Re: [Xen-devel] question about xenstore-chmod MAX_PERMS

[Chunyan Liu <cyliu@xxxxxxxx>]

2012/11/15 Ian Campbell <Ian.Campbell@xxxxxxxxxx>

On Thu, 2012-11-15 at 01:51 +0000, Chunyan Liu wrote:
>
> Â Â Â Â Â Â Â Â I can't see anything obvious in the underlying library
> Â Â Â Â Â Â Â Â which would
> Â Â Â Â Â Â Â Â prevent it handling essentially arbitrary length lists
> Â Â Â Â Â Â Â Â of perms. If you
> Â Â Â Â Â Â Â Â want to change the client to increase the number
> Â Â Â Â Â Â Â Â supported I think you
> Â Â Â Â Â Â Â Â should make it likewise handle arbitrary numbers
> Â Â Â Â Â Â Â Â rather than just
> Â Â Â Â Â Â Â Â increasing MAX_PERMS.
>
> In addition: there is a check for msg.len <= ÂXENSTORE_PAYLOAD_MAX
> (which is 4096).
> For chmod, the msg.len = path len + mode len. In current environments,
> there won't be so many perms that could exceed the value. But it IS a
> limitation.

Do you know what it works out as?

If atomicity matters you could do it as batches within a transaction,

Â

Yeah. If exceeding 4096 happens, batches within a transaction is the way out. Same to other commands.
But this is purely from coding's point, in current environments it's almost impossible to happen :-)
Â

otherwise simple batching would do?

Ian.

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