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, 2 insertions, 1 deletions

diff --git a/fs/bcachefs/move.h b/fs/bcachefs/move.h
index aef613802935..c5a7c0add1d6 100644
--- a/fs/bcachefs/move.h
+++ b/fs/bcachefs/move.h
@@ -66,7 +66,8 @@ int bch2_move_data(struct bch_fs *,
 		   bool,
 		   move_pred_fn, void *);
 
-int __bch2_evacuate_bucket(struct moving_context *,
+int __bch2_evacuate_bucket(struct btree_trans *,
+			   struct moving_context *,
 			   struct bpos, int,
 			   struct data_update_opts);
 int bch2_evacuate_bucket(struct bch_fs *, struct bpos, int,