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block: Implement bdrv_append() without bdrv_swap()

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Remember all parent nodes and just change the pointers there instead of
swapping the contents of the BlockDriverState.

Handling of snapshot=on must be moved further down in bdrv_open()
because *pbs (which is the bs pointer in the BlockBackend) must already
be set before bdrv_append() is called. Otherwise bdrv_append() changes
the BB's pointer to the temporary snapshot, but bdrv_open() overwrites
it with the read-only original image.

We also need to be careful to update callers as the interface changes
(becomes less insane): Previously, the meaning of the two parameters was
inverted when bdrv_append() returns. Now any BDS pointers keep pointing
to the same node.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Kevin Wolf 2015-06-18 14:09:57 +02:00
parent d42a8a935b
commit dd62f1ca43
2 changed files with 87 additions and 31 deletions
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2
blockdev.c
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@ -1546,7 +1546,7 @@ static void external_snapshot_commit(BlkTransactionState *common)
/* We don't need (or want) to use the transactional
* bdrv_reopen_multiple() across all the entries at once, because we
* don't want to abort all of them if one of them fails the reopen */
bdrv_reopen(state->new_bs, state->new_bs->open_flags & ~BDRV_O_RDWR,
bdrv_reopen(state->old_bs, state->old_bs->open_flags & ~BDRV_O_RDWR,
NULL);
aio_context_release(state->aio_context);