bcachefs: Convert bch2_gc_done() for_each_btree_key2()

This converts bch2_gc_stripes_done() and bch2_gc_reflink_done() to the
new for_each_btree_key_commit() macro.

The new for_each_btree_key2() and for_each_btree_key_commit() macros
handles transaction retries, allowing us to avoid nested transactions -
which we want to avoid since they're tricky to do completely correctly
and upcoming assertions are going to be checking for that.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

fs/bcachefs/btree_gc.c

@@ -1321,21 +1321,19 @@ static inline bool bch2_alloc_v4_cmp(struct bch_alloc_v4 l,
 
 static int bch2_alloc_write_key(struct btree_trans *trans,
 				struct btree_iter *iter,
+				struct bkey_s_c k,
 				bool metadata_only)
 {
 	struct bch_fs *c = trans->c;
 	struct bch_dev *ca = bch_dev_bkey_exists(c, iter->pos.inode);
 	struct bucket gc, *b;
-	struct bkey_s_c k;
 	struct bkey_i_alloc_v4 *a;
 	struct bch_alloc_v4 old, new;
 	enum bch_data_type type;
 	int ret;
 
-	k = bch2_btree_iter_peek_slot(iter);
-	ret = bkey_err(k);
-	if (ret)
-		return ret;
+	if (bkey_cmp(iter->pos, POS(ca->dev_idx, ca->mi.nbuckets)) >= 0)
+		return 1;
 
 	bch2_alloc_to_v4(k, &old);
 	new = old;
@@ -1428,23 +1426,13 @@ static int bch2_gc_alloc_done(struct bch_fs *c, bool metadata_only)
 	bch2_trans_init(&trans, c, 0, 0);
 
 	for_each_member_device(ca, c, i) {
-		for_each_btree_key(&trans, iter, BTREE_ID_alloc,
-				   POS(ca->dev_idx, ca->mi.first_bucket),
-				   BTREE_ITER_SLOTS|
-				   BTREE_ITER_PREFETCH, k, ret) {
-			if (bkey_cmp(iter.pos, POS(ca->dev_idx, ca->mi.nbuckets)) >= 0)
-				break;
+		ret = for_each_btree_key_commit(&trans, iter, BTREE_ID_alloc,
+				POS(ca->dev_idx, ca->mi.first_bucket),
+				BTREE_ITER_SLOTS|BTREE_ITER_PREFETCH, k,
+				NULL, NULL, BTREE_INSERT_LAZY_RW,
+			bch2_alloc_write_key(&trans, &iter, k, metadata_only));
 
-			ret = commit_do(&trans, NULL, NULL,
-					      BTREE_INSERT_LAZY_RW,
-					bch2_alloc_write_key(&trans, &iter,
-							     metadata_only));
-			if (ret)
-				break;
-		}
-		bch2_trans_iter_exit(&trans, &iter);
-
-		if (ret) {
+		if (ret < 0) {
 			bch_err(c, "error writing alloc info: %i", ret);
 			percpu_ref_put(&ca->ref);
 			break;
@@ -1452,7 +1440,7 @@ static int bch2_gc_alloc_done(struct bch_fs *c, bool metadata_only)
 	}
 
 	bch2_trans_exit(&trans);
-	return ret;
+	return ret < 0 ? ret : 0;
 }
 
 static int bch2_gc_alloc_start(struct bch_fs *c, bool metadata_only)
@@ -1536,72 +1524,79 @@ static void bch2_gc_alloc_reset(struct bch_fs *c, bool metadata_only)
 	};
 }
 
-static int bch2_gc_reflink_done(struct bch_fs *c, bool metadata_only)
+static int bch2_gc_write_reflink_key(struct btree_trans *trans,
+				     struct btree_iter *iter,
+				     struct bkey_s_c k,
+				     size_t *idx)
 {
-	struct btree_trans trans;
-	struct btree_iter iter;
-	struct bkey_s_c k;
-	struct reflink_gc *r;
-	size_t idx = 0;
+	struct bch_fs *c = trans->c;
+	const __le64 *refcount = bkey_refcount_c(k);
 	struct printbuf buf = PRINTBUF;
+	struct reflink_gc *r;
 	int ret = 0;
 
-	if (metadata_only)
+	if (!refcount)
 		return 0;
 
