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    SubjectRe: Networked filesystems vs backing_dev_info
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    On Sat, 2007-10-27 at 11:22 -0400, Jan Harkes wrote:
    > On Sat, Oct 27, 2007 at 11:34:26AM +0200, Peter Zijlstra wrote:
    > > I had me a little look at bdi usage in networked filesystems.
    > >
    > > NFS, CIFS, (smbfs), AFS, CODA and NCP
    > >
    > > And of those, NFS is the only one that I could find that creates
    > > backing_dev_info structures. The rest seems to fall back to
    > > default_backing_dev_info.
    >
    > While a file is opened in Coda we associate the open file handle with a
    > local cache file. All read and write operations are redirected to this
    > local file and we even redirect inode->i_mapping. Actual reads and
    > writes are completely handled by the underlying file system. We send the
    > new file contents back to the servers only after all local references
    > have been released (last-close semantics).
    >
    > As a result, there is no need for backing_dev_info structures in Coda,
    > if any congestion control is needed it will be handled by the underlying
    > file system where our locally cached copies are stored.

    Ok, that works. Thanks for this explanation!

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