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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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1
include/block/block.h
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@ -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,