NFS/pNFS: Fix pnfs_layout_mark_request_commit() invalid layout segment handling

{

	struct list_head *list;

	struct pnfs_commit_array *array;

	struct pnfs_commit_bucket *buckets;

	struct pnfs_commit_bucket *bucket;

	mutex_lock(&NFS_I(cinfo->inode)->commit_mutex);

	array = pnfs_lookup_commit_array(cinfo->ds, lseg);

	if (!array)

		goto out_resched;

	buckets = array->buckets;

	list = &buckets[ds_commit_idx].written;

	if (list_empty(list)) {

		if (!pnfs_is_valid_lseg(lseg))

	if (!array || !pnfs_is_valid_lseg(lseg))

		goto out_resched;

	bucket = &array->buckets[ds_commit_idx];

	list = &bucket->written;

	/* Non-empty buckets hold a reference on the lseg.  That ref

	 * is normally transferred to the COMMIT call and released

	 * there.  It could also be released if the last req is pulled

	 * off due to a rewrite, in which case it will be done in

	 * pnfs_common_clear_request_commit

	 */

		if (!buckets[ds_commit_idx].lseg)

			buckets[ds_commit_idx].lseg = pnfs_get_lseg(lseg);

	}

	if (!bucket->lseg)

		bucket->lseg = pnfs_get_lseg(lseg);

	set_bit(PG_COMMIT_TO_DS, &req->wb_flags);

	cinfo->ds->nwritten++;