blockdev: add refcount to DriveInfo

The host part of a block device can be deleted with in progress
block migration.

To fix this, add a reference count to DriveInfo, freeing resources
on last reference.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
CC: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit 84fb392526479d54602a3830326d50d44657f630)

3 files changed, 20 insertions, 4 deletions

diff --git a/blockdev.c b/blockdev.c
index 1c56da0a16..f2a00bd214 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -71,7 +71,7 @@ void blockdev_auto_del(BlockDriverState *bs)
     DriveInfo *dinfo = drive_get_by_blockdev(bs);
 
     if (dinfo && dinfo->auto_del) {
-        drive_uninit(dinfo);
+        drive_put_ref(dinfo);
     }
 }
 
@@ -178,7 +178,7 @@ static void bdrv_format_print(void *opaque, const char *name)
     error_printf(" %s", name);
 }
 
-void drive_uninit(DriveInfo *dinfo)
+static void drive_uninit(DriveInfo *dinfo)
 {
     qemu_opts_del(dinfo->opts);
     bdrv_delete(dinfo->bdrv);
@@ -186,6 +186,19 @@ void drive_uninit(DriveInfo *dinfo)
     qemu_free(dinfo);
 }
 
+void drive_put_ref(DriveInfo *dinfo)
+{
+    assert(dinfo->refcount);
+    if (--dinfo->refcount == 0) {
+        drive_uninit(dinfo);
+    }
+}
+
+void drive_get_ref(DriveInfo *dinfo)
+{
+    dinfo->refcount++;
+}
+
 static int parse_block_error_action(const char *buf, int is_read)
 {
     if (!strcmp(buf, "ignore")) {
@@ -453,6 +466,7 @@ DriveInfo *drive_init(QemuOpts *opts, int default_to_scsi)
     dinfo->bus = bus_id;
     dinfo->unit = unit_id;
     dinfo->opts = opts;
+    dinfo->refcount = 1;
     if (serial)
         strncpy(dinfo->serial, serial, sizeof(dinfo->serial) - 1);
     QTAILQ_INSERT_TAIL(&drives, dinfo, next);
diff --git a/blockdev.h b/blockdev.h
index 84e462ab3f..2c9e7804c9 100644
--- a/blockdev.h
+++ b/blockdev.h
@@ -36,13 +36,15 @@ struct DriveInfo {
     QemuOpts *opts;
     char serial[BLOCK_SERIAL_STRLEN + 1];
     QTAILQ_ENTRY(DriveInfo) next;
+    int refcount;
 };
 
 DriveInfo *drive_get(BlockInterfaceType type, int bus, int unit);
 DriveInfo *drive_get_by_index(BlockInterfaceType type, int index);
 int drive_get_max_bus(BlockInterfaceType type);
 DriveInfo *drive_get_next(BlockInterfaceType type);
-void drive_uninit(DriveInfo *dinfo);
+void drive_get_ref(DriveInfo *dinfo);
+void drive_put_ref(DriveInfo *dinfo);
 DriveInfo *drive_get_by_blockdev(BlockDriverState *bs);
 
 QemuOpts *drive_def(const char *optstr);
diff --git a/hw/pci-hotplug.c b/hw/pci-hotplug.c
index b6dcbda0ce..478fe9b836 100644
--- a/hw/pci-hotplug.c
+++ b/hw/pci-hotplug.c
@@ -147,7 +147,7 @@ void drive_hot_add(Monitor *mon, const QDict *qdict)
 
 err:
     if (dinfo)
-        drive_uninit(dinfo);
+        drive_put_ref(dinfo);
     return;
 }