From patchwork Mon Jun 22 23:10:39 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Blake X-Patchwork-Id: 487417 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 812F714010F for ; Tue, 23 Jun 2015 09:11:14 +1000 (AEST) Authentication-Results: ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=comcast.net header.i=@comcast.net header.b=k5MzUZNg; dkim-atps=neutral Received: from localhost ([::1]:42384 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Z7Arw-0002UC-7k for incoming@patchwork.ozlabs.org; Mon, 22 Jun 2015 19:11:12 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59214) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Z7Ara-00027G-Rn for qemu-devel@nongnu.org; Mon, 22 Jun 2015 19:10:52 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Z7ArW-0004k3-0K for qemu-devel@nongnu.org; Mon, 22 Jun 2015 19:10:50 -0400 Received: from resqmta-po-03v.sys.comcast.net ([96.114.154.162]:45023) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Z7ArV-0004jn-Gw for qemu-devel@nongnu.org; Mon, 22 Jun 2015 19:10:45 -0400 Received: from resomta-po-18v.sys.comcast.net ([96.114.154.242]) by resqmta-po-03v.sys.comcast.net with comcast id jbAd1q0045E3ZMc01bAk8r; Mon, 22 Jun 2015 23:10:44 +0000 Received: from red.redhat.com ([24.10.254.122]) by resomta-po-18v.sys.comcast.net with comcast id jbAh1q0012fD5rL01bAjS7; Mon, 22 Jun 2015 23:10:44 +0000 From: Eric Blake To: qemu-devel@nongnu.org Date: Mon, 22 Jun 2015 17:10:39 -0600 Message-Id: <1435014639-27341-1-git-send-email-eblake@redhat.com> X-Mailer: git-send-email 2.4.3 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=comcast.net; s=q20140121; t=1435014644; bh=klLelPObqSX65qINkd+rvrgWIRvGHdVf0ruo6sbjmkk=; h=Received:Received:From:To:Subject:Date:Message-Id; b=k5MzUZNgnffTeFMtEC3YJaRFZz9ax658bgFLRdXy6rZZw6g2o2hg3MdM4qp8od0vW pzQOKHGBjN1k1/Immif5Wt86Uwfd0CUuiMlhVSRqK/wVHTLLbK9/pAFF+25M7EC7F1 EweeIvYOV3j/Wj72y9+431LnXZ5adjXJV9NQVnNbZrgcv3Kf+0k/oE3Qai2tBpKV1J R8HcKBiB5RmR2dvalGLKgI4Yu0hbUSNdDDIdy4uGQYEXrG3JeaBZroSrvNTyeJB7p6 ggM8/Hl8QWSzfeqMt9v3C4lVfSzLmkMW7VDnhfqWB4zSwih21+hNRD1qMprAd2c0PN nvfznA6duJtgw== X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 96.114.154.162 Cc: Kevin Wolf , Jeff Cody , "open list:Block layer core" Subject: [Qemu-devel] [PATCHv2 for-2.4] block: Auto-generate node_names for each BDS entry X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org From: Jeff Cody Currently, node_name is only filled in when done so explicitly by the user. If no node_name is specified, then the node name field is not populated. If node_names are automatically generated when not specified, that means that all block job operations can be done by reference to the unique node_name field. This eliminates ambiguity in resolving filenames (relative filenames, or file descriptors, symlinks, mounts, etc..) that qemu currently needs to deal with. If a node name is specified, then it will not be automatically generated for that BDS entry. If it is automatically generated, it will be prefaced with "__qemu##", followed by 8 characters of a unique number, followed by 8 random ASCII characters in the range of 'A-Z'. Some sample generated node-name strings: __qemu##00000000IAIYNXXR __qemu##00000002METXTRBQ __qemu##00000001FMBORDWG The prefix is to aid in identifying it as a qemu-generated name, the numeric portion is to guarantee uniqueness in a given qemu session, and the random characters are to further avoid any accidental collisions with user-specified node-names. Reviewed-by: Eric Blake Signed-off-by: Jeff Cody Message-Id: <9516d2684d419e1bfa2a95f66d2e9a70a4ff7eb7.1403723862.git.jcody@redhat.com> [id_wellformed() rejects generated names, which means we can't collide] Signed-off-by: Eric Blake --- v2: revive this patch; very little needed changing I just posted a libvirt patch series that depends on this patch: https://www.redhat.com/archives/libvir-list/2015-June/msg01111.html As the original was posted by Jeff (nearly a year ago!), it counts as a patch that was submitted prior to soft freeze :) [I will be on vacation the next 3 weeks, so I may be slow to respond on replies to this message] block.c | 22 +++++++++++++++++----- 1 file changed, 17 insertions(+), 5 deletions(-) diff --git a/block.c b/block.c index dd4f58d..2532b70 100644 --- a/block.c +++ b/block.c @@ -765,16 +765,28 @@ static int bdrv_open_flags(BlockDriverState *bs, int flags) return open_flags; } +#define GEN_NODE_NAME_PREFIX "__qemu##" +#define GEN_NODE_NAME_MAX_LEN (sizeof(GEN_NODE_NAME_PREFIX) + 8 + 8) static void bdrv_assign_node_name(BlockDriverState *bs, const char *node_name, Error **errp) { + char gen_node_name[GEN_NODE_NAME_MAX_LEN]; + static uint32_t counter; /* simple counter to guarantee uniqueness */ + + /* if node_name is NULL, auto-generate a node name */ if (!node_name) { - return; - } - - /* Check for empty string or invalid characters */ - if (!id_wellformed(node_name)) { + int len; + snprintf(gen_node_name, GEN_NODE_NAME_MAX_LEN, + "%s%08x", GEN_NODE_NAME_PREFIX, counter++); + len = strlen(gen_node_name); + while (len < GEN_NODE_NAME_MAX_LEN - 1) { + gen_node_name[len++] = g_random_int_range('A', 'Z'); + } + gen_node_name[GEN_NODE_NAME_MAX_LEN - 1] = '\0'; + node_name = gen_node_name; + } else if (!id_wellformed(node_name)) { + /* Check for empty string or invalid characters */ error_setg(errp, "Invalid node name"); return; }