-	bch2_trans_init(&trans, c, 0, 0);
+	while ((r = genradix_ptr(&c->reflink_gc_table, *idx)) &&
+	       r->offset < k.k->p.offset)
+		++*idx;
 
-	for_each_btree_key(&trans, iter, BTREE_ID_reflink, POS_MIN,
-			   BTREE_ITER_PREFETCH, k, ret) {
-		const __le64 *refcount = bkey_refcount_c(k);
+	if (!r ||
+	    r->offset != k.k->p.offset ||
+	    r->size != k.k->size) {
+		bch_err(c, "unexpected inconsistency walking reflink table at gc finish");
+		return -EINVAL;
+	}
 
-		if (!refcount)
-			continue;
+	if (fsck_err_on(r->refcount != le64_to_cpu(*refcount), c,
+			"reflink key has wrong refcount:\n"
+			"  %s\n"
+			"  should be %u",
+			(bch2_bkey_val_to_text(&buf, c, k), buf.buf),
+			r->refcount)) {
+		struct bkey_i *new;
 
-		r = genradix_ptr(&c->reflink_gc_table, idx++);
-		if (!r ||
-		    r->offset != k.k->p.offset ||
-		    r->size != k.k->size) {
-			bch_err(c, "unexpected inconsistency walking reflink table at gc finish");
-			ret = -EINVAL;
-			break;
-		}
+		new = bch2_trans_kmalloc(trans, bkey_bytes(k.k));
+		ret = PTR_ERR_OR_ZERO(new);
+		if (ret)
+			return ret;
 
-		if (fsck_err_on(r->refcount != le64_to_cpu(*refcount), c,
-				"reflink key has wrong refcount:\n"
-				"  %s\n"
-				"  should be %u",
-				(printbuf_reset(&buf),
-				 bch2_bkey_val_to_text(&buf, c, k), buf.buf),
-				r->refcount)) {
-			struct bkey_i *new;
+		bkey_reassemble(new, k);
 
-			new = kmalloc(bkey_bytes(k.k), GFP_KERNEL);
-			if (!new) {
-				ret = -ENOMEM;
-				break;
-			}
+		if (!r->refcount)
+			new->k.type = KEY_TYPE_deleted;
+		else
+			*bkey_refcount(new) = cpu_to_le64(r->refcount);
 
-			bkey_reassemble(new, k);
+		ret = bch2_trans_update(trans, iter, new, 0);
+	}
+fsck_err:
+	printbuf_exit(&buf);
+	return ret;
+}
 
-			if (!r->refcount)
-				new->k.type = KEY_TYPE_deleted;
-			else
-				*bkey_refcount(new) = cpu_to_le64(r->refcount);
+static int bch2_gc_reflink_done(struct bch_fs *c, bool metadata_only)
+{
+	struct btree_trans trans;
+	struct btree_iter iter;
+	struct bkey_s_c k;
+	size_t idx = 0;
+	int ret = 0;
 
-			ret = commit_do(&trans, NULL, NULL, 0,
-				__bch2_btree_insert(&trans, BTREE_ID_reflink, new));
-			kfree(new);
+	if (metadata_only)
+		return 0;
+
+	bch2_trans_init(&trans, c, 0, 0);
+
+	ret = for_each_btree_key_commit(&trans, iter,
+			BTREE_ID_reflink, POS_MIN,
+			BTREE_ITER_PREFETCH, k,
+			NULL, NULL, BTREE_INSERT_NOFAIL,
+		bch2_gc_write_reflink_key(&trans, &iter, k, &idx));
 
-			if (ret)
-				break;
-		}
-	}
-fsck_err:
-	bch2_trans_iter_exit(&trans, &iter);
 	c->reflink_gc_nr = 0;
 	bch2_trans_exit(&trans);
-	printbuf_exit(&buf);
 	return ret;
 }
 
@@ -1653,66 +1648,73 @@ static void bch2_gc_reflink_reset(struct bch_fs *c, bool metadata_only)
 		r->refcount = 0;
 }
 
