NFSv4.1 mark layout when already returned

When the file layout driver is fencing a DS, _pnfs_return_layout can be
called mulitple times per inode due to in-flight i/o referencing lsegs on it's
plh_segs list.

Remember that LAYOUTRETURN has been called, and do not call it again.
Allow LAYOUTRETURNs after a subsequent LAYOUTGET.

Signed-off-by: Andy Adamson <andros@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/pnfs.h b/fs/nfs/pnfs.h
index 592beb0..2c6c805 100644
--- a/fs/nfs/pnfs.h
+++ b/fs/nfs/pnfs.h
@@ -64,6 +64,7 @@
 	NFS_LAYOUT_ROC,			/* some lseg had roc bit set */
 	NFS_LAYOUT_DESTROYED,		/* no new use of layout allowed */
 	NFS_LAYOUT_INVALID,		/* layout is being destroyed */
+	NFS_LAYOUT_RETURNED,		/* layout has already been returned */
 };
 
 enum layoutdriver_policy_flags {
@@ -255,6 +256,24 @@
 bool nfs4_put_deviceid_node(struct nfs4_deviceid_node *);
 void nfs4_deviceid_purge_client(const struct nfs_client *);
 
+static inline void
+pnfs_mark_layout_returned(struct pnfs_layout_hdr *lo)
+{
+	set_bit(NFS_LAYOUT_RETURNED, &lo->plh_flags);
+}
+
+static inline void
+pnfs_clear_layout_returned(struct pnfs_layout_hdr *lo)
+{
+	clear_bit(NFS_LAYOUT_RETURNED, &lo->plh_flags);
+}
+
+static inline bool
+pnfs_test_layout_returned(struct pnfs_layout_hdr *lo)
+{
+	return test_bit(NFS_LAYOUT_RETURNED, &lo->plh_flags);
+}
+
 static inline int lo_fail_bit(u32 iomode)
 {
 	return iomode == IOMODE_RW ?