hmp: 'drive_add -n' for creating a node without BB

This patch adds an option to the drive_add HMP command to create only a
BlockDriverState without a BlockBackend on top.

The motivation for this is that libvirt needs to specify options to a
migration target (specifically, detect-zeroes). drive-mirror doesn't
allow specifying options, and the proper way to do this is to create the
target BDS separately with blockdev-add (where you can specify options)
and then use blockdev-mirror to that BDS.

However, libvirt can't use blockdev-add as long as it is still
experimental, and we're expecting that it will still take some time, so
we need to resort to drive_add.

The problem with drive_add is that so far it always created a BB, and
BDSes with a BB can't be used as a mirroring target as long as we don't
support multiple BBs per BDS - and while we're working towards that
goal, it's another thing that will still take some time.

So to achieve the goal, the simplest solution to provide the
functionality now without adding one-off options to the mirror QMP
commands is to extend drive_add to create nodes without BBs.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>

diff --git a/blockdev.c b/blockdev.c
index 1824cae259052c3874887e43da332045eff98a96..1297c90512c5442cdef7ee8ba8ada8746d3b80a5 100644 (file)
--- a/blockdev.c
+++ b/blockdev.c
@@ -3875,6 +3875,36 @@ out:
     aio_context_release(aio_context);
 }
 
+void hmp_drive_add_node(Monitor *mon, const char *optstr)
+{
+    QemuOpts *opts;
+    QDict *qdict;
+    Error *local_err = NULL;
+
+    opts = qemu_opts_parse_noisily(&qemu_drive_opts, optstr, false);
+    if (!opts) {
+        return;
+    }
+
+    qdict = qemu_opts_to_qdict(opts, NULL);
+
+    if (!qdict_get_try_str(qdict, "node-name")) {
+        error_report("'node-name' needs to be specified");
+        goto out;
+    }
+
+    BlockDriverState *bs = bds_tree_init(qdict, &local_err);
+    if (!bs) {
+        error_report_err(local_err);
+        goto out;
+    }
+
+    QTAILQ_INSERT_TAIL(&monitor_bdrv_states, bs, monitor_list);
+
+out:
+    qemu_opts_del(opts);
+}
+
 void qmp_blockdev_add(BlockdevOptions *options, Error **errp)
 {
     QmpOutputVisitor *ov = qmp_output_visitor_new();

diff --git a/device-hotplug.c b/device-hotplug.c
index 9a7cd669d5bedbf7114fe8ab6715e0f0718410ed..3e5cdaad109e24daf5a14dac1a2945eb8778b079 100644 (file)
--- a/device-hotplug.c
+++ b/device-hotplug.c
@@ -30,6 +30,7 @@
 #include "qemu/config-file.h"
 #include "sysemu/sysemu.h"
 #include "monitor/monitor.h"
+#include "block/block_int.h"
 
 static DriveInfo *add_init_drive(const char *optstr)
 {
@@ -55,6 +56,12 @@ void hmp_drive_add(Monitor *mon, const QDict *qdict)
 {
     DriveInfo *dinfo = NULL;
     const char *opts = qdict_get_str(qdict, "opts");
+    bool node = qdict_get_try_bool(qdict, "node", false);
+
+    if (node) {
+        hmp_drive_add_node(mon, opts);
+        return;
+    }
 
     dinfo = add_init_drive(opts);
     if (!dinfo) {

diff --git a/hmp-commands.hx b/hmp-commands.hx
index 639205b692922b5e9df8450cc017a03a27741e4e..4f4f60a0dfd20bd6d37f19ceda17579098eb885e 100644 (file)
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -1201,8 +1201,8 @@ ETEXI
 
     {
         .name       = "drive_add",
-        .args_type  = "pci_addr:s,opts:s",
-        .params     = "[[<domain>:]<bus>:]<slot>\n"
+        .args_type  = "node:-n,pci_addr:s,opts:s",
+        .params     = "[-n] [[<domain>:]<bus>:]<slot>\n"
                       "[file=file][,if=type][,bus=n]\n"
                       "[,unit=m][,media=d][,index=i]\n"
                       "[,cyls=c,heads=h,secs=s[,trans=t]]\n"

diff --git a/include/block/block_int.h b/include/block/block_int.h
index 9ef823a660fc9b257cad147b8284e59526f3dacb..dda5ba0927ec59a82c8ea27f4413f0ea45d33051 100644 (file)
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -694,6 +694,8 @@ void backup_start(BlockDriverState *bs, BlockDriverState *target,
                   BlockCompletionFunc *cb, void *opaque,
                   BlockJobTxn *txn, Error **errp);
 
+void hmp_drive_add_node(Monitor *mon, const char *optstr);
+
 void blk_set_bs(BlockBackend *blk, BlockDriverState *bs);
 
 void blk_dev_change_media_cb(BlockBackend *blk, bool load);