linux-kernel - Re: [PATCH] AFS: Implement shared-writable mmap [try #2]

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Date:	Thu, 17 May 2007 13:30:01 +0100
From:	David Howells <dhowells@...hat.com>
To:	Nick Piggin <nickpiggin@...oo.com.au>
Cc:	akpm@...l.org, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH] AFS: Implement shared-writable mmap [try #2]

Nick Piggin <nickpiggin@...oo.com.au> wrote:

> No, you shouldn't. We could theoretically introduce a new API for this,
> but I think it would be preferable if you can fix the race in the fs.

Actually, I might be able to do better.

When making a StoreData call to the AFS server, I send all the parameters
first, and at that point, the server will abort it, I think, if permission is
not available, and won't wait for the payload to be delivered.

So if I tell AF_RXRPC to send the parameter data with an explicit ACK request
and then wait till it's either hard-ACK'd or aborted, I should then be able to
deal with the permissions failure at a state where I have locked *all* the
pages to be sent.

At that point, I should be able to tell truncate to simple discard all these
locked pages.

How's that sound?

David
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