Re: [ANNOUNCEMENT PATCH COW] proof of concept impementation of cowlinks

From: Jörn Engel
Date: Tue May 11 2004 - 10:59:41 EST

On Tue, 11 May 2004 10:40:49 -0500, Steve French wrote:
> It would not be helpful to take a userspace request to perform a file
> (or directory) copy operation and break it into open/sendfile/close by
> passing file handles to the network filesystem and have this work for
> SMB/CIFS - there is no equivalent network protocol operation. It also
> makes the operation much, much harder to make atomic (since two systems
> are involved) and makes error handling and recovery for network
> filesystems much harder since inconsistent client and server state have
> to be considered if the copy operation is broken into pieces on the
> clien (it is also slower - a single copy operation on the network is the
> absolute optimal case - minimizes the expensive network latency - the
> roundtrip delay - open/sendfile/close sends at a minimum three times as
> many but likely four with an extra lookup or two)
> Currently copy file (or copy directory for that matter) as both speced
> (and is implemented in various servers) in the SMB/CIFS network
> filesystem protocol takes in effect four parameters (there is no handle
> based file copy):
> a source pathname, and source export (actually SMB tree identifier for
> a share, but in effect the same thing)
> a target pathname, and target export (actually SMB tree identifier for a
> share, but in effect the same thing)
> And the shares (exports) referenced have to be on the same server

Or in short, copyfile makes sense for smbfs/cifs. The question
whether my hack can be cleaned up enough to get past Al Viro is still
open, though. :)


Homo Sapiens is a goal, not a description.
-- unknown
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