+/*
+ * While truncating the inode pages during eviction, we get the VFS calling
+ * btrfs_invalidatepage() against each page of the inode. This is slow because
+ * the calls to btrfs_invalidatepage() result in a huge amount of calls to
+ * lock_extent_bits() and clear_extent_bit(), which keep merging and splitting
+ * extent_state structures over and over, wasting lots of time.
+ *
+ * Therefore if the inode is being evicted, let btrfs_invalidatepage() skip all
+ * those expensive operations on a per page basis and do only the ordered io
+ * finishing, while we release here the extent_map and extent_state structures,
+ * without the excessive merging and splitting.
+ */
+static void evict_inode_truncate_pages(struct inode *inode)
+{
+ struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
+ struct extent_map_tree *map_tree = &BTRFS_I(inode)->extent_tree;
+ struct rb_node *node;
+
+ ASSERT(inode->i_state & I_FREEING);
+ truncate_inode_pages(&inode->i_data, 0);
+
+ write_lock(&map_tree->lock);
+ while (!RB_EMPTY_ROOT(&map_tree->map)) {
+ struct extent_map *em;
+
+ node = rb_first(&map_tree->map);
+ em = rb_entry(node, struct extent_map, rb_node);
+ clear_bit(EXTENT_FLAG_PINNED, &em->flags);
+ clear_bit(EXTENT_FLAG_LOGGING, &em->flags);
+ remove_extent_mapping(map_tree, em);
+ free_extent_map(em);
+ }
+ write_unlock(&map_tree->lock);
+
+ spin_lock(&io_tree->lock);
+ while (!RB_EMPTY_ROOT(&io_tree->state)) {
+ struct extent_state *state;
+ struct extent_state *cached_state = NULL;
+
+ node = rb_first(&io_tree->state);
+ state = rb_entry(node, struct extent_state, rb_node);
+ atomic_inc(&state->refs);
+ spin_unlock(&io_tree->lock);
+
+ lock_extent_bits(io_tree, state->start, state->end,
+ 0, &cached_state);
+ clear_extent_bit(io_tree, state->start, state->end,
+ EXTENT_LOCKED | EXTENT_DIRTY |
+ EXTENT_DELALLOC | EXTENT_DO_ACCOUNTING |
+ EXTENT_DEFRAG, 1, 1,
+ &cached_state, GFP_NOFS);
+ free_extent_state(state);
+
+ spin_lock(&io_tree->lock);
+ }
+ spin_unlock(&io_tree->lock);
+}
+