When we are setting a new layout, fully initialize the structure:
 - zero it out
 - always set preferred_osd to -1
Signed-off-by: NSage Weil <sage@inktank.com>
Reviewed-by: NAlex Elder <elder@inktank.com>

...after some prodding by Christoph.
Signed-off-by: NSage Weil <sage@newdream.net>

This allows us to force IO through the sync path which you normally only
get when multiple clients are reading/writing to the same file or by
mounting with -o sync.  Among other things, this lets test programs verify
correctness with a single mount.
Reviewed-by: NYehuda Sadeh <yehuda@hq.newdream.net>
Signed-off-by: NSage Weil <sage@newdream.net>

The ioctl magic was inadvertently changed in 571dba52.
Signed-off-by: NSage Weil <sage@newdream.net>

Signed-off-by: NSage Weil <sage@newdream.net>

Allow an application to mark a file descriptor for lazy file consistency
semantics, allowing buffered reads and writes when multiple clients are
accessing the same file.
Signed-off-by: NSage Weil <sage@newdream.net>

There is certainly no reason not to report this.

The only real downside to allowing the user to set it is that you don't
get default values by zeroing the layout struct (the default is -1).
Signed-off-by: NSage Weil <sage@newdream.net>

A few Ceph ioctls for getting and setting file layout (striping)
parameters, and learning the identity and network address of the OSD a
given region of a file is stored on.
Signed-off-by: NSage Weil <sage@newdream.net>