Merge tag 'bcachefs-2024-06-12' of https://evilpiepirate.org/git/bcachefs

Pull bcachefs fixes from Kent Overstreet:

 - fix kworker explosion, due to calling submit_bio() (which can block)
   from a multithreaded workqueue

 - fix error handling in btree node scan

 - forward compat fix: kill an old debug assert

 - key cache shrinker fixes

   This is a partial fix for stalls doing multithreaded creates - there
   were various O(n^2) issues the key cache shrinker was hitting [1].

   There's more work coming here; I'm working on a patch to delete the
   key cache lock, which initial testing shows to be a pretty drastic
   performance improvement

 - assorted syzbot fixes

Link: https://lore.kernel.org/linux-bcachefs/CAGudoHGenxzk0ZqPXXi1_QDbfqQhGHu+wUwzyS6WmfkUZ1HiXA@mail.gmail.com/ [1]

* tag 'bcachefs-2024-06-12' of https://evilpiepirate.org/git/bcachefs:
  bcachefs: Fix rcu_read_lock() leak in drop_extra_replicas
  bcachefs: Add missing bch_inode_info.ei_flags init
  bcachefs: Add missing synchronize_srcu_expedited() call when shutting down
  bcachefs: Check for invalid bucket from bucket_gen(), gc_bucket()
  bcachefs: Replace bucket_valid() asserts in bucket lookup with proper checks
  bcachefs: Fix snapshot_create_lock lock ordering
  bcachefs: Fix refcount leak in check_fix_ptrs()
  bcachefs: Leave a buffer in the btree key cache to avoid lock thrashing
  bcachefs: Fix reporting of freed objects from key cache shrinker
  bcachefs: set sb->s_shrinker->seeks = 0
  bcachefs: increase key cache shrinker batch size
  bcachefs: Enable automatic shrinking for rhashtables
  bcachefs: fix the display format for show-super
  bcachefs: fix stack frame size in fsck.c
  bcachefs: Delete incorrect BTREE_ID_NR assertion
  bcachefs: Fix incorrect error handling found_btree_node_is_readable()
  bcachefs: Split out btree_write_submit_wq

Author: torvalds

fs/bcachefs/alloc_background.c

@@ -741,6 +741,7 @@ int bch2_trigger_alloc(struct btree_trans *trans,
 		       enum btree_iter_update_trigger_flags flags)
 {
 	struct bch_fs *c = trans->c;
+	struct printbuf buf = PRINTBUF;
 	int ret = 0;
 
 	struct bch_dev *ca = bch2_dev_bucket_tryget(c, new.k->p);
@@ -860,8 +861,14 @@ int bch2_trigger_alloc(struct btree_trans *trans,
 		}
 
 		percpu_down_read(&c->mark_lock);
-		if (new_a->gen != old_a->gen)
-			*bucket_gen(ca, new.k->p.offset) = new_a->gen;
+		if (new_a->gen != old_a->gen) {
+			u8 *gen = bucket_gen(ca, new.k->p.offset);
+			if (unlikely(!gen)) {
+				percpu_up_read(&c->mark_lock);
+				goto invalid_bucket;
+			}
+			*gen = new_a->gen;
+		}
 
 		bch2_dev_usage_update(c, ca, old_a, new_a, journal_seq, false);
 		percpu_up_read(&c->mark_lock);
@@ -895,6 +902,11 @@ int bch2_trigger_alloc(struct btree_trans *trans,
 
 		percpu_down_read(&c->mark_lock);
 		struct bucket *g = gc_bucket(ca, new.k->p.offset);
+		if (unlikely(!g)) {
+			percpu_up_read(&c->mark_lock);
+			goto invalid_bucket;
+		}
+		g->gen_valid	= 1;
 
 		bucket_lock(g);
 
@@ -910,8 +922,14 @@ int bch2_trigger_alloc(struct btree_trans *trans,
 		percpu_up_read(&c->mark_lock);
 	}
 err:
+	printbuf_exit(&buf);
 	bch2_dev_put(ca);
 	return ret;
+invalid_bucket:
+	bch2_fs_inconsistent(c, "reference to invalid bucket\n  %s",
+			     (bch2_bkey_val_to_text(&buf, c, new.s_c), buf.buf));
+	ret = -EIO;
+	goto err;
 }
 
 /*

fs/bcachefs/bcachefs.h

@@ -790,7 +790,8 @@ struct bch_fs {
 
 	/* BTREE CACHE */
 	struct bio_set		btree_bio;
-	struct workqueue_struct	*io_complete_wq;
+	struct workqueue_struct	*btree_read_complete_wq;
+	struct workqueue_struct	*btree_write_submit_wq;
 
 	struct btree_root	btree_roots_known[BTREE_ID_NR];
 	DARRAY(struct btree_root) btree_roots_extra;

fs/bcachefs/btree_cache.c

@@ -91,10 +91,11 @@ static int bch2_btree_cache_cmp_fn(struct rhashtable_compare_arg *arg,
 }
 
