Btrfs: add and improve comments
This improves the comments at the top of many functions. It didn't
dive into the guts of functions because I was trying to
avoid merging problems with the new allocator and back reference work.
extent-tree.c and volumes.c were both skipped, and there is definitely
more work todo in cleaning and commenting the code.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/async-thread.c b/fs/btrfs/async-thread.c
index 4e780b2..04fb970 100644
--- a/fs/btrfs/async-thread.c
+++ b/fs/btrfs/async-thread.c
@@ -231,17 +231,25 @@
/*
* if we pick a busy task, move the task to the end of the list.
- * hopefully this will keep things somewhat evenly balanced
+ * hopefully this will keep things somewhat evenly balanced.
+ * Do the move in batches based on the sequence number. This groups
+ * requests submitted at roughly the same time onto the same worker.
*/
next = workers->worker_list.next;
worker = list_entry(next, struct btrfs_worker_thread, worker_list);
atomic_inc(&worker->num_pending);
worker->sequence++;
+
if (worker->sequence % workers->idle_thresh == 0)
list_move_tail(next, &workers->worker_list);
return worker;
}
+/*
+ * selects a worker thread to take the next job. This will either find
+ * an idle worker, start a new worker up to the max count, or just return
+ * one of the existing busy workers.
+ */
static struct btrfs_worker_thread *find_worker(struct btrfs_workers *workers)
{
struct btrfs_worker_thread *worker;