bcachefs fixes for 6.12

- Assorted tiny syzbot fixes
 - Shutdown path fix: "bch2_btree_write_buffer_flush_going_ro()"
 
   The shutdown path wasn't flushing the btree write buffer, leading to
   shutting down while we still had operations in flight. This fixes a
   whole slew of syzbot bugs, and undoubtedly other strange heisenbugs.
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Merge tag 'bcachefs-2024-11-13' of git://evilpiepirate.org/bcachefs

Pull bcachefs fixes from Kent Overstreet:
 "This fixes one minor regression from the btree cache fixes (in the
  scan_for_btree_nodes repair path) - and the shutdown path fix is the
  big one here, in terms of bugs closed:

   - Assorted tiny syzbot fixes

   - Shutdown path fix: "bch2_btree_write_buffer_flush_going_ro()"

     The shutdown path wasn't flushing the btree write buffer, leading
     to shutting down while we still had operations in flight. This
     fixes a whole slew of syzbot bugs, and undoubtedly other strange
     heisenbugs.

* tag 'bcachefs-2024-11-13' of git://evilpiepirate.org/bcachefs:
  bcachefs: Fix assertion pop in bch2_ptr_swab()
  bcachefs: Fix journal_entry_dev_usage_to_text() overrun
  bcachefs: Allow for unknown key types in backpointers fsck
  bcachefs: Fix assertion pop in topology repair
  bcachefs: Fix hidden btree errors when reading roots
  bcachefs: Fix validate_bset() repair path
  bcachefs: Fix missing validation for bch_backpointer.level
  bcachefs: Fix bch_member.btree_bitmap_shift validation
  bcachefs: bch2_btree_write_buffer_flush_going_ro()

fs/bcachefs/backpointers.c

@@ -52,6 +52,12 @@ int bch2_backpointer_validate(struct bch_fs *c, struct bkey_s_c k,
 			      enum bch_validate_flags flags)
 {
 	struct bkey_s_c_backpointer bp = bkey_s_c_to_backpointer(k);
+	int ret = 0;
+
+	bkey_fsck_err_on(bp.v->level > BTREE_MAX_DEPTH,
+			 c, backpointer_level_bad,
+			 "backpointer level bad: %u >= %u",
+			 bp.v->level, BTREE_MAX_DEPTH);
 
 	rcu_read_lock();
 	struct bch_dev *ca = bch2_dev_rcu_noerror(c, bp.k->p.inode);
@@ -64,7 +70,6 @@ int bch2_backpointer_validate(struct bch_fs *c, struct bkey_s_c k,
 	struct bpos bucket = bp_pos_to_bucket(ca, bp.k->p);
 	struct bpos bp_pos = bucket_pos_to_bp_noerror(ca, bucket, bp.v->bucket_offset);
 	rcu_read_unlock();
-	int ret = 0;
 
 	bkey_fsck_err_on((bp.v->bucket_offset >> MAX_EXTENT_COMPRESS_RATIO_SHIFT) >= ca->mi.bucket_size ||
 			 !bpos_eq(bp.k->p, bp_pos),
@@ -947,9 +952,13 @@ int bch2_check_extents_to_backpointers(struct bch_fs *c)
 static int check_one_backpointer(struct btree_trans *trans,
 				 struct bbpos start,
 				 struct bbpos end,
-				 struct bkey_s_c_backpointer bp,
+				 struct bkey_s_c bp_k,
 				 struct bkey_buf *last_flushed)
 {
+	if (bp_k.k->type != KEY_TYPE_backpointer)
+		return 0;
+
+	struct bkey_s_c_backpointer bp = bkey_s_c_to_backpointer(bp_k);
 	struct bch_fs *c = trans->c;
 	struct btree_iter iter;
 	struct bbpos pos = bp_to_bbpos(*bp.v);
@@ -1004,9 +1013,7 @@ static int bch2_check_backpointers_to_extents_pass(struct btree_trans *trans,
 				  POS_MIN, BTREE_ITER_prefetch, k,
 				  NULL, NULL, BCH_TRANS_COMMIT_no_enospc, ({
 			progress_update_iter(trans, &progress, &iter, "backpointers_to_extents");
-			check_one_backpointer(trans, start, end,
+			check_one_backpointer(trans, start, end, k, &last_flushed);
-					      bkey_s_c_to_backpointer(k),
-					      &last_flushed);
 	}));
 
