+ release = atomic_dec_and_lock(&bp->b_hold, &pag->pag_buf_lock);
+ spin_lock(&bp->b_lock);
+ if (!release) {
+ /*
+ * Drop the in-flight state if the buffer is already on the LRU
+ * and it holds the only reference. This is racy because we
+ * haven't acquired the pag lock, but the use of _XBF_IN_FLIGHT
+ * ensures the decrement occurs only once per-buf.
+ */
+ if ((atomic_read(&bp->b_hold) == 1) && !list_empty(&bp->b_lru))
+ xfs_buf_ioacct_dec(bp);
+ goto out_unlock;
+ }
+
+ /* the last reference has been dropped ... */
+ xfs_buf_ioacct_dec(bp);
+ if (!(bp->b_flags & XBF_STALE) && atomic_read(&bp->b_lru_ref)) {
+ /*
+ * If the buffer is added to the LRU take a new reference to the
+ * buffer for the LRU and clear the (now stale) dispose list
+ * state flag
+ */
+ if (list_lru_add(&bp->b_target->bt_lru, &bp->b_lru)) {
+ bp->b_state &= ~XFS_BSTATE_DISPOSE;
+ atomic_inc(&bp->b_hold);
+ }
+ spin_unlock(&pag->pag_buf_lock);
+ } else {
+ /*
+ * most of the time buffers will already be removed from the
+ * LRU, so optimise that case by checking for the
+ * XFS_BSTATE_DISPOSE flag indicating the last list the buffer
+ * was on was the disposal list
+ */
+ if (!(bp->b_state & XFS_BSTATE_DISPOSE)) {
+ list_lru_del(&bp->b_target->bt_lru, &bp->b_lru);
+ } else {
+ ASSERT(list_empty(&bp->b_lru));