-static int bch2_gc_stripes_done(struct bch_fs *c, bool metadata_only)
+static int bch2_gc_write_stripes_key(struct btree_trans *trans,
+				     struct btree_iter *iter,
+				     struct bkey_s_c k)
 {
-	struct btree_trans trans;
-	struct btree_iter iter;
-	struct bkey_s_c k;
-	struct gc_stripe *m;
-	const struct bch_stripe *s;
+	struct bch_fs *c = trans->c;
 	struct printbuf buf = PRINTBUF;
+	const struct bch_stripe *s;
+	struct gc_stripe *m;
 	unsigned i;
 	int ret = 0;
 
-	if (metadata_only)
+	if (k.k->type != KEY_TYPE_stripe)
 		return 0;
 
-	bch2_trans_init(&trans, c, 0, 0);
+	s = bkey_s_c_to_stripe(k).v;
+	m = genradix_ptr(&c->gc_stripes, k.k->p.offset);
 
-	for_each_btree_key(&trans, iter, BTREE_ID_stripes, POS_MIN,
-			   BTREE_ITER_PREFETCH, k, ret) {
-		if (k.k->type != KEY_TYPE_stripe)
-			continue;
-
-		s = bkey_s_c_to_stripe(k).v;
-		m = genradix_ptr(&c->gc_stripes, k.k->p.offset);
-
-		for (i = 0; i < s->nr_blocks; i++)
-			if (stripe_blockcount_get(s, i) != (m ? m->block_sectors[i] : 0))
-				goto inconsistent;
-		continue;
+	for (i = 0; i < s->nr_blocks; i++)
+		if (stripe_blockcount_get(s, i) != (m ? m->block_sectors[i] : 0))
+			goto inconsistent;
+	return 0;
 inconsistent:
-		if (fsck_err_on(true, c,
-				"stripe has wrong block sector count %u:\n"
-				"  %s\n"
-				"  should be %u", i,
-				(printbuf_reset(&buf),
-				 bch2_bkey_val_to_text(&buf, c, k), buf.buf),
-				m ? m->block_sectors[i] : 0)) {
-			struct bkey_i_stripe *new;
-
-			new = kmalloc(bkey_bytes(k.k), GFP_KERNEL);
-			if (!new) {
-				ret = -ENOMEM;
-				break;
-			}
+	if (fsck_err_on(true, c,
+			"stripe has wrong block sector count %u:\n"
+			"  %s\n"
+			"  should be %u", i,
+			(printbuf_reset(&buf),
+			 bch2_bkey_val_to_text(&buf, c, k), buf.buf),
+			m ? m->block_sectors[i] : 0)) {
+		struct bkey_i_stripe *new;
+
+		new = bch2_trans_kmalloc(trans, bkey_bytes(k.k));
+		ret = PTR_ERR_OR_ZERO(new);
+		if (ret)
+			return ret;
 
-			bkey_reassemble(&new->k_i, k);
+		bkey_reassemble(&new->k_i, k);
 
-			for (i = 0; i < new->v.nr_blocks; i++)
-				stripe_blockcount_set(&new->v, i, m ? m->block_sectors[i] : 0);
+		for (i = 0; i < new->v.nr_blocks; i++)
+			stripe_blockcount_set(&new->v, i, m ? m->block_sectors[i] : 0);
 
-			ret = commit_do(&trans, NULL, NULL, 0,
-				__bch2_btree_insert(&trans, BTREE_ID_reflink, &new->k_i));
-			kfree(new);
-		}
+		ret = bch2_trans_update(trans, iter, &new->k_i, 0);
 	}
 fsck_err:
-	bch2_trans_iter_exit(&trans, &iter);
+	printbuf_exit(&buf);
+	return ret;
+}
 
-	bch2_trans_exit(&trans);
+static int bch2_gc_stripes_done(struct bch_fs *c, bool metadata_only)
+{
+	struct btree_trans trans;
+	struct btree_iter iter;
+	struct bkey_s_c k;
+	int ret = 0;
 
-	printbuf_exit(&buf);
+	if (metadata_only)
+		return 0;
+
+	bch2_trans_init(&trans, c, 0, 0);
+
+	ret = for_each_btree_key_commit(&trans, iter,
+			BTREE_ID_stripes, POS_MIN,
+			BTREE_ITER_PREFETCH, k,
+			NULL, NULL, BTREE_INSERT_NOFAIL,
+		bch2_gc_write_stripes_key(&trans, &iter, k));
+
+	bch2_trans_exit(&trans);
 	return ret;
 }