bcachefs: Add the status of bucket gen gc to sysfs

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/bcachefs.h

@@ -719,6 +719,9 @@ struct bch_fs {
 	atomic_t		kick_gc;
 	unsigned long		gc_count;
 
+	enum btree_id		gc_gens_btree;
+	struct bpos		gc_gens_pos;
+
 	/*
 	 * Tracks GC's progress - everything in the range [ZERO_KEY..gc_cur_pos]
 	 * has been marked by GC.

fs/bcachefs/btree_gc.c

@@ -1193,6 +1193,8 @@ static int bch2_gc_btree_gens(struct bch_fs *c, enum btree_id btree_id)
 
 	while ((k = bch2_btree_iter_peek(iter)).k &&
 	       !(ret = bkey_err(k))) {
+		c->gc_gens_pos = iter->pos;
+
 		if (gc_btree_gens_key(c, k)) {
 			bch2_bkey_buf_reassemble(&sk, c, k);
 			bch2_extent_normalize(c, bkey_i_to_s(sk.k));
@@ -1244,6 +1246,8 @@ int bch2_gc_gens(struct bch_fs *c)
 
 	for (i = 0; i < BTREE_ID_NR; i++)
 		if ((1 << i) & BTREE_ID_HAS_PTRS) {
+			c->gc_gens_btree = i;
+			c->gc_gens_pos = POS_MIN;
 			ret = bch2_gc_btree_gens(c, i);
 			if (ret) {
 				bch_err(c, "error recalculating oldest_gen: %i", ret);
@@ -1260,6 +1264,9 @@ int bch2_gc_gens(struct bch_fs *c)
 		up_read(&ca->bucket_lock);
 	}
 
+	c->gc_gens_btree	= 0;
+	c->gc_gens_pos		= POS_MIN;
+
 	c->gc_count++;
 err:
 	up_read(&c->gc_lock);

fs/bcachefs/sysfs.c

@@ -136,6 +136,7 @@ write_attribute(trigger_btree_coalesce);
 write_attribute(trigger_gc);
 write_attribute(prune_cache);
 rw_attribute(btree_gc_periodic);
+rw_attribute(gc_gens_pos);
 
 read_attribute(uuid);
 read_attribute(minor);
@@ -312,6 +313,13 @@ static int bch2_compression_stats_to_text(struct printbuf *out, struct bch_fs *c
 	return 0;
 }
 
+void bch2_gc_gens_pos_to_text(struct printbuf *out, struct bch_fs *c)
+{
+	pr_buf(out, "%s: ", bch2_btree_ids[c->gc_gens_btree]);
+	bch2_bpos_to_text(out, c->gc_gens_pos);
+	pr_buf(out, "\n");
+}
+
 SHOW(bch2_fs)
 {
 	struct bch_fs *c = container_of(kobj, struct bch_fs, kobj);
@@ -337,6 +345,11 @@ 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;
+	}
+
 	sysfs_printf(copy_gc_enabled, "%i", c->copy_gc_enabled);
 
 	sysfs_printf(rebalance_enabled,		"%i", c->rebalance.enabled);
@@ -566,6 +579,7 @@ struct attribute *bch2_fs_internal_files[] = {
 	&sysfs_trigger_journal_flush,
 	&sysfs_trigger_btree_coalesce,
 	&sysfs_trigger_gc,
+	&sysfs_gc_gens_pos,
 	&sysfs_prune_cache,
 
 	&sysfs_copy_gc_enabled,