From patchwork Thu Jun 23 22:37:06 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Blake X-Patchwork-Id: 639950 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org 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 ozlabs.org (Postfix) with ESMTPS id 3rbGpx5JNsz9sXx for ; Fri, 24 Jun 2016 08:48:57 +1000 (AEST) Received: from localhost ([::1]:39789 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bGDQd-00081C-LE for incoming@patchwork.ozlabs.org; Thu, 23 Jun 2016 18:48:55 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:60974) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bGDFr-0003zb-Ei for qemu-devel@nongnu.org; Thu, 23 Jun 2016 18:37:48 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bGDFn-0005vj-Jb for qemu-devel@nongnu.org; Thu, 23 Jun 2016 18:37:46 -0400 Received: from mx1.redhat.com ([209.132.183.28]:46831) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bGDFa-0005oo-RP; Thu, 23 Jun 2016 18:37:30 -0400 Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 5D29264373; Thu, 23 Jun 2016 22:37:30 +0000 (UTC) Received: from red.redhat.com (ovpn-116-212.phx2.redhat.com [10.3.116.212]) by int-mx11.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id u5NMbSVH010930; Thu, 23 Jun 2016 18:37:29 -0400 From: Eric Blake To: qemu-devel@nongnu.org Date: Thu, 23 Jun 2016 16:37:06 -0600 Message-Id: <1466721446-27737-3-git-send-email-eblake@redhat.com> In-Reply-To: <1466721446-27737-1-git-send-email-eblake@redhat.com> References: <1466721446-27737-1-git-send-email-eblake@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.24 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.39]); Thu, 23 Jun 2016 22:37:30 +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: [Qemu-devel] [PATCH v3 02/22] block: Document supported flags during bdrv_aligned_preadv() 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, famz@redhat.com, stefanha@redhat.com, qemu-block@nongnu.org, Max Reitz Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" We don't pass any flags on to drivers to handle. Tighten an assert to explain why we pass 0 to bdrv_driver_preadv(), and add some comments on things to be aware of if we want to turn on per-BDS BDRV_REQ_FUA support during reads in the future. Also, document that we may want to consider using unmap during copy-on-read operations where the read is all zeroes. Signed-off-by: Eric Blake Reviewed-by: Kevin Wolf Reviewed-by: Fam Zheng Reviewed-by: Stefan Hajnoczi --- v3: no change v2: retitle from 'Honor flags during bdrv_aligned_preadv()', and change scope of patch --- block/io.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/block/io.c b/block/io.c index b95e856..994d3fa 100644 --- a/block/io.c +++ b/block/io.c @@ -945,6 +945,9 @@ static int coroutine_fn bdrv_co_do_copy_on_readv(BlockDriverState *bs, if (drv->bdrv_co_pwrite_zeroes && buffer_is_zero(bounce_buffer, iov.iov_len)) { + /* FIXME: Should we (perhaps conditionally) be setting + * BDRV_REQ_MAY_UNMAP, if it will allow for a sparser copy + * that still correctly reads as zero? */ ret = bdrv_co_do_pwrite_zeroes(bs, cluster_offset, cluster_bytes, 0); } else { /* This does not change the data on the disk, it is not necessary @@ -987,7 +990,12 @@ static int coroutine_fn bdrv_aligned_preadv(BlockDriverState *bs, assert((bytes & (align - 1)) == 0); assert(!qiov || bytes == qiov->size); assert((bs->open_flags & BDRV_O_NO_IO) == 0); - assert(!(flags & ~BDRV_REQ_MASK)); + + /* TODO: We would need a per-BDS .supported_read_flags and + * potential fallback support, if we ever implement any read flags + * to pass through to drivers. For now, there aren't any + * passthrough flags. */ + assert(!(flags & ~(BDRV_REQ_NO_SERIALISING | BDRV_REQ_COPY_ON_READ))); /* Handle Copy on Read and associated serialisation */ if (flags & BDRV_REQ_COPY_ON_READ) {