Re: [PATCH v2 01/13] tools/xenstore: don't allow creating too many nodes in a transaction

[Juergen Gross <jgross@xxxxxxxx>]

On 20.02.23 14:49, Juergen Gross wrote:
> Assume node quota is 1000, and at start of the transaction the guest is owning
> 999 nodes. In the transaction the guest is deleting 10 nodes, then dom0 is
> creating 5 additional nodes owned by the guest. The central node counter is now
> 1004 (over quota), while the in-transaction count is 994. In the transaction the
> guest can now happily create a new node (#995) with my patch, but will fail to
> do so without (it sees the 1004 due to the transaction count being ignored).
It is even worse, so I'd like to suggest the following commit message:

  tools/xenstore: take transaction internal nodes into account for quota

  The accounting for the number of nodes of a domain in an active
  transaction is not working correctly, as it is checking the node quota
  only against the number of nodes outside the transaction.

  This can result in the transaction finally failing, as node quota is
  checked at the end of the transaction again.

  On the other hand even in a transaction deleting many nodes, new nodes
  might not be creatable, in case the node quota was already reached at
  the start of the transaction.


Juergen

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