six locks: Kill six_lock_pcpu_(alloc|free)

six_lock_pcpu_alloc() is an unsafe interface: it's not safe to allocate
or free the percpu reader count on an existing lock that's in use, the
only safe time to allocate percpu readers is when the lock is first
being initialized.

This patch adds a flags parameter to six_lock_init(), and instead of
six_lock_pcpu_free() we now expose six_lock_exit(), which does the same
thing but is less likely to be misused.

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

1 files changed, 4 insertions, 4 deletions

diff --git a/fs/bcachefs/btree_cache.c b/fs/bcachefs/btree_cache.c
index 76e08f2f6689..5801f4ff9097 100644
--- a/fs/bcachefs/btree_cache.c
+++ b/fs/bcachefs/btree_cache.c
@@ -121,7 +121,6 @@ static struct btree *__btree_node_mem_alloc(struct bch_fs *c, gfp_t gfp)
 		return NULL;
 
 	bkey_btree_ptr_init(&b->key);
-	bch2_btree_lock_init(&b->c);
 	INIT_LIST_HEAD(&b->list);
 	INIT_LIST_HEAD(&b->write_blocked);
 	b->byte_order = ilog2(btree_bytes(c));
@@ -142,6 +141,8 @@ struct btree *__bch2_btree_node_mem_alloc(struct bch_fs *c)
 		return NULL;
 	}
 
+	bch2_btree_lock_init(&b->c, 0);
+
 	bc->used++;
 	list_add(&b->list, &bc->freeable);
 	return b;
@@ -435,7 +436,7 @@ void bch2_fs_btree_cache_exit(struct bch_fs *c)
 	while (!list_empty(&bc->freed_nonpcpu)) {
 		b = list_first_entry(&bc->freed_nonpcpu, struct btree, list);
 		list_del(&b->list);
-		six_lock_pcpu_free(&b->c.lock);
+		six_lock_exit(&b->c.lock);
 		kfree(b);
 	}
 
@@ -595,8 +596,7 @@ struct btree *bch2_btree_node_mem_alloc(struct btree_trans *trans, bool pcpu_rea
 		mutex_lock(&bc->lock);
 	}
 
-	if (pcpu_read_locks)
-		six_lock_pcpu_alloc(&b->c.lock);
+	bch2_btree_lock_init(&b->c, pcpu_read_locks ? SIX_LOCK_INIT_PCPU : 0);
 
 	BUG_ON(!six_trylock_intent(&b->c.lock));
 	BUG_ON(!six_trylock_write(&b->c.lock));