bcachefs: Heap allocate printbufs

This patch changes printbufs dynamically allocate and reallocate a
buffer as needed. Stack usage has become a bit of a problem, and a major
cause of that has been static size string buffers on the stack.

The most involved part of this refactoring is that printbufs must now be
exited with printbuf_exit().
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/bkey.c

@@ -57,11 +57,12 @@ static void bch2_bkey_pack_verify(const struct bkey_packed *packed,
 	tmp = __bch2_bkey_unpack_key(format, packed);
 
 	if (memcmp(&tmp, unpacked, sizeof(struct bkey))) {
-		char buf1[160], buf2[160];
+		struct printbuf buf1 = PRINTBUF;
+		struct printbuf buf2 = PRINTBUF;
 		char buf3[160], buf4[160];
 
-		bch2_bkey_to_text(&PBUF(buf1), unpacked);
-		bch2_bkey_to_text(&PBUF(buf2), &tmp);
+		bch2_bkey_to_text(&buf1, unpacked);
+		bch2_bkey_to_text(&buf2, &tmp);
 		bch2_to_binary(buf3, (void *) unpacked, 80);
 		bch2_to_binary(buf4, high_word(format, packed), 80);
 
@@ -72,7 +73,7 @@ static void bch2_bkey_pack_verify(const struct bkey_packed *packed,
 		      format->bits_per_field[2],
 		      format->bits_per_field[3],
 		      format->bits_per_field[4],
-		      buf1, buf2, buf3, buf4);
+		      buf1.buf, buf2.buf, buf3, buf4);
 	}
 }
 

fs/bcachefs/bset.c

@@ -58,7 +58,7 @@ void bch2_dump_bset(struct bch_fs *c, struct btree *b,
 	struct bkey_packed *_k, *_n;
 	struct bkey uk, n;
 	struct bkey_s_c k;
-	char buf[200];
+	struct printbuf buf = PRINTBUF;
 
 	if (!i->u64s)
 		return;
@@ -69,12 +69,14 @@ void bch2_dump_bset(struct bch_fs *c, struct btree *b,
 		_n = bkey_next(_k);
 
 		k = bkey_disassemble(b, _k, &uk);
+
+		printbuf_reset(&buf);
 		if (c)
-			bch2_bkey_val_to_text(&PBUF(buf), c, k);
+			bch2_bkey_val_to_text(&buf, c, k);
 		else
-			bch2_bkey_to_text(&PBUF(buf), k.k);
+			bch2_bkey_to_text(&buf, k.k);
 		printk(KERN_ERR "block %u key %5zu: %s\n", set,
-		       _k->_data - i->_data, buf);
+		       _k->_data - i->_data, buf.buf);
 
 		if (_n == vstruct_last(i))
 			continue;
@@ -90,6 +92,8 @@ void bch2_dump_bset(struct bch_fs *c, struct btree *b,
 		    !bpos_cmp(n.p, k.k->p))
 			printk(KERN_ERR "Duplicate keys\n");
 	}
+
+	printbuf_exit(&buf);
 }
 
 void bch2_dump_btree_node(struct bch_fs *c, struct btree *b)
@@ -106,6 +110,7 @@ void bch2_dump_btree_node_iter(struct btree *b,
 			      struct btree_node_iter *iter)
 {
 	struct btree_node_iter_set *set;
+	struct printbuf buf = PRINTBUF;
 
 	printk(KERN_ERR "btree node iter with %u/%u sets:\n",
 	       __btree_node_iter_used(iter), b->nsets);
@@ -114,12 +119,14 @@ void bch2_dump_btree_node_iter(struct btree *b,
 		struct bkey_packed *k = __btree_node_offset_to_key(b, set->k);
 		struct bset_tree *t = bch2_bkey_to_bset(b, k);
 		struct bkey uk = bkey_unpack_key(b, k);
-		char buf[100];
 
-		bch2_bkey_to_text(&PBUF(buf), &uk);
+		printbuf_reset(&buf);
+		bch2_bkey_to_text(&buf, &uk);
 		printk(KERN_ERR "set %zu key %u: %s\n",
-		       t - b->set, set->k, buf);
+		       t - b->set, set->k, buf.buf);
 	}
+
+	printbuf_exit(&buf);
 }
 
 #ifdef CONFIG_BCACHEFS_DEBUG
@@ -155,13 +162,14 @@ static void bch2_btree_node_iter_next_check(struct btree_node_iter *_iter,
 		struct btree_node_iter_set *set;
 		struct bkey ku = bkey_unpack_key(b, k);
 		struct bkey nu = bkey_unpack_key(b, n);
-		char buf1[80], buf2[80];
+		struct printbuf buf1 = PRINTBUF;
+		struct printbuf buf2 = PRINTBUF;
 
 		bch2_dump_btree_node(NULL, b);
-		bch2_bkey_to_text(&PBUF(buf1), &ku);
-		bch2_bkey_to_text(&PBUF(buf2), &nu);
+		bch2_bkey_to_text(&buf1, &ku);
+		bch2_bkey_to_text(&buf2, &nu);
 		printk(KERN_ERR "out of order/overlapping:\n%s\n%s\n",
-		       buf1, buf2);
+		       buf1.buf, buf2.buf);
 		printk(KERN_ERR "iter was:");
 
 		btree_node_iter_for_each(_iter, set) {
@@ -226,6 +234,8 @@ void bch2_verify_insert_pos(struct btree *b, struct bkey_packed *where,
 	struct bset_tree *t = bch2_bkey_to_bset(b, where);
 	struct bkey_packed *prev = bch2_bkey_prev_all(b, t, where);
 	struct bkey_packed *next = (void *) (where->_data + clobber_u64s);
+	struct printbuf buf1 = PRINTBUF;
+	struct printbuf buf2 = PRINTBUF;
 #if 0
 	BUG_ON(prev &&
 	       bkey_iter_cmp(b, prev, insert) > 0);
@@ -234,17 +244,15 @@ void bch2_verify_insert_pos(struct btree *b, struct bkey_packed *where,
 	    bkey_iter_cmp(b, prev, insert) > 0) {
 		struct bkey k1 = bkey_unpack_key(b, prev);
 		struct bkey k2 = bkey_unpack_key(b, insert);
-		char buf1[100];
-		char buf2[100];
 
 		bch2_dump_btree_node(NULL, b);
-		bch2_bkey_to_text(&PBUF(buf1), &k1);
-		bch2_bkey_to_text(&PBUF(buf2), &k2);
+		bch2_bkey_to_text(&buf1, &k1);
+		bch2_bkey_to_text(&buf2, &k2);
 
 		panic("prev > insert:\n"
 		      "prev    key %s\n"
 		      "insert  key %s\n",
-		      buf1, buf2);
+		      buf1.buf, buf2.buf);
 	}
 #endif
 #if 0
@@ -255,17 +263,15 @@ void bch2_verify_insert_pos(struct btree *b, struct bkey_packed *where,
 	    bkey_iter_cmp(b, insert, next) > 0) {
 		struct bkey k1 = bkey_unpack_key(b, insert);
 		struct bkey k2 = bkey_unpack_key(b, next);
-		char buf1[100];
-		char buf2[100];
 
 		bch2_dump_btree_node(NULL, b);
-		bch2_bkey_to_text(&PBUF(buf1), &k1);
-		bch2_bkey_to_text(&PBUF(buf2), &k2);
+		bch2_bkey_to_text(&buf1, &k1);
+		bch2_bkey_to_text(&buf2, &k2);
 
 		panic("insert > next:\n"
 		      "insert  key %s\n"
 		      "next    key %s\n",
-		      buf1, buf2);
+		      buf1.buf, buf2.buf);
 	}
 #endif
 }
@@ -1555,9 +1561,6 @@ void bch2_bfloat_to_text(struct printbuf *out, struct btree *b,
 	struct bkey uk;
 	unsigned j, inorder;
 
-	if (out->pos != out->end)
-		*out->pos = '\0';
-
 	if (!bset_has_ro_aux_tree(t))
 		return;
 

fs/bcachefs/btree_cache.c

@@ -742,14 +742,16 @@ static int lock_node_check_fn(struct six_lock *lock, void *p)
 
 static noinline void btree_bad_header(struct bch_fs *c, struct btree *b)
 {
-	char buf1[200], buf2[100], buf3[100];
+	struct printbuf buf1 = PRINTBUF;
+	struct printbuf buf2 = PRINTBUF;
+	struct printbuf buf3 = PRINTBUF;
 
 	if (!test_bit(BCH_FS_INITIAL_GC_DONE, &c->flags))
 		return;
 
-	bch2_bkey_val_to_text(&PBUF(buf1), c, bkey_i_to_s_c(&b->key));
-	bch2_bpos_to_text(&PBUF(buf2), b->data->min_key);
-	bch2_bpos_to_text(&PBUF(buf3), b->data->max_key);
+	bch2_bkey_val_to_text(&buf1, c, bkey_i_to_s_c(&b->key));
+	bch2_bpos_to_text(&buf2, b->data->min_key);
+	bch2_bpos_to_text(&buf3, b->data->max_key);
 
 	bch2_fs_inconsistent(c, "btree node header doesn't match ptr\n"
 			     "btree %s level %u\n"
@@ -757,10 +759,14 @@ static noinline void btree_bad_header(struct bch_fs *c, struct btree *b)
 			     "header: btree %s level %llu\n"
 			     "min %s max %s\n",
 			     bch2_btree_ids[b->c.btree_id], b->c.level,
-			     buf1,
+			     buf1.buf,
 			     bch2_btree_ids[BTREE_NODE_ID(b->data)],
 			     BTREE_NODE_LEVEL(b->data),
-			     buf2, buf3);
+			     buf2.buf, buf3.buf);
+
+	printbuf_exit(&buf3);
+	printbuf_exit(&buf2);
+	printbuf_exit(&buf1);
 }
 
 static inline void btree_check_header(struct bch_fs *c, struct btree *b)

fs/bcachefs/btree_iter.c

@@ -574,7 +574,9 @@ static void bch2_btree_path_verify_level(struct btree_trans *trans,
 	struct btree_node_iter tmp;
 	bool locked;
 	struct bkey_packed *p, *k;
-	char buf1[100], buf2[100], buf3[100];
+	struct printbuf buf1 = PRINTBUF;
+	struct printbuf buf2 = PRINTBUF;
+	struct printbuf buf3 = PRINTBUF;
 	const char *msg;
 
 	if (!bch2_debug_check_iterators)
@@ -622,26 +624,27 @@ static void bch2_btree_path_verify_level(struct btree_trans *trans,
 		btree_node_unlock(path, level);
 	return;
 err:
-	strcpy(buf2, "(none)");
-	strcpy(buf3, "(none)");
-
-	bch2_bpos_to_text(&PBUF(buf1), path->pos);
+	bch2_bpos_to_text(&buf1, path->pos);
 
 	if (p) {
 		struct bkey uk = bkey_unpack_key(l->b, p);
-		bch2_bkey_to_text(&PBUF(buf2), &uk);
+		bch2_bkey_to_text(&buf2, &uk);
+	} else {
+		pr_buf(&buf2, "(none)");
 	}
 
 	if (k) {
 		struct bkey uk = bkey_unpack_key(l->b, k);
-		bch2_bkey_to_text(&PBUF(buf3), &uk);
+		bch2_bkey_to_text(&buf3, &uk);
+	} else {
+		pr_buf(&buf3, "(none)");
 	}
 
 	panic("path should be %s key at level %u:\n"
 	      "path pos %s\n"
 	      "prev key %s\n"
 	      "cur  key %s\n",
-	      msg, level, buf1, buf2, buf3);
+	      msg, level, buf1.buf, buf2.buf, buf3.buf);
 }
 
 static void bch2_btree_path_verify(struct btree_trans *trans,
@@ -739,16 +742,16 @@ static int bch2_btree_iter_verify_ret(struct btree_iter *iter, struct bkey_s_c k
 	if (!bkey_cmp(prev.k->p, k.k->p) &&
 	    bch2_snapshot_is_ancestor(trans->c, iter->snapshot,
 				      prev.k->p.snapshot) > 0) {
-		char buf1[100], buf2[200];
+		struct printbuf buf1 = PRINTBUF, buf2 = PRINTBUF;
 
