savevm.c keeps a pointer to the snapshot block device. If you manage
to get that device deleted, the pointer dangles, and the next snapshot
operation will crash & burn. Unplugging a guest device that uses it
does the trick:
$ MALLOC_PERTURB_=234 qemu-system-x86_64 [...]
QEMU 0.12.50 monitor - type 'help' for more information
(qemu) info snapshots
No available block device supports snapshots
(qemu) drive_add auto if=none,file=tmp.qcow2
OK
(qemu) device_add usb-storage,id=foo,drive=none1
(qemu) info snapshots
Snapshot devices: none1
Snapshot list (from none1):
ID TAG VM SIZE DATE VM CLOCK
(qemu) device_del foo
(qemu) info snapshots
Snapshot devices:
Segmentation fault (core dumped)
Move management of that pointer to block.c, and zap it when the device
it points to goes away.
Signed-off-by: Markus Armbruster <arm...@redhat.com>
---
block.c | 25 +++++++++++++++++++++++++
block.h | 1 +
savevm.c | 31 ++++---------------------------
3 files changed, 30 insertions(+), 27 deletions(-)
diff --git a/block.c b/block.c
index 5e0ffa0..34055e0 100644
--- a/block.c
+++ b/block.c
@@ -63,6 +63,9 @@ static QTAILQ_HEAD(, BlockDriverState) bdrv_states =
static QLIST_HEAD(, BlockDriver) bdrv_drivers =
QLIST_HEAD_INITIALIZER(bdrv_drivers);
+/* The device to use for VM snapshots */
+static BlockDriverState *bs_snapshots;
+
/* If non-zero, use only whitelisted block drivers */
static int use_bdrv_whitelist;
@@ -660,6 +663,9 @@ void bdrv_close_all(void)
void bdrv_delete(BlockDriverState *bs)
{
assert(!bs->peer);
+ if (bs == bs_snapshots) {
+ bs_snapshots = NULL;
+ }
/* remove from list, if necessary */
if (bs->device_name[0] != '\0') {
@@ -1772,6 +1778,25 @@ int bdrv_can_snapshot(BlockDriverState *bs)
return 1;
}
+BlockDriverState *bdrv_snapshots(void)
+{
+ BlockDriverState *bs;
+
+ if (bs_snapshots)
+ return bs_snapshots;
+
+ bs = NULL;
+ while ((bs = bdrv_next(bs))) {
+ if (bdrv_can_snapshot(bs)) {
+ goto ok;
+ }
+ }
+ return NULL;
+ ok:
+ bs_snapshots = bs;
+ return bs;
+}
+
int bdrv_snapshot_create(BlockDriverState *bs,
QEMUSnapshotInfo *sn_info)
{
diff --git a/block.h b/block.h
index 88ac06e..012c2a1 100644
--- a/block.h
+++ b/block.h
@@ -193,6 +193,7 @@ const char *bdrv_get_encrypted_filename(BlockDriverState
*bs);
void bdrv_get_backing_filename(BlockDriverState *bs,
char *filename, int filename_size);
int bdrv_can_snapshot(BlockDriverState *bs);
+BlockDriverState *bdrv_snapshots(void);
int bdrv_snapshot_create(BlockDriverState *bs,
QEMUSnapshotInfo *sn_info);
int bdrv_snapshot_goto(BlockDriverState *bs,
diff --git a/savevm.c b/savevm.c
index 20354a8..f1f450e 100644
--- a/savevm.c
+++ b/savevm.c
@@ -83,9 +83,6 @@
#include "qemu_socket.h"
#include "qemu-queue.h"
-/* point to the block driver where the snapshots are managed */
-static BlockDriverState *bs_snapshots;
-
#define SELF_ANNOUNCE_ROUNDS 5
#ifndef ETH_P_RARP
@@ -1575,26 +1572,6 @@ out:
return ret;
}
-static BlockDriverState *get_bs_snapshots(void)
-{
- BlockDriverState *bs;
-
- if (bs_snapshots)
- return bs_snapshots;
- /* FIXME what if bs_snapshots gets hot-unplugged? */
-
- bs = NULL;
- while ((bs = bdrv_next(bs))) {
- if (bdrv_can_snapshot(bs)) {
- goto ok;
- }
- }
- return NULL;
- ok:
- bs_snapshots = bs;
- return bs;
-}
-
static int bdrv_snapshot_find(BlockDriverState *bs, QEMUSnapshotInfo *sn_info,
const char *name)
{
@@ -1674,7 +1651,7 @@ void do_savevm(Monitor *mon, const QDict *qdict)
}
}
- bs = get_bs_snapshots();
+ bs = bdrv_snapshots();
if (!bs) {
monitor_printf(mon, "No block device can accept snapshots\n");
return;
@@ -1769,7 +1746,7 @@ int load_vmstate(const char *name)
}
}
- bs = get_bs_snapshots();
+ bs = bdrv_snapshots();
if (!bs) {
error_report("No block device supports snapshots");
return -EINVAL;
@@ -1833,7 +1810,7 @@ void do_delvm(Monitor *mon, const QDict *qdict)
int ret;
const char *name = qdict_get_str(qdict, "name");
- bs = get_bs_snapshots();
+ bs = bdrv_snapshots();
if (!bs) {
monitor_printf(mon, "No block device supports snapshots\n");
return;
@@ -1863,7 +1840,7 @@ void do_info_snapshots(Monitor *mon)
int nb_sns, i;
char buf[256];
- bs = get_bs_snapshots();
+ bs = bdrv_snapshots();
if (!bs) {
monitor_printf(mon, "No available block device supports snapshots\n");
return;
--
1.6.6.1
