From: Jeff Cody <jc...@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 <ebl...@redhat.com>
Signed-off-by: Jeff Cody <jc...@redhat.com>
Message-Id:
<9516d2684d419e1bfa2a95f66d2e9a70a4ff7eb7.1403723862.git.jc...@redhat.com>
[id_wellformed() rejects generated names, which means we can't collide]
Signed-off-by: Eric Blake <ebl...@redhat.com>
---
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;
}
--
2.4.3
