bcachefs: Btree key cache coherency

 - Updates to non key cache iterators will now be transparently
   redirected to the key cache for cached btrees.

 - Except when creating new keys: then the update goes to underlying
   btree

For for iterating over a cached btree to work, we need to ensure that if
a key exists in the key cache, it also exists in the btree - otherwise
the iterator code will skip past it and not check the key cache.

Otherwise, for consistency, all updates should go to the same place -
the key cache.

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

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/bcachefs/btree_iter.c b/fs/bcachefs/btree_iter.c
index ff98024e76fc..c7ba6ce27007 100644
--- a/fs/bcachefs/btree_iter.c
+++ b/fs/bcachefs/btree_iter.c
@@ -2188,6 +2188,8 @@ struct bkey_i *__bch2_btree_trans_peek_updates(struct btree_iter *iter)
 			break;
 		if (bpos_cmp(i->k->k.p, iter->path->pos) < 0)
 			continue;
+		if (i->key_cache_already_flushed)
+			continue;
 		if (!ret || bpos_cmp(i->k->k.p, ret->k.p) < 0)
 			ret = i->k;
 	}