NFSv4.1: Ensure that the layout sequence id stays 'close' to the current

pnfs_set_layout_stateid(struct pnfs_layout_hdr *lo, const nfs4_stateid *new,

			bool update_barrier)

{

	u32 oldseq, newseq;

	u32 oldseq, newseq, new_barrier;

	int empty = list_empty(&lo->plh_segs);

	oldseq = be32_to_cpu(lo->plh_stateid.seqid);

	newseq = be32_to_cpu(new->seqid);

	if (list_empty(&lo->plh_segs) || pnfs_seqid_is_newer(newseq, oldseq)) {

	if (empty || pnfs_seqid_is_newer(newseq, oldseq)) {

		nfs4_stateid_copy(&lo->plh_stateid, new);

		if (update_barrier) {

			u32 new_barrier = be32_to_cpu(new->seqid);

			if (pnfs_seqid_is_newer(new_barrier, lo->plh_barrier))

				lo->plh_barrier = new_barrier;

			new_barrier = be32_to_cpu(new->seqid);

		} else {

			/* Because of wraparound, we want to keep the barrier

			 * "close" to the current seqids.  It needs to be

			 * within 2**31 to count as "behind", so if it

			 * gets too near that limit, give us a litle leeway

			 * and bring it to within 2**30.

			 * NOTE - and yes, this is all unsigned arithmetic.

			 * "close" to the current seqids.

			 */

			if (unlikely((newseq - lo->plh_barrier) > (3 << 29)))

				lo->plh_barrier = newseq - (1 << 30);

			new_barrier = newseq - atomic_read(&lo->plh_outstanding);

		}

		if (empty || pnfs_seqid_is_newer(new_barrier, lo->plh_barrier))

			lo->plh_barrier = new_barrier;

	}

}