bcachefs: Improve path for when btree_gc needs another pass

btree_gc sometimes needs another pass when it corrects bucket generation
numbers or data types - when it finds multiple pointers of different
data types to the same bucket, it may want to keep the second one it
found.

When this happens, we now clear out bucket sector counts _without_
resetting the bucket generation/data types that we already found,
instead of resetting them to what we have in the alloc btree.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

fs/bcachefs/btree_gc.c

@@ -604,8 +604,8 @@ static int bch2_check_fix_ptrs(struct bch_fs *c, enum btree_id btree_id,
 				(bch2_bkey_val_to_text(&PBUF(buf), c, *k), buf))) {
 			if (data_type == BCH_DATA_btree) {
 				g2->_mark.data_type	= g->_mark.data_type	= data_type;
-				g2->gen_valid		= g->gen_valid		= true;
 				set_bit(BCH_FS_NEED_ALLOC_WRITE, &c->flags);
+				set_bit(BCH_FS_NEED_ANOTHER_GC, &c->flags);
 			} else {
 				do_update = true;
 			}
@@ -1327,12 +1327,6 @@ static int bch2_gc_start(struct bch_fs *c,
 
 	percpu_down_write(&c->mark_lock);
 
-	/*
-	 * indicate to stripe code that we need to allocate for the gc stripes
-	 * radix tree, too
-	 */
-	gc_pos_set(c, gc_phase(GC_PHASE_START));
-
 	for_each_member_device(ca, c, i) {
 		struct bucket_array *dst = __bucket_array(ca, 1);
 		struct bucket_array *src = __bucket_array(ca, 0);
@@ -1360,6 +1354,27 @@ static int bch2_gc_start(struct bch_fs *c,
 	return 0;
 }
 
+static void bch2_gc_alloc_reset(struct bch_fs *c, bool initial, bool metadata_only)
+{
+	struct bch_dev *ca;
+	unsigned i;
+
+	for_each_member_device(ca, c, i) {
+		struct bucket_array *buckets = __bucket_array(ca, true);
+		struct bucket *g;
+
+		for_each_bucket(g, buckets) {
+			if (metadata_only &&
+			    (g->mark.data_type == BCH_DATA_user ||
+			     g->mark.data_type == BCH_DATA_cached ||
+			     g->mark.data_type == BCH_DATA_parity))
+				continue;
+			g->_mark.dirty_sectors = 0;
+			g->_mark.cached_sectors = 0;
+		}
+	};
+}
+
 static int bch2_gc_reflink_done(struct bch_fs *c, bool initial,
 				bool metadata_only)
 {
@@ -1430,6 +1445,55 @@ static int bch2_gc_reflink_done(struct bch_fs *c, bool initial,
 	return ret;
 }
 
+static int bch2_gc_reflink_start(struct bch_fs *c, bool initial,
+				 bool metadata_only)
+{
+	struct btree_trans trans;
+	struct btree_iter iter;
+	struct bkey_s_c k;
+	struct reflink_gc *r;
+	int ret = 0;
+
+	if (metadata_only)
+		return 0;
+
+	bch2_trans_init(&trans, c, 0, 0);
+	c->reflink_gc_nr = 0;
+
+	for_each_btree_key(&trans, iter, BTREE_ID_reflink, POS_MIN,
+			   BTREE_ITER_PREFETCH, k, ret) {
+		const __le64 *refcount = bkey_refcount_c(k);
+
+		if (!refcount)
+			continue;
+
+		r = genradix_ptr_alloc(&c->reflink_gc_table, c->reflink_gc_nr++,
+				       GFP_KERNEL);
+		if (!r) {
+			ret = -ENOMEM;
+			break;
+		}
+
+		r->offset	= k.k->p.offset;
+		r->size		= k.k->size;
+		r->refcount	= 0;
+	}
+	bch2_trans_iter_exit(&trans, &iter);
+
+	bch2_trans_exit(&trans);
+	return ret;
+}
+
+static void bch2_gc_reflink_reset(struct bch_fs *c, bool initial,
+				  bool metadata_only)
+{
+	struct genradix_iter iter;
+	struct reflink_gc *r;
+
+	genradix_for_each(&c->reflink_gc_table, iter, r)
+		r->refcount = 0;
+}
+
 static int bch2_gc_stripes_done(struct bch_fs *c, bool initial,
 				bool metadata_only)
 {
@@ -1493,43 +1557,10 @@ static int bch2_gc_stripes_done(struct bch_fs *c, bool initial,
 	return ret;
 }
 
