bcache: Add bch_keylist_init_single()

This will potentially save us an allocation when we've got inode/dirent bkeys
that don't fit in the keylist's inline keys.
Signed-off-by: Kent Overstreet <kmo@daterainc.com>

drivers/md/bcache/bset.h

@@ -478,6 +478,12 @@ static inline void bch_keylist_init(struct keylist *l)
 	l->top_p = l->keys_p = l->inline_keys;
 }
 
+static inline void bch_keylist_init_single(struct keylist *l, struct bkey *k)
+{
+	l->keys = k;
+	l->top = bkey_next(k);
+}
+
 static inline void bch_keylist_push(struct keylist *l)
 {
 	l->top = bkey_next(l->top);

drivers/md/bcache/journal.c

@@ -313,8 +313,6 @@ int bch_journal_replay(struct cache_set *s, struct list_head *list)
 	uint64_t start = i->j.last_seq, end = i->j.seq, n = start;
 	struct keylist keylist;
 
-	bch_keylist_init(&keylist);
-
 	list_for_each_entry(i, list, list) {
 		BUG_ON(i->pin && atomic_read(i->pin) != 1);
 
@@ -327,8 +325,7 @@ int bch_journal_replay(struct cache_set *s, struct list_head *list)
 		     k = bkey_next(k)) {
 			trace_bcache_journal_replay_key(k);
 
-			bkey_copy(keylist.top, k);
-			bch_keylist_push(&keylist);
+			bch_keylist_init_single(&keylist, k);
 
 			ret = bch_btree_insert(s, &keylist, i->pin, NULL);
 			if (ret)