Messages in this thread | | | Subject | Re: Networked filesystems vs backing_dev_info | From | Peter Zijlstra <> | Date | Sat, 27 Oct 2007 17:32:16 +0200 |
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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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