From patchwork Thu May 4 03:07:47 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Blake X-Patchwork-Id: 9710735 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id A7DD060362 for ; Thu, 4 May 2017 03:09:47 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 980C528636 for ; Thu, 4 May 2017 03:09:47 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 8983C2863A; Thu, 4 May 2017 03:09:47 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 05A4728636 for ; Thu, 4 May 2017 03:09:46 +0000 (UTC) Received: from localhost ([::1]:39507 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1d679G-0003Df-1y for patchwork-qemu-devel@patchwork.kernel.org; Wed, 03 May 2017 23:09:46 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:52476) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1d677h-0002u4-55 for qemu-devel@nongnu.org; Wed, 03 May 2017 23:08:11 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1d677f-0001Fz-US for qemu-devel@nongnu.org; Wed, 03 May 2017 23:08:09 -0400 Received: from mx1.redhat.com ([209.132.183.28]:53264) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1d677c-0001Dn-Ai; Wed, 03 May 2017 23:08:04 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 6D3704E339; Thu, 4 May 2017 03:08:03 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 6D3704E339 Authentication-Results: ext-mx09.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx09.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=eblake@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com 6D3704E339 Received: from red.redhat.com (ovpn-122-206.rdu2.redhat.com [10.10.122.206]) by smtp.corp.redhat.com (Postfix) with ESMTP id 97CA162923; Thu, 4 May 2017 03:08:02 +0000 (UTC) From: Eric Blake To: qemu-devel@nongnu.org Date: Wed, 3 May 2017 22:07:47 -0500 Message-Id: <20170504030755.1001-3-eblake@redhat.com> In-Reply-To: <20170504030755.1001-1-eblake@redhat.com> References: <20170504030755.1001-1-eblake@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Thu, 04 May 2017 03:08:03 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 209.132.183.28 Subject: [Qemu-devel] [PATCH v12 02/10] block: Update comments on BDRV_BLOCK_* meanings X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kwolf@redhat.com, qemu-block@nongnu.org, mreitz@redhat.com Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" X-Virus-Scanned: ClamAV using ClamSMTP We had some conflicting documentation: a nice 8-way table that described all possible combinations of DATA, ZERO, and OFFSET_VALID, contrasted with text that implied that OFFSET_VALID always meant raw data could be read directly. Furthermore, the text refers a lot to bs->file, even though the interface was updated back in 67a0fd2a to let the driver pass back which BDS (not necessarily bs->file). As the 8-way table is the intended semantics, simplify the rest of the text to get rid of the confusion. ALLOCATED is always set by the block layer for convenience (drivers do not have to worry about it). RAW is used only internally, but by more than the raw driver. Document these additional items on the driver callback. Suggested-by: Max Reitz Signed-off-by: Eric Blake Reviewed-by: Max Reitz --- v12: even more wording tweaks v11: reserved for blkdebug half of v10 v10: new patch --- include/block/block.h | 35 +++++++++++++++++++---------------- include/block/block_int.h | 7 +++++++ 2 files changed, 26 insertions(+), 16 deletions(-) diff --git a/include/block/block.h b/include/block/block.h index 862eb56..c8bec7d 100644 --- a/include/block/block.h +++ b/include/block/block.h @@ -120,29 +120,32 @@ typedef struct HDGeometry { #define BDRV_REQUEST_MAX_BYTES (BDRV_REQUEST_MAX_SECTORS << BDRV_SECTOR_BITS) /* - * Allocation status flags - * BDRV_BLOCK_DATA: data is read from a file returned by bdrv_get_block_status. - * BDRV_BLOCK_ZERO: sectors read as zero - * BDRV_BLOCK_OFFSET_VALID: sector stored as raw data in a file returned by - * bdrv_get_block_status. + * Allocation status flags for bdrv_get_block_status() and friends. + * + * Public flags: + * BDRV_BLOCK_DATA: allocation for data at offset is tied to this layer + * BDRV_BLOCK_ZERO: offset reads as zero + * BDRV_BLOCK_OFFSET_VALID: an associated offset exists for accessing raw data * BDRV_BLOCK_ALLOCATED: the content of the block is determined by this - * layer (as opposed to the backing file) - * BDRV_BLOCK_RAW: used internally to indicate that the request - * was answered by the raw driver and that one - * should look in bs->file directly. + * layer (short for DATA || ZERO), set by block layer * - * If BDRV_BLOCK_OFFSET_VALID is set, bits 9-62 represent the offset in - * bs->file where sector data can be read from as raw data. + * Internal flag: + * BDRV_BLOCK_RAW: used internally to indicate that the request was + * answered by a passthrough driver such as raw and that the + * block layer should recompute the answer from bs->file. * - * DATA == 0 && ZERO == 0 means that data is read from backing_hd if present. + * If BDRV_BLOCK_OFFSET_VALID is set, bits 9-62 (BDRV_BLOCK_OFFSET_MASK) + * represent the offset in the returned BDS that is allocated for the + * corresponding raw data; however, whether that offset actually contains + * data also depends on BDRV_BLOCK_DATA and BDRV_BLOCK_ZERO, as follows: * * DATA ZERO OFFSET_VALID - * t t t sectors read as zero, bs->file is zero at offset - * t f t sectors read as valid from bs->file at offset - * f t t sectors preallocated, read as zero, bs->file not + * t t t sectors read as zero, returned file is zero at offset + * t f t sectors read as valid from file at offset + * f t t sectors preallocated, read as zero, returned file not * necessarily zero at offset * f f t sectors preallocated but read from backing_hd, - * bs->file contains garbage at offset + * returned file contains garbage at offset * t t f sectors preallocated, read as zero, unknown offset * t f f sectors read from unknown file or offset * f t f not allocated or unknown offset, read as zero diff --git a/include/block/block_int.h b/include/block/block_int.h index 8773940..1fdfff7 100644 --- a/include/block/block_int.h +++ b/include/block/block_int.h @@ -165,6 +165,13 @@ struct BlockDriver { int64_t offset, int count, BdrvRequestFlags flags); int coroutine_fn (*bdrv_co_pdiscard)(BlockDriverState *bs, int64_t offset, int count); + + /* + * Building block for bdrv_block_status[_above]. The driver should + * answer only according to the current layer, and should not + * set BDRV_BLOCK_ALLOCATED, but may set BDRV_BLOCK_RAW. See block.h + * for the meaning of _DATA, _ZERO, and _OFFSET_VALID. + */ int64_t coroutine_fn (*bdrv_co_get_block_status)(BlockDriverState *bs, int64_t sector_num, int nb_sectors, int *pnum, BlockDriverState **file);