+STATIC void
+xfs_buf_lru_add(
+ struct xfs_buf *bp)
+{
+ struct xfs_buftarg *btp = bp->b_target;
+
+ spin_lock(&btp->bt_lru_lock);
+ if (list_empty(&bp->b_lru)) {
+ atomic_inc(&bp->b_hold);
+ list_add_tail(&bp->b_lru, &btp->bt_lru);
+ btp->bt_lru_nr++;
+ }
+ spin_unlock(&btp->bt_lru_lock);
+}
+
+/*
+ * xfs_buf_lru_del - remove a buffer from the LRU
+ *
+ * The unlocked check is safe here because it only occurs when there are not
+ * b_lru_ref counts left on the inode under the pag->pag_buf_lock. it is there
+ * to optimise the shrinker removing the buffer from the LRU and calling
+ * xfs_buf_free(). i.e. it removes an unneccessary round trip on the
+ * bt_lru_lock.
+ */
+STATIC void
+xfs_buf_lru_del(
+ struct xfs_buf *bp)
+{
+ struct xfs_buftarg *btp = bp->b_target;
+
+ if (list_empty(&bp->b_lru))
+ return;
+
+ spin_lock(&btp->bt_lru_lock);
+ if (!list_empty(&bp->b_lru)) {
+ list_del_init(&bp->b_lru);
+ btp->bt_lru_nr--;
+ }
+ spin_unlock(&btp->bt_lru_lock);
+}
+
+/*
+ * When we mark a buffer stale, we remove the buffer from the LRU and clear the
+ * b_lru_ref count so that the buffer is freed immediately when the buffer
+ * reference count falls to zero. If the buffer is already on the LRU, we need
+ * to remove the reference that LRU holds on the buffer.
+ *
+ * This prevents build-up of stale buffers on the LRU.
+ */
+void
+xfs_buf_stale(
+ struct xfs_buf *bp)
+{
+ bp->b_flags |= XBF_STALE;
+ atomic_set(&(bp)->b_lru_ref, 0);
+ if (!list_empty(&bp->b_lru)) {
+ struct xfs_buftarg *btp = bp->b_target;
+
+ spin_lock(&btp->bt_lru_lock);
+ if (!list_empty(&bp->b_lru)) {
+ list_del_init(&bp->b_lru);
+ btp->bt_lru_nr--;
+ atomic_dec(&bp->b_hold);
+ }
+ spin_unlock(&btp->bt_lru_lock);
+ }
+ ASSERT(atomic_read(&bp->b_hold) >= 1);
+}