-		bch2_bkey_to_text(&PBUF(buf1), k.k);
-		bch2_bkey_to_text(&PBUF(buf2), prev.k);
+		bch2_bkey_to_text(&buf1, k.k);
+		bch2_bkey_to_text(&buf2, prev.k);
 
 		panic("iter snap %u\n"
 		      "k    %s\n"
 		      "prev %s\n",
 		      iter->snapshot,
-		      buf1, buf2);
+		      buf1.buf, buf2.buf);
 	}
 out:
 	bch2_trans_iter_exit(trans, &copy);
@@ -760,7 +763,7 @@ void bch2_assert_pos_locked(struct btree_trans *trans, enum btree_id id,
 {
 	struct btree_path *path;
 	unsigned idx;
-	char buf[100];
+	struct printbuf buf = PRINTBUF;
 
 	trans_for_each_path_inorder(trans, path, idx) {
 		int cmp = cmp_int(path->btree_id, id) ?:
@@ -786,9 +789,10 @@ void bch2_assert_pos_locked(struct btree_trans *trans, enum btree_id id,
 	}
 
 	bch2_dump_trans_paths_updates(trans);
+	bch2_bpos_to_text(&buf, pos);
+
 	panic("not locked: %s %s%s\n",
-	      bch2_btree_ids[id],
-	      (bch2_bpos_to_text(&PBUF(buf), pos), buf),
+	      bch2_btree_ids[id], buf.buf,
 	      key_cache ? " cached" : "");
 }
 
@@ -1071,23 +1075,23 @@ static void btree_path_verify_new_node(struct btree_trans *trans,
 	if (!k ||
 	    bkey_deleted(k) ||
 	    bkey_cmp_left_packed(l->b, k, &b->key.k.p)) {
-		char buf1[100];
-		char buf2[100];
-		char buf3[100];
-		char buf4[100];
+		struct printbuf buf1 = PRINTBUF;
+		struct printbuf buf2 = PRINTBUF;
+		struct printbuf buf3 = PRINTBUF;
+		struct printbuf buf4 = PRINTBUF;
 		struct bkey uk = bkey_unpack_key(b, k);
 
 		bch2_dump_btree_node(c, l->b);
-		bch2_bpos_to_text(&PBUF(buf1), path->pos);
-		bch2_bkey_to_text(&PBUF(buf2), &uk);
-		bch2_bpos_to_text(&PBUF(buf3), b->data->min_key);
-		bch2_bpos_to_text(&PBUF(buf3), b->data->max_key);
+		bch2_bpos_to_text(&buf1, path->pos);
+		bch2_bkey_to_text(&buf2, &uk);
+		bch2_bpos_to_text(&buf3, b->data->min_key);
+		bch2_bpos_to_text(&buf3, b->data->max_key);
 		panic("parent iter doesn't point to new node:\n"
 		      "iter pos %s %s\n"
 		      "iter key %s\n"
 		      "new node %s-%s\n",
-		      bch2_btree_ids[path->btree_id], buf1,
-		      buf2, buf3, buf4);
+		      bch2_btree_ids[path->btree_id],
+		      buf1.buf, buf2.buf, buf3.buf, buf4.buf);
 	}
 
 	if (!parent_locked)
@@ -1783,18 +1787,22 @@ void bch2_dump_trans_paths_updates(struct btree_trans *trans)
 {
 	struct btree_path *path;
 	struct btree_insert_entry *i;
+	struct printbuf buf1 = PRINTBUF, buf2 = PRINTBUF;
 	unsigned idx;
-	char buf1[300], buf2[300];
 
 	btree_trans_sort_paths(trans);
 
-	trans_for_each_path_inorder(trans, path, idx)
+	trans_for_each_path_inorder(trans, path, idx) {
+		printbuf_reset(&buf1);
+
+		bch2_bpos_to_text(&buf1, path->pos);
+
 		printk(KERN_ERR "path: idx %u ref %u:%u%s%s btree %s pos %s locks %u %pS\n",
 		       path->idx, path->ref, path->intent_ref,
 		       path->should_be_locked ? " S" : "",
 		       path->preserve ? " P" : "",
 		       bch2_btree_ids[path->btree_id],
-		       (bch2_bpos_to_text(&PBUF(buf1), path->pos), buf1),
+		       buf1.buf,
 		       path->nodes_locked,
 #ifdef CONFIG_BCACHEFS_DEBUG
 		       (void *) path->ip_allocated
@@ -1802,17 +1810,25 @@ void bch2_dump_trans_paths_updates(struct btree_trans *trans)
 		       NULL
 #endif
 		       );
+	}
 
 	trans_for_each_update(trans, i) {
 		struct bkey u;
 		struct bkey_s_c old = bch2_btree_path_peek_slot(i->path, &u);
 
+		printbuf_reset(&buf1);
+		printbuf_reset(&buf2);
+		bch2_bkey_val_to_text(&buf1, trans->c, old);
+		bch2_bkey_val_to_text(&buf2, trans->c, bkey_i_to_s_c(i->k));
+
 		printk(KERN_ERR "update: btree %s %pS\n  old %s\n  new %s",
 		       bch2_btree_ids[i->btree_id],
 		       (void *) i->ip_allocated,
-		       (bch2_bkey_val_to_text(&PBUF(buf1), trans->c, old), buf1),
-		       (bch2_bkey_val_to_text(&PBUF(buf2), trans->c, bkey_i_to_s_c(i->k)), buf2));
+		       buf1.buf, buf2.buf);
 	}
+
+	printbuf_exit(&buf2);
+	printbuf_exit(&buf1);
 }
 
 static struct btree_path *btree_path_alloc(struct btree_trans *trans,

fs/bcachefs/btree_update_interior.c

@@ -41,7 +41,7 @@ static void btree_node_interior_verify(struct bch_fs *c, struct btree *b)
 	struct bkey_s_c k;
 	struct bkey_s_c_btree_ptr_v2 bp;
 	struct bkey unpacked;
-	char buf1[100], buf2[100];
+	struct printbuf buf1 = PRINTBUF, buf2 = PRINTBUF;
 
 	BUG_ON(!b->c.level);
 
@@ -58,9 +58,9 @@ static void btree_node_interior_verify(struct bch_fs *c, struct btree *b)
 
 		if (bpos_cmp(next_node, bp.v->min_key)) {
 			bch2_dump_btree_node(c, b);
-			panic("expected next min_key %s got %s\n",
-			      (bch2_bpos_to_text(&PBUF(buf1), next_node), buf1),
-			      (bch2_bpos_to_text(&PBUF(buf2), bp.v->min_key), buf2));
+			bch2_bpos_to_text(&buf1, next_node);
+			bch2_bpos_to_text(&buf2, bp.v->min_key);
+			panic("expected next min_key %s got %s\n", buf1.buf, buf2.buf);
 		}
 
 		bch2_btree_node_iter_advance(&iter, b);
@@ -68,9 +68,9 @@ static void btree_node_interior_verify(struct bch_fs *c, struct btree *b)
 		if (bch2_btree_node_iter_end(&iter)) {
 			if (bpos_cmp(k.k->p, b->key.k.p)) {
 				bch2_dump_btree_node(c, b);
-				panic("expected end %s got %s\n",
-				      (bch2_bpos_to_text(&PBUF(buf1), b->key.k.p), buf1),
-				      (bch2_bpos_to_text(&PBUF(buf2), k.k->p), buf2));
+				bch2_bpos_to_text(&buf1, b->key.k.p);
+				bch2_bpos_to_text(&buf2, k.k->p);
+				panic("expected end %s got %s\n", buf1.buf, buf2.buf);
 			}
 			break;
 		}
@@ -1151,10 +1151,11 @@ static void bch2_insert_fixup_btree_ptr(struct btree_update *as,
 	invalid = bch2_bkey_invalid(c, bkey_i_to_s_c(insert), btree_node_type(b)) ?:
 		bch2_bkey_in_btree_node(b, bkey_i_to_s_c(insert));
 	if (invalid) {
-		char buf[160];
+		struct printbuf buf = PRINTBUF;
 
-		bch2_bkey_val_to_text(&PBUF(buf), c, bkey_i_to_s_c(insert));
-		bch2_fs_inconsistent(c, "inserting invalid bkey %s: %s", buf, invalid);
+		bch2_bkey_val_to_text(&buf, c, bkey_i_to_s_c(insert));
+		bch2_fs_inconsistent(c, "inserting invalid bkey %s: %s", buf.buf, invalid);
+		printbuf_exit(&buf);
 		dump_stack();
 	}
 
@@ -1636,15 +1637,17 @@ int __bch2_foreground_maybe_merge(struct btree_trans *trans,
 	}
 
 	if (bkey_cmp(bpos_successor(prev->data->max_key), next->data->min_key)) {
-		char buf1[100], buf2[100];
+		struct printbuf buf1 = PRINTBUF, buf2 = PRINTBUF;
 
-		bch2_bpos_to_text(&PBUF(buf1), prev->data->max_key);
-		bch2_bpos_to_text(&PBUF(buf2), next->data->min_key);
+		bch2_bpos_to_text(&buf1, prev->data->max_key);
+		bch2_bpos_to_text(&buf2, next->data->min_key);
 		bch_err(c,
 			"btree topology error in btree merge:\n"
 			"  prev ends at   %s\n"
 			"  next starts at %s",
-			buf1, buf2);
+			buf1.buf, buf2.buf);
+		printbuf_exit(&buf1);
+		printbuf_exit(&buf2);
 		bch2_topology_error(c);
 		ret = -EIO;
 		goto err;

fs/bcachefs/btree_update_leaf.c

@@ -831,11 +831,12 @@ static inline int do_bch2_trans_commit(struct btree_trans *trans,
 		const char *invalid = bch2_bkey_invalid(c,
 				bkey_i_to_s_c(i->k), i->bkey_type);
 		if (invalid) {
-			char buf[200];
+			struct printbuf buf = PRINTBUF;
 
