Re: [Xen-devel] [PATCH] oxenstored: Quota.merge: don't assume domain already exists

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Jonathan Davies writes ("[PATCH] oxenstored: Quota.merge: don't assume domain 
already exists"):
> In Quota.merge, we merge two quota hashtables, orig_quota and mod_quota, 
> putting
> the results into dest_quota. These hashtables map domids to the number of
> entries currently owned by that domain.
> 
> When mod_quota contains an entry for a domid that was not present in 
> orig_quota
> (or dest_quota), the call to get_entry caused Quota.merge to raise a Not_found
> exception. This propagates back to the client as an ENOENT error, which is not
> an appropriate return value from some operations, such as transaction_end.
> 
> This situation can arise when a transaction that introduces a domain (hence
> calling Quota.add_entry) needs to be coalesced due to concurrent xenstore
> activity.
> 
> This patch handles the merge in the case where mod_quota contains an entry not
> present in orig_quota (or in dest_quota) by treating that hashtable as having
> existing value 0.
> 
> Signed-off-by: Jonathan Davies <jonathan.davies@xxxxxxxxxx>

The ocaml looks vaguely plausible.  I speak enough ocaml to see that
this looks (out of context and with my half-remembered knowledge of
oxenstored innards) like it does what you say.

Acked-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>

Thanks,
Ian.

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