bcachefs: Btree key cache coherency

This is the last piece for btree key cache coherency:

We already have:
 - btree iterator code checks the key cache when iterating over a cached
   btree
 - update path ensures that updates go to the key cache when updating a
   cached btree

But 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.

This patch implements that last piece: on a key cache update, if
creating a new key, we now also update the underlying btree.

This fixes a device removal bug, where deleting alloc info wasn't
correctly deleting all keys associated with a given device. It also
means we should be able to re-enable the key cache for inodes.

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/fs/bcachefs/btree_key_cache.c b/fs/bcachefs/btree_key_cache.c
index a575189f358c..5785efc8c276 100644
--- a/fs/bcachefs/btree_key_cache.c
+++ b/fs/bcachefs/btree_key_cache.c
@@ -562,6 +562,16 @@ bool bch2_btree_insert_key_cached(struct btree_trans *trans,
 	return true;
 }
 
+void bch2_btree_key_cache_drop(struct btree_trans *trans,
+			       struct btree_path *path)
+{
+	struct bkey_cached *ck = (void *) path->l[0].b;
+
+	ck->valid = false;
+
+	BUG_ON(test_bit(BKEY_CACHED_DIRTY, &ck->flags));
+}
+
 static unsigned long bch2_btree_key_cache_scan(struct shrinker *shrink,
 					   struct shrink_control *sc)
 {