-			bch2_bkey_val_to_text(&PBUF(buf), c, bkey_i_to_s_c(i->k));
+			bch2_bkey_val_to_text(&buf, c, bkey_i_to_s_c(i->k));
 			bch2_fs_fatal_error(c, "invalid bkey %s on insert from %s -> %ps: %s\n",
-					    buf, trans->fn, (void *) i->ip_allocated, invalid);
+					    buf.buf, trans->fn, (void *) i->ip_allocated, invalid);
+			printbuf_exit(&buf);
 			return -EINVAL;
 		}
 		btree_insert_entry_checks(trans, i);

fs/bcachefs/buckets.c

@@ -376,22 +376,23 @@ static inline int update_replicas(struct bch_fs *c, struct bkey_s_c k,
 {
 	struct bch_fs_usage __percpu *fs_usage;
 	int idx, ret = 0;
-	char buf[200];
+	struct printbuf buf = PRINTBUF;
 
 	percpu_down_read(&c->mark_lock);
+	buf.atomic++;
 
 	idx = bch2_replicas_entry_idx(c, r);
 	if (idx < 0 &&
 	    (test_bit(BCH_FS_REBUILD_REPLICAS, &c->flags) ||
 	     fsck_err(c, "no replicas entry\n"
 		      "  while marking %s",
-		      (bch2_bkey_val_to_text(&PBUF(buf), c, k), buf)))) {
+		      (bch2_bkey_val_to_text(&buf, c, k), buf.buf)))) {
 		percpu_up_read(&c->mark_lock);
 		ret = bch2_mark_replicas(c, r);
-		if (ret)
-			return ret;
-
 		percpu_down_read(&c->mark_lock);
+
+		if (ret)
+			goto err;
 		idx = bch2_replicas_entry_idx(c, r);
 	}
 	if (idx < 0) {
@@ -407,6 +408,7 @@ static inline int update_replicas(struct bch_fs *c, struct bkey_s_c k,
 err:
 fsck_err:
 	percpu_up_read(&c->mark_lock);
+	printbuf_exit(&buf);
 	return ret;
 }
 
@@ -678,7 +680,8 @@ static int check_bucket_ref(struct bch_fs *c,
 	u16 bucket_sectors = !ptr->cached
 		? dirty_sectors
 		: cached_sectors;
-	char buf[200];
+	struct printbuf buf = PRINTBUF;
+	int ret = 0;
 
 	if (gen_after(ptr->gen, b_gen)) {
 		bch2_fsck_err(c, FSCK_CAN_IGNORE|FSCK_NEED_FSCK,
@@ -687,8 +690,9 @@ static int check_bucket_ref(struct bch_fs *c,
 			ptr->dev, bucket_nr, b_gen,
 			bch2_data_types[bucket_data_type ?: ptr_data_type],
 			ptr->gen,
-			(bch2_bkey_val_to_text(&PBUF(buf), c, k), buf));
-		return -EIO;
+			(bch2_bkey_val_to_text(&buf, c, k), buf.buf));
+		ret = -EIO;
+		goto err;
 	}
 
 	if (gen_cmp(b_gen, ptr->gen) > BUCKET_GC_GEN_MAX) {
@@ -698,8 +702,10 @@ static int check_bucket_ref(struct bch_fs *c,
 			ptr->dev, bucket_nr, b_gen,
 			bch2_data_types[bucket_data_type ?: ptr_data_type],
 			ptr->gen,
-			(bch2_bkey_val_to_text(&PBUF(buf), c, k), buf));
-		return -EIO;
+			(printbuf_reset(&buf),
+			 bch2_bkey_val_to_text(&buf, c, k), buf.buf));
+		ret = -EIO;
+		goto err;
 	}
 
 	if (b_gen != ptr->gen && !ptr->cached) {
@@ -710,12 +716,16 @@ static int check_bucket_ref(struct bch_fs *c,
 			*bucket_gen(ca, bucket_nr),
 			bch2_data_types[bucket_data_type ?: ptr_data_type],
 			ptr->gen,
-			(bch2_bkey_val_to_text(&PBUF(buf), c, k), buf));
-		return -EIO;
+			(printbuf_reset(&buf),
+			 bch2_bkey_val_to_text(&buf, c, k), buf.buf));
+		ret = -EIO;
+		goto err;
 	}
 
-	if (b_gen != ptr->gen)
-		return 1;
+	if (b_gen != ptr->gen) {
+		ret = 1;
+		goto err;
+	}
 
 	if (bucket_data_type && ptr_data_type &&
 	    bucket_data_type != ptr_data_type) {
@@ -725,8 +735,10 @@ static int check_bucket_ref(struct bch_fs *c,
 			ptr->dev, bucket_nr, b_gen,
 			bch2_data_types[bucket_data_type],
 			bch2_data_types[ptr_data_type],
-			(bch2_bkey_val_to_text(&PBUF(buf), c, k), buf));
-		return -EIO;
+			(printbuf_reset(&buf),
+			 bch2_bkey_val_to_text(&buf, c, k), buf.buf));
+		ret = -EIO;
+		goto err;
 	}
 
 	if ((unsigned) (bucket_sectors + sectors) > U16_MAX) {
@@ -736,11 +748,14 @@ static int check_bucket_ref(struct bch_fs *c,
 			ptr->dev, bucket_nr, b_gen,
 			bch2_data_types[bucket_data_type ?: ptr_data_type],
 			bucket_sectors, sectors,
-			(bch2_bkey_val_to_text(&PBUF(buf), c, k), buf));
-		return -EIO;
+			(printbuf_reset(&buf),
+			 bch2_bkey_val_to_text(&buf, c, k), buf.buf));
+		ret = -EIO;
+		goto err;
 	}
-
-	return 0;
+err:
+	printbuf_exit(&buf);
+	return ret;
 }
 
 static int mark_stripe_bucket(struct btree_trans *trans,
@@ -759,7 +774,7 @@ static int mark_stripe_bucket(struct btree_trans *trans,
 	struct bch_dev *ca = bch_dev_bkey_exists(c, ptr->dev);
 	struct bucket *g;
 	struct bucket_mark new, old;
-	char buf[200];
+	struct printbuf buf = PRINTBUF;
 	int ret = 0;
 
 	BUG_ON(!(flags & BTREE_TRIGGER_GC));
@@ -767,6 +782,7 @@ static int mark_stripe_bucket(struct btree_trans *trans,
 	/* * XXX doesn't handle deletion */
 
 	percpu_down_read(&c->mark_lock);
+	buf.atomic++;
 	g = PTR_GC_BUCKET(ca, ptr);
 
 	if (g->mark.dirty_sectors ||
@@ -774,7 +790,7 @@ static int mark_stripe_bucket(struct btree_trans *trans,
 		bch2_fs_inconsistent(c,
 			      "bucket %u:%zu gen %u: multiple stripes using same bucket\n%s",
 			      ptr->dev, PTR_BUCKET_NR(ca, ptr), g->mark.gen,
-			      (bch2_bkey_val_to_text(&PBUF(buf), c, k), buf));
+			      (bch2_bkey_val_to_text(&buf, c, k), buf.buf));
 		ret = -EINVAL;
 		goto err;
 	}
@@ -799,8 +815,8 @@ static int mark_stripe_bucket(struct btree_trans *trans,
 	bch2_dev_usage_update(c, ca, old, new, journal_seq, true);
 err:
 	percpu_up_read(&c->mark_lock);
-
-	return 0;
+	printbuf_exit(&buf);
+	return ret;
 }
 
 static int __mark_pointer(struct btree_trans *trans,
@@ -987,10 +1003,11 @@ static int bch2_mark_extent(struct btree_trans *trans,
 	if (r.e.nr_devs) {
 		ret = update_replicas(c, k, &r.e, dirty_sectors, journal_seq, true);
 		if (ret) {
-			char buf[200];
+			struct printbuf buf = PRINTBUF;
 
-			bch2_bkey_val_to_text(&PBUF(buf), c, k);
-			bch2_fs_fatal_error(c, "no replicas entry for %s", buf);
+			bch2_bkey_val_to_text(&buf, c, k);
+			bch2_fs_fatal_error(c, "no replicas entry for %s", buf.buf);
+			printbuf_exit(&buf);
 			return ret;
 		}
 	}
@@ -1019,13 +1036,16 @@ static int bch2_mark_stripe(struct btree_trans *trans,
 		struct stripe *m = genradix_ptr(&c->stripes, idx);
 
 		if (!m || (old_s && !m->alive)) {
-			char buf1[200], buf2[200];
+			struct printbuf buf1 = PRINTBUF;
+			struct printbuf buf2 = PRINTBUF;
 
-			bch2_bkey_val_to_text(&PBUF(buf1), c, old);
-			bch2_bkey_val_to_text(&PBUF(buf2), c, new);
+			bch2_bkey_val_to_text(&buf1, c, old);
+			bch2_bkey_val_to_text(&buf2, c, new);
 			bch_err_ratelimited(c, "error marking nonexistent stripe %llu while marking\n"
 					    "old %s\n"
-					    "new %s", idx, buf1, buf2);
+					    "new %s", idx, buf1.buf, buf2.buf);
+			printbuf_exit(&buf2);
+			printbuf_exit(&buf1);
 			bch2_inconsistent_error(c);
 			return -1;
 		}
@@ -1090,10 +1110,11 @@ static int bch2_mark_stripe(struct btree_trans *trans,
 				      ((s64) m->sectors * m->nr_redundant),
 				      journal_seq, gc);
 		if (ret) {
-			char buf[200];
+			struct printbuf buf = PRINTBUF;
 
-			bch2_bkey_val_to_text(&PBUF(buf), c, new);
-			bch2_fs_fatal_error(c, "no replicas entry for %s", buf);
+			bch2_bkey_val_to_text(&buf, c, new);
+			bch2_fs_fatal_error(c, "no replicas entry for %s", buf.buf);
+			printbuf_exit(&buf);
 			return ret;
 		}
 	}
@@ -1174,7 +1195,7 @@ static s64 __bch2_mark_reflink_p(struct btree_trans *trans,
 	int add = !(flags & BTREE_TRIGGER_OVERWRITE) ? 1 : -1;
 	u64 next_idx = end;
 	s64 ret = 0;
-	char buf[200];
+	struct printbuf buf = PRINTBUF;
 
 	if (r_idx >= c->reflink_gc_nr)
 		goto not_found;
@@ -1193,7 +1214,7 @@ static s64 __bch2_mark_reflink_p(struct btree_trans *trans,
 	if (fsck_err(c, "pointer to missing indirect extent\n"
 		     "  %s\n"
 		     "  missing range %llu-%llu",
-		     (bch2_bkey_val_to_text(&PBUF(buf), c, p.s_c), buf),
+		     (bch2_bkey_val_to_text(&buf, c, p.s_c), buf.buf),
 		     *idx, next_idx)) {
 		struct bkey_i_error new;
 
@@ -1207,6 +1228,7 @@ static s64 __bch2_mark_reflink_p(struct btree_trans *trans,
 
