Btrfs: Limit btree writeback to prevent seeks
Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c
index 55f272c..b6a4974 100644
--- a/fs/btrfs/extent_map.c
+++ b/fs/btrfs/extent_map.c
@@ -1106,6 +1106,45 @@
return found;
}
+u64 count_range_bits(struct extent_map_tree *tree,
+ u64 *start, u64 max_bytes, unsigned long bits)
+{
+ struct rb_node *node;
+ struct extent_state *state;
+ u64 cur_start = *start;
+ u64 total_bytes = 0;
+ int found = 0;
+
+ write_lock_irq(&tree->lock);
+ /*
+ * this search will find all the extents that end after
+ * our range starts.
+ */
+ node = tree_search(&tree->state, cur_start);
+ if (!node || IS_ERR(node)) {
+ goto out;
+ }
+
+ while(1) {
+ state = rb_entry(node, struct extent_state, rb_node);
+ if ((state->state & bits)) {
+ total_bytes += state->end - state->start + 1;
+ if (total_bytes >= max_bytes)
+ break;
+ if (!found) {
+ *start = state->start;
+ found = 1;
+ }
+ }
+ node = rb_next(node);
+ if (!node)
+ break;
+ }
+out:
+ write_unlock_irq(&tree->lock);
+ return total_bytes;
+}
+
/*
* helper function to lock both pages and extents in the tree.
* pages must be locked first.