 static const struct rhashtable_params bch_btree_cache_params = {
-	.head_offset	= offsetof(struct btree, hash),
-	.key_offset	= offsetof(struct btree, hash_val),
-	.key_len	= sizeof(u64),
-	.obj_cmpfn	= bch2_btree_cache_cmp_fn,
+	.head_offset		= offsetof(struct btree, hash),
+	.key_offset		= offsetof(struct btree, hash_val),
+	.key_len		= sizeof(u64),
+	.obj_cmpfn		= bch2_btree_cache_cmp_fn,
+	.automatic_shrinking	= true,
 };
 
 static int btree_node_data_alloc(struct bch_fs *c, struct btree *b, gfp_t gfp)

fs/bcachefs/btree_gc.c

@@ -874,6 +874,9 @@ static int bch2_alloc_write_key(struct btree_trans *trans,
 	const struct bch_alloc_v4 *old;
 	int ret;
 
+	if (!bucket_valid(ca, k.k->p.offset))
+		return 0;
+
 	old = bch2_alloc_to_v4(k, &old_convert);
 	gc = new = *old;
 
@@ -990,6 +993,8 @@ static int bch2_gc_alloc_start(struct bch_fs *c)
 
 		buckets->first_bucket	= ca->mi.first_bucket;
 		buckets->nbuckets	= ca->mi.nbuckets;
+		buckets->nbuckets_minus_first =
+			buckets->nbuckets - buckets->first_bucket;
 		rcu_assign_pointer(ca->buckets_gc, buckets);
 	}
 
@@ -1003,12 +1008,14 @@ static int bch2_gc_alloc_start(struct bch_fs *c)
 				continue;
 			}
 
-			struct bch_alloc_v4 a_convert;
-			const struct bch_alloc_v4 *a = bch2_alloc_to_v4(k, &a_convert);
+			if (bucket_valid(ca, k.k->p.offset)) {
+				struct bch_alloc_v4 a_convert;
+				const struct bch_alloc_v4 *a = bch2_alloc_to_v4(k, &a_convert);
 
-			struct bucket *g = gc_bucket(ca, k.k->p.offset);
-			g->gen_valid	= 1;
-			g->gen		= a->gen;
+				struct bucket *g = gc_bucket(ca, k.k->p.offset);
+				g->gen_valid	= 1;
+				g->gen		= a->gen;
+			}
 			0;
 		})));
 	bch2_dev_put(ca);

fs/bcachefs/btree_io.c

@@ -1389,7 +1389,7 @@ static void btree_node_read_endio(struct bio *bio)
 		bch2_latency_acct(ca, rb->start_time, READ);
 	}
 
-	queue_work(c->io_complete_wq, &rb->work);
+	queue_work(c->btree_read_complete_wq, &rb->work);
 }
 
 struct btree_node_read_all {
@@ -1656,7 +1656,7 @@ static int btree_node_read_all_replicas(struct bch_fs *c, struct btree *b, bool
 		btree_node_read_all_replicas_done(&ra->cl.work);
 	} else {
 		continue_at(&ra->cl, btree_node_read_all_replicas_done,
-			    c->io_complete_wq);
+			    c->btree_read_complete_wq);
 	}
 
 	return 0;
@@ -1737,7 +1737,7 @@ void bch2_btree_node_read(struct btree_trans *trans, struct btree *b,
 		if (sync)
 			btree_node_read_work(&rb->work);
 		else
-			queue_work(c->io_complete_wq, &rb->work);
+			queue_work(c->btree_read_complete_wq, &rb->work);
 	}
 }
 
@@ -2229,7 +2229,7 @@ void __bch2_btree_node_write(struct bch_fs *c, struct btree *b, unsigned flags)
 	atomic64_add(bytes_to_write, &c->btree_write_stats[type].bytes);
 
 	INIT_WORK(&wbio->work, btree_write_submit);
-	queue_work(c->io_complete_wq, &wbio->work);
+	queue_work(c->btree_write_submit_wq, &wbio->work);
 	return;
 err:
 	set_btree_node_noevict(b);

fs/bcachefs/btree_iter.c

@@ -221,11 +221,8 @@ static void bch2_btree_path_verify(struct btree_trans *trans,
 				   struct btree_path *path)
 {
 	struct bch_fs *c = trans->c;
-	unsigned i;
-
-	EBUG_ON(path->btree_id >= BTREE_ID_NR);
 
-	for (i = 0; i < (!path->cached ? BTREE_MAX_DEPTH : 1); i++) {
+	for (unsigned i = 0; i < (!path->cached ? BTREE_MAX_DEPTH : 1); i++) {
 		if (!path->l[i].b) {
 			BUG_ON(!path->cached &&
 			       bch2_btree_id_root(c, path->btree_id)->b->c.level > i);
@@ -251,8 +248,6 @@ static void bch2_btree_iter_verify(struct btree_iter *iter)
 {
 	struct btree_trans *trans = iter->trans;
 
-	BUG_ON(iter->btree_id >= BTREE_ID_NR);
-
 	BUG_ON(!!(iter->flags & BTREE_ITER_cached) != btree_iter_path(trans, iter)->cached);
 
