From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:41320) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Wzt6R-0000kR-Ty for qemu-devel@nongnu.org; Wed, 25 Jun 2014 15:43:39 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Wzt6K-00020k-9j for qemu-devel@nongnu.org; Wed, 25 Jun 2014 15:43:31 -0400 Received: from mx1.redhat.com ([209.132.183.28]:60489) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Wzt6K-00020Y-0p for qemu-devel@nongnu.org; Wed, 25 Jun 2014 15:43:24 -0400 From: Jeff Cody Date: Wed, 25 Jun 2014 15:43:12 -0400 Message-Id: <9516d2684d419e1bfa2a95f66d2e9a70a4ff7eb7.1403723862.git.jcody@redhat.com> In-Reply-To: References: In-Reply-To: References: Subject: [Qemu-devel] [PATCH v7 for 2.1 1/4] block: Auto-generate node_names for each BDS entry List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: kwolf@redhat.com, benoit.canet@irqsave.net, pkrempa@redhat.com, famz@redhat.com, stefanha@redhat.com 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 --- block.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) diff --git a/block.c b/block.c index def7e67..6d7901e 100644 --- a/block.c +++ b/block.c @@ -843,12 +843,26 @@ 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; + 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; } /* empty string node name is invalid */ -- 1.9.3