 	bch2_bkey_buf_exit(&last_flushed, c);

fs/bcachefs/btree_gc.c

@@ -182,7 +182,7 @@ static int set_node_max(struct bch_fs *c, struct btree *b, struct bpos new_max)
 	bch2_btree_node_drop_keys_outside_node(b);
 
 	mutex_lock(&c->btree_cache.lock);
-	bch2_btree_node_hash_remove(&c->btree_cache, b);
+	__bch2_btree_node_hash_remove(&c->btree_cache, b);
 
 	bkey_copy(&b->key, &new->k_i);
 	ret = __bch2_btree_node_hash_insert(&c->btree_cache, b);

fs/bcachefs/btree_io.c

@@ -733,11 +733,8 @@ static int validate_bset(struct bch_fs *c, struct bch_dev *ca,
 			 c, ca, b, i, NULL,
 			 bset_past_end_of_btree_node,
 			 "bset past end of btree node (offset %u len %u but written %zu)",
-			 offset, sectors, ptr_written ?: btree_sectors(c))) {
+			 offset, sectors, ptr_written ?: btree_sectors(c)))
 		i->u64s = 0;
-		ret = 0;
-		goto out;
-	}
 
 	btree_err_on(offset && !i->u64s,
 		     -BCH_ERR_btree_node_read_err_fixable,
@@ -829,7 +826,6 @@ static int validate_bset(struct bch_fs *c, struct bch_dev *ca,
 			       BSET_BIG_ENDIAN(i), write,
 			       &bn->format);
 	}
-out:
 fsck_err:
 	printbuf_exit(&buf2);
 	printbuf_exit(&buf1);

fs/bcachefs/btree_update_interior.c

@@ -2398,7 +2398,8 @@ static int __bch2_btree_node_update_key(struct btree_trans *trans,
 	if (new_hash) {
 		mutex_lock(&c->btree_cache.lock);
 		bch2_btree_node_hash_remove(&c->btree_cache, new_hash);
-		bch2_btree_node_hash_remove(&c->btree_cache, b);
+
+		__bch2_btree_node_hash_remove(&c->btree_cache, b);
 
 		bkey_copy(&b->key, new_key);
 		ret = __bch2_btree_node_hash_insert(&c->btree_cache, b);

fs/bcachefs/btree_write_buffer.c

@@ -277,6 +277,10 @@ static int bch2_btree_write_buffer_flush_locked(struct btree_trans *trans)
 	bool accounting_replay_done = test_bit(BCH_FS_accounting_replay_done, &c->flags);
 	int ret = 0;
 
+	ret = bch2_journal_error(&c->journal);
+	if (ret)
+		return ret;
+
 	bch2_trans_unlock(trans);
 	bch2_trans_begin(trans);
 
@@ -491,7 +495,8 @@ static int fetch_wb_keys_from_journal(struct bch_fs *c, u64 seq)
 	return ret;
 }
 
-static int btree_write_buffer_flush_seq(struct btree_trans *trans, u64 seq)
+static int btree_write_buffer_flush_seq(struct btree_trans *trans, u64 seq,
+					bool *did_work)
 {
 	struct bch_fs *c = trans->c;
 	struct btree_write_buffer *wb = &c->btree_write_buffer;
@@ -502,6 +507,8 @@ static int btree_write_buffer_flush_seq(struct btree_trans *trans, u64 seq)
 
 		fetch_from_journal_err = fetch_wb_keys_from_journal(c, seq);
 
+		*did_work |= wb->inc.keys.nr || wb->flushing.keys.nr;
+
 		/*
 		 * On memory allocation failure, bch2_btree_write_buffer_flush_locked()
 		 * is not guaranteed to empty wb->inc:
@@ -521,17 +528,34 @@ static int bch2_btree_write_buffer_journal_flush(struct journal *j,
 				struct journal_entry_pin *_pin, u64 seq)
 {
 	struct bch_fs *c = container_of(j, struct bch_fs, journal);
+	bool did_work = false;
 