 	*idx = next_idx;
 fsck_err:
+	printbuf_exit(&buf);
 	return ret;
 }
 
@@ -1289,7 +1311,7 @@ void fs_usage_apply_warn(struct btree_trans *trans,
 {
 	struct bch_fs *c = trans->c;
 	struct btree_insert_entry *i;
-	char buf[200];
+	struct printbuf buf = PRINTBUF;
 
 	bch_err(c, "disk usage increased %lli more than %u sectors reserved",
 		should_not_have_added, disk_res_sectors);
@@ -1298,13 +1320,17 @@ void fs_usage_apply_warn(struct btree_trans *trans,
 		struct bkey_s_c old = { &i->old_k, i->old_v };
 
 		pr_err("while inserting");
-		bch2_bkey_val_to_text(&PBUF(buf), c, bkey_i_to_s_c(i->k));
-		pr_err("  %s", buf);
+		printbuf_reset(&buf);
+		bch2_bkey_val_to_text(&buf, c, bkey_i_to_s_c(i->k));
+		pr_err("  %s", buf.buf);
 		pr_err("overlapping with");
-		bch2_bkey_val_to_text(&PBUF(buf), c, old);
-		pr_err("  %s", buf);
+		printbuf_reset(&buf);
+		bch2_bkey_val_to_text(&buf, c, old);
+		pr_err("  %s", buf.buf);
 	}
+
 	__WARN();
+	printbuf_exit(&buf);
 }
 
 int bch2_trans_fs_usage_apply(struct btree_trans *trans,
@@ -1744,7 +1770,7 @@ static int __bch2_trans_mark_reflink_p(struct btree_trans *trans,
 	struct bkey_i *n;
 	__le64 *refcount;
 	int add = !(flags & BTREE_TRIGGER_OVERWRITE) ? 1 : -1;
-	char buf[200];
+	struct printbuf buf = PRINTBUF;
 	int ret;
 
 	bch2_trans_iter_init(trans, &iter, BTREE_ID_reflink, POS(0, *idx),
@@ -1764,19 +1790,19 @@ static int __bch2_trans_mark_reflink_p(struct btree_trans *trans,
 
 	refcount = bkey_refcount(n);
 	if (!refcount) {
-		bch2_bkey_val_to_text(&PBUF(buf), c, p.s_c);
+		bch2_bkey_val_to_text(&buf, c, p.s_c);
 		bch2_fs_inconsistent(c,
 			"nonexistent indirect extent at %llu while marking\n  %s",
-			*idx, buf);
+			*idx, buf.buf);
 		ret = -EIO;
 		goto err;
 	}
 
 	if (!*refcount && (flags & BTREE_TRIGGER_OVERWRITE)) {
-		bch2_bkey_val_to_text(&PBUF(buf), c, p.s_c);
+		bch2_bkey_val_to_text(&buf, c, p.s_c);
 		bch2_fs_inconsistent(c,
 			"indirect extent refcount underflow at %llu while marking\n  %s",
-			*idx, buf);
+			*idx, buf.buf);
 		ret = -EIO;
 		goto err;
 	}
@@ -1811,6 +1837,7 @@ static int __bch2_trans_mark_reflink_p(struct btree_trans *trans,
 	*idx = k.k->p.offset;
 err:
 	bch2_trans_iter_exit(trans, &iter);
+	printbuf_exit(&buf);
 	return ret;
 }
 

fs/bcachefs/clock.c

@@ -157,6 +157,7 @@ void bch2_io_timers_to_text(struct printbuf *out, struct io_clock *clock)
 	unsigned long now;
 	unsigned i;
 
+	out->atomic++;
 	spin_lock(&clock->timer_lock);
 	now = atomic64_read(&clock->now);
 
@@ -165,6 +166,7 @@ void bch2_io_timers_to_text(struct printbuf *out, struct io_clock *clock)
 		       clock->timers.data[i]->fn,
 		       clock->timers.data[i]->expire - now);
 	spin_unlock(&clock->timer_lock);
+	--out->atomic;
 }
 
 void bch2_io_clock_exit(struct io_clock *clock)

fs/bcachefs/debug.c

@@ -169,10 +169,11 @@ void __bch2_btree_verify(struct bch_fs *c, struct btree *b)
 		failed |= bch2_btree_verify_replica(c, b, p);
 
 	if (failed) {
-		char buf[200];
+		struct printbuf buf = PRINTBUF;
 
-		bch2_bkey_val_to_text(&PBUF(buf), c, bkey_i_to_s_c(&b->key));
-		bch2_fs_fatal_error(c, "btree node verify failed for : %s\n", buf);
+		bch2_bkey_val_to_text(&buf, c, bkey_i_to_s_c(&b->key));
+		bch2_fs_fatal_error(c, "btree node verify failed for : %s\n", buf.buf);
+		printbuf_exit(&buf);
 	}
 out:
 	mutex_unlock(&c->verify_lock);
@@ -188,8 +189,7 @@ struct dump_iter {
 	struct bch_fs	*c;
 	enum btree_id		id;
 
-	char			buf[1 << 12];
-	size_t			bytes;	/* what's currently in buf */
+	struct printbuf		buf;
 
 	char __user		*ubuf;	/* destination user buffer */
 	size_t			size;	/* size of requested read */
@@ -198,9 +198,9 @@ struct dump_iter {
 
 static int flush_buf(struct dump_iter *i)
 {
-	if (i->bytes) {
-		size_t bytes = min(i->bytes, i->size);
-		int err = copy_to_user(i->ubuf, i->buf, bytes);
+	if (i->buf.pos) {
+		size_t bytes = min_t(size_t, i->buf.pos, i->size);
+		int err = copy_to_user(i->ubuf, i->buf.buf, bytes);
 
 		if (err)
 			return err;
@@ -208,8 +208,8 @@ static int flush_buf(struct dump_iter *i)
 		i->ret	 += bytes;
 		i->ubuf	 += bytes;
 		i->size	 -= bytes;
-		i->bytes -= bytes;
-		memmove(i->buf, i->buf + bytes, i->bytes);
+		i->buf.pos -= bytes;
+		memmove(i->buf.buf, i->buf.buf + bytes, i->buf.pos);
 	}
 
 	return 0;
@@ -228,13 +228,17 @@ static int bch2_dump_open(struct inode *inode, struct file *file)
 	i->from = POS_MIN;
 	i->c	= container_of(bd, struct bch_fs, btree_debug[bd->id]);
 	i->id	= bd->id;
+	i->buf	= PRINTBUF;
 
 	return 0;
 }
 
 static int bch2_dump_release(struct inode *inode, struct file *file)
 {
-	kfree(file->private_data);
+	struct dump_iter *i = file->private_data;
+
+	printbuf_exit(&i->buf);
+	kfree(i);
 	return 0;
 }
 
@@ -266,11 +270,8 @@ static ssize_t bch2_read_btree(struct file *file, char __user *buf,
 	k = bch2_btree_iter_peek(&iter);
 
 	while (k.k && !(err = bkey_err(k))) {
-		bch2_bkey_val_to_text(&PBUF(i->buf), i->c, k);
-		i->bytes = strlen(i->buf);
-		BUG_ON(i->bytes >= sizeof(i->buf));
-		i->buf[i->bytes] = '\n';
-		i->bytes++;
+		bch2_bkey_val_to_text(&i->buf, i->c, k);
+		pr_char(&i->buf, '\n');
 
 		k = bch2_btree_iter_next(&iter);
 		i->from = iter.pos;
@@ -319,8 +320,7 @@ static ssize_t bch2_read_btree_formats(struct file *file, char __user *buf,
 	bch2_trans_init(&trans, i->c, 0, 0);
 
 	for_each_btree_node(&trans, iter, i->id, i->from, 0, b, err) {
-		bch2_btree_node_to_text(&PBUF(i->buf), i->c, b);
-		i->bytes = strlen(i->buf);
+		bch2_btree_node_to_text(&i->buf, i->c, b);
 		err = flush_buf(i);
 		if (err)
 			break;
@@ -384,16 +384,14 @@ static ssize_t bch2_read_bfloat_failed(struct file *file, char __user *buf,
 			bch2_btree_node_iter_peek(&l->iter, l->b);
 
 		if (l->b != prev_node) {
-			bch2_btree_node_to_text(&PBUF(i->buf), i->c, l->b);
-			i->bytes = strlen(i->buf);
+			bch2_btree_node_to_text(&i->buf, i->c, l->b);
 			err = flush_buf(i);
 			if (err)
 				break;
 		}
 		prev_node = l->b;
 
-		bch2_bfloat_to_text(&PBUF(i->buf), l->b, _k);
-		i->bytes = strlen(i->buf);
+		bch2_bfloat_to_text(&i->buf, l->b, _k);
 		err = flush_buf(i);
 		if (err)
 			break;

fs/bcachefs/ec.c

@@ -286,14 +286,15 @@ static void ec_validate_checksums(struct bch_fs *c, struct ec_stripe_buf *buf)
 			struct bch_csum got = ec_block_checksum(buf, i, offset);
 
 			if (bch2_crc_cmp(want, got)) {
-				char buf2[200];
+				struct printbuf buf2 = PRINTBUF;
 
-				bch2_bkey_val_to_text(&PBUF(buf2), c, bkey_i_to_s_c(&buf->key.k_i));
+				bch2_bkey_val_to_text(&buf2, c, bkey_i_to_s_c(&buf->key.k_i));
 
 				bch_err_ratelimited(c,
 					"stripe checksum error for %ps at %u:%u: csum type %u, expected %llx got %llx\n%s",
 					(void *) _RET_IP_, i, j, v->csum_type,
-					want.lo, got.lo, buf2);
+					want.lo, got.lo, buf2.buf);
+				printbuf_exit(&buf2);
 				clear_bit(i, buf->valid);
 				break;
 			}

fs/bcachefs/fs.c

@@ -1676,7 +1676,8 @@ static int bch2_show_options(struct seq_file *seq, struct dentry *root)
 {
 	struct bch_fs *c = root->d_sb->s_fs_info;
 	enum bch_opt_id i;
-	char buf[512];
+	struct printbuf buf = PRINTBUF;
+	int ret = 0;
 
 	for (i = 0; i < bch2_opts_nr; i++) {
 		const struct bch_option *opt = &bch2_opt_table[i];
@@ -1688,13 +1689,17 @@ static int bch2_show_options(struct seq_file *seq, struct dentry *root)
 		if (v == bch2_opt_get_by_id(&bch2_opts_default, i))
 			continue;
 
-		bch2_opt_to_text(&PBUF(buf), c, opt, v,
+		printbuf_reset(&buf);
+		bch2_opt_to_text(&buf, c, opt, v,
 				 OPT_SHOW_MOUNT_STYLE);
 		seq_putc(seq, ',');
-		seq_puts(seq, buf);
+		seq_puts(seq, buf.buf);
 	}
 
-	return 0;
+	if (buf.allocation_failure)
+		ret = -ENOMEM;
+	printbuf_exit(&buf);
+	return ret;
 }
 
 static void bch2_put_super(struct super_block *sb)

fs/bcachefs/io.c

@@ -2057,11 +2057,11 @@ static noinline void read_from_stale_dirty_pointer(struct btree_trans *trans,
 	struct bch_fs *c = trans->c;
 	struct bch_dev *ca = bch_dev_bkey_exists(c, ptr.dev);
 	struct btree_iter iter;
-	char buf[200];
+	struct printbuf buf = PRINTBUF;
 	int ret;
 
-	bch2_bkey_val_to_text(&PBUF(buf), c, k);
-	bch2_fs_inconsistent(c, "Attempting to read from stale dirty pointer: %s", buf);
+	bch2_bkey_val_to_text(&buf, c, k);
+	bch2_fs_inconsistent(c, "Attempting to read from stale dirty pointer: %s", buf.buf);
 
 	bch2_trans_iter_init(trans, &iter, BTREE_ID_alloc,
 			     POS(ptr.dev, PTR_BUCKET_NR(ca, &ptr)),
@@ -2069,12 +2069,14 @@ static noinline void read_from_stale_dirty_pointer(struct btree_trans *trans,
 
 	ret = lockrestart_do(trans, bkey_err(k = bch2_btree_iter_peek_slot(&iter)));
 	if (ret)
-		return;
+		goto out;
 
