bcachefs: Fragmentation LRU

Now that we have much more efficient updates to the LRU btree, this
patch adds a new LRU that indexes buckets by fragmentation.

This means copygc no longer has to scan every bucket to find buckets
that need to be evacuated.

Changes:
 - A new field in bch_alloc_v4, fragmentation_lru - this corresponds to
   the bucket's position in the fragmentation LRU. We add a new field
   for this instead of calculating it as needed because we may make the
   fragmentation LRU optional; this field indicates whether a bucket is
   on the fragmentation LRU.

   Also, zoned devices will introduce variable bucket sizes; explicitly
   recording the LRU position will be safer for them.

 - A new copygc path for using the fragmentation LRU instead of
   scanning every bucket and building up an in-memory heap.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

1 files changed, 0 insertions, 1 deletions

diff --git a/fs/bcachefs/bcachefs.h b/fs/bcachefs/bcachefs.h
index 84b30adf56c9..5dc4b0c133ad 100644
--- a/fs/bcachefs/bcachefs.h
+++ b/fs/bcachefs/bcachefs.h
@@ -927,7 +927,6 @@ struct bch_fs {
 
 	/* COPYGC */
 	struct task_struct	*copygc_thread;
-	copygc_heap		copygc_heap;
 	struct write_point	copygc_write_point;
 	s64			copygc_wait;
 	bool			copygc_running;