-	return bch2_trans_run(c, btree_write_buffer_flush_seq(trans, seq));
+	return bch2_trans_run(c, btree_write_buffer_flush_seq(trans, seq, &did_work));
 }
 
 int bch2_btree_write_buffer_flush_sync(struct btree_trans *trans)
 {
 	struct bch_fs *c = trans->c;
+	bool did_work = false;
 
 	trace_and_count(c, write_buffer_flush_sync, trans, _RET_IP_);
 
-	return btree_write_buffer_flush_seq(trans, journal_cur_seq(&c->journal));
+	return btree_write_buffer_flush_seq(trans, journal_cur_seq(&c->journal), &did_work);
+}
+
+/*
+ * The write buffer requires flushing when going RO: keys in the journal for the
+ * write buffer don't have a journal pin yet
+ */
+bool bch2_btree_write_buffer_flush_going_ro(struct bch_fs *c)
+{
+	if (bch2_journal_error(&c->journal))
+		return false;
+
+	bool did_work = false;
+	bch2_trans_run(c, btree_write_buffer_flush_seq(trans,
+				journal_cur_seq(&c->journal), &did_work));
+	return did_work;
 }
 
 int bch2_btree_write_buffer_flush_nocheck_rw(struct btree_trans *trans)

fs/bcachefs/btree_write_buffer.h

@@ -21,6 +21,7 @@ static inline bool bch2_btree_write_buffer_must_wait(struct bch_fs *c)
 
 struct btree_trans;
 int bch2_btree_write_buffer_flush_sync(struct btree_trans *);
+bool bch2_btree_write_buffer_flush_going_ro(struct bch_fs *);
 int bch2_btree_write_buffer_flush_nocheck_rw(struct btree_trans *);
 int bch2_btree_write_buffer_tryflush(struct btree_trans *);
 

fs/bcachefs/extents.c

@@ -1364,7 +1364,7 @@ void bch2_ptr_swab(struct bkey_s k)
 	for (entry = ptrs.start;
 	     entry < ptrs.end;
 	     entry = extent_entry_next(entry)) {
-		switch (extent_entry_type(entry)) {
+		switch (__extent_entry_type(entry)) {
 		case BCH_EXTENT_ENTRY_ptr:
 			break;
 		case BCH_EXTENT_ENTRY_crc32:
@@ -1384,6 +1384,9 @@ void bch2_ptr_swab(struct bkey_s k)
 			break;
 		case BCH_EXTENT_ENTRY_rebalance:
 			break;
+		default:
+			/* Bad entry type: will be caught by validate() */
+			return;
 		}
 	}
 }

fs/bcachefs/journal_io.c

@@ -708,6 +708,9 @@ static void journal_entry_dev_usage_to_text(struct printbuf *out, struct bch_fs
 		container_of(entry, struct jset_entry_dev_usage, entry);
 	unsigned i, nr_types = jset_entry_dev_usage_nr_types(u);
 
+	if (vstruct_bytes(entry) < sizeof(*u))
+		return;
+
 	prt_printf(out, "dev=%u", le32_to_cpu(u->dev));
 
 	printbuf_indent_add(out, 2);

fs/bcachefs/recovery_passes.c

@@ -27,6 +27,12 @@ const char * const bch2_recovery_passes[] = {
 	NULL
 };
 
+/* Fake recovery pass, so that scan_for_btree_nodes isn't 0: */
+static int bch2_recovery_pass_empty(struct bch_fs *c)
+{
+	return 0;
+}
+
 static int bch2_set_may_go_rw(struct bch_fs *c)
 {
 	struct journal_keys *keys = &c->journal_keys;

fs/bcachefs/recovery_passes_types.h

@@ -13,6 +13,7 @@
  * must never change:
  */
 #define BCH_RECOVERY_PASSES()							\
+	x(recovery_pass_empty,			41, PASS_SILENT)		\
 	x(scan_for_btree_nodes,			37, 0)				\
 	x(check_topology,			 4, 0)				\
 	x(accounting_read,			39, PASS_ALWAYS)		\