-	bch2_bkey_val_to_text(&PBUF(buf), c, k);
-	bch_err(c, "%s", buf);
+	bch2_bkey_val_to_text(&buf, c, k);
+	bch_err(c, "%s", buf.buf);
 	bch_err(c, "memory gen: %u", *bucket_gen(ca, iter.pos.offset));
 	bch2_trans_iter_exit(trans, &iter);
+out:
+	printbuf_exit(&buf);
 }
 
 int __bch2_read_extent(struct btree_trans *trans, struct bch_read_bio *orig,

fs/bcachefs/journal.c

@@ -414,18 +414,18 @@ static int __journal_res_get(struct journal *j, struct journal_res *res,
 	    !can_discard &&
 	    j->reservations.idx == j->reservations.unwritten_idx &&
 	    (flags & JOURNAL_RES_GET_RESERVED)) {
-		char *journal_debug_buf = kmalloc(4096, GFP_ATOMIC);
+		struct printbuf buf = PRINTBUF;
 
 		bch_err(c, "Journal stuck! Hava a pre-reservation but journal full");
-		if (journal_debug_buf) {
-			bch2_journal_debug_to_text(&_PBUF(journal_debug_buf, 4096), j);
-			bch_err(c, "%s", journal_debug_buf);
 
-			bch2_journal_pins_to_text(&_PBUF(journal_debug_buf, 4096), j);
-			bch_err(c, "Journal pins:\n%s", journal_debug_buf);
-			kfree(journal_debug_buf);
-		}
+		bch2_journal_debug_to_text(&buf, j);
+		bch_err(c, "%s", buf.buf);
+
+		printbuf_reset(&buf);
+		bch2_journal_pins_to_text(&buf, j);
+		bch_err(c, "Journal pins:\n%s", buf.buf);
 
+		printbuf_exit(&buf);
 		bch2_fatal_error(c);
 		dump_stack();
 	}
@@ -1186,6 +1186,8 @@ void __bch2_journal_debug_to_text(struct printbuf *out, struct journal *j)
 	unsigned long now = jiffies;
 	unsigned i;
 
+	out->atomic++;
+
 	rcu_read_lock();
 	s = READ_ONCE(j->reservations);
 
@@ -1270,6 +1272,8 @@ void __bch2_journal_debug_to_text(struct printbuf *out, struct journal *j)
 	}
 
 	rcu_read_unlock();
+
+	--out->atomic;
 }
 
 void bch2_journal_debug_to_text(struct printbuf *out, struct journal *j)
@@ -1286,6 +1290,8 @@ void bch2_journal_pins_to_text(struct printbuf *out, struct journal *j)
 	u64 i;
 
 	spin_lock(&j->lock);
+	out->atomic++;
+
 	fifo_for_each_entry_ptr(pin_list, &j->pin, i) {
 		pr_buf(out, "%llu: count %u\n",
 		       i, atomic_read(&pin_list->count));
@@ -1305,5 +1311,7 @@ void bch2_journal_pins_to_text(struct printbuf *out, struct journal *j)
 			pr_buf(out, "\t%px %ps\n",
 			       pin, pin->flush);
 	}
+
+	--out->atomic;
 	spin_unlock(&j->lock);
 }

fs/bcachefs/journal_io.c

@@ -251,14 +251,15 @@ static int journal_validate_key(struct bch_fs *c, const char *where,
 	invalid = bch2_bkey_invalid(c, bkey_i_to_s_c(k),
 				    __btree_node_type(level, btree_id));
 	if (invalid) {
-		char buf[160];
+		struct printbuf buf = PRINTBUF;
 
-		bch2_bkey_val_to_text(&PBUF(buf), c, bkey_i_to_s_c(k));
+		bch2_bkey_val_to_text(&buf, c, bkey_i_to_s_c(k));
 		mustfix_fsck_err(c, "invalid %s in %s entry offset %zi/%u: %s\n%s",
 				 type, where,
 				 (u64 *) k - entry->_data,
 				 le16_to_cpu(entry->u64s),
-				 invalid, buf);
+				 invalid, buf.buf);
+		printbuf_exit(&buf);
 
 		le16_add_cpu(&entry->u64s, -((u16) k->k.u64s));
 		memmove(k, bkey_next(k), next - (void *) bkey_next(k));
@@ -995,6 +996,7 @@ int bch2_journal_read(struct bch_fs *c, struct list_head *list,
 	struct journal_replay *i, *t;
 	struct bch_dev *ca;
 	unsigned iter;
+	struct printbuf buf = PRINTBUF;
 	size_t keys = 0, entries = 0;
 	bool degraded = false;
 	u64 seq, last_seq = 0;
@@ -1053,7 +1055,8 @@ int bch2_journal_read(struct bch_fs *c, struct list_head *list,
 
 	if (!last_seq) {
 		fsck_err(c, "journal read done, but no entries found after dropping non-flushes");
-		return -1;
+		ret = -1;
+		goto err;
 	}
 
 	/* Drop blacklisted entries and entries older than last_seq: */
@@ -1085,7 +1088,7 @@ int bch2_journal_read(struct bch_fs *c, struct list_head *list,
 
 		while (seq < le64_to_cpu(i->j.seq)) {
 			u64 missing_start, missing_end;
-			char buf1[200], buf2[200];
+			struct printbuf buf1 = PRINTBUF, buf2 = PRINTBUF;
 
 			while (seq < le64_to_cpu(i->j.seq) &&
 			       bch2_journal_seq_is_blacklisted(c, seq, false))
@@ -1101,14 +1104,13 @@ int bch2_journal_read(struct bch_fs *c, struct list_head *list,
 				seq++;
 
 			if (i->list.prev != list) {
-				struct printbuf out = PBUF(buf1);
 				struct journal_replay *p = list_prev_entry(i, list);
 
-				bch2_journal_ptrs_to_text(&out, c, p);
-				pr_buf(&out, " size %zu", vstruct_sectors(&p->j, c->block_bits));
+				bch2_journal_ptrs_to_text(&buf1, c, p);
+				pr_buf(&buf1, " size %zu", vstruct_sectors(&p->j, c->block_bits));
 			} else
-				sprintf(buf1, "(none)");
-			bch2_journal_ptrs_to_text(&PBUF(buf2), c, i);
+				pr_buf(&buf1, "(none)");
+			bch2_journal_ptrs_to_text(&buf2, c, i);
 
 			missing_end = seq - 1;
 			fsck_err(c, "journal entries %llu-%llu missing! (replaying %llu-%llu)\n"
@@ -1116,7 +1118,10 @@ int bch2_journal_read(struct bch_fs *c, struct list_head *list,
 				 "  next at %s",
 				 missing_start, missing_end,
 				 last_seq, *blacklist_seq - 1,
-				 buf1, buf2);
+				 buf1.buf, buf2.buf);
+
+			printbuf_exit(&buf1);
+			printbuf_exit(&buf2);
 		}
 
 		seq++;
@@ -1130,14 +1135,13 @@ int bch2_journal_read(struct bch_fs *c, struct list_head *list,
 			.e.nr_required = 1,
 		};
 		unsigned ptr;
-		char buf[80];
 
 		if (i->ignore)
 			continue;
 
 		ret = jset_validate_entries(c, &i->j, READ);
 		if (ret)
-			goto fsck_err;
+			goto err;
 
 		for (ptr = 0; ptr < i->nr_ptrs; ptr++)
 			replicas.e.devs[replicas.e.nr_devs++] = i->ptrs[ptr].dev;
@@ -1149,15 +1153,17 @@ int bch2_journal_read(struct bch_fs *c, struct list_head *list,
 		 * the devices - this is wrong:
 		 */
 
+		printbuf_reset(&buf);
+		bch2_replicas_entry_to_text(&buf, &replicas.e);
+
 		if (!degraded &&
 		    (test_bit(BCH_FS_REBUILD_REPLICAS, &c->flags) ||
 		     fsck_err_on(!bch2_replicas_marked(c, &replicas.e), c,
 				 "superblock not marked as containing replicas %s",
-				 (bch2_replicas_entry_to_text(&PBUF(buf),
-							      &replicas.e), buf)))) {
+				 buf.buf))) {
 			ret = bch2_mark_replicas(c, &replicas.e);
 			if (ret)
-				return ret;
+				goto err;
 		}
 
 		for_each_jset_key(k, _n, entry, &i->j)
@@ -1171,7 +1177,9 @@ int bch2_journal_read(struct bch_fs *c, struct list_head *list,
 	if (*start_seq != *blacklist_seq)
 		bch_info(c, "dropped unflushed entries %llu-%llu",
 			 *blacklist_seq, *start_seq - 1);
+err:
 fsck_err:
+	printbuf_exit(&buf);
 	return ret;
 }
 
@@ -1481,7 +1489,7 @@ void bch2_journal_write(struct closure *cl)
 	struct jset_entry *start, *end;
 	struct jset *jset;
 	struct bio *bio;
-	char *journal_debug_buf = NULL;
+	struct printbuf journal_debug_buf = PRINTBUF;
 	bool validate_before_checksum = false;
 	unsigned i, sectors, bytes, u64s, nr_rw_members = 0;
 	int ret;
@@ -1586,11 +1594,8 @@ void bch2_journal_write(struct closure *cl)
 		goto retry_alloc;
 	}
 
-	if (ret) {
-		journal_debug_buf = kmalloc(4096, GFP_ATOMIC);
-		if (journal_debug_buf)
-			__bch2_journal_debug_to_text(&_PBUF(journal_debug_buf, 4096), j);
-	}
+	if (ret)
+		__bch2_journal_debug_to_text(&journal_debug_buf, j);
 
 	/*
 	 * write is allocated, no longer need to account for it in
@@ -1607,8 +1612,8 @@ void bch2_journal_write(struct closure *cl)
 
 	if (ret) {
 		bch_err(c, "Unable to allocate journal write:\n%s",
-			journal_debug_buf);
-		kfree(journal_debug_buf);
+			journal_debug_buf.buf);
+		printbuf_exit(&journal_debug_buf);
 		bch2_fatal_error(c);
 		continue_at(cl, journal_write_done, c->io_complete_wq);
 		return;

fs/bcachefs/journal_reclaim.c

@@ -216,14 +216,11 @@ void bch2_journal_space_available(struct journal *j)
 	if (!clean_ondisk &&
 	    j->reservations.idx ==
 	    j->reservations.unwritten_idx) {
-		char *buf = kmalloc(4096, GFP_ATOMIC);
+		struct printbuf buf = PRINTBUF;
 
-		bch_err(c, "journal stuck");
-		if (buf) {
-			__bch2_journal_debug_to_text(&_PBUF(buf, 4096), j);
-			pr_err("\n%s", buf);
-			kfree(buf);
-		}
+		__bch2_journal_debug_to_text(&buf, j);
+		bch_err(c, "journal stuck\n%s", buf.buf);
+		printbuf_exit(&buf);
 
 		bch2_fatal_error(c);
 		ret = cur_entry_journal_stuck;

fs/bcachefs/rebalance.c

@@ -257,35 +257,47 @@ void bch2_rebalance_work_to_text(struct printbuf *out, struct bch_fs *c)
 {
 	struct bch_fs_rebalance *r = &c->rebalance;
 	struct rebalance_work w = rebalance_work(c);
-	char h1[21], h2[21];
 
-	bch2_hprint(&PBUF(h1), w.dev_most_full_work << 9);
-	bch2_hprint(&PBUF(h2), w.dev_most_full_capacity << 9);
-	pr_buf(out, "fullest_dev (%i):\t%s/%s\n",
-	       w.dev_most_full_idx, h1, h2);
+	out->tabstops[0] = 20;
 
-	bch2_hprint(&PBUF(h1), w.total_work << 9);
-	bch2_hprint(&PBUF(h2), c->capacity << 9);
-	pr_buf(out, "total work:\t\t%s/%s\n", h1, h2);
+	pr_buf(out, "fullest_dev (%i):", w.dev_most_full_idx);
+	pr_tab(out);
 
