From fd6002e9b8a93220d5f53b93d9624caf73cdc8a2 Mon Sep 17 00:00:00 2001
From: Fred Isaman <iisaman@netapp.com>
Date: Thu, 6 Jan 2011 11:36:22 +0000
Subject: [PATCH] pnfs: change layout state seqlock to a spinlock

This prepares for future changes, where the layout state needs
to change atomically with several other variables.  In particular,
it will need to know if lo->segs is empty, as we test that instead
of manipulating the NFS_LAYOUT_STATEID_SET bit.  Moreover, the
layoutstateid is not really a read-mostly structure, as it is
written almost as often as it is read.

The behavior of pnfs_get_layout_stateid is also slightly changed, so that
it no longer changes the stateid.  Its name is changed to +pnfs_choose_layoutget_stateid.

Signed-off-by: Fred Isaman <iisaman@netapp.com>
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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