fs/bcachefs/sb-errors_format.h

@@ -136,7 +136,9 @@ enum bch_fsck_flags {
 	x(bucket_gens_nonzero_for_invalid_buckets,		122,	FSCK_AUTOFIX)	\
 	x(need_discard_freespace_key_to_invalid_dev_bucket,	123,	0)		\
 	x(need_discard_freespace_key_bad,			124,	0)		\
+	x(discarding_bucket_not_in_need_discard_btree,		291,	0)		\
 	x(backpointer_bucket_offset_wrong,			125,	0)		\
+	x(backpointer_level_bad,				294,	0)		\
 	x(backpointer_to_missing_device,			126,	0)		\
 	x(backpointer_to_missing_alloc,				127,	0)		\
 	x(backpointer_to_missing_ptr,				128,	0)		\
@@ -177,7 +179,9 @@ enum bch_fsck_flags {
 	x(ptr_stripe_redundant,					163,	0)		\
 	x(reservation_key_nr_replicas_invalid,			164,	0)		\
 	x(reflink_v_refcount_wrong,				165,	0)		\
+	x(reflink_v_pos_bad,					292,	0)		\
 	x(reflink_p_to_missing_reflink_v,			166,	0)		\
+	x(reflink_refcount_underflow,				293,	0)		\
 	x(stripe_pos_bad,					167,	0)		\
 	x(stripe_val_size_bad,					168,	0)		\
 	x(stripe_csum_granularity_bad,				290,	0)		\
@@ -302,7 +306,7 @@ enum bch_fsck_flags {
 	x(accounting_key_replicas_devs_unsorted,		280,	FSCK_AUTOFIX)	\
 	x(accounting_key_version_0,				282,	FSCK_AUTOFIX)	\
 	x(logged_op_but_clean,					283,	FSCK_AUTOFIX)	\
-	x(MAX,							291,	0)
+	x(MAX,							295,	0)
 
 enum bch_sb_error_id {
 #define x(t, n, ...) BCH_FSCK_ERR_##t = n,

fs/bcachefs/sb-members.c

@@ -163,7 +163,7 @@ static int validate_member(struct printbuf *err,
 		return -BCH_ERR_invalid_sb_members;
 	}
 
-	if (m.btree_bitmap_shift >= 64) {
+	if (m.btree_bitmap_shift >= BCH_MI_BTREE_BITMAP_SHIFT_MAX) {
 		prt_printf(err, "device %u: invalid btree_bitmap_shift %u", i, m.btree_bitmap_shift);
 		return -BCH_ERR_invalid_sb_members;
 	}
@@ -450,7 +450,7 @@ static void __bch2_dev_btree_bitmap_mark(struct bch_sb_field_members_v2 *mi, uns
 		m->btree_bitmap_shift += resize;
 	}
 
-	BUG_ON(m->btree_bitmap_shift > 57);
+	BUG_ON(m->btree_bitmap_shift >= BCH_MI_BTREE_BITMAP_SHIFT_MAX);
 	BUG_ON(end > 64ULL << m->btree_bitmap_shift);
 
 	for (unsigned bit = start >> m->btree_bitmap_shift;

fs/bcachefs/sb-members_format.h

@@ -65,6 +65,12 @@ struct bch_member {
 	__le32			last_journal_bucket_offset;
 };
 
+/*
+ * btree_allocated_bitmap can represent sector addresses of a u64: it itself has
+ * 64 elements, so 64 - ilog2(64)
+ */
+#define BCH_MI_BTREE_BITMAP_SHIFT_MAX	58
+
 /*
  * This limit comes from the bucket_gens array - it's a single allocation, and
  * kernel allocation are limited to INT_MAX

fs/bcachefs/super.c

@@ -272,6 +272,7 @@ static void __bch2_fs_read_only(struct bch_fs *c)
 		clean_passes++;
 
 		if (bch2_btree_interior_updates_flush(c) ||
+		    bch2_btree_write_buffer_flush_going_ro(c) ||
 		    bch2_journal_flush_all_pins(&c->journal) ||
 		    bch2_btree_flush_all_writes(c) ||
 		    seq != atomic64_read(&c->journal.seq)) {