bcache: Add btree_insert_node()

The flow of control in the old btree insertion code was rather -
backwards; we'd recurse down the btree (in btree_insert_recurse()), and
then if we needed to split the keys to be inserted into the parent node
would be effectively returned up to btree_insert_recurse(), which would
notice there was more work to do and finish the insertion.

The main problem with this was that the full logic for btree insertion
could only be used by calling btree_insert_recurse; if you'd gotten to a
btree leaf some other way and had a key to insert, if it turned out that
node needed to be split you were SOL.

This inverts the flow of control so btree_insert_node() does _full_
btree insertion, including splitting - and takes a (leaf) btree node to
insert into as a parameter.

This means we can now _correctly_ handle cache misses - for cache
misses, we need to insert a fake "check" key into the btree when we
discover we have a cache miss - while we still have the btree locked.
Previously, if the btree node was full inserting a cache miss would just
fail.

Signed-off-by: Kent Overstreet <kmo@daterainc.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/drivers/md/bcache/bset.c b/drivers/md/bcache/bset.c
index 22d1ae72c282..830eede86d56 100644
--- a/drivers/md/bcache/bset.c
+++ b/drivers/md/bcache/bset.c
@@ -73,6 +73,18 @@ struct bkey *bch_keylist_pop(struct keylist *l)
 	return l->top = k;
 }
 
+void bch_keylist_pop_front(struct keylist *l)
+{
+	struct bkey *next = bkey_next(l->bottom);
+	size_t bytes = ((void *) l->top) - ((void *) next);
+
+	memmove(l->bottom,
+		next,
+		bytes);
+
+	l->top = ((void *) l->bottom) + bytes;
+}
+
 /* Pointer validation */
 
 bool __bch_ptr_invalid(struct cache_set *c, int level, const struct bkey *k)