[Xen-devel] xenstored misaccounting resource limits

[John Levon <levon@xxxxxxxxxxxxxxxxx>]

Currently xenstored does not account domain->nbentry when a transaction
is aborted (either intentionally or via EAGAIN). We hit this case when
adding a lot of disks to a domU: the limit is reached much earlier than
expected, as a number of clashing transactions cause incorrect inflation
of the value of ->nbentry.

There's been a little discussion internally on the nicest way to fix
this. My current suggestion is along the lines of:

domain_entry_inc()

       d = domain to inc as before

       if (transaction)
               transaction->domain_nbcount[d]++
       else
               d->nbcount++

(same for _dec)

then in transaction end:

       for d in transaction->domains
               d->nbcount += transaction->domain_nbcount[d]


But I thought it wise to ask if somebody has a different suggestion, or
preference, before we cook up a patch.

cheers
john

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