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block: add helper function to determine if a BDS is in a chain

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This is a small helper function, to determine if 'base' is in the
chain of BlockDriverState 'top'.  It returns true if it is in the chain,
and false otherwise.

If either argument is NULL, it will also return false.

Reviewed-by: Benoit Canet <benoit@irqsave.net>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Jeff Cody <jcody@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Jeff Cody 2014-06-25 15:40:09 -04:00 committed by Stefan Hajnoczi
parent fa40e65622
commit 5a6684d2b9
2 changed files with 12 additions and 0 deletions
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11
block.c
View File

@ -3774,6 +3774,17 @@ BlockDriverState *bdrv_lookup_bs(const char *device,
return NULL;
}
/* If 'base' is in the same chain as 'top', return true. Otherwise,
* return false. If either argument is NULL, return false. */
bool bdrv_chain_contains(BlockDriverState *top, BlockDriverState *base)
{
while (top && top != base) {
top = top->backing_hd;
}
return top != NULL;
}
BlockDriverState *bdrv_next(BlockDriverState *bs)
{
if (!bs) {

1
include/block/block.h
View File

@ -403,6 +403,7 @@ BlockDeviceInfoList *bdrv_named_nodes_list(void);
BlockDriverState *bdrv_lookup_bs(const char *device,
const char *node_name,
Error **errp);
bool bdrv_chain_contains(BlockDriverState *top, BlockDriverState *base);
BlockDriverState *bdrv_next(BlockDriverState *bs);
void bdrv_iterate(void (*it)(void *opaque, BlockDriverState *bs),
void *opaque);