netdev - Re: [PATCH 3/3] AFS: Implement basic file write support

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Message-ID: <27482.1178790992@warthog.cambridge.redhat.com>
Date:	Thu, 10 May 2007 10:56:32 +0100
From:	David Howells <dhowells@...hat.com>
To:	Nick Piggin <nickpiggin@...oo.com.au>
Cc:	David Howells <dhowells@...hat.com>, akpm@...l.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 3/3] AFS: Implement basic file write support

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

> Why do you call SetPageUptodate when the page is not up to date?
> That leaks uninitialised data, AFAIKS.

It only seems that way.  If afs_prepare_write() is called, but doesn't return
an error, then afs_commit_write() will be called, and it seems that the copy
in of the data will be guaranteed not to fail by the caller.

Furthermore, afs_prepare_page() will have filled in the missing bits.

And whilst all that is going on, the page lock will be help by the caller, so
that no-one else can access the partially complete page.

I suppose I could call SetPageUptodate() in afs_commit_write() instead.

David
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