-static int bch2_gc_reflink_start(struct bch_fs *c, bool initial,
-				 bool metadata_only)
+static void bch2_gc_stripes_reset(struct bch_fs *c, bool initial,
+				bool metadata_only)
 {
-	struct btree_trans trans;
-	struct btree_iter iter;
-	struct bkey_s_c k;
-	struct reflink_gc *r;
-	int ret = 0;
-
-	if (metadata_only)
-		return 0;
-
-	bch2_trans_init(&trans, c, 0, 0);
-	c->reflink_gc_nr = 0;
-
-	for_each_btree_key(&trans, iter, BTREE_ID_reflink, POS_MIN,
-			   BTREE_ITER_PREFETCH, k, ret) {
-		const __le64 *refcount = bkey_refcount_c(k);
-
-		if (!refcount)
-			continue;
-
-		r = genradix_ptr_alloc(&c->reflink_gc_table, c->reflink_gc_nr++,
-				       GFP_KERNEL);
-		if (!r) {
-			ret = -ENOMEM;
-			break;
-		}
-
-		r->offset	= k.k->p.offset;
-		r->size		= k.k->size;
-		r->refcount	= 0;
-	}
-	bch2_trans_iter_exit(&trans, &iter);
-
-	bch2_trans_exit(&trans);
-	return ret;
+	genradix_free(&c->gc_stripes);
 }
 
 /**
@@ -1565,11 +1596,13 @@ int bch2_gc(struct bch_fs *c, bool initial, bool metadata_only)
 	/* flush interior btree updates: */
 	closure_wait_event(&c->btree_interior_update_wait,
 			   !bch2_btree_interior_updates_nr_pending(c));
-again:
+
 	ret   = bch2_gc_start(c, metadata_only) ?:
 		bch2_gc_reflink_start(c, initial, metadata_only);
 	if (ret)
 		goto out;
+again:
+	gc_pos_set(c, gc_phase(GC_PHASE_START));
 
 	bch2_mark_superblocks(c);
 
@@ -1607,25 +1640,26 @@ int bch2_gc(struct bch_fs *c, bool initial, bool metadata_only)
 
 	if (test_bit(BCH_FS_NEED_ANOTHER_GC, &c->flags) ||
 	    (!iter && bch2_test_restart_gc)) {
+		if (iter++ > 2) {
+			bch_info(c, "Unable to fix bucket gens, looping");
+			ret = -EINVAL;
+			goto out;
+		}
+
 		/*
 		 * XXX: make sure gens we fixed got saved
 		 */
-		if (iter++ <= 2) {
-			bch_info(c, "Second GC pass needed, restarting:");
-			clear_bit(BCH_FS_NEED_ANOTHER_GC, &c->flags);
-			__gc_pos_set(c, gc_phase(GC_PHASE_NOT_RUNNING));
-
-			percpu_down_write(&c->mark_lock);
-			bch2_gc_free(c);
-			percpu_up_write(&c->mark_lock);
-			/* flush fsck errors, reset counters */
-			bch2_flush_fsck_errs(c);
+		bch_info(c, "Second GC pass needed, restarting:");
+		clear_bit(BCH_FS_NEED_ANOTHER_GC, &c->flags);
+		__gc_pos_set(c, gc_phase(GC_PHASE_NOT_RUNNING));
 
-			goto again;
-		}
+		bch2_gc_stripes_reset(c, initial, metadata_only);
+		bch2_gc_alloc_reset(c, initial, metadata_only);
+		bch2_gc_reflink_reset(c, initial, metadata_only);
 
-		bch_info(c, "Unable to fix bucket gens, looping");
-		ret = -EINVAL;
+		/* flush fsck errors, reset counters */
+		bch2_flush_fsck_errs(c);
+		goto again;
 	}
 out:
 	if (!ret) {