From patchwork Fri Oct 14 18:33:17 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Blake X-Patchwork-Id: 9377323 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 F11F8607FD for ; Fri, 14 Oct 2016 18:52:32 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id E27BD2A7BD for ; Fri, 14 Oct 2016 18:52:32 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id D5CC92A810; Fri, 14 Oct 2016 18:52:32 +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 634D52A7BD for ; Fri, 14 Oct 2016 18:52:32 +0000 (UTC) Received: from localhost ([::1]:48945 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bv7ap-0000re-HY for patchwork-qemu-devel@patchwork.kernel.org; Fri, 14 Oct 2016 14:52:31 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:39659) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bv7Ic-0002Xf-2P for qemu-devel@nongnu.org; Fri, 14 Oct 2016 14:33:43 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bv7Ia-0001fV-Nj for qemu-devel@nongnu.org; Fri, 14 Oct 2016 14:33:41 -0400 Received: from mx1.redhat.com ([209.132.183.28]:33814) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1bv7IT-0001cA-Jj; Fri, 14 Oct 2016 14:33:33 -0400 Received: from int-mx13.intmail.prod.int.phx2.redhat.com (int-mx13.intmail.prod.int.phx2.redhat.com [10.5.11.26]) (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 867B185365; Fri, 14 Oct 2016 18:33:32 +0000 (UTC) Received: from red.redhat.com (ovpn-116-53.phx2.redhat.com [10.3.116.53]) by int-mx13.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id u9EIXL1w001087; Fri, 14 Oct 2016 14:33:31 -0400 From: Eric Blake To: qemu-devel@nongnu.org Date: Fri, 14 Oct 2016 13:33:17 -0500 Message-Id: <1476469998-28592-16-git-send-email-eblake@redhat.com> In-Reply-To: <1476469998-28592-1-git-send-email-eblake@redhat.com> References: <1476469998-28592-1-git-send-email-eblake@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.26 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.25]); Fri, 14 Oct 2016 18:33:32 +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 v7 15/16] nbd: Implement NBD_CMD_WRITE_ZEROES on server 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: Kevin Wolf , pbonzini@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 Upstream NBD protocol recently added the ability to efficiently write zeroes without having to send the zeroes over the wire, along with a flag to control whether the client wants to allow a hole. Note that when it comes to requiring full allocation, vs. permitting optimizations, the NBD spec intentionally picked a different sense for the flag; the rules in qemu are: MAY_UNMAP == 0: must write zeroes MAY_UNMAP == 1: may use holes if reads will see zeroes while in NBD, the rules are: FLAG_NO_HOLE == 1: must write zeroes FLAG_NO_HOLE == 0: may use holes if reads will see zeroes In all cases, the 'may use holes' scenario is optional (the server need not use a hole, and must not use a hole if subsequent reads would not see zeroes). Signed-off-by: Eric Blake --- v6: rebase, improve commit message v5: no change v4: rebase, fix value for constant v3: abandon NBD_CMD_CLOSE extension, rebase to use blk_pwrite_zeroes --- include/block/nbd.h | 8 ++++++-- nbd/server.c | 42 ++++++++++++++++++++++++++++++++++++++++-- 2 files changed, 46 insertions(+), 4 deletions(-) diff --git a/include/block/nbd.h b/include/block/nbd.h index eea7ef0..3e373f0 100644 --- a/include/block/nbd.h +++ b/include/block/nbd.h @@ -71,6 +71,7 @@ typedef struct NBDReply NBDReply; #define NBD_FLAG_SEND_FUA (1 << 3) /* Send FUA (Force Unit Access) */ #define NBD_FLAG_ROTATIONAL (1 << 4) /* Use elevator algorithm - rotational media */ #define NBD_FLAG_SEND_TRIM (1 << 5) /* Send TRIM (discard) */ +#define NBD_FLAG_SEND_WRITE_ZEROES (1 << 6) /* Send WRITE_ZEROES */ /* New-style handshake (global) flags, sent from server to client, and control what will happen during handshake phase. */ @@ -96,7 +97,8 @@ typedef struct NBDReply NBDReply; #define NBD_REP_ERR_SHUTDOWN NBD_REP_ERR(7) /* Server shutting down */ /* Request flags, sent from client to server during transmission phase */ -#define NBD_CMD_FLAG_FUA (1 << 0) +#define NBD_CMD_FLAG_FUA (1 << 0) /* 'force unit access' during write */ +#define NBD_CMD_FLAG_NO_HOLE (1 << 1) /* don't punch hole on zero run */ /* Supported request types */ enum { @@ -104,7 +106,9 @@ enum { NBD_CMD_WRITE = 1, NBD_CMD_DISC = 2, NBD_CMD_FLUSH = 3, - NBD_CMD_TRIM = 4 + NBD_CMD_TRIM = 4, + /* 5 reserved for failed experiment NBD_CMD_CACHE */ + NBD_CMD_WRITE_ZEROES = 6, }; #define NBD_DEFAULT_PORT 10809 diff --git a/nbd/server.c b/nbd/server.c index 66dc484..ea234ae 100644 --- a/nbd/server.c +++ b/nbd/server.c @@ -617,7 +617,8 @@ static coroutine_fn int nbd_negotiate(NBDClientNewData *data) char buf[8 + 8 + 8 + 128]; int rc; const uint16_t myflags = (NBD_FLAG_HAS_FLAGS | NBD_FLAG_SEND_TRIM | - NBD_FLAG_SEND_FLUSH | NBD_FLAG_SEND_FUA); + NBD_FLAG_SEND_FLUSH | NBD_FLAG_SEND_FUA | + NBD_FLAG_SEND_WRITE_ZEROES); bool oldStyle; size_t len; @@ -1147,11 +1148,17 @@ static ssize_t nbd_co_receive_request(NBDRequestData *req, rc = request->type == NBD_CMD_WRITE ? -ENOSPC : -EINVAL; goto out; } - if (request->flags & ~NBD_CMD_FLAG_FUA) { + if (request->flags & ~(NBD_CMD_FLAG_FUA | NBD_CMD_FLAG_NO_HOLE)) { LOG("unsupported flags (got 0x%x)", request->flags); rc = -EINVAL; goto out; } + if (request->type != NBD_CMD_WRITE_ZEROES && + (request->flags & NBD_CMD_FLAG_NO_HOLE)) { + LOG("unexpected flags (got 0x%x)", request->flags); + rc = -EINVAL; + goto out; + } rc = 0; @@ -1256,6 +1263,37 @@ static void nbd_trip(void *opaque) } break; + case NBD_CMD_WRITE_ZEROES: + TRACE("Request type is WRITE_ZEROES"); + + if (exp->nbdflags & NBD_FLAG_READ_ONLY) { + TRACE("Server is read-only, return error"); + reply.error = EROFS; + goto error_reply; + } + + TRACE("Writing to device"); + + flags = 0; + if (request.flags & NBD_CMD_FLAG_FUA) { + flags |= BDRV_REQ_FUA; + } + if (!(request.flags & NBD_CMD_FLAG_NO_HOLE)) { + flags |= BDRV_REQ_MAY_UNMAP; + } + ret = blk_pwrite_zeroes(exp->blk, request.from + exp->dev_offset, + request.len, flags); + if (ret < 0) { + LOG("writing to file failed"); + reply.error = -ret; + goto error_reply; + } + + if (nbd_co_send_reply(req, &reply, 0) < 0) { + goto out; + } + break; + case NBD_CMD_DISC: /* unreachable, thanks to special case in nbd_co_receive_request() */ abort();