-	pr_buf(out, "rate:\t\t\t%u\n", r->pd.rate.rate);
+	bch2_hprint(out, w.dev_most_full_work << 9);
+	pr_buf(out, "/");
+	bch2_hprint(out, w.dev_most_full_capacity << 9);
+	pr_newline(out);
+
+	pr_buf(out, "total work:");
+	pr_tab(out);
+
+	bch2_hprint(out, w.total_work << 9);
+	pr_buf(out, "/");
+	bch2_hprint(out, c->capacity << 9);
+	pr_newline(out);
+
+	pr_buf(out, "rate:");
+	pr_tab(out);
+	pr_buf(out, "%u", r->pd.rate.rate);
+	pr_newline(out);
 
 	switch (r->state) {
 	case REBALANCE_WAITING:
-		pr_buf(out, "waiting\n");
+		pr_buf(out, "waiting");
 		break;
 	case REBALANCE_THROTTLED:
-		bch2_hprint(&PBUF(h1),
+		pr_buf(out, "throttled for %lu sec or ",
+		       (r->throttled_until_cputime - jiffies) / HZ);
+		bch2_hprint(out,
 			    (r->throttled_until_iotime -
 			     atomic64_read(&c->io_clock[WRITE].now)) << 9);
-		pr_buf(out, "throttled for %lu sec or %s io\n",
-		       (r->throttled_until_cputime - jiffies) / HZ,
-		       h1);
+		pr_buf(out, " io");
 		break;
 	case REBALANCE_RUNNING:
-		pr_buf(out, "running\n");
+		pr_buf(out, "running");
 		break;
 	}
+	pr_newline(out);
 }
 
 void bch2_rebalance_stop(struct bch_fs *c)

fs/bcachefs/recovery.c

@@ -760,6 +760,8 @@ static int verify_superblock_clean(struct bch_fs *c,
 {
 	unsigned i;
 	struct bch_sb_field_clean *clean = *cleanp;
+	struct printbuf buf1 = PRINTBUF;
+	struct printbuf buf2 = PRINTBUF;
 	int ret = 0;
 
 	if (mustfix_fsck_err_on(j->seq != clean->journal_seq, c,
@@ -772,7 +774,6 @@ static int verify_superblock_clean(struct bch_fs *c,
 	}
 
 	for (i = 0; i < BTREE_ID_NR; i++) {
-		char buf1[200], buf2[200];
 		struct bkey_i *k1, *k2;
 		unsigned l1 = 0, l2 = 0;
 
@@ -782,6 +783,19 @@ static int verify_superblock_clean(struct bch_fs *c,
 		if (!k1 && !k2)
 			continue;
 
+		printbuf_reset(&buf1);
+		printbuf_reset(&buf2);
+
+		if (k1)
+			bch2_bkey_val_to_text(&buf1, c, bkey_i_to_s_c(k1));
+		else
+			pr_buf(&buf1, "(none)");
+
+		if (k2)
+			bch2_bkey_val_to_text(&buf2, c, bkey_i_to_s_c(k2));
+		else
+			pr_buf(&buf2, "(none)");
+
 		mustfix_fsck_err_on(!k1 || !k2 ||
 				    IS_ERR(k1) ||
 				    IS_ERR(k2) ||
@@ -791,10 +805,12 @@ static int verify_superblock_clean(struct bch_fs *c,
 			"superblock btree root %u doesn't match journal after clean shutdown\n"
 			"sb:      l=%u %s\n"
 			"journal: l=%u %s\n", i,
-			l1, (bch2_bkey_val_to_text(&PBUF(buf1), c, bkey_i_to_s_c(k1)), buf1),
-			l2, (bch2_bkey_val_to_text(&PBUF(buf2), c, bkey_i_to_s_c(k2)), buf2));
+			l1, buf1.buf,
+			l2, buf2.buf);
 	}
 fsck_err:
+	printbuf_exit(&buf2);
+	printbuf_exit(&buf1);
 	return ret;
 }
 

fs/bcachefs/replicas.c

@@ -997,11 +997,12 @@ bool bch2_have_enough_devs(struct bch_fs *c, struct bch_devs_mask devs,
 
 		if (dflags & ~flags) {
 			if (print) {
-				char buf[100];
+				struct printbuf buf = PRINTBUF;
 
-				bch2_replicas_entry_to_text(&PBUF(buf), e);
+				bch2_replicas_entry_to_text(&buf, e);
 				bch_err(c, "insufficient devices online (%u) for replicas entry %s",
-					nr_online, buf);
+					nr_online, buf.buf);
+				printbuf_exit(&buf);
 			}
 			ret = false;
 			break;

fs/bcachefs/super-io.c

@@ -572,16 +572,10 @@ int bch2_read_super(const char *path, struct bch_opts *opts,
 {
 	u64 offset = opt_get(*opts, sb);
 	struct bch_sb_layout layout;
-	char *_err;
-	struct printbuf err;
+	struct printbuf err = PRINTBUF;
 	__le64 *i;
 	int ret;
 
-	_err = kmalloc(4096, GFP_KERNEL);
-	if (!_err)
-		return -ENOMEM;
-	err = _PBUF(_err, 4096);
-
 	pr_verbose_init(*opts, "");
 
 	memset(sb, 0, sizeof(*sb));
@@ -633,8 +627,8 @@ int bch2_read_super(const char *path, struct bch_opts *opts,
 		goto err;
 
 	printk(KERN_ERR "bcachefs (%s): error reading default superblock: %s",
-	       path, _err);
-	err = _PBUF(_err, 4096);
+	       path, err.buf);
+	printbuf_reset(&err);
 
 	/*
 	 * Error reading primary superblock - read location of backup
@@ -689,16 +683,16 @@ int bch2_read_super(const char *path, struct bch_opts *opts,
 	ret = bch2_sb_validate(sb, &err);
 	if (ret) {
 		printk(KERN_ERR "bcachefs (%s): error validating superblock: %s",
-		       path, _err);
+		       path, err.buf);
 		goto err_no_print;
 	}
 out:
 	pr_verbose_init(*opts, "ret %i", ret);
-	kfree(_err);
+	printbuf_exit(&err);
 	return ret;
 err:
 	printk(KERN_ERR "bcachefs (%s): error reading superblock: %s",
-	       path, _err);
+	       path, err.buf);
 err_no_print:
 	bch2_free_super(sb);
 	goto out;
@@ -768,6 +762,7 @@ int bch2_write_super(struct bch_fs *c)
 {
 	struct closure *cl = &c->sb_write;
 	struct bch_dev *ca;
+	struct printbuf err = PRINTBUF;
 	unsigned i, sb = 0, nr_wrote;
 	struct bch_devs_mask sb_written;
 	bool wrote, can_mount_without_written, can_mount_with_written;
@@ -795,18 +790,11 @@ int bch2_write_super(struct bch_fs *c)
 		bch2_sb_from_fs(c, ca);
 
 	for_each_online_member(ca, c, i) {
-		struct printbuf buf = { NULL, NULL };
+		printbuf_reset(&err);
 
-		ret = bch2_sb_validate(&ca->disk_sb, &buf);
+		ret = bch2_sb_validate(&ca->disk_sb, &err);
 		if (ret) {
-			char *_buf = kmalloc(4096, GFP_NOFS);
-			if (_buf) {
-				buf = _PBUF(_buf, 4096);
-				bch2_sb_validate(&ca->disk_sb, &buf);
-			}
-
-			bch2_fs_inconsistent(c, "sb invalid before write: %s", _buf);
-			kfree(_buf);
+			bch2_fs_inconsistent(c, "sb invalid before write: %s", err.buf);
 			percpu_ref_put(&ca->io_ref);
 			goto out;
 		}
@@ -897,6 +885,7 @@ int bch2_write_super(struct bch_fs *c)
 out:
 	/* Make new options visible after they're persistent: */
 	bch2_sb_update(c);
+	printbuf_exit(&err);
 	return ret;
 }
 

fs/bcachefs/super.c

@@ -870,12 +870,9 @@ noinline_for_stack
 static void print_mount_opts(struct bch_fs *c)
 {
 	enum bch_opt_id i;
-	char buf[512];
-	struct printbuf p = PBUF(buf);
+	struct printbuf p = PRINTBUF;
 	bool first = true;
 
-	strcpy(buf, "(null)");
-
 	if (c->opts.read_only) {
 		pr_buf(&p, "ro");
 		first = false;
@@ -897,7 +894,11 @@ static void print_mount_opts(struct bch_fs *c)
 		bch2_opt_to_text(&p, c, opt, v, OPT_SHOW_MOUNT_STYLE);
 	}
 
-	bch_info(c, "mounted with opts: %s", buf);
+	if (!p.pos)
+		pr_buf(&p, "(null)");
+
+	bch_info(c, "mounted with opts: %s", p.buf);
+	printbuf_exit(&p);
 }
 
 int bch2_fs_start(struct bch_fs *c)
@@ -1561,11 +1562,11 @@ int bch2_dev_remove(struct bch_fs *c, struct bch_dev *ca, int flags)
 
 	data = bch2_dev_has_data(c, ca);
 	if (data) {
-		char data_has_str[100];
+		struct printbuf data_has = PRINTBUF;
 
-		bch2_flags_to_text(&PBUF(data_has_str),
-				   bch2_data_types, data);
-		bch_err(ca, "Remove failed, still has data (%s)", data_has_str);
+		bch2_flags_to_text(&data_has, bch2_data_types, data);
+		bch_err(ca, "Remove failed, still has data (%s)", data_has.buf);
+		printbuf_exit(&data_has);
 		ret = -EBUSY;
 		goto err;
 	}
@@ -1614,16 +1615,9 @@ int bch2_dev_add(struct bch_fs *c, const char *path)
 	struct bch_sb_field_members *mi;
 	struct bch_member dev_mi;
 	unsigned dev_idx, nr_devices, u64s;
-	char *_errbuf;
-	struct printbuf errbuf;
+	struct printbuf errbuf = PRINTBUF;
 	int ret;
 
-	_errbuf = kmalloc(4096, GFP_KERNEL);
-	if (!_errbuf)
-		return -ENOMEM;
-
-	errbuf = _PBUF(_errbuf, 4096);
-
 	ret = bch2_read_super(path, &opts, &sb);
 	if (ret) {
 		bch_err(c, "device add error: error reading super: %i", ret);
@@ -1741,7 +1735,7 @@ int bch2_dev_add(struct bch_fs *c, const char *path)
 	if (ca)
 		bch2_dev_free(ca);
 	bch2_free_super(&sb);
-	kfree(_errbuf);
+	printbuf_exit(&errbuf);
 	return ret;
 err_late:
 	up_write(&c->state_lock);
@@ -1906,8 +1900,7 @@ struct bch_fs *bch2_fs_open(char * const *devices, unsigned nr_devices,
 	struct bch_sb_field_members *mi;
 	unsigned i, best_sb = 0;
 	const char *err;
-	char *_errbuf = NULL;
-	struct printbuf errbuf;
+	struct printbuf errbuf = PRINTBUF;
 	int ret = 0;
 
 	if (!try_module_get(THIS_MODULE))
@@ -1920,14 +1913,6 @@ struct bch_fs *bch2_fs_open(char * const *devices, unsigned nr_devices,
 		goto err;
 	}
 
