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block: drop bs_snapshots global variable

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The bs_snapshots global variable points to the BlockDriverState which
will be used to save vmstate.  This is really a savevm.c concept but was
moved into block.c:bdrv_snapshots() when it became clear that hotplug
could result in a dangling pointer.

While auditing the block layer's global state I came upon bs_snapshots
and realized that a variable is not necessary here.  Simply find the
first BlockDriverState capable of internal snapshots each time this is
needed.

The behavior of bdrv_snapshots() is preserved across hotplug because new
drives are always appended to the bdrv_states list.  This means that
calling the new find_vmstate_bs() function is idempotent - it returns
the same BlockDriverState unless it was hot-unplugged.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Wenchao Xia <xiawenc@linux.vnet.ibm.com>
Signed-off-by: Wenchao Xia <xiawenc@linux.vnet.ibm.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2013-05-25 11:09:42 +08:00 committed by Kevin Wolf
parent 2499a096a2
commit 29d782710f
3 changed files with 15 additions and 33 deletions
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28
block.c
View File

@ -99,9 +99,6 @@ 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;
@ -1368,9 +1365,6 @@ void bdrv_close(BlockDriverState *bs)
notifier_list_notify(&bs->close_notifiers, bs);
if (bs->drv) {
if (bs == bs_snapshots) {
bs_snapshots = NULL;
}
if (bs->backing_hd) {
bdrv_delete(bs->backing_hd);
bs->backing_hd = NULL;
@ -1602,7 +1596,6 @@ void bdrv_delete(BlockDriverState *bs)
bdrv_close(bs);
assert(bs != bs_snapshots);
g_free(bs);
}
@ -1646,9 +1639,6 @@ void bdrv_set_dev_ops(BlockDriverState *bs, const BlockDevOps *ops,
{
bs->dev_ops = ops;
bs->dev_opaque = opaque;
if (bdrv_dev_has_removable_media(bs) && bs == bs_snapshots) {
bs_snapshots = NULL;
}
}
void bdrv_emit_qmp_error_event(const BlockDriverState *bdrv,
@ -3392,24 +3382,6 @@ int bdrv_is_snapshot(BlockDriverState *bs)
return !!(bs->open_flags & BDRV_O_SNAPSHOT);
}
BlockDriverState *bdrv_snapshots(void)
{
BlockDriverState *bs;
if (bs_snapshots) {
return bs_snapshots;
}
bs = NULL;
while ((bs = bdrv_next(bs))) {
if (bdrv_can_snapshot(bs)) {
bs_snapshots = bs;
return bs;
}
}
return NULL;
}
int bdrv_snapshot_create(BlockDriverState *bs,
QEMUSnapshotInfo *sn_info)
{

1
include/block/block.h
View File

@ -333,7 +333,6 @@ BlockInfo *bdrv_query_info(BlockDriverState *s);
BlockStats *bdrv_query_stats(const BlockDriverState *bs);
int bdrv_can_snapshot(BlockDriverState *bs);
int bdrv_is_snapshot(BlockDriverState *bs);
BlockDriverState *bdrv_snapshots(void);
int bdrv_snapshot_create(BlockDriverState *bs,
QEMUSnapshotInfo *sn_info);
int bdrv_snapshot_goto(BlockDriverState *bs,

19
savevm.c
View File

@ -2262,6 +2262,17 @@ out:
return ret;
}
static BlockDriverState *find_vmstate_bs(void)
{
BlockDriverState *bs = NULL;
while ((bs = bdrv_next(bs))) {
if (bdrv_can_snapshot(bs)) {
return bs;
}
}
return NULL;
}
static int bdrv_snapshot_find(BlockDriverState *bs, QEMUSnapshotInfo *sn_info,
const char *name)
{
@ -2338,7 +2349,7 @@ void do_savevm(Monitor *mon, const QDict *qdict)
}
}
bs = bdrv_snapshots();
bs = find_vmstate_bs();
if (!bs) {
monitor_printf(mon, "No block device can accept snapshots\n");
return;
@ -2440,7 +2451,7 @@ int load_vmstate(const char *name)
QEMUFile *f;
int ret;
bs_vm_state = bdrv_snapshots();
bs_vm_state = find_vmstate_bs();
if (!bs_vm_state) {
error_report("No block device supports snapshots");
return -ENOTSUP;
@ -2519,7 +2530,7 @@ void do_delvm(Monitor *mon, const QDict *qdict)
int ret;
const char *name = qdict_get_str(qdict, "name");
bs = bdrv_snapshots();
bs = find_vmstate_bs();
if (!bs) {
monitor_printf(mon, "No block device supports snapshots\n");
return;
@ -2551,7 +2562,7 @@ void do_info_snapshots(Monitor *mon, const QDict *qdict)
int *available_snapshots;
char buf[256];
bs = bdrv_snapshots();
bs = find_vmstate_bs();
if (!bs) {
monitor_printf(mon, "No available block device supports snapshots\n");
return;