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

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Message-ID: <464D0F9D.9070303@yahoo.com.au>
Date:	Fri, 18 May 2007 12:29:49 +1000
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	David Howells <dhowells@...hat.com>
CC:	akpm@...l.org, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH] AFS: Implement shared-writable mmap [try #2]

David Howells wrote:
> 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?

Truncate as it stands still needs to be given unlocked pages. So we would
either have to create a new API, or I think preferably it would be nice if
you could see if you can first solve it with a private lock?

-- 
SUSE Labs, Novell Inc.
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