bcachefs: Write lock btree node in key cache fills

this addresses a key cache coherency bug

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

diff --git a/fs/bcachefs/btree_key_cache.c b/fs/bcachefs/btree_key_cache.c
index 4eba2871f28933660b25d245dda2274e9d0db850..382f99b774b8fd6f499988281948fa143d6a33bc 100644 (file)
--- a/fs/bcachefs/btree_key_cache.c
+++ b/fs/bcachefs/btree_key_cache.c
@@ -197,7 +197,9 @@ out:
        return ck;
 }
 
-static int btree_key_cache_create(struct btree_trans *trans, struct btree_path *path,
+static int btree_key_cache_create(struct btree_trans *trans,
+                                 struct btree_path *path,
+                                 struct btree_path *ck_path,
                                  struct bkey_s_c k)
 {
        struct bch_fs *c = trans->c;
@@ -217,7 +219,7 @@ static int btree_key_cache_create(struct btree_trans *trans, struct btree_path *
        key_u64s = min(256U, (key_u64s * 3) / 2);
        key_u64s = roundup_pow_of_two(key_u64s);
 
-       struct bkey_cached *ck = bkey_cached_alloc(trans, path, key_u64s);
+       struct bkey_cached *ck = bkey_cached_alloc(trans, ck_path, key_u64s);
        int ret = PTR_ERR_OR_ZERO(ck);
        if (ret)
                return ret;
@@ -226,19 +228,19 @@ static int btree_key_cache_create(struct btree_trans *trans, struct btree_path *
                ck = bkey_cached_reuse(bc);
                if (unlikely(!ck)) {
                        bch_err(c, "error allocating memory for key cache item, btree %s",
-                               bch2_btree_id_str(path->btree_id));
+                               bch2_btree_id_str(ck_path->btree_id));
                        return -BCH_ERR_ENOMEM_btree_key_cache_create;
                }
        }
 
        ck->c.level             = 0;
-       ck->c.btree_id          = path->btree_id;
-       ck->key.btree_id        = path->btree_id;
-       ck->key.pos             = path->pos;
+       ck->c.btree_id          = ck_path->btree_id;
+       ck->key.btree_id        = ck_path->btree_id;
+       ck->key.pos             = ck_path->pos;
        ck->flags               = 1U << BKEY_CACHED_ACCESSED;
 
        if (unlikely(key_u64s > ck->u64s)) {
-               mark_btree_node_locked_noreset(path, 0, BTREE_NODE_UNLOCKED);
+               mark_btree_node_locked_noreset(ck_path, 0, BTREE_NODE_UNLOCKED);
 
                struct bkey_i *new_k = allocate_dropping_locks(trans, ret,
                                kmalloc(key_u64s * sizeof(u64), _gfp));
@@ -258,22 +260,29 @@ static int btree_key_cache_create(struct btree_trans *trans, struct btree_path *
 
        bkey_reassemble(ck->k, k);
 
+       ret = bch2_btree_node_lock_write(trans, path, &path_l(path)->b->c);
+       if (unlikely(ret))
+               goto err;
+
        ret = rhashtable_lookup_insert_fast(&bc->table, &ck->hash, bch2_btree_key_cache_params);
+
+       bch2_btree_node_unlock_write(trans, path, path_l(path)->b);
+
        if (unlikely(ret)) /* raced with another fill? */
                goto err;
 
        atomic_long_inc(&bc->nr_keys);
        six_unlock_write(&ck->c.lock);
 
-       enum six_lock_type lock_want = __btree_lock_want(path, 0);
+       enum six_lock_type lock_want = __btree_lock_want(ck_path, 0);
        if (lock_want == SIX_LOCK_read)
                six_lock_downgrade(&ck->c.lock);
-       btree_path_cached_set(trans, path, ck, (enum btree_node_locked_type) lock_want);
-       path->uptodate = BTREE_ITER_UPTODATE;
+       btree_path_cached_set(trans, ck_path, ck, (enum btree_node_locked_type) lock_want);
+       ck_path->uptodate = BTREE_ITER_UPTODATE;
        return 0;
 err:
        bkey_cached_free(bc, ck);
-       mark_btree_node_locked_noreset(path, 0, BTREE_NODE_UNLOCKED);
+       mark_btree_node_locked_noreset(ck_path, 0, BTREE_NODE_UNLOCKED);
 
        return ret;
 }
@@ -293,6 +302,7 @@ static noinline int btree_key_cache_fill(struct btree_trans *trans,
        int ret;
 
        bch2_trans_iter_init(trans, &iter, ck_path->btree_id, ck_path->pos,
+                            BTREE_ITER_intent|
                             BTREE_ITER_key_cache_fill|
                             BTREE_ITER_cached_nofill);
        iter.flags &= ~BTREE_ITER_with_journal;
@@ -306,7 +316,7 @@ static noinline int btree_key_cache_fill(struct btree_trans *trans,
        if (unlikely(ret))
                goto out;
 
-       ret = btree_key_cache_create(trans, ck_path, k);
+       ret = btree_key_cache_create(trans, btree_iter_path(trans, &iter), ck_path, k);
        if (ret)
                goto err;