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Date: Fri, 12 Dec 2008 15:24:35 +0100
From: Andrea Arcangeli <aarcange@redhat.com>
Subject: Re: [Qemu-devel] [RFC] Replace posix-aio with custom thread pool
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To: Anthony Liguori <anthony@codemonkey.ws>
Cc: Gerd Hoffmann <kraxel@redhat.com>, kvm-devel <kvm@vger.kernel.org>, qemu-devel@nongnu.org

On Wed, Dec 10, 2008 at 08:08:10PM +0100, Andrea Arcangeli wrote:
> On Wed, Dec 10, 2008 at 12:50:17PM -0600, Anthony Liguori wrote:
> > But opening twice means that you lose coherency with NFS.
> 
> Not sure why. They're not running from different nfs clients. If this

I just got confirmation from Trond that from nfs point of view,
opening the file multiple times or duping it, is the same as I
expected (all it matters is that the inode is the same so the
pagecache radix tree is the same etc..). So opening the file each time
a thread starts, would provide a local f_pos and it would work fine on
older/current kernels too. In theory other nfs clients should also
behave. Not sure what's best, if to hack around the bdrv api and open
the file multiple times or wait for preadv/pwritev.