Re: [PATCH] rdma: don't make pages writeable if not requiested

From: Roland Dreier
Date: Thu Mar 21 2013 - 05:14:08 EST

On Thu, Mar 21, 2013 at 1:51 AM, Michael S. Tsirkin <mst@xxxxxxxxxx> wrote:
>> In that case, no, I don't see any reason for LOCAL_WRITE, since the
>> only RDMA operations that will access this memory are remote reads.
> What is the meaning of LOCAL_WRITE then? There are no local
> RDMA writes as far as I can see.

Umm, it means you're giving the local adapter permission to write to
that memory. So you can use it as a receive buffer or as the target
for remote data from an RDMA read operation.

> OK then what we need is a new flag saying "I really do not
> intend to write into this memory please do not break
> COW or do anything else just in case I do".

Isn't that a shared read-only mapping?

- R.
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