-	_errbuf = kmalloc(4096, GFP_KERNEL);
-	if (!_errbuf) {
-		ret = -ENOMEM;
-		goto err;
-	}
-
-	errbuf = _PBUF(_errbuf, 4096);
-
 	sb = kcalloc(nr_devices, sizeof(*sb), GFP_KERNEL);
 	if (!sb) {
 		ret = -ENOMEM;
@@ -1991,7 +1976,7 @@ struct bch_fs *bch2_fs_open(char * const *devices, unsigned nr_devices,
 	}
 out:
 	kfree(sb);
-	kfree(_errbuf);
+	printbuf_exit(&errbuf);
 	module_put(THIS_MODULE);
 	pr_verbose_init(opts, "ret %i", PTR_ERR_OR_ZERO(c));
 	return c;

fs/bcachefs/sysfs.c

@@ -46,8 +46,28 @@ struct sysfs_ops type ## _sysfs_ops = {					\
 }
 
 #define SHOW(fn)							\
+static ssize_t fn ## _to_text(struct printbuf *,			\
+			      struct kobject *, struct attribute *);\
+									\
 static ssize_t fn ## _show(struct kobject *kobj, struct attribute *attr,\
 			   char *buf)					\
+{									\
+	struct printbuf out = PRINTBUF;					\
+	ssize_t ret = fn ## _to_text(&out, kobj, attr);			\
+									\
+	if (!ret && out.allocation_failure)				\
+		ret = -ENOMEM;						\
+									\
+	if (!ret) {							\
+		ret = min_t(size_t, out.pos, PAGE_SIZE - 1);		\
+		memcpy(buf, out.buf, ret);				\
+	}								\
+	printbuf_exit(&out);						\
+	return ret;							\
+}									\
+									\
+static ssize_t fn ## _to_text(struct printbuf *out, struct kobject *kobj,\
+			      struct attribute *attr)
 
 #define STORE(fn)							\
 static ssize_t fn ## _store(struct kobject *kobj, struct attribute *attr,\
@@ -64,22 +84,19 @@ static ssize_t fn ## _store(struct kobject *kobj, struct attribute *attr,\
 #define sysfs_printf(file, fmt, ...)					\
 do {									\
 	if (attr == &sysfs_ ## file)					\
-		return scnprintf(buf, PAGE_SIZE, fmt "\n", __VA_ARGS__);\
+		pr_buf(out, fmt "\n", __VA_ARGS__);			\
 } while (0)
 
 #define sysfs_print(file, var)						\
 do {									\
 	if (attr == &sysfs_ ## file)					\
-		return snprint(buf, PAGE_SIZE, var);			\
+		snprint(out, var);					\
 } while (0)
 
 #define sysfs_hprint(file, val)						\
 do {									\
-	if (attr == &sysfs_ ## file) {					\
-		bch2_hprint(&out, val);					\
-		pr_buf(&out, "\n");					\
-		return out.pos - buf;					\
-	}								\
+	if (attr == &sysfs_ ## file)					\
+		bch2_hprint(out, val);					\
 } while (0)
 
 #define var_printf(_var, fmt)	sysfs_printf(_var, fmt, var(_var))
@@ -348,7 +365,6 @@ static void bch2_gc_gens_pos_to_text(struct printbuf *out, struct bch_fs *c)
 SHOW(bch2_fs)
 {
 	struct bch_fs *c = container_of(kobj, struct bch_fs, kobj);
-	struct printbuf out = _PBUF(buf, PAGE_SIZE);
 
 	sysfs_print(minor,			c->minor);
 	sysfs_printf(internal_uuid, "%pU",	c->sb.uuid.b);
@@ -365,10 +381,8 @@ SHOW(bch2_fs)
 
 	sysfs_printf(btree_gc_periodic, "%u",	(int) c->btree_gc_periodic);
 
-	if (attr == &sysfs_gc_gens_pos) {
-		bch2_gc_gens_pos_to_text(&out, c);
-		return out.pos - buf;
-	}
+	if (attr == &sysfs_gc_gens_pos)
+		bch2_gc_gens_pos_to_text(out, c);
 
 	sysfs_printf(copy_gc_enabled, "%i", c->copy_gc_enabled);
 
@@ -378,83 +392,54 @@ SHOW(bch2_fs)
 		     max(0LL, c->copygc_wait -
 			 atomic64_read(&c->io_clock[WRITE].now)) << 9);
 
-	if (attr == &sysfs_rebalance_work) {
-		bch2_rebalance_work_to_text(&out, c);
-		return out.pos - buf;
-	}
+	if (attr == &sysfs_rebalance_work)
+		bch2_rebalance_work_to_text(out, c);
 
 	sysfs_print(promote_whole_extents,	c->promote_whole_extents);
 
 	/* Debugging: */
 
-	if (attr == &sysfs_journal_debug) {
-		bch2_journal_debug_to_text(&out, &c->journal);
-		return out.pos - buf;
-	}
+	if (attr == &sysfs_journal_debug)
+		bch2_journal_debug_to_text(out, &c->journal);
 
-	if (attr == &sysfs_journal_pins) {
-		bch2_journal_pins_to_text(&out, &c->journal);
-		return out.pos - buf;
-	}
+	if (attr == &sysfs_journal_pins)
+		bch2_journal_pins_to_text(out, &c->journal);
 
-	if (attr == &sysfs_btree_updates) {
-		bch2_btree_updates_to_text(&out, c);
-		return out.pos - buf;
-	}
+	if (attr == &sysfs_btree_updates)
+		bch2_btree_updates_to_text(out, c);
 
-	if (attr == &sysfs_dirty_btree_nodes) {
-		bch2_dirty_btree_nodes_to_text(&out, c);
-		return out.pos - buf;
-	}
+	if (attr == &sysfs_dirty_btree_nodes)
+		bch2_dirty_btree_nodes_to_text(out, c);
 
-	if (attr == &sysfs_btree_cache) {
-		bch2_btree_cache_to_text(&out, c);
-		return out.pos - buf;
-	}
+	if (attr == &sysfs_btree_cache)
+		bch2_btree_cache_to_text(out, c);
 
-	if (attr == &sysfs_btree_key_cache) {
-		bch2_btree_key_cache_to_text(&out, &c->btree_key_cache);
-		return out.pos - buf;
-	}
+	if (attr == &sysfs_btree_key_cache)
+		bch2_btree_key_cache_to_text(out, &c->btree_key_cache);
 
-	if (attr == &sysfs_btree_transactions) {
-		bch2_btree_trans_to_text(&out, c);
-		return out.pos - buf;
-	}
+	if (attr == &sysfs_btree_transactions)
+		bch2_btree_trans_to_text(out, c);
 
-	if (attr == &sysfs_stripes_heap) {
-		bch2_stripes_heap_to_text(&out, c);
-		return out.pos - buf;
-	}
+	if (attr == &sysfs_stripes_heap)
+		bch2_stripes_heap_to_text(out, c);
 
-	if (attr == &sysfs_open_buckets) {
-		bch2_open_buckets_to_text(&out, c);
-		return out.pos - buf;
-	}
+	if (attr == &sysfs_open_buckets)
+		bch2_open_buckets_to_text(out, c);
 
-	if (attr == &sysfs_compression_stats) {
-		bch2_compression_stats_to_text(&out, c);
-		return out.pos - buf;
-	}
+	if (attr == &sysfs_compression_stats)
+		bch2_compression_stats_to_text(out, c);
 
-	if (attr == &sysfs_new_stripes) {
-		bch2_new_stripes_to_text(&out, c);
-		return out.pos - buf;
-	}
+	if (attr == &sysfs_new_stripes)
+		bch2_new_stripes_to_text(out, c);
 
-	if (attr == &sysfs_io_timers_read) {
-		bch2_io_timers_to_text(&out, &c->io_clock[READ]);
-		return out.pos - buf;
-	}
-	if (attr == &sysfs_io_timers_write) {
-		bch2_io_timers_to_text(&out, &c->io_clock[WRITE]);
-		return out.pos - buf;
-	}
+	if (attr == &sysfs_io_timers_read)
+		bch2_io_timers_to_text(out, &c->io_clock[READ]);
 
-	if (attr == &sysfs_data_jobs) {
-		data_progress_to_text(&out, c);
-		return out.pos - buf;
-	}
+	if (attr == &sysfs_io_timers_write)
+		bch2_io_timers_to_text(out, &c->io_clock[WRITE]);
+
+	if (attr == &sysfs_data_jobs)
+		data_progress_to_text(out, c);
 
 	return 0;
 }
@@ -567,7 +552,7 @@ struct attribute *bch2_fs_files[] = {
 SHOW(bch2_fs_internal)
 {
 	struct bch_fs *c = container_of(kobj, struct bch_fs, internal);
-	return bch2_fs_show(&c->kobj, attr, buf);
+	return bch2_fs_to_text(out, &c->kobj, attr);
 }
 
 STORE(bch2_fs_internal)
@@ -617,16 +602,15 @@ struct attribute *bch2_fs_internal_files[] = {
 
 SHOW(bch2_fs_opts_dir)
 {
-	struct printbuf out = _PBUF(buf, PAGE_SIZE);
 	struct bch_fs *c = container_of(kobj, struct bch_fs, opts_dir);
 	const struct bch_option *opt = container_of(attr, struct bch_option, attr);
 	int id = opt - bch2_opt_table;
 	u64 v = bch2_opt_get_by_id(&c->opts, id);
 
-	bch2_opt_to_text(&out, c, opt, v, OPT_SHOW_FULL_LIST);
-	pr_buf(&out, "\n");
+	bch2_opt_to_text(out, c, opt, v, OPT_SHOW_FULL_LIST);
+	pr_char(out, '\n');
 
-	return out.pos - buf;
+	return 0;
 }
 
 STORE(bch2_fs_opts_dir)
@@ -690,13 +674,10 @@ int bch2_opts_create_sysfs_files(struct kobject *kobj)
 SHOW(bch2_fs_time_stats)
 {
 	struct bch_fs *c = container_of(kobj, struct bch_fs, time_stats);
-	struct printbuf out = _PBUF(buf, PAGE_SIZE);
 
 #define x(name)								\
-	if (attr == &sysfs_time_stat_##name) {				\
-		bch2_time_stats_to_text(&out, &c->times[BCH_TIME_##name]);\
-		return out.pos - buf;					\
-	}
+	if (attr == &sysfs_time_stat_##name)				\
+		bch2_time_stats_to_text(out, &c->times[BCH_TIME_##name]);
 	BCH_TIME_STATS()
 #undef x
 
@@ -812,7 +793,6 @@ SHOW(bch2_dev)
 {
 	struct bch_dev *ca = container_of(kobj, struct bch_dev, kobj);
 	struct bch_fs *c = ca->fs;
-	struct printbuf out = _PBUF(buf, PAGE_SIZE);
 
 	sysfs_printf(uuid,		"%pU\n", ca->uuid.b);
 
@@ -825,58 +805,47 @@ SHOW(bch2_dev)
 	if (attr == &sysfs_label) {
 		if (ca->mi.group) {
 			mutex_lock(&c->sb_lock);
-			bch2_disk_path_to_text(&out, c->disk_sb.sb,
+			bch2_disk_path_to_text(out, c->disk_sb.sb,
 					       ca->mi.group - 1);
 			mutex_unlock(&c->sb_lock);
 		}
 
-		pr_buf(&out, "\n");
-		return out.pos - buf;
+		pr_char(out, '\n');
 	}
 
 	if (attr == &sysfs_has_data) {
-		bch2_flags_to_text(&out, bch2_data_types,
+		bch2_flags_to_text(out, bch2_data_types,
 				   bch2_dev_has_data(c, ca));
-		pr_buf(&out, "\n");
-		return out.pos - buf;
+		pr_char(out, '\n');
 	}
 
 	if (attr == &sysfs_state_rw) {
-		bch2_string_opt_to_text(&out, bch2_member_states,
+		bch2_string_opt_to_text(out, bch2_member_states,
 					ca->mi.state);
-		pr_buf(&out, "\n");
-		return out.pos - buf;
+		pr_char(out, '\n');
 	}
 
