Having to fire up qemu, then use QMP commands for nbd-server-start
and nbd-server-add, just to expose a persistent dirty bitmap, is
rather tedious. Make it possible to expose a dirty bitmap using
just qemu-nbd (of course, for now this only works when qemu-nbd is
visiting a BDS formatted as qcow2).
For now, I play it safe and only allow a bitmap to be exposed on
a read-only image. We may relax it in the future.
Signed-off-by: Eric Blake <ebl...@redhat.com>
---
qemu-nbd.texi | 5 +++++
qemu-nbd.c | 16 ++++++++++++++--
2 files changed, 19 insertions(+), 2 deletions(-)
diff --git a/qemu-nbd.texi b/qemu-nbd.texi
index 9a84e81eed9..1bf9d2bd8bf 100644
--- a/qemu-nbd.texi
+++ b/qemu-nbd.texi
@@ -45,6 +45,11 @@ auto-detecting
Export the disk as read-only
@item -P, --partition=@var{num}
Only expose partition @var{num}
+@item -B, --bitmap=@var{name}
+If @var{filename} has a qcow2 persistent bitmap @var{name}, expose
+that bitmap via the ``qemu:dirty-bitmap:@var{name}'' context
+accessible through NBD_OPT_SET_META_CONTEXT. Requires the use of
+@option{-r}.
@item -s, --snapshot
Use @var{filename} as an external snapshot, create a temporary
file with backing_file=@var{filename}, redirect the write to
diff --git a/qemu-nbd.c b/qemu-nbd.c
index a6cc0f2553e..9781efe7a25 100644
--- a/qemu-nbd.c
+++ b/qemu-nbd.c
@@ -95,6 +95,7 @@ static void usage(const char *name)
"Exposing part of the image:\n"
" -o, --offset=OFFSET offset into the image\n"
" -P, --partition=NUM only expose partition NUM\n"
+" -B, --bitmap=NAME expose a persistent dirty bitmap\n"
"\n"
"General purpose options:\n"
" --object type,id=ID,... define an object such as 'secret' for providing\n"
@@ -509,7 +510,7 @@ int main(int argc, char **argv)
off_t fd_size;
QemuOpts *sn_opts = NULL;
const char *sn_id_or_name = NULL;
- const char *sopt = "hVb:o:p:rsnP:c:dvk:e:f:tl:x:T:D:";
+ const char *sopt = "hVb:o:p:rsnP:c:dvk:e:f:tl:x:T:D:B:";
struct option lopt[] = {
{ "help", no_argument, NULL, 'h' },
{ "version", no_argument, NULL, 'V' },
@@ -519,6 +520,7 @@ int main(int argc, char **argv)
{ "offset", required_argument, NULL, 'o' },
{ "read-only", no_argument, NULL, 'r' },
{ "partition", required_argument, NULL, 'P' },
+ { "bitmap", required_argument, NULL, 'B' },
{ "connect", required_argument, NULL, 'c' },
{ "disconnect", no_argument, NULL, 'd' },
{ "snapshot", no_argument, NULL, 's' },
@@ -558,6 +560,7 @@ int main(int argc, char **argv)
QDict *options = NULL;
const char *export_name = ""; /* Default export name */
const char *export_description = NULL;
+ const char *bitmap = NULL;
const char *tlscredsid = NULL;
bool imageOpts = false;
bool writethrough = true;
@@ -695,6 +698,9 @@ int main(int argc, char **argv)
exit(EXIT_FAILURE);
}
break;
+ case 'B':
+ bitmap = optarg;
+ break;
case 'k':
sockpath = optarg;
if (sockpath[0] != '/') {
@@ -822,6 +828,12 @@ int main(int argc, char **argv)
}
}
+ if (bitmap && !(nbdflags & NBD_FLAG_READ_ONLY)) {
+ error_report("Exporting bitmap '%s' requires a readonly export",
+ bitmap);
+ exit(EXIT_FAILURE);
+ }
+
#if !HAVE_NBD_DEVICE
if (disconnect || device) {
error_report("Kernel /dev/nbdN support not available");
@@ -1015,7 +1027,7 @@ int main(int argc, char **argv)
}
}
- exp = nbd_export_new(bs, dev_offset, fd_size, export_name, NULL, NULL,
+ exp = nbd_export_new(bs, dev_offset, fd_size, export_name, bitmap, NULL,
export_description, nbdflags, nbd_export_closed,
writethrough, NULL, &error_fatal);
--
2.20.1
