) > > diff --git a/include/block/block.h b/include/block/block.h > index 50a07c1c33..5321d8afdf 100644 > --- a/include/block/block.h > +++ b/include/block/block.h > @@ -438,6 +438,7 @@ int bdrv_pdiscard(BdrvChild *child, int64_t offset, int64_t bytes); > int bdrv_co_pdiscard(BdrvChild *child, int64_t offset, int64_t bytes); > int bdrv_has_zero_init_1(BlockDriverState *bs); > int bdrv_has_zero_init(BlockDriverState *bs); > +int bdrv_has_zero_init_truncate(BlockDriverState *bs); > bool bdrv_unallocated_blocks_are_zero(BlockDriverState *bs); > bool bdrv_can_write_zeroes_with_unmap(BlockDriverState *bs); > int bdrv_block_status(BlockDriverState *bs, int64_t offset, > diff --git a/include/block/block_int.h b/include/block/block_int.h > index 6a0b1b5008..d7fc6b296b 100644 > --- a/include/block/block_int.h > +++ b/include/block/block_int.h > @@ -420,9 +420,16 @@ struct BlockDriver { > /* > * Returns 1 if newly created images are guaranteed to contain only > * zeros, 0 otherwise. > + * Must return 0 if .bdrv_has_zero_init_truncate() returns 0. > */ > int (*bdrv_has_zero_init)(BlockDriverState *bs); > > + /* > + * Returns 1 if new areas added by growing the image with > + * PREALLOC_MODE_OFF contain only zeros, 0 otherwise. > + */ > + int (*bdrv_has_zero_init_truncate)(BlockDriverState *bs); > + > /* Remove fd handlers, timers, and other event loop callbacks so the event > * loop is no longer in use. Called with no in-flight requests and in > * depth-first traversal order with parents before child nodes. > diff --git a/block.c b/block.c > index cbd8da5f3b..81ae44dcf3 100644 > --- a/block.c > +++ b/block.c > @@ -5066,6 +5066,27 @@ int bdrv_has_zero_init(BlockDriverState *bs) > return 0; > } > > +int bdrv_has_zero_init_truncate(BlockDriverState *bs) > +{ > + if (!bs->drv) { > + return 0; > + } > + > + if (bs->backing) { > + /* Depends on the backing image length, but better safe than sorry */ > + return 0; > + } > + if (bs->drv->bdrv_has_zero_init_truncate) { > + return bs->drv->bdrv_has_zero_init_truncate(bs); > + } > + if (bs->file && bs->drv->is_filter) { > + return bdrv_has_zero_init_truncate(bs->file->bs); > + } > + > + /* safe default */ > + return 0; > +} > + > bool bdrv_unallocated_blocks_are_zero(BlockDriverState *bs) > { > BlockDriverInfo bdi; This looks like a very correct change, even for the sake of clarifying the scope of bdrv_has_zero_init Reviewed-by: Maxim Levitsky Best regards, Maxim Levitsky