 	BUG_ON((iter->flags & BTREE_ITER_is_extents) &&
@@ -3406,8 +3401,10 @@ void bch2_fs_btree_iter_exit(struct bch_fs *c)
 		bch2_time_stats_exit(&s->lock_hold_times);
 	}
 
-	if (c->btree_trans_barrier_initialized)
+	if (c->btree_trans_barrier_initialized) {
+		synchronize_srcu_expedited(&c->btree_trans_barrier);
 		cleanup_srcu_struct(&c->btree_trans_barrier);
+	}
 	mempool_exit(&c->btree_trans_mem_pool);
 	mempool_exit(&c->btree_trans_pool);
 }

fs/bcachefs/btree_key_cache.c

@@ -32,10 +32,11 @@ static int bch2_btree_key_cache_cmp_fn(struct rhashtable_compare_arg *arg,
 }
 
 static const struct rhashtable_params bch2_btree_key_cache_params = {
-	.head_offset	= offsetof(struct bkey_cached, hash),
-	.key_offset	= offsetof(struct bkey_cached, key),
-	.key_len	= sizeof(struct bkey_cached_key),
-	.obj_cmpfn	= bch2_btree_key_cache_cmp_fn,
+	.head_offset		= offsetof(struct bkey_cached, hash),
+	.key_offset		= offsetof(struct bkey_cached, key),
+	.key_len		= sizeof(struct bkey_cached_key),
+	.obj_cmpfn		= bch2_btree_key_cache_cmp_fn,
+	.automatic_shrinking	= true,
 };
 
 __flatten
@@ -840,7 +841,6 @@ static unsigned long bch2_btree_key_cache_scan(struct shrinker *shrink,
 		six_lock_exit(&ck->c.lock);
 		kmem_cache_free(bch2_key_cache, ck);
 		atomic_long_dec(&bc->nr_freed);
-		freed++;
 		bc->nr_freed_nonpcpu--;
 		bc->freed++;
 	}
@@ -854,7 +854,6 @@ static unsigned long bch2_btree_key_cache_scan(struct shrinker *shrink,
 		six_lock_exit(&ck->c.lock);
 		kmem_cache_free(bch2_key_cache, ck);
 		atomic_long_dec(&bc->nr_freed);
-		freed++;
 		bc->nr_freed_pcpu--;
 		bc->freed++;
 	}
@@ -876,23 +875,22 @@ static unsigned long bch2_btree_key_cache_scan(struct shrinker *shrink,
 
 			if (test_bit(BKEY_CACHED_DIRTY, &ck->flags)) {
 				bc->skipped_dirty++;
-				goto next;
 			} else if (test_bit(BKEY_CACHED_ACCESSED, &ck->flags)) {
 				clear_bit(BKEY_CACHED_ACCESSED, &ck->flags);
 				bc->skipped_accessed++;
-				goto next;
-			} else if (bkey_cached_lock_for_evict(ck)) {
+			} else if (!bkey_cached_lock_for_evict(ck)) {
+				bc->skipped_lock_fail++;
+			} else {
 				bkey_cached_evict(bc, ck);
 				bkey_cached_free(bc, ck);
 				bc->moved_to_freelist++;
-			} else {
-				bc->skipped_lock_fail++;
+				freed++;
 			}
 
 			scanned++;
 			if (scanned >= nr)
 				break;
-next:
+
 			pos = next;
 		}
 
@@ -917,6 +915,14 @@ static unsigned long bch2_btree_key_cache_count(struct shrinker *shrink,
 	long nr = atomic_long_read(&bc->nr_keys) -
 		atomic_long_read(&bc->nr_dirty);
 
+	/*
+	 * Avoid hammering our shrinker too much if it's nearly empty - the
+	 * shrinker code doesn't take into account how big our cache is, if it's
+	 * mostly empty but the system is under memory pressure it causes nasty
+	 * lock contention:
+	 */
+	nr -= 128;
+
 	return max(0L, nr);
 }
 
@@ -1025,9 +1031,10 @@ int bch2_fs_btree_key_cache_init(struct btree_key_cache *bc)
 	if (!shrink)
 		return -BCH_ERR_ENOMEM_fs_btree_cache_init;
 	bc->shrink = shrink;
-	shrink->seeks		= 0;
 	shrink->count_objects	= bch2_btree_key_cache_count;
 	shrink->scan_objects	= bch2_btree_key_cache_scan;
+	shrink->batch		= 1 << 14;
+	shrink->seeks		= 0;
 	shrink->private_data	= c;
 	shrinker_register(shrink);
 	return 0;

fs/bcachefs/btree_node_scan.c

@@ -72,10 +72,11 @@ static bool found_btree_node_is_readable(struct btree_trans *trans,
 
 	struct btree *b = bch2_btree_node_get_noiter(trans, &k.k, f->btree_id, f->level, false);
 	bool ret = !IS_ERR_OR_NULL(b);
-	if (ret) {
-		f->sectors_written = b->written;
-		six_unlock_read(&b->c.lock);
-	}
+	if (!ret)
+		return ret;
+
+	f->sectors_written = b->written;
+	six_unlock_read(&b->c.lock);
 
 	/*
 	 * We might update this node's range; if that happens, we need the node