-	if (attr == &sysfs_iodone) {
-		dev_iodone_to_text(&out, ca);
-		return out.pos - buf;
-	}
+	if (attr == &sysfs_iodone)
+		dev_iodone_to_text(out, ca);
 
 	sysfs_print(io_latency_read,		atomic64_read(&ca->cur_latency[READ]));
 	sysfs_print(io_latency_write,		atomic64_read(&ca->cur_latency[WRITE]));
 
-	if (attr == &sysfs_io_latency_stats_read) {
-		bch2_time_stats_to_text(&out, &ca->io_latency[READ]);
-		return out.pos - buf;
-	}
-	if (attr == &sysfs_io_latency_stats_write) {
-		bch2_time_stats_to_text(&out, &ca->io_latency[WRITE]);
-		return out.pos - buf;
-	}
+	if (attr == &sysfs_io_latency_stats_read)
+		bch2_time_stats_to_text(out, &ca->io_latency[READ]);
+
+	if (attr == &sysfs_io_latency_stats_write)
+		bch2_time_stats_to_text(out, &ca->io_latency[WRITE]);
 
 	sysfs_printf(congested,			"%u%%",
 		     clamp(atomic_read(&ca->congested), 0, CONGESTED_MAX)
 		     * 100 / CONGESTED_MAX);
 
-	if (attr == &sysfs_reserve_stats) {
-		reserve_stats_to_text(&out, ca);
-		return out.pos - buf;
-	}
-	if (attr == &sysfs_alloc_debug) {
-		dev_alloc_debug_to_text(&out, ca);
-		return out.pos - buf;
-	}
+	if (attr == &sysfs_reserve_stats)
+		reserve_stats_to_text(out, ca);
+
+	if (attr == &sysfs_alloc_debug)
+		dev_alloc_debug_to_text(out, ca);
 
 	return 0;
 }

fs/bcachefs/tests.c

@@ -871,7 +871,9 @@ int bch2_btree_perf_test(struct bch_fs *c, const char *testname,
 			 u64 nr, unsigned nr_threads)
 {
 	struct test_job j = { .c = c, .nr = nr, .nr_threads = nr_threads };
-	char name_buf[20], nr_buf[20], per_sec_buf[20];
+	char name_buf[20];
+	struct printbuf nr_buf = PRINTBUF;
+	struct printbuf per_sec_buf = PRINTBUF;
 	unsigned i;
 	u64 time;
 
@@ -932,13 +934,15 @@ int bch2_btree_perf_test(struct bch_fs *c, const char *testname,
 	time = j.finish - j.start;
 
 	scnprintf(name_buf, sizeof(name_buf), "%s:", testname);
-	bch2_hprint(&PBUF(nr_buf), nr);
-	bch2_hprint(&PBUF(per_sec_buf), div64_u64(nr * NSEC_PER_SEC, time));
+	bch2_hprint(&nr_buf, nr);
+	bch2_hprint(&per_sec_buf, div64_u64(nr * NSEC_PER_SEC, time));
 	printk(KERN_INFO "%-12s %s with %u threads in %5llu sec, %5llu nsec per iter, %5s per sec\n",
-		name_buf, nr_buf, nr_threads,
+		name_buf, nr_buf.buf, nr_threads,
 		div_u64(time, NSEC_PER_SEC),
 		div_u64(time * nr_threads, nr),
-		per_sec_buf);
+		per_sec_buf.buf);
+	printbuf_exit(&per_sec_buf);
+	printbuf_exit(&nr_buf);
 	return j.ret;
 }
 

fs/bcachefs/util.c

@@ -99,6 +99,38 @@ STRTO_H(strtoll, long long)
 STRTO_H(strtoull, unsigned long long)
 STRTO_H(strtou64, u64)
 
+static int bch2_printbuf_realloc(struct printbuf *out, unsigned extra)
+{
+	unsigned new_size = roundup_pow_of_two(out->size + extra);
+	char *buf = krealloc(out->buf, new_size, !out->atomic ? GFP_KERNEL : GFP_ATOMIC);
+
+	if (!buf) {
+		out->allocation_failure = true;
+		return -ENOMEM;
+	}
+
+	out->buf	= buf;
+	out->size	= new_size;
+	return 0;
+}
+
+void bch2_pr_buf(struct printbuf *out, const char *fmt, ...)
+{
+	va_list args;
+	int len;
+
+	do {
+		va_start(args, fmt);
+		len = vsnprintf(out->buf + out->pos, printbuf_remaining(out), fmt, args);
+		va_end(args);
+	} while (len + 1 >= printbuf_remaining(out) &&
+		 !bch2_printbuf_realloc(out, len + 1));
+
+	len = min_t(size_t, len,
+		  printbuf_remaining(out) ? printbuf_remaining(out) - 1 : 0);
+	out->pos += len;
+}
+
 void bch2_hprint(struct printbuf *buf, s64 v)
 {
 	int u, t = 0;
@@ -151,9 +183,6 @@ void bch2_flags_to_text(struct printbuf *out,
 	unsigned bit, nr = 0;
 	bool first = true;
 
-	if (out->pos != out->end)
-		*out->pos = '\0';
-
 	while (list[nr])
 		nr++;
 

fs/bcachefs/util.h

@@ -242,19 +242,39 @@ enum printbuf_units {
 };
 
 struct printbuf {
-	char			*pos;
-	char			*end;
-	char			*last_newline;
-	char			*last_field;
+	char			*buf;
+	unsigned		size;
+	unsigned		pos;
+	unsigned		last_newline;
+	unsigned		last_field;
 	unsigned		indent;
-	enum printbuf_units	units;
-	unsigned		tabstop;
-	unsigned		tabstops[4];
+	enum printbuf_units	units:8;
+	u8			atomic;
+	bool			allocation_failure:1;
+	u8			tabstop;
+	u8			tabstops[4];
 };
 
+#define PRINTBUF ((struct printbuf) { NULL })
+
+static inline void printbuf_exit(struct printbuf *buf)
+{
+	kfree(buf->buf);
+	buf->buf = ERR_PTR(-EINTR); /* poison value */
+}
+
+static inline void printbuf_reset(struct printbuf *buf)
+{
+	buf->pos		= 0;
+	buf->last_newline	= 0;
+	buf->last_field		= 0;
+	buf->indent		= 0;
+	buf->tabstop		= 0;
+}
+
 static inline size_t printbuf_remaining(struct printbuf *buf)
 {
-	return buf->end - buf->pos;
+	return buf->size - buf->pos;
 }
 
 static inline size_t printbuf_linelen(struct printbuf *buf)
@@ -262,29 +282,13 @@ static inline size_t printbuf_linelen(struct printbuf *buf)
 	return buf->pos - buf->last_newline;
 }
 
-#define _PBUF(_buf, _len)						\
-	((struct printbuf) {						\
-		.pos		= _buf,					\
-		.end		= _buf + _len,				\
-		.last_newline	= _buf,					\
-		.last_field	= _buf,					\
-	})
+void bch2_pr_buf(struct printbuf *out, const char *fmt, ...);
 
-#define PBUF(_buf) _PBUF(_buf, sizeof(_buf))
-
-
-#define pr_buf(_out, ...)						\
-do {									\
-	(_out)->pos += scnprintf((_out)->pos, printbuf_remaining(_out),	\
-				 __VA_ARGS__);				\
-} while (0)
+#define pr_buf(_out, ...) bch2_pr_buf(_out, __VA_ARGS__)
 
 static inline void pr_char(struct printbuf *out, char c)
 {
-	if (printbuf_remaining(out) > 1) {
-		*out->pos = c;
-		out->pos++;
-	}
+	bch2_pr_buf(out, "%c", c);
 }
 
 static inline void pr_indent_push(struct printbuf *buf, unsigned spaces)
@@ -298,7 +302,7 @@ static inline void pr_indent_pop(struct printbuf *buf, unsigned spaces)
 {
 	if (buf->last_newline + buf->indent == buf->pos) {
 		buf->pos -= spaces;
-		buf->pos = '\0';
+		buf->buf[buf->pos] = '\0';
 	}
 	buf->indent -= spaces;
 }
@@ -341,12 +345,12 @@ static inline void pr_tab_rjust(struct printbuf *buf)
 	BUG_ON(buf->tabstop > ARRAY_SIZE(buf->tabstops));
 
 	if (shift > 0) {
-		memmove(buf->last_field + shift,
-			buf->last_field,
+		memmove(buf->buf + buf->last_field + shift,
+			buf->buf + buf->last_field,
 			move);
-		memset(buf->last_field, ' ', shift);
+		memset(buf->buf + buf->last_field, ' ', shift);
 		buf->pos += shift;
-		*buf->pos = 0;
+		buf->buf[buf->pos] = 0;
 	}
 
 	buf->last_field = buf->pos;
@@ -460,8 +464,8 @@ static inline int bch2_strtoul_h(const char *cp, long *res)
 	_r;								\
 })
 
-#define snprint(buf, size, var)						\
-	snprintf(buf, size,						\
+#define snprint(out, var)						\
+	pr_buf(out,							\
 		   type_is(var, int)		? "%i\n"		\
 		 : type_is(var, unsigned)	? "%u\n"		\
 		 : type_is(var, long)		? "%li\n"		\
@@ -605,10 +609,8 @@ do {									\
 	sysfs_print(name##_rate_d_term,		(var)->d_term);		\
 	sysfs_print(name##_rate_p_term_inverse,	(var)->p_term_inverse);	\
 									\
-	if (attr == &sysfs_##name##_rate_debug) {			\
-		bch2_pd_controller_debug_to_text(&out, var);		\
-		return out.pos - buf;					\
-	}								\
+	if (attr == &sysfs_##name##_rate_debug)				\
+		bch2_pd_controller_debug_to_text(out, var);		\
 } while (0)
 
 #define sysfs_pd_controller_store(name, var)				\

fs/bcachefs/xattr.c

@@ -426,9 +426,8 @@ static int __bch2_xattr_bcachefs_get(const struct xattr_handler *handler,
 		bch2_inode_opts_to_opts(bch2_inode_opts_get(&inode->ei_inode));
 	const struct bch_option *opt;
 	int id, inode_opt_id;
-	char buf[512];
-	struct printbuf out = PBUF(buf);
-	unsigned val_len;
+	struct printbuf out = PRINTBUF;
+	int ret;
 	u64 v;
 
 	id = bch2_opt_lookup(name);
@@ -451,14 +450,19 @@ static int __bch2_xattr_bcachefs_get(const struct xattr_handler *handler,
 	v = bch2_opt_get_by_id(&opts, id);
 	bch2_opt_to_text(&out, c, opt, v, 0);
 
-	val_len = out.pos - buf;
+	ret = out.pos;
 
-	if (buffer && val_len > size)
-		return -ERANGE;
+	if (out.allocation_failure) {
+		ret = -ENOMEM;
+	} else if (buffer) {
+		if (out.pos > size)
+			ret = -ERANGE;
+		else
+			memcpy(buffer, out.buf, out.pos);
+	}
 
-	if (buffer)
-		memcpy(buffer, buf, val_len);
-	return val_len;
+	printbuf_exit(&out);
+	return ret;
 }
 
 static int bch2_xattr_bcachefs_get(const struct xattr_handler *handler,